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Old Apr 24, 2012, 04:49 AM
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United Kingdom, England, Nantwich
Joined Jan 2012
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Replace foam "hinges" or not?

I wondered if its worth cutting out the foam-hinged control surfaces and using proper hinges? I figure its less demanding on the servos and maybe offers more response? Is it something that people normally do with a foamy?

If it is something that is recommended, should you use hinge tape (or something similar) to fill the gap between the wind and control surface to avoid a loss of lift?
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Old Apr 24, 2012, 06:47 AM
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Danny_l's Avatar
South Africa, WC, Cape Town
Joined Oct 2011
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Hi,
I have four different foam planes; Cessna 182, Sensei, T28 and P47.
They all have somewhere between 50 to 100 flights (each) and the hinges on any of them have never failed .
To be on the safe side I have put hinge tape on each surface, two strips on top and two on the bottom.
We often fly them in very strong winds, and have not had any problems.

I'd suggest you put the hinge tape on, it should be sufficient.

There's no need to block airflow between the control surface and the stabilizer /fin/ wing.
What is important is that when you apply the tape you should have the control surface deflected maximum to the oposite direction (when applying tape on the top of the elevator, the elevator should be max down) so that you do not end up with restricted throws.

What plane have you got?

Brgds,
Danny
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Old Apr 24, 2012, 06:50 AM
Stick, roger ball.
United States, TX, Rockwall
Joined Oct 2011
344 Posts
It depends...

Foamies with live hinges are typically set up that way to save weight. The live hinge is very light but sometimes not as durable as other hinges. Many foamies use hinge tape, welders glue, hot glue, or my personal favorite packing tape.

As far as using a constant hinge, it won't make much difference in lift. It will help reduce drag (a small consideration on most foamies) and it reduces control surface flutter. I always use a constant hinge because in aerobatic/3D flight the airflow between the wing and control surface seems to cause a lot of stress on the hinges and the pull apart.

If your plane has live hinges and they work, I would leave them alone until they start to crack, which may be never.
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Old Apr 24, 2012, 07:19 AM
Canadian Bacon
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Kingston, Canada
Joined Jun 2004
12,552 Posts
Some foamies have a lot of load on the foam hinges. What I do with those is to slit the from about 1/1/2 in. in from the tip to almost the centre of the wing. Leave another 1 1/2 in. at the middle of the wing, then do the same at the fuselage end of the ail., leaving another 1 1/2 in. at the inner end of the ail. In other words, you end up with three 1 1/2 hinges. This cuts down on the servo load drastically. Just for a test, unhook the servo from the surface and bend the servo to feel the load. Now slice the hinge and feel the difference. If my planes don't have these hinges, I use hotglue, and If I happen to break one of these foam hinges I repair it with hot glue.

Gord.
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Old Apr 24, 2012, 08:52 AM
Registered User
United States, NJ, Lodi
Joined Jan 2012
968 Posts
For hinges just use this when needed
http://www.rcfoam.com/product_info.p...a245c1490376f1

here is a video of how it is done:
Uhu-Por scharnier (1 min 12 sec)


"scharnier" is the german word for "hinge"

the phrase "ca. 5 minuten antrocknen lassen" means let the glue set for about 5 minutes
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Old Apr 24, 2012, 09:13 AM
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United States, FL, The Villages
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Blenderm
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Old Apr 25, 2012, 03:19 AM
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United Kingdom, England, Nantwich
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Thanks for all the advice guys!
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Old Apr 28, 2012, 04:16 AM
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New Zealand, Canterbury, Rolleston
Joined Oct 2011
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After ending up a tree the other day because an aileron horn came off due to the foam hinge loading and a while ago rehinging the elevator because of the stiffness causing horn glue failure (twice - I'm a slow learner...), personally I'd say a most definite YES to replacing all foam hinges.

Foam hinges are used because they are cheap to make and the manufacturer can get away with it.
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Old Apr 28, 2012, 04:56 AM
222 km/hr Parkjet flyer
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Latvia / UK visits
Joined Jan 2010
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i have no problem with foam hinges ..... my EDF has them - one aileron started to crack along the hinge line so hinge tape cured that. That was after many flights and rough use. She gets heaved around the sky proving the hinge system is fine.
My Parkjet has hit over 200kph with foam hinges ... no problem. I have added hinge tape under later as I intend to push even more speed.
My Cessna 182 Skyartec has foam hinged elevators / rudder - more than a year on - still great. But the hinge tape ailerons / flaps needed redoing and I used pinned hinges.

Foam hinges are fine. What people need to do when they first get the model is unclip the control rod from the surface and work the surface so the hinge frees up. They come out of mould stiff and just need that bit of help by hand to free-up. Once done - others posts about load on servos is solved.
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Old May 02, 2012, 05:12 AM
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New Zealand, Canterbury, Rolleston
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Just flown the Bixler today after fitting tape hinges (X type tape) to the ailerons. A totally different plane now, totally responsive, touch the stick and it responses. Note, not too responsive but rolls now look like they were meant.

Those X hinges - a length of masking tape sticky side to sticky side with an overlap as much as the thickness of the flying surface (wing, elevator or rudder). Cut the tape about 5 mm wide and stick one piece to the top surface of the (say) tailplane and the other end to the bottom of the elevator. Fit the next one the opposite way, top of elevator bottom of tailplane alongside it. Fit at least 6 of these. Same for the other moving surfaces.

There are other methods but this is easy to get material, simple, cheap and works. So free moving that the weight of the foam makes the surface hang down without the pushrods fitted.
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Old May 03, 2012, 02:38 AM
222 km/hr Parkjet flyer
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Quote:
Originally Posted by Mac50L View Post
Just flown the Bixler today after fitting tape hinges (X type tape) to the ailerons. A totally different plane now, totally responsive, touch the stick and it responses. Note, not too responsive but rolls now look like they were meant.

Those X hinges - a length of masking tape sticky side to sticky side with an overlap as much as the thickness of the flying surface (wing, elevator or rudder). Cut the tape about 5 mm wide and stick one piece to the top surface of the (say) tailplane and the other end to the bottom of the elevator. Fit the next one the opposite way, top of elevator bottom of tailplane alongside it. Fit at least 6 of these. Same for the other moving surfaces.

There are other methods but this is easy to get material, simple, cheap and works. So free moving that the weight of the foam makes the surface hang down without the pushrods fitted.
X hingeing takes me back to Control Line days ........... we used nylon covering cloth then. Cut a strip of cloth into short lengths. Apply to surfaces as you describe, use liquid glue, ie PVA, to soak through to fix to the surface. Some people used the same dope as to shrink / seal the covering.
Excellent way to do it BUT needed care to not have slack in the joint.

Back to foam hinges ... my foam hinges are such that elevators etc. fall under own weight - but that's because as I posted earlier - I work the hinge line by hand to free it up. Makes a big difference.

There's also the method of using the actual shrink covering ... and in the form of the Tex covering - can be used on large planes etc. with success. The beauty here is that once fixed - the shrinking process brings that hinge line RIGHT BANG in tight.
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