Dunno Doc, it's great stuff, I won't use anything but.

 Once it's on, shrunk, doped and prepped, you can finish it with anything that's compatible with your prepped surface. For more info I'd recommend just doing a "Polyspan" search here on the forum, there has been many forum discussions on Polyspan.

 I wouldn't go there Jim, I'm pretty sure you'd end up with nothing but a BIG mess. If you don't want to use dope, don't use Polyspan.

You can also apply Polyspan as if it was Monokote.  Apply Balsarite or Stix-it to the adhesion areas (actually, Nitrate Dope, White glue and contact cement work too), and apply with a hot iron.  You can really do tips perfectly this way.  Pull and heat, pull and heat.  Think of it as a stretch-on, not a heat shrink!

BTW, in my experience, use an Iron to final shrink the material, it is awfully easy to melt holes with a hot air gun!

If you sand into the material and get the dreaded "fuzzies", wet sanding with 2000 grit paper will cut them down so you can seal them back off with dope.

Note especially Polyspan has a "good" side that MUST be the outside, and it has grain that MUST go spanwise.  Violate either of these and you will hate the stuff. 

I was referring to the people that say it is not durable/strong enough for I-Beamers.   

I helped Dennis Coleman cover the wing to an All American with polyspan last night.  He used adhesive on the structure and ironed the material down.  He used "Ceconite" as his adhesive, and frankly, I don't think it begins to compare to Balsarite for adhesion.  On the other hand, it's adhesion is light enough that you can pull the covering up to make corrections (so maybe it has merit after all).

Using pull and stretch on the tips, the wing came out flawless.  We only used a hot iron for the whole application, testing the heat on scraps to get it right.  Basic main panel is done at a heat that will assure adhesion, but not give ANY shrink.  When you do the tips, you just want the material to soften a bit so you can stretch it.  Too much heat here would possibly weaken the material while pulling it and cause tears (both rips and salty drops of water from the eyes).  Finally, heat the iron until a scrap shows definite shrinkage, and de wrinkle the wing.

I don't think you can get the tips of a typical wing perfect without using heat on this material.

There are a few tricks to getting it right.  After tacking down the main panel to about 1" from the start of the wingtip, pull up the wingtip tack and start the pull and stretch routine at the center and alternately work out to the L.E. and T.E.  For this, start your heat in the main panel end bay and roll around to the tip.  This sucks some of the material out of the main panel to form to the curve of the tip.

One change from my usual technique that worked well, is that instead of doing the root first, we tacked the center of the tip, then did the L.E. and T.E. tacks on the wing root.  I am still thinking about why this worked better, but it did!  We discovered this by accident when the center wrinkled up on tacking the tip.  So we pulled the root tacks up and re did them.  Bingo, a much easier time eliminating all wrinkles!  We did this on the remaining panels, and it went very well.

I heartily recommend Faye Stilley's books on film covering.  They are available from Model Airplane News.  The man is THE MAN when it comes to film coverings.  I saw him do a demo at a model show, and I was blown away!   

I have a roll of polyspan that I haven't used.  I think the negative comments about the product going around any compound curves has kept me from using it. I always get good results from SGM silkspan, so I'll be cautious for now.

Floyd

Hi Floyd,

I think, like Larry just posted, that curves can be dealt with just fine.  I have not had a problem covering the tips of those which I have done, so far.  With it being heat shrink, it really helps, and although I always use dope to attach it, the heat activated "glues" work well from all accounts.  I did suffer a very short learning curve on how "hot" the heat gun can be set, and how quickly to move the gun around, but I learned quick once I blew a small hole in the bottom panel of the first wing I did!

Many have used silkspan to cover the tips of wings, I just haven't had to do so, yet.  It DOES appear to have much more torsional strength than the normal plastic heat shrink coverings so I am not afraid to use it on an I-Beam wing.  PLUS!  Polyspan's resistance to punctures really, really, makes it a good choice of covering instead of silkspan.

We actually covered a profile fuselage with it, once, but I don't think I would do that again.  I didn't see any benefit, and silk, silkspan, CF veil, or even 1/2 oz fiberglass cloth are all materials I prefer to use on a fuselage.

Bill

Having read this thread thoroughly, I have a burning question to you all.

I used polyspan on two open bay wings. I started with a adhesive like the old coverite, then applied heat with a shrinking iron. Four layers of nitrate shrinking dope. Then I decided on a fuel proof coating of transparent 2K polyurethane varnish. Next half day later, the tension in the polyspan seemed to have disapeared on both wings. The varnish was not fully cured yet.  I then applied heat again and retained some of the tension. Has anyone out there had the same sort of experience? I read that it is recommended to wait quite long before putting on a finishing coat. How long is long?

Thanks.