Shrinking Silkspan

[7car7]

I'm covering a tail group with Silkspan. This is a balsa open frame.

First, I didn't realize I was to put it on wet with WATER. I tried getting it wet with accetone. I imediately painted down the edges, and then proceded to the surface.

That produced a very loose covering. Not adequate. So I ripped it all off of all 4 pieces. Not fun.

Then, after reading every thread I could find in a search, realized that I should wet it with water, then just stick down the edges, and let dry. I did this, and tried 2 methods - air dry, and heat gun dry.
This time, it is much better, but still not as tight as I'd imagined it would be. Now I'm not sure if I should proceed with the dope, or what?

I'm using Butyrate black dope. Is there something that would shrink MORE than this? I was told by the LHS OWNER that if I wanted it all black, I didn't need to use the clear first.

[Pinecone]

Been a LONG time since I did silkspan, but IIRC the clear will shrink and seal the silkspan.

[ronrange]

One method that worked well for me years ago.

Dope the frame with a couple coats of nitrate dope and sand smooth. Wet the silkspan and lay onto the surface to be covered. Smooth out somewhat and then apply nitrate over the silkspan to the perimeter of the surface to be covered. The dope should be fairly thin for that process. Trim the edges. That should bond it in place. Repeat for the opposite side of the component being covered. After the silkspan has dried you cn proceed with applying the dope.

Another method which I have not tried but sounds like it should work equally well is to use a thin mixture of white glue applied to the outer surfaces to bond the silkspan in place. Otherwise all about the same.

Good luck

[7car7]

Thanks guys for your help!

I am having good results now. I went and bought some SIG Supercoat and thinner. (Last time I was just using acetone for thinner.)

The pieces are coming out nice and tight now. So I'm left to believe that the colored Brodak is not to be used for shrinking. But to be fair, I did not use the colored stuff after getting the tissue wet, and only gluing down the edges.

Oh, by the way, the Supercoat is also a Butyrate. Not a Nitrate. I didn't get a Nitrate, because my frames already had Butyrate, and it sounds like you can't put Nitrate over it.

The only issue I have now is that each time I put on a new coat, it stretches out again, and tightens again. I'm concerned that when I put the black back on, it may not shrink it again. Oh well, only one way to find out...

[Lost_Dawg]

I still like to do silk/tissue/silkspan and dope. I just finished an Ugly 30 that I built for RC electric that I covered with Polyspan and clear dope that I tinted with drawing ink for the look of an old time silk and dope finish.

The thing about nitrate dope is that it's light weight. I believe it also shrinks less. You see, not all types of dope shrink the same amount. Sig Lite coat for example is a low shrink dope. On smaller planes or a piece that you expect to put a lot of coats on this can be pretty important. The more dope you put on the more shrinkage you will get and you can get big time warps or even structural damage in an extreme case. I always try to do both sides of any wing or tail one right after the other to reduce warping.

Thinning with acetone doesn't work well because it evaporates way too fast and tends to create problems with blushing. I use acetone for clean up though to save $ over thinners. You can use Dupont 3608S as a thinner for Sig dope. Works fine for me and will save you some $. Buy it at auto paint supply shops.

You mentioned brodak colored dope not being used for shrinking. Color dope shrinks just like the others but the reason you should start by sealing everything with at least 3 coats of clear is to avoid the weight penalty that comes from using color. The pigment is what adds the weight to dope. Clear will not add nearly as much weight to your plane as color. Get the sealing and surface quality you want with clear then shoot as little color as you can for a look can live with for the final finish. You will find that you will have your best luck ir you stick with the same brand of dope for the whole project. Here's a little word to go by: EBAN.

E: You can put enamel over all dope.
B: Butyrate dope over acetate.
A: Acetate dope over nitrate.
N: Nitrate over nothing.

My basic proceedure is to coat the wood with two or three coats of 50/50 clear with very light sanding w/220 grit to remove bumps, globs and hairs between coats. Next I cover with wet silkspan. Spray it with some kind of spray pump from Windex, Shower Clean, hair spray, etc.. Pull it tight gently so that it's pretty decent but not drum tight by any means. Dope it in place by going around the perimeter on open frame work and go full coverage on solid surfaces. There should be no need for further water shrinking. Three to five coats of clear after the paper/silk dries will do all the shrinking you should need if you got the covering on there right in the first place. I put all this clear on with a very soft brush.I thin ALL Sig dope at least 50/50, sometimes more for spraying. IMHO Spraying is bad for your body and should be done as minimally as possible with proper ventilation and a serious professional respirator with organic vapor cartriges and spray mist filters.

Hope this helps.

[7car7]

More great advice! Thanks so much.

My pieces came out great, I'm very happy. I did a few coats of the clear, and each time it stretched out nice. Then I did the black, I think 2 coats. It was thinned about 50%. Came out perfect.

I think my original problem is I simply just did not have the Silkspan wet.

Now that I have the hang of it, it's easy and fun. I now wish I'd taken all the Monokote (maybe?) off the wings and fuse of my "ARF" plane and done Silkspan instead. Oh well, next time!

[grb]

sure brings back very fond memories of learning how to build airplanes in the lat 50's and early 60's with my father.

We used almost the same process as mentioned above with coating the wooden structure with a couple of coats of dope and then wetting the silkspan and after applying the wet silkspan brushing on a coat of dope on the wooden parts to set and seal the silkspan. Almost all of the shrinking would happen when the silkspan dried but on occasion it was necessary to use a spray bottle and re-wet isolated areas to help it shrink. After the silkspan was taught to our liking then we would dope the whole structure with a couple of coats of clear and then apply color to our tastes and needs.

[Mike1484]

What once was old is new again . Silkspan and dope is one of the earliest forms of model covering . Easy and fast to do , try colored tissue for trim instead of colored dope .

Mike 1484

[7car7]

Thought you might like some pics...

Here's the tail group I had trouble with, but now look great. Might be hard to see since they're black...
http://i127.photobucket.com/albums/p156/7car7/RC/RCPlanes10_27_07012.jpg

Here they are before covering, and also the wings wich are monokote with printed tissue put on with water based polyurethane. Really wish I'd re-done them with just tissue. Maybe someday I'll do that.
http://i127.photobucket.com/albums/p156/7car7/RC/RCPlanes10_27_07005.jpg

[sgtdirt]

very cool!!
what kit is that your building?
i like doing the printed tissue thing myself. i use doculam underneath and tissue over it. this works good because the tissue can be applied dry then sprayed with water. use an iron on low setting to get the wrinkles out. krylon clear or matte will seal the tissue too.

[speedy2]

Does anyone know how to make nitrate tautening dope ?

I can't seem to buy any and I know modellers used to make their own. I always used to buy it. I would like to make my own so I could control the ingrediants to adjust the amount of shrinkage. Basically I think it is cellulose ( Nitrate ) plastic desolved in acetone or some other thinner with other additives.

Anyone have any experience ?

Thanks,
Speedy2

[speedy2]

No problem, I have my Nitrate taughtening dope now.

[7car7]

very cool!!
what kit is that your building?


Thanks!
This is a Cedar Hobbies Albatros. They sell on ebay, and I guess also from their site.

[ezrydr]

"No problem, I have my Nitrate taughtening dope now."

Speedy, where or what did you wind up getting or using?

I make a cellulose nitrate laquer (for rocket engine ignitors as a pyrogen binder) by disolving cut up ping pong balls in acetone but I never thought of using on my airplanes. If its even the same thing as you are talking about.

Steve