Chapter 21: Glassing the Strake Tops and Bottoms
A word about "Sag"
I was pretty happy with the top installation until I came back the next day and saw the sag between the R33 and R57 ribs. Apparently, this is a common problem that's well-reported in the archives. What happens is that the top skins want to sag between the R33 and R57 ribs, starting at 2 inches aft of the leading edge bulkheads and ending about 8 inches aft. So, we're talking an area of about 2 feet wide by about 6 inches fore/aft. Nothing drastic mind you, but still noticeable and still a pain in the patooty to fix. This is not due to my workmanship; just due to trying to bend a flat piece of fiberglass around curved surfaces. I have a choice of fixing it now, or glassing now and filling with micro later. I choose to fix it now by microing in strips of blue foam and spline sanding nice and flush.
After discussing the "sag" with Norm Muzzy, we both wondered if it would have been worth the effort to install two additional ribs and a cross member to stop the sagging. (My starboard "sag" was about 3/8-th inch deep and its deepest spot; the port sag was 1/4th inch deep.) But all in all, this "fix" was easy to do.
By the way, the answer is "NO!". The drywall screws DO NOT penetrate the inside skin. They are only there to hold the strips in place while the micro cured. And yes, you bet the holes got filled with micro before glassing the tops!
Glassing the Tops and Bottoms
The plans have you flip the plane upside down and glass the bottoms first. I saw no need to do this. So I glassed the tops first, then flipped the plane and glassed the bottoms.
I sawed off the tips of the R33 and R57 ribs to make the glass overlap easier to accomplish over the leading edge bulkheads, and to prevent leaks. Trying to notch out the UND cloth to fit around the rib tips, and then trying to seal these areas is just asking for trouble. I saved the tips and will simply flox them into place as guides for carving the leading edges.
Prior to glassing:
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I spline-sanded the tops and bottoms as best as possible with a 4-foot board. I sanded until a straight edge laid on the strakes aligned with the inside of the wing root cuff. Why align with the inside? To allow room for the thickness of the two layers of UND applied to the strake skins! When you do this, make sure you align the straight edge parallel with the leading edge. Don't align side to side or else you'll get the wrong answer! In fact, I used the slits in the foam as a guide, laying the straight edge in the slits and checking alignment to the wing root at each slit.
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I next sanded a 5-inch wide joggle on the outboard diagonal to account for the thickness of the 5-inch-wide UND layup. (I glassed the 5-inch-wide UND first.)
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I sanded a 2-inch wide joggle into the leading edge to account for overlap of the BID later when the leading edges are glassed onto the leading edge bulkheads.
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Finally, I spline sanded across the major flat surfaces to make damned sure there were no obvious high spots! Better to be slightly low and use a little micro fill than to have a bump and use lots of micro to hide the bump.
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And yes, I did peel-ply the entire top and bottom surfaces.
After cure, I was VERY pleased. The strake tops aligned very nicely to the wing roots. Woohoo!
Help Arrives
Glassing goes alot faster when help arrives! My buddy George (on the left) came up from Florida to visit during the Christmas holidays and we promptly worked all week on the plane. A member of George's church, Wayne (too!), stopped by to say hello and we promptly gave him gloves, a cup of epoxy, a squeegee and put him to work! Since the plane's at the airport now, I get ALOT of impromptu visits. Metal pilots are always mystified by the fiberglass construction. They think it takes a PhD to do this. Rather than perpetuate this ruse, I get them involved. After they don gloves and help with a few hours of glass work, some of the mystery is taken away and they think the Cozy is really cool! Of course, four seats at 200 MPH leaves them j-e-a-l-o-u-s!
And by the way....as I write this, it's December 30, 2001, and it's C-O-L-D! That doesn't stop me from doing work on the plane. I use a kerosene jet heater to heat a local area in the hangar, then use heat guns and hair dryers to keep the foam, glass, and epoxy nice and warm. For cure, I construct a heat tent -- nothing more than an electric space heater under a temporary frame with some tarps and blankets thrown over it. Definitely not as nice as Cozygirrrl's heat tent, but it does the job nonetheless. :-)
