March 21, 2013 - Upper Wing Spar
Ladders |
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With the spar flanges done, the next step was to build the spar
ladders. Each spar ladder consists of two spar flanges with
the swallowtail (SWT) blocks and flange spacers between
them.
Here I have laid out two spar ladders with the SWT blocks between
them. Both spar ladders are for the upper wing box
spar. |
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I had made the SWT blocks previously
but I still had to make the flange spacers. They are made from 5/8"
x 2" stock. So that they would fit tight against the spar flanges,
it was important to make them perfectly rectangular. The table
saw is best for making precise cuts so I used that. |
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| Because the spar
flanges are tapered, the height of the flange spacers is
variable. In the below picture, I have cut all the flange
spacers but have not cut all of them to height yet. |
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OK, all of the flange spacers are cut
to height. I also drilled 1/4" holes in them per the plans. I
think the holes are so air can circulate through the box spar. |
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| Gluing the first
spar ladder. It took me over an hour to apply the T-88 epoxy to all
the surfaces. It's hard to see what is going on because of all the
clamps and hold-down bars. Plus the ladder is wrapped in wax paper
so it doesn't get glued to the spar table. |
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| From another
angle. Lots of clamps were required. Fortunately 8" bar
clamps can be had at Harbor Freight for $4 each. |
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| And the first spar
ladder is glued! |
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From another angle so you can see how
long it is. It is for the upper wing and is 21 1/2 feet long. |
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| My lazy assistant. |
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A trial clamping of the second spar
ladder, in preparation for gluing. |
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| Close up of the
flange spacers. |
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| The second spar
ladder has been glued. I took this picture to give you an idea how
the spar ladders go together to make the box spar. The ribs slip
over the box spar as shown. There will be spar spacers in between
the two ladders. These have yet to be made. Each ladder
gets covered with thin plywood. The entire box spar gets covered
with plywood as well. So a lot of work remains to be done. |
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| From another
angle. |
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| The flange spacers
get triangular gussets on each side. These were easy to make using
the band saw. |
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| A flange spacer
with gussets. Not glued yet, however. |
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| I cut gussets for
all the flange spacers. Ready for gluing. |
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