Conference vmszoo::rc

    -.1
    
    Have you started building your Extra 300 yet?  You said you bought a
    OS.61 for the bird.  Do you think this will be enough power?  I will be
    putting an OS 120 four stroke in mine.  Hard part is coming up with the
    $$$$$$ to get the motor.  Solved the issue with the rudder being weak. 
    I just installed some carbon fiber to a cross piece.  Now it's nice and
    firm.  Should give me years of faithful service......I hope.
    
    John

    Nope, I haven't started yet, but probably will soon.
    
    The docs inside the box imply that a .61 would be plenty. I went with
    the SF, which is a little stronger than the FP. We'll see.
    

    Loren,
    
    Be careful when your building.  Some of the pictures are incorrect.  It
    shows some of the parts being upside down.  Solved the issue with the
    rudder being too weak.  I used some carbon fiber on the top cross
    member.  Seems rugged enough now.  The instructions don't call for much
    use of epoxy.  I have a hard time believing that CA will hold a
    firewall together.  Building experience will help you get thru any of
    these problems.
    
    John

    Well it's finished.  Ended up using dual servos for the elevator and
    duals for the alierons.  Had to heavily modify the front cowling to
    conform to the true lines of the bird.  Front edge of the cowling was
    almost 1 inch above the nose cone.  Even with an OS 120fs and six
    servos, it only weighs 9 pounds even.  Should have plenty of virticle
    even at 7200'.
    
    John

Article 2782 of rec.models.rc:
Path: lemans!news.crl.dec.com!nntpd.lkg.dec.com!pa.dec.com!decwrl!mips!munnari.oz.au!network.ucsd.edu!dcdwest!plb
From: [email protected] (Phil Blais)
Newsgroups: rec.models.rc
Subject: Goldberg Extra 300 - Kit Review
Message-ID: <[email protected]>
Date: 7 Apr 92 17:07:44 GMT
Distribution: na
Organization: ITT Aerospace/Communications Division - West
Lines: 84


I just recently completed the Goldberg Extra 300 and "for what it's
worth" I offer the following:

Construction:
Very straight forward and well "documented" in the instruction
manual. The trickiest area was the 1/32" ply turtle deck.
The turtle deck requires considerable "bending" and is
best done "wet". I sprayed the ply with water, rolled it up into
a tube and held it together for about 15 mins. with tape prior
to gluing. This worked well and resulted in a very satisfactory
job.

The canopy and canopy frame are a bit tedious to get just right
but I was careful and took my time and it came out quite nice.

The kit includes jigs for joining the two wing halves. Basically
a crutch for each wing tip and a saddle for the center section.
I highly recommend using the jig fixtures when joining the two
halves with weights placed strategically to hold everything in
place while the glue dries. This will insure a flat (no dihedral),
warp free wing.

<Flame on>
My only complaint with the entire kit was and is the main gear.
Two pieces of preformed 3/16" wire (one left and one right) form
the basic gear. The gear fairing is built up by laminating pieces
of ply together and attaching them to the wire gear. This results
at best with a flimsy and very springy main gear which IMO is a
piece of junk.
<Flame off>

I recognized the need for a stiffer gear in the
building process and initially figured I'd use a Hallco gear but
found, much to my delight, a composite main gear made specifically
for the Goldberg Extra 300. This gear is great. Its curved the way
a 300 gear should be and its stiff. A flying buddy who completed
his 300 the same time I did flew his with the stock gear, bounced
his first landing (about 5-10 feet) and quickly retrofitted the
composite gear. (cost of the composite gear was ~$40.00).

Finishing:
I usaully spray paint all my planes with PPG Dizler Acrylic Urethane
but for the 300 I decided to try the new 21st Century Fabric from
Coverite (dark blue, light red and white). Overall I was very
impressed with this covering. It handles well, has good shrink
charcteristics and can be trimmed with itself with no bubbles.
My only complaint was its lack of adhesion  especially to
plywood (lite ply) which comprises much of the 300 fuse. I ended
up using Balsarite on the entire frame and the adhesion problem
was solved.

The fiberglass cowl and wheel pants (obtained from T&D fiberglass)
and part of the canopy were painted with matching 21st Century
paint. Paint matched the fabric well and so far is holding up
nicely.

Engine:
I use the O.S. FS120 Surpass II with pump and APC 14x12 or 14x14
prop. This makes for a beautiful combination with the 300.

Flying:
The 300 with the above engine is an awesome combination. It flies
like a pattern plane and really groves like its on a rail. Stall
characteristics are very gentle and to date I have found no
bad characteristics what so ever. Landings are somewhat faster
than a trainer but not much. The only problem is airspeed. the
300 is so clean and the APC prop so efficient that it takes quite
a while to bleed off speed. My first few landing attempts ended
up in go arounds because I was much too hot.

Summary:
I've been building and flying RC planes for close to 20 years
and this is one of the most impressive planes I have ever
owned. I'm amazed that a ~$100+ kit looks and flies as good as
it does. Especially when I compare it to other planes in my
hangar which include $2000 jets and some very expensive
1/4 scale models.

-- 
phil blais  N6KXD (ex WD6ETL)    ITT    Aerospace Communications Division
[email protected]           DEFENSE    10060 Carroll Canyon Road
						San Diego, CA 92131
						   (619) 578-3080

    What is the source of the composite landing gear for the 300?  There
    was a mention of Hallco, but I wasn't sure this is the company that
    makes it.
    
    I just started building this kit, and have ordered a Super Tigre 90K
    for it.  I looked at the price of an OS 120 four stroke, and got
    instant sticker shock.  I'm wondering what the ST 90 will be like in
    comparison.  Anyone want to hazard an opinion about what I'm going to
    expect for performance?  Looking at the RC Report lab tests of the ST
    90K, it appears that this engine likes a 14x5 prop for maximum thrust.
    
    This plane got rave reviews in both MAN and RC Report.  Can't wait to
    fly it.
    
    Regards,
    Joe

    Just thought of another question.  Has anyone bought the RC City
    fiberglass replacement cowl for the "300"?  I'm curious if it has the
    same problem fitting to the fuse as the stock cowl has?  Or did they
    fix the problem?  I'm interested in buying the fiberglass cowl, but
    won't pay the extra $25 if it has the same problem as the stock unit.
    
    Regards,
    Joe 

    I've built mine, but haven't flown it yet. Pretty plane. 
    
    I agree that the landing gear looks like a weak point. I might be
    tempted to upgrade it. I didn't have any problems with the cowl,
    though. My stock cowl fit great with minimal effort.

    
    Joe,
    
      I saw a Goldberg Extra 300 at a Pattern contest at Westover AFB a
    couple of weeks ago. It weighed about 11 pounds with a YS-120
    installed, and had pretty much unlimited vertical. I would think a
    ST-90 would fly it well, but vertical would be limited. I have been
    flying a 7.5 pound Panic with a ST.90 and a 14/7 prop. It has decent
    performance, but is by no means unlimited. The Panic has MUCH more
    drag then the Extra though, so a direct comparison is not really
    valid.
      The gear WAS a weak point, as it was flexing and vibrating all over
    the place ( and this was on asphalt! ). I would DEFINATELY look at
    upgrading the gear, as the stock gear wouldn't last 3 seconds at the
    Merrimack field.
    
                                                             Dan
    

    Thanks for the responses so far.  
    
    I will be looking for an alternate to the landing gear, and would like
    to know if there are any after market companies that have one for the
    Extra.
    
    ALthough the general observation about the stock 3/16" landing gear is
    that it seems to be _very_ flimsey, the reviewers say it seems to hold 
    up nevertheless. 
    My experience with very "springy" gear is that you will get more
    bouncing, hence less control on the ground.  I stiffened up the U/C on
    the Super Aeromaster, the Taube, and the Eindecker, and had _much_
    better performance while landing and taxiing.  I think this may be
    analogous to stock suspensions vs racing (stiff) suspensions in cars. 
    The stiffer the suspension, the better road control you have, and
    cornering is much better.
    
    Regarding the ST90 2C vs a 120 4C, my druthers are to have the 120, but
    my budget can't handle it right now.  The premium for going to the OS
    120 is _twice_ the price over the ST 90!!  According to the data I
    have, the ST 90 is more BHp than the OS 120, but that doesn't say
    anything about thrust, so they may be reasonably close in overall
    performance, with the ST 90 probably having the edge in top speed.  I
    don't think I'll be dissappointed with the ST 90.
    
    The tail feathers are done, now on to the wing.  
    
    Regards,
    Joe

    
    Personally, I would take a YS120 over the OS120 any day, but the price
    is almost the same!
    
    
    As an alternative for the gear, get yourself some 5/32 music wire, bend
    it to lay against the inside of the aluminum gear, and FIRMLY attach it
    to the aluminum gear with j bolts. Run it from about the axle, up
    across and down the other leg. You will be amazed at how it will
    stiffen the gear!

    Re: -.1
    
    I may have misled people about the stock landing gear.  It consists of
    two identical peices of prebent 3/16 music wire which gets covered with
    ply and balsa fairings to make it look like a piece of flat material. 
    It is not sheet aluminum.  Therefore, your suggestion cannot be
    implemented based on what I have in the kit.  Thanks anyway.
    
    And, yes, I've heard that the YS120 is the superior engine.  I'll keep
    dreaming....
    
    Regards,
    Joe

    The landing gear on mine hasn't given any problems at all.  Although I
    don't land in grass, just fairly smooth pavement.  You'll like this
    bird for it's takeoff's and landings.  Very predictable and stable on
    landings.  Slows down nicely.  How did you strengthen the rudder
    assembly?  Good luck!
    
    John
    

    
    Have you thought about using a muffled tuned pipe on the ST90 ? It for
    shure boosts the performance. 
    I must admit that on some models tuned pipes just don't fit. You've
    basically three choises : performance - good looks - $$$$$$$$$
    
    
    Bernd

    re .13
    
    John, it sounds like your experience with the stock landing gear has
    been good.  I will be flying off a rough grass field, so I'm concerned
    about the springiness others have reported.  I wish Goldberg had made
    the landing gear out of tempered aluminum sheet. That would be the
    answer to what I'm looking for.
    
    BTW, your comment about strengthening the rudder assembly has me
    guessing.  What is the problem with it?  I guess I'm somewhat concerned
    with the butt joints breaking, so I will be putting gussetts in each
    corner for additional strength.  Are there other problems?
    
    Thanks for all the info.
    
    Regards,
    Joe  

    After I was done building the rudder assembly and tried to remove it
    from the building board, it broke at the top.  I figured that if it
    couldn't handle being slightly stuck to a building board, it probably
    couldn't handle the stress of flight.  I didn't want to add gussetts
    because of the added weight.  Along came carbon fiber.  A few strands
    ca'd to both sides of the top cross piece took care of the problem.  I
    also used the fiber on the cowling which I had to "slice & dice" to fit
    the OS 120.  Come to think of it, I used it on the gear sheeting also.
    
    Hope this helps,
    
    John 

    Re: -.1
    
    John, thanks for the additional detail on how you strengthened the
    rudder.  I think I'll do the same.
    
    Now for another question.  Given that you are using a 120 in your bird,
    what arrangement did you use for the elevators?  I'd be curious if you
    used one servo with a split pushrod at the elevator, or two independent
    servos with dedicated pushrods?  If the latter, how did you do this
    installation?  I'm going to use two elevetor servos with dedicated
    fiberglass pushrods, and where they show the on/off switch, I will put
    the second elevator servo right there, and find another spot for the
    switch.  This will give me a completely symmetrical arrangement of
    elevator servos and pushrods.  Plus it will give me some backup control
    if one of the servos quits.
    
    Also, I assume you used one servo per aileron.  How did this work out?
    
    My biggest complaint about this kit so far is the warped leading and
    trailing edges for the wing.  I'm trying to straighten them out using
    ammonia and water and then letting them dry in a counter-bent position,
    but this may not work in every case.  We'll see.
    
    Regards,
    Joe
    

    Well, I found the answer I was looking for.  I spoke to Fiberglass
    Specialties yesterday, and they offer a prebent tempered aluminum
    landing gear for the Extra 300 for $19.95 plus shipping.  Interestingly,
    they also offer the same gear covered with a powdered white paint that gets
    baked on for a nice paintable white surface.  This one sells for $24.95.
    Assuming I am going to paint the gear to match the plane, this seems to
    be the way to go.   As a bonus, the aluminum gear weighs _less_ than
    the stock wire gear with fairing!! 
    
    They also sell the cowl and wheel pants in fiberglass.  For $80 they
    will sell you the entire set of cowl, pants, and painted landing gear, 
    and that includes shipping.  
    
    I think I will spring for the entire set as I've worked with the
    plastic parts that come in kits and can't say its an enjoyable
    experience.  I'd much rather use the very best materials on this bird
    so it gives maximum performance and length of service.
    
    The wing is done except for the aileron servos.  Once these are
    installed its on to the fuse.  Very nice kit!
    
    Regards,
    Joe

    Joe,
    
    I did use two servos for the elevator and alierons.  Much stronger design.
    I just couldn't see using 1 servo with a bird this size.  If yours
    turns out anything like mine, it will need absolutely 0 trim
    adjustment.  The plane will basically fly itself.  You might want to
    toe-in the wheels to help slow it while on the ground.  Mine loves to
    run off the end of the runway.  Hopes this helps.
    
    John
    

    I have a general question for the masses.  What can cause an airplane
    like the Extra to "snap roll" when full up is applied?  Alignment has
    been checked and is true. Incidence is also correct.  Balance is on the
    nose side and left/right.  I've even checked for difference in deflection 
    of both sides of the elevator.  It happens at anything over half
    throttle and is made worse the faster you go.  Lessening the throws
    helps stop the problem but naturally lessens it's sensitivity.  How it
    occurs is when your flying (up,down, or level) straight then hit full
    up.  The plane attempts to comply then falls off and rolls to the
    right.  It appears that the plane is literally stalling the wing and
    your attempting to fly with the elevator and rudder.  Doing loops while
    increasing the elevator slowly to max will end up giving a multi sided
    circle.  Kinda interesting looking though.  Since the air is pretty
    thin at 7200', stalling the wing does seem possible.  If this is the
    case, why isn't the elevator stalling also?
    
    Any help will be appreciated.
    
    John 

    I was talking a couple of weeks ago to Bob Sliff, owner of Hobby Horn
    and he described a similar condition which occurred during the
    testing of the team USA F3E ships.
    
    To test the strength of the wings they dive the ships at very high
    speed and pullout violently.  The result of this test was what
    Bob described as a "high speed stall"  which sounds like what you 
    are experiencing.
    
    I know from looking at airfoil polars that all airfoils only
    generate lift up to a certain angle of attack.  After this
    point the wing stalls.  If the motor generates enough thrust
    you can climb indefinitely, otherwise you will reach a point where
    the wing stalls and drops a tip.
    
    
                                                       Regards,
    
                                                       JIm
    

    You are probably getting the wing to the critical angle of attack at
    which it stalls!  There can be a few other things that exacerbate this
    problem.  For example if you have a bit of twist (washout) in the wing 
    toward the tip it may stall sooner than normal.  An aft CG can cause
    the same problem.  You may also have an incidence problem where the
    wing is already at a positive angle of attack during level flight (did
    you have to trim down to make if fly level?).  If all of these things
    prove not to be the problem try drooping the ailerons a couple of
    degrees.
    
    Will

    correction .22 thats wash in not wash out!
    

    Your experiencing a high speed stall. Wings don't have to be going
    slow to stall. The problem is too much elevator throw. Turn it down.
    You can control responsiveness with your rate switches but decrease
    the amount of travel on the elevator to stop the unexpected snaps.

    Linked flaps, often called flaperons, can relieve the high speed stall
    problem up to a point.
    
    E.

    CG too far back and too much elevator cause undesired snap rolls upon
    application of full elevator.  Turn you elevator low rate down until
    you cannot snap it with full up and use high rate to do snaps and
    spins. (If you want to do them)  As Steve said, a Snap Roll is a high
    speed stall or a horizontal spin.
    	This type of plane is designed to be fairly low stability to do
    wild aerobatics.  They are usually set up with the CG back as far as
    possible and still be controlable.  This increases the likelyhood of
    stalls and snaps.  They will be more abrupt and it is easy to have them
    cause a crash.  If you don't like this, move the CG forward somewhat.
    
    Charlie
    

    I would add that you can do a snap roll without higher rated elevator
    throws because the rudder and ailerons are also applied for that
    maneuver.
    
    I tune all my planes to NOT snap on full elevator. I then drop the
    throttle just before entering the snap roll and use a boot load of
    rudder and full aileron.
    
    Running with too much elevator will get you sooner or later. The best
    thing to do is test high!.
    
    E2.

    Thanks for the replies.  Turning down the throws is exactly how I cured
    the problem.  Now if the operator could get alittle more stick time,
    things might look better.
    
    John

    Re: last few discussing snap with elevator
    
    I'v had about 35 flights on my Extra, and have never experienced any
    tendency to snap with heavy application of elevator.  I set the throws
    exactly per the manual, and ballanced mine a tad nose heavy.  It has
    always flown on rails, tracking rock solid, but when I call for a
    maneuver, it responds instantly and precisely with no slop.  WHen I say
    I'v never had it snap when applying hard elevator, I can't be sure I'v
    ever given it FULL up, so I will have to try this next time out.
    
    One of the things that has given me some extra tension when flying this
    bird is that it is so slippery that it just won't slow down, and lands
    _very_ hot.  Especially at the Merrimack field where you have to dive
    into the field over some high trees.  Elsewhere, I discussed this
    issue, and it was suggested I try to use flapperons to slow it down.  I
    tried flaps, but it didn't seem to have any effect.  Strange, I
    thought.  So since the flap knob allowed for the ailerons to be
    positioned both down (ie, flap mode), and up (spoiler mode), I tried
    the spoilers.  Lo and behold, it did what I wanted.  When the spoilers
    are deployed, the nose tilts up nicely, causing a higher angle of
    attack.  I crank in a few clicks of down to keep it from blooming, and
    it slows down beautifully.  In fact, I have to add a click or two of
    power to keep the speed above stall, and in this configuration, I can
    dive into the field without picking up speed, and it lands much better.
    
    I'm sure glad I built this with one servo per aileron, as it allows
    this kind of programming to achieve better overall performance.  Yes,
    and the JR X347 helps too.
    
    I also got the smoker working last week, and it was a real gas tearing
    up the sky and leaving a smoke trail.  Am I having fun yet? 
    Grown men shouldn't be allowed to have this much fun!  Actually, I think 
    its just the early arrival of second childhood. 8^}   
                                  
    -Joe