Building a rudder

[GreenLake]

I recently had a mishap where the boat slipped off the trailer and was supported only by the rudder while being dragged a short distance. Because of the location of the rudder pivot, the transom never touched the ground, but I lost about 1/2-3/4" off the leading edge of the rudder. After drying out the exposed wood, I used penetrating epoxy (SystemThree S-1) to give a good seal and then used 3M High Strength Marine Repair Filler to build up the leading edge again. (It's fiber reinforced and works well for that purpose).

I located my original templates and made sure that the profile was as close as I could make it before painting.

Good as new. Gudgeons and pintles look fine.

[GreenLake]

More follow-up on how durable or not the rudder turns out to be in practice. (Pictures to come).

Latest data item: collision with a keelboat. They failed to duck me and hit the stern quarter of the DS. Other than some lighter spots on the rub-rail, no visible evidence of the collision --- except for the rudder.

The rudder didn't like the sudden sideways motion through the water, and the cheeks of the rudder head proved to be the sacrificial part. It wasn't a clean break. On the side towards the impact, the plywood for the cheeks failed and it delaminated, but there was enough there, or in the thin glass sheath to prevent the rudder head from separating.

The opposite side, away from the collision, broke cleanly in a pretty straight line. Wood and glass.

The rudder blade looks undamaged, and no damage to the pintles or gudgeons.

I'm not sure what to think. If allowing the rudder to break, allowed the stern to accelerate faster and thus take no damage, that would be a plus. On the other hand. if the rudder head can break before the gudgeons are bent, even a little, it might indicate that it broke a bit too easy.

Tentative plan is to switch all or part of the "cheeks" to fiberglass this round. But it won't be a controlled experiment, as I'm not planning on being rammed again>

(PS: looks like one of the POs also had a collision. There are faint weathered cracks on the deck on that side, but none on the opposite one.)

[GreenLake]

As promised:

Rudder damage; click on image to view all

P1100496-c2_1099.jpg (54.27 KiB) Viewed 876 times

This photo clearly shows how the boat was shoved from port side and the water kept the rudder in place. The other boat never touched the rudder itself. One of the two cheeks that hold the rudder blade simply tore clean across under tension. The other delaminated inside the plywood.

After taking it apart and looking at the wood, it appeared discolored, so it looks like water had gotten in at one point. Both the outside painted surface, as well as the inside were covered with a glass sheath. Except at the break itself, these surfaces are undamaged, unlike the interior of the plywood.

Because both rudder head and blade are undamaged, my plan will be to replace the cheeks (and beef them up a bit in the process). Anybody interested in using the information here to build their own rudder might want to take similar steps for a somewhat stronger design.

Note that the original design of the rudder did survive over a decade of use, something that hopefully means the repaired one will last even longer.

More details to follow.

[GreenLake]

Here now the update after successful rudder repair.

As you can see above, the damage was limited to the two "cheeks" that attach to the rudder head and between which the rudder blade can pivot. That determined the strategy for repair.

1. I started with removing almost all of the cheeks, and sanding the bottom half of the rudder head back to its original thickness.
2. At the top of the cheeks there's that little "ramp" area, designed to give a more gradual transition in thickness. You can see that one side had split almost all the way to that location, while the other one broke much lower. I removed both to about the same level, but I left the ramp itself in place. Not least to have a fixed point for alignment.
3. I took a piece of plywood, double the size of one of the cheeks and added several layers of fiberglass cloth (both light and heavy) as well as fiberglass mat (designed for use with epoxy resin). The original design had some fiberglass layers on both sides of the plywood, but think I more than doubled them, with an extra layer or two on the outside.
4. Once that was done, I divided the board, and trimmed one edge for alignment with the ridge left over from the ramp.
5. I then screwed both sections into the rudder head with deck screws, just to fixate them while trimming the rear and bottom, which form a somewhat complex curve. I found that a jigsaw barely works, and that the best result for rough shaping was achieved on a table saw (carbide blade and blocking the free ends of the checks to prevent them from bending while cutting.
6. Final shaping with a belt sander. I decided to leave a bit more material than the 1" in my original design. The damage didn't show any weaknesses in that area, but I felt better adding about 1/4-1/2"....
7. Locating the hole for the pivot was tricky. Originally, I had drilled blade and cheeks at the same time, which minimized issues of positioning. This time, I had to try to locate the hole based on a part that didn't really have too many straight sides (and even the nominally straight ones weren't really). However, I managed that to within about 1/8" of an inch. The rudder blade now overextends a bit beyond the vertical, consistent with the gap being too tall by a bit.
8. The original design had a cutout where the bracket for the lower pintle is attached to the rudder head. That design was copied from the stock rudder, but proved to be a weak point (the fracture lines tended to end there). I decided to not do a cutout, but to only drill oversized holes that would allow the heads and nuts for the bolts to pass through and on one side, wide enough to fit a socket for tightening. The brackets for the pintles effectively go into a "slot". However, it did require sanding the underside of the cheeks, so there's now a "channel" where there used to be a full cutout. An electric file proved the tool of choice for that part.
9. Even though some material was removed from the underside of the cheeks, the heavier laminate on the outside is almost fully undisturbed (except for the access holes for the bolts) and the brackets now go into a slit.
10. After shaping an drilling, I unscrewed the checks, coated them with epoxy and reattached them again in the same place (with the heads of the temporary screws deeply countersunk).
11. I also used some clamps.
12. The full "ramps" where rebuilt with a wood flour/epoxy paste, and the same pasted used to bury the temporary screws. Any bare wood from sanding and drilling was epoxy coated.
13. After sanding the wood flour paste, some areas could use cosmetic fairing, for which I used QuickFair.
14. I also took care of some nicks in the trailing edge of the blade, using an epoxy repair paste (a MarineTex clone).
15. To provide UV protection for the epoxy, I applied a coat of Pettit's EZ-Poxy.

I've sailed with this a couple of times and the repair appears fully successful. Not a full stress test, but I'm expecting this to work at least as well as the original design.
Pictures to come.