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Silkspan and dope Questions. - 10/7/2009 3:43 AM   
Doc.316


 

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Status: offline 		Wow...I think I need help...got the "Jetco" supercruiser ready to cover. Read up a bunch on silk and dope/silkspan and dope....and decided to try it. I nitrate doped the structure around the edges (a couple of coats) then I wetted the silkspan and glued around the edges with nitrate dope pulling out the wrinkles then trimmed and really glued the edges well. Then I let it dry,....well partially dry (it hasn't been overnight but it seems pretty dry. The silkspan has taughtened some...but isn't "drum tight".

Ok, 1. Is it supposed to be drum tight at this point or is the dope coats supposed to taughten it up some more?
2. Am I being impatient...it should be better in the morning when it drys better.
3. Geeze, ya didn't do it right kiddo...pull off the covering and try again.
4. Yes it should be tighter but you can fix it like this.

Thanks, as old as I am (45) and this is the first open bay plane that I have tried to do silkspan on....the last for silkspan was when I was 15 and it was just a solid sided fuselage so any help will be appreciated. I just don't think I have the method down yet....(sigh). If I havta pull the covering off I will, whatever it takes to get a good finish (that is why I started with silkspan...it is pretty cheap).

Steve


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RE: Silkspan and dope Questions. - 10/7/2009 4:44 AM   
big max 1935


 

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From: huron s.d.
Status: offline 		Check it in the morning & as long as it is smooth with no wrinkles give it a coat of dope thinned 50 -50. I think you will find it will tighten up . After a couple of coats add a few drops of castor oil to keep it from getting too tight . Silkspan is about as easy as silk to work with . Good luck ,MAX H.

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RE: Silkspan and dope Questions. - 10/7/2009 12:21 PM   
pd1


 

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Status: offline 		It should shrink tight overnight.

If it doesn't you can use an atomizer to spray more water on it and let it shrink some more.
Silkspan and tisue are paper and shrink quite a bit.

Question, why silkspan ? Silk is a lot easier to use and sells for about $2 to $3 a yard.

http://www.dharmatrading.com/html/eng/3374-AA.shtml

#HS536 36" $2.65 This works real well.

Paul

Before water and after water.



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RE: Silkspan and dope Questions. - 10/8/2009 3:01 AM   
Doc.316


 

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Status: offline 		Whew, it shrank.....and ended up looking pretty good! The next morning it was tighter...but with another reshrink...all is good...not professional but a fairly decent amateur job...it should look good with color.

Well, I went with the silkspan because I am a impatient individual... ...they had tissue in the box and not knowing much about covering this way I figured I needed a easily obtainable source of covering and they had it at the local hobby shop....ok I was in a toot to get this thing covered and the silkspan was quicker....

Someone should have told me these fabrics relax and tighten when you dope them, it would have saved me some heartburn...(sigh).

I still have some more questions....
1. The castor is added as a plasticizer (sorry about the spelling) to keep it from shrinking too much and to make the covering not so brittle. I mix my own fuel so that can easily be obtained. Is this OK?
2. At the shop we have supercoat, and light coat. It seems like the lite coat shrinks less. Is this what I need?
3. The hobby shop has the colors I need (red and white). Do I need to add the castor to them also? This stuff seems a lot like painting a car (with laquer) so I was thinking I should spray a bunch of very light coats and let them eat into each other. Is this the way to do it?
4. How do I know when to start putting on the color?
5. Can I clear over the color (or do I need to?) for a final coat or will that cause the masked lines to melt into one another?

Thanks for your help, I am a little out of my comfort zone on this one. I have done a lot of fixing of the old equipment...(just built a rod for a spark ignition engine the other day) but really have no idea how to do this....

Steve

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RE: Silkspan and dope Questions. - 10/8/2009 3:52 AM   
wilddog


 

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Status: offline 		1,2,3 Yes,yes,yes. 4, the clear will get a gloss to it, takes about five coats, then apply color. For your first and second coat of clear, you can add baby powder to the clear to fill the paper faster. 5, never tried that.

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RE: Silkspan and dope Questions. - 10/8/2009 4:44 AM   
otrcman


 

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Status: offline 		Hi Doc,

Sounds like you are pretty much on the right track now. I'm assuming that when you say "supercoat", you're talking Sig products? If you use the Sig line of dope, you can mix or overcoat the butyrate products just fine. Clear over color shouldn't be a problem. But be careful with the nitrate dope, even if it is the same brand. You can use nitrate dope for the undercoats, but once you apply an overcoat of butyrate, then you have to keep using butyrate from then on.

The Sig "low shrink" clear butyrate and all of the colors work fine without additional plasticizer. Sig says these dopes are made from a low shrink base, whatever that is.

Will this be a glo fueled model or is it rubber band? The reason I ask is because the modern butyrate dopes don't seem to be as highly fuel proof as they were in years gone by. In areas where exhaust or raw fuel will be getting on the model, it helps to apply a final coat of some kind of highly fuel proof clear. Some folks have mentioned spray can polyurethane clear like you buy in a hardware store. But I haven't had much luck with the brands I've tried. My current final coat is a two-part polyurethane used on full scale airplanes, called Stits Aerothane. But you have to buy a quart of that stuff and it's pretty expensive. I understand Klass Kote clear (advertised in the model mags) does just as well for a lot less money.

Dick Fischer

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RE: Silkspan and dope Questions. - 10/8/2009 6:24 AM   
Doc.316


 

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Status: offline 		Yes, it is a single channel model with a McCoy .049 so it is glow fuel powered. Yea, the (few) products we have around here are sig products. They carry it in quarts (sigh) so I am going to end up being kind of expensive (thinking $20 apiece for the colors (2), and then the clear, nitrate, and thinner....wow!) Oh, well I have some left over for another project.

I apprectiate the help, it really doesn't seem to be too hard so far. The only complaint is the from the wife about the smell. It is pretty amazing she can smell it since the shop is hooked up to the garage with a door and then the garage is hooked up to the house with a door and somehow the smell makes it to the kitchen....I told her I could be working in the basement....

Thanks again for the help, I will probably ask more questions when I get farther along in the process.

Steve

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RE: Silkspan and dope Questions. - 10/8/2009 12:11 PM   
pd1


 

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Status: offline 		Fill the silkspan with thinned clear until it remains shiny after the dope is dry, then it is ready for color.
The more the silkspan is filled with clear, the less color you will need.

If the silkspan isn't completely saturated, the silkspan will soak up the color like a sponge.
Don't be tempted to use full strength dope, thin it 50%. You will get a better finish with the thinned dope.

I only brush the clear on, I'll spray the color though.

After 3 or 4 coats of dope it can usually be sanded with 300 to 400 sandpaper.
Be careful at the juncture of structure to open areas. The sandpaper tends to cut through at the edges of the wood.

Personally I only use plasticiser for the last coat or two of dope.
That's just my preference.
Castor oil work well as a plasticiser.

Clear can be added at any time over the color. When adding trim, I tape the outline and give the area to be painted a coat of clear.
This will keep the trim color from bleeding under the tape and keeps the tape from lifting.

Clear can be added as a final topcoat too, it helps make the plane shine and as you said, melts the edges of the trim.

Paul

First plane is yellow tissue with color trim. These are all doped, first three silk, rear two tissue.

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RE: Silkspan and dope Questions. - 10/8/2009 4:53 PM   
HighPlains


 

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Status: online 		Minimaster, Aeromaster, Trainermaster right?
Is the Shoestring the Dare kit?

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RE: Silkspan and dope Questions. - 10/8/2009 5:52 PM   
pd1


 

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quote:

ORIGINAL: HighPlains

Minimaster, Aeromaster, Trainermaster right?
Is the Shoestring the Dare kit?


Correct on all.
But you forgot the Sparky and the Roaring 20.


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RE: Silkspan and dope Questions. - 10/10/2009 8:49 PM   
Doc.316


 

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Status: offline 		Well, it is almost covered, whew! I have a few light coats on her and all is going pretty well (I think). So what do I do about the "windows"? The plans show the windows going on after the covering....but they paint them with the same color as the model.

So I have another question (sigh) seems like I have been asking a lot during this ordeal. Does the dope eat the windshield? Can I lightly sand the edge of the windshield, glue her on, mask and then shoot the edges of the windshield when I am shooting the rest of the color?

Thanks for your time,

Steve

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RE: Silkspan and dope Questions. - 10/11/2009 3:43 AM   
otrcman


 

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quote:

ORIGINAL: Doc.316

Does the dope eat the windshield? Can I lightly sand the edge of the windshield, glue her on, mask and then shoot the edges of the windshield when I am shooting the rest of the color?

Thanks for your time,

Steve



Hmmm. There seem to be several different window materials. What exactly you have is hard to know. To be sure of compatibility, it would be safest to test a sample before doing it on the airplane. Some of the window material is referred to as "butyrate plastic", so that should be OK. Sometimes you can get away with minor incompatibility by holding your airbrush way back and just fogging on a few dry coats. That way there is very little paint solvent to attack the window.

Backup plan: Make a template of the window before you glue it into place. That way, it's easier to make the replacement if things go wrong.

Dick

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RE: Silkspan and dope Questions. - 10/13/2009 1:20 AM   
Jim Thomerson



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Status: offline 		On sanding the silkspan on your wings, use steel wool. It is safer, as it is easy to cut through at the ribs with sandpaper. Go over the wing with a magnet after you use the steel wool.

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RE: Silkspan and dope Questions. - 10/13/2009 5:06 AM   
Doc.316


 

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Status: offline 		Excellent idea Jim. Wish I'd known about it earlier....(sigh)...had to fix one sand through even though I was trying to be very carefull. I will try that on the fuselage and tail. I am taking my time on this trying different methods (there seems to be a bunch) to see what I like best. The wing ended up looking useable...actually better than I thought it would. The red covers up a lot of the messups pretty well. Now the white I shot on the fuselage is like white primer...I need to do a bunch more sanding/filling/sandings....but I can see the end of the road.
Thanks for the ideas everyone...

Steve

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RE: Silkspan and dope Questions. - 10/14/2009 7:00 AM   
deckape


 

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steve use Butraite Dope in short time it will be drum tight, Dont over use it or it will cause warps in time. I know this from experience I use use to much on my free flight rubber jobs turns exlent models into prezzels. for drum tight use it spiringly Nitraite dopes dont tighten up you really have to pre shrink your tissue and pull it tight before dopeing useing nitraite dopes.

My own two cents Sir

Franklyn

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RE: Silkspan and dope Questions. - 10/14/2009 10:38 AM   
Phlip



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Status: offline 		One of the things I've always loved about silkspan is that patches can be invisible. If you tear out a patch from new silkspan (as opposed to cutting it out with scissors) when you dope it down, the edges disappear. You can then paint it the same as the rest of the plane and nobody knows that there was a patch!

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RE: Silkspan and dope Questions. - 10/16/2009 4:32 AM   
Doc.316


 

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Status: offline 		Ok, the white dope is on....and also the red trim....where the silkspan was put on looks well it looks pretty good for an amateur.....but (there is always a but isn't there) the cowl looks like er (bad...really bad). It basically crazed. The cowl looks like abs plastic and I had my doubts about it (I even considered carving out a wood one) but I thought well it must be compatable with dope since that is what everyone covered with back in the day. What is interesting is that I sprayed it with white first (yes it was buterate dope) and all was well (maybe this mix was more thinner than the white heck I can't tell ya what the mix was).

So my plan is to let it dry...lightly sand it and spray on a bunch of very light layers ....and sand lightly between and try to get the thinner to flash off before it melts down into the layer laid before....Is this the way to go on this thing?

I guess I learned something...lol.

Steve

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RE: Silkspan and dope Questions. - 10/16/2009 12:20 PM   
pd1


 

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Status: offline 		No guarantees on this but sometimes the clear dope will have less effect than the color.
Sand as much of the paint off as possible where it has reacted first.
I would try a thinned coat of clear and sand then thinned color as you suggested.
You shouldn't need much paint, you just want to color the plastic piece.
Let each coat dry thoroughly before the next coat of paint.

Good luck
Paul


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RE: Silkspan and dope Questions. - 10/16/2009 3:56 PM   
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Status: offline 		Dang, I hate it when that happens.

One other approach to doping the cowl would be to put some kind of barrier coat between the plastic and the dope. Epoxy comes to mind, as it is a lot less aggressive than the dope. One downside to non-soluble finishes like epoxy is that the dope has a hard time biting in for adhesion. To solve the adhesion problem you can spray on a coat of epoxy and then follow up with a coat of dope just as the epoxy becomes tacky. Let that cure, and then subsequent coats of dope will adhere well to the dope undercoat.

How did you like the Jetco kit, Steve ? I have a Navigator kit which sends conflicting messages. One side of me wants to build it, while the other side thinks it's really neat in the box just as it is.

Dick

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RE: Silkspan and dope Questions. - 10/17/2009 12:10 AM   
otrcman


 

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Status: offline 		I'm usually a slow thinker. Sometimes REALLY slow. Mulling over your crazing problem I got to wondering whether it's a chemical incompatibility or simple lack of adhesion. If you tried painting dope directly onto metal, it would shrink up and peel because the dope couldn't stick to the metal. Maybe that's what is happening on your cowl. Is the plastic surface wrinkled or showing damage in any way? If the plastic looks pristine, them maybe all you need is a primer coat that bites into the plastic and is compatible with dope.

Dick Fischer

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RE: Silkspan and dope Questions. - 10/17/2009 2:48 AM   
Doc.316


 

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Status: offline 		Well, I let it dry. it seems like the abs (or whatever it is) seems to be getting softened by the thinner. So what I did was sand it off, then I put some dope out on a plate and let it thicken up while I ran some engines, then I brushed on a coat. It seems to have gone on without messing up stuff. So the next idea is to let it dry well, then brush on another coat or two then sand lightly and try to smooth it out without thining the previous coats much....then start spraying a light coat on it and let it dry well. If this doesn't work then I will sand it off and go with a sealer coat of finishing resin.

I like the Jetco kit (in fact I have been looking for a Cessna to build). It is very buildy compared to a kit from the 70's like I am used to (something like a commander or kadet or even the Kadet Sr). It is really a marvel of engineering with wood with all the pieces fiting together like a puzzle. It is a good change of pace of what I have been building lately(you might see a stuka, ultimate, or delta in the background)...I have got to admit that it sure seemed like something was missing when I installed the radio...it just didn't look right with one servo in there....

It has been a learning experience that I have enjoyed....and I have learned to appreciate what modelers of the 50's and 60's had to go through to build one of these things (even thought I have to admit I DID use ca and not the dryed up 5c model cement). I got a couple of pictures of the parts that look ok for an amateur I will post as soon as can get the cord from the wife.
Steve

Steve

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