Replace centerboard control line

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Replace centerboard control line

Postby Erik » Tue Apr 03, 2018 9:41 am

I need to replace the centerboard control line on my 33. Does anyone know how to get to the top of the board what needs to be removed etc

Thanks
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Re: Replace CB control line

Postby Goose13 » Tue Apr 03, 2018 3:30 pm

mine has a little portal that you get to inside next to the table, I can only get my arm in so its a one hand job. I can also access my trunk from the deck when I remove the plastic plate.
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Re: Replace CB control line

Postby Castaway » Thu Apr 05, 2018 6:41 pm

On the UK built boats, you have to remove the top of the centreboard case; two layers, one cosmetic wood, the other GRP sealed to the case. Then you can get at the blocks, sheaves and pennant. Make sure you watch the order and direction around the tackle, since crossing lines will increase the effort of lifting, and lead to early chafing of the pennant and/or failure of the block on the board end of the tackle. I know this from repeated personal experience. :cry:

Wire was usually used for the pennant, but I manage well with 10 or 12 mm rope, which goes onto a normal winch. The wire needed a dedicated winch unusable for anything else.

CB (1).jpg
The centreboard tackle, viewed from aft with the board raised
CB (1).jpg (238.37 KiB) Viewed 600 times


I don't know if this is representative of the original US build.

Make sure you have something substantial to support the board whilst you replace the line; the board weighs better part of half a ton. You can do it with the boat afloat if you make off a supporting line to a stout bar across the casing from the CB attachment point. With the board up, the line is out of the water. Don't drop pliers or a shifter inside, since the lucky result of that is for the tool to sink to the ocean floor; the unlucky one is for it to jam in the casing and block the board's movement. At least I was on land when I found that out.
Gerald Freshwater,
s/y 'Castaway', (UK F35 cat ketch)
Lerwick Boating Club
Shetland Isles, Scotland
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Re: Replace CB control line

Postby Erik » Fri Apr 06, 2018 3:56 pm

Thanks so much for the info. Mine has rope all the way to the winch. One picture speaks a 1000 words. Thanks again.

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Re: Replace centerboard control line

Postby andygc » Sat Apr 07, 2018 4:25 pm

I've just been experimenting with the rigging of the plate uphaul on my F30 - it's the same layout as the F33/35. Its technical name is a "winding tackle". I've ended up slightly different from Gerald's arrangement - for a start, I don't have room for that long bowline onto the becket of the double block. I tried rigging it with the block at 90 degrees to the fixed sheaves - Ashley Book of Knots serial 3253 - but that didn't work for me. I then went for serial 3261 (although you have to think it upside down because the lead sheave is not in line with the other two fixed sheaves)
IMG_0001.jpg
IMG_0001.jpg (62.35 KiB) Viewed 548 times
IMG_0002.jpg
IMG_0002.jpg (68.03 KiB) Viewed 548 times

Imagine that you are looking up from underneath and that the hauling part goes up and away from you, not coming at you as shown. Note the crossover of the left hand turn.

Don't drop pliers or a shifter inside, since the lucky result of that is for the tool to sink to the ocean floor; the unlucky one is for it to jam in the casing and block the board's movement.
:D The fragments of the plastic sheave fitted by a previous owner to replace a bronze sheave are equally unlucky. It was a real struggle dropping the plate out when I got the boat as the broken sheave was very difficult to poke out. The boat was hanging on the crane for a couple of hours!

By the way, when you refit the top of the trunking, you might not want to use silicone sealant. You will need to get into the casing again, and single component polysulphide sealant does not set. I use Arbokol 1000.
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Re: Replace centerboard control line

Postby Erik » Sat Apr 07, 2018 6:40 pm

Thanks again for all your help
Erik
33 Cat Ketch #74
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Re: Replace centerboard control line

Postby Castaway » Sun Apr 08, 2018 8:40 am

I would definitely support Andy's comments about non-setting sealant; after a boat-repairer had used Sikkaflex, I had to cut the cover into pieces to remove it, then rebuild it with more GRP to replace again.

His comment about the long bowline is pertinent; it prevented me from raising the board fully on my F33/35. I would have preferred a fisherman's bend, but it was too bulky at the becket on the block, so the weaker bowline has to suffice.

The layout of the 'winding tackle' is dictated by the positions of the fixed, and offset, sheaves at the forward end of the casing;
CB.jpg
view of the forward CB case, with fixed sheaves
CB.jpg (231.08 KiB) Viewed 529 times


On UK boats, the upper sheave leads the pennant through a tube to another sheave on deck, then aft to the winch. I checked several variants of order and direction, until I found one with the least contact between the lines when under tension. I currently have a 12mm line in place, which is probably a mistake, since it is harder to haul. Next time, I'll use an aramid fibre line of 8 or 10 mm. I expect there will be a next time.
Gerald Freshwater,
s/y 'Castaway', (UK F35 cat ketch)
Lerwick Boating Club
Shetland Isles, Scotland
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Re: Replace centerboard control line

Postby andygc » Sun Apr 08, 2018 5:42 pm

His comment about the long bowline is pertinent; it prevented me from raising the board fully on my F33/35. I would have preferred a fisherman's bend, but it was too bulky at the becket on the block, so the weaker bowline has to suffice.

Have you thought of using a halyard knot - it works for me.

Image

In fact, because I've very limited space, I've gone a half turn less. It's never going to slip with 12mm line permanently loaded by the weight of the plate. Indeed, the thickness of the rope is a help in making the knot secure as the edge of the becket digs into the tail. A useful knot - it jams up hard, but can be picked apart fairly easily with a spike.
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Re: Replace centerboard control line

Postby Castaway » Sun Apr 08, 2018 6:50 pm

Andy, I think that's the knot I call a 'fisherman's bend'; I don't have access to Ashley's book, so will bow to your nomenclature. Would it hold with a modern aramid rope (Dyneema), notoriously bad with knots?

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s/y 'Castaway', (UK F35 cat ketch)
Lerwick Boating Club
Shetland Isles, Scotland
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Re: Replace centerboard control line

Postby andygc » Mon Apr 09, 2018 10:00 am

Fisherman's hitch/anchor hitch
http://www.animatedknots.com/anchor/index.php
Halyard hitch/halyard knot
http://www.animatedknots.com/halyard/index.php
Should work with modern ropes, but don't cut the tail very short. It's very widely used as a way of attaching halyards to shackles, avoiding the stiffness that is caused by splicing braided rope, and I have seen many comments on sailing forums about using it with Dyneema halyards.
There is also the buntline hitch, but I don't think that is as secure.
http://www.animatedknots.com/buntline/index.php
Note the comment about the EStar hitch, but that would require the line to go twice through the becket.

I drew a new version of the arrangement from Ashley to show how I have it rigged on my plate.

plate tackle.jpg
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