dmcmike

My Feedback: (14)

After recently deciding to finish a Great Planes Giant Aeromaster using the old Silk and Dope method, I started to look around the web for any 'tips' and found very few sources. If there's any interest, I'll go ahead and document my trials, tribulations, and hopefully triumph! Bear with me, as I haven't done this for about 20 years or so, but had pretty good luck with it back then.

To start off, we need some silk to put on the frame, so I checked out www.thaisilks.com and ordered 10 yards of 8mm Habotai Silk last Monday. It arrived today.

Right after ordering the silk, I phoned Brodak and after talking to John Brodak for a few minutes to determine what I was going to need for supplies, I ordered 16oz of Clear Butyrate, White primer, Thinner, Insignia Red and Insignia Black Butyrate. Basic finish will be overall White, with Black and Red trim, much like kit box.

Since I don't have access to an Air compressor, this one will be a brush job. Just got to thin the dope so it flows well.

Now the work starts. Before I get going on laying any silk on the frame, I'm going to hit it with the lightweight filler in the 'dings' and then start sanding for the next day or two.

I'll get some pics up here sometime soon! Gonna have to clean up the shop too!

mcmike

BobHH

My Feedback: (18)

MCmike, I purchased some of the Tai silk for some projects. I had some trouble getting it to tighten up correctly. It Finally, after about 5 coats of dope it began to tighten. Strangely I have some older Sig silk that tightened up good after one coat but the Tai stuff took several coats. Not sure if it is the weight or the die that may have caused it. Unfortunately the weight came out a bit heavier than I wanted. You may want to do a test run to see if you have the same problem. I have about 5 yards of gold and purple from Tai I don't have much use for unless I can find a way to tighten it up with less coats. I make try the Randolph dope next. I was using Sig Butyrate on my project. I would be curious how yours turns out. Over 3/4 of my models are silked and doped. The only way to cover!!!!

Bob Harris

RCPAUL

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This would be great!

Paul

dmcmike

My Feedback: (14)

Bob,

I know some silks are treated, and that the treatment has to be gently washed out before you cover with it, or it won't shrink properly. I'm going to do that with my covering tonight. Not sure what to use, but i'm going to take a couple of samples, and wash one in Woolite, "For Fine Washables", and one in some dishwashing detergent. After that, i'm going to cover a couple of test 'frames' and see how it goes. Using the Brodak dope, which as John Brodak told me is made by Randolph to his specifications, so it should be a good comparison to the Randolph product.

mcmike

Jim Thomerson

I think you will need a bunch more clear dope and thinner.. I've not used the Thai silk but rather the old Esaki, etc. (I have yard packs that sold for $2.95, and up).. I like your idea of washing the silk and doing test panels. I would suggest you dope your framework until it is shiny and put the silk on quite wet. Get it as tight and smooth as you can. Stick the silk down with thinner or very thin dope. It will blush but this will go away with subsequent doping when dry. When I want a translucent covering, I first brush very thin dope, so run throughs aren't that noticeable. As I dope along, I use progressively thicker dope.Once the grain is filled, no pinholes, I am doping on a surface, no run through.

dmcmike

My Feedback: (14)

Not to worry... it's going on wet!

guess I ought to ouline what i'm going to do...

1) fill and sand the airframe until all blemishes are gone
2) Apply 2 coats of clear butyrate (thinned until it flows well) to airframe, sanding between coats.
3) apply silk (wet) with thinned butyrate on just the frame, not the open areas (yet!).
4) After the silk has dried, apply 2 coats of thinned butyrate over the entire surface. I use an old trick of keeping the surface i'm doping perpendicular to the floor, so the dope will not 'puddle' on the inside surface.
5) light sanding after the clear, see if I need any more.
6) 2 coats of white primer - sanding about 90% of this off between coats. I'll use this primer to fill the grain of the silk. I got this as advice from John Brodak. He tells me it works better for him than sanding sealer, and gives a great surface for the final color coats.
7) after i've got the grain filled, or very close to it. apply 2 coats of insignia white color , 400 grit between coats. I'll reevaluate the need for more coats after the second is on.
8) mask and paint trim probably 2 coats
9) do a final sanding with 600 to 800 grit, just to get it nice....
10) final 2 coats of clear
we'll see what it looks like after that...

I may cut back on some of the primer coat if it looks like i'm putting too much weight into the finish. I don't want a great looking static display model that weighs too much to fly well.....

And if anyone wants to offer advice, please, give it! Like I said, it's been a Long time since i've done this.

mcmike

Chip_Mull

My Feedback: (1)

Before you order Randolph dope, be sure you know what to order. A lesson in dope is probably in order first. All dope shrinks! Even "Non-tautening dope" shrinks, just not as much. Most dope today is manufactured to be applied to polyester fabric which is heat shrunk. What you are trying to achieve with nitrate dope and then butyrate dope is the chemical bond like Poly tone has. That's why you apply Nitrate dope then Butyrate dope. Most dyed in the wool dope guys apply 10 coats of each before even getting to the color.

Now, for silk, Nitrate us obviously unnecessary. What you will need is "Tautening Dope" or Randolph 9701 Tautening Butyrate Dope (Clear). If the silk didn't tighten as much as you wanted, it may have been the dope. Just because it says "Butyrate" doesn't mean they are all the same.

I don't know what Brodak specifies in his "Specifications" for the dope are but I would be sure to ask is it tautening or non-tautening. Generally, the colored dope is non-tautening Butyrate but, we can tint the 9701 Clear dope also. By the way, Poly Fiber bought Randolph several years ago and all Poly Tone Dealers now blend their own colors. We are also Randolph Dealers and can blend Randolph to the Poly Tone color card or Randolph color card.

Just for your edification, we also sell a dope which has talc in it for sanding. The Rand-O- Fill silver has talc and aluminum in it.

For more information contact Stitspolyfiber @ [email protected] or call 817-279-8045.

LesUyeda

Nitrate and Butyrate dopes: both come in taughtening and non taughtening flavors.

Nitrate sticks to about anything, and you can put almost anything over it. It is not fuel proof.

Butyrate dope is fuel proof, but you cannot put anything over it except butyrate.

Neither Sig nor Aerogloss is true butyrate dope, they are some strange formulation, that resembles the original. You must use their thinner with them, and their thinner eats anything that I have tried to use for masking. I ended up throwing away all that I had.

I used Thai colored silk on a small airplane, and had the same problem with poor shrinkage, BUT eventually everything shrank up just fine with no additional dope, just time.

Les

HighPlains

My Feedback: (1)

A question about silk. Can I dye it before using it? I would like to do a translucent Red silk job, but only have white silk (35 year old yard packages). Or do you add a bit of color to the clear dope after it's covered?

I would like to do the model (Falcon 56) pretty much as the box art, so it would also be color doped on the nose, and leading edges.

BWooster

But nitrate is lighter and easier to use. So use it until you are ready for colour. (oops - color)

dmcmike

My Feedback: (14)

You can dye it without too much trouble, prior to putting it on the plane. I've read on the net that better results are had with liquid dye, rather than the powdered RIT dye. Dig around on some of the CL sites, you'll find some information there on Dying your fabric.

In the past, during the 'pre-monokote period' (yes there was such a time) I always used Butyrate for everything. Never had any trouble at all with it shrinking up the covering, whether it was silkspan on my CL stuff, or Silk on the RC. I've always put the covering material on wet, and let the moisture do a lot of the initial shrinking of the material. Yes, it was Aero-Gloss dope back then mosf the time, usually straight out of the can for the clear. I had tried a couple of others, including Randolph, and noticed that the Aero-gloss never did shrink as 'quickly' as the others, but eventually did a fine job. Never used Nitrate, simply because it wasn't fuel-proof , and i didn't want to mess with adding a fuel proofer to it, same as now. I'll just go with the dope I know, at least on the Frames. I might pick some nitrate up for one of the frames, to see if it makes much of a difference. I've still got a Nobler built in 1970, and a Flite Streak built in '69. Covering is as bright as ever, tight as ever, and still looks good.

The Silk came in Yesterday from Thaisilks. Nice stuff! I almost had to wrestle it away from the Wife! Looks like it's going to be the right weight at 8mm. I ordered 10 yards of the 54" wide material, and after looking it over, there are virtually no flaws in the fabric at all!

Just waiting for the care package from Brodak with the balance of the covering materials, then it's off to work.

I'm working on doing a final check of the airframe this weekend, filling any dings and sanding everything. Started off with 150 grit, moving to 200-250 this evening. Starting to look pretty good!

mcmike

Chip_Mull

My Feedback: (1)

You don't need the nitrate with silk. I only mentioned it for the guys using polyesters (Sig Koverall, Stits Lite and such). Butyrate sticks to nitrate, that's why we use it, what they don't tell you is the intermediate product recommended by Randolph ( Rand-O-Proof, G-6302) is half nitrate and half butyrate. Again, trying to achieve that chemical bond Poly Tone has.

When Piper produced the first Cubs, EVERYTHING was painted with Butyrate. That's why we have two different original Yellows for Cubs, pre-war and post-war yellow.

Wherever you order the dope, order their thinner 'cause it's all different. I noticed you are going to brush the dope instead of spraying. Do yourself a favor and buy a good quality camel hair brush. Preferably a couple of different sizes and the best you can afford. It will make a huge difference in the final finish.

Good luck and please post pics.

dmcmike

My Feedback: (14)

You must be psychic! I ordered the Brodak Thinner along with the dope, and 4 different sized camel hair brushes. Should have everything I need!

I do have one question... I've read that some silk comes with a 'sizing' that needs to be washed out before you use it. Any recommendations on what to use to do that? How do you tell if you need to?

thanks!
mcmike

LesUyeda

I am told that the sizing is to help it keep its shape whilst sewing, and that it can be washed out just as you would wash any silk. I did not, with the colored Thai that I used.

Les

Chip_Mull

My Feedback: (1)

I would be more worried about damaging the silk from washing and handling it than the sizing. Sizing is a lubricant used on the threads for weaving. When purchasing fabrics for aircraft we are looking for several things. Two of which are sizing that is compatible with our paints and "Griege goods" or polyester that has not been over a steam bar. We are looking for basically virgin material with nothing done to it. That gives us maximum shrink and compatibility.

Remember when you wet it and it dries, it shrinks. There goes your first shrink, so to speak.

I really doubt that the Thai silk you are purchasing has any sizing in it. A simple phone call or e-mail could answer this. Call the people you purchased it from.

This is one of the main reasons we do not recommend lining material from dress shops to cover your models. it's usually pre-shrunk and you have no idea what kind if any sizing is used. The fabric is the cheapest component in the whole process. Rarely is the fabric the culprit for adding excess weight on an aircraft. It's usually the paint/process used.

In this case I wouldn't worry about sizing.

dmcmike

My Feedback: (14)

thanks Chip!

I'm thinking the same as you, don't want to lose that first "shrink"! I'm going to give them a call on Monday, but from what i've read on their website, it is 'virgin' silk, i.e. nothing done to it since weaving.

Right now... I think i've got balsa dust in every orfice! that's a big airplane to sand! But we're getting there... I'll post pictures of the 'Victem' in the bones Monday night.

Particulars on the airplane:

Giant Aeromaster from the Kit
7 Hitec 5945's - 2 on elevator, 1 each on 4 ailerons, 1 on rudder (although i'm thinking about putting another on it)
Rudder and Elevator servos in the tail.
1 futaba s3004 on throttle, 1 on choke, if I put a servo on the choke...
G62 with Bennett mount, Pro-Zinger 22x10
Futaba Radio
(2) 2600 mah Ni-Mh batteries
Haven't decided on whether on not to put smoke in it... not much room for the tank and pump!
I've built it pretty much stock, except added 1" to each elevator and 1 1/2" to the rudder

da50ex

Great info here, in answer to the original question, yes, i would be interested. I'm going to be building a Sterling Stnson Reliant and want to use dope and fabric as I have difficulty with the shrink on stuff. I haven't used dope & fabric though in over 30 years and could use a refresher
Thanks
John

Chip_Mull

My Feedback: (1)

To da50x:
I would only and I stress ONLY use silk on a park flyer or something less than 40 sized. Most people have the misconception that the fabric is where the weight is when covering and painting a model. Paint alone is responsible for most of the weight or better yet the paint "system" used. If you're thinking of the 80" Stinson Reliant, use one of the polyester fabrics available. They are all ("They" being polyesters sold for modelers) in the range of about 1 to 1.2 ounces per square yard. That's about 3 ounces of actual fabric used on the Stinson.
Rather than being concerned about the weight, I would be more concerned with the denier or "tightness" of the weave. A lighter fabric but looser weave takes more coats of paint to fill the weave.

I have comparisons available for full scale and models and it boils down to: 1. any two-part system or paint is heavier. 2. between the solvent based systems/paint, dope is heavier than the Poly Tone system. On a full scale Piper Super Cub you save over 30 pounds with Poly Tone paint.

Polyester gives you a stronger more durable aircraft and Poly Tone gives you a lighter paint. It takes more coats of dope to accomplish the same thing. As an example, we sell both Randolph Dope and the Poly Tone system for full scale aircraft and modelers. I sell 10 times more Poly Tone paint than I do Randolph Dope. We have now begun mixing Poly Tone paint in the Randolph colors by demand. It's just simply a lighter, better system.

Silk and Grade A linen was great when it was all we had. We are now in the 21st Century. Paint has changed and fabrics have changed a lot. Remember two things when deciding to paint. You have a lot of time and money invested in this work of art to get it to this stage. Every model out there is a work of art in the raw. Don't rush this stage of model building. Do your planning and research.

Secondly, when you finish with the paint job you seldom see what is underneath the paint. Why let that ruin a perfectly planned paint scheme by using something that has the potential to split, chip, wrinkle or let go when you least expect it? There are products available that have been developed from the full scale industry and have been tested in both the sport and contest circuit. The full scale industry has developed these techniques over the last hundred years and over the last 30 years have refined it to a science. Use it! Us modelers don't have to re-invent the wheel (paint in this case).

One other piece of advice. Whatever system you start with, stick with it. Don't change systems after the first coat, they may not be compatible. Ray Stits used to say "We can put a quality product in the can but we can't but craftsmanship in a can". He also used to say " We have builders and inventors. The builders read and follow instructions. The inventors think they know more than the manufacturer."

Sorry about the long diatribe here. It's just something I deal with on a technical level every day.

dmcmike

My Feedback: (14)

ok... thanks for the diatribe. Not doubting your remarks or familiarity with the product at all, but I gotta disagree on using "silk only on a park flyer or something less than 40 sized". I've seen a lot of airplanes up to 1/3 scale covered with silk and dope. I decided to go that way simply because I've used in the past, long past maybe, but past. Who knows... I may regret it, and wind up ripping it all off and recovering, but I doubt it. BTW, the silk I've purchased is listed as 8mm, while the silk that has been used in the past for modeling is a bit lighter at 5mm.

Anyways, since I've already spent the money on the silk, and have the dope on the way, I thought I'd introduce you to our victem, er... Subject! It's a Lot of Lumber!





Was running out of light, so I didn't have time to stick the surfaces on it, but you get the general idea.

Haven't had a chance to get an accurate weight on her yet, but plan to get all the equipment aboard, servos, batteries, receiver, engine, etc... then get an accurate 'Before' and 'After' weight, just for fun.

Now, if UPS ever gets here with the dope, we'll start!

Chip_Mull

My Feedback: (1)

MCKIKE that is a lot of lumber. The ribs almost look scale. How long have you worked on it up to this point?

dmcmike

My Feedback: (14)

total time for construction, maybe 3 months on and off. It's really a good kit, if you can find one.. What's not evident from the pictures is the pound of so of extra wood that i took out of it! It's basically an oversized .60 model, same type of structure, etc. so a lot can be done to make it lighter. Ribs are simply die-cut, with capstrips. Yes, it's a lot of lumber, but anyone who's ever built a kit could do it without much trouble.

Hopefully, the UPS guy shows up today with the balance of the supplies and I can get on with the covering!

da50ex

Chip,
The Stinson I'm building is a small one, 57" wing designed for a .40 size engine. Kitted by Sterling models a long time ago. The kit is intact and in excellent condition. a little yellowing around the edges of the plans though. I plan on putting a 70 - 82 4 stroke in it, so i'm not too concerned about weight. Back in the days when i was active and my father before that, all we did was go to the LHS and buy some silk and dope and put it on. There wasn't a lot of choices like you have now i guess. I'm in no way an expert builder, but I have the advantage of learning the craft from my dad years ago. My models are good 10 footers, but when i try to use any shrink covering, they get to be more like 30 footers! I won't have time to even start this kit for a few weeks yet, but hope it comes out half as nice as MCMIKE's

dmcmike

My Feedback: (14)

I've managed to get started covering the Rudder and Elevators. Got 2 coats on the frame, lightly sanded with 400 grit between coats. Then cut the silk with about 1 to 1 1/2" to spare all around. Wet the silk with lukewarm water, and laid it out, getting all the wrinkles out. then with a 50-50 thinner, clear butyrate, went around the outside edges of the framework, working the dope in with both a brush, and my fingers. I've found that lightly rubbing in the dope get's it take a "set" pretty quickly. I worked quickly so that the silk wouldn't get too dried out. Once I had the edges doped on, i started laying the silk over the sides, cutting it at the corners, ala monokote. Again working my way around with both the brush and my fingers. So far, so good! Here's a couple of pics of my progress.







now, i'll just let the first side dry for an hour or so, then go back and do the other side of the panels.

Jim Thomerson

Not the thing to do. Easy way to build in a warp. You should cover both sides and keep both sides moist until you finish. Then set the part vertical so that both sides dry at the same rate. your structure is so heavy you probably won't have any trouble, but it is still not a good practice.

dmcmike

My Feedback: (14)

i'm not worried about warping this structure at all... and so far, things have gone very well, but you're correct about covering both sides on lighter weight frames. Had to do that all the time when building CL stunters.