Working on my Barnstormer top block, I have reinforced the fuse with cross bracing so it is very stiff and the foam top block is just for looks. I am looking at doing fiberglass covering with two layers of 1oz cloth and finishing epoxy. For those that have done foam blocks is two layers enough?

Best,   DennisT

Den,

I would use balsa. Use balsa.

Charles

If you find 1oz CF cloth let me know. One layer of that would do the job. I would use 2 layers of CF vail (tissue) applied at the same time with the finishing resin. Glass cloth, I would go for 2 layers of 1oz cloth so you can sand it all you want.

Motorman

Me three.  Question - is the Mark II OTS legal?

Ken

The pink foam top blocks are about 90% done so balsa is really not going to happen at this point. Also is electric so not much vibration to worry about. I have done fiberglass molded cowl blocks and it worked fine but was from 5oz glass, which I feel is heavy for this application. I just need to have something that holds the shape and is strong enough to hold up to someone picking up the ship and putting a finger on the top block.

I like the carbon idea just need to fine some cloth around 1 - 2oz weight. Resin plan is epoxy finishing resin.

Best,   DennisT

      Sounds like you know what to do but want some one to tell you it's OK. If you have experience using the 5 oz cloth, just adapt going by your previous experience. Going all the way back into the 60s I think, Ron St. Jean and others used foam for free flight fuselage components and just layered silk span or gift wrapping paper with white glue on the foam to provide a durable shell. A local guy here did a Tucker Special once using the same technique  with a couple of layers of heavy silk span and white glue on pink or blue foam. The finish on top of that was clear dope that had been "doped" with dabs of white dope in the clear dope used to do the build ups over it. The model came out less than 40 ounces and flew quite well and was pretty durable, but once the foam got some fuel into it , it degraded pretty quickly. The next time he dinged the ground with it on an outside loop, it wrote off the airplane.
    Type at you later,
     Dan McEntee

Dan,
Like many of us building time is limited so trying not to have to do a redo if I don't have to is a good thing. Again, just want to have enough strength to resist thumb dents from picking up the ship by the fuse (likely me taking it off or on the plane rake.

The Titebond carbon fiber method you mentioned is very interesting. I did remember it after you brought it up and did a forum search. Lots of infor from Bob Hunt and Phil C. I like that approach, just wondering how dent resistant the surface is? Might do a simple test block to see. It seems that it should weigh about the same, just less expensive material. Will see.

Best,    DennisT

Yesterday I did some searching on this forum and found a lot of information by Paul Wood, Tim Wescott,   Istvan Travnik and Bob Hunt about using MiniWax Ploy, Titebond, Finishing Epoxy to adhere the fiberglass or CF to foam blocks. Seems this has been done for ages. I decided to do a simple test to see what each system would add as weight. I made up simple strip blocks from the pink foam, sanded through the hard surface to get it like the surface of the shaped top block which is more open and likely to absorb more material.

First test was to see with just the plain surface coated with each material until it had sealed with a sheen to it how it would feel under a finger pressure, kinda dent resistance. The Finishing Epoxy and Titebond III (thinned) took one coat to seal, the MiniWax Ploy took two as it is very thin our of the can. After drying/curing all day all surfaces were hard to the touch, as you might expect the F Epoxy felt very hard, the MiniWax Ploy almost as hard but the Titebond although hard had more flex. Granted these all would get harder with more time but close enough for this simple test. I had weight each block before applying the material (FE_2,25gm, TBIII_2.4gm, MWP_2.3gm) so I could get a feel for the amount of weight added by each. After they dried/cured I weighed them and the Epoxy was the heaviest followed by the Titebond then the MiniWax Ploy the lightest.

Next I added two layers of Carbon Fiber Vail to each and again filled the wave to a slight sheen. They cured/dried overnight and i did the dent/pressure test again and they all felt stronger and just about the same to the touch. I weighed them and as you would expect the F Epoxy was the heaviest at total gain of 1.35gm, Titebond second at 1.1gm and MiniWax Ploy the lightest at 0.5gm.

My conclusion is that the MiniWax Ploy for simple non-structural blocks is the lightest, easiest to apply and has more than adequate strength and dent resistance for the job with either carbon fiber vail or light weight fiberglass cloth.

Dear Dennis, dear All,
Thanks for introduce me several alternative laminating/finishing materials, since I have always problems obtaining my usual CIBA/Huntsman Araldite LY 5052 resin + its hardener from the aerospace industry.
This Minivax Polycrilic topcoat looks to be similar to our top water based acrylic hard floor lacquers, obtainable in Europe.
Only one question remained open for me: I never-ever found any water based coat, being fully methanol resistant.
(this is not a hard question for electric powered planes, but excludes these coats from using IC powered family, regardless of decoration paint and final covering lacquer).  I tried it, and I cried on it, believe me.
Istvan

Dear Dan,
I need to tell you (and for the collective) my story (lesson) about my experiences. (Thanks God, only the nose got these coats, as follows:
1. Stabilizing paint of thinned LY 5052 epoxy, right onto the bluefoam.
2. Next day, I sanded with 280-320 grade wet paper to get a brilliant, smooth surface.
3. I covered with 1 layer of 2/3 oz glass, with thinned LY5052, After hardened, I slightly sanded.
4. I covered with 1 more layer of 2/3 oz glass, with thinned LY5052. After hardened, I slightly sanded again, the surface became superior quality, and strong enough to bear the engine bank,  tank, undercarriage, etc. Without long, hardwood spars...
I got waterbase acrylic hard floor lacquer, colored it to yellow, and sprayed on.
And sprayed on 2-component transparent polyurethane floor lacquer, just like before, for 50 years...
After several months, some vertical ripping appeared below the tanking/overflow tubes...
Next year appeared the foam, covered by the glass, in half centimeter wide strip...
Ripping and stripes, more and more...
 Finally, I put this complete nose into Polyethylene sack, fill with methanol, and after a week, I simply scratched everything from above the epoxied glass surface, by a bankcard. And paint with 2-component yellow polyurethane, and 2-component acrylic auto-lacquer on the top.
Istvan,