I am in the process of building a Ziroli B-25 and a Don Smith B-17. All of my building experience is covering with Monokote. I have never covered with fiberglass. I would like to hear as many opinions as possible of the techniques of glassing using epoxy verses using polyurethane. I have read only one article using epoxy and one article using polyurethane. I am still not sure which way to go. So I would greatly appreciate any comments.

I've used every technique and product imaginable for glassing. Here are my opinions:

Waterbased polyurethane tends to warp sheeting up to 3/16 of an inch thick. It doesn't fill the weave well in the cloth, and I won't use it again. It is easy because there is no mixing, and cleans up with water. It dries in a few hours, so it is possible to put on several coats a day.

Polyurethane finishing resin is good, sands better than most epoxy resin, and in my opinion, smells good. The only problem is if you use wood filler to fill dents and dings, the resin may not cure. It also doesn't like to cure over most 5 and 30 minute epoxies.

Finishing epoxy such as the West systems, EZ lam and the Pacer Z-poxy finishing resins all work well. They will cure over everything, but will gum up the sandpaper while sanding. Except for the Z-poxy, you should wait several days or up to a week before finish sanding the top coat.

I use to weigh each project before and after the application of the finish resins, and I always seem to have the polyurethane finish resin end up the lightest per square inch.

Email me privately if you have specific questions about application techniques.

Moot

rcflyerjoe,

I would suggest that you contact proflooney over in the warbird forum. He has a very informative section on his website about the various methods. Try also to contact Kirk (Ksonn) here on RCU. He was a devout Epoxy Resin guy and has achieved favorable results with the poly method. Also you can contact Warbird Fanatic here on RCU. He "Wet-Nursed" me through my first glass job and panel lines (Great Planes P51). The results that I was able to achieve on my first experience were terrific and these are the people who I turned to. Very helpful and really nice guys each and every one.

Good luch in your efforts.
John

Thanks for the comments guys. I have read Proflooney article and found it to be very informative. It seems that all methods have their good and bad points and depends on which one you want to put up with. No one has commented on the strenght of each method. Are they all the same, are is epoxy stronger? I have a few more weeks before I will need to decide. Thanks again for the help. Joe

Nitrate dope is a pretty easy way to attach thin glass cloth. Just paint it on top of the cloth (preferably after a couple of coats on the raw wood first, with light sanding). Apply several coats, then sand a little, and you are ready for primer. I also use Pacer Finishing resin. I think it is a toss-up on which system is the lighter.
The finishing resin may be a little less work on flat surfaces like wings and tail. On curved parts like fuselages, the nitrate is probably easier.

You might give the nitrate a shot and see if you like it.

Clair

One common theme I think you will reach as you search for info and talk to others about glassing and strength is: "The purpose of glassing a plane is to provide a smooth, hard surface where paint and detailing can be applied." Most everyone agrees that you should build strong in the first place and not rely on glass cloth to provide any measurable amount of additional strength.

That's what I found in my research.

John

Thanks again for your comments. I came across a real intresting article last night. It really leans me toward the water base polyurthane method. Here is the link if anyone would like to read it. http://www.renderwurx.com/rc/glasstest/index.htm

Hrm... perhaps that shoots a big hole in some of my pondering and plans... I've been looking at foam slope ships (perhaps a Weasel Pro to start with, and eventually something fun like a Mig3), and one of several "accepted" methods of covering the things involves lots of fiberglass strapping tape (for strength and durability?) followed by colored packing tape or solartex iron-on film. I thought to myself "hrm... why not just get some light-weight glass cloth and glass that bad-boy, skipping the tape business!"

Am I way out in left field, or might this produce acceptable results?

Rick:

The 'glassing can be purely for a smooth surface finish, in which case very light and finely woven cloth is used.

But it can be for strength as well. All you do is use a heavier cloth.

However, a well designed foam wing usually doesn't need the reinforcement.

Bill.