Part I was getting all the spars and ribs straight, and cleco'ed up. This was pretty simple. Then came the modification of the centre ribs to allow room for the 'spar web' in the middle - again, pretty simple.
Then comes putting the right skin on. Not simple, not straight forward. You think its just lay the skin on, put it in position, and go to town... no so. The 'jigging' process basically has to take the bow OUT of the spars. So, I turn to the Glastar.net forum - which is an AWESOME source of wisdom. Lots of guys have been here before, with lots of pics and advise.
So you basically have to build a jig to hold the spars straight in both axis AS you line up the skins.
Lots of swearing, thinking, and reading...
So here was my solution.
- My workbench is level, with very straight edges
- I made some blocks out of 3/4" ply that go in both the horizontal and vertical axis so I can butt the spar / skins up against it. I know those 2 axis are straight (or at least I sure hope so).
- I clamped the bottom of the aft spar into that L brace with wood clamps and blocks (of which I have plenty). Now I know that the aft spar is straight in 2 axis.
- As luck would have it, a 2x4 on end match up perfectly on the forward spar. I clamped the right outboard end, and 2/3rd of the way down
- Using the level method in the manual I verified lack of twist at every rib location along the way.
Pics below.
Going to give it a rest for the rest of the night and recheck for twist tomorrow before I commit to drilling. Once the holes are in, "it is what it is".
The forums has a variety of ideas, from building a steel truss work, to L channels, to standing it on end. I have no doubt these are all valid approaches. Bottom line is you need a straight / flat reference to butt everything against, with a steady reference from end to end to make sure the entire structure is straight / twist free.
Time for a break, and a double think before committing. The drilling will go fast.
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