Bound to happen sooner or later on this build.  Last bay of the top wing I so badly wanted to get some color on.  First time with Polycrylic.  I was amazed at it's toughness.  Too amazed.  I relaxed.  I drifted.  I sanded.  Too much. 

Never relax sanding silkspan.

The person who said "anything worth doing is worth overdoing" never sanded a model airplane!  If you claim you have never had that happen, then you haven't built much.

Ken

Moitch,

A close up appears to show a number of pin holes where what appears to be Polyspan was heat stretched out in the tip area. It also appears you used grey primer (NAPA) and were in the process of removing it in the sand out. I'm curious here about your process in hopes to improve mine.

I have just begun using Polyspan with thinned Butyrate dope to get away from the porous silk that requires many coats of clear to fill. Additionally I have been using Polycrylic on the hard surfaces with doctors paper to minimize in house odors and complaints.

I recently tested brush applying watered down Polycrylic on a sample frame with Polyspan to seal it. You are correct the PC is very hard, it tends to leave brush strokes even thinned and is not easily sanded unless you go into a coarse grit 320 or lower which is risky on the rib edges as you have experienced.

From what I've read most are using multiple coats of 50/50 clear preferably sprayed on to fill and seal the wings. After 3 or more coats and filling the pin holes the Polyspan can be lightly sanded using 400 or higher. Also my experience using the NAPA primer on the Polyspan is it too is not easily sanded off (unlike on hard surfaces) and can add too much weight. Some claim spraying on thinned clear and Zinc Stearate fills nicely and does sand (powder) off nicely.

Hopefully we'll get some recommendations on what is most preferable to use over Polyspan.

Steve

Hopefully we'll get some recommendations on what is most preferable to use over Polyspan.

I have had really good success with waiting to heat shrink the open areas until I had a coat of wet dope applied.  It seals most of the pin holes and prevents the larger ones from opening up if you shrink it "wet" with as low a heat as you can.  Polyspan is heat shrink, not moisture activated so, unlike silk or silkspan, it will continue to tighten when you hit it with heat over still "plastic" dope after the 1st coat and less likely to get those "exploding" pin holes that just ruin your day.  It also lets you use non-tauting nitrate which, in my opinion fills faster.

Ken

Oops, I too missed the Silkspan, not Polyspan - never mind.  You have to put a patch over the tear before there is too much dope on the wing.  Tear a small one and get it on before it is too late to avoid a seam showing.  If you have some lighter grade silkspan use that and put it on wet.

I always use a foam brush with polycrylic to keep from having brush marks.

Mike

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Ken,

What is the recommended filler or "primer" coat used for Polyspan before applying the finish base coats?

Steve

Over the open areas I don't use filler at all.  I use a satin Rustoleum color in what will be my base coat, which is lighter than gloss act like filler and dries super fast.  Sands well with 800+ and seems to fill what is left of the weave.  It is simpler to touch up and shows flaws much better than gloss.  The clear coat makes it all pretty.  I hope our fetish for shiny planes ends before I do cause I like them better without a shine and they seem to fly better and NO HEAVY CLEAR COAT!  I am willing to guess that this preference is not shared by many!

Ken,
Please tell me more about what Rust-Oleum you use for a base coat?

Mike

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Rustoleum has a line of, for want of a better word, pastel and earth tones.  I think it is in the 2x line and most are satin.  By using your final color for both base coat, filler and primer you save a whole lot of steps as long as it is a light color like white.  The plane in the pix has only three brushed coats of nitrate clear over polyspan by shrinking it wet and three light coats of Rustoleum satin white.  1st five sanded with 800 and touched up where needed.  The blue is only two light coats.  The great part is how easily touches up.
Wish I could be of more help but circumstance has forced me kicking and screaming into the MonoKote world.

Ken

Ken,
How long did you have to let the nitrate gas off before you sprayed it with the R-O?

Mike

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I'm in the final assembly stage of the Ercoupe project I'm working on.

I think there's a half a dozen patches in the wing.  One or two are from sand-throughs, at least one is from blithely setting the thing down over a bottle of CA glue that was sitting there waiting to poke the wing, and I can't remember exactly what the others were.

Oh -- and I just put covering onto my Legacy project.  On one half of the wing top I must have dropped the Polyspan, because there's dirt grains between the polyspan and the wood.  So those are going to have to be sanded out, picked out, or whatever, then patched over, and then I'm going to discover the joys of the Polyspan Fuzzies.

So those are going to have to be sanded out, picked out, or whatever, then patched over, and then I'm going to discover the joys of the Polyspan Fuzzies.

The fuzzies aren’t the major deal everybody led me to believe. They disappear pretty quickly with a coat or two of paint and fine sandpaper.
Of course it’s even less of a big deal if you don’t get any in the first place. Just gotta be careful about sanding down into it.