Sheeting foam cores
 

What's the best adhesive to use to stick 1/16 balsa wing skins to foam cores?, and whats the best glue to use to stick the balsa sheets together in the first place?

Sheeting foam cores
 

Elmers white glue for the wing joints. Used it for years.

Probond Ploy glue for the skinning. I have some stuff on my webpage about the skinning fo my Ricochet wing.

Using probond, if you just tape the seams together with a seamless joint there is really no reason to glue the sheets together. The probond will handle that for you. Works fine.

Sheeting foam cores
 

Thanks for the info, not sure if Probond Poly is available here in the UK - what sort of glue is it?, contact advise, PVA...... Please let me know, it might be sold under a different name here.

Stuart

Sheeting foam cores
 

Probond is a polyurethane glue that is activated by moisture and expands to several times its original volume. Under pressure, as in the wing cradle, it will expand into the foam and make a very strong bond. It fills gaps well, but do not let it escape, it sands terribly. There are several brands available around here. I remember seeing somewhere else that in the UK it may be sold as Excel glue or Gorilla glue (gorilla is also available in the states.
Try a google search, you should get a few hits.

Sheeting foam cores
 

Mike

Thanks for that.

Sheeting foam cores
 

Whatever you do, do not use 3M #77 spray adhesive. I am repairing the right inner wing panel of a G&P P38 that I bought at Bomber field in September. I discovered a soft spot under the sheeting and pulled off the sheeting to discover a melted area the size of a grapefruit. Yep the guy who started this plane used 3M #77, and it ate the foam. I never liked 3M #77 for sheeting wings, but I also never heard of it eating foam, that is until I read about it in this forum. Seems the new formula has a foam eating solvent in it, I could still smell it.

Vince

Sheeting foam cores
 

I agree with Vince about 3M-77 ,a lots of problem with this product the skin on my Zero started separating after a year. On the next plane I used Southern's Sorghum with great results here is link to give you some idea's

http://www.eam.net/DBROWN/bldsupplies.htm

If you decide to use S. sorghum make sure to seal the inside part of the skin with Balsarite or equivalent first otherwise a lots of sorghum will be absorbed by balsa.
the only disadvantage of sorghum is once the skin touches the core it is an instant bond and there is no moving around so measure and plan ahead. Good product. Next I have also used epoxy and it worked OK but the it is heavier than all methods

Sheeting foam cores
 

In the olden days I used sourgum contact cement with really good results. It was cheap to get and lasted for ever on the shelf. Now I can not find it any more so I have used 3M-77(old), epoxy, alphetic resin powder you mix mith water, latex contact cement.

For the cost the latex wins hands down. It holds like crazy, does not soften in the heat, does not get brittle in the cold, does not eat foam, semi flexable so it bends a little instead of breaking. I picked up a quart for $8.00 at an apoulstery store. It does have a smell of amonia, but it goes away after ten minutes.

Gorillia glue works very well. Do not get ANY of it on the balsa. It does not sand woth beans. This also goes for the alphetic resin glue. It cures so hard it is not easy to sand. THe only problem I had with the OLD formula of 3M-77 was on real hot days the skins could begin lifting.

My opinion.

Dru.

Sheeting foam cores
 

I use thick CA to glue the skins together,then Z-poxy finishing resin,polyurethane glue,or slow epoxy in that order is my favorite glue,white or yellow glue works also.What ever glue you choose,use very little,after smearing the glue on the foam I then take a putty knife and remove the excess

Sheeting foam cores
 

I used to use 3M 77, but after trying Pro Bond Polyurethane I'll never go back.

Sheeting foam cores
 

I use Foam Bond contact cement when I build my NWHT (all foam) planes. Works great, and I will not go to any other method to sheet foam after trying this method.

Sheeting foam cores
 

Stuart,

May be worth experimenting with 'Copydex' to stick balsa to foam.

Use it as a contact adhesive, ie coat both sides and let it dry clear, be warned as soon as you touch the two parts together, instand bond, no second chances!

Simon.

Sheeting foam cores
 

Simon

Thanks for that, I'll give it a go.

Stuart

Sheeting foam cores
 

I use 3M transfer tape. Cover the entire surface with it, peel that backing and put on the sheeting. 3M 77 spray works well, just make sure you wear a good mask. That stuff is really bad for you. Very high cancer causing. For putting sheets together, I get cheap electrical tape at the outlet store, tape 2 sheets together on the seam, bend it back and put thick CA in the joint, then wipe the other side with a paper towel. Sand lightly as the glue is drying and the dust will fill the rest of any crack. Take the tape off and sand that side lightly and the crack there will be filled as well. You get nice smooth sheeting that way. Be carefull not to sand too much thinning the sheeting too much.

Sheeting foam cores
 

If you tape the skins together and let the probond hold it together, can the probond be sanded if any leaks out? How soft is it after it cures?

ML

Sheeting foam cores
 

Hi ml3456,poly is easier to sand than epoxy,the best way is as it goes through the cracks,wipe it off with a damp rag of water.

Sheeting foam cores
 

Thanks John,

Does it sand better than carpenters glue?

Mark

Sheeting foam cores
 

I think so,I love it on foam wings,try some on some scrap,after smearing it on remove as much as possible,the stuff really swells.

Sheeting foam cores
 

I do as the above poster mentioned,
Tape the sheets together, weigh it all down
Let them cure for 24-48 hrs, remove from shucks, remove tape from seems, The leakage through the seams is very small, and sands off nicely.

I think the trick to the small amount of probond seeping through the seams, is having a very tight fit to begin with. Edge sand all your sheets perfectly straight, and you will have no problems

Sheeting foam cores
 

I can't imagine trusting a wing, or plane for that matter to 3M double sided tape.

I just repaired a foam wing on a G&P Sales P38 that was sheeted with 3M #77. The adhesive softened and attacked the foam under the sheeting. I pulled the sheeting off the foam, and it came off real easy. The foam core underneath was so damaged that I could not use it and had to cut another core. I sheeted the new core with Gorilla glue (polyurethane). This was my first experience using this glue to sheet wings. All I can say is WOW, this stuff is perfect for sheeting. It grabs like nothing I have ever used to sheet wings with, and that includes 3M #77, Sorghum, and Epoxy.

Yes, it's messier than contact spray adhesive, but no more than epoxy. Epoxy cannot match the holding power of this stuff. I misted the back side of the skin with water, then spread a thin film of Gorilla glue on the core. Laid the skin on the core and weighted it down. Went back an hour later and a small amount had foamed out the leading edge, trailing edge, and tip. On the tip I can see where the glue migrated about 1/32" to 1/8" into the foam as it expanded. When cured it sands easier than epoxy and flares nicely in to the balsa. The grip is tenacious, far better than anything I have used. I will never go back to contact adhesive, or epoxy.

Epoxy is still a viable alternative IMO, but it can't compare with Gorilla glue for grip, or price.

Vince

Sheeting foam cores
 

Vince and others,

Thanks for your advice. I am doing my first sheeting, and edge gluing seems like a real pain to get correct.

If this glue leaks a little bit on the tape seam does it bond th tape or tape adhesive to the thin balsa making it hard to remove?? Tight edge seam will help here.

Mark

Sheeting foam cores
 

Hi all,

Will the expansion of the poly glues (Probond, Gorilla, etc) tend to lift the sheeting of a non-bagged wing? In that regard, to compress the cores how much weight should be applied per square foot of wing area? (or square meter, for those using that irrational base-10 metric system :D )

Probond
 

Probond is put out by Elmers Glue. The nice thing about it like has been said is that expands and fills the seam of the sheeting so you dont have to glue it together first. As for sanding it sand very easily the nice part about it is it sands about the same as the balsa does thus you dont end up grooving balsa like you would if it were normal white glue, epoxy, or CA


Joe

Sheeting foam cores
 

Hey wildblue check this site on use of probond. wwwedge540.com. I used probond the first and last time the same day for skinning. Its alot of work getting the leading and trailing edges tite to the core. Takes about 300 lbs on a 35% wing also,still the edges are difficult for me. I bought a vacuum bag outfit and this is very easy to use. At about 6ins.of vacuum the skins are tight all the way around the core. Did 4 wing half's for a 38% Ultimate, they all turned out perfect.

Sheeting foam cores
 

It will bond to the tape, but both sand away easily at about the same rate as balsa.

Vince