Bill Vargas

My Feedback: (5)

http://www.rcuniverse.com/showthread...01&forumid=111

Howdy, here's a little more info for those that might want to try out the skin Hinge thing,,, but just aren't quite sure.


Experiment and Test with a scrap peice of balsa, some cloth, a peice of mylar, some 5 min epoxy OR with the epoxy that you are going to be using for the actual skin hinges on your wing. Mix a small batch of epoxy,,, lay the cloth down on the balsa and apply the epoxy. Next is to place the plastic over the work and squeegy out the bubbles and excess. Wait for this to kick off, about 5-7 mins and then just peel away the plastic!

Next is to flip the balsa over and cut a small groove, about 3/16-1/4 wide, to expose the bottom side of the fiberglass.

And there you have it,,, a fiberglass skin hinge


BVV

Pathous

My Feedback: (12)

Is the groove cut in the balsa tapered or straight?

Pathous

Bill Vargas

My Feedback: (5)

On the test peice,,, it make no difference how the groove is cut.

On the wing, I cut straight down



BV

djlyon

Hi Bill
What weight cloth and have you ever tried polyester resin instead of epoxy
Denis

Bill Vargas

My Feedback: (5)

Hi Denis, been using 1.5 or 2oz cloth,,, polyester is to brittle and will crack :sunsmiley

BV

djlyon

Hi Bill
Why not a 1/16 or1/8 vs 3/16 or 1/4 groove. Does the smaller groove result in too small a bend radius on the epoxy glass hinge so that it breaks with enough flex cycles?
Denis

daven

My Feedback: (1)

Denis,

You are correct, a small gap puts too much stress on the hinge line, and it will crack. It will start with a nice white line, but they will fail eventually if the gap is too small. I use 3/8" on my ailerons, and 1/4" on my elevator halves.

Bill Vargas

My Feedback: (5)

Denis, Daven says it all in the above

But now your stuck with a Gap and the best way to cover that is with some Glider Hinge Gap Tape. Its about 3/4" wide,,, half of which has that stick'em stuff on it and the other half is without. Just cut to size, peel the backing off and apply it to the wing,,, the clear half covers the gap and rides the FWD LE of the aileron.

There's also another way to do Skin Hinges, as per Dave Norman's instructions,,, there're posted over there at the www.NMPRA.org site,,, check that out also


BV

Per_N

Bill & Daven
I have tried this method with my V-tail and my result was not good. The only thing i haven't done is to put some hinge tape to close the gap. My rudders flipping up and down wards to much. Any suggestion what i have done wrong.

Per

Bill Vargas

My Feedback: (5)

Per, is the plane experiencing "tail flutter" during flight? What kind of pushrods are going to the V tail? Check the servos for sloppy gears or a worn out servo arm,,, post a pic if you can so we can see what it is exactly your talking about


BV

daven

My Feedback: (1)

I would agree, I'm really not sure what your problem is Per.

Try and give us a little more info.....

Per_N

I post some pic so understand me, I have use 4-40 push rods and one layer of 2oz glass.
And as you can see, I did not mount these tail because of the flutter or what is called.

Per_N

This pic when I press a little down wards.

Per_N

This pic when I press a little up wards.

Any suggestions Bill?

Per_N

Some more info.
The gap is 6mm or 0,236 Inch

Per

Bill Vargas

My Feedback: (5)

Per, Good pics!

Add another coat of epoxy resin to the top surface only to fill in the weave of the fiberglass. I have a feeling you did not use enough or scraped off to much because I can see the pores of the weave in the fiberglass. By doing that should help to stiffen things up a bit and you should be Good To Go


BV

Per_N

I would give that a try but i don't think i have to little of epoxy resin. I have not use any mylar plastic to cover the glass when i put on the resin, so i think you will always see some of the pores anyway.
Have you or anyone else experience these kind of problem before?

When you grab the rudder you can move it up and down maybe 3-4mm each way.
I guess if i mount this and go fly with it, it will explode in air.

I can't understand how it should be possible to get this construction stiff, the only thing that is stopping the rudder from moving in this direction is some thin glass and a small TQ rod

Any help here would be nice.

Thank's

Per

PylonWorld

Another thing you can do is add some epoxy on the underside where the slot is. Not a lot, but maybe add a very little cabosil or microballoons and create a small fillet at the fiberglass and wood intersections. The filler would only be used so that the epoxy stays where you want it. Cabosil is more thixotropic and would be my choice.

I agree with Bill that you need a little more resin because the cloth provides the strength, and the amount of resin controls the stiffness. Try adding some resin on top first, and if that doesn't do it, try my suggestion.

kane

Per,

The method I use for skinned hinges is a little different. Instead of the big through hole, I bevel the bottom surface similar to using monokote hinges. The gap is needed on the bottom for the surface to move (approx 1/8" - 4 mm). The top gap is considerably smaller approx 1/32" - 1 mm. I use kevlar for my hinge material (caution: don't try to sand it or else you get the fuzzies). To do all of this I shape my balsa tail with the elevators attached as one piece. Then I use an Xacto knife to cut the "V" shape into the hinge line. My first cut is perpendicular to surface and the second is on an angle (use a straight edge). This is all done from the bottom side. After I remove the balsa piece just cut out, I turn the stab over and make a second cut just behind the first to widen the gap along the top surface. I do not cut the ends of the surface until after it is bagged.

My two cents,

Dan

Lastly, I do not put the torque rods that far into the surface. I only extend past the edge of the elevator approx 1.25". Does anyone else put their torque rods that far into the elevator? (it looks like the rod is approx 4 inches long)

Per_N

You are correct Dab, The Tq rod are 3-4 inches. I believe that is what bill use too.
You version of making this skinned hinges sounds that the result would be great but a little more difficult to make i think.

I post a link to my Quickie site, there are some pictures of how i building my Quickie. Unfortunately there are only Swedish text but the pictures would tell some.

http://user.tninet.se/~jqv326g/bygga_sq500.htm

Thanks for every advice.

Regards Per

Bill Vargas

My Feedback: (5)

Per, here's a pic of my V tail on my recently retired Racer,,, its the plane you see me holding on the left

Per_N

Thank's Bill
You're probably right. I should try that. I have a little more gap on mine closer to 6mm, But i should make a little smaller next time I think.

Cheers

Per

Per_N

You told me some time ago where you are buying that hinge gap tape you are using. Unfortunately I have lost that link. Can you take that once more please.

Per

Bill Vargas

My Feedback: (5)

Per, Try www.Hilaunch.com The Gap Seal part number is ww502 and comes in a 10 foot roll.


I just looked and it wasn t there,,, but thats the person who sells the Gap Seal tape,,, try giving him an email



BV

Per_N

Thank's Bill