Polyspan

About two weeks ago Scott Riese asked about the current source of Polyspan and Preston correctly directed us all to the FAI Model Supply web site. The web site has two somewhat helpful articles about using Polyspan.
What I have heard and read about Polyspan is a mixed bag of pro's and con's. I would appreciate hearing from anyone who uses or has used Polyspan what your experience has been. Any special tricks that you you might have developed to make it behave the way you would like would also be appreciated.
Thanks!

My guess is that, the better the builder, the happier with polyspan folks will be.

I find it annoying. The stuff is plastic fiber. When applied and then sanded, any "sand through" yields a bunch of micro plastic fibers poking up and leaving a napp for the lifetime of the model!

I would also question any weight advantage, although will not question a strength issue...after all, it's plastic!

Good builders get their projects into very fine shape prior to application, and, therefore, don't have the problems.

See Ya

Peter, good timing. I have used Polyspan on several projects, I'd be glad to show you. I found it much easier to work with than silkspan, for example, and easier to apply than silk. We use the stuff on indoor rubber models, so I think weight is not a factor. It sure takes less dope to fill in than silkspan/silk.

Peter,

I have used Polyspan on a DeBolt Stuntwagon, and have mixed feeling about it. I really like it toughness. You won't accidently poke holes through it like you would with silkspan.

But the thing that drove me nuts, was trying to get the edges to stick down, especially around wing tips. I used 50/50 butyrate dope, and did rub some spots down with my fingertip with some success.

What are your techniques for making Polyspan lay down around wing tips in particular?

TIA

I adhered my Polyspan with nitrate dope, as if it was silkspan. Any edges that did not cooperate (and I left plenty of selvage around the ends) was the beneficiary of my heat gun, cotton glove, and more nitrate dope. I used my covering iron to tack down any straight lines, such as leading edges, trailing edges, if they seemed to want some help, and most did. Going around wingtips, the heat gun. Worked every time. Heat and pull and more dope. Treated the stuff more like a plastic film than a fabric going around corners. Worked very well, and then after trimming off the selvage, used the iron to seal down the seams. It's a mixed media of adhesive techniques, but the results are there. Silkspan, too,responds to those ministrations, but care is needed, the stuff can't take the yanking that Polyspan can. The person doing the work cannot be shy, he needs to have his pot of nitrate, heat gun, and iron ready to hand. But it does work out very well.

What I found to be a "BITCH" with the stuff was that I used Brodak Clear on the wood about 50-50 let it dry, put the polyspan down and apply dope around the edges. HOWEVER, the dope DRYED before I could pull all of the wrinkles out. I tried retarder, more thinner. I found that Brodak clear is HOT. SO that's the only thing I found bad about useing polyspan. Other then that IT'S GOOD STUFF. Scott

I use polyspan to provide puncture resistence and strength to the wing. The method I use is to cover only the open bays. Apply three thinned coats of dope to the entire wing. Cut a piece of polyspan about 5/8 inch larger than the open bay all around. Stick this down with dope and completely bond with couple of coats. If you get a wrinkle here and there, don't worry about it! After dope is dry, heat shrink the polyspan. You can apply heat over the forementioned wrinkles and most will come out with the help of some thinner and dope. Fill the polyspan with three brushed coats of 50-50 mixed clear. After final coat has dried overnite, any wrinkles that still persist can be sanded of with a block and 400 sandpaper. Now cover the entire wing with 000 silkspan, attaching the silkspan around the edges of the wing as you would normally do. Dope in the normal way. You will now have the same surface as the rest of a tissued model with the toughness of polyspan and not have to deal with the "fuzzys". One last thought, if you install polyspan upside down, and I have done so, you will get a really rough surface! The tissue will still work and save the covering. The extra weight is minimal and worth it in my opinion. Roy DeCamara

SURE........ NOW YOU Give up your secrets. Thanks a lot Love Scott...lol...see ya at the field

I've applied polyspan on ff models using thinned out contact cement on the edges and ribs and a sealing iron. The edges of the material stick quite nicely. You can blend compound curves with the iron or heat gun, occasionally ungluing the stuff to move it.
I follow that up with nitrate dope and I've never had a problem. Curt Stevens at MRL sells larger quantities of polyspan for less $.