Installing the Cape Horn Windvane
When I was ready, I started off by marking the center of the transom, vertically and horizontally, with a pencil mark. Then I drilled a small 1/4" pilot hole. I taped over the surrounding area to protect the edges and reduce the likelihood of damage to the Awlgrip paint when I drilled the required 2 1/2" hole with a hole saw. I would be lying if I said I was not a little anxious about drilling this hole. I spent some time making sure the drill bit was level by calibrating the drill with a bronze rod and a torpedo level. Once I was satisfied I knew what level was I installed the hole saw and made the cut. No sweat. The tube fit perfectly level.
Next, I inserted the horizontal mounting tube (HMT). It gets bolted in place with two 1" diameter SS support rods. The rods connect to the HMT on the inside of the lazerette and then to 4"x4"x3/4" beveled plywood pads that are glassed to the inside of boat. Then, to provide more strength, the HMT itself gets glassed to the inside of the transom as well. So, it is important to get the depth of the HMT just right as it become permanent to the boat. To determine the depth, I used a 1/4" line to hold the HMT level (see pictures below) and temporarily installed the control axis (lower part of the vane) which contains the toggle rod and to which the steering oar is also attached. The control axis is inserted through the HMT. The steering quadrant is attached to the forward end of the control axis that protrudes through the forward end of the HMT--a tube inside a tube, if you will. I wanted the vane tower be close to the aft end of the fantail but allow room for the steering oar to rotate up 180 degrees in the stowed position. I also checked that the quadrant, which gets attached to the end of the control axis on the inside of the lazerette, to make sure it will have room to rotate. The quadrant will be in the up position (see the photo below) when the steering oar is down but rotates 180 down when the steering oar is in the stowed, up position. Clear as mud, right? When I get further along and have more pictures it will make more sense.
Once I was satisfied the HMT was in the right position, I marked the tube on the inside with a sharpie. Then, I spent some time cutting the plywood pads that the inside support rods will be secured to. The brackets the tube get bolted two have to be through-bolted to the pads and the flat heads of the machine bolts counter sunk since that side will be glassed to the inside of the hull. I spent about 90 minutes just sitting in the lazerette with the pads, brackets, and some mock up 1" OD PVC pipe determining the best location for the support tubes to be located. I initially thought there would be lots of options regarding where the pads could be glassed to, but not so. The ideal location would have been under the aft deck but the dorades are there. A little closer to the centerline looked great but the lazerette hatch hinges fit there. A little wider and the antenna tuner would be in the way. Finally, I came up with a good location . . . angled down and to the lower side of the transom just aft of the quadrant. By the time I came up with the right location it was time to stop work.
Next, I made a simple jig for holding round stock when drilling. I took a scrap piece of 2x4 about 14" long and cut 2 opposing 45 degree bevels in it with the bevels joining down the centerline. This created a 1" deep 90 degree angled "trough" that will hold various sized round stock steady for drilling.
Then, I used the measurements for the support tubes from the mock ups I made yesterday. I cut the 7/8" OD SS tubes about 5" long with a hack saw. I used a sharpie to mark on the HMT where the swivel brackets would be located (each swivel is held on with two 1/4" bolts. These holes only go through one side of the tube. Cape Horn supplies a little custom curved and pre-tapped backing plate that fits on the inside of the HMT. I marked the location on the HMT for the two holes for each of the swivel brackets with a center punch. I could not get the jig to fit under my small drill press and have room for the drill bit to clear the 2 1/2" diameter HMT. So, I just set the jig on the floor and cut the 5/16" holes with a hand drill (these holes are cut slightly oversized to provide some wiggle room for fitting) . The jig made it pretty easy. Next, I needed to drill a 1/4" hole for the bolt that would hold one end of the tube to the "U" bracket (I installed the "U" brackets to 4'x4" plywood pads yesterday--see the previous entry for pictures of the pads and "U" brackets). This hole goes all the way through the tube so I used the drill press for the small tube, since it would fit under the drill press, and because this hole needed to be drilled at 90 degrees through both sides. Next, I assembled all the parts and test fit them in the boat. It all looked pretty good. I was running out of time and did not want to get in a hurry epoxying the HMT and the pads in position so I spent the remaining time cutting out biaxial cloth for the pads and a small strip for the HMT. I also spent some time beveling the inside and outside edge of the 2 1/2" hole in the transom. This should allow a better epoxy filet on the inside and a bedding compound caulking grove on the outside. I vigorously sanded the inside of the lazerette where the pads will be secured with 40 grit paper, vacuumed up the residue, and did a thorough acetone wipe down.
So how does the windvane work? The windvane blade is set by the skipper so one edge is directly into the winds. The vane is push over (tilted) left or right as it responds to changes in the relative angle of the wind as the boat sails along. The vane blade is linked to the steering oar via a special connecting rod. A change in the windvane causes the steering oar to turn (left or right) and the water pressure then pushes on the steering oar (with great power) literally swinging the whole oar blade. The swinging of the steering oar (levering is probably a better word) causes the control axis to rotate inside the HMT, riding on those Teflon bushings. That rotation of the control axis is transmitted to the quadrant (bolted to the forward end of the control axis) you can see in the last picture. As the quadrant rotates it pulls on the control lines (they are not rigged in the photo below) that lead, via a series of small blocks, to either the tiller, wheel, or the boat's steering quadrant (if it has one) (three options) as you desire. It's all about the Cape Horn quadrant pulling on the control lines. That is essentially how the vane steers the boat.
Last, night I sanded the HMT on the outside in the area that will be glassed to the inside of the hole in the transom. Sanding the SS tube gives the epoxy something to grab onto so it won't slip. I also sanded the bottom of the plywood pads and the beveled sides with 40 grit abrasive paper. This morning, I started off by test fitting the whole lash up one more time. Next, I performed another acetone wash down of the area that will receive epoxy. Next, I cut some 17.08 biaxial to fit over the plywood pads that will be glassed to the inside of the lazerette. Then, I wetted out the bottoms of the pads and the area against the hull they will contact with. I let it cure till it was tacky. Next, I mixed up a batch of West Epoxy that I thickened with a small amount of 404 filler and the rest was 406 colloidal silica. I trowled it on to the bottom of the pad to create a small wedge to better angle the bad towards the HMT. I smoothed fillets around the pads and too the left over epoxy to make a fillet around the HMT on the inside of the hull where it passes through the transom.
I let all this cure till it was firm but not hard. Then, I removed the bolts from the pad end of the support tube and folded the tubes out of the way. Next, I wet out the biaxial, placed it over the pads, around the HMT, and smoothed it all out. I spent the rest of the afternoon reading through the directions for mounting the control tower and rigging the control lines.
The most interesting event today was installing the brackets on the tower. The trick was to get the tapped backing plates inside the tube, lined up with the holes I drilled, and the bolts on the fittings to connect with the threaded backing plate. Yves Gelinas, the designer and builder of the Cape Horn Windvane described how to do it in the instruction book. I was a little skeptical but it worked like a champ. Take a look at the pictures to see the technique. I will keep that technique in my bag of tricks.
The windvane is up. It looks good. Seems to be very secure. It is nice to see the boat looking different. Tomorrow, I start working on rigging the control lines. I'll need to pick up some small bullet blocks, make some backing pads and take a closer look how/where to run the lines.
I'll replace the night time photos of the vane in the gallery below tomorrow with some day time shots.
Note: I mentioned that I think Yves is very clever. In one of the pictures of the Cape Horn steering quadrant I added to the 7 Dec 11 photo gallery, there is a little rod you can see that fits in a special slot in the front of the HMT. It's only purpose is to allow a very small tiller pilot to link to the steering gear. This unique design feature allows what would normally be a low power (and low power draw) tiller pilot to steer a large boat because the tiller pilot taps into the self steering gear mechanical system to provide leverage via the steering oar. Yves points out that because the tiller pilot does not have to work very hard and because it will be in the lazerette and out of the weather it will last longer. The rod can be removed in a couple of seconds.
I found the blocks I needed--Harken #001 swivel bullet blocks with a 2 .25 diameter sheave. As hard as it is to believe, of all the places I looked, the best price, by far, is West Marine. They gave me a bunch of discounts. They had two in stock so I purchased them and ordered the rest. I chose bullet blocks because they have very little friction which will help to keep the vane sensitive in light air.
On the right side of the picture you can see the temporary piece of scrap pine 2x4, installed vertically, secured with hot glue and the Schaefer blocks that I used to develop the run. I have not drilled a hole in the center of the bronze plate as I need to get the right fitting--a SS eyebolt I think. Two block will be secured to it--one that supports the port side control line and one that support the starboard side control line. I can't really do much more till the rest of the blocks arrive. So, tomorrow I'll go back to work on the interior.
Will it be sensitive enough to steer the boat in light air when rigged in this manner? Yves seems to think so and that was good enough for me to give it a try. If, however, it is not then I can modify it easily enough and connect it to the tiller.