By Bob Reed
When I built the mounting jig for the horizontal stabilizer, I followed the plans exactly. It started out ok but after mounting the top of the stabilizer in the jig and starting construction, the straight edge board warped slightly and transferred that warp to the trailing edge of the stabilizer. It did not end up as an unrecoverable problem but it did teach me that the jig is important enough to do it right and make sure it is built to do it's job. So when I got ready to build the jig to hold the wings, I listened to those who had gone before me and built it with extra ribs. I also wanted to try and use materials that started out straight and true and would probably remain that way. The humidity in Houston can cause just about anything to warp.
I picked prefinished 12 x 48 inch shelves of 5/8 inch MDF boards. Using the kit supplied pattern I cut a total of 12 ribs to roughly the shape of the pattern. I then shaped one board to the exact size of the pattern. Once satisfied with the initial rib I used it to produce 11 more exact copies. For the rails I selected the best and straightest Red Oak boards I could find. They were expensive but they were also straight. I assembled the system using these and anchored it to my work bench which had been leveled. I assembled the whole thing with dry wall screws. Everything was repeatedly checked for level and square.
|The best method I have found for duplicating
a wood part is to use the router. The whole
process took less than an hour.
|All complete ribs were clamped together and
checked for true match. The process was
good enough that you could not feel any
edges as you rubbed your hand across the
surface. I used the same process to cut the
slots for the center support.
|I placed the rails together and marked the
position for the ribs on all three at the same
time. I used wood block to provide the
exact position of each rib. I then used 1x2
wood blocks to position and anchor the
whole jig to the top of the workbench.
|All the ribs are screwed into place with
liberal anchors placed to hold the jig in the
|This shows the position of the jig on the
work bench. It should last through both
wings without warping.
|It is straight and true. I also added 1x2 oak
ledge to support the back edge of the wing.
This is a strait edge which I used to bond the
wing down along the full length of the trailing
edge. I used 1x2 boards to clamp the edge
down while the bonding cured. The full wing
was bonded down at each rib to hold it. It
required bonding since the wing had a very
strong curl to the inside.
Overkill? Well maybe, but I would rather err on the side of caution.
After mounting the first wing skin top I think I may have made a good
decision. I used a epoxy-flox mix to bond the wing into the jig. I
had to use screws to pull the front edge of the wing down into the proper
position. The epoxy-flox was used after attempting to use bondo and
it failed to hold. I made sure to not sand or clean the wing skin so
that the bond could easily be broken when the wing was complete. I
will probably have a bit of a time getting it out but it will stay until
I am ready to take it out. I will update this when I take the first
07/31/2001 - Removal of first wing from the jig was no problem. The EpoxyFlox mix had held tight through the construction process and released with a bit of friendly persuasion (lifted the wing from the front and slowly poped the bonds loose.) and left a very straight edge. Overall the jig worked as planned and had no damage from the first wing. Even though all the duplicate ribs I used are probably not required I highly recommend their use for the added support it gives. Besides, it only takes a few extra minutes to duplicate the ribs using the router. A little clean up and some light sanding was all that was necessary for preparing for the second wing.