But wasn't Steve's problem that he didn't follow the manufacturer's instructions and used incompatable products (or ones that didn't bond to each other well) in the O-O Special?Originally Posted by highflyer
But wasn't Steve's problem that he didn't follow the manufacturer's instructions and used incompatable products (or ones that didn't bond to each other well) in the O-O Special?
Yes, he attempted to stick down polyfiber fabric to the wood using nitrate dope. While that would work with cotton where the dope could wet the fabric, it didn't with the polyester fabric. Polytak would have been the proper adhesive. You're going to have to do the surface prep recommended by the manufacturer. For polyfiber over wood, that's two part epoxy.
If it helps, I will offer the info that every modern recovering method uses polyester fabric and has you prime tubing and varnish wood before adding fabric. I pull 6G's two or three times a week flying a Pitts covered with Cooper Superflite. Fabric over varnished wood and primed tubing. No problems with adhesion.
Modern fabric adhesives work fine over varnish. But as mentioned previously, you need to follow the directions and not fudge as you go along.
Today I would not own an airplane covered with cotton. Grade-A is very hard to find these days and it does not last like the new materials. And it degrades by the calendar. Why guarantee that you have to rip it all off and do it over any sooner than you have to?
Every manufacturer publishes manuals with enough detail that you can do a decent job. Do be careful of shelf life though. Some of the new water based finishes can only sit on your shelf for a few months before they have to be thrown away. A friend learned this by having to stip down and redo his wings when the finish dod not come out right. So put off buying finishing stuff until you really need it.
Best of luck,
Wes
P.S.
I visited Steve Whitman at his home at Leward Air Ranch a few months before his crash. Very accomplished guy, but very willing to answer questions about his latest project all laid out in his hangar.
As stated, poly-fiber requires wood be painted with the two part epoxy. Not left bare, not varnished,
Lord only knows what investigators would have decided had Steve Wittman used polyester fabric that was not ink stamped ever 36 linear inches with "polyfiber." There are other polyester covering systems where the instructions require nitrate dope over plywood before covering. Even though polyester fabric for different "processes" comes off the same weaving loom, once the ink stamp is applied, the fabric will only work with that company's proprietary finishing products - wow! I never knew ink was so powerful! I wonder what happens when you use "uninked" a.k.a. uncertified polyester fabric? Only uncertified coatings will work? Just wondering as all the major outlets sell uncertified polyester fabric for homebuilts, ultralights and such.
Last edited by martymayes; 04-25-2012 at 06:53 PM.
The problem was not that he doped the plywood, the problem is he attempted to use dope as the SOLE ADHESIVE in holding down the polyester fabric.
It wouldn't have worked any better with ceconite. While ceconite says to prime the wood with nitrate dope, it doesn't say to use dope as the adhesive. It says to use their cement. You can not bed any polyester fabric in dope (regardless of who made it) and expect it to stick structurally. This only works with the natural fibers because the dope wets into the fibers.
Of course, if you're not up on the materials enough to understand what will and will not work chemically and structurally, it would behoove you to follow the instructions rather than conjuring up some great conspiracy between the NTSB and the fabric manufacturers.
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