Rudders

After cleaning up the aka supports and the rudder support on the hull, it was time to continue fabricating the rudders.

Taking the Moto-tool with its sanding drum at the end of the flexible shaft, I trimmed the leading edge of the two rudders at the joint where the reinforcement piece of plywood joins the wider rudder blade. This is where the rudder will be mounted on the outer fiberglass tube which, in turn, rotates about the smaller fiberglass tube previously glued and glassed to the hull.




Using a left over piece of smaller tubing inserted into the two rudder outer tubes in order to keep the rudders concentric, I then carefully balanced the two rudders at 55 degrees plus and minus, mirroring each other, using blocks of scrap foam and some weights to keep things aligned properly. Using several spoonfuls of fillet foam the rudders were then secured to the larger fiberglass tubes. They were left to set overnight.

The next day the rudder assemblies were separated and the fillet material was trimmed and smoothed. The glass and resin that had been applied to the seat, to the aka supports and the rudder supports was also sanded smooth.

The rudders were then mounted on the support shaft, with temporary supports used to hold them parallel to the deck.

After a bit of experimentation I took some scrap plywood that originally had been intended for the aka support bases and trimmed off the beveled edges. These pieces were then placed on the rudders at the pivot points and held in place at the top end with a support structure made from junk found laying about the shop. The angles for the pieces was chosen so they would just intersect with the side of the hull when the rudders were in the fully deployed position. This would align them with the pulleys that would be installed for the control cords that would be used to pull the rudders down into position.

Since there was not much room on the inside between the outer rudder tube and the limit ring, I taped them off with shrink wrap plastic on the top and duct tape on the bottom to hold the shrink wrap in place.



More fillet putty was mixed and liberally applied to the joint on both sides.

The assembly was left to set overnight.

I also started an experiment. Using a large piece of scrap wood, one of the smaller T-nuts and some of the excess fillet putty, I secured the T-nut to the wood and let that sit overnight as well. Tomorrow (2 days later) I'll see how much force is needed to
1. torque it so that the nut spins in place when a bolt threaded into it is rotated.
2. remove it when a tension force is applied to a bolt threaded into it.

Otherwise, today I went on a shopping trip to Online Metals. No, I didn't digitize myself and jump into the computer like the guy in Tron; rather, I drove over to their bricks and mortar location in Ballard, a neighborhood in northwest Seattle.

Their warehouse is located quite close to the Ship Canal leading from Lake Union to Shilshole Bay on Puget Sound. Anyway, I picked up two contenders for the stiff tubing portion of the propeller shaft that connects to the gearbox and fits through the stuffing box to where the more flexible rod portion of the shaft continues onward.

One tube is 0.625 inches OD by 8 feet, with a 0.035 inch wall. The other is 0.5 inches OD by 8 feet, with a 0.049 inch wall. I think the 0.625 inch tubing will do quite nicely, and perhaps might be a bit thicker than needed.

While I was there I also picked up a 1 foot tube of stainless steel to be cut and worked into a coupling between the gearbox and the prop shaft tube.


On the way back home I stopped at Fisheries Supply and picked up some 3mm polyester cord (rated to over 460 pounds) and a pair of cheeks; i.e., pulleys mounted in a stainless steel cage that will be screwed to the hull. These are to be used to pull the rudders down into position and redirect the tensile force of the rope forward to the cockpit.

Since the hull is only 4mm thick, and the forces will be repetitive and possibly somewhat larger than that thickness of wood can handle, I think I'll thicken the hull where the pulleys are mounted with an additional layer of plywood, say 1 inch by 2 inches or so. That should probably be adequate, along with a pair of 1/2 inch #8 wood screws.

It is starting to look like the boat just might not be finished in time for the race this weekend. That might be just as well, as the following race is in a month and I would then have time to do a decent finishing job on the hull, clear coat it, and put it through some trial runs.