Centerboard riggin

Engines, Drive trains, Propellers, Steering, Ground Tackle and other mechanical system

Centerboard riggin

Postby Erik » Sat May 12, 2018 6:42 pm

I have recently replaced the centerboard lift line and blocks and noted that there is no mechanical stop to prevent lowering the board to far. I did this repair with the boat was on the hared and was able to drop the board a full 4' to paint it. I have marked the lift line at 1' intervals I now know how far its extended. Is something missing or is this they way it was intended to function.

Thanks for your help

Erik
Cat Ketch 33 hull # 74
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Re: Centerboard riggin

Postby Castaway » Sat May 12, 2018 7:39 pm

There should be a line from the block attachment on the aft end of the board, and (on Castaway), a "U" bolt at the top of the fork which carries the pivot. You can adjust the length of this to limit the lower travel of the board. I think the optimum point for lowering the board is when it most nearly fills the opening at the bottom of the case, which supports the board laterally along its length, and allows less room for it to bang about. However, if it extends further, then it will increase lateral resistance, as well as moving the centre of resistance forward. Getting the length of the rope right is quite tricky, in my experience, and I mark the pennant at suitable points.

The stop rope is 10mm, three strand nylon, with spliced loops, which will hopefully stretch a little if the board drops suddenly.

The rubbing pegs will also limit the travel, though if they are too large, the board may jam when lowered. I had new ones made, and had to trim them after trial fitting. Getting them out was a long job. There is a hole in the centreboard at the aft end, which I think is there for lifting the board at installation, but that might be a suitable attachment for a stop line, too. I think a stout bar at the after end of the casing top would be a good fixed point for such a line, with less strain when the board is fully down.

Regards,

Gerald
Gerald Freshwater,
s/y 'Castaway', (UK F35 cat ketch)
Lerwick Boating Club
Shetland Isles, Scotland
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Re: Centerboard riggin

Postby andygc » Sun May 13, 2018 6:54 am

It seems that the F28/30 is slightly different from the F33/35 - but maybe that varies from boat to boat.

My plate has a double eye - one hole for the lifting pennant, one for the restraint strop.

Plate00001.jpg
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The hole on the left (aft) is for the restraint strop.

The other end of the strop goes to an eyeplate on the port side of the trunk.

Plate00002.jpg
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My strop is a length of 14mm braid on braid (came with the boat). It has a simple stopper knot each end, and is just slightly slack when the plate is fully up. It stops the plate when the leading edge is at 45 degrees to vertical - which is the position shown on all drawings I have seen of centreboard F28 and F33 cat ketches.
Feronia
(UK Freedom 30 cat ketch, build number 107)
River Exe, Devon
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Re: Centerboard riggin

Postby Castaway » Sun May 13, 2018 8:01 am

CB (aper) 5.jpg
CB (aper) 5.jpg (233.88 KiB) Viewed 263 times

Here's a picture of the two attachment points, though the line is detached from the yoke, and is lying over to the port side. The centreboard has been partly raised into the saloon. A knotted line would be much easier to adjust, but I have never had the chance to work on the board with the boat raised to any useful height.

I'm sure Jay Parrish's aerofoil section works best when the board is lowered to the position shown in the brochure, but at one time, the stop line allowed mine to go much deeper. I don't think there was any noticeable advantage, and it increased the weather helm when close hauled.

The two inch hole in my picture is where the rubbing peg sits, a mushroom shaped HDPE peg in a hard rubber sleeve, which allows some compression, and keeps the peg located in the centre of the hole.
Gerald Freshwater,
s/y 'Castaway', (UK F35 cat ketch)
Lerwick Boating Club
Shetland Isles, Scotland
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Re: Centerboard riggin

Postby Erik » Wed May 16, 2018 6:54 pm

Thanks everyone for the info. There is a bar at the top of my centerboard trunk about 18" aft of the forward edge of the trunk. I have attached a length of 1/2" triple braid between it and the center board to act as a safety and to limit the downward travel of the board. That should do it.

Thanks again
Erik
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