HI All,
Has anyone used Poly Span over the "kept foam" wing system?
TIA
Bill <><
Bill,
In my experience, the dope WILL attack the foam, but not to an amount that is significant. I built a Dixon "StuntWagon" which uses the 'kept foam' technique.
As you apply the first few coats of dope, look carefully and you will see a change in the *texture* of the foam directly under the open bays. Some vapor from the dope is trapped in that small cavity between the Polyspan and the foam core, but the volume is small, and the reaction with the foam is very minor.
As subsequent layers of dope are applied, eventually this reaction will diminish and stop as the Polyspan is filled. If I were to venture a guess as to how much foam was "melted" I would say probably 1/32" to 1/16", not enough to effect the structural strength of the wing.
I believe that it was Todd Lee that had this situation cause a failure of his "Mustang" wing, but in his case, he had removed much of the foam between the capstrips, which left a large void that could contain a large volume of dope vapor, and consequently, a major damage to the remaining foam and an ultimate failure. If I don't have all those facts right, please someone feel free to correct me.
Go for it, Bill.
Cheers,
Warren Wagner