Finishing Gurus,
I am working on an airplane that I am trying Polyspan® on and decided to stop it at the tips.  Initially I tried silkspan for the tips but did not get a result that I thought I would be happy with, so tried some silk that I had left over from a different project.  In any case, I was able to get the silk to go onto the tips without any problems or wrinkles, but after a couple of coats of Brodak clear, which I think is low shrink, I started to develop some large wrinkles.  I think that I have about 6 coats on it now and the weave is filled, but the wrinkles are still there.  Any advice?  I have some Sig Supercoat that I thought would make quick work of the wrinkles (planned on using Brodak thinner to keep at least one thing constant) but thought I would ask here for some input.
Thanks,
John

You might want to try a solarfilm iron on your silked tips before you rip it off and recover them! Start at a low temp. and work up the heat. I've removed wrinkles from doped tissued wing tips using this method.

Cheers        Neville

John,
Before you rip it all off, hit it with a heatgun using continuous motion.Use the fan nozzle on the heatgun for better control of the heat pattern.Won't hurt anything and doesn't cost anything to try. I've had variable luck doing it.

Once upon a time I had this problem,so I softened the dry dope up with another very thinned(more thinner) coat, then used low heat to dry/ shrink the tip.Just be careful to not heat the thinned coat to high on heat trying this method!

my .01 werth...

John, did you switch to silk or silkspan to do the tips and why did you give up on the Polyspan?  This is a picture of the cowl for my new PA model covered with one piece of Polyspan.  It really isn't that hard.  (read that easy)  The trick is to use nitrate to seal the balsa, about four coats and sand smooth.  The process from there is pretty much the same as Monocote only easier.  Tack around the edges and use an iron, NOT A GUN!  The nitrate acts just like glue allowing you to glue the polyspan in the compound curves.  This is the first time I have tried this but I've done many wing tips.  Challenge yourself, it only takes a little practice.

Gene,
I am embarassed to say that I did not look at the grain.  I had one direction that was as wide as the tip so I cut it accordingly.  Perhaps one of these days I will remember to look before I cut.

Mike,
I was talking with another flyer in the area today and he asked why I did not finish with the polyspan.  I guess on my next project I will have to give it a shot.  Currently I have a bunch of Sig Nitrate.  Do you think I could get away with using it and Brodak thinner if my top layers are going to be Brodak?

Randy,
I have the Sig Supercoat on there now and it is pulling it tighter.  Since I know that it takes a little longer than the Brodak dopes to gas off, I might need to wait a few more days before I make the final call. 

Richard,
I tried the heat gun and it does seem to tighten up the silk as you pass over it.  However, when the whole things cools off, the silk actually seems a little bit looser.  Generally letting it dry and stabilize over night brings it back to a semi-taught condition.  As I mentioned to Gene, I did not take a good look at the grain of the silk before applying and may have not put it on properly.

Everyone,
I will keep you all up to date on how this project works out.  The woods are calling and I will need to go sit and be very quiet for a few days, but then I will have a bit of time off to keep working on this.  Thanks for all of your advice so far.
John

I had the same experience and put some Sig over the Brodak.  It got better, but not perfect.  But by the time you read this, you'll be back from the woods and can see whether the Sig did the trick.  I tried the heat also to no avail.

Pete Peterson is the Master of Polyspan.  Before I cover my next plane, I shall sit at his feet and gain his wisdom.  On second thought, I don't need to sit as his feet.  I only come up to about his knees when I'm standing. 

Howard,
It got better, but not perfect.  This is an OTS airplane so I am not too concerned about a perfect finish, but I should do better on the next one.
John

John,
As I recall, my Sig Nitrate can says NOT to use it on silk over open bays--but to use Sig SuperCote Clear as it shrinks more.

Read the label

John,
As I recall, my Sig Nitrate can says NOT to use it on silk over open bays--but to use Sig SuperCote Clear as it shrinks more.

Read the label

Alan,
I used Brodak Clear over the silk as it looked fairly tight after I applied it.  I do know that it is low shrink, probably similar to Sig's Lite Coat but I thought I was going to be okay with the base silk being fairly tight.  I think that I will use the Sig as the base filler coats for the material coverings in the future.  The tips are looking okay, but I will certainly pay attention to the silk grain and use the Sig Supercoat on the next one.  Currently I have some Nitrate, but have not used it much as either a base or to attach material to the airplane.  There is this Super Chipmunk on the list of things to do though.........Perhaps I can try it out on that one.
John