Conference vmszoo::rc

		I recently went to the ducted fan meeting at
	Abingdon. It is a yearly event, exclusively for fan 
	driven models... There was in the region of 50 
	planes there this year, most of which were built to
	an incredibly high standard.. The crash rate did seem
	rather high. Of the ones that glew I would guesstemate
	that 50%ish were rekitted.

		Three notables were an 8ft long F-15 Eagle powered 
	by twin	KB 45s and turbax fans. Flown by a Belgian chap.                  
        A 13ft long Concorde, complete with drooping snoot, powered
	by 4 Super Tigre 45s. Looked very realistic in the air.      
        A 8ft span A10 Warthog, that dropped bombs..


		There was a good variety of models including, BAE Hawks,
	Gnats, Starfighters, F-20 Tigersharks, Saab Viggen, Mirage, Lear
	Jet, Chance Cutlass, Sabres, Migs (sabre type shape), Huge twin
	fan Mig Foxbat. Plus a 75% complete Harrier, with full VTOL
	capability, and puffer jets in the wingytips. Looked like a pile
	of plastic drainpipes to me. Aparrently several test rigs have been
	built and sucessfully flown. 

		
                Most sucessful fliers of the day had to be the Thorpe 
	brothers. They produce their own fan unit, use OPS 40 engines
	and run on straight fuel.. Their Tigershark is good for 150+
	on a 40 engine... They had at least one of their plane in the 
	air throughout the afternoon. 

		
                If I had easy access to a good runway then I would
	undoubtably build a fan model of some sort. Fans and grass
	strips don't mix to well.. We have had sucessful flights from
	our field, but it took a lot of attempts to get off.. Never
	know I may still succumb and build the Thorpe Bros Starfighter.
	Ducted fans are the business.....
     

		bob

	Does anyone have any direct experience, knowledge, seen or have 
any info on the Hi Tech 2002 featured in the Sept 86 AMA mag.  It is a 
45 sized canard wing fan jet.  Also what suitable engines (45 sized) 
are available besides the K & B 7.5 and the OS .46.  This plane is 
designed to use the RK-740 fan unit but I haven't seen it advertised in 
any of the major adds.  Any info on sources for fan jets would be 
welcome.

    The OPS .45 is frequently used in ducted fan applications.  Of interest
    to all potential "vacuum-cleaner" jockeys (and in line with Bob Day's 
    report ot the Adingdon, U.K. dusted fan meet) will be the article
    on DF activities in the U.K (by Ron Sweeny) in the latest issue
    of Scale R/C Modeler.  DF activity in the U.K. seems to be less
    than in the U.S. but they seem to be MUCH more innovative there.
    
    Adios,	Al

    re .1
    
    Hey Bob, you mentioned that a good number  of the planes at Abington
    "re-kitted" themselves.. DO you have any info  as to the major causes
    of such drastic action ??

    


    		Dunno really.. One major cause was that they don't
    	seem to dead stick to well. Several just sorta dropped out
    	of the sky. There was a twin enginge Mig Foxbat that lumbered
    	around on one engine, then made a very heavy landing.
    		The little Learjet just couldn't get up in the
    	crosswind. There just seemed to be a lot of broken planes...
    	
    
    		What were your obversations John?....
                             
    
    	bob

    ANyone got a name for the guy who did that ducted fan unit for the
    HARRIER ?? and how one could possibly get in touch with him ??
    
    md

    re .5. 
    
    I'll believe the dead stick one.. I will have to admit that I'm
    a bit suprised/dismayed at that. 
    
    It would seem to me that the first thing to ensure is that the engine
    is reliable. Now, are the engine cutting out more often than their
    prop driven brothers or what ??
    
    md

    Marc,
    
    I'm not a jet jockey and am not likely to be'til they can demonstrate
    better handling and friendlier qualities than they do now.  I can,
    however, give you some reasons why they're less reliable than their
    propellor turning kin.
    
    The very environment the ducted fan engine is required to function
    is at the root of the reliability issue: consider, for starters,
    that you cannot treat a DF engine with moderation like we do our
    prop engines...you dare NOT give 'em a break and run 'em rich as
    they MUST put out the absolute MAXIMUM possible RPM (power).  With
    a .40-.60 engine, we expect to run between 10-to-14 thousand RPM
    and can easily tolerate 1000 R's less to keep the engine a little
    on the rich side with no great loss of performance.
    
    The same (or similar) engine in a DF set-up MUST turn upwards of
    24,000 RPM and the loss of 1000 R's makes the difference between
    flying and NOT flying...all the DF's power is generated at the UPPER
    limits of it's RPM capability.  Add to this the fact that many DF
    engines are burning upwards of 40% nitro, are totally enclosed within
    the fuselage, and are being fed from non-conventionally located saddle-
    tanks, frequently requiring (UGH!) pumps to feed a header, tank and
    you have all the ingredients for a VERRRY finicky power package...
    requiring a lot more tweaking and fiddling than I'm prepared to
    do.  I wanna' fuel-up. fire-up 'n fly when I go to the field, not
    spend the day "playing engine" in the pits...particularly when one
    sour run can cost you the whole ball-of-wax!
    
    I have no idea why an engine failure should, of necessity, precipitate
    a crash, unless, of course, the failure catches you at a critical
    moment during takeoff/climb-out.  A jet is, after all, just an airplane
    (a very light one at that) and "should" be perfectly capable of
    landing dead-stick just like any other model.  Obviously, they are
    of more exotic planform and design so they probably don't possess
    the glide ratio of an Eaglet...my suspicion is that a pilot, too
    often, forgets this and tries to get too much "stretch" out of it
    resulting in the well known snap/spin/crash syndrome.
    
    If a guy just has to try his jet-wings, I'd strongly recommend he
    start with a Byron F-16.  The Byro-jet set-up seems much less exotic,
    therefore more trouble-free (pronounced: reliable), doesn't demand
    high-nitro fuels and seems a little more tolerant of less than peak
    RPM runs.  The F-16, while looking EXTREMELY slippery, is probably
    one of the friendliest birds I've ever seen, fan or prop!  It can
    be flown at VERRRY low speeds, nose-high and landed at nearly walking
    speed with no snap tendencies...in fact, it seems almost stall-proof!
    It'd certainly be my first choice if I was ever bitten by the jet-bug.
    
    Adios,	Al

    Just wanted to add my comments regarding Ducted Fans.  A fellow
    at our field is flying various DF planes.  Of these, one stands
    out as being "user friendly".  It is a Bob Parkinson "Regal Eagle"
    F-15.  It is realistic in its flight characteristics (I know because
    McDonnell Douglas is my customer).  The most significant thing about
    this plane is that fact that "It is stall proof".  Emmett, the owner
    could not stall it even intentionally.  He dropped it to an idle
    and gave it full up elevator.  The result was it raised the nose
    a little and maintained its previous course.  This guy can fly and
    he tryed everything in the book to get it to stall and couldn't
    do it.  Result: several people have ordered them.  I am still learning
    on a trainer, but need I say more?
    
    Bye,
    Chris

I think Al covered everything in .8 however I will add a couple of
observations. 

At Abingdon I thought the main reason for the model fatalities were Pilot
error. Most instances the pilots kept applying up elevator to gain altitude
when there was insufficient air speed, not only was the wing stalled but
generally the the fan as well. Remember you can stall a prop or a fan and end
up with a disk of air rotating performing no useful work. Bob, you remember the
Concord, that had very marginal power but the pilot let it build up speed in
straight level flight before gaining altitude. 

The second point is that as a general rule Ducted Fan and Scale builders alike
do not spend enough time considering the needs of the engine during the
construction of the models. To them the engine is a necessary evil to propel
the model around the sky and put of the inevitable necessary testing until
they reach the flight line at a flying field. (eg. I put five tanks of fuel
through it on the bench and had no problems; all I have done since is install
it in the model, invert it, put a different fuel tank in a different place, put
a cowl around the engine, change fuel etc and now it won't run.) 

Stu Richmond the well known Journalist made the statement that "we should have 
Scale modellers building the models, Pylon fliers setting up the engines and 
maintaining the aircraft, and pattern fliers presenting them at contests; it 
would be an unbeatable team."

John

    
    	re -.2  From what I read in this months Model Avaition mag
    	about similtars what you said about the inability of the
    	owner/flier of the F-15 to stall it makes a lot of sense
    	since the F-15 is a flying wing. Was a good article and
    	people should read it.
    
    				Mike
    

    Engines a necessary evil ?? Not unless your a glider flier !!!
    
    For my money, If your are going to put a power plant in your favorite
    toy, you better pay attention to its performance. If you don't and
    get into trouble, you asked for it..
    
    And if you are going to go DF, learning about the differences from
    standard propeller driven beasts is a must.. otherwise more trouble..
    
    md

    I did a bit of thinking after Al's comment and other remarks on
    engine power in other notes. 
    
    SOunds to me that is one going to spin a engine in the 20-25000
    rpm range for a DF, one better be ready to spend some $$$$ on a
    good quality engine, probably of the type used in racing (pylon
    or other). In addition, it is probably a good idea to find a
    local engine guru to help you get the best power out of it.
    
    Also, as mentioned, get the biggest thing that will fit.
    
    (I can't help thinking about some comment I read way back about
    how expensive (per hour) it was to operate a jet as compared to
    a regular prop engine.. I guess the same seems to applies to models)
    
    Now does anyone have brands/size of engines that would meet the
    above. Rossi & Supertigre are two that come to my mind. 
    
    md

    Marc,
    
    Now yer' thinkin' in the right ballpark.  However, those engines
    which have been designed and built for DF application (K&B 7.5 &
    .72, O.S. .77, Rossi .81, etc.) have "supposedly" been optimized 
    in the areas you mention and are, as such, already "hopped-up" 
    racing engines.
    
    Adios,	Al

	Ah come on guys, hows about some more activity on Ducted Fans.  
So far most replies have been from those without direct DF experience.  
Lets hear from someone who has built or flown one of these birds!

	How about more engine info, Do's and Don'ts.  Anyone have 
experience with Irvine engines?  I understand they make a RE 40 that 
could be used for DF.  Any comments?

	I am going to build some kind of fan jet this winter, but I don't 
want to spend BIG$$$, so I think I'l go the 45 sized route and maybe 
scratch build something.

	I found this list of manufactures of DF related products in the 
Sept issue of MA News.

	Sterner Engineering
	661 Moorestown Dr	
	Battle, Pa.

	Cressline Model Products
	635 Third Ave S.
	Park WI 54552

	Bob Violett Models
	1373 Citrus Rd.
	Winter Spring, FL 32708

	Byron Originals, Inc.
	PO Box 279
	Ida Grove, IA 51445

	Force Air Technology, Inc.
	9275 Trade Place, Suite G
	San Diego, CA 92126

	Bob Parkinson Flying Models
	3 William St.
	Thornton, Ontario 2NO
	Canada

	Jet Hanger Hobbies
	12554 Centralia Rd.
	Lakewood, CA 90715

	Century Models
	11B Senior Officer Row
	Rantoul, IL 61866

	Hurricane Fans
	Steve Korney
	14835 Halcourt Ave.
	Norwalk, CA 90650


					Tom

    COuld you give some details on what these  suppliers can provide ie
    kits or components or what ??

Some ramblings:
    
    
    Being a new Ducted Fan owner (F16), there appears to be varying reports
of just how difficult or easy it is to takeoff grass or paved runways.
The one thing I've noticed in photos of some Byron's F16's, is a real
nose high condition, attributed to the long nose gear.  I've looked at
photos, and in person of the real thing, and don't see similar attitudes
while resting on the ground.  Here is some ramblings that might stimulate
some thought....(been a long time since using this stuff, hope to have
not induced errors!)

Speculating that more thrust is diverted 'into' the ground versus 
straight back from the aircraft, I wanted to see the effect of this
on takeoff distance, hence runway.  Ideal conditions are assumed here,
no friction, drag, etc, but for figures quoted by Byron's of takeoff
distances of 100 to 150 feet, these calculations are close to ballpark.

The point is, a prop driven plane gets lift from the propwash, a jet
only gets lift due to air velocity over the wing by moving forward.
The less thrust you have in the forward direction, the longer it will
take to get to takeoff velocity.            
             
             
      Assumes: ByroJet, 12 pounds thrust
          _  
          A   force
        <-----vector along desired direction of movement (this gives forward                
           _                                               velocity).
           C  force                                        
	vector along thrust axis out of byrojet nose high (12 pounds max)
              /
 	     /                                                                 
        |   /
        |  /\  
        | /  \<-----angle of nose Q (30 degrees)        Desired           
        |V____\_________________________________>Direction of movement
             _    _              
            |A|= |C|*cos(Q)        
          10.4 = 12 * cos(30) where 30 is 30 degrees based on photos

This means 10.4 pounds of thrust is directed along axis of desired movement,
which is only 86% of available thrust! (What a waste!)


Some dynamics:


	      ===========================
		Velocity, Vf = Vo + a*t

		Distance,  S = .5*a*t^2

		Force,	   F = m*a

		Acceleration, a

		Time in Seconds, t

		Mass, m

		Vo, initial velocity

		Vf, final velocity
	     ============================
		
	Facts:   Thrust of Engine = 12 pounds
		 Weight of Plane  =  8 pounds
		 Angle  of Thrust/direction  = 330 degrees (360-330=30 below)  
		 Acceleration of Gravity = 32 ft/sec^2


	Assumptions: No Friction or Drag (what factor to use here?)
		     (Might be close for paved runway)
		
		     Takeoff velocity is 60 MPH  (It may be more, or less)
		
	
	Using:  F=ma, we get 8# = m*32ft/sec^2
			     m	= 8/32=.25 (mass of airplane)

	Using:  Vector relationships, 12 * cos ((30*3.141592654/180))=x compt.
						for cos in radians.

				  gives 10.4 # is thrust along x axis (ground).

	Using:  F=ma, we get acceleration along x axis (ground):

			10.4 = .25 * a
			   a = 41.6 ft/sec^2

	If takeoff velocity is 60mph, or 88 ft/sec, then:

		
		Velocity, Vf = Vo + a*t

			  88 =  0 + 41.6 * t

			   t = 2.1 seconds

	Runway distance:

		Distance,  S = .5*a*t^2

			   S = .5 * 41.6 * 2.1^2
			
			   S = 91.7 feet			

	  Byron's say 100 to 150 feet, (real life conditions.)

    neat... love it...
    
    My questin now is: Is your F16 in a nose high attitude on the ground?
    If so, did you consider adjusting the landing gear to have the plane
    closer to zeror degrees..
    
    Historical note: The ME262 was originally designed to be a taildragger.
    
    The 1st proto was prop driven (1 engine in nose, stolen from ME109).
    this was to test airframe, whil ewaiting for  engines.
    The jet engines where then installed (in addition to prop)..
    it was found that the plan would not take lift its tail 'cause
    tail plane was blanketed..
    
    The temporary fix was to mark the runway with a white line and
    when line was reached, apply brake to lift tail...
    
    Enventually the landing gear was modified to use nose wheel
    
    even at that, the ME262 still required about 1000m to take off..
    
    md

    I modified my landing gear to approximate the real thing...
    I reviewed an old review of the F16 in Model Airplane News, and
    their photos are significantly nose-high (Sept '81 I believe). 
    Since the nose gear is two piece (solder axle portion to main strut),
    I cut the main strut to achieve this.

    RE .20 - Have you flown your F16 yet?  I have seen the Byron F16
    fly from a grass field (CMRCM in Westboro) with some difficulty
    getting it airborne.  Drag on the gear can make it difficult to
    rotate resulting in running off of the runway.  I suspect this may
    be the reason some are set up to taxi nose high.  Otherwise, the
    elevator must be able to lift the nose.  If the CG is too far forward,
    it can be difficult to rotate, especially on a grass field even
    after sufficient speed for takeoff is attained.  By the way, the
    only way the guy I saw flying it could get it off successfully was
    to have a partner hold it at the end of the runway while he ran
    the engine up to full thrust before releasing it.  He also experienced
    a near disaster when the fan came loose on the engine shaft during
    flight.  The vibration was so severe that it caused the throttle
    to score the bore resulting in a stuck at full throttle condition.
    Then things started falling off of the plane.  He lucked out and
    ran out of fuel before the plane disintigrated completely and
    deadsticked it in.  Plastic parts were welded from the vibration
    and all of the servo gears were trashed.  The engine mount was
    cracked as well.  I think that the total repair bill was about $150.
    

    
    	In ref to .16, corrected address for Sterner Engineering
    
    	Sterner Engineering
    	661 Moorestown Dr.
    	Bath, Pa. 18014
    	
    	Additional Suppliers
    
    	Kress Jets, Inc.
    	4308 Ulster Landing Rd.
    	Saugerties, NY 12477
    
    	Tidewater Engr & Mach Co.
    	PO Box 1135
    	Bastrop, LA 71220
    
    	B- Line Products
    	PO Box 1231 
    	823 Main St.
    	Roseville, CA 95661
    
    	REF .17 -----  The suppliers listed sell engines, fan units,
    kits and accessories for the ducted fan user.  I have written for
    info from all of those listed.  If there is interest I will post
    items, description, price and mfg from those who respond.

    I would like get all the info you can get you hands on.
    
    If you can sen me hard copy, that would even better.
    
    BTW, I'm looking for a fan unit that can generate up 10 pounds of
    thrust. External dimension should not exceed 4 inches in diameter
    
    tx,
    
    md
    
    

    
    	The info is starting to arrive.   I would be happy to hard copy
    any one who is interested.  Just vaxmail me your address.
    
    	I am at marhub::mjovax::sprecher

    Seen in Model Aviation, nov issue, product review column:
    
    Bob Violett (See .16 for address) now has an engine for is Viojett
    Fan system. Was design in conjunction with John Brodbeck of K&B.
    
    Its a rear intake, read exhaust .72. Come fitted with addjustable
    exhaust header for pipe. Supposed to be better than the imports
    
    $240. qty 1... (oouch)
    
    md

    Marc,
    
    Does the price include the Viojett fan unit or is that $240.00 for
    the engine alone?....if so, I second yer' "Ouch!"  U.S. manufacturers
    simply MUST become price-competitive with the imports!  They (the
    mfgr.'s) can't expect us to pay a premium to buy/fly American, es-
    pecially when their engines frequently fall short of the performance
    of their foreign competition.
    
    The hottest fan engine I've seen of late is the new O.S. .77.  Several
    of the jet-jockeys, hereabouts, have replaced their Rossi .81's
    with this engine and realized better takeoff acceleration and no-
    ticeably increased top speed.  One guy's Byron F-16 gained enough
    top speed to experience a tail-section flutter he'd NEVER had before.
            
    Adios,	Al
                  

    RE -.26,
    
    	Byron's specifies how to balance the flying stabilizer...this
    may help dampen the perceived flutter.  Also, the stab is controlled
    via Nyrods, and will need several supports inside the fuse...
    
    			-Mike
    

	Our ducted fan man brought his A10/Warthog/Tankbuster up
	the field this weekend.  He couldn't fly it cos it doesn't
	actually have all the radio installed. he just wanted to
	run the engines up, check the fuel pump and silencer...
	It's powered by 2 OPS 40s driving Micromold fan units. 
	An electric fuel pump keeps the fuel flow up, and the 
	engines both exhaust via a common silencer. No where to
	put tuned pipes.....

	There's lots of other goodies built in. The retracts operate
	via motor driven screw, so they wind up and down slowly. Ther's
	an electric canopy lift (real posey). It has a full range of
	bombs under the wings, which can be dropped in flight, all good
	fun....

	Not sure what the scale is, or the wingspan, somewhere in the 
	6-8 ft region I guess, must ask him...... Very impressive piece
	of building....

	One of these was flown at Abingdon last june.. Looks great in the
	air. Flys a lot slower than normal ducted fan planes. Plus the
	sound of twin screaming engines was great. Nearly as good as a 4
	stroke....

	cheers

	bob 

    Ok, I called up Bob Violett Models to get more info on the $240
    wonder..
    
     Well, it appears to be a case of getting what you pay for.
     
    Yup, the price is higher than your ROSSIs, PICCOs or OS MAX
    but when you by the latter, you usually have to go out & buy a number of
    "adapter parts" from the fan mfgr in orderto mate the engine to
    the fan unit. Same applies if you plan to buy a pipe (almost
    mandatory in this business). All this stuff is going to set you
    back about $100 extra.  Also to consider is the price of
    replacement parts.
     As far as the KBV goes, you buy the engine & slap it into the 
    VIOJETT unit and that's it. You want a pipe, same thing, buy it
    and ad it on. The exhaust header is already designed to accept
    a pipe. 
    
    The fan, BTW, is something else. A lot of engineering has gone into
    to this sucker to make the airflow as smooth as possible. There
    is a fairing in front of the engine cylinder (it also doubles up
    as a stator. There is an other fairing aft of the cylinder to
    reduce turbulence generated by the cylinder. There is an other
    fairing (cone shaped) that extends from the engin mount back to
    further aid air flow.
    
    Generates some 10 lbs of real thrust. All this in a package
    some 5" diameter. Length depends on specific model and is
    not critical.
    
    OK, about prices:
    
    	engine :	$240
    	Fan    :	$210
        Pipe   :	$ 52
    
    You may also want a probe to attach to you starter: $35
    
    So you just had a heart attack !!! So did I..
    
    To quote Bob Violett: If price is a consideration, don't get
    into this game. Jets are expensive ........  
    
    
    Md

>    OK, about prices:
>    
>    	engine :	$240
>    	Fan    :	$210
>        Pipe   :	$ 52
>    
>    You may also want a probe to attach to you starter: $35
>    
>    So you just had a heart attack !!! So did I..


  The Tower Hobbies 'Tower Talk' catalog that I have here show the 
OS .77 VR-DF ABC RC Ducted Fan Engine s/Heatsink as retailing for 
$359.95, but Tower sells it for only $209.99!  $240 doesn't sound
that outrageous compared to this.......
                          [ assuming the engine is any good |-)  ]


Jim

    and you are going to need a shaft adapter for the fan unit and a
    header adpater for the pipe.  If you want to preserve air stream
    smoothness (with VIOJETT) you aslo need a new head. 
    All that for about some $125.
    
    Engine part for OS 77 are apparently very expensive: $100 for cylinder
    sleeve. KBV sleeves goes for $45.
    
    md

	I am in the process of building a ducted fan from plans for a kinda-
scale Eagle.  I have all the wood, engine, fan, and pipe.  The next thing I
need is an outlet tube.  Any ideas out there on how to make one rather than
spending 50 bucks for one made of fiberglass?  I would think one could be built
from some type of heavy card stock and then fuel proofed.  The tube does not
function as any type of structural support.  Any inputs????
				
						Tom from PA

    I have seen it done using 1/64th plywood and the fiberglassed inside
    with .6 oz glass cloth.
    
    					Tom

    Also, if you have a local source for fiberglass sheet [like that
    used for circuit boards, etc.], you can buy a suitable sized sheet
    of verrrrry thin G-10 fiberglass and roll it into the desired size
    tube.  No fuel-proofing required with this method.material.
    
    Adios,	Al

    I was told by Bob Violett that the outlet tube or its length is
    not to critical. As log as it is the right size & fuel proofed,
    you should be set.
    
    
    md

	So the RC notesfile is still here...

	Over here the duct is most commonly made from litho plate.
	The thin aliminium sheet printers use... Dunno what they
	use it for as I'm not a printer... Any way it's very thin,
	light and easily formed into a duct, being ali sheet it's
	surface is very smooth. Best of all printers throw it away,
	so it costs bugger all... 

	Alternatively use 1/64 ply.....

	cheers

	bob

Gidday Bob,

So you are still around, I was beginning to think you may have been cut
into little pieces by one of your helicopters.

You may be amused to learn I have just beginning to put together a Ducted Fan 
F28. I bought a Byron OS77 fan unit this week which has still to be worked up 
to max output. I give an update once I am happy with the performance and give 
before and after figure's.

I am using a Byron Kit but modifying it to look like the Avon Saber which is an 
Australian built variant using the Avon jet but it has a very large hole up 
front which I felt would improve performance.

I am building it for the Bicentennial Airshow which modeling has a major 
involvement. It is going to be an Airshow type model rather than F4C ie. Stand 
way off scale.

Any body out in notes land built the F28?.

John

    Is there ANY ducted fan kit that you fellows would recommend as a
    a trainer?  I know you recommend against the Byron F-16.            
    
    (yeah, the V-1 Buzz Bomb.  It flies a while, then crashes and explodes.
     Landing gear is unnecessary, and not to scale, either.  Prototype
     landings are easy; fly till the fuel runs out, then put in full
     left and down stick.  Yowza!  :-)  :-)  :-)  )
                                                           
    
    Exposed propellers still give me the heebeejeebees at times.  I
    like the concept of keeping the rotating parts inside, so a bad
    landing can't crack the prop and cause a hazard later.  Besides,
    ducted fans LOOK much nicer to me.  
    
    (OK, so I used to do turbine blades for GE.  So shoot me!  That
    new UDF turbofan engine (UnDuctedFan) gives me the heebeejeebies too!
    When _that_ mutha throws a blade the pilot's going to have a real
    fun time on his hands) 

    Re: .-1,
    
    Are you talking about a trainer for getting started in jets or a
    basic trainer, period?  
    
    If yer' talking brand new, novice to R/C basic trainer, it is my opinion
    that there is NO SUCH THING as a ducted fan trainer.  Jets should
    be considered a higher level of R/C modeling which requires considerable
    prerequisite training with conventional, prop-driven trainers,
    advancing through higher performance sport types and pattern types
    PRIOR TO endeavoring into DF jets.  In other words, you must "pay
    your dues" with conventional types before trying jets if you hope
    to be successful.
    
    As an entry level, first _jet_, the Byron F-16 would be difficult
    to beat but it'd be a disaster as a first [any kind of] airplane!  

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

    
    	At one time (don't know who) someone was going to do a U-2
    ducted fan kit.  Byrons, Jet-Hangar, don't know...  But anything
    that looks like a sailplane with an engine that doesn't weigh too
    much should be an attractive first ducted fan, no?
    
    	Anybody know what happened to the U-2?

    The Russians still have the pieces to F. Gary Powers' U-2.
    
    The Air force still flies a few.  The rest of them have been
    transferred to NASA for use as ultra-high-altitude research planes.
                                   
    I wouldn't WANT to fly a U-2 as a trainer. A model probably flies a lot
    like the full-scale prototype, least they do whenever I build them.
    She's a very twitchy ship, by all reports I've read.  Twitchy not in
    that she can pull a lot of G's if you sneeze, twitchy in that you can
    easily get into a stall condition _without_ pulling a lot of G's, the
    wings tend to bend, flutter, rip off and fold up, and in general it
    ruins your day. They tried using the U-2 as a hurricane-penetration
    craft and lost several. 
             
    How much of that is due to trying to build it light, and how much
    is due to the long, narrow, tapered (i.e. twisty, vortex-shedding)
    wing, with a large roll moment (the fuel tanks were out in the wings,
    making them rather heavy, and also making the U-2 very slow to roll).
    I don't know really.  The people who really do know probably are
    not willing to talk.
    
    --------------
    
    The buzz-bomb idea was only half-facieous; remember that the V-1
    (except for a single testing proto) had no human at the controls.
    The autopilot was about as simple as could be made (as it was
    expendable).  Clock to determine flight radius, magnetic compass
    and photoelectric cell to rudder, throttle by barometric altimeter,
    elevator by airspeed, damped pendulum for ailerons (wing-leveling
    only, no coordinated turns. ) 
    
    With an autopilot that simple, the V-1 must have been a very stable
    plane.    
    
    -----------------------------
    
    Does a DF ship _have_ to be a high-performance 250-MPH
    climb-straight-up screamer?  Or is it just that everyone builds them
    that way?  As I said, exposed propellers make me nervous, especially
    those turned by .35 or bigger engines, capable of slicing off several
    fingers with no more compunction than Jason and his Cuisinart. 
                                      
    I guess the theoretical question is:
    	
    	Can a DF ship EVER be a first-plane trainer?
    
    -Bill

    
    I'll throw my $.02 in and back up Al's statement that going DF as
    a first plane is a big mistake.  I don't have any numbers for you
    but if you look at thrust-to-weight ratio of a DF versus prop I
    think you'll find a big difference (for just the power plant itself).
    This results in generally high wing loadings and hot planes.

    Also, DF doesn't have some other features I would recommend in a trainer,
    such as quick response to pull out of emergencies, easy building,
    easy starting and low maintenance.  The DF engines have to push
    25 to 30K RPMs while the prop engines operate around 15K max.  And
    cost is significantly higher.  The fan unit plus engine, plus the
    REQUIRED electric starter and battery, make for some pretty high
    start-up costs!
    
    Part of the problem may be that the industry knows most people don't
    get into DF until their skills are advanced, and therefore even
    the so-called DF trainers are pretty hot.  I have seen some fairly
    mild DF planes fly, and none was close to being considered a trainer.
    I personally get more nervous going near a DF screaming at 30K rpms
    than a prop spinning at 12K.  Either one'll do plenty of damage if
    you don't show 'em proper respect.
    
    You should try to find some people with DF planes, ask around at
    some local clubs.  Then you can go and see for yourself.  I'm
    pretty sure you'll see what we're talking about.  Of course if you
    do find a real DF trainer somewhere let us know about it!
    
    Good luck,
    
    Bill

    If any of you are still interested in the U-2 ducted fan, I've
    just run across an AD for it in the Jan. 86 issue of MAN. The
    Details:
    
    	U-2 Spyplane, 1/12 scale.
    	103" wingspan, 52" length, 8 lbs.
    	Engine: .46 to .65
    	"Recommended as the perfect ducted fan trainer."
    	$289 (in Jan. 86)
    
    	Kights of the Air
    	(301)-489-5050
    	1400 Rte 32 West Friendship, MD 21794
    
    The key comment may be that it is a ducted fan trainer rather than
    a trainer in general.  If you decide to try this U-2 let us know
    how well it works, it looks like a great plane from the photo in
    the AD.
    
      Sam
    

	Hya John.... Still managing to keep the heli at arm's 
	length...

	I'm VERY tempted to build a fan, but realistically our
	field just isn't smooth enough to get a decent take off
	run..... Occasionally you get lucky, but if I wanted to 
	play on the ground a Tamiya buggy'd be a lot cheaper. 
	
	One of these days I'm sure I'll succombe...

	There are a few in the club, an F20, several Hawks, an
	A10, a Sabre. Under construction an A4 Skyhawk, a couple
	of F18s and a Phantom.
                       
	The Sabre is the Jet hanger version, and hasn't quite made
	it into the air yet... We've been trying for several weeks
	to get it up, but as with all new plane there have been 
	teething problems, and with fans things have to be spot on.

	It'll be interesting to see how much extra thrust you can get 
	by tuning... These fans are so inefficient anyway that I would 
	think a lot of your effort would be wasted.. Better to 
	concentrate on improving the airflow, a la viojett.


	cheers

	bob
	

    It seems to me that the reason that none of the DF kits out there
    qualifies as a Primary Trainer is that they are all Scale or Sort
    of Scale Jets, mostly fighters.  I scale Jet Fighter is not going
    to be a docile, easy to land plane.  I don't see why someone couldn't
    build a DF trainer that looks more like a prop trainer, but I wouldn't
    expect to see one.  The main advantage to DF's as I see it is for
    more realistic Scale Jets.  It just doesn't look right to see a
    jet model with a prop hanging out of it.  
    	It is true that a prop (or a fan) demands respect and your
    undivided attention at all times.  If you learn the proper safety
    techniques and have the sense to ALWAYS follow them, you can avoid
    much of the risk of injury.
    
    CHarlie
    

    I saw an article recently (RCM or the ACM pub) about ducted fan
    models. Somoene has a designed a trainer for DF. I also saw a couple
    of plans for DF powered flying wings. let me look fish around.
    
    md

    
    	Widwest used to sell a kit of a .30 sized kit. I think it was
    called a "Jetster". What it consisted of was a low winged ship
    with the engine mounted on the top of the fuse in a pod configuration.
    I would think that any .40 sized low winged trainer could be modified
    in a similar manor.
    
    						Tom

    So now we believe that all (most?) DFs available are hot planes,
    because the big use of DF's is on scale jets, and a scale jet is
    going to handle about like the full-scale jet; Very Hot, Very Quick,
    Very Twitchy, and in inept hands, Very Small Pieces.
    	
    But not all full-scale jets are fighters.  Example: the V-1. (see
    previous diatribe)  
    
    Another example: the A-10 Warthog, stable under wildly varying loads
    (like the recoil when it fires that huge antitank automatic cannon with
    the HVAP depleted-uranium slugs), unspinnable, able to fly with major
    pieces missing/disabled/fluttering/jammed. Fuselage and wing are
    simple, untapered. Also ugly as sin so you don't really feel bad about
    smashing it to pieces. 
                                                     
    Too bad the A-10 is dual-engined...
                                         
    ----------------------
    
    I'm greatly surprised to hear that someone actually calls a U-2 a "good
    trainer".  Maybe it's a lot stiffer and stronger than the full-scale
    ship.  Hopefully it is....  and they must have redone the landing gear,
    as the original U-2 gear was pretty wimpy (on takeoff, there were
    wingtip wheels on struts that were jettisoned after clearing the
    runway)                      
    
    ----------------------
            
    Has anyone dealt with a DF that wasn't a scale fighter?
    
    ----------------------
    
    Please do let me know if you find out something on a primary trainer
    that's a DF.
    	
    	Thanks
    	Bill
    

    
    Bill, I missed it before but do you want a DF trainer? IE your first
    DF or do you want your first RC project to be a DF. If you have
    ne previous expereince in RC and wish to do so with a DF then I
    say
    good luck. 
    
    If you already know how to fly RC and are looking for that first
    DF ship then again any .40 sized ship could be modified to be powered
    by a DF.
                                             _______
                 -------------              /   |    |
                |             |            /    |    |
                |             |           /     |    |
      -------------------------------------==============
    /                                           |    |
    \___________________________________________|____|
        |                 |
        o                 |
        |                 |
       OOO               OOO
    
    
    
    					Tom

    re .-1, .-3
    
    That looks an awfull lot like what I ran across. 
    
    md

    I guess clarifications are in order:
    
    I want a first RC plane that's ducted fan, because I'm paranoid about
    large  (> .049) engines with exposed propellers.  I've been grazed
    several times by .049's, and I don't relish anything larger. A cousin
    (who got me into CL) got bitten rather badly by a McCoy .35; broken
    fingers, I think.  Looked very painful.  All healed now.  Guess I'm a
    bit gun-shy. 
        
    I do NOT know how to fly RC. (OK, I have maybe 10 minutes stick time
    on a friends .40 ship, several years ago)
    
    I have many hours of control line flying (mostly .049 time, on a
    skiplane of my own design.  It was ugly, but it rarely broke the
    prop, even on wet-grass landings).                 
                
    I do know car RC pretty well.  I'm reasonably competitive (not
    wonderful) with a mostly-stock SuperShot.  Left-right confusion is
    a thing of the ancient past.  Wheel time- many many hours. 
    	
    The "extra expense" of electric starter isn't a problem; the
    aforementioned cousin got his while starting with a "chicken stick",
    so I don't trust _those_ any more, either.  I have a
    spare Sears DieHard for the fieldbox. 
                                      
    (how did the Colonel manage to get his fingers into a DF anyway?)

    Bill,
    
    I'm afraid I don't know the details of Col. Thacker's accident...,
    never thought to ask him.  All I know is he was working around the
    fan with the engine running and somehow(?) got his fingers (4 of
    em) into the turbine blades.
    
    Since the fan was installed in aa model (as opposed to being test
    run on the bench) and since the nature of the injury was primarily 
    the near-surgidal removal of the pads of his fingers, I have to
    surmise he was reaching from behind into the engine compartment
    ahead of the fan unit whereby his palm was facing aft.  More than
    that I can only guess.
    
    Regarding your paranoia about props, I can only offer that there
    are risks in nearly any endeavor you can name;  you could get tangled
    up in your blankets in your sleep and suffocate while safely(?)
    suggled in your own bed.  I've built and flown gas engine powered
    models since the very early 50's and, yes, I've been bitten on occasion
    but I still have all my fingers and no scars to show for these many
    years of model flying.
    
    A very healthy respect for our engines/props is a powerful preventative
    but allowing an almost irrational fear of them to prohibit your
    enjoyment of the hobby is quite unreasonable.  The knowledge that
    you could be killed, maimed or horribly disfigured in an accident
    doesn't prevent you from driving a car, does it?  More likely, this
    knowledge influences you to take a defensive/preventative approach
    to driving.  Apply the same approach to modeling and you have it
    made.  Use an electric starter and treat the engine/prop with utmost
    respect anytime it's in motion and you'll do just fine.
    
    Please believe me when I say that there is no such animal as a DF
    powered basic trainer.  Owing to the nature of DF's, I highly doubt
    there even _could_ be such a thing and, if there were, it'd be
    _extremely_ fiddly to operate not to mention being prohibitively
    expensive for application as a trainer...totally impractical, which
    is precisely why you don't see such a thing on the market.   
    
    Take my advice, go with a conventionally powered trainer, approach
    it with all due caution and respect and ENJOY yer'self!  Otherwise,
    you'll probably never get airborne and are cheating yer'self of
    the rewards this hobby offers.  About the only other option is to 
    simply stick with sailplanes.

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

                This point  may have been made before, but I believe it's
        the single most  important  reason  why DFs don't make good first
        trainers.
        
                On a regular ship  the  prop blast flows over all control
        surfaces.  If you are close to a stall and gun the engine you get
        immediate lift and all controls will  "bite"  in  the slipstream.
        When I train beginners the most common  mistake  is  to  give too
        much up elevator and end up hanging on the prop.  On a ducted fan
        you don't have this effect.  No matter how  much  power you apply
        it doesn't help one little bit on you controls.   Not  until  you
        have gained sufficient air speed will you regain full control.

                      _ 
                     / |
        |  _====____/==|
        |-/____________|
        |    |        o \
             O           \ 
                          O
         Hang in there! o_|_
                          |
             Anker      \_|_/

>        the single most  important  reason  why DFs don't make good first
>        trainers.

Agreed but also I don't know where your located.
Ducted fans need lots of very smooth runway.

If your in Mass then you're probably out of luck unless
you can get the Duke to give you a large nice piece of
Interstate 495.  If you have a field large enough to take off in
then double it or triple it for landing.

That is not to say that there are no ducted fans in Mass.
There are no ducted fans that have ever successfully been
flown in Mass by a novice.  Can anyone prove me wrong?

              _!_      
Bye        ----O----   
Kay R. Fisher / \     

================================================================================

    As a novice who graduated to RC last year from U/C & .049s, I would
    recommend you get yourself a good prop driven trainer. Its no secret
    that I want to go DF also, but I going to get my wings first. I
    built a .20 powered trainer last year (and lost it). Now working
    on a .40 powered Goldberg CUB. Ya, me to, i was scared about about
    get my fingers chopped but found these bigger engines easier to
    deal wit than the .049s.
    
    As far as finger in the prop concern, I say: get yourself a starter.
    They are great. They come new at around $40. Check RC_SWAP also.
    Bargain show up on a regular basis.  They start an engine in a jiffy
    and take all the pain out of getting in air.
    
    
    DF engines are going to be more difficult to deal with than regular
    sports class engines. These mills are really like speed class ones.
    They run at 25K to 30K rpm, need a pipe, etc,. They also cost a 
    bundle more. COme to think about it, by the time you add up all
    the expenses for DF, you'll probably find that you could have bought
    2 regular prop-driven planes.
    
    You may also want to consider a glider or a electric-powered plane.
    That way, you won't have to worry about the big engine with the
    big prop. And you get to fly R/C !!!!
    
    have fun,
    
    md

    re .-2;
    	
    	Quite right on the fanwash/control surface; the V-1 had a
    rudder-plate that extended into the jetwash.
    	
    The A-10 Warthog "cages" the jet exhaust over the top of the elevator
    and on the inside surfaces of the twin rudders for a similar effect.
    	             
    (wash-induced control accentuation is not the only reason the A-10
    does this; the other reason is that the elevator/rudder surfaces
    thereby keep the hot (IR-visible) end of the engines from being
    visible to a ground-launched heat-seeker missle like a Stinger.)
                         
    I think (not sure, have to ask Janos sometime) that some recent
    MiGs have control surfaces in the exhaust wash, too.
    
    ------------------
    
    Why does a DF need a long, hard, smooth runway?  Is that merely
    a consequence of the high wing loading (because they're usually
    fighters?) or because of something else, like a wrong-shaped 
    thrust vs. velocity curve?  
                                          
    Or because DF models are fighters, fighters have small wheels,
    small wheels need hard surfaces?
    	
    Or because DF models are usually superior scale jobs, superior scale
    work often incurs a weight penalty, high weight--> slow accelleration,
    high wing loads, long takeoff/landing runs.
   
    Or because most propeller planes are front-engined; most
    DF's are center-engined.  This makes the DF have a smaller pitch
    and yaw moment, so they climb/dive/skid much more quickly.  Quickly
    enough to eat novices?
   
    ------------------    
                    
     Does anyone KNOW what the thrust vs. airspeed curves for the 
    DF units are?  
                       
    ------------------
    
    OK, it looks like 
    	
    	"Building a DF for a first RC aircraft is a gamble akin to 
    	  drawing to an inside straight".
    	
    I get the picture.                                 
    
    If someone can get me thrust/airspeed numbers or curves, I think
    that this is worth looking into yet.  I'm learning a lot about the
    whole area from this discussion.  And though I'm not convinced
    its _undoable_, I'm no longer convinced it's _doable_ either.
    
    (Just how big is a Turbax, anyway ???)
    

    After re-reading (my own) response, I realize it doesn't convey
    one thing I wanted it to...
    	
    	THANKS!
    	
    I really do want to thank you all for the time and effort (and 
    sympathy!) on this line of thought.  It really does help, and
    I appreciate it.
    	
    	-Bill Yerazunis
    

Bill, I doubt you'll ever find a bigger Woosy on the subject of
engines than myself.  Until this year I was terrified of anything
bigger than an .049, including my Enya .09.  But I knew that if I
was going to play this RC game, I'd better get over the fear,
pronto.

What helped greatly was that my first 'big' engine was a K&B
Sportster .20.  Now, I've cursed and bemoaned that engine many
times in this file, but I've gotta say one thing good about it:
Its quiet.  Its a real pussycat.  I can run it in my front yard
by the garage, and people walking by on the sidewalk 30ft away
are unaware its running unless they look.  Even my wife, who
complains about everything, does not mind that engine.  So my
advice is get a quiet engine; the K&B I endorse, maybe the .45 is
just as good.  Now I run my OS .25 and it doesn't bother me, even
the Arrid Rodent has talked me into upgrading to a .45!

Speaking of which, check your AMA flyer this year.  Fox is
offering a .45 with spinner and 4 plugs for $60!!!!

Such a deal.

    Ok, I'll say it again and join the rest of you: If your first
    plane has to be a DF because you're afraid of props, then get
    an R/C car and forget about planes. Again, it depends on where
    you'll fly, but at our short, grass field the last time I saw
    a guy try to take off a DF he carried it out to the VERY end of
    the field, tail in the tall grass, held on while he revved it up,
    let go, and it made a bee-line down the runway all the way to
    the tall grass at the other end! That's a pretty expensive go-cart,
    he could have done a lot better with an off-road car! I'm lots
    more scared of the DFs than the prop-jobs. A healthy respect for
    a spinning prop is a very good thing, but paranoia about it is not.
    I watched my dad get his finger chopped right through the nail down
    to the bone when I was a kid, but he didn't stop, he was just a
    lot more careful next time!
    
    So, the vote is still unanimous!
    
    Dave

    Bill,
    I guess I might as well help beat a dead horse to death.  I have
    been in the model business off and on for about 40 years.  Most
    of that time it has been with gas type engines and even though
    I have been bit several times (who hasn't), I don't think I have
    ever received as much as a slight scar on any of my hands or fingers.
    I do have many scars on my fingers, most of them by exacto knives.
    I think you should be more fearful of building than of starting
    and tuning an engine. .
    
    Just a plain (plane?) klutz.
    
    Ken

    Another interesting tidbit for your psychoanalysis:
    	
    Chopper blades (both real and model) do NOT scare me!  At least
    not as much as they should for my own personal safety.   
    	
    Weird, huh?
    	                                                   
    
    Does this mean I should go into choppers?  X-(:-)     
    
    ----------------------
    
    Getting off the psychological tangent and to the aerodynamics tangent:
    	
    	Why can't a DF take off from a grass field?  
    	
    	Why can't a DF be super-stable?
    	
    etc?
    
    

    Bill,
    
    I won't comment on yer' lack of fear of helicopter rotor-blades except
    to agree with you that it's weird.
    
    > Why can't a DF takeoff from grass?
    
    We're dealing with a totally different kinda' thrust with a DF.  I'm
    not able to lay an aerodynamic explanation on ya' but a DF's thrust
    is considerably less than that of an equivalent size engine driving
    a conventional prop...I'm swagging here but I'd speculate that the
    DF only develops 2/3 the thrust of a conventional prop setup [or less].
    This thrust is only developed at the engine's absolute peak RPM and
    takes the form of a column of air pushing rather than pulling the
    aircraft through the air.  Like full size jets, initial acceleration
    is slower than a prop-job and, with the considerable resistance
    of grass, rotation speed is difficult to attain.
    
    Other factors also exist; because of the less efficient nature of
    the power source, power:weight ratios are higher and, even though
    airframes are built exceptionally light, effective wing loadings
    tend to be higher, all of which constitutes a less efficient flying
    machine at lower speeds, one of the many reasons why DF's must
    typically fly faster.  One remaining factor is the landing gear
    arrangement.  As a rule, jets have a tri-gear setup which places
    the main gear way behind the CG.  In order to rotate the nose, thereby
    achieving a flying angle of attack, high groundspeed must be attained
    before the elevator has enough leverage to raise the nose when the
    center of rotation (the main gear) is so far behind the center of 
    weight (CG). 
    
    suffice to say that it simply takes a much higher rotation speed
    to get a DF airborne than it does an equivalently powered prop-job
    and grass impedes attaining this speed considerably. It's not
    impossible but it can be very difficult/frustrating and I have no
    doubt that certain smaller grass fields are totally unacceptable
    for DF operation, period.
    
    > Why can't a DF be super stable?
    
    * They can!!  A case in point is the Byron F-16 which seems almost
    stall-proof no matter how ham-handed the pilot is.  The point is
    that jets, due to the very nature of their propulsion principle,
    are just about _required_ to fly faster and _SPEED_ is one of the 
    beginner's worst enemies.  Time to think and react correctly is
    the biggest asset a novice can have and this commoditiy simply
    is not among a jet's characteristics.   Again, I have to encourage
    you to put this idea out of yer' mind, address and control this
    fear of props and get about the business of learning with a nice,
    slow, friendly and, most importantly, simple trainer.  Once you've
    paid yer' dues, many of these answers will become obvious to you
    and you can then choose to _advance_ to jets if they are still
    attractive to you.

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

    re DF efficiency: Bob Violett claims that his DF system is about
    85% efficient (ie translates engine HPO into thrust)
    
    md

    A better option than DF for a beginner would be a sailplane.  This
    eliminates the prop and they fly slowly.  I'm not advising this,
    but it is something to consider if you really want to fly propless.
    
    Charlie
    

    Re: .-1,
    
    _BUT_ don't begin to consider that learning on a sailplane will
    qualify you to move up to jets.  You'll still need to go through
    power planes as a prerequisite to DF.  There's no free-lunch in
    this question; either a guy pays his dues beforehand or he goes
    through enormous expense in crashed aircraft and ruined equipment,
    the likely result being disenchantment with and departure from what
    could have been an enjoyable hobby for him.  There_are_NO_shortcuts!_

      |                                                                  
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

    Correct as usual, King Friday...
    	
    One ALWAYS has to pay the dues, one way or another.  I understand
    that; the first time I build any RC car, I always goof a few things
    that come out oooh-so-much-nicer on V2.0 . It happens, can't explain
    it, can't avoid it.  I just keep the epoxy handy...
    
    Time to retreat into severe self-examination...
    	
    	Thanks again,
    	Bill
    

	re .65


	I've seen that figure quoted for the Viojett... Other
	fans are around the 60-65% region.... No wonder they're
	so hard to get up.....

	Of the planes that I mentioned at our club, very few of 
	them fly regularly simply because of the hassle involved,
	both with the field and the planes themselves....

	But I still want one......


	cheers

	bob

    Bob Violett models take VISA & MASTERCARD. 
    
    
    MD

    re -.53
    
    ... SIMPLY stick with sailplanes ...   !!!!!!!
    
    Hey Rodent! If it was simple, you guys with castor oil all over
    your selves and your planes wouldn't get so nervous every dead-
    stick!!!   :-))
    
                             |                      
   \	       	         ____|____                      /   Regards,
    \________________________O_________________________/    Frank.
    

Here is some very interesting information that I received from Hurricane 
Fans.  I make no claims to its accuracy, realize that it is from an 
advertisement.  Insert disclaimer here.



			HURRICANE FANS


	Hurricane fans can configure a fan to provide maximum 
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	All aluminum, hub and spinners are made from the finest 7075 T6 
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close that further balancing may not be required.
	All blades are cloned from a single precision injection mold and 
made from the finest space age CO-POLYMER material for durability and 
strength.

			

			RELATIVE FAN DATA

IN GENERAL:

	The data generated by my computer is to be used only as a 
reference...That is to say...

(The average fan velocity, airplane speed, and fan efficiency)

has been computed by means of combining mathematical equations and known 
practical experience.
	Using this method, determining the difference between one rotors 
specifications and another can be quite accurate.
	The speed numbers are not to be taken as absolute values, but 
more to relate one example to another.

The hub to tip ratio, the swept area, the blade pitch, and the tip speed
are all mathematically accurate.

	The tail pipe diameter given is designed to maintain a 
combination of maximum static thrust and highest tail pipe velocity.  
Reducing the tail pipe diameter will reduce static thrust while it will 
increase tail pipe velocity.

		SOME INFORMATION ON OTHER FANS

Manuf	Dia Fan	Dia Hub	#Blades	Pitch	Tip Ang	Engine	Range RPM

Viojett	4.65	2.05	7	9.48	33	.72	very high
TurbaxI	4.75	2.18	5	7.60	27	.40-.46	very high
  " III	4.75	2.18	5	7.60	27	.65-.81	ultra high
Dynamax	4.88	2.25	11	6.7-7.9	23-27	.65-.81	very high
Byron	6.00	2.25	5	9.6	27	.65-.81	medium
Hurricane
	4-6  1.75-2.25	2-10	6-13	20-35	.25-.90	low-ultra hi

	RPM RANGES FOR DUCTED FAN ENGINES ON THE GROUND

LOW		BELOW 18000
MEDIUM		18000 TO 20000
HIGH		20000 TO 22000
VERY HIGH	22000 TO 24000
ULTRA HIGH	ABOVE 24000

Remember that different engines have different usable rpm ranges... But, 
in practice, the lower the rpm, the longer the engine lasts.

			IN GENERAL
	
	A minimum fan tip speed of 325 mph should be maintained for good 
operation of ANY FAN.

SIZE OF FAN	RPM TO MAINTAIN THAT TIP SPEED
	4	25500
	4.6	23500
	4.75	23000
	4.94	22500
	5.125	21800
	5.875	18500
	6	18200

			AS YOU CAN SEE

The larger the fan diameter, the lower the rpm's have to be to maintain 
325 mph tip speed.

SIZE OF ENGINE		MAX RPM'S NEEDED ON THE GROUND
	.25-.46			24000
	.60-.81			22000
	.90			21000

	AND NOW TO CHOOSE YOUR NEW HURRICANE FAN...

1)	Determine the total weight of the completed airplane.  Dry 
weight.
2)	Choose the largest diameter fan that will fit easily in the 
airframe from the (airplane weight/fan-engine size) guide below.
3)	Choose either a tractor or pusher.
4)	Decide if the fan shroud will have a bell mouth or it will be 
straight cut to accept a inlet liner (tractor only). A bell mouth shroud 
is the easiest to install and maintain, but the inlet liner will give 
better performance.

		GUIDE--AIRPLANE WEIGHT/FAN/ENGINE

MAX WEIGHT	MIN FAN DIAM/ENGINE SIZE

5# OR LESS	4" .21-.28
8# OR LESS	4" .40-.46
10# OR LESS	4.6 .65-.72
10# OR LESS	4.75 .65-.81
11# OR LESS	4.94 .65-.81
12# OR LESS	5.875 .65-.90

	The blade tip angle or pitch, and the number of blades will be 
determined by the size of the engine and the horse power, keeping within 
their best rpm range for long engine life.

FOR MORE INFORMATION CONTACT

STEVE KORNEY
HURRICANE FANS
14835 HALCOURT AVE.
NORWALK, CALIF. 90650
(213) 864-8891

    How about that !! Someone took the time to explain various parms
    that affect performance.. 
    
    neat !!
    
    
    tx,
    
    md

    In the July issue of RCM there is an advertisement for a hobby
shop called Yellow Aircraft & Hobby Supplies LTD.
  They have a kit for an SR71.

  The full details that are supplied are:

		Includes:
			o Power packages (2 O.S. 77 DFs)
			o Retracts and scale struts
			o Fans and pipes
			o Outlet ducts
			o Fiberglass fuselage
			o Fiberglass exhaust ducts
			o All bulkheads installed
			o All gear mounts installed
			o Foam flying surfaces
			o Speed envelope 160mph

		Length: 105 inches
		Wingspan: 55 inches
		Weight: 19-21 pounds

		$1450 for first 25 kits  {whatever that means}
		$699 kit only

	All aircraft available assembled with or without engines from:
	
		Bob & Lewis Model Building Services
		Call or write for prices
		(718) 375-6668
		1982 West 5th St.
		Brooklyn, NY  11223


	Yellow Aircraft & Hobby Supplies LTD.
	Suite 201
	3040 Palstan Rd.
	Mississauga,  Ont.   Canada  L4Y 226
	Tel: (416) 273-6757



            ========
              \  /               /---
     | --------\/\___/----------/___|
     |_|       /\      Jim    ______/
     | |______/__\_______-----
            ========
               |
              /--\
              \__/

    Re: .74,
    
    This is the very Blackbird that Dennis Crooks had at the Spring
    1/8 AF Scale Fly-In.  Very impressive/exotic looking craft over
    7-or-8' in length.
    
    Unfortunately, we didn't get to see it fly; Dennis took it out to
    test-fly in private during the week prior to the fly-in and had
    a severe pitch-oscillation probleem at low/no power caused by,
    evidently, a too far aft C.G.  Naturally, this made landing this
    beast somthing of a chore and, while he made it, Dennis damaged
    the landing gear and gear mounts to the extent that he opted to
    wait 'til he got home to repair and continue flight trials.
    
    This ship is most definitely _NOT_ for the inexperienced or the
    faint-hearted.     

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

    I thought people might be interested in an update on ducted-fan
    activity in the UK -

    My father and I went to the UKs annual ducted-fan fly-in at RAF
    Wroughton, near Swindon, this past weekend. We were both very impressed
    by the quality of the models and the flying. We saw no real crashes all
    day (a few untidy arrivals tho' :-) ) and the general performance of
    the models and their reliability seemed very high. There were 75 pilots
    and models registered.

    The highlight had to be seeing the world scale champion, Belgian
    Phillipe Avonds with one of his twin-engined F15s. His flying was some
    of the best seen all day, doing high speed passes along the runway with
    loops and half-rolls at either end - just like a full size display. The
    size of the model clearly helps, but he is a very smooth pilot. It had
    plenty of power - you could hear him throttling back during the
    manouvers. Apparently he flies F16s and F15s for the Belgian Air Force.
    A kit for the F15 is available at �500. Looked like a bargain to me :-)

    There were a couple of other F15s and several F16s (I think most were
    from the Byron kit). Some of the F16s were a little slow, they flew OK,
    but the effect is greatly reduced if the model doesn't appear to be
    going fast enough. One was definitely on a par with the Avonds F15
    though, and was doing fast low passes and realistic 'breaks' for the
    landing. This one flew several times in the day with no sign of
    trouble.

    The most impressive of the UK models were a large (~6') twin-engined
    Tornado, complete with swing-wings, that flew very well, and an equally
    large Phantom that got the most (and well-deserved) applause for
    executing a go-around after a less than perfect round-out - the second
    landing was much better. These were both built out of foam and covered
    in brown paper(!), but you couldn't tell. The Tornado was very well
    detailed. Alongside them was a (similarly constructed I think) smaller
    model of an ME163 , the German WW2 rocket-powered flying wing. Not the
    most obvious subject, but it flew very well - dropping its  two-wheel
    dolly on take-of and landing perfectly on its skid (I think he had a
    little more throttle control than the original tho'...)

    A model of the ill-fated TSR2 (a 'Tornado' class aircraft from the 60s
    that was canned by the government of the time), didn't quite make it
    off the ground. There was a stiff cross-wind, and that combined with a
    narrow undercarriage meant it was tipping over on its take-off run. The
    final attempt resulted in it disapearing into the long grass just at
    the point of rotation! Looked like in better circumstances it would
    have flown. As an aside, Wroughton is an excellent site, with use of a
    smooth runway and acres of long grass that proved the saviour of
    several dead-stick arrivals.

    There were several models of an 'Albatross', an Eastern Bloc trainer,
    that I think were from a kit, certainly all flew well. A couple of
    Grumman Panthers that did some 'formation' flying towards the end of
    the day and looked very nice. About seven Folland Gnat's - most in Red
    Arrows colors, but I never saw two in the air together, shame. Several
    Mig 15s. A Gloucester Javelin that looked a little rough on the ground
    but flew very well, fast yet quiet. The lone Starfighter made a short
    but spectacular display (how do those things fly??). There were various
    F5 and F20 variants in all sizes. All flew very well. The Thorpe
    brother's were there with their F20 (now at 9lbs, up from its original
    7lbs they said) that flew several times, and an F18 that was again not
    quite fast enough to look convincing. The UK's chief exponent of
    smaller DF models, Alec Cornish-Trestrail was there with several models
    powered by .051-.30 sized engines. The best, which I confess I didn't
    see fly this weekend, but have seen previously was a small twin-engined
    Mig that flies very well.

    All in all, it was an excellent day - I'd recommend anyone remotely
    interested to check this one out next year. 

    I have 40 minutes of the models and the flying on a PAL format VHS
    tape, that I'd be happy to lend to anyone in the UK who's interested.
    Mail or call me. If there is enough interest, I can get a second copy
    made to send to the USA (the original is on 8mm video). Remember it is
    in PAL format, so you need a multi-standard player. 

    cheers,	
    	Scott
    

    A friend over here (Italy) has a large Byron fan kit. I don't recall
    the model but has a 7.5cc engine. Anyway the kit calls for a particular
    fan and it sounded like Scotci, Scottzi,,,, I didn't have a pen.
    Anyone know about this fan ^? or info on where to get? He has tried
    here, Germany and Switz..
    
    Thanks, Ed

    Ed,
    
    I think the fan you refer to is the Scozzi.  I wouldn't swear to this
    but I think the Scozzi was an early technology unit which was improved
    by Bob Violett into the turbax fan.  Bob recognized a few years back
    that the Turbax was becoming obsolescent so he sold the unit to Larry
    Wolfe (Jet Hangar Hobbies) who improved it somewhat into the Turbax-III
    (though the original Turbax-I is still available).  However, the
    Turbax, in any form, is woefully inferior to the current, state-of-the-art
    fans on the market, e.g. the Byron, Tom Cook and, most especially, the
    Viojett from Bob Violett which I believe to be the best, most efficient
    fan obn the market today.  Frankly, I wouldn't bother trying to locate
    ANY one of the older-tech fans as performance will undoubtedly be
    disappointing.
    
    Incidentally, I doubt if the kit your friend has is a Byron kit since,
    Byron, from its first jet kit (the MiG-15), has had and would,
    naturally specify, its own Byron fan unit.  Also, with the possible
    exception of the MiG-15, Byron's jets are simply too large to be
    adequately powered by a 7.5 (~ .46 cid).  Most all Byron Jets require a
    _minimum_ of a .61 and virtually _all_ of them (at least the successful
    ones) are flying with a minimum of .77 up to .91 cid fan engines. 
    
    Hope I did more than add to the confusion here.  Please verify and let
    us know exactly what kit your friend has and, maybe, we can recommend
    what fan/engine combo he should try to install.   

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

    Thanks Al. Will check and verify this weekend.
    ciao, Ed

    Ed,
    
    Al's right.  Scozzi/Violet is now owned by Larry Wolfe (Jet Hangar
    Hobbies) and it is called the Turbax I (.40-.46 power).  THe improved
    Turbax III is for .61 and up.  Both are 5" fans.  Another choice
    in a 5" fan is Tom Cooks (Jet Model Products) Dynamax unit.  It
    on sale for $80 currently and you specify what engine you are running.
    It comes ready for your engine (some assembly required).  
    
    If I can be of further assistance, send mail to MDVAX1::SPOHR. 
    DTN 445-6577.  I'm currently getting into ducted fans myself and
    have collected info from several manufacturers.
    
    Chris Spohr

    At a recent meet for scale jet aircraft (MACH 2.2) here in France, one
    contestant flew a jet turbine - Not a ducted fan.
    The thing turns at around 100,000rpm. This is as reported folks, not a 
    figment of my much used imagination.
    
    I shall dig out the details this evening for tomorrows readers.
    
    This incidentally must be the third or fourth proto that I have heard
    about in the last 10 odd years.  The most sucessful apparently being a
    unit built and flown in the UK. 
    The skimpy information that I had on the UK unit was that it was an
    axial front end compressor with a continuous burner chamber around the
    circumference of the unit.
    Metal work took many many hours  as it was "erosion" machining if that
    is the right term. Much like sand blasting rock to shape!
    
    These units are nothing like the pulse jet type units which incidently
    powered the full sized V1 - just a bell mouth inlet into which air is 
    compressed, a plenum chamber for fuel/mix and burn and a straight through 
    "tuned" pipe for maximum thrust.
    
    Fault perhaps of lack of current pertinent documentation, I have picked
    up no reports coming out of the USA.
    
    Would any of you notes out there in the big wide world fill in the
    holes, if there are any on this rather skimpy subject or is there
    already a Jet Turbine note that I have missed.
    
    	regards  George Frost.
    
    

    Re: .-1, George,
    
    There is a team of modelers/engineers located in Mesa, Arizona that has
    had a VERY successful gas-turbine jet engine in operation for the past
    3-years or so.  They've demo'd it for us at noon-breaks during our 1/8
    Air Force Scale Fly-Ins twice in the past and, most recently, flew it
    during one of the lunch break demos at Top Gun in Mesa last April.
    
    I don't know much about it (or any other jet engine for that matter)
    but I believe they solved the compressor problem by using compressed
    air or gas in pressurized onboard tank(s) to handle this chore.  Yer' 
    memory is quite correct regarding turbine rpm as the Mesa engine also 
    turns in excess of 100K rpm. It sounds EXACTLY like a full size turbo-jet
    engine except that it is [surprisingly] much quieter than one would
    expect.
    
    Commercial applications are not expected anytime in the near future
    owing to safety considerations revolving around the extremely high
    operating rpm and compressed gas required for operation.
						 __
				|      |        / |\	   	       
      	         \|/		|______|__(o/--/  | \	   	       
      | |        00	       <|  ~~~  ____ 04 ---- | --------------------
    |_|_|        (O>o		|\)____/___|\_____|_/	   Adios amigos, Al
      |     \__(O_\_	        |	  |___/	 o	   (The Desert Rat)

The obvious application would be to sign up the military for drone powerplants. 
That gets you the devolopment and production before you have to ask the general 
public to pay off the expensive R&D.

    Two things have happened since I promised to fill in the details on the
    jet turbine note earlier.
    
    I had to zip off to Italy for a couple of days, and the model mag that
    carries the data on the turbine cannot be located. My daughter loves
    looking at pictures in magazines and also scrunches up the pages when
    finished?
    When I have straightened out the domestic disorder I shall post the
    correct details.
    
    What I remember is that the unit measures about 11", weighs about 3
    pounds and has a thrust to weight of better than 1:1 (powerplant only).
    Fuel is speculated as propane.
    Externally the unit looks like un unpainted coke can with no fans,
    blades pipes whatever showing.
    
    Jim, your previous note suggesting a  drone application might be an
    answer, however various reconnaissance/target drone applications are
    being flown in active combat in the middle east and are VERY succesful.
    Range and endurance are a big factor and currently are accomodated with
    conventional piston engine and prop. Turbines being much more thirsty
    beasts might not get a better reception.
    By the way, the smallest commercially available turbine is the Noel
    Penny, the French also make a tiny one - all-up weight for both is around
    20 kilos or 42 pounds.
    
    	regards George Frost 
    
    
    
    
    more later
    
    	regards  George Frost
    

    I have the promised information for those interested.
    
    The unit was designed and built by Michel Serrier and Alain Deslick, a
    pair of French modellers. Not patents have as yet been registered so
    the pair are apparently very cagey about what and to whom they talk.
    
    A commercial project is afoot with an approach to ROBBE in Germany.
    
    Details are as follows:
    
    	-	No long tuned pipe (as for pulso units)
    
    	-	Unit is currently flying in a Saggitario with extended wing
    		to handle the increased wing loading. 15.4 lbs. auw as against
    		11 lbs. for the pulse jet.
    
    	-	Pressure gauge in the cockpit.
    
    	-	Length	11.8" diam, 5.5" weight, 4.84 lbs
    
    	-	Fuel is liquid propane under nominal? pressure
    
    	-	Power-on time is approximately 5 mins. and throttleable
    
    	-	Rpm more than 100,000
    
    	-	Instantaneous light-up by ingestion of compressed air and 
    		glow plug ignition
    
    	-	Noise: 104da, at max power on the ground.
    		       70Dba, in flight
    
    	-	Aircraft speed 200km/h (120mph)
    
    	regards George Frost	   

    I have just got a copy of the German Flug- und Modelltechnik (tks
    Jorg), and the turbine mentioned in the most recent notes is featured.
    
    It is now commercially available, manufactured in France by one of its
    co-developers who incidentally also manufactures full sized axial fan
    engines.
    
    This one is axial compressor up front,
    
                     weight 1.6Kg
    		     diam   110mm
    		     length 300mm
    		     thrust 5kg
    		     fuel propane
    		     price 17,000 French Francs - 2,830$
    
    Manufactured by	 JPX-ZI Nord
    			 F-72320 Vibraye
    			 France

    
    
    	I'm pretty sure that the AMA insurance and the SFA insurance
    will not cover anyone operation a "true" jet engine.  I wonder
    if your home owners will?
    
    
    Tom

On Saturday I saw this new gas turbine (in a saggitario) fly at
Sandown (Esher UK).

This motor runs on propane and really shifts. It sounds just like a real jet
engine (well it is).
All the ducted fan boys where getting their cheque books out
to sign away the �2700 required.

This thing stole the show, I reckon they must have sold 100 when he pulled
it vertical and went. Made the DF planes look rather pathetic.

I'll get the details tonite from the show programme but from memory it was
basically the same specs as George mentioned in the previous replies.

If there's anything u want to know, post it here and I'll try and find out
from the importers here in the UK.

Ian.

    
    I saw a report on this engine last month in one of my mags. Sounds very
    impressive, though not as impressive as the $3000 price tag.
    
    AMA will cover "turbojets" with special approval. What is required I
    have no idea.

    
     True, they cost $3000, but I heard that if you order 
    10 or more , the cost is only $2950! :)         
    
     I'll put the order together, just send cash, and I'll take care of
    the rest! :)

    This sounds like a neat engine, and apparently a lot more powerful
    than earlier model turbo-jet attempts.
    
    To be historical consistent the first engine in the U.S. should be
    installed in a scale P-59.
    
    Wasn't it just about 50 years ago that the first Whittle gas turbines
    were sent to the U.S. ?
    
    Terry

Although I wasn't at Sandown on Sunday they had a radar trap for the JPX
jet. Talking to the chaps in the shop they made 165mph without trying.
The guy flying the saggitario (Pete Marston) visibly shook when the speed was
announced and promptly declared he was low on fuel :-)

There's plenty more left yet.

Also its looks like Bob Violet will be the importer for the US.


Ian.