The craziness continues!
My continuing flirtation with Aviation:
I've purchased a 90% complete Mitchell U-2 Flying Wing!
(Which in Aviation math usually means, 90% is left to be done.)
Rerouting the Rudder Cables
The plans call for the rudder cables to be routed through the wing in tubing. The original builder apparently used a low density Poly Ethylene tubing of some nature. Ultra violet light and age had rendered much of it so brittle that it was easily cracked or broken. Also there were places where the tubing was turned in radiuses that were smaller than allowed for the cable they carried. And finally, the tubing protruded out of the wing at an upward angle potentially allowing water to enter the tubing.
So I decided to reroute the cables using a different tubing and to make all major direction changes using reinforced phenolic pulleys. I'll use 1/4 inch ID Pax tubing.
|First we used the 2" pulleys (the minimum dia. allowed for the cable) as a guide for cutting out the pulley block sides. Then we epoxied the sides to a spacer which was the width of the pulley plus two washers.|
|The roughed out pulley blocks before being separated and sanded down to final shape. At this point the block assembly is very fragile - sure enough immediately after being separated one unit got dropped and broke the spacer - which was easy enough to fix.|
|After sanding down the attachment area on the spar, I epoxied one of the pulley blocks in place and "clamped" it with a bungee cord.|
|The other pulley block after removing it's bungee cord the following day.|
|Next I attached an old cable to the rudder control arm and routed it through the two pulley assemblies and existing holes in the rib and spar. Then I clamped the cable so the rudder spring put tension on the cable.|
|This is the other pulley assembly being fitted and aligned prior to being epoxied into place.|
|After alignment the pulley block was epoxied in place and the tension increased on the cable to "clamp" the assembly in place while curing.|
|Next we cut supports which were mounted to each rib to support the tubing and it's support.|
|The tubing support was secured to the supports at each rib using nylon wire ties while the tubing was secured to the tubing support using smaller exterior grade wire supports.|
|The tubes needed to be spliced in order to have enough length. So we split a piece of larger diameter tubing and then secured both ends with wire ties. The butt ends of the tubing were tapered with a drill bit to aid threading the cable through the spliced area.|
|Checking the alignment of the cable tube with the first pulley assembly.|
|Overview of the first outer section after completion.|
|And finally, we fitted a cutout in the wingtip faring for the pulley block. Next I need to make a small fairing to cover the pulley block and streamline everything before painting.|