2 hr
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( 3 / 15 )Yep, more gussets.
4 hr
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( 2.8 / 11 )The pictures show the jig along with batches of gussets in small plastic containers.
You can also see that I changed the rear spar dummy block from the first picture shown above. I wanted a little better quality control over the size of the space left for the rear spar, so I made the dummy block full size. I may be sorry later when it comes time to release the rib from the jig - time will tell.
6 hr
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( 2.8 / 33 )Gussets continued...
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( 2.8 / 26 )As many other builders have done, I decided to set up a small mass production facility to make ribs. That meant cuttiing a lot of gussets. I made some simple jigs to ease cutting of approximately 700 or so small wood parts. Only a few of the gusset shapes were able to be used in more than one place. All the rest were custom shapes. I'm planning 50 gussets for each location - 20 double sided ribs, 4 single sided ribs (at wing root/fuselage sides), and several scratch/test ribs. One exception is the gusset nearest the trailing edge, which is only placed on one side. I made 30 of that one.
The gussets were all cut from 1/16" GL-II Finish birch plywood. I got mine from Wicks Aircraft. It truly is beautiful material - perfectly void free. I started by ripping the sheet into strips. Gussets were then cut from those strips.
I had some trepidation regarding grain orientation. The plans appear to show the face grain running chordwise on the rib. Tony Bingelis says run the face grain up and down, or at a 45 degree angle for "L" connection gussets. My structural engineering background tells me Tony is more correct. Wood Aircraft Building Techniques also says to orient the face grain up and down, unless the plans say otherwise. In the end, destructive testing has shown me that is doesn't make a difference for this design. The rib sticks fail first outside the glue joint. Furthermore, with rib stitching most of the joints are in compression anyways.
Since I had already started ripping the strips with the grain lengthwise, I stuck with what the plans appear to show. The funny thing is, even though Mr. Bingelis, my structures instructor and the EAA say it's best to run the face grain up and down, nearly every example aircraft I have seen runs the grain the way I am. Even these gussets for a Pitts Model 12 (an aerobatic biplane) have the grain running chordwise.
Most experienced builders will tell you to wait until later in the build to start making gussets. The argument goes that the scraps from other stages of construction will make more than enough gussets. Well, I don't really have that option because I am starting with the wings. If I end up with a lot of extra 1/16" ply left over, I will just build another plane. :)
1 hr
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( 3 / 20 )I completed the jig today (who really spends 8 hours on a bloody rib jig), so I set about making dozens of PVC clamps of various sizes. If you've never seen a PVC clamp, they are simply 1/4" - 5/8" wide rings cut from a length of PVC pipe. I used 2" and 3" pipe. Each ring is then cut such that it can open up into a "C" shape. Take care so that the clamping flats are cut in such a way as to not ding or gouge the wood when used. I cut mine so that the flats were parallel when the clamp was opened up about 1 1/2". Wider clamps have more force, so be sure to make a variety of sizes to fit your needs.
2 hr
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( 2.9 / 16 )I've continued attaching blocks to the jig in all the necessary places. I am mostly done, with just a few of the more complicated junctions to finish.
I was thinking of trying to use a cam device made from the HDPE to act as a clamp as I've seen other builders do. The problem for me was getting acceptable round cams from the plastic - they always came out slighly tapered (due to the tooling heat) and therefore wouldn't clamp evenly. I decided to just try the PVC clamps everywhere.
4 hours
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( 3.1 / 26 )I scanned the rib plan sheets into Microstation (our office CAD system) and reassembled the images so the dimensions matched. Then I printed the assembled image out on a plotter.
I layed the plan over a sheet of 1/2" particle board, then cut the board approximately 1" around the perimeter of the truss portion of the wing rib. I then covered the whole works with waxed paper.
I started started screwing down blocks of high density polyethylene (from a kitchen cutting board) to hold the sticks and gussets in position. I am hoping that if I take my time and hold some tight tolerances, I will have a jig that allows me to glue on both sides of the gussets in one shot without using nails or staples.
2 Hours
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( 2.9 / 26 )
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