Building Tips and technical articles. > Paint and finishing
SLC OVER Polyspan?
Andrew Tinsley:
Hello Larry,
I don't have a clue what SLC is, but it sounds as though your system is similar to mine. I cover the airfame with very thin mylar that the FF boys use. Stick it on with balsaloc or thinned down impct adhesive. then cover with dyed silk and one coat of 50/50% thinned dope. Fuel proof to taste. It is incredibly strong and lighter than silk onits own as you don't need to seal the silk.
Andrew.
Larry Renger:
Nope, sorry, you have completely missed the point! The Polyspan, silk, japanese tissue, or silkspan is attached only around the periphery, then the SLC (super light covering, a vey thin Mylar with adhesive coating) is applied OVER it and heat bonded to the fiber underlayer. The fiber layer, whatever it is, is NOT DOPED IN THE OPEN BAYS. The SLC provides both the function of filler, binding film and fuel proofing even if no other finish is applied.
The result is a composite covering that is incredibly light, tough and rigid, but fuel proof or paint ready without multiple layers of dope and filler.
This way of covering is exactly reversed from your standard practice of covering with SLC then applying one of the fiber coverings doped over it. Yes that works, but you still have to then apply dope to fill the fiber and fuelproof it. Putting the SLC on top of the raw fiber gives you the same strength with a LOT less work, time and weight. Also, IMHO a better finish than I have the patience to achieve otherwise.
As mentioned elsewhere, with Polyspan, the result weighs. only 1.4 ounces per sq.yard.
Bill Little:
--- Quote from: Larry Renger on July 23, 2013, 04:24:11 PM ---With out doing actual destructive impact tests, I believe the composite of fiber and film is way tougher and more rigid than either alone.
--- End quote ---
Hi Larry,
I agree 100% on your supposition that the two, together, are stronger than either alone.
BIG Bear
RNMM/AMM
Larry Renger:
One day of flying, and so far, no separation. I will keep everyone posted on how this technique works out on the long term.
Larry Renger:
Two weeks later, all is still staying stuck where it is supposed to. So far, so good. Give it a try! No dope on the Polyspan, the SLC bonds to it and stabilizes the structure like you wouldn't believe, and then provides a totally smooth surface for painting (after you rough up the outer surface with wet sanded 600 grit) I don't think you even need primer! Maybe for a 20 point finish, a primer coat and blocking coat might be needed, but not for us normal mortals.
Think about it, 1 sq yard will cover just about any model you can imagine, and it only weight 1.5 ounces ready for paint. What does a dope over tissue or Polyspan surface weigh for that area? or even a Polyspan OVER SLC? You are totally eliminating the filler coats of dope to achieve a smooth surface, not counting the time and effort required. The bond between the SLC and fiber is really strong. Dope would just get in the way.
My next trick is to try some of the ultra-light park flyer coverings over the Polyspan to get color without paint at all!
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