Wings 51, Total 514 Drilling and Dimpling Rear Spar

Last night I finally executed the plan that devised to drill and dimple the necessary holes in the rear spars and the aileron support brackets. To start with, you have to understand that the flanges on the support brackets are bent over 90 degrees to the web, so that means that the angle required to drill holes correctly in the top flange must alos be done at the same angle. Decided to guesstimate this by using the reflection in the alclad aluminum to determin if the drill bit was pernedicular to the flange after clamping the spars to the edges of my saw horses. This worked out just fine I think. One or two of the holes in each support bracket flange may be slightly misaligned from the others, but not to the point where I have to worry about anything.

The above setup allowed me to sit down with the drill at almost eye level so I could focus my attention to the correct angle to hold the drill on the spar flange. Was largely a non-event.

Here the aileron support bracket is clecoed to the rear spar, and the upper spar flange is in position for drilling. I am glad I made the decision to drill these holes now, because they all needed a fair amount of deburring for some reason.

And this is one of the outboard brackets after the holes are drilled and deburred:

And finally is really crappy blurry pic of the inboard upper spar flange holes that must be dimpled ahead of time You can't tell from the pic that the first 10 inches-worth of holes are dimpled with the tank dimple die, but that is what I did to account for the thickness of the wing skin as well as the wing walk doubler plate whose dimples will both need to fit inside the dimples in the spar flange. You must dimple these holes before riveting the spar doubler support brackets in place, because the thickness of the heavy support brackets makes it impossible to get a dimple die in that area afterward. I did the inboard holes with the tank dimple dies in the standard 3 inch yoke with my hand squeezer, and the remaining holes with the standard AN426AN3 dimple dies. For now you only need to dimple the holes up to the end of the length of the forks on each support bracket.

One thing that happens when you dimple these holes, again because of the over 90 degree angle of the spar flange, is that small marks will be made on the spar web from the tip of the yoke. They are not deep and will be scuffed away when the parts are prepped for priming. Just another annoyance with tools that don't quite properly do the job without making some modifications. In this case I would have had to grind down more of the tip of the yoke so that it would not hit the web of the spar as you formed the dimple with the squeezer. I did not do this because I read about the marks in other posts from other builders, so I knew they were nothing to worry about. Riveting them, of course, will be another story, because I will not want to make the same marks after the skins are in place and everything is primed. So that will be a job for the no hole yoke, to ensure that the tip will not interfere with the spar web.

I will say this - I once again used a hand squeezer here instead of that damn air squeezer because I did not want to risk making deeper gouges in the spar web than necessary. I enjoy the better control with the hand squeezer emensly for areas where extra care needs to be taken.

The only thing I think I need to do is dimple the flange holes that I just drilled for the aileron support brackets and the matching holes in the spar flange, but I need to think that one through as well.

On a cool factor note, I attended our monthly EAA Chapter 301 meeting tonight, and saw a presentation by a local builder who appears as though he will be one of only 3 people with a flying kit built replica of a Nieuport 28 WW I biplane fighter in the not too distant future. He presented a snapshot of the kit and the building process. He even already has the replica machine guns to go with it.

This is a way cool kit, and I can't wait until he finishes and flies it. Apparently the owners of the other two flying Nieuports are both in Texas, and one of those is also finishing up a Sopwith side by side seat aircraft, one of which may be at Oshkosh this year. ONe other interesting tidbit is that he used standard BEHR latex house paint to paint the fabric covered wings, because he says that the weight of 4 coats of that paint is actually less than dope or any other polyurethane paint on the market. Very cool stuff indeed.