Matt's RV-7 Project

More work on the top cowl mounting strip, to which the camlocs will eventually be attached. The spaces between adjacent camlocs need to be notched out so the remaining aluminum can be shaped to conform to the tapered cowl shape. I taped over the pilot holes for the camlocs – to keep myself from accidentally enlarging them prematurely! – and started each notch with a hole whose edge is about a quarter inch away from the end of the fuselage skin.

A lot of cutting, filing, and shaping later, here's the finished product. If you can get to this point in building the airplane, you should be able to make this part from raw stock with no problems, so I won't bore you with a detailed step-by-step.

I found that it was handy to have a variety of rotary files and scotchbrite wheels to chuck up in the drill press. And yes, you can cut all the notches on a small bandsaw if you plan carefully.

I will have to make finer adjustments later, but for now I just roughly bent the two most outboard tabs on each side to generally match the cowl shape. The easiest way to do this is to put it in a vise with padded jaws and wail on it with a rubber mallet.

The finished product clecoed in place, one of many trial-fittings it took to get to this point. You'll notice that I also trimmed down the side pieces that go below the bend at the upper longeron. I resisted the urge to put one more camloc down the side, since there needs to be a gap between the camloc strip and the side hinge in order to insert the hinge pin. Luckily I remembered now and not after finishing the top cowl!

Wow, whatever I had really knocked me for a loop, but thanks to modern medicine I am mostly over it at last. Irregularly-scheduled blogging will now (sporadically) resume.

I pulled the forward top skin out of storage and clecoed it to the fuselage:

The cowl on my last airplane was attached with a combination of quarter-turn camlocs and piano hinge, instead of using hinges everywhere as the plans show. That seemed to work all right, so I've decided to use a similar setup on the current airplane project. The bottom cowl will be attached to the firewall with straight sections of piano hinge, and I'll use camlocs to attach the top cowl to the firewall and along the horizontal seam between the top and bottom cowl halves.

The camlocs need a metal backing strip attached to the fuselage, to which the camloc receptacles will be mounted. I cut a 3" strip off the end of a sheet of 0.062" alclad (gee, I really wish I had a big metal shear) and shaped it with hand pressure until it conformed to the curve of the firewall.

While clamping it carefully in place, I match drilled every other hole through the forward edge of the top skin and the firewall flange. If you plan it carefully, you can use a single piece with no compound curves that runs from a point just above the upper longeron all the way over to the corresponding spot on the opposite side of the firewall. Then you add small filler pieces below the firewall bend line, which I'll show in a bit.

To mark a trim line a fixed distance forward of the firewall flange, I drilled a 1/16" hole at a suitable location in a piece of scrap aluminum, stuck a pen through it, and dragged it along the mounting strip. Simple.

Lots of cutting and filing later, I had the mounting strip trimmed down to size.

It's hard to see here, but I've now marked and drilled #40 pilot holes where the camlocs will eventually go. You can also see one of the extra filler pieces that brings the line of fasteners all the way down to the horizontal cowl seam.

The instructions recommend a maximum spacing of 3.5"-4" between adjacent camlocs; however, since I remember seeing the cowl "pillowing" between fasteners at high speed on my last airplane, I decided to reduce the spacing to 3 1/8". That also helped keep the hole pattern away from the split between the main piece and the two smaller pieces.

Bleargh. I have been sick for a week. The only thing I've had the energy to do is to trace a circle onto a piece of MDF and cut/sand it to make an accurate copy of the spinner backplate.

I'm not even sure why I did this. It seems like it could be useful for cowl fitting later on.

I'm going to go lay down now.

Well, there's no sense in avoiding it any longer… I have to start on the cowling sometime.

The first step is to mark and cut a hole in the top cowl for the oil door. I ignored the dimensions in the plans and cut a hole that's more of a square than a trapezoid, since I have in mind a different arrangement for the hinge and latch.

I spent some time sanding the edges smooth, because I'm fairly certain I'll be spending a lot of time reaching my tender arms through here.