I realize that there will be weight gain back there. That's not the reason for this exercise.. It's outlined in Post #1, 15, 17, and 19.

Thanks for the input

Bob

N1EDM,
In keeping with the original idea.......
Glassing over an open area does have sensible applications. And it's really a decent idea to learn how to accomplish it. It's also a good idea to see how it works in use.

As I mentioned in an early answer, taut silkspan can serve as the "mold" that makes spanning an opening with glass cloth in resin possible. I've done it and it works. I don't remember the exact products I used but the epoxy was very probably HobbyPoxyII. Epoxy structures are far more flexible and forgiving than polyester resin ones. That's why I used epoxy and it worked. I do remember that I concluded that my use of glass cloth gave less than the best result, that I should have used thicker if I stuck (pun intended) with glass, but that a less brittle cloth would have been better. There are cloths just like that available today.

Thanks, Darock... That's the kind of information that I'm looking for.

I've heard a lot of people say that they like West Systems epoxy.. I presume they mean the stuff from West Marine, but I'll check. I'll need to make sure. Folks like that a lot better than Z-Poxy. I'm going to try to stay away from polyester resin if I can. Smell is too severe.

Thanks again for the reply.

Bob

Both of my LHSs have West Systems products for sale. They both have what looks like the complete line. It appears to be products selected for marketing to our slightly narrow requirements. Or maybe it's better to say that they're offering a simpler set of components.

Their selection and sizes look like West Systems was fairly sensible and made good choices for what to sell. I've not used any of their stuff yet so can't comment on how it works, but their pump dispensers do look like a very good idea for anyone who builds year round. They also have a couple of brochures that provide some good info on what they're selling and how to use it. I didn't see any glass cloth or any other cloth for sale in their displays. I'm just guessing that they only market the resins.

....and a bit of hint/discussion/thoughts....... Someone mentioned that they thought the silkspan would sag from the chemicals in the resins. Mine didn't but I used epoxy. Polyester stinks because of the very strong chemicals in it, some of which are solvents. I'm not altogether positive that epoxy is free of solvents, but it appears to me to be just two components without solvents.

Also.... I used HobbyPoxyII because it had the longest pot life I could find. I wanted to brush it on, and thinning epoxy with alcohol weakens it measurably. I also thought the alcohol might hurt the silkspan's tightness. Slightly heating the resin does a great thinning job but shortens the pot life, so I used a long pot life epoxy.

Also.... Almost all of the strength of a layup comes from the cloth being locked by the resin. Almost all of the weight of the layup comes from the resin. So a "dry" layup is preferred. But I wanted light (which suggested light cloth) and dry and had no idea how strong the silkspan was going to remain while applying the epoxy. One technique to get lightness is to blot off the resin until the layup looks somewhat dry. Blotting over the silkspan that was over the holes was scary at first. If you find a very bulky, thick, soft toilet paper and use it to blot, it works great. Don't unroll it. Blot with the intact roll. Gently press and lift. Pull off the saturated layer and you got a "dry sponge" again. It takes a touch, but what do we do in building our models that doesn't?

Also.... People often layer to achieve their desired strength goals. If you let each layer cure to hard, you're "making plywood". If you schedule your layering so that each next layer goes onto the previous after it's kicked, but before it's hardened, you will be creating one solid layer from bottom to top. But, hey, plywood is strong too, even if under some conditions it delaminates.

I hope your testing works and look forward to reading about your results.

If you are talking about the woven fabric showing, it didn't show up with fiberglass on top, but probably would if you simply epoxied the cloth. Koverall is almost as light or lighter than MonoKote, but heavier after painting. If you go to some C/L and FF sites you will find a material called Polyspan that is heat shrunk and looks like and is about the same weight and texture as silkspan. That should also work. I wasn't after maximum strength as much as durability so I thinned the epoxy slightly with laquer thinner. Works better than alcohol as it evaporates quicker and well before it cures, so you get a stronger resin. But not as strong as unthinned epoxy.

Another method is to wax a sheet of window glass with floor wax or mold release wax and lay a layer or two of glass cloth. Squegee on finishing resin with a playing card. After it hardens, peel it off and glue it onto the surface. Nice and flat, no sag.

FYI: http://www.westsystem.com/

And low prices from: http://www.solarcomposites.com/

Thanks for the comments, guys... Sportpilot, no offense, but I'm not interested in learning how to work in Koverall at this time. Maybe later. This thread is for me to learn how to use epoxy and glass and to cover open areas for painting with Klasskote. But thanks for the input.

Thanks for the link on WestSystems. It does appear to be distributed by West Marine, after all.

I'll have to find a local distributor for it.

Keep the ideas coming!!! This thread is starting to take of now...

Bob

N1EDM, I've been following this thread since it's, one, an interesting problem, and two, because it's purpose is so puzzling to me.

But anyway, I have a lot of experience with fibrous coverings including Silkspan, Polyspan, Litespan, Airspan, Jap Esaki tissue, Koverall and silk, and others I can't remember.

In my own experience, nothing provides as taut a surface as real silk filled with several coats of nitrate dope. The drawback is that it takes a long time before it fully cures and finishes shrinking, as in weeks or even months.

Other than filling the open areas with solid material - which I know you don't want to do - I'm not aware of any fibrous material (such as silkspan) that will provide as tight and rigid a surface as Jap silk and nitrate when properly applied, sealed and shrunk.

I have painted 30-minute epoxy over silk that is covering open areas for the purpose of fuel proofing and almost 14 years later it still hasn't cracked. I can't imagine why the same would not hold true had I included a layer of glass cloth in the process. Applying epoxy paint over this (Klass Kote, for example) wouldn't change anything as far as I can see.

Here are a couple of pics. The pylon (wing mount) is Japanese Esaki silk, the fuse is Esaki tissue. Both are coated with epoxy. This was done in 1992.

Rainy day, that plane is absolutely gorgeous. I saw a plane like that win an award at the WRAM Show in 2004. You should enter it if you have a similar show nearby.

The basic premis of this thread is that I want to use an LT-40 that I'm currently building to cut my teeth on a glass epoxy finish, and Klasskote. I have a Scale project in the wings, and I don't want to use that as my 'learning tool'. I'm willing to accept the weight gain, etc., on the LT-40 in order to gain experience.

But, the LT-40 has some open areas in the aft fuse and from everything that I've read, you can't put epoxy over glass over an open area, so I was thinking about applying some silkspan (it has a tight weave) over those open areas before I applied the glass and epoxy finish. I just wanted to investigate the feasability of doing this.

I have some silk (from thai silk) and maybe I'll give your idea a try. My LHS should have some nitrate dope. I don't want to do anything fancy because the covered areas won't show.

I've had a Playboy Sr. semi-kit for about 3 years that I keep threatening to build, and I bought a Dennyplane at an auction but haven't flown it yet. The Dennyplane has a Monokote finish. But, I might consider silk and dope for the Playboy when I finally get around to it.

Thanks for the tip. And, thanks for those photos... beautiful finish on that plane.

Bob

Thanks N1EDM! There's no thrill like building a FF old timer and seeing it climb and glide on its own without radio assistance. But that's a different subject.

I think silk/nitrate is your ticket. Just in case you haven't used this method before: apply three full strength coats of nitrate dope (don't use butyrate to adhere covering) to the edges of the fuse. You can sand between coats. Silk can be applied dry or lightly misted with water; try both to see what you prefer. Start attaching the silk by brushing straight dope thinner on the silk and rub the area with your finger as you would rub an iron when using Monokote. The thinner will desolve the nitrate below and glue the silk down. It re-dries very fast, but can be released with more thinner. Then just stretch the covering across the open area and adhere it, pulling out wrinkles the same way you would when covering an open area with Monokote. After all edges are adhered, mist the silk with water or alcohol for the preliminary shrinking.

Now comes the hardest part. The silk must be filled with dope to seal the weave and fully shrink it. I use nitrate for this stage, too, since I think it has more solids and shrinks tighter than butyrate (which I only use as a topcoat for glow fuel-proofing). If you are brushing it on, you should thin the dope a bit so that it won't form droplets on the underside of the silk. Several light coats are better than one or two heavy ones. You only need to let it dry for an hour or so between these coats. If you have a spray gun, then it is a much easier process and with light coats you don't have to worry about the dope pooling up on the underside. Preventing the dope from collecting under the silk is the only part of the whole process that is somewhat of a pain, but with practice, you can avoid it. After the surface has a nice sheen and you can no longer see any pin holes throught the weave, set it aside for several days to cure and finish shrinking. The longer the better. After this, you should be able to apply the glass and epoxy without trouble. I hope. I at least know that epoxy alone works fine.

If you decide to give this a try, let me know if you have questions.

I look forward to seeing that Playboy Sr. Then you can join in the fun of running spark ignition engines!

1940s Ohlsson & Rice .60:

Nice shot of the O&R 40. Thanks for the method for applying the Nitrate. I'd always used butyrate over silkspan, have never used silk.

I always thought that you HAD to brush on dope. I thought that there were reasons for not spraying. Obviously, I'm mistaken. That's nice because I'm in the process of looking for a good quality HVLP gravity-feed setup. What size nozzle do you use? I was planning on getting a 1.3mm nozzle, which seemed to be the one recommended for KlassKote. I'm wondering if it will work OK for the dope as well, or if I should get something smaller.

Thanks again for the tips, and I'll move that Playboy Sr. project up a notch or two now...

Bob

Another variation of the paper towels is the use of a roll of (unused) toilet paper. It is very absorbent and blots off virtually all of the excess resin.

I saw several posts about using epoxy resin to paint down fiberglass cloth. My question is, how do you go about doing it? Should I thin it with alcohol or not? Should I use 5 minute or 30 minute epoxy? Just so you will know, I am reinforcing the firewall on a Hangar 9 Corsair to put a RCV 90 engine on it. The photo shown is from another build. The light colored pieces of wood were cut as backing plates for the engine mount. My plan is to cut plywood to the shape to completely fill those spaces and then glass cloth over them. Thanks for any advice.[img][/img]

N1EDM, the set-up you're looking at should be fine; whatever nozzle works best for your epoxy paint will spray nitrate. The dope is usually sprayed 1:1 with thinner. The trick is not to get it on too heavy as to collect under the fabric. Wear a mask!

Well Koverall is easier to use than Monokote. And I know you can cover open with glass over the Koverall because I have done this.

Hi!
Corvin...fasten glassfiber to any surface is not done with 5 or 30min epoxy! Instead we use epoxy resin, that is 24 hour epoxy which is more like thick water [] in consistency which dries glass hard and is easy to sand. 5 and 30min epoxy is more "rubbery" in consistency, not what you should use together with fiberglass.

But back to the covering issue using glassfiber to cover holes in a trainer fuselage.
This should not be attempted because covering lightning holes in fuselage is much more easily done with either silk and dope or a using plastic covering films like Oracover or Oratex, Solartex and the like.
If you still want to cover the front part on the airplane with glassfiber and resin (either 24 hour epoxy or polyester resin) ...go ahead ...but stop at the rear and cover the holes with silk and dope or the more modern fabrics or films ...and then paint the airplane. Don't try to cover the holes with glassfiber ...its not the way to do it! It will only render your airplane heavier then necessary.

Regards!
Jan K
Sweden