Wednesday November 08, 2006
Wednesday November 08, 2006 I've actually completed the initial fiberglassing of a few parts of my airplane. The elevators are glassed as well as both winglets.
|
Here you can see the first layup on one surface of one of the elevators. The weights are there to convince the foam to remain flat with the surface of the table. In the background you can see the second elevator being glued down temporarily with 5 minute epoxy to the table surface. Once the top surfaces are complete the elevators are popped off the table and flipped over and the second layup is done. Because they are glued to the table when you pop them off the foam on that side is damaged. Normally with dings and voids you'd fill them with a dry mixture of epoxy and micro-balloons. Weight is critical on the elevators so instead the damage is filled by "pour foam" (like "GreatStuff" only you mix it yourself). The cloth used in this layup is called UNI. It has major fibers running in only one directions. It has a cross fiber running only enough to keep the cloth somewhat stable. In these layup you cut 8.5 inch strips on a 45 degree bias. So from the 40 inch roll you end up with pieces about 28 inches long. So it takes about 2.5 pieces to cover a 72 inch elevator. The layup is two layers of glass with the fibers perpendicular to each other. Because the cloth is UNI and narrow if you look at it wrong the 8.5x28 strip becomes a 4x40 strip in a moment. It's really a pain to control.
|
|
It took me more than an hour to do one layer of glass. At first I was pretty frustrated trying to get it to lay right. The second layer went faster but still the first layup took about 2.5 hours. In the construction videos it took about a half an hour to do both elevators. When I did the first surface of the second elevator it took about 1.5 hours. For the second surfaces I did both elevators at once and it took about 2 hours. Still pretty slow but improving.
After that I started on the winglets. The first thing you do on the winglets is install the comm antenna(s). One of the advantages of a fiberglass airplane is that fiberglass is transparent to radio so the antennas can be inside the airplane and not out in the airstream producing drag. (One of the disadvantages is that a lightning strike in a composite airplane is a much bigger deal than in a metal airplane).
|
Here you can see the antenna preparations. The antenna is a simple dipole using copper foil (like used in stained glass) for the elements. They are just stuck to the surface of the foam. The coax is embedded in the foam and then covered. The manual say to cut the foam track by burning it with a soldering iron and to cover the coax with dry micro. I cut the slot with a router and covered the caox with pour foam. Pour foam is a lot easier to sand into shape and less bother than making up the micro. The winglet is laying on the piece of foam it was originally cut from. There is a curve on the surface of the trailing edge and in order to preserve that gentle curve instead of glassing the winglet on a table you let it sit on the other foam piece until the initial layup is complete.
|
|
|
Here you can see the winglet covered with the fiberglass cloth. This layup was also done with UNI cloth, two layers. The first layer had the fibers parallel to the trailing edge and the second layer the fibers are parallel to the leading edge. The larger cloth was much easier to deal with than the cloth for the elevators. The foam beneath the trailing edge is covered with aviation grade release tape (duct tape) so that the winglet can be popped of the lower foam form.
|
|
To the right is just another view of the winglet while it cures. The cloth you see at the bottom edge (and actually is on the trailing edge too) is a strip of dacron that is called peel ply. It doesn't stick to the epoxy and you can peel it off after the cure and you get a surface that doesn't need sanding if you are doing a later layup. It also tends to remove excess epoxy resin and excess resin only contributes weight, no strength. It is also good to use to get a smooth transition from one are to another. Peel ply can reduce the amount of sanding you have to do and anything you can do to reduce sanding in a composite airplane is a very good thing.
|
|