Foam Wing Sheeting Adhesive?

Last time I sheeted a foam wing (several years ago) the glue of choice was the slowest cure Hobbypoxy. I was very fortunate to receive hands-on training from Scott Smith of AeroSmith Model Aviation. Scott was always a big advocate of the epoxy method - not 3M #77 spray contact cement.

Since Petit has discontinued the HobbyPoxy line, what's the current choice for a wing sheeting epoxy?

I'm really happy with System 3 resins. They are a local
formulator in the Seattle area. I use it in a vacuum bag
for epoxy/glass/carbon layups. Friends of mine
use west system with equal results. Whatever you choose,
make sure you are happy with the viscosity of the room temp
mix. Some people advocate thinning with alcohol to get the
viscosity they need, but I find that the alcohol flashing
thru the laminate causes really crummy mechanical properties
and pinholes. Your results may vary...........

Scott Correa

Polyurethane glue is superior to epoxy in every way.

Lighter, faster, easier, superior bond. I recommend Titebond.

>Polyurethane glue is superior to epoxy
>in every way.
>
>Lighter, faster, easier, superior bond.
>I recommend Titebond.

Any glue can be heavy if too much is applied. If you use the "squeegee" method with the epoxy, you shouldn't gain more than half an ounce on the whole wing. Speed is dependent on the cure rate. Use slow cure to give yourself time to work and let it cure overnight in the cradles. I have difficulty thinking anything is stronger than epoxy. But strength is not an issue so long as it holds (which is a problem sometimes with pressure sensitive glues. Heat sometimes causes them to separate). Easier? See, now you have me curious. Would you lay out your procedure for sheeting a wing with polyurethane glue, and why you feel it is lighter, faster, easier, etc..??

(Once you start these things, you have got to keep going.)

Leonard Neumann

I use the poly-u glue exclusively. It is superior not only in the weight savings but also in the bonding. Poly-u glue foams up and thus fills the gaps in the beads of foam and the grain of the wood. If you are in a dry climate you may need to spritz a little water on the core before you lay the sheeting down since water is the caltyst that causes the foaming action. The method I use is:

1. Prepare the sheeting, top and bottom, by sanding smoothe both sides and cutting to shape with 1/4 in overlap on all edges.
2. Put cheap masking tape strips every two inches along the LE and TE of either the top or bottom sheet. (this step can be skipped if you are going to bag it)
3. Spread the poly-u glue on the sheeting using a plastic trowel. Mine has 1/32 v notches cut into it but I am told you don't need them. DO NOT LEAVE EXCESS GLUE ON THE SHEETING!!! This stuff FOAMS up.
4. Spritz a little water on the foam core (both sides) using an old hairspray bottle. A very fine mist is plenty. If you are in a humid environment the humidity in the air is plenty.
5. Place the sheeting on the top and bottom of the core and center them.
6. Tape the LE and TE together and place in the cradles then weight it all down with heavy stuff. OR place the sheets and core in the bag taped in a place or two to prevent shifting, and suck it down.
7. Allow to dry for a few hours. I am told you don't need that much time for curing but I don't like to take chances.

This works for me every time. Andy Patterson used this method on the inboard wing of his SV and epoxy on the outboard and he said that the weight difference was significant. I have used 3M 77, epoxy, and wood glue and the poly-u is so much better than any of those in my book.

Good luck with trying this stuff, Hope I helped. Ed

As Ed Culver stated, I tried both epoxy (30 Min) and Titebond on my SV22 wings. The inboard wing was done with Titebond and the outboard with Epoxy. The outboard wing was 1/4 oz heavier and the wing is shorter than the inboard. I will use only Titebond from now on when I sheet my wings. Have fun, BAD ANDY

OK you've got me curious now.

I've always used epoxy. And always managed to build light models that way.

This titebond, exactly what is it? I need to be able to find a local equivalent here in Aus. I'm interested to experiment with it.

>OK you've got me curious now.
>
>
>I've always used epoxy. And always
>managed to build light models
>that way.
>
>This titebond, exactly what is it?
> I need to be
>able to find a local
>equivalent here in Aus. I'm
>interested to experiment with it.
OK. Here you go.

I have been using the Titebond Polyurethane Glue for sheeting foam wings (polyurethane glue was recommended for this application on RCOnline). It is the same resin type I used at Findlay Industries to make headliners and door panels for automobiles. It is absolutely the BEST glue for sheeting foam ever invented. It is superior to epoxy in every way-convenience, effectiveness, weight, and speed.

Doug Moon was trying to find the Titebond (Titebond 800-347-4583). The manufacturer is Franklin International. Here it is for sale on the web.

http://www.cheyennesales.com/catalog/glue.htm
and here
http://store.yahoo.com/toolsplus/t-b2303.html

Doug got the Elmer's version and it is definitely different. It did not expand as much as the Titebond and appeared much thicker. The Titebond is very thin and expands like mad, perfect for sheeting foam.

Thanks, whoever recommended it.

I squirted on too much glue right out of the bottle in an "S" pattern and troweled it around with a credit card until is began to turn yellow. The bulk of the glue was then pulled off the end of the skin onto a paper towel. Very little is required. (.1 oz by my tests).

I would not recommend leaving piles of glue, more glue expands more. The grooves in the card method would not be necessary.

Save the paper towel you troweled the extra glue onto. When the glue is hard on the towel (it will be hard as rock and will snap into pieces) your cores are done and can be taken out of the cradles. Mine took 45 minutes on a rainy day.

By the way, for a Time Machine wing I used .1 oz of glue per sheet (that's .2 oz per core and .4 oz per wing). From start to finish was 45 minutes, and the bond is THE BEST I have ever done.

My weight numbers for my new plane go like this.
Foam wing halve (Time Machine):
Core with spar = 2.2 OZ.
Balsa Sheet = .7 OZ wood, .9 OZ joined
Sheeting glue = .1 OZ per sheet
Core sheeted (no leading or trailing edges) = 4.2 OZ
With leading trailing edges added = 4.7 OZ
With Stiletto style wing tip built “Tom Morris” style (fully sheeted-very nice) = 5.0 OZ
3 coats of wiped Minwax Polycrylic (sanded between) = 5.2 OZ
Ultra light Jap tissue (one layer) and (4) coats of 50% nitrate clear dope (not sanded) gased off for one week= 6.2 OZ
Dope sanded flat and shiny = 5.8 OZ

Beat that...

I use Sorgums contact cement. There is enough in one bottle to do three full size wings. Just spread on with an old credit card. On he sheeting and the core. Let it dry for about 45 minutes and stick it together. I roll the foam core from the trailing edge forward. Once you stick the sheeting on it is on for good. There is no dry time after that. I have no peel up or troubles yet. Easy to use and the clean up is easy as can be. It just rolls off your fingers or your table. It works well. I would not use 3m77 it does bot last. I have tried two like this and both delaminated once it got outside in the sun.

Doug Moon

I just assembled my first polyurethane-adhesive vacuumbagged wing. I found it harder to spread than epoxy, and also found that the spreading difficulty could be sidestepped by putting on more than I needed and then squeegeeing it like crazy, just like epoxy. I haven't done an a/b comparison with epoxy for weight, but as earlier posts from other folks show, you can't save more than the half-ounce the epoxy weighs per panel described, but anything saved is to the good. I thought it cleaned-up much more easily, and it's really nice and sandable too. The vacuum bag keeps the foaming under control, and I found that overnight in the bag under vacuum worked out just fine.

The project that I experimented with was a r/c F4U Corsair wing, four foam panels, lots of joints, laminated block tips, embedded l/g torque blocks, all with the one polyurethane glue. The only limitation I saw was the short working time as compared to epoxy. The thinner epoxy is spread, the more working time. Exact opposite for this stuff. I did a test panel first, and I thought I had twenty minutes to get the cores into the bag before the glue started to set up.

Someone could enlighten me, too? The glue I used was "Elmer's", any different than the "Titebond" version, and if so, in what way? Thanks.

Peter Havriluk