Finishing Kit

April 27, 2011

Canopy Frame Hinge Pin Blocks - 4.0 hrs.

Today I continued working on the canopy frame hinge pin blocks. Here I ran into my first little snag. The instructions tell you to temporarily remove the F-744 short ribs from the forward fuselage area, so you can clamp these blocks to the long F-745 ribs and drill the second hole. Problem is, I riveted the short F-744 ribs to the bulkhead back when I was working on the fuselage (as per the plans!). The problem was easily solved, however. I just took it all apart and did the drilling on the bench. First, I enlarged the #30 pre-punched holes in the F-745 rib to #12.

With the top hole already drilled in the UHMW blocks, I pushed a bolt through and clamped the block to the rib for spot-drilling the second hole. This means drilling just a short 1/16" into the block to mark the position of the hole. Then it's drilled out the rest of the way with #10 on the drill press.

Here's a shot from the other side:

A while later, after both blocks have been drilled on the drill press for the second hole, both bolts were inserted and the assembly clamped in place for drilling the 1/4" hole for the hinge pin:

Finally, the holes need to be drilled in the short F-744 ribs. To position everything accurately for drilling, it all needs to be assembled back in the plane. First, I drilled the holes in the aluminum spacers and the thin blocks, then put the assembly into place back in the plane. The bolts are in place through the F-745 ribs, and through the blocks and spacer, but just pushed up against the short F-744 rib for now.

Since everything is so flexible and tends to move around a lot, the top skin is clecoed on first. This positions everything exactly where it goes before drilling.

The trick here is to cleco the skin on all around to hold everything in position, but undo one side so you can lift up the skin and reach in there with the drill. I clamped the blocks in place, then pulled one bolt at a time out of the assembly, and drilled all the way through the assembly to drill through the F-744 rib. Then the bolt is pushed all the way back in, and the next one pulled out and drilled. I tried to drill the 1/4" hole for the hinge pin, but due to the curvature of the flange on the bulkhead, there's no way to drill it in place like this. Even my right-angle drill won't work here.

No problem, though. Just take it all apart again and do the final 1/4" hole on the bench. With the two bolt holes located, I bolted the assembly in place for the drilling of the third hole, the hinge pin hole:

Then, it was time to put it all back together once more in the plane to check everything for fit. To my delight, everything fits as it should, and the hinge pins slide easily in and out of the holes for the canopy release. So this part of the project is finished. My cleco pliers and my hands got a real workout today!

Speaking of the canopy release, I now face a decision. I have noticed that most RV's I've seen do not have the canopy jettison handle on the instrument panel. I don't like the idea of having it taking up valuable real estate on the panel, but on the other hand maybe it should be there. Vans designed it to be there. I have found some discussion on this issue, but I still have more reading and study to do before deciding what I'm going to do. I would like to be able to jettison the canopy in the event of an emergency, but on the other hand, nobody has ever jettisoned a canopy from an RV during flight. Would you really have the strength to push it off against the wind blast? Or would it want to come off on it's own if it's unlatched? How would the airplane handle without the canopy on, and with a 150 mph+ wind blast in your face? What about the struts that normally hold the canopy up? How would they become disconnected? And how would the canopy depart the plane without taking the tail off? (or your head!) I suppose in a severe emergency, none of these details matter as much as being able to get out of the plane. But how often will I be carrying a parachute? And what about my passenger? These and many other questions remain unanswered for me. One other thing bothers me. You're supposed to notch the forward top skin to allow for the canopy frame hinges to be able to freely come up out of the plane. This would not only be unsightly, but allow rain and water to leak into the plane, right on to the top of some very expensive instruments and avionics. Not an attractive idea. So I don't know what I'm going to do. I feel like this has suddenly been brought to my attention, and it's in my face. I don't know why I didn't think about this sooner. It just hadn't entered my mind. It's not something you hear people talking about either.

If I do like a lot of builders and opt out on the canopy jettison handle, how do I build the release mechanism? Obvously you must have a way to take the canopy off the plane. I will be studying this issue a lot more before making my final decisions.

And as if that weren't enough to think about, the next item on the list is the canopy latch mechanism on the left side of the cabin. The plans have you cutting a slot in the side of the fuselage skin and installing the latching mechanism that's in the kit. But I've been seriously looking at an alternative aftermarket canopy latch, so I'm not ready to start cutting slots in the side of the fuselage just yet. So far, I've contacted 3 different people regarding the canopy latch I want. It has been passed along this many times just since I ordered the Finish Kit. I hope one will be in production soon so I can order it and get on with it here in my shop. Meanwhile, I'm going to press on with the next thing in the instructions. The aft canopy latch.

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