HP-24 Project

Update 9 April 2003: A little jig, the first big layup

This weekend I made the jigs for the HP-24 rudder pedal slide carriage. That's the unit that the two rudder pedals pivots on, and which slides fore and aft for adjustment.

I'm using HP-18 rudder pedals, but for the slide carriage I've decided to go with a new design that slides on a single square steel tube instead of two round tubes. It's similar to one I saw on a Genesis II a while back. I don't know if it's better or worse than the HP-18 system, but I do know that what I'm doing will have fewer parts and be a bit easier to install.

One interesting aspect of my rudder pedals, and of the adjustable rudder pedals of virtually every European sailplane, is what to do with the extra cable from the adjust knob.

When you want the pedals further aft, you pull on the adjust knob until all the slack comes out of the cable. Then you pull a bit harder to unlatch the carriage. Then you contiune pulling to tow the carriage aft to the desired position. Then you apply forward pressure to the carriage with the heels of your feet until the latch mechanism engages the next forward latch detent. Then, you release the adjust knob, and a light spring takes up the extra slack in the cable.

Or, maybe not. On a stock HP-18, the rudder pedal adjust is a rigid cable that stays at the adjusted position. On some European ships, the slack is taken up by a light bungee cord that rots to pieces in the course of about five years.

Somehow, I've got it in my head that I might be able to use a take-up reel somewhere in the system to store the extra cable. The places that appeal are on the slide carriage, and in the actual adjustment knob that you grasp to adjust the pedals. I'm thinking that I might be able to use one of those take-up reels that some people hang their keychains from to store the extra cable. That might be kinda slick. It also might be sorta hokey. We'll see.

This morning (9 April 2003) I did the first big composite layup for the HP-24 horizontal stabiliser plug; it was the top surface. And anyhow, I didn't do it alone; longtime friend Doug Gray (DG-300 DV) helped out.

I did the layup (3 ply of 7533, 1 ply of 108 veil cloth) on a piece of visqueen, and then laid the whole mess onto the foam core and peeled off the visqueen. After sweeping it down to the core with squeegees, we laid on peel ply and breather, and then vacuumed it down to about 8.5 inches of mercury.

The whole layup took just under three hours going slowly and methodically. There was about an hour of setup, just over an hour speading resin and laying on cloth, and about 40 minutes getting the laup and core zipped up and sucked down.

Tomorrow morning at about 7:30 AM, I'll unveil it and see what I've got.

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page updated 9 April 2003 all text and graphics copyright (c) 2003 HP Aircraft, LLC