Conference vmszoo::rc

    
    	Well, I think I've used every hinge you mentioned so to start
    things off.   
    
    Robart.  Pin hinges. didn't like drillng that hole and alignment
    was a problem.
    
    Iron on  Again alignment and they left a slight bulge in the covering.
    
    What I've been using is a this flat mylar/plastic type hinge from
    SIG. I wrote about it in another note. I'll try and find it.
    
    					Tom

    THANKS TOM. FRIEND FROM FLYING CLUB USED THE ROBART PINS AND LIKED
    THEM ALOT, HOWEVER USED DRILL PRESS FOR CUTTING HOLE ACCURATELY.
    BUT ADDED USE THE SMALLER PINS (THEY HAVE SEVERAL SIZES) BECAUSE
    THE JOINT IN THE MIDDLE OF THE LARGER PINS KEEP THE CONTROL SURFACES
    (FROM TE TO LE) TOO FAR APART, GET FLUTTER. EPOXY ON SMALLER PIN
    WORKES AND HOLDS JUST FINE.
    
    REGARDS,
    BOB G.  JERSEY COAST FLYING CLUB
    

    HOT STUFF HINGES--------------
    I have been using them for three years now. B-17, 60 size stiks,
    F1, scat cats, etc. Real easy to install and I've never had a
    failure. I usually install them ( with no CA ) prior to sanding.
    Sand everything smooooth and remove. Reinstall after covering
    using a little thin CA. When painting install prior to primer.
    
    Bob
     

    
    >because the joint in the middle of the larger pins keep the control
    >surfaces too far apart, get flutter.
    
    What I have done when using the larger Robart pins is the drill
    the hole for the pin, then go in with a larger drill to recess the
    hinge halfway into each edge. You can get an almost gapless joint
    this way.
    
    Dan 
    

    I too have used the Robart pins with total satisfaction.  The technique
    described by Dan Snow in .-1 works quite well.  To repair a rudder with
    a partially torn gapless hinge, I have used the Robart without rudder
    disassembly by routing the top of the rudder/fin to accept the hinge.
    The gap is nil.

    For the short length of a rudder hinge line, it would seem that the
    Robart could be installed such that future disassembly could be done
    by removing the metal pivot pins in the Robart "pins" just as if this
    were a household interior door.

    Alton, the repairman

I have  looked  through  all  the notes under "HINGES" in the directory, and
cound not find a detailed explanation about installing the ROBART hinge.

When you think about it superficially, you feel it is easy to drill the 1/8"
(or  whatever  dia) holes into the two surfaces being hinged, coat the hinge
ends with epoxy, and literally stick it in.

However, upon  deeper  cogitation  on  the  process,  I  came  up  with  the
following.

1. All  hinges  must  be  parallel to each other, perpendicular to the hinge
   line, and have their hinge pins co-axial.

2. 1 above also means that you have to insert the hinge to the same depth in
   each surface.

3. I  am  thinking  of rounding the leading edge of the moving surface (e.g.
   elevator),  and  sanding  a  concave  depression  into the t.e. of    the
   fixed surface (horizontal  stab/tail plane) to get a gap-less hinge/scale
   look.

Sooo, while  I  can  think  of  drilling  holes  using a drill press, etc..,
theoretically,  can someone with practical experience give enough details to
guide me through the in's and out's of using Robart hinges?

Of course, I am assuming that using these hinges is a good idea in the first
place :-)

And in  return  for transferring advanced aerospace technology from good ole
'merica, you'll have eternal third world gratitude. We might _even_ consider
not chopping down the rain forests so ya' all can continue driving the 2, 3,
4 or however many cars that you own. :-)

Yeeeeoooow! Time to duck 'n git out of yer' way...

ajai

ps. Perhaps  I should "practice" on a scrap piece to get the hang of things,
so I don't put my aircraft (yet to be built) in jeopardy?

    Ajai,
    
    First, yes, Robarts are a very good choice of hingeing systems, the
    best IMHO, and my preferred system for the past 8-10 years.
    
    Second, by all means practice on a piece or pieces of scrap to get the
    mechanics sorted out.
    
    Third, don't overcomplicate the installation by overanalyzing
    things...this is one of T.H.E. easiest of all hinges to install.
    
    The critical part (but not _that_ critical) is marking and drilling the
    holes.  DuBro, Golberg and others sell a little centering jig for
    locating the center of the surface.  Robart even sells a similar jig
    which includes a 1/8" drill guide.  Note that all thise gizmos work
    best/easiest BEFORE rounding/shaping the surfaces; I recommend locating
    and drilling the holes while the surfaces are nice, square-cornered
    flat-stock.  Personally, I drill the holes by hand, eyeballing the
    2-plane alignment of the drill bit and "feeling" with thumb and
    forefinger placed on either side of the surface as I slowly insert the
    drill...if I get off center, I can "feel" the bit and correct its path
    before it comes out the top or bottom of the surface.  If uncomfortable
    with this, by all means use a drill-press however, this isn't foolproof
    as the grain of the wood can sometimes divert the drill and cause it to 
    come through in spite of carefull jigging.  This, however, is not a
    reason to commit Hari-Kiri (or the Indian equivalent)...just recenter
    the drill and don't worry about the unwanted hole in the surface; you
    can fix it with filler later and it'll never show.
    
    I always drill the stabilizer first, then, with centerline already
    located, I mate up the elevator (rudder or aileron) _exactly_ where I
    want it and mark the hinge position with a pencil.  This exactly
    locates and centers the holes in the control surface(s).  Once holes 
    are all drilled, decide whether to attach the surfaces before or after 
    covering (after covering is usually preferred).  
    
    Slightly inletting the hinge into both the stab and control surface
    minimizes the resulting gap.  Just assure that you don't get things so
    tight as to limit/restrict a reasonable amount of smooth surface
    movement around neutral.
    
    Just before installing (any pinned) hinges, it's a good idea to try to
    protect the hinge pins from excess epoxy.  There are probably better
    methods and I'd like to hear of some that others are using but here's
    what I do.  Using a pan I'm not terribly fond of, I heat some water to
    a boil, then back off the heat enough to retain the heat but stop the
    bubbling...I want a smooth surface.  Now, I spoon in some Vaseline
    petroleum jelly and allow it to "skin" over the surface of the hot
    water fairly thickyl.  Now, one at a time, I fold the hinges double and
    dip the pinned portions into the melted jelly, then place them on a
    paper towel to drain and cool.  This provides a barrier to the epoxy
    but be careful not to handle the hinges too much prior to installation.
    
    Now for installation; again I start with the stabilizer.  I prefer 30-min
    epoxy as it allows plenty of working time.  Using a toothpick, I fill
    each hole with epoxy, then apply a thin film to the hinge itself and
    slowly insert the hinge into the hole, rotating it back and forth as I
    go to get maximum distribution of epoxy.  Much excess epoxy will be
    forced out of the hole and I just wipe it away with a Kleenex or
    whatever's handy.  Now, with all hinges in place, I simply fold them
    all 90-degrees and rotate them as required to assure that they're all
    perpendicular tp the horizontal center line of the surface and allow to
    cure.
    
    I test the leftover epoxy to determine that point when it "kicks" and
    begins to harden.  Before it gets rock-solid, I exercise all hinges to
    free them from the excess epoxy that may've gotten into the works...it
    _always_ does, regardless of the Vaseline treatment and other
    precautions taken but don't sweat it, exercising the hinges frees them,
    quickly.
    
    Now, simply extend the hinges straight out, mix some more epoxy and
    attach the control surface(s), repeating the steps above.  Again, as
    the epoxy cures, the hinges will stiffen up but exercising them will
    loosen things up pronto.  BTW, especially if yer' doing all this
    _after_ covering/finishing, cotton swabs and Isopropyl alcohol will
    clean up excess epoxy in jig time UNTIL IT CURES...be sure to do all
    yer' cleanup _before_ the epoxy kicks.
    
    That about does it...simple, eh?  Much easier, IMHO, that slotting, 
    aligning, etc. for conventional flat pinned and/or polypro hinges.
    
    And, finally, Sahib, how does cutting down the rain forests help to
    insure that we can drive our automobiles??  You got me scratchin' mi
    cabeza with that one.  :B^) 
						 __
				|      |        / |\	   	       
      	         \|/		|______|__(o/--/  | \	   	       
      | |        00	       <|  ~~~  ____ 04 ---- | --------------------
    |_|_|        (O>o		|\)____/___|\_____|_/	   Adios amigos, Al
      |     \__(O_\_	        |	  |___/	 o	   (The Desert Rat)

Hah! There are nooo secrets, sez Al, and proceeds to expound the intricacies
of hinging in _just_ 91 lines :-)

You see,  I  was turning over a "sample" Robart hinged control surface in my
mind,  when  I  saw room for potential problems. For instance, if the hinges
are not inserted to the same depth, the surface will just plain not move, or
if it  does, it will bow. Also, if the hinges are not inserted perpendicular
to the hinge line, again the surface will lock up. (The plastic hinges don't
fuss if inserted skewed.) Soooo, I decided to tap into the experience people
had, rather than learn by trial and error, and save myself some time.

Yeah, I  have  a  Goldberg  slotting  jig,  that has a hole in it for Robart
hinges.  I  had realised this while using it for the first time, and again a
few  days  prior  to  entering my query, but plain forgot all about it while
entering  the  note.  I  have  a  full set of "brass tube drill bits" that I
rounded  up  at  a  hobby store (for $17) specifically for drilling holes in
balsa, going up in increments of 1/32", that I could use. Drill bits are too
clumsy to  use  with  balsa,  and don't do a clean job in my opinion. 

Yes, I  too  would  do  the  drilling  while  the edges are still square and
pristine,  but nonetheless, a good point to note for some tired rc notesfile
wayfarer who decides to stop under the shady hinging tree for some rest!

Now, that  bit  about  baptising  the  hinges in Al's potion, is nothing but
undiluted  witchcraft.  (Wizardry  sounds  too  goody-goody,  and therefore,
inappropriate  for  use  in  this  notes  file :-) ) I would have thought of
hoping  and  praying  against hinge freeze-up, but _never_ the boil-and-dunk
routine. I knew there is more to it than meets the eye, and bay-bee, wuz ah'
right!

Wee bit  more  thinking  about  covering  that concave rear end of the fixed
surface  had  me  sweating  :-),  so I would like to sort this out on paper,
...err...  notes file. I could form the seam for the monokote on the top and
bottom sides  of  the  fixed  surface (e.g. stab) inside this depression. Me
thinks  having to cover a 1/4 circle (with the 2 pieces from top and bottom)
is easier  than a 1/2 circle. I imagine the concave/convex surfaces will not
pose any  additional  problem  to  the  epoxy  clean-up routine, unless I am
missing something.

>>    And, finally, Sahib, how does cutting down the rain forests help to
>>    insure that we can drive our automobiles??  You got me scratchin' mi
>>    cabeza with that one.  :B^) 

Me too, especially if you put it like that!

Dees ees vot ah' sed.

" ...We  might _even_ consider not chopping down the rain forests so ya' all
can continue driving ..."      ^^^

Mebbe yas missed out on da negation preceding da chop. You know vot ah' mean
-  dem  trees  help  soak up da carbon-dioxide dem cars put out so yas don't
melt  dis planet vit da greenhouse effect. Sumpin like dat, you know vot ah'
mean. S'pose yer cleer naow.

ajai

ps. Lest  I  am  accused of spreading disinformation, while rain forests are
found in third world countries, India has only a minor share.

Well, questions about hinge placement, and number of hinges to be used. What
are  good rules of thumb to follow in the regard? I'll post a sampler so you
know what I am talking about...

1. A hinge every 6".

2. A hinge at each tip of the hingeline for each surface.

3. A  hinge  under  the control horn (or conversely, locate the control horn
over  the hinge) to prevent surface flexing under load, and enhance positive
action.

4. At  least 3 hinges per movable surface, so that if 1 fails, you still got
two working  for  you,  and  the  surface continues to remain functional. In
practice, I would imagine that more than one has to fail for any to fail. Of
course,  a  hinge  pin  could  drop out on just one hinge, assuming a pinned
variety.

5. Is there some rule about # of hinges vs engine size?

Someone pse add/correct/approve what I have quickly typed in.

ajai (hinges-are-forever)

    Ajai,
    
    I use no fewer than 3 hinges per surface, sometimes 4.  It's hard to
    give an "every so many inches" dimension as it varies with the type
    surface, i.e. I like to have at least 3 hinges in the elevator even
    though this spaces them closer than needs be...on a taildragger, I like
    to use 4 hinges on the rudder cause it takes quite a beating and, again, 
    this spaces them even closer.  On ailerons, I'll usually settle for 3 hinges
    unless they get 6" or farther apart...then I'll use 4.  I always locate
    the outermost hinges near the ends of the surface, then center the
    remaining hinge(s) between these.
    
    I like to have a hinge fairly close to a control horn for the reasons
    you cite but don't require that the horn br right atop the hinge.  BTW,
    Robart makes what's called [and I'm not making this up] a "Horny Hinge-
    Point" which doubles as a hinge PLUS a built-in control horn...this
    might be something for you to try. It installs almost identically to Robart
    hinges.
    
    Again, I encourage you not to make too much of a science out of
    hinging.  Yes, it must be done to certain minimums but these are so
    easy to achieve as to warrant little deep study or expenditure of time;
    just install at least 3 hinges per surface, 4 if it makes you feel a
    bit more secure, and get on with it.
    
    Are you building the Wot-4 currently or just psyching up to get started?
				 		 __
				|      |        / |\	   	       
      	         \|/		|______|__(o/--/  | \	   	       
      | |        00	       <|  ~~~  ____ 04 ---- | --------------------
    |_|_|        (O>o		|\)____/___|\_____|_/	   Adios amigos, Al
      |     \__(O_\_	        |	  |___/	 o	   (The Desert Rat)

re a recent question about aileron hinging by Eric DWOVAX::BEHNKE 
   (The question and diagram are now located at Note 694.13)

>>  Lastly, when building Ailerons, is it typical to "relieve"
>>  the aileron so that there is a gap (on the bottom) when the
>>  aileron is in the "neutral" position? 

    In my experience, center line hinging and top surface hinging are both
    rather standard with center line being more common except in gliders. 
    Low speed gliders like the Gentle Lady (which doesn't have ailerons)
    and the Chuperosa (which may) use the covering as the hinge; their
    control surfaces are hinged at the top (or one side of the rudder). 
    Power planes tend to be faster, the forces on the control surfaces tend
    to be higher, and the hinges more sturdy, so mechanical hinges are more
    common.  Mechanical hinges _can_ be top hinged, but few people go to
    the trouble; center line hinging is the norm.

    For center line hinging the front of the aileron would look like:

    		]     or    >     or    )    not    /

    Alton the librarian and re-kitted plane re-builder

    Al,
    
    Once you drill out the 1/8" hole for the Robart hinge, do you adopt any
    special technique to increase the size of the opening to seat the bulge
    at the hinge point? Or do you just hack away with a knife?
    
    ajai

    
>>    Once you drill out the 1/8" hole for the Robart hinge, do you adopt any
>>    special technique to increase the size of the opening to seat the bulge
>>    at the hinge point? Or do you just hack away with a knife?

    I'm not sure which "Al" you refer to, but I'll answer.

    I like to get the gaps as tight as possible without being so tight as
    to cause _any_ binding, so I recess both Robarts and the pinned Dubro
    hinges.  I've recessed the Robarts two ways: by simply re-drilling the
    entrance of the hole with an appropriately larger drill and by using
    the Dremel ball-shaped cutter to open the hole.  It really is not
    critical.  [For the pinned hinges, called "butt hinges" when used in
    your household doors, I use a Dremel router for both slotting and
    recessing.]

    It is rather important to get the hinge axes identical --- neither offset
    nor askew.  The Robarts have enough slop to make this non-critical. 
    For the Dubro, the use of the router takes out all but two degrees of
    freedom --- depth of insertion and rotation in the slot.  I pull the
    hinge pins and put in a long wire through the entire set of hinges. 
    That, together with flexing the surface before the epoxy sets and some
    careful inspection, will align the hinge axes.  The result is a hinged
    surface that will respond to gravitational forces until the linkages
    are attached, i.e.   swinging freely.

    But all this doesn't really matter.  I crash planes for other reasons. 

    
    >                                                           I pull the
    > hinge pins and put in a long wire through the entire set of hinges. 
    > That, together with flexing the surface before the epoxy sets and some
    > careful inspection, will align the hinge axes.  The result is a hinged
    > surface that will respond to gravitational forces until the linkages
    > are attached, i.e.   swinging freely.
    
    Al,
    
    I like that - never thought of it before - clever one this.
    
    Question here about rudders that take the force of a tip over. The 'ol
    rudder takes a knock every time and starts sliding. I don't know what
    others do here to prevent this (on the occasional tip over) but I just 
    thought of adding some extra hinges to increase the strength. I never 
    had the problem on my HiBoy since the rudder was protected by the fixed 
    fin. My Acro-Wot has a rudder extending up over the end of the fixed fin 
    and hence takes the knock (just one todate - after an aborted take off). 
    
    Any suggestions from notes land ?
    
    A couple of diagrams ...
    
    Traditional tail
    
    force can be absorbed by fin on tip over
           FORCE
         | |   | |
         v v   v v
        .----..--.
        |    ||   \
        |    ||    \
        |    ||     \
        |    ||      \
        |    ||------------
        |    ||
        `----'`---------------------------------
    
    
    Force absorbed by rudder and tries to shift it down
    (diagram a bit exaggerated by virtue of VT340 character cell
    characters !)
    
         FORCE
         | | | 
         v v v 
    
       .-------.
       |        \
       |         \
       |          \
       |          |\
       |          ||\
       |          || \ 
       |          ||  \
       |          ||   \
       |          ||    \
       |          ||     \
       |          ||      \
       |          ||------------
       |          ||
       `----------'`---------------------------------
    
    
    
    	Regards,
    
    	Eric.

    Re: .-1, Eric,
    
    Yeah, you got'cherself a problem there alright.  Best thing I can think
    of is _don't_flip_it_over_.  :B^)  Seriously, I'm not sure there's
    anything you _can_ do short of redesigning/modifying the fin/rudder
    assembly.  Extra hinges will, of course, help but, if you flip over
    often enough, eventually you _will_ break the hinges.
						 __
				|      |        / |\	   	       
      	         \|/		|______|__(o/--/  | \	   	       
      | |        00	       <|  ~~~  ____ 04 ---- | --------------------
    |_|_|        (O>o		|\)____/___|\_____|_/	   Adios amigos, Al
      |     \__(O_\_	        |	  |___/	 o	   (The Desert Rat)

>    assembly.  Extra hinges will, of course, help but, if you flip over
>    often enough, eventually you _will_ break the hinges.

You won't break a SIG EZ hinge.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    Re: .-1, Kay,
    
    That's what I keep "hearing."  But we've several occasions where these
    hinges have failed simply from flight loads...no crash or abuse. 
    Personally, I don't trust 'em but that's just my opinion.
						 __
				|      |        / |\	   	       
      	         \|/		|______|__(o/--/  | \	   	       
      | |        00	       <|  ~~~  ____ 04 ---- | --------------------
    |_|_|        (O>o		|\)____/___|\_____|_/	   Adios amigos, Al
      |     \__(O_\_	        |	  |___/	 o	   (The Desert Rat)

My cut at the problem described in .14: If you can't stop the flipping I'd
rather have the rudder and the hinges take the shock than the fin! The rudder is
much easier to replace in most cases than the fin. I have a problem with my
Panic also. If I miss the runway and land in what passes for grass at the local
field I flip over - period, no way to stop it. I've redesigned the tail feathers
and the fin/rudder are sort of similar to those on a Decathalon. Its now on its
third rudder due to flips that would surely have trashed the fin if not for the
"shock absorber" rudder. So my cut at the problem is *don't fix it*!


                   /-----------\
                  /             \   <-  Shock absorbing portion of rudder
                 /________       \
                 ________ |       \
                /        ||        |
               /         ||        |
              /   fin    || rudder |
             /           ||        |
            /            ||        |
           /             ||        |
--------------------------|        |
                          |        /
                          ---------

>    That's what I keep "hearing."  But we've several occasions where these
>    hinges have failed simply from flight loads...no crash or abuse. 
>    Personally, I don't trust 'em but that's just my opinion.

Please elaborate on this.  I've seen them pull out (tho they have taken
a generous amount of wood with them), and I have seen them become so
oil soaked that they fall out - but I've never ripped or broken one.

R U sure we are talking about the same hinge - it is the one that
looks like a little flat oblong piece of mylar but in reality it is sorta
clothish and white.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

	I think I might try the large hinges and see. Hhhmmm breaking
	them - could be tough I would say the rudder/fin would probably 
	give first - but the tip-over I had I broke one of the small plastic
	pinned hinges - a first. The large hinges are tough and would probably
	survive. What  I don't always do is glue 'em in. I, for the most part, 
	pin them. I know that it would be better if they were glued in but I 
	like the option of taking the control surfaces off for repair 
	recovering or whatever - without the problem of cutting them out.
	But thats why they are pinned - Hhhhmmmmm.

	One could put a slot across the rudder fin (at the hinge)- strengthen 
	the sides of the slot and glue a rod in the fin side. The rod would 
	attempt to limit the up/down travel of the rudder. Depending on the
	thickness of the rod wrt the rudder thickness one may only get this
	protection if the rudder is in center position. But it might work.
	Is it worth it for the odd tip over though ?

	Yes this needs a diagram.

	.---.
	|    \
	|     \
	|     |\
	|     ||\
	|     || \
	|     ||  \
	|    ===== \
	|     ||    \
	|     ||     \


	the ====== would be....


	Rudder would have a tight slot for bar.

     Rudder	|   |
		|   |   Fin
    .-----------'   |
    | XXXXXXXXXXXXXXXXXXXXXXXXX rod glued into fin
    `-----------.   |
                |   |
                |   |

		Hinge line





	Regards,

	Eric();
	

    Re: .19, Kay,
    
    Yup!  We're talking about the same hinge.  A friend of Chuck's and
    mutual flying buddy at Puckerbrush Int'l Airport tried them and they
    simply tore/broke at the hinge line.  Jim is _not_ the butcher Chuck
    tends to be so I feel confident he installed them correctly and did
    nothing that might've contributed to the demise but, after just a few
    flights, they'd failed.  I recall distinctly standing around the
    airplane muttering, "So much for so-called indestructable hinges!" 
    BTW, the hinges were installed in an old-timer Miss America which flew
    slow and graceful, never overstressing anything so go figger'.........
						 __
				|      |        / |\	   	       
      	         \|/		|______|__(o/--/  | \	   	       
      | |        00	       <|  ~~~  ____ 04 ---- | --------------------
    |_|_|        (O>o		|\)____/___|\_____|_/	   Adios amigos, Al
      |     \__(O_\_	        |	  |___/	 o	   (The Desert Rat)

    That's funny, I can concure with Kay on the hinge, though I have
    always used radio south pro hinges. I have used these on every plane
    I have built and have never seen a hinge failure. A couple of times
    I have experianced severe crashes where the result is that the hinge
    is intact, and the wood is ripped apart. 
    
    
    							Dave
    

    Good thing that next/unseen brought up this note as I was about
    ready to enter a note in 399.

    Over the weekend I tried the silicone hinge system outlined in an
    '89 issue of RC Soaring digest.
    The control surfaces are 27" long flaperons on a birch and maple
    veeneer sheeted foam wing.
    The l.e. of the flaperons and the t.e. of the wing were faced with
    balsa strips in the normal manner, I use wing trailing edge tapered
    stock to reduce shaping/sanding.
    The faces of the strips were coated with epoxy to provide a smooth
    hard surface for the silicon caulking to adhere to.
    The flaperons were taped in position with masking tape, with a ~
    3/32" gap. The masking tape was run across the bottom, full span
    of the flaperon.
    The tape was applied with enough slack so that it could be bowed
    upward in an inverted U shape into the "V" gap between the flaperon
    and wing.
    Looking at it from the top, you see the top of the masking tape,
    sticky side up, about 1\16" below the top surface of the flaperon/wing.
    
    Making sure that everything is taped securely, the control surface
    isn't bowed etc., run two strips of masking tape full length along
    each side of the ~ 3/32" gap, to keep the silicone off the wood.
    
    Now squeeze a bead of silicone caulking into the gap down the full
    span of the control surface. Press it into the gap and smooth it
    out with your finger. Use several light applications rather than
    one thick one. Get it as smooth, level and void free as possible
    then remove the masking on the upper surface and set the wing aside
    to cure overnight.
    
    The next day, carefully pull the U shaped piece of tape out of the
    gap on the lower surface. Pull slowly at a sharp angle and the cured
    silicon won't be disturbed.
    
    The results are amazing. A smooth completely sealed hinge line with
    the control suface "spring loaded" to the center position and about
    50 degrees of travel available in both directions before the tension
    puts a noticeable load on the servo. 
    
    This was my first attempt at slicon hinging and it came out a lot
    better than expected. A better job could be done using something
    thinner than masking tape, with perhaps a lower tack.
    It's easier than it sounds.
    
    Terry
    

This seemed like the right note to place this article from the usenet in.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

Article         4149
From: [email protected] (Akkana Peck)
Newsgroups: rec.models.rc
Subject: how to make a gapless Monokote hinge
Date: 19 Mar 91 18:39:17 GMT
Organization: Apple Computer Inc., Cupertino, CA
 
>I also use the Sig hinges,and also prefer the others made by ??Satellite City,
>or whoever.  These other brand's have a small slot in the center to aid
>the wicking of the thin CA into the balsa.
 
Lots of people seem to like these.  I've thought about using them --
they look like they'd be so easy to use -- but all of the CA hinges I've
seen have been extremely stiff -- fine for a large .40 or .60-sized plane,
but I hesitate to use them in the .10-sized planes I prefer, or in the
1/2A GLH (I use micro servos in all of these planes).  Am I being overly
paranoid in worrying about making the controls too stiff, given that
the servos have to be strong enough to resist the wind pressure against
the control surfaces anyway?  Are there CA hinges which are less stiff?
Or do we micro-pilots have to find some other hinge solution?
 
One solution I like, especially for the 1/2A's, is Monokote hinges.
Don't just Monokote over the top and bottom of the wing-to-hinge joint and
figure that will work as a hinge -- the result looks sloppy and will
eventually break.  Instead, use Monokote (or your favorite covering)
to make several individual hinges, thus:
 
Take a square of Monokote about twice as wide as you want the hinge to be
(about 1.5" should do for a small plane), and fold it in half with the
glue side out.  Now make a cut along the crease for about half the width
of the square.  Unfold the square, and make another crease in half of
the square (again, with glue side out).  Here's a picture:
 
	--------.-------
	|       .      |
	|   A   .  B   |
	|       .      |
	========.......|
	|              |
	|       C      |
	|              |
	----------------
"===" is the cut, "..."'s are creases.  Now you're ready to iron the hinge
on.  First, iron quadrant A onto, say, the top surface of the horizontal
stab (be careful not to iron on quadrant B at the same time by mistake).
Now fold along the A-B crease, so that the glue side is pointing up, and
iron section C to the bottom of the elevator.
 
Now you've made half of the monokote hinge.  If you play with it, you'll
find that it's not terribly strong and seems to want to pull out.  So to
prevent that, you make another hinge right next to the first one, as a
mirror of the first one, with C ironed along the bottom of the h. stab,
and A ironed onto the top of the elevator.  Now play with it, and you'll
see that you have a nice, solid hinge, with almost no resistance (good for
small planes), almost no gap (it's easy to set these up with zero gap),
no slotting or gluing, little weight and little expense.  Of course, you
use several of these hinges along the length of a control surface, just as
you would with any type of hinge.
 
The description sounds somewhat complicated, but it's not.  I'm a lousy
builder, but on my first try using Monokote hinges I made something that
had almost no gap and moved far more smoothly than any of the other types
of hinges I had tried in the past ...  They might not be strong enough for
a 60-sized pattern plane, but they're great for small ships.
 
	...Akkana

RE: Note 73.45 by KAY::FISHER
From: [email protected] (Akkana Peck)
Subject: how to make a gapless Monokote hinge

    This method seems WAY too complicated and likely to tear.  What I
    have done for each hinge is to cut 4 small pieces of MonoKote
    approx. 3/4" x 1/2".  Then take 2 of these and put them adhesive
    side together such that they overlap by about 1/4".  Crude picture:


            +------------+----+-------------+
            |  "A"       |    |    "B"      |
            |            | AB |             |
            | Glue side  |    | Glue side   |
            |   UP       |    |   DOWN      |
            |            |    |             |
            +------------+----+-------------+


    Both pieces, A and B are approx. 3/4" x 1/2" and overlap for 1/4" as
    indicated by region "AB".  In other words, lay the A part on the
    table with the adhesive up and lay the B part on top with the
    adhesive down then iron the 1/4" area where they overlap (AB above).
    Repeat above process for other 2 pieces.

    Now, iron on the A side to the bottom of the horizontal stab and the
    B side to the top of the elevator.  Alternate top/bottom for other
    half of hinge and place it next to the first half.  (A on top of
    horzontal stab, B on bottom of elevator.)  Again, use approx 3 to 6
    sets of these for each control surface.
    
                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

>    This method seems WAY too complicated and likely to tear.  What I
>    have done for each hinge is to cut 4 small pieces of MonoKote
>    approx. 3/4" x 1/2".  Then take 2 of these and put them adhesive
>    side together such that they overlap by about 1/4".  Crude picture:

I've also only done it your way Dan.  But frankly I was having trouble
picturing exactly what he did and I want to go home and cut a piece
of MonoKote up as per the instructions.  With just one you end up
with a really strange looking 1/2 hinge but perhaps with two interleaved?

Can anybody figure out what exactly this previous note is doing and
re-explain it so that I can figure it out without cutting up post-its
in my office?

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    Post-it notes don't help. I end up with flap B glue side up unless I
    cover it with half of C which then puts both hinges on the same side of
    the surface. I suppose that the normal surface covering will got over
    it but you still end up with three layers in the A/B/normal covering
    sandwich and the A/B layers have no glue to hold them to each other.
    Might be worthwhile to email Mr Peck directly for a clearer
    explanation.

    I tried cutting up post-its too. It works up to a point, but quadrant
    B is left hanging in the breeze, unattached to any surface. It's
    got me baffled. As Dan alludes, anytime you make a cut in a film
    covering, regardless of brand, you've introduced a point that will
    eventually rip through. 3M clear vinyl tape works for me, but I
    wasn't entirely convinced until I saw the local F3B gurus using
    it without failures.
    
    Terry

    Dan Miner's method works quite well.  I have examined it on an F3B type
    glider.  Not as nice as an arrow shaft hinge (The checkerboard shows
    through.), but strong, zero stiffness, and ultra light; I suspect the
    slop is comparable.

    But to make them, make all the hinges at once, not individually as Dan
    suggests.  The technique is documented in the Black Baron film
    instructions and in the February '91 issue of MAN, pages 57 and 86.
    To paraphrase those references and add a bit:

        Iron together two partially overlapping strips of film, adhesive
        face to adhesive face.  The width of a strip will become the size
        of a half hinge.  The overlap should be the thickness of the hinge
        joint or a bit less.  Then chop off individual hinges from this
        strip, so the length of the strip determines the number/width of
        hinges to be made.  Individual hinges are attached to the top of
        one surface and the bottom of the other, doing a "Z" bend in
        between.  Alternate [top and bottom] the hinges along the hinge
        line.  For a gapless hinge, put the individual hinges in close
        contact along the entire hinge line.  For a quickie, install them
        in sets of three at appropriate places.

    Moderator comment: I'm inclined to move this section to its own topic;
    there is a keyword, HINGES, that could point to one or two notes but
    not gracefully to these several entries.  I expect a few more entries;
    the slop aspect needs exploration and experience.

    I used to make cloth hinges this way back in my U-Control days.  I
    would add one more comment:  It's probably much easier to put all of
    the hinges on the stab first, then fold them alternately up and down,
    then add the elevator (control surface).  You can pull things nice and
    tight and not have to slip another hinge in.  Also, don't get the
    monokote too hot because it gets much more brittle.  Just get it hot
    enough to stick well.
    
    Charlie
    

    Cloth hinges for CL! That brings back memories - I used to use a ribbon
    that I cut to size. I guess the 1/2" wide ribbon for "tying" gifts
    ought to work just as well.
    
    All this is assuming folks take the cloth hinge route...
    
    ajai

    And if you decide on cloth hinges, the next logical step is to get
    some of the pre-packaged stuff such as Granite State R/C Products
    sells, which iron on just like film, but with a stronger adhesive,
    and eliminates all the measuring, sewing, cutting, etc.
    

Well, I've spent the last several nights putting silicone hinges on the Alcyone
and I've had lousy luck. I read Terry's note in here but couldn't find Kay's
notes about doing the Lovesong (I remember reading them when they happened). 
Here's what I'm doing and the problems I'm having.

First: I'm using clear silicone RTV for the hinge material. I'm about to switch
to the tube caulk stuff to see if that makes a difference.

Second: I'm using scotch tape for the seal. This is what Tyrie recommended and
his was the most recent explanation. It pulls off the monocoat real nice.

The problem I'm having is that the tape pulls the silicone out of the hingeline 
when I peel it off. I'm thinking that it's the RTV versus the tube caulk. I've 
let the stuff dry 24 then 36 hours in my two attempts and the RTV is definitely
dry. Trouble is it likes the tape as much as the plane and some sections pull 
free. The sections that have stuck have made wonderful hinges but I want an 
entire hinge not just a section here and there. The RTV was on the bench and 
was my own idea so I'll change that and try again.

    Jim,
    	I've used silicone for lots of applications and I've found that you
    have to do things just right to get good adhesion.  First, I would
    rough up the monokote surface with 400 sandpaper.  Wipe it with acetone
    before applying the silicone.  You could reduce the stick of the tape
    by applying it to a surface and peeling it off before applying it to
    the wing.  Use the good clear silicone boat calk (Spags has it) and
    make sure to wait plenty long for it to set.  The thicker the
    application, the longer it takes to set.  When removing the tape, peel
    it back on itself very slowly and it shouldn't tear the silicone.
    
    Charlie
    

    I've had better luck using masking tape. Scotch tape may be a little
    too sticky. As Charlie says, do something to reduce the stickiness
    before applying. I run my fingers over it a few times. If you can
    find the special low-stick type of masking tape, that's the best.
    
    Adhesion to the Monokote (oracover in my case) will probably be the 
    least of your worries, once the silicon is in place and well cured.
    I never noticed the slightest tendency to pull loose, and this in
    plenty of dusty, high alkaline content landings.
    
    Ironically I've replaced the silicon hinges on the Algebra and reverted
    to Graupner tape hinges because I wanted greater flaperon travel and
    the silicon hinges put a greater load on the servos the farther away
    from neutral the surface travels.
    
    Terry

Re: travel

I'd heard about the travel issues and figured I'd set the flap neutral to 45 
degrees since I had heard you could get 50 degrees each way. I'll probably sand
them slightly before the next attempt just to be safe.

I believe I was seeing changes in the hinge that were screwing up my neutral on
the flaps. My control rods are <6" and low slop and the S5102 servos return to 
center pretty well but the flaps would be offset at the beginning of each session
and I think it might be due to changes in the tape hinge due to temperature. 
Nothing to really indicate this but it has been driving me crazy and usually 
means that I waste a flight getting back into trim after recentering. Not good
if you need every round to count.