January 7th, 2008 4.5 hrs - 107.5 hrs total. Got Terry on the phone for about
an hour this morning. The two separate issues have two separate solutions.
The flanges are shown with the wrong dimensions on the plans. This is good
news as I've glued 7/8" strips that should be 3/4". Easy enough to run through
the table saw and then sand down to size - even though they're already glued to
the spar webs. I couldn't have made the notches in the ribs bigger because the
lightning holes are too close to the notches to allow them to be enlarged. I
thought about notching the spars or shaving down just that area too. Terry
reminded me that the stab is covered with plywood and is primarily stressed
skin, so most of the stresses encountered in flight are carried by the skin, not the
spars. All of the flanges in the stab are supposed to be 3/4". However, in the
elevator, which is mostly fabric covered, except for the leading edge, the stresses
are more significant so the flanges are 7/8" there. It appears the flange size for
the elevator somehow got transposed onto the stab trailing spar drawing. So,
problem 1 fixed.
For problem 2, slop from side to side (up and down really) in the tab to flange fittings, Terry said it needs a good
positive fit. He suggested I use a strip of plywood glued to the side of the tab, after it's been installed into the spar
slot, which fits snuggly between the flanges. We discussed various fillets and blocking options and decided this
would be the lightest.
Removed everything from the jig. Ran the trailing edge spar - complete with flanges - through the table saw to trim
the flanges to size. Worked extrememly well. Added some more center lines and attach points to the jig. Clamped
the trailing edge and main stab spars securely in place in the jig precisely lined up. Took a while to get this all set up
properly! Mixed up a batch of epoxy and started gluing in ribs. Only got through two ribs when the epoxy started
to cook off. Once it started I had about 30 seconds until the remaining epoxy was unusable. Noticed a very slight
twist in the main spar when pressed down onto the ribs. Decided to stop gluing and work on getting the ribs to fit
just a little better to get the twist out of the spar.
January 8th, 2008 2.5 hrs - 110 hrs total. Re-aligned main spar and checked spacing on all ribs. Sanded the flange
notches on several of the ribs to tweak the fit. Sits mutch better now. Glued in the mid section ribs 1 - 5 on both
port and starboard sides. To prevent epoxy from "baking off" before I could apply it, I poured half of the batch
into another cup. Didn't heat up at all this way and gave me almost 20 minutes of working time. Cut some 3/4 in
strips from 1/8" plywood to make rib tab reinforcement pieces as discussed with Terry yesterday. Made first two
pieces for ribs glued last night, but need to wait for glue to dry to make the rest. Kind of sad to think that all this
work is going to be covered up by the plywood skin.
January 9th,2008 2.0 hrs - 112 hrs total. Finished making the tab reinforcement strips. Got 9 out of the 10 glued
in before the epoxy baked off. I thought I'd use it fast enough to prevent it from having a chance to heat up - but not
this time! Dry fit all the nose ribs. Cleaned up the spar slots and did a little fine sanding in the nose ribs to get them
all to fit exactly and ready to glue. Am ready now except for putting some bracing in the jig to allow clamping of all
the ribs in two planes of motion. Still not positive about which way to do it. Several options available.
January 10th, 2008 3.0 hrs - 115 hrs total. Figured out how to brace the nose ribs when they are being glued. Cut
and fit these bracing pieces into the jig. Marked all nose ribs and inboard jack ribs with centerlines for alignment
when gluing. Should be able to align and glue all the nose ribs tomorrow night. Will post pictures of the bracing then
- if it works!
January 11th, 2008 4hrs - 119.0 hrs total. Decided to use popsicle sticks on the bracing to hold and align the nose
ribs in the jig. Found I could staple them in place with a staple gun and mark the other axis to align with centerlines.
Easy to slide the ribs out to apply the glue, then slide back into accurate position. Even after sp;itting the glue batch
into two cups, it still baked off in about 10 minutes. I made another batch to finish up, left it all in one cup, and in
about 5 minutes it baked off so fast I burnt my thumb on the cup before I could put it down!
|Nose rib bracing added to jig - some scrap 1X2s
|Popsicle sticks stapled to braces
|Alignmnet marks on sticks to match centerline
|Rib tab reinforcement strips in place