Centerboard "Play"

[Rick Thompson]

How much "play" should there be in the centerboard when it is lowered?

This afternoon we were out and were becalmed in some relatvely choppy water. We were only rolling maybe 10-15 degree but the centerboard was banging back and forth in time, pretty loudly. I thought there was something wrong and lifted it up and then we motored in (no wind anyway.)

I put the boat up on a boat lift and went underneath, and could move the CB almost an inch back and forth. I pulled the center pin to see if anything was really loose (and picked up the CB from the bottom of the lake.)

The pin is fairly tight through the centerboard (no signficant rounding of the corners), and the end of the pin seems to sit fairly tight in the indent on the other side. When we were out, the screws were tight, as I had earlier had issues with the CB raising.

The rubber gasket feels almost new, neither frayed nor rigid. Any advice or feedback would be greatly appreciated. My "first mate" is beginning to question the sea worthyness of our new old daysailor.

Also, any tips on aligning the CB when I reinstall it would be appreciated.

And finally, am I correct in believing that there are no washers or other spacers that go outside of the CB but in the CB tunnel?

Thanks,

Rick

[K.C. Walker]

What is normal or common it is not necessarily optimal. Ideally, there should be no play when the board is down. My 1974 boat has approximately half-inch difference between the centerboard and the trunk. The previous owner fiberglassed on some shims both in the trunk and on the board to eliminate wobble. I've read somewhere on the site that some people use formica as shim stock. It is glued onto the board to eliminate the wobble, which seems like it should work well. For best results you would want to get a snug fit at the top end of the board and where the board exits the centerboard slot. The very best solution would be to have a new foil shaped centerboard made that fits the trunk.

KC

[persephone]

Hi Rick,
A question first. Is your boat a one or two?
I had a similar problem with my boat (a one). I had play in 3 axis (fore & aft, side to side at the tip, and yaw or twist). A lot of it was between the worn post on my handle and the square boss in the board. Additionally the board handle and trunk wall all moved to allow the tip of the handle to move out of the (too small) indent in the far wall. I don't think the indent in the far wall is enough to keep the board from moving. The walls are too flexible. I replaced all the parts with custom made stuff (I have a friend who is a machinist). My board is now snugly through-bolted from one side of the trunk to the other. Additionally I have two 7" delrin discs (one on each side) spacing the board from the trunk walls. The end result is the board does not move at all except for up and down like its supposed to. The downside to these mods is that the stress is transferred to the trunk walls (a weak spot) and this caused the wall to crack open under the handle in the high (for a daysailer) seas off Chatham during the NACRs this year. If you don't race and don't plan to you might have more options.
The simple fix would be to add some shims to the side of the board, then drill and tap the handle for a relatively small screw (maybe a 1/4-20, smaller if you sail in calm waters). Drilling the hole through the far wall is the tricky part. But with some ingenuity you can devise a centering plug (for the drill) through the hole the handle sits in to make sure the hole is aligned properly.