otrcman

I'm about to put the finish on a balsa sheeted fuselage and wondering about using carbon veil and also about attaching it with dope rather than resin. I've used 3/4 oz glass cloth and resin before and haven't been impressed with the easy puncturing of the surface. It feels hard, but in service it's fragile as an eggshell. If I put enough resin on the surface to penetrate the balsa at all, then the weight buildup is excessive. I'm thinking that nitrate dope would penetrate the balsa a bit and make the surface a bit tougher much like silk and dope over balsa in the old days.

Questions:

1. Has anyone tried using dope & glass cloth or dope & veil before ? How did it work out compared to resin ?

2. Is there a clear choice between glass cloth and carbon veil ? I've never used the carbon before.

Thanks,

Dick

bentwings

I've been considering using veil too for the covering but actually I'd like to lay the veil on first with a thineed coat of finishing resin then lightly sand it and overlay it with 3/4 oz cloth and thinned finishing resin. I've had very good results with the 3/4 oz cloth and finishing resin. It sands easy if not glopped on and fills easy with primer and what ever paint used. My thought is to use the veil as a strengthining material but not for puncture resistance.

Also I'm considering using the veil as a laminate to make balsa plywood for my sheet stock to replace the lite ply whereever possible to reduce weight. For example laminate 2 layers of 1/16 balsa with the grain placed at 90 deg to each other. Use thined Elmers for adhesive. Then laminate CF veil on both sides using thinned finishing resin. This could be vacuum bagged but I think there would be more resin trapped than if I squeege most of like I normally do. Anyway I'm planning on running some tests this spring and early summer. Assuming it works out I'll build a new Ziroili Corsair with a projected weight of no more than 28 pounds wet. This compares to 37 pounds for the last one. Battery and electronic tech will aid in reducing weight too. I really don't like carrying 5 pounds of lead ballast around.

There will be a considerable amount of CF for other strengthing especially in the center section of the wing.

iron eagel

I am doing my Sig Somethin Extra using this method.
With the dope it is very lightweight.
http://www.rcuniverse.com/forum/m_66...12/key_/tm.htm
http://www.rcuniverse.com/forum/m_77...tm.htm#7975543

otrcman

Thanks for the reply and the links, Iron Eagle. That's the information I was looking for and gives me confidence in trying the veil/dope myself. One thing I'm hoping to see is a little firmer balsa substrate due to the soaking in of the dope. Seems to me that you can brush on thin nitrate dope to penetrate the balsa without much weight gain whereas letting resin soak in is a disaster in weight buildup.

When I was involved in Space Shuttle thermal tile development we quickly found that the tiles didn't bond well until the contact surface was "densified". Tiles are very low density silica fiber matrix (think: styrofoam strength and density). The tiles are glued to a thin sheet of Nomex felt which is in turn glued to the aluminum structure. The glue used is RTV (far more expensive than the consumer type of course). What was found initially was that the Nomex felt could be easily peeled off the back side of the tiles, leaving just a bit of the tile material adhered to the RTV. The tile material just wasn't strong enough to withstand local tension loading. The "densification" was a slurry which was brushed onto the back side of each tile and penetrated 1/16 to 1/8", leaving the surface much harder and stronger. RTV bonding to the denser surface was satisfactory. This is what I hope the dope will do for the balsa, making the surface a bit less of an "eggshell".

Dick

otrcman

One more question for Iron Eagle ... or anyone else with veil/dope experience:

Following your guidance, I applied carbon veil to the fuselage of my scale F3F biplane. It went on just as easily as you said it would and I'm really happy so far. Now for my next question:

I have 3 thinned coats of clear nitrate over the veil and so far have not sanded. The dope has not yet built up to the point of obscuring the texture of the veil. I'm a little worried that the veil will fuzz out when I try to sand it. Is this a problem ? From what I read of your posts it sounds like you went directly to color dope over the veil. Is that correct ? Do you have any difficulty with sanding the surface ? Have you sanded through the dope to the point of hitting the veil ? What grit sandpaper do you recommend ?

Thank you,

Dick

iron eagel

I used tinted clear dope after the first couple of coats of clear, then I progressed to a mix of clear and colored dope to put the last few sanding coats on. When I first sanded I used 200-240 grit very lightly (to cut off the big lumps). This removed the fuzz quickly and it was easy to pick out the high and low spots in the finish easily that way. It is very easy to sand through the veil so go lightly with the first sanding. I then applied another coat of mixed dope and let it dry for a couple of days, then used 300 grit to sand that coat down. After that I switched to using 600 grit wed dry from then on, and wet sanded after each coat. You will find that it is best each time after you get the first few tinted coats on and sanded to allow a day or two for any moisture to evaporate, a warm dry place also work well to sped up the process. When you get to the point that the surface feels smooth after sanding your tinted coat go with you first color coats, the first one or two use 600-800 grit and go up from there, the last few times sanding you want to use very fine grits where as for the final coats you want to burnish the surface more than sand it.
By the way one more tip, do not brush the dope over the veil to much that pulls the fiber and will make a mess.
Oh and if you by chance sand through the veil don’t panic. You can apply a patch of veil and then feather that into the rest of the surface fairly easy…

edit to add:
For the first few times you sand you will hit the veil do not worry about it or seeing the weave, it will be covered very quickly with the dope. If you start to see a lot of black or gray when you sand you are cutting the veil. You can sand through the veil fairly easily so go lightly with the sanding, I strongly recommend wet sanding from the beginning so you can see how much carbon you are taking off (by the color of the slurry). Note to mention it spreads over everything like the waste from a pencil sharpener...

iron eagel

I had meant to reply to your comment about the tile problem you had mentioned...
I had heard about that but did not realize that it was as bad as you had said it was.
I have handled the material you spoke of and it is some wild stuff!
I could not believe the seeing it or feeling the density and weight of it, actually could withstand the same type of abuse that ablative materials used earlier for the purpose had.
Not to mention the thermal properties are pretty wild...

otrcman

Thanks again, Iron Eagle.

I think I'll let the model sit for a couple days to let the first 3 coats dry, then try taking the big lumps off as you said with 220 grit wet. Since I'm using nitrate clear and don't have any colored nitrate to mix in, I'll thicken my dope with talc as a sanding sealer. Maybe a couple coats of that, then cut it down again with 220 or 320. My final coats will be butyrate color, with a bunch of plasticizer added to prevent bridging in the fillet areas. I'm sticking with nitrate as long as possible because it doesn't seem to bridge as badly as does butyrate.

By the way, after your warnings I was careful about brushing to much for fear of going through the veil. As it turned out, I never went through at all. But I'm suspicious that I may have .5 oz instead of .2 oz. The veil did come from CST but is marked .02 (whatever that means). The material wasn't as delicate as I expected from your comments, and my fuselage is much blacker than what shows in your pictures. Are your pictures really indicative of the color after putting veil on or is it blacker in real life ?

Dick

iron eagel

Bentwings,
Have you tried the balsa carbon laminate experiment yet?
I would be interested in hearing what your results were...
I have to applaud your goal of a 28 pound (wet) goal for that size Ziroili Corsair!!!
Wow, that would be one awesome warbird...
I agree with your idea sounds like a great way to enhance the performance as well as make a rugged bird at the same time!

Now I have recently upgraded to a 2.4 Ghz radio for my SSE, and I plan to install the antenna externally by putting them in styrene tubes, so they resemble full scale antenna.
I am a bit gun shy about trying the antenna within the shielded fuselage at this point, why temp fate is my thought at this point.

iron eagel

Dick,
In person it seems a bit darker, the flash makes it look a lot lighter then it is. One of the shots I posted was one of the cooling duct that was planked, it had been shaped so I had used a color coat to check the shape was indeed sanded enough to apply the veil. Most of what you see is a single layer, I only used more than one layer in high stress areas or in areas where I had opted to use more than one piece to cover some areas that I was concerned the veil would not conform to, before I got a feel for just how much you could "work it" around complex shapes.
The material becomes very delicate when you first lay it on with a 50/05 mix of dope and thinner, i managed to tear it with one stiff brush I was using in the beginning. (not to mentioned some that stuck to my fingers when I touched a "damp" area) As compared to silk I think it is more along the lines of paper tissue not quite as bad but similar if you take to long working it.
Oh I know all to well of the bridging you mentioned!
I had some problems early on when shaping the wing root fairings into the fuselage via fillets.
Oops!
Well that's not what I actually said...

Paul

iron eagel

and to add a bit more about the color...
The photo showed when I was applying the veil, only the darker areas had dope on it in that shot. As you may have noticed the weave becomes much more defined once it it is bonded to the substrate.

edit to add...
If you veil was marked .02 I would think that was the size mine came marked the same way.
I will tell you it sure took the sharpness of the scissors I used to cut it down fast!
The filler you mentioned works very well but it does not take all that much. You may be able to jump up quick on the grit of the paper as you sand you will find that the weave fills very fast as compared to silk or glass.

bentwings

I'm waiting for this winter weather to become spring. If it doesn't come soon the summer will be half over. I want the garage to remain at least 60 deg for the tests so I can work comfortably. I know it will be a lot more work building for weight and strength but it should be a good challenge. We'll go with the 2.3 tech also and so light weight batteries. I may even send the motor out to RC Ign for the lightweight treatment. My goal is to have no ballast inthe nose. My son is already concerned that I will deep 6 the Glennis wheels. They are really nice looking but they weigh a ton and a half at least.

iron eagel

We have gotten a few teaser type of days between the rain, I understand about you longing for spring, and having the shop over 60. Thankfully it is a bit warmer here than what you have to deal with but this winter seems to want to linger on and on.
True it is a lot more work when you build for the lightest weight and strength. Some of the pain seems to be centered about the wallet from my experience…
Yea but if the wheels look cool on a scale model….(sometimes you have to bite the bullet and make up for it elsewhere)

otrcman

You guys in the northeast and upper midwest are a tough lot to live in such cold country. As a kid I lived for 2 years on Cape Cod and then a year in Buffalo. That was enough for me ! Where I live in CA it almost never goes lower than 35 or over 85. On the other hand, we get to put up with about the highest taxes and nuttiest politicians in the country.

I couldn't stand to wait any longer and pushed ahead with sanding the finish on the F3F. I lightly block sanded the clear dope to identify the high spots and found no further contour fill necessary. So then I went after it lightly with 180 to take off the top of the texture. Went through in one tiny spot which I patched. Then brushed on a generous filler coat of talc & clear nitrate. After a few hours I hit it again with the 180 on a rubber block and was rewarded with a finish that was 98% smooth. Wanting to get rid of all the minor imperfections, I brushed on one more coat of the talc & nitrate. That's drying now and tomorrow I'll take it down again, this time with 320 on a rubber block. I hope it will be ready for color butyrate at that point.

I neglected to weigh the fuselage before & after putting the veil on, but it sure doesn't feel any different. All told, I used 1/3 yard of veil and about 2/3 pint of nitrate. If this had been glass and resin I'm sure the airplane would feel heavier.

By the way, I have several brand new pints of "Lee's Trophy Dope". Two cans are the navy gray that are just what I need. The cans are marked Fuel Proof, so I'm quite sure they are butyrate, but I don't know if they are low shrink or not. Sig thinner cuts the dope perfectly. Do any of you remember how much castor oil we used to put in dope to plasticize it ?

Thanks, Dick

iron eagel

15 minutes from the canal here, not all that bad... was 60 Friday
Does this F3F have retracts by any chance??? (very nice!!!)
So do you think it is hard to patch when using the veil and dope?

I have just gotten a 2.4 GHz setup to use in my SE, did you see the links regarding radio setup and carbon fiber?
The Sailplane guys have a few tips on it.

As far as:
By the way, I have several brand new pints of "Lee's Trophy Dope". Two cans are the navy gray that are just what I need. The cans are marked Fuel Proof, so I'm quite sure they are butyrate, but I don't know if they are low shrink or not. Sig thinner cuts the dope perfectly. Do any of you remember how much castor oil we used to put in dope to plasticize it ?

No clue...
Fine scale type of question...lol
perhaps...
Jack Patrolia or someone like that could answer...

Ever see his cl B24?
The pits is sweet also...

MTK

I have done quite a bit on the carbon veil/dope technique. It's a series with fairly hi-res photos. Look in the current folder and you find my file. I think I named it "covering balsa with carbon veil" or something like that. I'll look for it and post the link here in case you don't

MattK

iron eagel

the link is:
http://www.rcuniverse.com/forum/m_81...tm.htm#8106294

Thanks Matt great info on the process!
One question as I am just finishing up mine and your post is from last November have you reached the point were you are doing any radio equipment install yet?
Or do you have any thought or info regarding radio issues?

MTK

No radio....this has been a veeeery slow project for two really good reasons: Grandson Cason and granddaughter Abby. They are very young and we have full custody...keep us very busy. And as you can imagine, we are always tired

On the radio question, I know some folks who have used fuses with quite a bit of carbon and have not had issues in the 72 MHz band. I also suspect that the new 2.4 gig freqs are better than the older 72 Meg frqs in this regard due to the dual RX's. Please keep in mind that carbon veil is about 80% open.
In my situation I expect zero problems because the fuse is fiberglass with minimal carbon. The wings/stabs and rudder are the only areas covered with carbon veil.
MattK

iron eagel

Thanks,
My entire airframe is done in carbon fiber veil (in some places such as the turtle deck, aft fuselage and tail feathers have two or three layers. I did this because of the modifications to the tail such as: removing external bracing, tapered to the tip stabilizers, as well as enlarged surfaces.
And I too have had many delays...

Edit to add:
I have both 72 and 2.4 now to try.
I appreciate the info on how you feel about it.
I also got a lot of good information supplied by the sailplane guys who have been using a lot of composites.

otrcman

(quote)
"One question as I am just finishing up mine and your post is from last November have you reached the point were you are doing any radio equipment install yet?
Or do you have any thought or info regarding radio issues?"


I did call the Airtronics technical hotline about possible problems with carbon covered fuselage. Unfortunately, I didn't distinguish between veil vs woven cloth when I posed my question to him. The advice I was given was that in both 72 and 2.4, the antennas must be external to the fuselage to work adequately.

MTK's observation about the low surface density of the veil might be significant. As with any RF transmission, there is a relationship between the wave length of the signal and the mesh size of the screen. We need to ask this question of somebody who knows more about RF than I do.

One more observation regarding 2.4 radios: My understanding is the wattage output is lower than on the 72 radios. I guess this is part of the FCC requirement for use of the 2.4 band. So lower signal strength is one of the reasons why the manufacturers give such detailed instructions regarding antenna placement and orientation.

Dick