If I cover my PT20 with silk from a fabric store and use dope ONLY around the edges to apply it, can I later use my iron to shrink it without any affects from the dope?

If I am lucky enough to find silk in the colors I want all I should need to do is apply it as mentioned above, then coat with a few coats of butyrate dope to fuelproof it. RIGHT???

Or would it be alot easier to use stix-it and an iron, then few coats of butyrate dope to fuelproof?

I prefer the dope method because the dope would hold it in place better as you iron it taute. IF you CAN iron over dope.

It has been a lot of years since I used silk and dope, but as I remember it, we got it wet with water, layed it over the frame work, used dope to stick it down around the edges and when the water dried, it shrank up nice and tight, we never used heat to shrink it, it was not needed. Back in the 60s, we even mixed Amboid glue with the Aero Gloss clear dope for the stick it down coat. Caused it to stick very well.

John

shd3920,

NOTE: Anyone can correct me if they can prove their correction.

No ..... you cannot ..... dope should not be heated with an iron because it destroys its long time self-shrinking characteristics.
Silk from a fabric store is not real silk unless labelled as such. It is a fabric treated to look like silk, feel like silk but is not made by the worms that produce genuine silk.
Genuine silk is very expensive .... example ... a small scarf 18" wide by 72" long is over $100.00 .

The strength of the fabric is destroyed by the treatment given to make it look and feel like silk.
Instead of silk from the fabric store I use a light polyester material or light Ceconite.

If you insist to use artificial silk from a fabric store, that is your choice. Good luck in finding a color sheme that you like, stripes, wave patterns, all kind of flowers. I have rarely seen this fabric in a single uniform color if you wish to make your own color scheme.

Using stix-it is fine but if you apply it to bare wood you will need two or three applicatons so that there is a thick enough layer of stix-it on the surface to grab the fabric solidly. The first application of stx-it will penetrate the wood if the wood is not sealed.

You can iron the dope if you wish to lose its good qualities but you should not; read above again.
Dope is self taughtening for ever.
[/quote]

Good luck with your project.

Zor

Just my 2 cents: This is a trainer and it WILL be abused. Even if you get it covered with the right kind of silk, it will not be good for repairing as will most likely be needed at some or many points in time. Silk is fragile and a lot of work to get it right is required...it is an art form really. I used it on rubber and flow free flight planes many eons ago. Just go with an iron on covering, use the coverite woven one if you want that silk woven appearance. You can work this stuff easier and then repair it easier too. These coverings are tougher than silk also. And a previous response was correct IMO...heat iron was not used to shrink the silk. After it was adhered to the frame with dope, it was lightly sprayed with water and allowed to dry and shrink at the same time. Only then do you find if you applied it well enough to avoid wrinkles all over the place. Jon

To perhaps correct a few of the myths.

There are 4 flavors of "dope"; Nitrate, taughtening & non taughtening. Butyrate, taughtening and non taughtening.

Nitrate sticks to almost anything, and you can put almost anything over it.

Butyrate does not stick well to most things, and the only thing you can reasonably put over butyrate, is butyrate, because butyrate continues to shrink; forever.

Aero Gloss is neither. It is some chemists dream mix that is easily manufacturable.

Real silk IS available from Thai silk, for a few dollars a yard, but is somewhat pre shrunk, so that should be considered when covering. (5mm Momme is what I use)

Les

http://www.airfieldmodels.com/inform...wing/index.htm

I get my silk from 'Dharma Trading' and it quite rasonably priced too. I buy 11yd bolts of habotai, either 5 or 7mm, and usually pay about $3.50yd. As Zor has stated you need to use stixit or similar, and usually 2-3 good coats before covering. If needed I then give then give the covering a light misting of clean water to tighten, just enough to dampen but not saturate. The habotai from dharma shrinks both ways, from memory its 8 and 5%. I then usually use a fabric sealer, and then finish with auto acrylics.
I dont think personally that I would go to the trouble of doing a trainer that way, unless its to get the feel of using silk covering specifically

Thank you for your responses. I think I will stick to the silkspan and dope finish.
What paint would you recommend?
And what can I use after butyrate dope to seal and fuelproof the finish, and stop the constant shrinking caused by the dope?
Or could I use something instead of butyrate dope to apply the silkspan?

maukaonyx (and readers),

Just my 1/2 cents .

I certainly agree that as a trainer it will be abused.
That is a very good reason to be well glued with "glue fillets" and covered with light but strong fabric to minimize damages in a crash.

I do not know about "the right kind of silk". Silk is either genuine or its appearance and touch is artificially created by manufacturing processes.

I am convinced that whenever it is stated that silk is weak is because artificial silk was being used. The manufacaturng process destroys the fabric filaments to give it that smooth touch and sheen andloose the filaments strength.

Genuine silk from the worms is very strong. It has one of the highest strength to weight ratio.
In the old days, women could buy genuine silk stockings..I used an old pair of these silk stockings to cover the wings of my Piper Super Cruiser (72" wingspan) and those wings are still in good shape and still tight as a drum over 50 years later. I posted a recent picture of part of these wings recently showing the lack of cracking. Of course the dope will crack if the fabric is giving up. Genuine silk will last for decades.

Fabric to be doped should not be adhered to the frame work with dope. Additional coats of dope penetrate the previous layers to form a single overall layer. This soften the previous layers and the gluing will (does) slip.
A glue that, after cured, is not attacked by dope has to be used.

Doped fabric can be repaired that no signs of repair is achievable. The new dope used with the repair patch fuses into the original dope and can be wet sanded with 400 or 600 grit and make the patch completely disappear. I do not know any other finish that can do that; it is particularly advantageous for nice models made for show or contest purposes.

Voila ___another 1/2 cent of experience with the only finish I ever used.

Zor

shd3920,

I fail to understand your posting.

Silkspan is not a fabric. It is a specially made paper that is not woven using threads.

When you ask
What paint would you recommend?
Dope is a paint and does not need additonal paint like enamel or latex.
If you are asking for "What brand name of paint would you recommend ? then read the line above.

Butyrate dope is highly resistant to glow fuel. Your model should be washed (cleaned) afterevery flying days.
You can fly dozens (hundreds) of hours without any visible effect of the exhaust on the dope id you clean your model after the day of flying.

Now why would you ask "and stop the constant shrinking caused by the dope?"
That constant shrinking is what keeps a doped finish nice and tight and never wrinkle. You should not want to make that quality disappear. It is one of the good reasons to use dope.

quote . . .
Or could I use something instead of butyrate dope to apply the silkspan?[/size]
unquote . . .

If you are using "silkspan" you must be making quite small size models and very light weight ( just a few ounces).

Are you using engines running on glow fuel ?
What models are you building or assembling ?
Guillows ?

We could be of more help with more information on your project(s).

Zor

http://www.youtube.com/watch?v=9jLCgYOJrLI

There are many little things that are known by only a few concerning application and finishing of a silk and dope finish. My dad taught me the gift of applying silk and dope over 45 years ago and when you know the secrets it is actually quite easy to apply and you get a superior finish.

Clear gelatin can be applied to fill the weave of the silk before brushing on the many,many, coats of clear dope required to get a good gloss finish.

Just a couple drops of castor oil to a quart of clear dope as a plasticizer.

Ounce for ounce nothing is stronger than silk except carbon mat.

Yes! I am a "Doper" and proud to say so!

I still have fresh gallons of it stored for future use. I love to pop the lid off and stuff my face down in the can and take a big whiff. I can actually feel my liver shrink up like a piece of sun baked green bologna!

I finished this 77" Vito Tomeo Seafury with silk and dope. Then primered and filled and then painted with
automotive laquer and then a final K/B satin epoxy clear coat.

There is a great product by SIG called "Koverall" that is applied just like silk but can be shrunk down with a heat gun. Koverall is a great covering material made of dacron polyester that is just like what is used on full scale aircraft but of a lighter weight per square yard. It is heavier than silk but a very good covering material. I used Koverall on this 28% Scale Gee Bee Z and the results were a bit heavy due to using urethane 2-part primer and Sherwin-Williams "Polane" urethane paint.

I still consider silk as the best covering material available. It requires the most work but your efforts will be well worth the final results.

You will never have to iron the bubbles out of a silk and dope covering job. Never!!!!

Here is another one that will throw you for a loop. 3/4 ounce fiberglass cloth applied just like silk and dope. It works out perfect for a strong but lightweight finish just like silk. You can take a lot of weight off of a scale warbird by applying F/G cloth with dope first and then apply the resin finish. The wood will be sealed with the dope and keep it from soaking up that heavy resin.

acoat of buterate clear dope around the edges of the wing etc. let it dry then drape the damp silk and carefully "stretch" it lover and paint over the edges again. no heat. this is a natural thing,,,not plastic,,,hehe. buterate dope will seal it and it will bw tight. for life give it a few coates of silver until light wont shine through it. the sun will "rot" it in short order.

Silkspan is available in various weights and can be used on quite large models. I fear that like silk and dope, silkspan and dope finishes have become something of a lost art.

When properly done nothing is more beautiful than a silk/silkspan and dope finish. The process is quite time consuming though.j

jess

Interesting subject, thanks to all for sharing their experiences.
Denny

Silkspan on a trainer?!! Hmmmm.....Longevity might be a problem unless you are an accomplished pilot.

Let me suggest that you take a look at the Model Research Lab website and find their polyester tissue. The material looks and feels similar to silkspan but is much much stronger than silkspan. It will rip like silkspan but boy you have to work at it. Weight is similar to medium silkspan but takes less dope to fill so you end up with a lighter product

It is applied with nitrate as if you were covering with silkspan (no water tho, sorry) and is heat shrinkable like woven polyester coverings and films. In my experience it offers the best of all the worlds. It fills quickly to boot (again with nitrate) and is ready for just about any paint (thinking spray can types like Krylon here). It is a good idea to use primer first over the filled tissue and sand lightly. Then shoot your colors

Back in 1980 I built a VK Fokker Tri-Plane. Covered with real silk and butyrate dope. 2 coats of clear, 2 coats of silver and 14 coats of Fokker red. Absolutely beautiful finish. Still have the plane altho the fabric is torn and cracking from sitting for the last 25 years. You have to like building and finishing to do something like this!

Hi mike31,

The first coats of dopeshould benitrate for adhesion and reduced tightening.

Let me think that the silk was not genuine.
I have here models that are over 50 years old with finishes just as nice and tight as when applied.

Zor

Has anyone posting in this thread tried the "meniscus method" of dope application to silk? It works quite well with a bit of practice.

jess

Have you used that method on curved surfaces and on coumpond curved surfaces ?

Zor

First off, I say go for it! the silk and dope that is.
It is an art form, as mentioned earlier, but then so is building isn't it?
One VERY important note that wasn't mentioned is, Humidity. This will kill your finish. You want the air to be as dry as possible, so summer time finishes will look best. If not, the moisture will blemish the finish with cloudy spots, so do this to the entire piece.
Also Don't worry about color. You're using fabric and it can be tinted. "Rit Dye" is what I've always used. Cheap and easy to use. I have always used the powder form that can also tint plastic (like your canopy). I under stand the liquid dye cant do the plastics, but I never tried.
Dharma Trading is The best place for ordering silk. They are very nice and cheap. As for the the Dope, look into Aircraft Spruce and Specailty. I was told that they are the main manufacturers of the stuff, so it will be as fresh as you'll get. I know Brodak gets their dope from them.

Good Luck!!

DM

"If not, the moisture will blemish the finish with cloudy spots, so do this to the entire piece. "

By the surface of the dope "flashing over" before the rest has. Easily taken care of by spraying a light coat of thinner over the area, thereby thinning the surface, and allowing the trapped moisture to escape.

Les

I have applied dope in sub-freezing temps before with no blushing problems as long as the air is dry and your dope drys fast.

For example:
If you have a day that is 80 degrees and the humidity is above 80% you will/might have blushing.
If you have a day that is 30 degrees and the humidity is 30% you will not have blushing.

50% humidity or less is ideal for any paint application.

Cold dry days are no problem for applying dope. Dope will not freeze.

Dope must be stored in a cool place due to the fact that it will "gas" if it gets too warm and can actually blow the lid right off the can. A hot garage in the summer is not a good place to store dope.

Remember that thinner comes in 3 different "speeds". Slow / Medium / Fast. It was mentioned that applying a ligt coat of straight thinner will remove blushing,which is true, but you can also simply wait till the dope has dried and polish it out. The trapped moisture will usually rise to the surface where it can be removed.

I usually am not too concerned with blushing until I start applying my color coats and this is, in most situations, not until I have applied at least 10-15 coats of clear dope.

On the contrary, if I am going for a clear finish over colored silk, blushing must be addessed quite seriously since the finish is clear and only the dyed silk is the underlying color and herin is the true beauty of a silk covering job. The weave must be kept perfectly straight when pulling the silk tight on the framework and this is where the "Master's" true craftsmanship and artistic abilities come to play.

Applying silk is easy if you are going to paint over it with colored dope.

Applying a clear dope finish over dyed silk requires absolute perfection.


SPEEDY

Yes, worked like a charm. Curved surfaces make no diference as ite silk is alredy in place, adhered and shrunk when the dope is applied. I have tried the method using both toilet paper and foam brushes.

Note that I have used it only with clear dope to produce translucent finishes.

jess

jess

[quote]ORIGINAL: Aurora_60


One VERY important note that wasn't mentioned is, Humidity. This will kill your finish. You want the air to be as dry as possible, so summer time finishes will look best. If not, the moisture will blemish the finish with cloudy spots, so do this to the entire piece.


Sorry, I was up late, I meant to say:

You want the air to be as dry as possible, so summer time finishes will look best. If not, the moisture will blemish the finish with cloudy spots, or it will do this to the entire piece.


Here the summer works best. I guess the summer would be bad in a lot of areas for humidity. Would be nice to work in cold dry weather. A heater would make the air in the room even drier, wouldn't it?

I'm relocating from Hawaii to Utah in a few months. Have a few planes built that I'm looking forward to covering.



DM