HP-24 Project

I told everybody that I'd put in enough shop time for a while, and that I was going to stay away this weekend. I had to bring the kids down to see their grandparents who were in Manteca camping in a trailer down by the river. Some friends were going to climb Crack of Doom, a notorious offwidth with substantial stretches of unprotectable climbing. And there was some other stuff to do around the house, including cleaning and screening the gutters.

Well, that's not the way it worked out. An email and a couple of phone calls have suggested a resurgence of interest in some composite techniques I worked out for a long dormant one-off glider project. It rained on Saturday, making Crack of Doom improbable at best (Spyork, let me know if otherwise). And the weather Sunday was kind of drab but showing improvement, and I figured if I got to the shop early I could scoot by noon and drag the kids off on a hike or something that they'll later remember as "character building." Yeah, right.

Well, most of that worked out. We got to the shop early Sunday, did our 12" square test panel, got it bagged, and got out a little past 1pm. Then I took the kids and the puppy for a hike out to an old mine site a mile north of Parrott's Ferry Bridge. I got a good GPS mark at the crankcase of the old one-lung motor the miners had left, and on the way back we collect a full bag of recycle for the funraising drive for one of Brigitta's friends who just went in for brain surgery (it went well and she's doing fine).

Monday morning, Brigitta and I got up five-ish and went up to the shop to unbag the test panel and switch off the heater. It went fine, and the test panel looks great, successfully validating several aspects of the proposed schedule. Then I headed off to work.

The photos:

Okay, so I did do some HP-24 work. Here I am cleaning up the elevator molds a little, including rescuing the trench feature.

We also got some of the house upkeep done. We needed screens for the gutters, but didn't want to sit there chopping away with snips for an hour. So we wound the aluminum screen around one of the heavy cardboard tubes that fiberglass comes on and ran it through the bandsaw. Took five minutes tops.

Here's the polished aluminum surface of our CNC cut test mold, with the test panel internals in position. The sharp edges are taped to keep them from cutting the vacuum bag. The blue stuff is foam, the thick black strip is a couple of large pultruded Graphlite strips.

Here Brigitta has saturated the veil ply and outer carbon, and is now painting the foam and Graphlite parts in preparation for the inner ply. We included the Graphlite in this coupon so we could see what sort of surface disruption, if any, it causes in the finished part.

And here's the mold and test panel with peel, perf, and breather slathered on, zipped into a bag and sucked down.

And here's the exact same thing eighteen hours later. The perf dots are a bit bigger, but other than that it looks just like we left it.

One corner sliced open, with the breather peeled away. Looking good so far.

Completely unbagged, with just the peel ply left.

The envelope please...

Your intrepid sailplane developer, with a successful test panel!

You can't really tell from this photo, but the test panel shows good surface finish, only relatively tiny pinholes, and virtually no surface disruption from the Graphlite strips. On the part itself you can see where the Graphlite presses the weave of the cloth a tiny bit, but it is completely taken up by the veil cloth, and doesn't leave any detectable surface disruption.

Another shot of the exterior. The reflections from the overhead lights show the perfectly good but not perfect surface condition.

Back on the mold after weighing.

Homebuilt aviation is not for folks who don't try things at home.

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