Jig drilling spar caps

[X'N]

My plan was to make a cnc cut jig from steel about 2 feet long and advance the capstrip along it drilling them to -4 on the main and -3 on the rear and then upsize them once clecoed together on the spar. Any advice from people who have been here on things to avoid?

[Gavin Chester]

I did similar on my Bear Hawk . I laid out all the important and dimensioned holes on the drawing then worked in between.
Particularly at the strut attach point ,Flap and aileron drives and rear spar hinge mounting points. In reality it did not get much use !
I only laid out and drilled one spar on one side ( undersize), Then I used it as the drill jigs for all the other pieces. You will need some nuts and bolts to join for drilling.

[Glenn Patterson]

We laid the cap strips on the spar,marked the rib intersection & critical holes then gang drilled all 4 cap strips at one time. Pulled them apart and used the one that goes against the spar as the drill template for the spar. Once the spar is drilled the other 3 predrilled cap strips are added to complete the cap strip assembly. The holes were all done one size down then were drilled to their final size in place. It simplifies getting the cap strips on both sides of the spar to be located exactly the same. A trick we learned on the rear spars that would have helped earlier was to install the top spar caps trips. We then used a chop saw with a stop to cut all the verticals to the same exact length and then laid them on the spar. The bottom capstrips were pushed tight to the verticals and drilled. This saved all the fussing about to get the verticals to fit between the capstrips. If it is off a few thousandths it is not that critical but it does save time. Attached is a clip on gang drilling that may work with a jig if interested. Glenn

[Glenn Patterson]

The air drill shown was tossed very quickly & we used cordless drills all the way. Air drills whine, the compressor is running & fighting the hose is a PIA. The capstrips were drilled with an 18v cordless that we had but our primary weapon of choice was a DeWalt 12V. The DeWalt 12v has great torque & a battery will drill holes for about 3 hours. We bought a second DeW drill & use both all the time. Glenn

[DRLPatrol]

Nice write up Glenn, Thanks
Doug

[X'N]

Thanks for the replys guys. Nice write up Glenn you should put that in the tips section!

[Glenn Patterson]

I posted it over in tips with some further though that may save time.
GP

[S Lathrop]

I made a similar drill jig. It really saves a lot of time.

I made the jig the same width as the cap strips on the main spar but cut the ends down to the width of the rear spar cap strips. That way I could use the same jig for all the cap strips.

I drew the wing spar out in cad. When I calculated the distance between rivet holes so that the holes lined up with the positions of various elements of the wing, such as the aileron drive and aileron hinges, I had a rivet spacing very slightly different than what is indicated on the drawing.

Steve #623

[X'N]

Well I took the time to lay it all out in CAD and I'm glad I did! I found 1.02083 (yea I know its an unrealistic measurement to hit in the real world) was the rivet spacing that lined up the best. So Bob's spacing of 1.021 is spot on (this is on a patrol). The thing I didn't realize until I overlaid his drawing of the main spar splice is he moved some of the rivet holes so the strut bars don't interfear with the rivet heads. Had I not done this I would have just drill the cap strips down the line and ended up having to fix them...

[X'N]

Jig is complete. I was going to make 2 jigs one for myself and one for a friend who is building a 4-place but I decided to just make one steel piece and 2 bases because I had the material on hand. All in all they should work great!