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DATE |
PROCESS |
HOURS |
CATEGORY |
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07-04-03 |
Wing Center Section/cabanes *alot of pictures below! |
10 |
wing |
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DETAIL: |
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Over the past few weeks I have been slowly working on the wing center section and cabanes. As you may have read from previous log entries, I am using extruded streamline aluminum struts and cabanes. I got them from www.sky-tek.com. These struts are awesome! Very strong, require no welding to build and are inexpensive. I got all of my strut material for under $300. Since I had my lasercut wing spar plates done and ready I figured it was time to drill the center section spars to accept them. I laid out the location of the plates on the spar and then one by one I clamped them to the spar and drilled through them into the spars. This method was perfect. Each plate now lines up exactly with the holes in the spar. Laser cutting is the way to go if you want 100% perfect metal parts! Since I had already built the cabanes and attached them to the fuse it was time to build the wing center section. The first thing I needed to do was confirm that my angle of incidence was going to be correct. It turns out that the GN-1 plans are not correct and give you only about .5 degrees of incidence. This is probably why most GN-1's fly "tail low". I did the math and figured I needed to raise the front cabane another .5". I did that by inserting a longer aluminum bar into the extruded strut. This gave me 1.5 degrees of incidence. Now I was ready to build the center section. I used some moisture resistant 1/4" plywood at Home Depot for the center section ribs. I traced the shape from one of my built up ribs onto the ply. I cut them out on the band saw. I then cut lightening holes in them. Next, I glued 1/4 x 1/4 cap strip material to both sides of two ribs and then one side of the remaining two ribs. This gave me two inner ribs and a left and right rib for the ends. The cap strip material is needed to increase the gluing surface for the 1/16" plywood covering that will go on later. Before I could begin assembly of the center section I needed to rig the cabanes so they were straight and plumb with the fuse. Otherwise I'd be building the center section on a rickety set of cabanes with no guarantee that later I'd be able to rig the cabanes properly later. I decided to make my wing drag tubes adjustable rather than fixed as the plans show. I did this so that later on if I find that my wing does not sit perfectly perpendicular to the fuse I can lengthen one tube and shorten the other to help bring the wing into position. I made them from 3/8" .083 wall 6061 tube. I tapped and threaded the inside of both ends to accept a 1/4 x 28 rod end bearing. See the pictures. Next I had to find a way to keep the rear cabanes from pivoting fore and aft on their lower attach point. I made some 1/4" plywood strips with two holes drilled at 31" centers. I attached these strips to the cabanes with the bolts that hold the aluminum bars in place. See pictures. Next I rigged the cabanes with 1/8" cable and turnbuckles. For the visible part of the cables that attach to the wing center section I chose to use swaged fork fittings. I think they look much nicer than Nicopress sleeves and thimbles. Once everything was straight I was ready to build the center section. I then glued the ribs onto the spar. I had to space them such that they did not interfere with the bolts that attach the spar plates to the spars. Once the glue had set on the spars I put on 1/16 plywood sheeting on top between the two inner ribs. This was done easiest by using some strap type clamps. These worked great! See pictures. I also put the leading edge
stick in place as well. I figured at this point I could unrig the cabanes
and remove the center section. It's much easier to work on it when it's on
the work bench and not 6' up on the plane. With the ribs glued and one
piece of the ply skin on I figured it was not going to get "racked" or out of
alignment. I took off the center section and placed it on the table.
Next I'll be adding the other two top ply skins. |
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| PICTURES: | |||
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*NOTE* the cheap hardware store type cable clamps
shown in pics are for temporary rigging only.
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