Now I've built a few balsa kits over the years, but never had to glass one before, so i'm a bit lost on how to do it. Can anyone point me in the right direction or give some tips on a super lightweight glass job?

I have a pretty rare, discontinued and unstarted Multiplex Twinjet foam kit that I'm making into a 200mph+ model. The original kit was designed before the advent of brushless tech and the best motors that you could get were the brushed 480 style giving it pretty fast performance for the time (70-90mph). Now I have two 2600kv Tornado inrunners to fit that will make it absolutely ballistic! So I want to glass the whole model to give it the best rigidity (and durability) I can.

This was my first Twinjet I built, about 7 years ago now.



Ian F.

with foam you could use waterbased poly u and cloth 3/4 oz or lighter since it is electric does not need fuel proofing.

aerowoof gives you the nuts and bolts of exactly what you need to do and live wire gives you the web site for step by step instructions. 1/2 oz or 3/4 oz cloth and wbpu is a great way to cover a plane.

Awesome. Thanks guys, that's why I love this site.

Ian F.

Glassing with wb poly is fairly easy to do and it comes at looking great without adding much weight. However, it adds very little structural strength.

If your concern is strength then it will be hard to beat epoxy and glass. It is heavier but with good techinque not real bad. If weight is the main concern then I suggest poly, but I have not used it with glass yet. I build 20-30 pound planes and want a very hard surface and added strength. Clean your surface well before glassing and only put enough epoxy on to completely wet the glass. Remove access epoxy to save weight. Practice on something first.

Fiberglassing is a system. Different epoxies, vinylester's and polyester's (resins) with different glass types and weave, kevlar clothes and carbon fibers plus others will give very different results as far as strength is concerned in tension and compression, especially when layered and combined. Poly may work just fine for you but there are differencies. I have a little bit of experience with fiberglass white water canoes and the damage they can take. Used carefully epoxy is a wonderful resin used with fiberglass.

It is true that the poly or epoxy or rasin is just the binder; however, to find out how important of a role it plays do an experment. Take some glass cloth, lay it on a peice of thick balsa with a small peice of wax paper under one edge, then poly it down. After it is completely cured pull up on the edge that was prevented from bonding to the balsa. Though difficult you will find it will seperate. Now try the same thing with epoxy or rasin. You will find it almost impossible to remove it. Now keep in mind that the binder not only holds the cloth to the underlying structure but also to itself. The binder prevents compression of the weave or streaching of the weave. The material used for the binder therefore contributes to the overall attributes of the system of wood, cloth, and binder. A strong binder does add to the overall strength of the system much more than some might think.

Sharpeye

The biggest issue with using WBP over epoxy is warping of the wooden structure.
When using WBP over raw wood it will warp & the poly will cure before the structure can be straightened therefore locking in the warpage.
So sanding sealer is used to reduce the amount of soakage into the wood, which also limits how much grip the WBP has.

It is true resin is far harder & bonds stronger, but it is heavier than WBP, marginally.
Both products should be thought out prior to using, & there is no rule that says you can't use both on one plane.

I have a kit that has thin wing skins which will make it dead easy for some noddy to squeeze to hard & fracture/pierce, so I'm gonna use resin to lay up the wing, & WBP for the fuse which is a far stronger stucture anyways.

Like anything, there are ways to save weight, or cancel weight out in other areas, logic applies.

West Systems Epoxy

You will not be disappointed...ever

I have heard of people using wood glue to attach the fiberglass. Probably wont warp the wood like poly, but is harder, and would likely bond better than poly. Kinda middle of the road product. I guess to be sure, a guy could wrap the wing in wax paper, and weigh it down so it doesnt warp.... just a thought, dont know if it would work or not