HP-18 Center Stick Project

Update 14 May 2001:

Now I'm starting to understand exactly what they mean when they say "90% done, and only 90% left to go. I spent almost entire weekend's worth of shop time working on the canopies and frames, and didn't even get the transparencies mounted.

I started by getting the forward canopy frame tweaked to shape and fitted to the fuselage. I got the forward pins in, and the aft slide-in parts mounted. I even got a nice coat of flat black lacquer on the frame.

On the center canopy, I scrounged through the shop, and came up with an entire set of parts for the 18-470-x latching mechanism with only one trip to the hardware store. The four steel brackets were from the original center canopy frame of the Charlie Drew HP-11 N1954, before Steve Brown put the one-piece fore-hinged canopy on it. The steel set-screw collars likewise. The latching rods came from the hardware store. The springs came from an inventory box marked "springs, misc" where I found one plastic bag marked "18-470-5."

Drilling the holes in the frame where the latching rods go through the center canopy frame was a bit of a fright - there's not much opportunity for second chances. But it went fine. Then it was time to drill the matching holes in the forward and wing canopies. That was actually pretty easy, too. I just put the forward canopy frame and wing canopy in place, clamped the center canopy frame into position, and spotted the holes with a 3/i6" transfer punch.

After drilling all the latching holes, I assembled the latch mechanisms onto the center canopy frame. I fitted the latch handles onto the rods by drilling the handles #13 and just (carefully) hammering the rods into the holes. I actually had to cut one of the rods out and do it over when I found that I'd slid the collar and the spring onto the rod in the wrong order. Oh, well, three out of four isn't so bad.

One innovation that I added was a set of ferrules on the rods that limits their travel in the unlatch direction. These keep the rods from sliding out of their holes in the frame hoops. Charlie Drew had done this on his HP-11 using the same setscrew collars as hold the spring in place. I would have used Charlie's old collars, but they were sort of rusty, and of the eight collars he used, I only managed to rescue the four that secure the springs to the rods. However, I just got some 1/4" OD, .035" wall tube, and cut four little ferrules off of it. The ID turns out to be a few thou under 3/16", just right for a light drive fit. I just hammered the rods through the ferrules til they were at the right spot, and done. No wasted material, no extra parts.

Once all that was done, it was pretty late, but there was still time to work on mounting the forward transparency. I got the canopy out of the loft, set it on the frame, and traced the outline of the frame. Then I just used my die-grinder with a grit wheel to cut the plexi to just outside the line, and the 2" sanding disk to cut it to the edge of the line. I figured that that was close enough, and that I'd sand it to the frame contour once the frame and glass was mounted. Next, I masked to the line of the inside edges of the frame with vinyl tape, and scuffed the bond area of the canopy with maroon scotch-brite. Man, that stuff is abrasive! I figured it would take some rubbing to get a good surface. No, it only took a few passes to get a good opaque finish.

Then it was time to do some canopy gluing. Several years back, I happened to pick up at a yard sale several caulk-tubes of that stuff they use to glue windshields into newfangled cars (the ones without windshield gaskets). I figured that it would be great stuff for HP-18 canopies, so I bought all they had. Now, it was time to try it out.

Well, it turns out that the shelf life of that stuff is less than several years. It had kicked over in the tube, and turned into an unspreadable lump of unvulcanized rubber. And so the attempted transparency mounting adventure was over for the week.

But I still think that that stuff has some potential. This week, I'll be going to an auto body shop for some other stuff. I'll get a new tube of that windshield glue and try it again the weekend after next. Next weekend? I'm gonna go to Disneyland!

I spent the last hour or so of shop time working the steel for that batch of landing gar yokes. Those get welded this week.

I didn't get any work done on the instrument pedestal. Likewise nada on the battery box or the antenna. First things first, you know.

page updated 05/14/01 all text and graphics copyright (c) 2001 HP Aircraft, LLC