Centerboard and handle

[Baysailer]

I started on a new centerboard, strip cut some douglas fir and epoxied them together so ready to make a blank and form. I careened and pulled the old board and it was actually better shape than expected, not bad for a 51 year old board. A bit chewed at the tip but the square peg wasn't to far gone so I think this could easily be repaired as well. One item though when you move it around it sounds like there's sand or something granular loose inside. Anyone now what this is about? There's no splits or breaks in the glass just some crazing and some chipped paint.

The handle is twisted, and always was since I owned it. It is delicate and you can feel the flex in it, just doesn't feel right. I always ensure there's no force when I move it. It is cast bronze. Is there any chance to straighten this or should I just go to DR and get a new handle? Or maybe fabricate a new one using stainless?

Fred B

[GreenLake]

Fred,

I would not bend a cast handle to straighten it, especially not one that is "delicate". You can still get replacements, people have been posting links to them here.

Don't worry about repairing your board. If you are up to the task of making a new one, go for it. The main benefit of making a new one is that you can get a better foil profile, which will make your CB more effective. This is not something that you can do with an existing board, at least not easily, as the profile is wider than what you need for about the rear third. It's difficult to be sure that you can safely remove the additional material without compromising the integrity -- because you don't know how it was put together.

That said, I did a minimal repair of my CB with just a bit of re-profiling (limited to what I could achieve w/o destroying the CB). In retrospect, I'm not sure whether that wasn't wasted effort. The effort of creating a correct profile from a new blank is effectively not much more, but the results should be better.

Whatever you do, make sure that you have a good square peg and matching hole. The holes can be reconditioned with shims. The peg is better replaced, I think.

One reason that I did not go the route of making a new CB even though I made a new rudder was that I didn't trust my skills at the time and didn't want to replace a part that is difficult to inspect. I made some mistakes when it came to building my rudder. They were easily spotted and even more easily fixed, but it helped that this is a part that I take a close look at every time I go out. I'd say, at this stage, I'd probably feel up to building my own CB.

[Baysailer]

Hi Greenlakes, My plan is to make a new board. I've made a few and well versed in it but don't get to hung up on the NACA forms. Basically I just put the widest point about 1/3 back and form what looks good to my eye and symmetrical for both sides. Maybe I'll put more effort into this but we'll see once I start the forming part. I made a couple of rudders a year or two ago, one pivoting and one fixed since I don't sail in shallows much. I was just curious on the sand or fiberglass granules inside but I looked at old posts and see the board is actually hollow.

For the handle I agree and seen everything I need on DR's site so I'll spring for one of those.

I probably won't do the through bolt for the pivot pin like you have on your DS since I don't see any real issues with it stock, especially if its a tight fit.

Fred

[GreenLake]

Your original post was not totally clear on your intentions. But it looks like you have things well in hand.

I've found it challenging to translate a theoretical curve onto the actual blade when I built my rudder. I did make a template by printing out the curve at full size, then gluing it to cereal box cardboard with epoxy. Unusual choice of glue, I admit, but it makes the cardboard into something that's easier to cut along the line, you can even sand it. It's using the template where I think I didn't quite figure out the optimal technique.

On my next attempt, whatever that will be, I'm planning this approach. Build an epoxy sealed blank with at least one layer of glass so that it is inside the dimensions for the template. Apply a layer of fairing compound with a notched spreader, notches running down the length. The idea is that the ridges end up proud of the final profile. Before that hardens, use the template and press it into the fairing compound to get lines that are at the level of the profile. Then sand the ridges until they are flush with these profile lines. Fill all remaining hollows (grooves). Sand flush. Seal with epoxy, paint and done.

I don't think it would be much more work than "eye-balling" a curve. Especially if the trick with the notched spreader results in being able to get to the final shape in fewer iterations.

However, I would love to know how sensitive the final performance is to getting the optimal curve. Do you lose most of the theoretical performance from the first few percent of deviation, or is it much more gradual? The latter would mean that your approach would already deliver most of the benefits. I don't think I've seen that discussed anywhere. But I suspect, it's not unlike sail trim, where even small corrections can have noticeable results.

I see the main benefit of the throughbolt in reduced flexing of the CB trunk. Instead of a sideways force on the wall of the trunk, the through-bolt delivers an up/down force inline with the wall. Which it is far more able to resist. K.C. ended up reinforcing his CB trunk wall, looking at mine I just don't see the movement. Anyway, the way I have it was the way I got the boat. I'm not sure I would have made the choice retrofit it myself.