Disadvantage to good speed?

[Stickinthemud57]

On a recent shake-down outing, I was trying experiment with centerboard angle settings and found to my surprise that the centerboard was actually rising up above the "normal" angle without my having pulled on the lifting rope. It was slack at the mark I made on the rope at the normal backrake setting, and did not settle down until I was sailing at a lower speed.

Another member at the forum was boasting some pretty good pointing angles with his 26D, so I thought I would see how things went with the centerboard straight down. Problem is, the faster I go, the more it lifts. I did not scrape off the algae at my most recent bottom cleaning. That can only be done in the water, so there is likely a little algae growth contributing to drag and resulting lift.

Are there any other 26S owners who have experienced this. Are there any who care?

I am trying to think of a way to overcome this, and the only thing I can come up with is a thinner centerboard (maybe made from steel plate?) that would be of similar weight, but presents less drag.

Any thoughts?

[LakeMac26C]

A downhaul would be the way to go. It's silly that the rudders have a down and uphaul, but not on the CB? Another way to do it is with a locking pin to hold the CB at a set angle. Again, the rudder has these "Shear pin holes" but the CB does not??

Yes, you could be talking about putting holes in bad places on your boat if you try to retrofit something, but from a factory design perspective, it doesn't make sense not to have a downhaul for the CB.

I've also heard of ppl weighting their CB for better stability and also to help keep it down. I don't know if the stock hinge pin is up to the task though.

Or maybe some kind of small strake could be attached to the side of the CB to act as a tiny hydrofoil to keep the CB down??

I've been meaning to put my waterproof camera out on a stupid stick to actually look at the CB angle while underway, but never remember to bring it. Uphaul rope tension means nothing if the CB is angled back...your "neutral" uphaul tension is always in relation to the angle of the CB.

Besides, even the uphaul on my boat prevents me from retracting it 100%. Dunno why. I haul it up, hear the tell-tale sound of the board slapping the CB trunk, but when I go under to check it, I can still see some CB sticking down below the hull and can easily raise it a couple inches by hand.

[Stickinthemud57]

Yes, the CB does stick out some even hauled all the way up. Otherwise the bot would not have sailed all those times I forgot to put it back down!

I'm trying to imagine how a downhaul would work on the centerboard. It seems to me it would require a through-hull and tube arrangement like the uphaul. That and a quick-release clamcleat like I have for the rudder downhaul on my tiller. Not ready to go to that extent just yet.

I have had others suggest adding weight to the CB. This would likely be the most simple and direct solution, but also means you will be fighting that weight when raising it. Not ideal. The idea of the strake makes sense, but would interfere with raising the CB when racing and trailering. Also, more drag.

Using the diagram for the 26S at Sailboatdata.com et. al., I determined the "correct" angle and experimented with my uphaul until it matched. It took several trips underwater with my coroplast angle template, and once there I marked the position on the uphaul rope where it exits the cabinet at the galley. By doing that I can tell when it lifts above that point by finding the uphaul rope slack.

My plans for the off-season include applying Petit's Black Widow bottom paint to the bottom and the CB. Hopefully that and keeping the algae scraped off the CB as well as the bottom will do the trick.

[LakeMac26C]

I've had other centerboard boats other than the Mac that had downhauls built in. I don't know why it's not a standard feature on boats with CBs, even if it was only an elastic or a breakaway rope. But yes, they would need to plumb another thru hole for the downhaul. There are some pulley systems designed to lead a rope back to the same tube as the uphaul. Not sure specifically how to do this on a Mac. I've even considered some kind of magnet system for holding the CB forward since gravity is doing almost all of the work.

I guess this is where a daggerboard like on the Ms and Xs is an advantage because you can be assured at what depth the daggerboard is at. But you also have little means of adjusting the CLR with a daggerboard.

When you say you calculated the "correct" CB angle, what did you mean? For performance, moving the CB forward or back changes the Center of Lateral Resistance which can benefit the boat at different angles to the wind.

You could also try shaving the rear of the CB down to a finer, symmetrical edge and reglassing it. That should allow it to cut through the water with less drag which might help with all around performance. But if you get the curve wrong then you could also screw up the performance.