tendency to spring back to neutral

I did not want to change the subject on the other thread. But after reading it I got to thinking.
I did my first set of monokote hinges on two new planes.
The one set is on a skyray and they seem to work with no binding, and will stay just about where I put them. On a little Spitfire, they have a "tendency to spring back to neutral". No binding just springs back.
Will this be a problem?
Thanks
Paul

LAST EDITED ON Aug-08-04 AT 08:06 PM (CDT)
 
The hinge's are probably in a bind. Are they CA hinge's?

No sparky as stated in his message he is trying to make monokote hinges

Paul try using a heat gun while working the hinges by hand. see if you an stretch them just a little.

Roger
Thanks Tom!
I will give it a try tonight.

Paul

Everything I've built, except the latest plane on the building board, has used monokote hinges. All have had some degree of spring back or rebound in the hinges, especially when new. After 50 flights or so the hinges relax a bit and the rebound is reduced. I used to take pains to be careful not to use heat right where the hinge goes through the hingeline itself, thinking excessive shrinkage there would pull the hinges too tight and result in the rebound condition, but I gave up on that. Trying to keep a little bit of slack in the hinge causes the flap or elevator to migrate aft of the TE of the flight surface, causing a large gap in the surfaces at the hingeline. Although monokote hinges seal the entire hingeline so the gap is not visible, it puts strain on the flap bushing because the flap bushings, glued into the wing TE, cannot migrate back with the surface and take up excessive loads. Also, if you have one hinge tighter than the rest, that hinge will take up too much load and break.

But overall, its been effective on a number of airplanes, and I don't think the rebound is detrimental. The rebound force, in my opinion, is not great enough to deflect the surfaces in flight. In the last year, my planes with monokote hinges have garnered 2 thirds, 2 seconds and three wins in Advanced, so they fly pretty good with those hinges.

This is the problem I've had. I've done monokote hinges before and not had this problem but recently I have had this same condition occur repeatedly. I've covered and rehinged this stab-elevator combo three times and every time the same thing.
I've finally come to the conclusion that it is the way I'm doing the hinges.

I put the one side of the hinge on the surface and cut it off about an 1/8 of an inch over the surface. I then flip the monokote over and stick it into the gap between the surface and the monokote I just applied and iron it down over the edge. The hinge bends aroud the trailing edge and everything works fine til I start to finish the hinges up. I pin the two surfaces next to each other allowing for any misalignment from sanding the surfaces round, etc. Then I push the hinge down with the iron fom the hinge line out. One the one side is done I flip it over and do the other side the same way and when I'm finished the hinge line is sealed and the hinges are neat but they are stiff and spring back to neutral - attempts to loosen the hinges with the iron have failed so far. I've used settings on the iron from 1 to 2 and the temp doesn't seem to make a difference.

I'm going to try and just iron the hinges together separately and use it that way - this is more of a pain but if it produces a flexible hinge then I'll just have to live with the extra work

Would it be better to hinge the surface with a covering without glue on it, like micafilm, and then apply balsarite to the wood and iron it down that way? This would leave only a single ply of material in the hinge line - Possible you could do regular silk or cloth hinges the same way.

Has anyone tried this yet?

>I did not want to change the subject on the other thread.
>But after reading it I got to thinking.
>I did my first set of monokote hinges on two new planes.
>The one set is on a skyray and they seem to work with no
>binding, and will stay just about where I put them. On a
>little Spitfire, they have a "tendency to spring back to
>neutral". No binding just springs back.
>Will this be a problem?
>Thanks
>Paul
>
>I am a retread, - I did C/L in my youth and did not know
>what I was doing then other then having fun. And not much
>has changed.

Ron B.
F4Fguy

Paul:

If you used the method I drew on the plans,the problem is most likely to be too large a gap between the stab and elevator. This in turn makes the bonded area between the top and bottom pieces too wide and causes stiffness.The bond line needs to be ,essentially,a single line .010/.015 wide.
Also be careful not to stretch the material when ironing it in place,as this will cause it to pull to the tight side and not want to stay neutral.On the other hand,if you already have this condition,the heat gun technique mentioned by Tom may be worth a try.

Re the difficulty of "ironing" the hinge material together.

You've probably already thought of this but, rather than trying to iron the individual 1" wide hinges together it would be simpler to cut two strips of the moneykote a couple of feet long, tape the first strip glue side up to a flat surface then, very carefully align the second glue side down with the appropriate amount of overlap for the full length and tape in place. Iron together carefully and then simply cut off preattached hinges of the desired width.

>Re the difficulty of "ironing" the hinge material together.
>
>You've probably already thought of this but, rather than
>trying to iron the individual 1" wide hinges together it
>would be simpler to cut two strips of the moneykote a couple
>of feet long, tape the first strip glue side up to a flat
>surface then, very carefully align the second glue side down
>with the appropriate amount of overlap for the full length
>and tape in place. Iron together carefully and then simply
>cut off preattached hinges of the desired width.
>
>Ted

This is exactly what I do on mine. The monokote trim iron makes a convienent tool for attaching the glue/glue strip, and bonding the strips over glass means it does not stick to the work surface. Works quite easily, and the little trim iron set on high gives enough heat to join the strips, but not so much heat that it distorts the whole piece of material. Another useful fact is that even cold, the glue/glue interface of the two opposing strips will "tack" to each other in most cases, meaning you do not have to worry about the pieces moving as you attempt to iron the edges together.

By the time you've done everything, you have invested about as much time as if you did pinned hinges. You do have a sealed hingeline, though...

Ron B.
F4Fguy

Ted,and Steve:

Certainly the best way for over/under hinges.I don't believe this is what Paul's got(Paul???).The type I used on the 1/2A Spit for our Kid's Academy(the plan I sent Paul) was the iron on the top,fold back and iron on the bottom type. This is a lot easier for beginners to do.I've never had one fail,nor have I had a student who couldn't(some took a few tries)make a free hinge.1000 words attached:(the last two are demos of over/under type)

Ted,

I think that may have been what he was doing. I sent him a couple of the factory made tapes and one of them is pretty clear on how to do it. I know the first time I tried it they worked OK, for my son they didn't. May be that I was holding my mouth just right. My son was pretty good at it on subsequent applications. Could be that he just needs a little more practice. He also may be just trying too hard. Paul, if your reading this lighten up buddy.

Thanks Tom and Ron, and the rest of the gang.
I have tried a few times on the type that Ron sent. No luck. Now after looking at the pictures I do not think I had the crease ironed in right.
I re-watched the tape I got from Tom and I did it by taking the two strips like Ted suggested and cutting hinges and ironed on over under. I also did this same type on the Skyray. The Skyray seems fine but the Spitfire will move but springs back to neutral. I did it twice and the same thing. I will give it another shot tonight. Or may try the first type again that Ron shows in the pic.
I will keep ya'll posted.

Thanks
Paul

ps- Thanks Tom for the words of encourgement. I do not let it get to me too much. After all we are dealing with toy airplanes. We are still having fun.

>Re the difficulty of "ironing" the hinge material together.
>
>You've probably already thought of this but, rather than
>trying to iron the individual 1" wide hinges together it
>would be simpler to cut two strips of the moneykote a couple
>of feet long, tape the first strip glue side up to a flat
>surface then, very carefully align the second glue side down
>with the appropriate amount of overlap for the full length
>and tape in place. Iron together carefully and then simply
>cut off preattached hinges of the desired width.
>
>Ted

Ted's right as to technique, but he failed to mention that making hinge blank is so much easier if done on glass. MonoKote does not stick to glass.