Centerboard Mechanics and Physics

[christophermoorkelly]

I'm getting a new CB fabricated for a 17' sailboat, so wanted to be sure I understood how it works first. The current CB is in the image. The bow would be to the left. If you look on the lower right corner, it has a pull handle for lifting, with several holes for a cotter pin, which rests atop the trunk and across the slot. My question is... how does it 'stay down' when under sail? I've only ever sailed daggerboard and keel boats. Is it just the weight that will keep it from riding up into the trunk, or just generally being loose? There is no 'pull it down' mechanism.

Thank you!

 

[Timm R Oday25]

If I'm to understand the picture correctly ,the left side is the forward edge . There "appear" to be a fair number of rust spots. If this is indeed the
case then the center board is steel . That weight alone may well be enough to keep it down . My centerboard is about fifty or sixty pounds and stays down just fine . The holes may be for holding it up for shallow water or trailering .

 

[shemandr]

Weight alone, I think. I'm seeing rust so I'm assuming it metallic and therefore has enough weight to stay down.

 

[shemandr]

What about the rudder? It's likely set up to kick up in one method or another. On both of my centerboard boats the rudder needed a mechanism to keep it down - they were made of wood. The system should have some give in it so that if you ground the rudder it will move up rather than be damaged.

 

[JBP-PA]

Even a fiberglass center board will stay down from weight alone. There isn't much force pushing it backwards until you hit bottom, where you want it to lift up.

 

[christophermoorkelly]

Ok great, thank you all. Yes, it's steel and will be replaced with the same.

 

[Crazy Dave Condon]

What is the manufacturer of the boat and model. Where will you be sailing?

 

[christophermoorkelly]

Restoration project. Not sure exactly what she is. Definitely a kit build in the same family as a Lightning, Pirate, or Comet, but with slightly different dimensions. And a Hampton One rig. We'll be on the lakes, inlets, and bays of the general Chesapeake area.

 

[Project_Mayhem]

What's wrong with your current centerboard? Why replace it?

 

[christophermoorkelly]

Warped, pitted, and the various holes are rusted wide open. The other stuff could be fixable with a sandblaster and the epoxy coat, but the whole thing has a warp to it. Anyway, I have a shop working on a new one, which is exciting.

 

[BarryL]

Hello,

Back in the day I had a Catalina 22 with a swing keel. After you lowered the keel there was a screw you could tighten that could keep the keel from moving up. Since the keel was iron and heavy I never bothered tightening the screw.

Anyway it would be pretty easy for you rig up something like that if you find the centerboard does rise up.

Good luck,
Barry

 

[stickinthemud57]

I had a Hunter 170 that recommended the use of a bungee cord to make sure it stayed down. I opted instead to use a rope and quick-release clam cleat.

With my MacGregor 26S I noticed the centerboard would ride up when I got upwards of 6.5 knots. I attributed it to drag from algae on the centerboard. One of my winter projects included filling, sanding, and refinishing the centerboard to assure minimum drag. Beyond that, I'll just have to take a swim with a plastic scraper from time to time to ensure it stays clean.

 

[jssailem]

rope and quick-release clam cleat.