Right Wing III

5/3/2006

Drilling the drag blocks

Drilling of the holes for drag and anti drag wires involved accuracy that I knew I couldn't achieve using a drill free-hand. So I built a jig. The plans are little gray when referring to these holes. So after a couple of web posts on the Biplane Hangar forum, I finally knew where I had to drill.

Basically the opposing holes in a block need to be above and below centerline, so as to avoid i)clashing in the block itself, and ii) clashing where the wires will cross in the middle of the bays.

However, reference the 1/4 wires in the first bay, the drag wire lugs fore and aft actually both line up center of the spars. This would mean that the wires would clash at the crossover point. So, I marked out on my bench in full scale, the rear view of the spars between rib 2 1/4 and 35 1/4. Then sketched the path of the 1/4 wires allowing 1/16 clearance in the middle of the bay where they cross over. I calculated that the above and below center line 1/4 holes on the fore and aft blocks at 35 1/4 needed to be 5/16 respectively....it seemed to work out just right.

I have ordered the drag wires from Steen. Apparently, they are the sole importers from Brunton's in Scotland - the only manufacturer in the world of these wires. Trouble is, I have to wait 8-10 weeks for them to come in...

Fitting the final ribs

Now that all drag wire holes were drilled, and ensuring that I have room to feed the wires through the wing, I glued in place all the other ribs. Before gluing in rib St. 2 1/4, I made sure that there was ample cut-out clearance in the spar apertures for the spar butt fittings and drag wire lugs.

I tried out a new tool from System 3. It is basically a double barreled caulking gun that accommodates T-88. The nozzle has a built in mixing labyrinth, so by the time the 2 glues reach the end of the nozzle, they are fully mixed - supposedly. While I was squeezing out some glue, I couldn't help but notice that the 'mixed' glue didn't look the same color as when I mix by hand? I t was still slightly opaque in color....suggesting that it was not quiet mixed fully. I squeezed some out on to a pallet and hand-mixed for a few moments, and sure enough, I got the color more 'solid looking' with mixing. Another issue was that like all caulking guns, after pressing the release trigger, you still get crap oozing out of the nozzle...usually dripping all over the floor. However, this isn't a dollar tube of caulk.

This darn thing cost me $56, and I think for the way it's meant to be used it's a piece of crap. However, I found a great use for it... I removed the mixing nozzle, and now I have a cool 50-50 equal T-88 dispenser! So I kinda like it after all. :-)

Aluminium trailing edge extrusions

I had purchased these from Steen Aero as a set. They came over-size in length for final cutting. To cut to length, I sandwiched the t' edge between 2 scrap pieces of 1/4 ply, then used the chop saw with a regular carbide blade. It is important to NOT cut the aluminium without the ply...otherwise the t' edge can, and infact will snatch on the blade, which can be a nasty experience.

The t' edge was then notched for the rib stations using aviation snips. While gluing the t' edge to the ribs, I noticed a slight bow down the t' edge line when eye balling...so I used cable ties to clamp a little extra pressure at the bow point - see pic. T-88 is not apparently ideal for alum', but it will hold well enough until the taught fabric is in place.

Almost Gotcha: Do not glue rib 2 1/4 in place until the spar butt hardware has been dry-fitted, and then the rib spar apertures cut around those fittings. In other words, mount the hardware, then whittle away at the ribs until they fit around the fittings, remove the fittings and glue the rib in place.

Almost Gotcha: Here's a tip from an A&P guy I know... I made sure that I had a big glob of T-88 on the ends of the ribs prior to attaching the t' edge: this is to help fill the void inside the t' edge where the rib tail tip butts up. Filling this void is important, otherwise when the fabric is attached, the tautness of the fabric could pull the t 'edges in a little, thus causing wrinkles. Amendment: add sawdust to the T-88 - provides good filling properties and prevents it from running...