Polyspan how much will it shrink?

[bruce fraser]

I am doing my first Polyspan covering. I got it on no problem. I shrunk it down with an iron but it still seems to be less taught than I expected. There are no wrinkles or anything like that but I would say it's certainly not as taught as the monocoat on my Flight Streak ARF. How taught should I expect this stuff to get? Will it get a little tighter with application of dope? I have my iron as hot as it will get, the stuff will not melt, that's nice. Is it just because it's fabric so it has a different feel?

[Clint Ormosen]

Polyspan is good stuff. If you have it shrunk down to fairly taught without any wrinkles, it's probably good. A few coats of shrinking dope, either nitrate of butyrate, will start to make it even tighter. Once and a while I'll hit it with some heat again LIGHTLY after some dope just to make sure there isn't any loose areas, but there usually isn't. The fabric will melt using a heat gun too long in one spot.
 By the time you have your entire finish on, the stuff will be plenty tight. Don't worry.

[Bill Gruby]

 I don't use the iron for polyspan. The heat gun is much better. Polyspan WILL burn thru real quick.  If you set the temp on the iron too high you wwill find out in a real hurry what I am talking about. Ther gun does a better job of shrinking polyspan.

 "Billy G"

[Andrew Borgogna]

I use polyspan and nothing else.  Like Bill I use a heat gun not a an iron.  BUT be carefull and never let the gun get too close or stay in one spot too long.  It will burn through, having said that I use non-tautining dope and a few coat will also tighten up the material.  I always start with nitrate dope and put on three coats.  For my electric planes its from there to paint.  If the plane will get a gas engine I put on a couple of coats of Butyerate dope for fuel protection then paint.  The polyspan does not have to be drum tight before doping just wrinkle free, the dope will go a long way in giving the material a drum like tightness.  I have never used and will never use tautining dope, there is no need to and I have seem planes that did and the polyspan has split.  There is such a thing as too tight.  Finally as has been mentioned, you can always pass the heat gun over the wing after doping but again be carefull do not focus on one spot.  Keep the gun moving and keep at least four inch's of distants from the material.
Andy

[bruce fraser]

Thanks guys! I have 2 coats of dope on and it looks good. I'm using Randolph non-tautining.

[Clint Ormosen]

Thanks guys! I have 2 coats of dope on and it looks good. I'm using Randolph non-tautining.

That's the same stuff I use. It'll be all good when you're done.

[Dallas Hanna]

I don't use the iron for polyspan. The heat gun is much better. Polyspan WILL burn thru real quick.  If you set the temp on the iron too high you wwill find out in a real hurry what I am talking about. Ther gun does a better job of shrinking polyspan.

 "Billy G"

Hi Bill.   No real problem with an iron on Polyspan.  I use "mother dear's" discarded household iron for this purpose.  With it set on the lower end of "cotton" there is no sign of burning and the broader surface shrinks the polyspan quickly and evenly.   The heat shrinking is done prior to dope sealing so the surface is wrinkle free.   Usually about 4 coats of 50/50 does the job of that.

HH

[john e. holliday]

The Poly-span will not get as tight as Mono-kote initially.   I now go with butyrate dope clear from bare wood up to the color coats.  Just make sure the poly-span is smooth when you start doping.   Also if you have a warp in the wing whem you start covering, don't expect the poly-span to pull the warp out when doping.  It only shrinks so much much before holes start appearing.  It is also easy to patch.