How do I cover with Silk?
 

I've had a 70" Playboy SR kit for a while and hope to get to it later this year. It'll be an R/C Assist and fly with a TT GP-40 engine.

While I was at the WRAM show this year, I saw a beautiful Mercury covered in silk done by Jon B Shereshaw. I think John actually designed the Mercury somewhere around 1938. You can see this plane at http://www.wram.org/pages/VINTAGE%20R-C_png.htm.

Anyway, I was going to cover the plane with opaque and transparent film, but after seeing that plane, I'm starting to change my mind. Jon's plane sort of inspired me.

Everyone that I've asked has preached doom and gloom about covering with silk. Too heavy. Too much smell. Too much work.

Can someone tell me more about covering in silk (what weight to use, how do I fill the weave? How about coloring it?) Is there a site somewhere on the web that will give me honest answers to these questions?

Thanks,

Bob

RE: How do I cover with Silk?
 

For a complete explanation of how to cover with silk see the October, 1993 issue of Model Aviation

RE: How do I cover with Silk?
 

Do a search within RCU and you will find all the answers you need.

RE: How do I cover with Silk?
 

I have switched from plastic , iron on coverings to fabric and dope. I use polyester instead of silk though but it is intsalled the same way. I find it easier to do than iron on stuff. It is lighter than ultracoat too. It is not a one step porcess though like ultracoat. It takes many steps and many layers of dope and paint. I like it because it is forgiving. If you find you need to change something after it is installed (before painting) you can do it with no damage to the fabric or airframe.The Polyester is $1 a yard at a fabric store.

RE: How do I cover with Silk?
 

Thanks for the advice so far, I'll look up that info in MA. But I have a few questions for all of you if you have a minute....

As far as a search within RCU, there were so many hits that I couldn't pin anything concrete down as to techniques, such as a Step 1; Step 2; ... etc.

Mike Denest, I went to the vintagercsociety.org site. It's an interesting site, but I noticed that the Playboy SR isn't listed. I'm wondering if this was an oversite or if this Joe Eglin 1938 design doesn't qualify. Are there any links on the site pointing to finishing techniques? Thanks for the site. It'll make for interesting reading.

Regarding the Polyester, does it shrink (I thought I'd read somewhere that it would shrink with a heat gun)? If I remember correctly, silk is applied wet and shrinks as it dries. I don't think that polyester does that, being a synthetic. But, that's still good to know... Thanks.

I presume that the finish is applied with a spray gun instead of a brush to keep from brushing too much of the dope 'through' the silk and creating added and unnecessary weight. Is that true?

How about dying the material for getting the color(s) you want?

Thanks for the info so far. Any more suggestions???

Bob

RE: How do I cover with Silk?
 

Silk isn't easy like iron on coverings, but it's not impossible, either. It just takes a little practice and a lot of patience. It wouldn't hurt to try it out on a practice framework before you tackle your Playboy, jut to get the feel of it.
I bought silk from The Silk Connection at something like $2.00 per yard and dyed it with Rit dye and it worked very well. There are some details of this in a thread titled "Cheap Silk" in this forum.
If you've ever covered with tissue or silkspan and dope, it's something like that, except it's done wet, and a quarter of a yard of wet silk can be a little tough to handle...but if I can do it, you can do it! Nothing else looks quite right on an old timer!

RE: How do I cover with Silk?
 

Bob, If you are building a 70" Playboy it is scaled down Sr. or a scaled up Baby or Jr. as the Sr. is a 80" wing . It is SAM legal. Had a 80" one a few years back with a K&B rear exhaust .21 in it , plenty of power a .40 may be too much . With silk you need to look out for excessive shrinking & warps, use low shrink dope or add a few drops of Castor oil to it. This will probably sound nuts to you but the first coat of dope I put on is un-thinned & I brush it on through a piece of old "T" shirt , pulling it over the silk as I keep the shirt soaked with dope, it will fill the silk with out drops on the inside . JUST KEEP MOVING, let it dry good , hit the fuzzes lightly with some old fine sandpaper then add thinned coats until you are either happy or goofy.

RE: How do I cover with Silk?
 

HI Big Max,
Thanks for the tip. It sounds like a good one...

Mine is a full sized Playboy SR (O'Reilly plans & short kit). Maybe I was off on the wing span. Perhaps it's 78".. but it's a full scale job, anyway.

Weight is my concern, like anyone else's. I'd heard that brushing the dope on could lead to 'puddles' on the underside of the silk that do nothing but add weight. Thanks for that tip...

I know that this sounds wacky, but I "thought" I remembered something about using gelatin as some kind of filler, just to prevent that. Is that true? Has anyone heard of that?

Or have I been nipping at the cooking sherry too much?

Thanks,

Bob

RE: How do I cover with Silk?
 

A buddy of mine that has done a LOT of silk work on his old time FF's has told me quite a few hints that I've passed on below.

First off he does not cover wet, unlike most advice. He says he found that it tended to dry too quickly and would pucker as it dried. But of course keeping a mister handy and using it generously would help with that. His models are all in the 6 foot span range so there's quite a bit of work and I can see the covering drying too fast. Anyway he prefers to cover dry and taught and rely on the dope to do the shrinking. To avoid those puckers he also does not water spray after.

In getting the silk stretched out so it's fairly taught he also works the weave to keep it nicely oriented with teh ribs and spars. This is mostly a craftsmanship factor but I can see that it would also help keep the shrinking in line with the frame and perhaps introduce less warps.

For doping he uses a foam brush and does not thin the dope too much. Sort of to a heavy cream consistency. The dope is layed on with a moderate touch and not worked back over at all. 3 coats like this produces a nice shine with just a little of the silk's grain telegraphing through.

Now for my own idea.....

I don't see why you could not "dope" the frame with Balsarite and then use an iron to adhere the silk just like a modern covering. I tend to like this idea myself as it lets you work at a more controlled pace. If you try this do be careful with trying to lift and move the silk. The stuff is fragile and may "run" if the fibers stick too well. Perhaps this can be controlled by using a very light heat for an initial tack and then a higher heat to bond it permanently. Anyone tried that?

And all this from a guy that has yet to open his first bag of silk. But I've got about 10 packs in the garage... :D

RE: How do I cover with Silk?
 

Bob,
The Playboy is a F/F design that was adapted to R/C and is eligible for competition in SAM events. VR/CS concentrates on the models originally designed for R/C. However early R/C experimenters may have used designs similar to the Playboy for their stability and load carrying ability. So, you will not see it on the aproved planes list but you will not be turned away from any VR/CS function because of it. You are welcome to fly as much as you like. Does this help?

RE: How do I cover with Silk?
 

I've never tried covering dry, but the silk certainly would be easier to handle that way on a large panel such as a Playboy wing. Having a mister handy is essential as the water evaporates quite quickly, especially in a heated room in the wintertime. I'm not sure how the dry fabric would handle compound curves, but it seems worth a try.

I've read about the unflavored gelatin trick but never tried it myself. Those dope dropletts are pesky, they'll show up after several coats if there are even a few unsealed pores left. I've sort of learned to live with them... a little unevenness in the color and transparency just proves it's really silk, doesn't it? ;)

RE: How do I cover with Silk?
 

Good info so far... Thanks a lot for all the input...

I have two issues though...

Les Uyeda sent me a private email but somehow I screwed up the reply and it came back to me... Les, if you read this, I'd like to get that .pdf article from you. I couldn't find your email address, sorry.

Also, to prevent the drips under the silk, is it possible to spray the dope on? I've never used a sprayer for this, but might be able to get access to one. I'm thinking that a spray gun would coat evenly and not let the excess dope 'bleed' through the silk.

Any thoughts on that? Am I making a correct assumption or would this all work against me?

Thanks,

Bob

RE: How do I cover with Silk?
 

I have done covering over open frames with polyester and dope. It is simple and easier than iron on covering but slower because it takes many steps to finish. I lay the dry polyester fabric on the doped and dried frame and soak it with a spray of water. After a few minutes it expands and I then pull out all the wrinkles and while still wet I brush thinner on the parimiter of the fabric and rub it in with a finger. It sets in less than a minute. Allow to dry (or use heat gun) and the polyester will shrink drum tight. I then brush many coats of nitrate dope thinned 50/50 . The frist few coats need to be very thin ones to avoid puddeling. Fuel proofing can be applied later. I build 80 inch span electric war planes so do not bother to fuel proof. There are many ways to cover planes . This is just how I do it with good results.

RE: How do I cover with Silk?
 

Mike Denest,
Thanks for clarifying that. I can see that Ed Kazmirski's Taurus is listed. That was a ground-breaker. I remember reading the original article way back when. The article had a lot of Ed's thoughts about airplane design and how to fly a pattern. I can see why the Playboy SR doesn't qualify...

RE: How do I cover with Silk?
 

I'm building a kit right now that is getting silk covered. It's an old Sig Liberty Sport biplane kit. So far I've got it all framed up and have started covering.
I'm using a bit of an unconventional silk covering method though (don't we all have our own little tricks? ;))

I covered the top wing with a different process that I'm trying for the first time. First I covered it with silkspan tissue. I like silkspan because it's so easy to work with and comes out perfectly wrinkle free. The silkspan got one coat of nitrate sprayed on, then lightly sanded with 1500grit to take the fuzz off.

Silkspan is just not strong enough though for a model this size. So I laminated a second layer of covering, this time a very lightweight silk (10g/sqyd). The silk was layed out dry over the silkspan, then sprayed with water and the wrinkles pulled out and doped down around the edges. The underlying silkspan wrinkled a little from the water but it all shrank up nice and tight when it dried. I sprayed two good wet coats of thinned nitrate over everything which bonded the silk layer perfectly to the silkspan.

The result is that the covering came out very light and 100% sealed in only three coats of dope. It is tight and strong, probably the best silk covering job I've done. I calculated the weight of the covering and the total weight increase was 30g for the whole wing.
With a top and bottom combined area of 840sqin this equates to a covering weight of only 1.6oz/sqyd.

This is a scale model and is going to get painted of course so weight will increase but the technique could be used for an ultralight covering for other models all on its own with a little tint added for translucent colors, or using dyed silk. I think I'll try that on my next old-timer model .

RE: How do I cover with Silk?
 

Bob. I got your first e-mail and sent the .pdf's Sunday morning. Apparently you never got them, so I sent them again today, twice:-)))) The first time today, I forgot to attach them.

If you try to spray on open frame silk, the air pressure will blow the dope right through the weave. Just ask me how I know.

Les

RE: How do I cover with Silk?
 

Silk covering? You must have just a touch of masochism. Seriously, in the 40’s and early 50’s I covered a lot of models with silk (including a Playboy). The advent of sheer nylon quickly replaced silk in most of the model community. Silk is fairly fragile, tends to run, and is more difficult to apply compared to nylon. On the other hand it is one of the lightest of fabric coverings, and when skillfully done results in an appearance like no other. It has always been relatively expensive, and we often used ladies silk scarves, which were cheap and about a yard square, for covering. We usually covered the print pattern with colored dope, but I remember one model in particular that had a black fuselage with white wings with a pattern of delicate roses.

When I returned to the hobby after many years, I built a Berkley Brigadier and not knowing any better covered it with silk. If you have never used tissue or fabric and dope for covering, I strongly recommend that you practice on some simpler frames before attempting the Playboy. There is a learning curve and some skill to be acquired before you can expect to do a good job. After the Brigadier, I discovered Sig Koverall, and that’s all I use now. It is slightly heavier than silk, and can’t be dyed. The weight difference isn’t much and I use dyed dope sprayed on to give a translucent finish rather than dying the fabric.

Don’t use Balsarite, Stix-It or other iron on adhesive to attach the silk to the frame. You will have a mess. Silk is too fragile and prone to fraying. Run through of the first coats on the backside is a fact of life, however using several thinned coats will minimize the problem. Thin coats don’t leave much solid when they dry, and the run through won’t be noticeable after the finish is complete.

The red airplane is the Brigadier with silk. The other one is covered with Koverall, the fuselage painted with color dope, and the wings and tail using dyed dope for the translucent effect. It is a small aircraft with an OS Max 10 for power, and the weight of the Koverall is insignificant.

RE: How do I cover with Silk?
 

That is a beautiful job and for a scale model is probably worth the trouble. However when you add the silkspan and silk you are a little heavier than Koverall, and there is no way it will be as strong. (Koverall is incredibly tough.) If you ever need to make repairs, I believe Koverall would be simpler. For covering R.C model airplanes, Koverall (or an equivalent polyester) is hard to beat.

RE: How do I cover with Silk?
 

Actually I don't find silk any more dificult than iron-ons because it is easy to move around whereas once you touch the film with a bit to much heat it shrinks and wrinkles. Silk is also,IMO superior to any other material for compound curves.

I have read of a method of applying the first coat by flowing it on with a strip of toilet paper moved slowly over the surface. This would be similar to the foam brush method. With any brush method put as little pressure as possible on the silk for the first few coats.

I have had good success with spray by misting on very light, almost dry coats till the pores seal. The dope dries quickly this way so it is not as slow as it sounds.

jess

RE: How do I cover with Silk?
 

I really can’t compare silk to iron-on covering since I’ve never used the iron-on stuff. Silk is very good over compound curves, however I’ve not had a problem with Koverall and compound curves. I like the heat shrink properties of the polyester covering. Silk is dependent to some extent on the shrinking of the dope. Prior to doping, silk is also more fragile and easily develops runs (ask you mother, or grandmother about silk stockings). As soon as sheer nylon became available I begun to use it instead of silk, and since discovering Koverall, I wouldn’t consider going back to silk. I find Koverall much easier to work with.

I think comments in this thread make too much of flow through. I’ve never had that much of a problem with flow through with silk. A few brushed, well thinned filler coats and there isn’t a problem.

RE: How do I cover with Silk?
 

Jess

I have to agree with you. IMHO covering with silk is easier than plastic covering. Now I said covering------painting is another story. Covered a lot of planes in the 50s and 60s, Live Wire Senior-- Live Wire Bipe--Smog Hogs -- Astro Hogs-- Orions -- you name it with silk and graduated to the new stuff, Monokote which was great. No more dope and smell.

I am now revisiting my youth and am in the process of covering a Debolt Live Wire Trainer with silk using Sig yellow and red. Expensive stuff but very high quality. Just had to give silk another try. Needless to say it is beautifull but as one guy said you have to be a masochist to do this.

I have to keep it simple so I dope the wood with 2 coats of thinned clear dope. Lay the silk on the area to be covered dry. Smooth out as best you can. Have enough overhang so you can stretch the silk. Spray a water mist and stretch tight. Spray more water so that the silk adheres to the wood. My silk at this point is very wet Make sure all the wrinkles are out of the silk where it touches the wood. Brush thinned dope on the wood surfaces and let dry. Of course while doing all this keep an eye on the grain of the silk to make sure it is straight.

I have sprayed and brushed. Both a pain but I hate to clean spray guns and brushing seems to accomplish the same thing--seal the weave of the silk and yes you get a lot of dope droplets and runs thru the silk but I don't think this can be prevented. I used an old Binks small gun in the early years and the overspray was substantal, Naybe the HVLP gun would help this. Painting a color, after the silk has been sealed with clear, would be better sprayed in order to get a good even coat.

Hope I haven't bored you old timers but had to add my 2 cents worth. What a fun hobby !!!

Jim Whitney

RE: How do I cover with Silk?
 

Try this site for using dope and silk. I've been going through a covering process on a very light framed WWI combat model. I don't like the "plastic stuff" because I don't like the unrealistic plastic look it gives. I've used fiber glass and epoxy resin on sheeted wings and fuselages and dope and silk on open framework. The issue I have with silk on a light frame is the shrinkage control. It tends to distort light construction. The polyester fabrics (Koverall etc.) at least gives me some control over shrinkage with the amount of heat used in the shrinking process. I have gravitated towards Koverall and StixIt. Works great on compound corners and seems to have a tighter weave than silk so pushing dope through the covering is less of a problem.

http://members.aol.com/GreenHawk/mid...feb98/silk.htm

RE: How do I cover with Silk?
 

Anybody ever try Polyspan? Supposed to be similar to silkspan but with polyester fibers instead. I haven't tried this stuff, but it is said to be quite strong and looks great once you've mastered the learning curve.

http://www.faimodelsupply.com/starline-polyspan.htm

Scott

RE: How do I cover with Silk?
 

The attached photo is a 1/2 A model with the wings and tail covered with Polyspan. It is quite similar to silkspan except it is heat shrinkable and much tougher. The model shown is about four years old and has seen a lot of flying, but so far no holes. It only comes in white so I put dye in the dope and sprayed the final coat for color. It looks just like silkspan. It is completely waterproof so there is no sagging in damp weather like silkspan. The downside of this is that it is not as easy to cover compound curves which are easily done with wet silkspan.

RE: How do I cover with Silk?
 

HI Guys,
I'm sorry this took so long to answer but I was finally able to get to my PC....

les, I got those .pdf files... Thank you very much. Like the first page of that article says, that is probably the best 'bible' that a beginner could have for learning to cover... and thanks for answering the question about the spray gun. I never thought of that...

I overwhelmed with all the answers here. Thanks! and keep them coming! There is some absolutely beautiful work out there to show off. And that trick about using silkspan underneatn the silk... I may not use that first time, but I will tuck it all away for later reference.

LouW, those are beautiful planes. to answer your question, I used silkspan years and years ago. Never used silk, but I used to be an upholsterer, so that might help things a little bit :-D I just might have a fuselage that I can cover to 'practice' on.

John, thanks for that alternate site. I just made a WORD file out of it and printed it out for the archives.

Thanks a lot every one. This is getting me inspired...

Keep up the chatter. I want to hear more!

Bob