sensei

Frank is right, that is exactly how I remember using silk and silkspan, and it always worked great.

Bob

ululi1970

I know this thread is about fabric and dope, but... I had a bad experience with Minwax Polycrylic and fiberglass. Everything went well, until one day, while I was attaching decals to the nearly finished (painted) model I let my desk lamp get close to the surface. The surface near the lamp started almost immediately to
bubble and blister. Further experiments with a mockup panel covered with glass and minwax poly in the oven showed that ~135F is all it takes to cause blisters. For the record, I used lacquer sanding sealer on the bare wood, waited 2 weeks before applying the fiberglass with the Polycrylic...
Further research online confirmed my findings. Even in a relatively cool climate, under the middday sun a dark surface will exceed that temperature...

Somebody reported good results using the Lacquer sandable sealer instead of Poly to attach the fiberglass cloth. For the final layer, lacquer+talc (50/50) gives a very smooth finish. I have not tried this method. However, one thing to keep in mind is that in both cases one cannot hope to
achieve the strength of fiberglass+epoxy, which I think is a big advantage of the traditional glassing....

Alberto

OldScaleGuy

My Feedback: (2)

Interesting. I did not do any testing with heat involved. Thank you for setting us straight.

Zor

Hello,

Ask yourselves the question ___

Why is it that full size airplanes refinishers do not use some of the products mentioned in these recent postings.

Aircraft Spruce in Toronto had next door a location where folks were building their own full size airplanes and only genuine aircraft dope (Randolph) was used if the airplane was fabric covered. They have now moved to a new location where they are located on an airport.

Years ago I was often helping a friend who owned a refinishing business. None of the products mentioned were used.

Zor

sensei

I believe the sealer is your problem, and you only need the glass to kill the swell back of the balsa under the paint, so strength is not a consideration for paint surface prep.

Bob

countilaw

Back in the 70s and 80s, we used K & B Super Poxy Clear to seal the balsa sheeting on pattern wings. K & B Super Poxy had the same properties of Imiron automotive paint which is no longer available to the public. Now I use Automotive clear with a catalyst to seal the balsa.

Then the fibre glass (3/4 oz ) goes on with another coat of automotive clear to adhere the glass. Automotive clear is fuel proof and will stand up to the noon time sun heat.

I shy away from anything water based for a sealer. Water based automotive paint will work for your base colors, but must be sealed with the clear coat.

As for covering open areas, I think it is best to stick with the tried and true. Silk and dope. If you are going use automotive paint for the colors, I would use Nitrate Dope.

Frank

Zor

Hello Frank,

The silk you are mentioning is likely a light polyester treated to have the touch and appearance of silk.
A regular polyester material will do as well at much lower cost.

Zor

countilaw

No Zor, I use 100 % grade A silk with a weight of 5 mm in a Habotai weave. I get it from Dharma Trading Co. Their prices are good and their shipping is fast. Before I used Sig Silk, but their prices just got out of sight and you can only get one square yard in a package. With Dharma Trading, I can get a width of 54 inches by 55 yard bolts.

Here's a hint: If you lay your silk with the grain of the silk running across the ribs, the silk will shrink straight across the ribs. If you lay the silk grain running from front to back of the wing, the silk will dip between each rib.


Back when me and my friends built Free Flight planes and glider, we found that if the silk dipped between the ribs, it enhanced stability in the flight. (Or seemed to anyway) But what did we know, we were just kids and knew very little about aerodynamics.

Frank

P.S. We used only clear butyrate dope throughout, to save weight.

Zor

countilaw,

I wonder why you start by writing NO.

I have no proof that the silk you are buying is genuine silk and I suspect you do not know yourself.
People these days buy silk being labelled as such and accepting that the product they buy is silk.

Most of the time it is a polyester man made material treated to have the appearance and the feel of genune silk. The word "silk" is accepted (promoted) in the industry and become accepted by the buyers.

Genuine silk is very expensive and sells for about $100.00 USD or more per square yard.

Quite a while ago, a few years, I knew of a test that could be made by taking a thead and lighing it (exposing it to a flame) and he results would reveal if it is genuine silk or imitation.

Ido not think i have some genuine silk and some artificial here now to try this test again.
Just from memory I seem to remember that genuine silk would not ignite and keep burning while the imitation would.
- - - - - -
I just interrupted this writing and cut a little piece of polyester about 3" long and put a lighter at one end.
It caught and the flame ran all the way to my fingers in about one second.
I wish I had some gnuine silk but if my memory serves me well the real silk would just shrink in the flame and would not propagate as the flame is removed.

Anyone out there remembers that test ?
If you do please make a posting.

Zor

countilaw

Zor, the silk that I use is advertised as 100 % pure silk from silk worms. And No, silk does not burn. It just disentigrates . Silk is now cultivated in China. Did you know that a strand of silk from one cacoon can be a mile in lenght. It's called China Silk because it is cultivated in China. Originally Silk came from Japan, hence the term Nylon. Nylon was manufactuered as a replacement for Silk for parachutes During WW 2. Remember the slang, "It's time to hit the silk"? Nylon is an acronym for " Now You Look Out Nippon".

Frank

goirish

Zor, the dacron that I have is .009 is that to thick?

Zor

Frank,

You are pretty well confirming my old memoryof the burning test; thanks for that.

I sure enjoyed reading the rest of your post which is very interesting.

I wish I knew where the advertisement actually say from silk worms.

I am going to the site of Dharma Trading Co (if I can find it) and see about "from silk worms".

Regards from Zor

Zor

To all interested,

I have found the Dharma site and contacted some of their staff.
We exchanged some email.

I am waiting now for a reply to my request to them "if I can post that email in the forum".

More later,

Zor

Zor

Greetings,

I have received permission from Dharma to post the email.
I have to format the post properly and I am not a computer expert.

Anyone interested, please check this thread in the next 48 hours.
I find their email has some interesting information.

Zor

Zor

Hi David,

Dharma is the topic of discussion on one of the big online discussion groups, as are other silk retailers.
The discussion is that there is no way to know if the silk one buys is really silkworm silk.
These days not only do we have polyester "silkie" fabric, but the manufacturers of fibers from corn and soy are also calling their fibers silk, probably because they are using a protein for the process.

Zor wants to know where, on our website, he can refer people to read that we really do use the real silk from silkworms.
I was sure it was there somewhere, but I cannot find such a reference.
Since he is ready to stand up for Dharma in the international discussion group forum, I hope you can find it in your heart to send him some official word that it is silkworm silk, not just 100% pure soy silk that we are selling.
And it may be time to add that word silkworm to the Silk heading for the fabric pages. Or some wonderful article about silk cocoons being our source like we have an article of the bamboo and hemp growing farms.

Thanks, and if you don't want to send a note to Zor, I can do that when I return on Friday for my next shift, but he's going to think we aren't paying attention to this important debate. He won't take my word for it anyway, I already assured him by phone.

Laura Fritz

Fritz
[email protected]
Customer Support
Dharma Trading Co

Hello Zor,
Regarding our silks and their content; we import all our silks direct
from China, and have been purchasing our silks from the same vendors
for over 15 years. We have always asked for, and received 100% silk
from silkworm cocoons.
While we do not have visual confirmation, that is to say we have not
visited the factories and seen them boiling the cocoons, spinning the
yarns and weaving the cocoon silk into fabric, i would be highly
surprised to find there was anything other than silkworm thread in our
silks. I sincerely believe that the number of vendors out there trying
to cut corners by passing off soy silk, or other fiber, as silkworm
silk is extremely small, if they even exist. This sounds more like
rumor or conspiracy theory than anything real.
As for where someone can go on our site to see what we say, there
isn't a specific mention that our silk is 100% silkworm silk. We never
thought about that as being necessary to say. What we have can be
found on the Dharma web site page at the URL below. If you scroll to
the bottom of the header, there is a link to more about our silk.

http://www.dharmatrading.com/html/en...bric_silk.html

I hope this answers your question. Please feel free get in touch if
there is something more we can tell you.
Thank you very much,
David

> Hello David,
>
> Can I have your permission to post your email to me in the forum ?
>
> Many thanks.
>
> Zor
>
Hello Zor,
That would be fine. Please feel free to use it.
Thank you very much,
David

Zor

I hope you guys made your own conclusion from the email from Dharma.

Zor

EJWash1

My Feedback: (3)

countilaw,

You got my curiosity going so I ordered a sample packet of silk from Dharma ($6.95 - free shipping). The samples included 5mm, 8mm, 10mm, 12mm, and 16mm Habotai 4" X 4" swaths.I cut a few 3/4" strips of the 10mm sample, and burned it using a low flame. The edge of the lit silk (for lack of a better description) curdled into ash and would extinguish quickly. Does this concur with your burn tests of silk?I've never covered an R/C model with silk and dope. My experience with dope is from the '60s and '70s when I was a kid and built Guillows and Comet rubber-powered balsa stick kits using tissue anddope.I have a few vintage R/C kits that scream to be covered in silk and dope for time-period correctness, so I appreciate the benefit of experienced modelers.

You post that you're using 5mm silk. Is this because this weight is the lightest Dharma offers? Is there a rule-of-thumb or a formula used in determining what weight silk to use on a model predicated on the size/power of the model, or does this matter?

goirish

I finally got my nitrate and butyrate in yesterday. Will start on the covering of my G-Shark tomorrow. Also My first attempt at silk. Wish me luck.[X(]

EJWash1

My Feedback: (3)

Dacron or silk?

goirish

silk from Dharma. 5mm, using Randolph nitrate and butyrate. Suggested by ZOR.

EJWash1

My Feedback: (3)

I must have missed something. Last I read you had gotten dacron and was going to cover with that. Anyway, good luck with your covering. I'm interested in hearing (and seeing) how it comes out.

goirish

I do have the dacron but decided to try the silk first. Started covering the rudder and elevators. Call me chicken, but I wanted to try those first and if I screwed it up I could replace them. I did find out one thing it is easier to cut (trim) after the nitrate has started to set up. my first attempt was to trim while the silk was still wet. Easier the other way. One nice thing it goes around curves nice. I put the silk on dry, not sure if I should have wet it first. Seems to be some different opinions as to have it wet or dry.

LesUyeda

"Randolph nitrate and butyrate. "

Shrinking nitrate, I hope. There are both shrinking and non shrinking available.

Les

goirish

non-tautening nitrate but tautening butyrate. Please don't tell me it should have been tautening for both. LIE to me[:'(][:'(][:'(]

flyingagin

I think it should have been tautening nitrate as your first coat to apply and shrink the silk and then non tautening butyrate for you color coats . Tautening butyrate would have been ok also, but it is my understanding that tautening butyrate keeps on shrinking for a very long time, maybe never really stops.

Nityrate dope is not fuel proof where as thebutyrate and comes in colors so it is the last coat

Ken