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Catalina/Capri 25/250 Sailor's Forums

Catalina 250 Specific Forum

Centerboard Vectran line travel

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Steve Blackburn
Master Marine Consultant

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Canada
1091 Posts

Initially Posted - 05/27/2007 : 12:09:29

How much purchase should I expect when lowering the centerboard? I went sailing yesterday and I only had about 1 foot of purchase at the Dacron line. Feels awefully short to me, and I suspect my keel isn't going all the way down?

Steve Blackburn, Calgary, AB
C250WB - 1999 - Hull 396

Edited by - Steve Blackburn on 05/30/2007 23:34:37

dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 05/27/2007 : 12:32:48

Steve,

Purchase relates to the mechanical advantage of a block and tackle system like 3:1, 4:1,...etc. I think you are referring to how much tail you should have on the bitter end after deploying the centerboard.

Edited by - on

bear
Admiral

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USA
909 Posts

Response Posted - 05/27/2007 : 12:52:50

Steve, Is it possible the centerboard wasn't up all the way
when you went to lower it? Did you try raising it and re-lowering again? I have my dacron line marked with black tape when centerboard is fully down because I raise the centerboard about a handful when sailing. One foot definitely sounds short.

Edited by - on

Steve Blackburn
Master Marine Consultant

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Canada
1091 Posts

Response Posted - 05/27/2007 : 16:19:03

Hi Guys,

Sorry about wrongfull use of the term "purchase", I'm still learning the new vocabulary.

What I was trying to say is basicaly pulling only about 1 foot towards me then I hear the CLUNK where the centerboard hits the hull. So out in the open water I tried to lower and raise it a few times and found that it took only about 1 foot which can't be right.

I guess I'm going to have to take a swim and check it out. I'll make sure to use bear's trick of putting black tape to mark the spot.

Before I attempt the perilous journey to the deep and risk hypothermia is there another trick I could use to know if the centerboard is down while staying dry (apart from raising it on a lift)?

Edited by - on

bear
Admiral

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USA
909 Posts

Response Posted - 05/27/2007 : 17:57:45

Steve, If you have a docking pole or anything that can reach
halfway under the boat you can feel the contour of the centerboard when it should be full down if you are at a dock or anywhere else you can reach under the boat with that pole. From what you are writing it does sound like it is not going down all the way.

Edited by - on

britinusa
Web Editor

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USA
5404 Posts

Response Posted - 05/27/2007 : 18:31:30

Steve, check the vectran line behind the steps, when fully up, the two blocks should be almost touching one another and when fully down, the top, moving block, should be almost touching the fixed block secured under the cabin entryway.

Now, if anyone knows the exact length of movement of the moving blcok from fully up to the fully down position, please post it!

This weekend, I modified the block system: I replaced the top moving block (which was a double block & becket) with a triple block and becket, then added a third, single block atached just to stbd of the original lower block.
Now my purchase is a 7:1 compared to the original 5:1.

Paul

Edited by - on

Steve Blackburn
Master Marine Consultant

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Canada
1091 Posts

Response Posted - 05/28/2007 : 00:50:21

Bear: I can't believe I didn't think of that obvious method! Thanks, I'll check it out with my docking pole next time.

Paul: Thanks for the tip, I'll check out the block positions next time. How easier is it with your 7:1 purchase? I should expect that ever step up should be twice as easy, so in your case 2 to the power 2 or 4 times as easy right? Please post pictures as soon as you can.

Edited by - on

britinusa
Web Editor

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USA
5404 Posts

Response Posted - 05/28/2007 : 07:30:01

Steve, I'll post pics today, but we don't get to test it out till a week thursday when we arrive in Pensacola for the B.E.E.R. cruise

And in concept you are correct. Each pair of lines on the moving block increases purchase: eg. if the moving block has 2 lines, then for each two feet of line pulled, the block will move one foot, and for each pound of force on the pulling line, two pounds of force are exerted on the moving block.
But then you have friction in the whole system, the smaller the blocks, the less leverage and most likely more friction (friction includes having to bend the line around the block) So adding more blocks eventually increases the fricton to the point where the load cannot exert enough force on the system to allow the moving block to move under the load alone; not good, as in our case, we need the keel to be able to lower itself when we ease the haulin line.

I'm taking enough bits and pieces to make changes when on the water.

Paul

Edited by - on

Second Wind53
1st Mate

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Canada
45 Posts

Response Posted - 05/28/2007 : 11:27:06

Steve my centerboard doesn't come down until I go below and help the line through the blocks. The line is quite stiff and doesn't feed properly. Try opening up the velcro around the purchase and help it go down.

Peter

Edited by - on

Steve Blackburn
Master Marine Consultant

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Canada
1091 Posts

Response Posted - 05/28/2007 : 19:19:52

Second Wind, how much travel (distance) do you think you need on the main line (the one that comes outside). Even a ballpark idea would give me a good feeling on what is normal and what is not next time I'm on the water.

Edited by - on

Arlyn Stewart
Master Marine Consultant

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USA
2980 Posts

Response Posted - 05/29/2007 : 06:17:19

I'm guessing there is 9-11 feet of line travel.

Edited by - on

britinusa
Web Editor

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USA
5404 Posts

Response Posted - 05/29/2007 : 07:25:44

The two blocks can only move about 2' (ish) apart, and it's a 5:1 purchase (not 6:1 unless you boat is rigged different) so Arlyn is on the money 5*2=10'

I'm looking for the actual distrance the lower block moves from keel fully up to keel fully down. ie. If you put a mark on the vectran line where it exits the tube when the keel is fully up, and another when the keel is fully down, how far apart are the marks?

Paul

Edited by - on

Steve Blackburn
Master Marine Consultant

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Canada
1091 Posts

Response Posted - 05/29/2007 : 13:21:48

OMG I don't get near 10'. Too bad we can't lower the keel while on the trailer. I'll let you know next week as I am sailing this weekend and will check out the keel with my docking pole.

Edited by - on

britinusa
Web Editor

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USA
5404 Posts

Response Posted - 05/29/2007 : 18:27:39

Steve, check there are no 'knots' in the vectran line and in the block and tackle system. The vectran line passes through the groove in the turning block (spherical pulley where the line turns from the cabin angle forwards to the lifting block in the keel space.)

Also check the block and tackle are not getting twisted, that'll stop it going down too!

Paul

Edited by - on

Steve Blackburn
Master Marine Consultant

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Canada
1091 Posts

Response Posted - 05/30/2007 : 14:12:52

I'll check the lines, tackle and blocks again. The first time I checked everything was mighty loose. I'll let you know following this week-end. At worst I'll take a swim and pull it down.

Edited by - on

jlannutti
Navigator

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USA
102 Posts

Response Posted - 05/31/2007 : 07:18:44

britinusa and the others posters are all right on the money. Having gone through this recently I know that the blocks should be almost touching when the keel is up and the top block should be at the topmost point it can possibly reach when the keel is down. If you are using the stock setup that is all you can do. I suspect you have a kink, twist, or knot somewhere. Perhaps your line is out of the groove on the ball at the bottom og the black tube going through the hull. A trip overboard with goggles is in order but watch your hands! Aproximately 9 or 10 feet of travel is what you are looking for. I did my replacement with the boat up on stands...I could get the board down only half way so I dug a hole in order to let it travel all the way down.

Edited by - on

Steve Blackburn
Master Marine Consultant

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Canada
1091 Posts

Response Posted - 06/05/2007 : 12:54:02

My sail went fine this week-end. After easing the blocks a little I got about 9-10 feet of travel on the main vectran line. Funny thing is that I checked this that other week-end and something was definitly preventing it from going down. I pulled it up and down many times during last week-end.

Thanks for the help guys. Being so new at this, I really appreciate the help you provide.

Edited by - on

britinusa
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USA
5404 Posts

Response Posted - 06/13/2007 : 22:24:28

FYI, my mod to the keel hauling system was a total flop! After changing the blocks so that the system was a 7:1 purchase, the friction in the system was so great that I could not pull the keel up at all. When I let the line free, the keel could hardly lower itself under it's own weight.

I removed the new block and re-ran the line so that it was only a 4:1 purchase. Now I could not pull the keel up, but it would lower easy.

The water was not clear enough to see if the line is correctly in the wet blocks (turnig block and the final block in the keel trunk)

I'm guessing that the line really must be jambed in somewhere.

Next.

Paul

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