Jigging Cores

Step 2 MAKING LIFT TABS, INSERTS, JIGGING CORES, LAYING UP THE SHEAR WEB AND INSTALLING LIFT TABS

I have to admit - starting one of the most critical airfoils shapes on the aircraft by bondoing 2x4 lumber onto my jig table makes me wonder. When you see how it's used, however, using anything other than 2x4s would be a waste of time and money. I tried really hard to protect in some way the surface of the jig table by screwing the 2x4s to the table from the bottom after making sure they were lined up correctly.

Here's a shot of the canard sections being test fit into the fixture. You can see the 3" nails pressed into the sides as well.

To be sure the sections were all aligned in height properly, I cut short sections of 1x lumber and placed them underneath the fish tail portion of the canard sections. Resting the tails like this ensured even height all along and then I simply inserted the nails flush with the tops of the 2x4s.

Once the height was established, making them true along the span was in order. Using the string method as specified in the plans, I used a couple of spare pieces of wood on the end for spacing then simply hung weights over the edges of the table for tension. You can't tell here but I've already microed the sections together.

Even with all the jigging and so forth, I ended up with a bump between these two sections (this picture was taken later after the lift tabs were installed. The fish tails and airfoil sections lined up perfectly so I left this bump as is. It must be from a slight difference in hot wiring these pieces. I will sand it down when I do the shear web layup so it will disappear.

I like doing these pieces with CAD drawings. I made up this diagram one Sunday morning while things were quiet then used spray adhesive to fix it to the aluminum.

Here's another shot of the diagram on the aluminum ready to go.

Here are the lift tab inserts, drilled and countersunk and ready for install. I left the one diagram on the insert so you could see I use it for making the part. It's then easy to tear off the paper, clean off any remaining glue residue with some alcohol, then use the part for the next step.

The lift tab inserts were installed per plans method using wood pieces to get the spacing off of the table and some scrap plywood to take up space between the bolt head and threads to avoid driving the bolt all the way in. I drilled holes in the plywood and 2x4s for finishing nails so I could easily remove them for the layup then locate them again easily.

The lift tab insert installed and ready for the shear web layup. Don't forget the silicone caulk to seal the threads! If you don't they'll fill with epoxy and you'll have a task on your hands!

After doing the shear web layup, they tell you to remove the tape and so forth and peel ply. You should do this on most layups that come ahead, like the spar cap layup, where I didn't, and ended up having to sand a lot of tape off from around the edges where it stuck to the epoxy.

Another shot of the complete shear web layup. I had my wife Kelly help with this and it went pretty smooth that way. Don't try to do the larger layups without a helper, you'll get over-tired, it will take too long, the quality of the layup will be worse and you'll make a bigger mess. Sometimes I just have her help me lay out the glass and wet it out, then, I do the squeegeeing and finish it up and she helps again putting on the next layer. Works well because then she's not tied up for the whole time, but, I still get a helper.

Completed shear web layup peel plied and curing. Doesn't look like a wing yet, but, we're getting closer!

After removing the peel ply, the lift tab insert holes were drilled by re-assembling the jigs you made earlier. Here is one side being readied.

Lift tabs installed. This went pretty well with the jigs all done up front. Plans method works really well here.

A shot of both lift tabs installed and flox curing. I spent quite a bit of time scraping away the flox that oozed out from between the lift tab and the shear web.

That completes Step 2 - on to Step 3!