Upper Rudder Plate Progress

More progress on the upper rudder control linkage deck. The upright mounting plate was cut from brass stock and soldered to the lower deck plate. The upper rudder fin indexing pin hole was used as the hole for the stainless hex head bolt.

From this angle you can see the access hole for the nyrod control link has not been drilled yet. I want to keep this opening to a minimum to reduce stress on the solder joints. Will probably put brass braces on either side of the hole to add support.

The rack and pinion resting in place. I'll need to finish a few more things before calculating the final length of rack needed. The square brass tube serves as a guide and support. With a little grinding and experimentation it should all fit. The new GRP upper rudder fin will fit down over everything and actually bolt onto the control linkage deck.
My benchtop 5" disc sander has been a life saver. It grinds down the soft brass easily.

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Rudder Mods - Part 1

In order to increase the room in the upper rudder fin for control linakges I've decided to use the cast resin piece to create a master for a new GRP (Glass Reinforced Plastic, or fiberglass) piece. To create an upper rudder master with more internal volume, the sides needed to be widened.

The first step was to mask off the area to be altered. Then a small piece of styrene was glued in position as a guide for both contour and to set the maximum height of the filler.

The masked area was then filled with a layer of Evercoat Metal Glaze. This automotive grade polyster filler dries quick and can be worked extremely well. I globbed it on with the stick then scraped it smooth to work it the proper height and shape.

The modified rudder fin in position for a check. The sides were widened 1/32" on either side in the center, then faired back towards the tail after the rudder hinge point. Red putty and sanding finished out the imperfections. All it needs now is a coat of primer, some rescribing in places and rivet replacement. The square access plate on either side for the rudder hinge will be masked off and simulated with a few applications of primer to build up the panel.
Here is some initial work done on the rudder linkage mechanism. The brass plate will mount to the hull below the hole drilled for a nyrod control line. A keyed shaft fits through it into the upper rudder to secure it to the plate. The gear at the top of the shaft will mesh with a rack (not pictured). The nyrod will link the rudder servo in the WTC to the rack transferring the servo motion to the gear. The hollow GRP upper rudder fin will mount down over this assembly.
More to come as time, and progress, permits.

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Seam Stealing

No pictures at present but I've been working on the seam between the upper hull hatch and the lower hull. It came fairly tight but there are the occasional gaps up to 1/16" in spots and I thought I'd try to hide them.

First, I made sure the upper hull hatch would not stick to the filler material. I did this by brushing on a layer of PVA which I use as a mold release agent when laying up Type XXI hulls. When this was dry, I also applied a thin film of bearing grease down the edge of the hatch. Just in case.

Then, I sanded the lower hull lip for good adhesion. 3M painters tape was masked around the external edges to keep from spoiling the rivet detail. I also put the tape along the edge of the upper hull hatch as well.

The filler of choice was Evercoat Metal Glaze. I mixed a small amount up on a plastic putty spatula and applied it sparingly to the lower hull lip with a popsicle stick. No need to glob on too much and watch it ooze down the side (this stuff isn't cheap). The upper hull hatch is then installed and securely fastened. Only small sections (4" - 6") on one side are filled at a time to ease separation once the Evercoat cures. Any excess filler is scraped off to leave a smooth seam.

After an hour or so, the upper hull hatch is unfastened and gently pried loose -- snap! The result is a nearly invisible separation line between the two hull halves.

NOTE: for those who've lost any of your tiny button head socket cap screws used to secure the upper hull hatch the size is #2-56 and the length is 1/4". A pack of 50 in stainless steel can be bought from Micro Fasteners for $5.50. I'm switching out the kit supplied alloy steel screws to prevent rust in the field.

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