Silk Question.

Leading on from the RSM silk thread, (no pun intended), I am ashamed to admit I am still building a model I started 39 years ago, a Frog "Attacker". This is nice looking "T'brd" type, although I have heard varying tales as to its flying qualities.
Question - I covered this model in light silk, and very nice it was too. Unfortunately it's been done so long that it has perished, cracked and split with age before the model's even been finished. In case it takes me another 39 years to finish it, can anything be done to prevent this cracking? Any special dope? plasticiser? whatever?

>Leading on from the RSM silk thread, (no pun intended), I am
>ashamed to admit I am still building a model I started 39
>years ago, a Frog "Attacker". This is nice looking "T'brd"
>type, although I have heard varying tales as to its flying
>qualities.
>Question - I covered this model in light silk, and very nice
>it was too. Unfortunately it's been done so long that it has
>perished, cracked and split with age before the model's even
>been finished. In case it takes me another 39 years to
>finish it, can anything be done to prevent this cracking?
>Any special dope? plasticiser? whatever?

As the commercial goes about a certain brand of ice cream: "It's the cows", in your case "It's the dope." Yup, the old dope dried, got brittle, and most anything underneath it got brittle, too. Silkspan, silk, it made no difference. I crashed a couple of planes back then that literally shattered when they thudded in.

The new dopes that are plasticized will not do this. And that is the key. Make sure you use a good plasticized dope when you recover, or add a plasticizer to the dope.

Now I am proud to say we have tested this out with the new dopes made over the last 10 years and even with straight in crashes they do not shatter even when using silkspan.

Some things do improve over the ages, and the dope formulations are one of them.

Thanks for a spot-on answer Len. Will bear this in mind.

I use a plasticiser in all my dopes and lacquers except the two to three coats of Super Coat that I use to shrink the silkspan or silk.
I got it from the auto paint supply house that is intended to be used in acrylic lacquers. So far I have not experienced any problems using it in Sig dope, or auto acrylic lacquer (about 10 years now). No Brodak, yet, so I can't say about that.
It has greatly increased the life span of the silkspan.
Bill <><

I have used "ESAKI" silk for many years. I still have a C./L stunter I built in 1962 with ESAKI silk still in great condition. On the other hand, my Palmer VENUS with ESAKI silk built only about 10 years ago has split and deteoriated. I stripped it and refinished it in silkspan and Brodak dope with good results.

The perplexing problem is: my 1962 plane was with SIG butyrate, and also was my later VENUS. They aged quite differently. I don't understand the difference. The silk was the same: the dope was the same. But one survived and the other did not survive.

"tis a problem"
--King of Siam,--- in the movie.

Hey, isn't the correct quote: "Tis a puzzlement"

Quite correct. I only watch Disney movies..

Dr. Spark

As I understand it. Despite Sigs statments to the contrary, they have changed the formulation of thier dope more than once.

The dope that you used way-back-when is different than what you are getting now. If you are still using Sig dope, be sure to add a few drops of plasticizer to your mix. That should help improve it's flexability longrun.

IMHO, Brodak solved 99% of the problems we were having with our finishes, when he came out with his line of specialy formulated dopes from Randolph.

If you really want to know the story, call Windy. He did the development work, in conjunction with the manufacturer. No one knows more about working with dope than he does.

The absolutely best way to paint silk is to spray the clear on. You loose some dope but there are no runs! Back in my younger years I used Rit dye dissolved into thinner to tint the clear dope. It gave a nice deep color and seemed to plasticize the dope as well. That was a plus for free flight but not for CL?

Thanks everybody for your help.

Question ?? What are you fellows usin' for plasticiser and where are you gettin' it ???
Thanks, Gil

Dave Browns "Flexall".