MTK

I am in the middle of finishing my latest Pattern model, an original design that will be called Papillon. You may remember the movie with Dustin Hoffman and Steve McQueen. It's French for butterfly.

Anyway, I've decided to finish the wood covered surfaces with carbon veil and paint.

The technique is simple but requires a lot of elbow grease. Sanding, sanding and more sanding of the fill coats. But I am getting ahead of myself

After sanding the wood with 220 and 320 to a good finish, I apply one coat of 100% thinned Nitrate dope to seal. The wood is ligthly sanded to knock off some light grain and dust with 320 paper. Carbon veil (0.2 oz) or mat (ACP carries the material as do several other suppliers) is cut to shape and layed down directly over the wood. I dope it down bedding the material with Nitrate 100% thinned (equal amounts of thinner and dope)

MTK

Randolph's dope is a better and less expensive approach to Sig or Brodak. A quart of nitrate and a gallon of thinner cost about the same as 1 pint and one quart respectively of Sig dope from the LHS. But had to pay shipping to get the material from Aircraft Spruce (around 10$)

I brushed the material well into the carbon veil. Carbon is not silkspan and requires no sealing. It feathers superbly with light sanding and really adds terrific stiffness to balsa cavered surfaces, particularly trailing edges. The ailerons on the wing are stiffer than most anything I have built.

The rudder is large on this model, nearly 70 sq inches. It is constructed of honeycombed foam and 1/32" balsa. As one would expect, it was a bit flexible as initially built but a layer of carbon veil stiffened it up nicely

MTK

After bedding the carbon veil, I let the material fully dry several hours, then a second coat is applied of clear 100% thinned nitrate. Edges are worked with a finger to make corners sharp and lay the material down around compound curves such as tips. Thinner dissolves the veil's binder and frees the fibers considerably, allowing them to lay down over compound surfaces. I've written about that before in other threads but it is worth repeating for those who are not familiar with the other threads or not familiar with carbon work

The second coat is allowed to fully flash overnight. Note doubling of the carbon edge at the wing's TE. Very little flex results.

After fully flashing, a light sanding is given the whole surface with blocked 320 paper. The block that works really well is a simple block of foam, 1 pound density

MTK

The surfaces are ready for fill coats. I used either KlassKote clear epoxy paint or the same nitrate dope and filled either material with about 4 parts to 1 part (volume) filler material. The filler I used is a combination of microballoons and Johnson's baby powder

I went the epoxy paint route for the rudder and stab/elevators and nitrate route for wings/ ailerons. Point is that it doesn't matter yet how the filler is applied....what matters is that the filler must be brushed into the carbon veil well, to fill the open space. The recipe sands very easily so I had to be careful not to sand though, which, Of course, I did in spots. Some pieces of carbon veil had to be added to the sanded through spots.

MTK

The wing panels are large for these model types. Each panel displaces approximately 530 sq inches of wetted area. Yet the panels weigh around 260 grams each complete with ailerons cut out and faced, servo mount installed and wing socket already built in. Judicious use of low density wood and extremely light foam (0.4 pound density) accounts for the wing's lightness.
However, the sheeting was applied after first epoxying the carbon veil to the inside as well, then vacuum bagging each panel. Therefore the sheeting is really a carbon, balsa, carbon sandwich

Weight increases after filling to around 290 grams each panel

MTK

One thing I forgot to mention is the types or more accurately, weights of carbon veil you can find. I use the 0.2 oz material for covering wings and stabs. There's also the 0.5 type which is considerably thicker and holds much more dope or epoxy. It finishes much heavier than nedded and isn't recommended for coverings. However is has it's own uses where strength is needed, in places such as wheel pant mounts, landing gear mount fuse reinforcement, wood prop modifications and so on

Chas_97

My Feedback: (5)

Thanks for posting this informative build thread. I appreicated reading it and may try this technique on a warbird build that I plan on doing this winter.

daven

My Feedback: (1)

I appreciate it also, very interesting. Hopefully I can give it a try this winter.

Thanks,

dhal22

more please!

david

MTK

There isn't much more to it actually. It's that straight forward. I always keep my old Escali scale on hand to keep tabs on weight build up. It was around 40$ on eBay about 6 or 7 years ago. It's served me well. It has about 15 pound capacity and 1 gram resolution.

After the fill coat has set, wet sanding with fresh 320 paper cuts the soft filler easily and quickly. It will look like the stab photo attached. Remember the filler recipe...2 parts microballoons, 2 parts baby powder, 1 part nitrate dope (or alternately 1 part epoxy clear paint like KlassKote) and 2 parts nitrate thinner (or lacquer thinner from Cheapo Depo for epoxy paint)

MTK

Doubling up on the carbon is high stress areas such as trailing edges where you would grab the model, helps keep it intact.

After the filler is sanded and wiped clean, a good medium coat of primer is applied. I use KlassKote primer and the recipe that works for me is 1 part each A and B, 1 1/2 parts baby powder, mixed well and let sit for 1/2 hour to initiate polymerization. Then I add 2 parts lacquer thinner and mix well.

This coat is sprayed. I use a simple gravity fed gun from Lowes. If you have expensive stuff, go for it. To me, I have not found it necessary, neither for primer nor for regular finish.

That's my grandson in the last photo of the loose assembly. He is 4 and is my flying buddy. He just loves it

bentwings

Would it be worth it to make bulkheads by laminating veil balsa veil??? Say 1/8 in. In the large warbirds a lot of weight goes into lite ply bulkheads in the rear or behind the GC. This needs to be offset by balast in the nose eventually. Also it might be possible to use it on the skin say 1/16/ veil / 1/16 balsa. No real weight saving but possibly great strengthing.

MTK

In wood Pattern models, carbon/balsa laminates are everywhere. Even my firewall on my new design is a carbon/balsa laminate (carbon cloth in this case and not veil obviously). It saves about 2 ozs over the original lite ply firewall and is stronger. The technique is done as much for strength as weight savings. And BTW, the firewall will support a ZDZ40 gassie

I suggest Carbon/Balsa/Carbon 1/16" or 3/32" sheet 5 pound density stock. Either double up the 0.2 oz carbon mat or use the 1 layer each side of 0.5 carbon veil. Vacuum lam if at all possible to remove all excess epoxy. That's how I built the firewall, vaccum bagging

Tired Old Man

My Feedback: (1)

I notice that a lot of sanding is required with this, or really any other laminating process where painting will take place.

Not noted was the need to wear serious inhalation and eye protection while working in a well ventalited area. Carbon is a substance that the human lungs do not clear. Once in, it's there forever, regardless of the source. Entry to the eyes or mucus membranes can be quite hazardous and most issitating. Carbon slivers penetrating the skin can be quite difficult to locate and remove.

Carbon is a great product and does wonderful things but you need to be aware of the precautions you need to take before working with carbon fiber products.

vx99

hi matt,

over here from the black magic thread; thanks for the reference. just to make sure i'm reading it correctly 100% thinned means 1 part dope, 1 part thinner? or 1 part dope, 2 parts thinner?

and this is probably ignorant, but what's the difference between nitrate dope & butyrate (sp?) dope, and how do you tell the difference if the can isn't labeled with anything other than "dope"

thanks, dave.

MTK

Dave,

Nitrate is used as an adhesive layer in many applications including silk, silkspan and paper or glass coverings, full scale or model alike. You can get it in several types including nontaughtening clear which shrinks very little, or taughtening clear which shrinks much more. It is an industrial adhesive and is sold as such. It is not fuel proof and comes in limited colors.

Butyrate is similar except its formulation results in a fuel resistant finish, and comes in the colors of the rainbow. Chemistry is different. The easiest way to tell the difference is via odor: butyrate has an almost sweet, banana smell to it while nitrate has a more solvent, lacquer thinner smell.

I saw where Mike recommends balsarite. It can work fine. I've used balsarite many moons ago and found it heavier than necessary. Nitrate is about as light as possible and seals well but is not fuel proof and needs the top coats to produce a fuel proof finish. Take your pick....they both work. Butyrate works also as does epoxy clear paint. Clear epoxy paint is heaviest of the bunch but does result in fuel proof base from the start

MattK

MTK

DAve,

100% thinned means 1 part dope and 1 part thinner

Matt

vx99

thanks mtk.[sm=thumbup.gif]

MTK

Don't mention it.... I am glad I could help.

Hopefully, by posting something on this page, it will resurrect the thread. I saw that some guys are asking questions about this method I presented here but didn't see the thread. Well....I hope it comes through and assist you in your project. Afterall, that's what it's all about....assist one another
MattK

iron eagel

Thanks Matt you have always been one willing to help!

Paul

dhal22

it worked, i reread the thread. that is a sweet looking pattern plane.

rinnander

Hello,
Sorry to break in on your thread. But can I cover my 81" ov 10 that is now covered with film with .010 G-10 fiberglass so I can paint it the way I like or will it be to heavy? Thank for any and all advice I get.
Paul

MTK

Paul, it depends,

I don't know what OV10 is. If it has fully sheeted surfaces you may cover it in glass. But 010" glass is thick for covering purposes. It is more like a reinforcing material.

Glass that has a weight rating of .6 to .75 oz per sq yard (these materials are roughly equivalent and have thicknesses around .003") may be used with lighter results because these will hold much less finishing resin.

If the wings are very light, you may try it. What's light? A 1000 sq wing that weighs around 17-20 ozs ready for finishing with glass. If yours is heavier than that ratio, will be heavier than desired by pattern standards.

On the other hand, 1000 sq inch wings can support considerable weight and still fly okay if you don't demand the kind of performance we do in pattern. So it depends

MattK

rinnander

Hi MattK,

Thanks, more info on my plane it is the plane from hobby hanger the Rich Ulrich (not sure if that is the correct spelling of his name) 81" OV 10 Bronco twin engine. I have 2 rcv 4 stroke sp .90 engines for it and would like to give a better pain job than the ultra coat it came with. Where can I get .003 fiberglass and what type of resien or dope do you use with it. Sorry for all of the questions this is my first plane that I am building. I do have other planes but they were like just bolt the wing on and fly. I would like this one to have my own touches in it.

Thanks for all of your help.
PaulR

MTK

I'd guess the weight of the model is on the high side for the power you are going to use. Also I'd guess the wing area to be around 1000 sq inches.

On a project like this one you will may add about 2-2 1/2 lbs of finish easy if you paint. Since this is your first, you may be a bit heavy handed (we all were with our first models) so be very very careful and be certain you want to tackle such an undertaking. The point is that the model may turn out to look very nice but will perform poorly if made too heavy for the wing area and power.

A 1000 sq inch wing flies great if the model weighs 10-12 lbs. As the weight increases to 15-16 lbs, that's about the limit if you are interested in doing some reasonable flying with little fear of the model falling out of the sky due to a stall. If the weight comes in at around 18 lbs you may be flirting with stall with the power you will use

Nevertheless, AerospaceCompositeProducts and CST Sales sell 0.6 and 0.75 oz/sqyd glass cloth. ACP cloth is fine weave and that's what you want. On application, you have options.....nitrate dope, epoxy paint, or epoxy resin will all work well. Nitrate dope is not fuel proof so after application, you will need to fuel proof the model with Butyrate dope of epoxy paint (KlassKote). There are a few threads that explain how to apply and finish such a material. Browse through the pages

Good Luck

MattK