sheeting foam wings

[Matt Neumann]

I am going to be sheeting some foam wings this fall and since the last time I did that was in 2008 I am a little foggy on a couple of things.  What is the best epoxy to glue the sheeting on with?  I know of Z-poxy which has a working time of 20 minutes and I see some other stuff that Brodak sell which looks like the same stuff I can get at Hobby Lobby that has a 30 minute working time.  I like the extra working time.  I thought at one point there was some stuff that had a 45 minute working time.  But that was years ago.  What recommendations do you guys have?  I am in the process of taking inventory and seeing what I will need to get between now and building season.  I want to order stuff now so if it takes awhile to get I will have some time instead of ordering it at the last minute only to find out it is out of stock.  I am also looking for stuff that a normal guy can use.  Some of the really high tech stuff, which might be great, you need to be a scientist to use.

[Dave Harmon]

I've sheeted a bunch of foam wings over the years but mostly for Pattern airplanes....but the techniques are the same.
Some guys like the Gorilla glue that you use a paint roller to apply, then spray with water then put the sheets in place.
I know it works but I've never tried it.
I have always used standard model epoxy.

These days I use the BSI (Bob Smith) Slow Cure (yellow package).
I know that Hobby Town has it....and most every town has a Hobby Town.
Never looked for it at Hobby Lobby....I know you can get it at Amazon.
It is 30 minute cure but you should still be all set up and work quickly....spread it on the wood, not the foam.

Properly sheeting a foam wing can get much more involved with advanced techniques and equipment but this will get you going with a good job and not much more than a plastic spreader for the glue.
OKIEAIR has a good spreader formerly sold by SIG.
Get the glue there too.
One good thing about it is that it sands nicely....doesn't rubber up....I like it a lot.

[doug coursey]

IF YOU USE THE FOAMING GORILLA GUE YOU HAVE TO WEGHT IT DOWN BECAUSE IT EXPANDS A LOT

[Dave Harmon]

IF YOU USE THE FOAMING GORILLA GUE YOU HAVE TO WEGHT IT DOWN BECAUSE IT EXPANDS A LOT

True....but no matter what glue you use....you still have to weight it down a lot.

[Matt Neumann]

True....but no matter what glue you use....you still have to weight it down a lot.

I know about the weight it down part.  At least 100lbs preferably more.  I remember about scraping it off leaving ribbons of glue as well.  I just did not remember if there was a preferred glue that normal people use. 

[Dan McEntee]

  I would drop Bob Hunt a line and see if he has a tutorial on file for sheeting foam wings. Seeing as he has done a few in his time, I think it would be worth a read ! I think he would email that out on request. It has all the basics and such and I'm sure he can update things like glue and such. I think I got it from him once years ago but finding it may be an impossible effort. I do need to find it myself, as I have a couple of unfinished projects that will require it myself.
  Type at you later,
   Dan McEntee

[Dennis Toth]

Matt,
I agree with Dan a call to Bob Hunt will give you his method. The basic has been epoxy slow cure glue that is applied using the spread and scrap method. Some have given the sheeting a coat of clear on the glue side to reduce soaking in the epoxy. When you apply you want to scrap off as much as you can, it should look dry. Make sure the cores are smooth and dust free then apply the skins, tape to hold in place then put them back in the cradles and add weights.

Tom Dixon was doing them with foam safe CA by dribbling it in a random pattern over the skin then position and stick down then in the cradles and weight, there is a YouTube video on this method.

Best,   DennisT

[Howard Rush]

I have hundreds of pounds of this fluid stuff in my shop—even more just outside. I could pile up to 1,500 lb. of it on a wing, but 300 lb. is probably enough. That’s how much scrap iron Bob Hunt piles on his, as I remember.

[Perry Rose]

I have two slabs of marble one inch thick I sandwich the balsa/foam with. Matching holes are drilled around and 1/4-20 bolts with wing nuts to squeeze things together. Easy to put tons of pressure on things.

[Matt Neumann]

I had thought of borrowing a few batteries from work.  They are around 70lbs each.  Put a board across the top and 4 batteries, that should do it.

[Gerald Arana]

I had thought of borrowing a few batteries from work.  They are around 70lbs each.  Put a board across the top and 4 batteries, that should do it.

Personally, I use a vacuum bag. No need for weight! LOL! The air at sea level is 14 lbs.+/- something per sq. inch! I have an air bleed so I don't crush the foam....

Cheers, Jerry

[Jim Svitko]

I was using epoxy, after coating the adhesive side of the balsa skin with clear dope.  This reduced the amount of epoxy that soaks into the wood which adds unnecessary weight.

After a friend told me of the brown Gorilla glue, I finally used it.  Spread a thin layer with an old credit card.  A spritz of water to be sure, but in a humid environment, the water is probably not needed.

I have a flat building board, the wing building board that Tom Morris sold.  I put the wing on that building board after getting the cradles positioned and taped in place.  A 1/4 inch thick aluminum plate goes on the top cradle, then at least 125 lbs. of barbell plates.  This is working well for me so I stay with it.

[Istvan Travnik]

Yes,
In the 21st century, the vacuum bag is the way to go. Everywhere you can find a vacuum pump: take out from a crap refrigerator. And, the enlightening "tunnels" in the whitefoam shall be cut AFTER sheeting.
As I observed my sheeting friends, they used slow action, self-foaming polyurethane glue, activating with some water spraying on balsa sheet (I think in the States that is "Gorilla" brand).
Many, very nice and good quality wings they made, with double leading edge balsa spars for perfect half-elliptic shape.
By my side, I remain by "Bluefoam" techique, for 40+ years, but that is another story...
Istvan

[Howard Rush]

Personally, I use a vacuum bag. No need for weight! LOL! The air at sea level is 14 lbs.+/- something per sq. inch! I have an air bleed so I don't crush the foam....

Yup, we use air for weight. I’d think they would have air east of the Rockies, but, come to think of it, I don’t remember seeing air when I lived there.

[Russell Graves]

Matt, here is a video by Tom Dixon about sheeting foam wings. It has some really good information.

[Brett Buck]

Yup, we use air for weight. I’d think they would have air east of the Rockies, but, come to think of it, I don’t remember seeing air when I lived there.

   How do you keep it at some reasonable vacuum?   I would think you would need a regulator of some sort, because 15 PSI seems far to much, even a junk refrigerator will pull a pretty decent vacuum.

     Brett

[Brett Buck]

I am going to be sheeting some foam wings this fall and since the last time I did that was in 2008 I am a little foggy on a couple of things.  What is the best epoxy to glue the sheeting on with?  I know of Z-poxy which has a working time of 20 minutes and I see some other stuff that Brodak sell which looks like the same stuff I can get at Hobby Lobby that has a 30 minute working time.  I like the extra working time.  I thought at one point there was some stuff that had a 45 minute working time.  But that was years ago.  What recommendations do you guys have?  I am in the process of taking inventory and seeing what I will need to get between now and building season.  I want to order stuff now so if it takes awhile to get I will have some time instead of ordering it at the last minute only to find out it is out of stock.  I am also looking for stuff that a normal guy can use.  Some of the really high tech stuff, which might be great, you need to be a scientist to use.

    I use EZ-Lam from Aerospace Composites, but unfortunately they no longer have modeler-size kits for it. Gone are the days you could call up former Junior National Champion Justin Sparr and get anything you wanted. When I run out of it, or it goes bad, I am back to guessing again.

    Brett

[Howard Rush]

   How do you keep it at some reasonable vacuum?   I would think you would need a regulator of some sort, because 15 PSI seems far to much, even a junk refrigerator will pull a pretty decent vacuum.

I use a “vacuum relief valve” from cstsales.com.  It’s just an adjustable, unregulated leak, but it works. One could probably use an old needle valve assembly.

[Howard Rush]

Maybe it does have some regulation, but I doubt it.

[Rusty]

I have planes with foam wings I built 25 years ago using this glue.  It is easy clean up and water based so it will not attack the foam.  Perfect after 25 years.  (Bridi Kaos)

I also have a large sea plane that I used carpet tape to put the sheeting on.  It is perfect after 30 years.  (Cunningham AHoy)

[Brett Buck]

I have planes with foam wings I built 25 years ago using this glue.  It is easy clean up and water based so it will not attack the foam.  Perfect after 25 years.  (Bridi Kaos)

I also have a large sea plane that I used carpet tape to put the sheeting on.  It is perfect after 30 years.  (Cunningham AHoy)

   That (and similar water-based products like Southern Sorghum from Dave Brown) definitely work. The problem is that they typically wind up  at least several ounces heavier - and sometimes much more.

   Epoxy is definitely the way to go, you have to use so little of it that the adhesive weight is nearly negligible. But you do need to press it into tight contact, either Matts 100+lbs ( I usually use 200 or more) or vacuum.

    Fun calculation - for a 300 square inch wing panel, 200 lbs is 2/3 PSI. A full vacuum is 15 psi. To get an equivalent pressure using weight alone you would need 4500 lbs- much more than most cars.

     That's why I was asking about a regulator, even a refrigerator compressor can pull down into fractions of a PSI, depending on what shape it might be in.

     Brett

[Brent Williams]

A repurposed $15 aquarium air pump will give around 6in of vacuum all day long.  Reverse the diaphragm and it makes a good little vac pump. 
I have a Tetra Whisper that works pretty well for 1lb white foam.

That is also in concept what ACP sold as the EZ-Vac.

[Gerald Arana]

   Epoxy is definitely the way to go, you have to use so little of it that the adhesive weight is nearly negligible. But you do need to press it into tight contact.........
     Brett
[/quote]

Brett; Have you done a vacuum job? When I was making competition glider wings, I never had to "press" anything. The epoxy will go into "all" the small spaces when the air is sucked out. I used an air leak system.

And yes, very little epoxy is used which makes a light wing. I haven't tried it on a CL ship and probably won't since I haven't been flying.............

Cheers, Jerry

PS: The first time I tore (read crashed) a wing apart I was surprised to see how the epoxy went everywhere.
PPS: I use "Safety Poxy" from aircraft spruce.

[Brett Buck]

Brett; Have you done a vacuum job?

   Not for a foam wing and not with equipment suitable for this. I do have an old refrigerator compressor from a different project.

     Brett

[Bob Hunt]

Sorry to be late to this party; had a bunch of things to do to get ready for my club's Electric Fun Fly this weekend.

I've covered a few foam wings in my life, and I've come up with a system that works for me. I did a tutorial several years ago on the subject and have discovered that someone posted it on the Internet without consulting me. That's okay, I'm getting used to that sort of thing...

Anyway,  here's the link to that tutorial. One caveat: The photos that show the Z-Poxy being spread on the balsa shows a lot more epoxy than is actually used. I had trouble with the photo showing the more minimal amount; it was almost imperceptible. So, I left more on just to clarify the spreading with the notched piece of plywood. As Brett has pointed out above, only a very small amount of epoxy need be used. And, as he pointed out, a lot of weight is the other key. I use upwards of 300 pounds of weight on the "sandwich."

Okay, here's the link: https://www.scribd.com/document/24384216/Bob-Hunt-Sheeting-Wing

Later - Bob Hunt

[Bob Hunt]

One more thing about that tutorial: It shows me using medium viscosity CA to join the skins. While that does work using the method shown, I have subsequently switched to using Titebond III glue to join the sheeting. I'll try to make some time to do a photo essay of how I do that and post it here soon. 

Later - Bob

[Brett Buck]

Sorry to be late to this party; had a bunch of things to do to get ready for my club's Electric Fun Fly this weekend.

I've covered a few foam wings in my life, and I've come up with a system that works for me. I did a tutorial several years ago on the subject and have discovered that someone posted it on the Internet without consulting me. That's okay, I'm getting used to that sort of thing...

Anyway,  here's the link to that tutorial. One caveat: The photos that show the Z-Poxy being spread on the balsa shows a lot more epoxy than is actually used. I had trouble with the photo showing the more minimal amount; it was almost imperceptible. So, I left more on just to clarify the spreading with the notched piece of plywood. As Brett has pointed out above, only a very small amount of epoxy need be used. And, as he pointed out, a lot of weight is the other key. I use upwards of 300 pounds of weight on the "sandwich."

    That is a very critical point - you want to spread around a fair bit of epoxy, then remove almost all of it by scraping it with a notched scraper (Signature Inn key card, etc). There is more-or-less no standing puddles or continuous lines of glue, it just looks like you got it damp. The total weight for a single wing panel (top/bottom) is less than 1/2 ounce. So you mix up way more than you need, pour it on there, spread it around, and then scrape it almost all off.

     Another point - watch out for it curing too quickly, particularly if you mix it in a cup. You have to have it remain liquid the entire time, and it takes a while to do the spreading and setting it all up in the cradles. The problem with mixing it in a cup is that it self-heats, and heating it speeds up the curing process. Hobby Poxy Formula II was notorious for this - mix it in a 1-ounce cup, start applying it, and then next time you reach for the cup for more, it is warm to hot. Leave it alone, and it gets hot enough to *boil* in high ambient temps. Instead of your "30-minute" working time,  it might start getting stringy in a few minutes.

    A trick to avoid this is to get a cookie sheet or something similar, cover it with smooth aluminum foil, mix it up, then pour it out in a puddle on the foil. That will let it spread out and keep the working time as intended. 30 minutes is *marginal* to do this, I usually only do one panel at a time.

   How bad the self-heating might be depends on the brand and age of the glue. EZ-Lam in particular is extremely good about self-heating, it barely gets warm, and the working time of 30 or 60 minutes is exellent, it really is still a liquid at the end of the time. Various West systems I have tried is OK. A lot of the "finishing epoxy" types are really bad, and will "go off" in ten minutes and you will not be able to pick up the cup it is so hot.

      I also note that these are *very powerful chemicals" and you should avoid exposure or getting it on your skin if practical. Small amounts are not the end of the world but take some precautions and don't get is smeared around all over you hands, etc.

     Brett

[Brent Williams]

Bob Hunt demonstrated sheeting a wing on the YouTube Stunthangar hangout back in February of 2021.  Nice to watch the master in action.

https://www.youtube.com/live/y4_G11nblDk?feature=shared&t=5145