BuzzBomber

My Feedback: (4)

Ok, so maybe it was too late to keep working and my brain was already asleep, but I really had a bear of a time sheeting the front center section on the LT-25 I'm building. The rear section was fine as it doesn't carry much radius, but the front kept popping up. I was laying the sheet down dry using titebond and spot tacking it with med. CA since that's all I had. I didn't want to pin the sheet down and risk splitting the ribs, so I had to hold it until the CA set. I finally got it done ok (its gonna need a little filler in spots ), but I was thinking, there's got to be a better way. Anyone care to enlighten me with what works best for them?

BillHarris

Use an aliphatic adhesive ("wood glue"). Tack down the sheeting at the LE with CA and work backwards. You can pin the sheeting down, or use "shot bags" (bags with lead shot) and weight the top down until the glue sets.

Another good adhesive to use on center and D-tube sheeting on a built-up wing is Probond Polyurethane glue. It foams up, fills gaps, makes a nice fillet and is flexible so that the joint can flex without failing.

beardking

My Feedback: (4)

Buzzbomber, what I did for my sheeting on my wing that I've been building for my RV-4 is put a coating of wood glue down on the curved surfaces and then I butted the sheeting up against the adjacent wood and then I taped the other end down and let it sit overnight. Worked perfectly for me.

SALMONBUG

My Feedback: (1)

what I do

1) cut sheeting to shape
2) apply wood glue on the rib and main spar
3) pin the sheeting to the leading edge
4) glue the sheeting to the leading edge using thin CA
5) witha wet sponge, I wet the sheeting applying slight pressure till it's on the ribs and main spare
6) pin the sheeting to the main spar (you may also want to pin it on some ribs)
7) weight and let dry overnight

et voila....

MinnFlyer

My Feedback: (4)

What I do is similar to all of these. I CA the sheet to the LE and wet the top, then add wood glue to the ribs, BUT leave about a 1/2" gap near the center. Then put a drop of Medium CA in all of those gaps, and CA the spar. Now, fold it over and I hold it down with a long level that I have (Anything long and straight will do) for about 30 seconds, and it's good to go.

Note* The only reason I use the wood glue is to give myself more working time, and to cut down on the expense of CA.

Al Stein

I do mine about the same way as SalmonBug except I don't use CA and I don't pin into spars.

I get the sheeting to shape, glue and pin the leading edge, apply glue to the rib tops and main spar, then use the sponge trick to get the sheeting to bend into place, and hold the trailing edge of the sheeting with weights.

When I don't seem to be getting the contact I want, I do uae pins into the ribs, but I use sewing pins instead of T-pins because the sewing pins are such fine wire and very rarely split wood, even dry 1/16" sheet.

BuzzBomber

My Feedback: (4)

Thanks for the replies everybody......it seems pretty obvious now. I'm still just trying to figure out how my CA tacking didn't work, but I'm definitely going to borrow some of your ideas for the rest of the sheeting. BTW, I have a bottle of Probond, but I've been afraid of the stuff because of its supposedly large amount of expansion. Is this true? Does it set/cure any quicker than Titebond (aliphatic)? Thanks again for the answers!

Crash90

My Feedback: (17)

Using a sponge to wet the balsa sheeting really helps.

Al Stein

I can give half the answer to the glue setting time question... I use Titebond II and it takes 20 minutess to have enough hold for me to handle the assembly or add more to it without supporting the joints. (It does get stronger over a period of hours, but the 20 minutes is what it takes til it holds.)

BuzzBomber

My Feedback: (4)

I guess I need to be more patient.

Al Stein

Patience can be an issue. It helps if you have room to work on one the fuselage or tail while the wing is setting.

Using a jig is also helpful if you don't like to wait before you can go on to the next step. I had a wing jig for a couple of years before I made myself use the thing, but I've used it often ever since.

With the wing structure supported on the jig rods, I can glue all kinds of parts onto one side, flip it over and do a bunch of the other side. For operations that normally need to dry so they won't be warped or distorted, there's no worry when the jig is holding the whole assembly straight.

In the time it takes for the upper leading edge sheeting glue to set, I can have the spars and trailing edge mounted to the underside and start on the lower sheeting. Then while the lower sheeting dries, I can be working on servo supports, wing tips, etc. from the top.

The jig I use is the old RCM version... I bought mine for two dollars even, but you can probably build one for not much more. It consists of a pair of 1/4" steel rods and a pair of supports that hold them aligned. Fast, straight wings every time... the only real investment was in building up the motivation to make myself use the thing the first time.

BillHarris

The Probond Polyurethane adhesive sets "overnight". The foaming is dependent on the amount of water available to the glue to react with (this water is in the air and the wood; sometimes you need to wet the wood) and the amount of glue.
Do a test piece to see how much the glue foams. It can and will push parts apart.

Dsegal

> 6) pin the sheeting to the main spar <

That sounds scary to me. I would not want to weaken the spars with pinholes.

Dave Segal

SALMONBUG

My Feedback: (1)

excuse me Dave but you are wrong, the toilet paper for exemple never crack at the position of the small holes

FLYBOY

My Feedback: (11)

I just use CA. Glue the leading edge like everyone said, then run thick ca down the ribs and bend it on and hold it. If you need to make it bend better, amonia works really well. I now have a cool tool that I put the balsa in and use a steamer and pre-bend all the wood. It is really slick.

BingoFlyer

I have used pins to hold LE sheeting to the main spar for 50 years and have never had a wing failure, even when getting into trouble and exerting more G force than I would have thought the wing could stand.

I also use a little ammonia with the water to make the sheeting bend easier.

Al Stein

I think that may not work because of how soft the balsa is... or it might. I know that I have had chunks of balsa torn rather than cut by a slip of a tool... as long as that doesn't happen, it may just be a good idea.

The fine sewing pins I've been using never seem to do any damage, so I've gone that way for the last couple years. If you try blunting the tips, I'd like to hear how it goes.

BuzzBomber

My Feedback: (4)

I've got enough different methods here to try a new one on every sheet for a few projects now, I think. Last night, I finished up the sheeting on this panel using the titebond with CA tacking at each end and the middle of each rib, and sandbagged it for about half an hour. Worked great! Going a little slower and actually thinking about what I was doing made a huge difference. Thanks guys!

MinnFlyer

My Feedback: (4)

Going slow is a good thing.

A VERY GOOD thing!

FLYBOY

My Feedback: (11)

I have also seen pins with a round platsic piece on them that will hold the balsa better without splitting it. Can't remember who makes them but I am sure tower will have them.

BuzzBomber

My Feedback: (4)

actually, I've got about a dozen of those......they come with shirts I buy at JC Penney. I like them better than the other pins I use because they're thinner AND easier to grab. I haven't had any splitting problems using them to build stick and tissue FF jobs. I'd bet they're cheaper at the sewing/craft store than the LHS too.

Al Stein

I think that what Flyboy's referring to was called pin clamps or something similar... it's a disk with a raised collar in the middle where the pin goes through. It lets a bunch of holding pressure be applied to the flat side of the balsa instead of the holding just being through the wood's friction against the pin.

I used to have some similar thingies that I made by punching a bunch of disks out of the lid of a "butter tub." I'd kinda forgotten about them...They did help a lot.

BuzzBomber

My Feedback: (4)

my bad. I have NOT seen those.