indigoonlatigo(at)msn.com
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 Posted: Tue May 31, 2011 7:33 pm Post subject: lost email found |
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Hi Bill,
My experience was not asking Mr. Loehle himself about how the wonderfil works. I told his wife what I was doing and she didn't think it would be a problem.
I used UV Smooth and Prime. UV S&P is a water based product and does not work in the same chemistry of the poly ester and maybe epoxy primers. I am not saying that one can't spray these primers on top of UV S&P, you just can't do it until the S&P is cured.
As I understand it, Wonderfil is a thickened/ concentrated version of the paint carrier molecule. In the application of it in this manner it is simply a wetting agent.
The problem IMO with using it on the cowl as Loehle shows in his manual is that those defects in the cowl outer surface are not small pin holes, they are craters. Even though the manual states to whip it on liberaly and then whip off the excess, these voids on the surface are filled with a large amount of the wonderfil. I seriously doubt that sraying a layer of primer over the top of it would allow the primer to thoroughly mix with that mass of wonderfil beneath. I like to think of it as pouring epoxy resin into a cup and then adding the hardner into the cup and maybe making one or two stir strokes with a tongue depressor. The result is that only the two chemicals that immediately touch will react, leaving everything below that not cured.
So I Wonderfilled the the cowl surface and then whipped off the excess and then rolled the UV S&P. It was like painting over a pitted waxed surface, bonded in some spots(where there was no Wonderfil), enough to cause serious grief in later removal and totally not bonded in others.
I am not saying that Wonderfil does not work on pin holes, I am saying I would not use it on the rough surface of the cowl and not with other products that do not use this chemical for the carrier molecule.
The cowl has a problem in the production of it. The outer glass making up the skin pulls away from the mold once the Nomex honeycomb is added making only the glass which is on contact with this honeycomb actually stay pushed against the mold. The result is the huge craters I refer to.
To correct this, one needs to add a lot of effort making up for the lack there of on the producers side.
No matter what system used to correct for this, speaking from the experience of an anal retentive dentist, how one effectively roughens and gets a true bond to the bottoms of these craters is a complete mistery???????????????
Corn blaster or sandblaster would work great, but would destroy the part and or add the weight of the beach to the front end of your airplane.
I removed all the UV S&P and then made a slurry of chopped glass and epoxy, squeggying it over the cowl and then after cure, sanding it out again. From there I leveled it out with Epoxy and Micro ballons
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