How long do foam wings last

[isabel]

Yes, what I had in mind was delamination (or wing tube coming loose)...
Wing delamination happened to us (caught in time luckily) on a second-hand plane we bought (all fixed now though) and subsequent discussion brought us to consider these questions. Most builders around here seem to build & sell & build & sell etc so we weren't sure about how long these planes can actually last if they are built perfectly. But there seems to be quite a lot of evidence that they can last...

For experienced builders... if you were sheeting a wing that you were wanting to last for 5000 flights (let's say)... what kind of glue would you use? Poly urethane seems the "standard" but I have heard of some people switching to epoxy?

[Roger, the secret is to not put the plane away in the winter... we have skis on our 35% Extra 260... there is something special about an Extra landing in a "puff of snow" And yes it's practicing that leads us to fly so much (we fly IMAC... check out www.scaleaerobaticscanada.com) but also we are two people flying the same planes so it adds up a lot quicker! With two people you can easily fly up to 14 flights in a day...]

Isabel

[jtec/radiowave]

If your worried about foam wings lasting under normal use your probably in the wrong hobby. Gravity or a full speed blender will most likly be the death of any wing foam or built up not the material

Al

[forgues research]

If you look at the type of wing I am building for my Turbo prop laser 40%, its a jig built wing, which is actually stronger, and lighter, and for this being foam ribs, I use carpenters white glue...

Roger

[MikeC3D]

We use Poly Eurothane(Gorilla Glue) for the simple fact that it expands and penetrates into the foam, especially when it is vacume bagged, also we spray with a mist of water or windex and it really makes the foam expand for even better penetration, and the main reason we use this is because it is lighter than epoxy. JMO

[hangingbach]

i fail to see any reason to epoxy the skin on. Unless you want to beat someone with the wing i guess.

[MikeC3D]

	Quote: Originally Posted by forgues research
	If you look at the type of wing I am building for my Turbo prop laser 40%, its a jig built wing, which is actually stronger, and lighter, and for this being foam ribs, I use carpenters white glue... Roger

Roger, interested in knowing/seeing how the white carpenter glue adheres to the foam, does it penetrate? I have never seen it done this way and was just wondering, I know the wood glues make good bonds just dont know how it does to foam.

[forgues research]

	Quote: Originally Posted by MikeC3D
	Roger, interested in knowing/seeing how the white carpenter glue adheres to the foam, does it penetrate? I have never seen it done this way and was just wondering, I know the wood glues make good bonds just dont know how it does to foam.

It adheres just as good as any glue but here is the problem .. if you want to sheet a solid foam core, you can't use the carpenter's glue. This glue cures by evaporation of the water in it. and with large surfaces, it will not happen or at least for a long time. but when you have a half inch foam rib then it s not a problem.
By the way for jig built wings I only use the pink or blue foam, never the white foam as it is not strong enough for this although plenty strong for a solid core.

Roger

[MikeC3D]

Cool, thanks....

[smokin]

i always put the foam block cut-out (for the hotwire tube template) back in and glue it in place behind the inner wing tube supports. this will hopefully eliminate the end point of the wing tube socket from being a weak point. when that foam block is poly'd back in, it really makes the center area of the wing a strong point.

[Wojcigitty]

	Quote: Originally Posted by jaguar bone
	I cam tell your this - CA hinges (yes on smaller planes only PLEASE) will last about 2 years - then hang on for a fun ride!

That's because the CA makes the hinges brittle at the bend line and eventually crack. The best way to install CA hinges is to draw a line across the hinge with a crayon or candle where it will be bending, then put two pins through the hinge on the line. Put the hinge in the surface/wing/stab/fin, letting the pins line up the hinge so that line you drew is between the surface and the fin/wing/stab. Pull the pins out, and drop on some CA. The CA will wick in as normal, but the crayon line will keep the bending part of the hinge from getting glue on it and becoming brittle/failing. I have several airplanes that were hinged in this manner that are 3 or 4 years old with no hinge failures.

Back to the topic at hand: I believe that a properly constructed foam wing is the most durable construction method. I think you would probably have to recover your wing well before it fatigues, giving you time to inspect it. If I were to build an airframe for reliability and longevity, it would have a foam wing.

Also, getting hit in the knee with a foam wing doesn't hurt like a composite wing would.