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Catalina/Capri 25/250 Sailor's Forums

Catalina 250 Specific Forum

Centerboard System - admirals peeve

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britinusa
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USA
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Initially Posted - 05/07/2007 : 17:47:25

It's official, the admiral has commanded me to improve the centerboard raising system so that she can manage it.

For those of you that don't know, the C250 WB has a centerboard that is raised by brute force pulling on the line from a 6:1 block and tackle system. If you look at the online manual you'll see the setup.

I took a long hard look at the whole thing, sadly I'm missing one piece of info: what is the distance between the blocks when the keel is fully lowered?

Besides that, here's my review of the keel hauling system (has a certain ring to it 'keel haulin'

Observations:
<ul><li>There are too many useless turning points: The Pull from the cockpit first turns via a Garhauer Block which does nothing more than direct the line down to the bottom block. The angle of turn is about 120degrees. Angles outside a straight line increases friction. </li><li>The line next turns around a useless wheel in the lower block, I say useless because it does not increase the purchase, it simply increases friction.</li><li>The Vectran line turns 180 degrees at the underide of the cabin entrance, again this does nothing for the purchase, but again increases friction</li></ul>

Here's my concept:
<ul><li>Shorten the vectran line so that when the keel is fully down, it just extends up out of the 'tube'</li><li>Shift the lower block to the end of the vectran line </li><li>fix the top block to the current turning point of the vectran line</li></ul>

This setup would expand the turn angle of the line from the cockpit, reducing friction, makes the most of the mechanical advantage of the 6:1 block and tackle, eliminating the friction of the top vectran turning point, eliminating the friction of the lower block turn.

This all depends upon the distance between the blocks when the keel is in the fully down position. JD is on the trailer right now so I can't make that measurement.. anyone got it handy?

Paul

Joint Decision. (Sold)
PO C250WB 2005 Sail # 841.

Moved up to C34 Eximius

Updated August 2015

Edited by - on

delliottg
Former Mainsheet C250 Tech Editor

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Response Posted - 05/07/2007 : 18:23:59

Paul,
Is it possible to use a [url="http://www.tpub.com/content/engine/14037/css/14037_23.htm"]luff upon luff tackle[/url]? Like maybe a 4:1 handy-billy to increase her pulling power on the 6:1 tackle? I've only been inside a couple of WB's so I don't know where or how you could mount it, or even if it's feasible.

Take a look at [url="http://sharp.bu.edu/~slehar/GantryWebpage/Gantry.html"]this page[/url] to see how they raised a boat off it's cradle with an A-frame, a six part fall and a handy-billy in luff on luff. Pretty interesting to read. Maybe it'll give you some ideas?

Good luck,

Edited by - on

britinusa
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Response Posted - 05/07/2007 : 19:25:54

David, that page about lifting the boat with A Frames took me back to a Royal Navy leadership school project in 1972. A team was trying to turn an articulated truck and cab on its side (probably so someone else could right it!) using a block and tackle. With far to much manpower on the heaving line, all they could do was drag the truck sideways. I got picked out to come up with a solution: Simple! Mount an A-frame on the side of the truck bed and run the line over the top of it and down to the far side of the truck. Once setup, a handful of guys on the heaving line easily flipped the truck. Give me a lever and I'll move the world!

Anyway, back to your handy billie concept: sadly it would not work as the lower block has to move somewhere around 18" x 6:1 (but I think it is only rigged as a 5:1) so that equates to 90" of line, and there's only about 36" of space below the cabin access. I could use one in the cockpit, but now I would require the admiral to not only heave on the line but also deal with 21' of line (assuming a 3:1 billy)

However, you did cause me to note that another prospect to reduce the effort would be larger Blocks (greater advantage)

Paul.

Edited by - britinusa on 05/07/2007 19:31:29

Arlyn Stewart
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Response Posted - 05/07/2007 : 21:22:30

It might work... but the triple block might also rotate under the angle of pull causing the line to bind somewhat or even possibly induce twist into the b&t as was typical if there was no twist shackle used to mount the lower block.

Only one way to know for sure.

I had problems with mine until the twist shackle was moved from the top block to the bottom block... Catalina drawing shows the twist shackle on the top block... but that doesn't work well and induced twist knots into the b&t.

Edited by - on

delliottg
Former Mainsheet C250 Tech Editor

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Response Posted - 05/08/2007 : 08:47:58

Sounds like you did more fun things in the Royal Navy than I did in the USN. I think the most fun I ever had was rigging "Med lights" for xmas each year. I was the only one in my shop who <i>liked </i>going up the mast. I'd suit up in a down jacket, long underwear, ski gloves & wooly hat (remember it was nearly xmas), and slog my way to the top of the mast carrying a messenger line with a lead weight and a radio. I'd rig the messenger line to a block at the top of the mast then drop it to my guys on deck, and they'd work their way all the way aft with it. Then they'd have to heave on the messenger line to drag string after string of lights to the top of the mast, while I stood in the stirrups and watched, mostly just looking at the view from up there. After they got the stern set rigged, we'd do it all over again to rig the lights forward. Most of my time was spent sight seeing, while the rest of the guys were grunting the lights up. After the holidays were over, we'd get to do it all over again in reverse, so another whole morning of sight seeing for me.

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Nautiduck
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Response Posted - 05/08/2007 : 10:21:53

Have any of you WBers considered adding a power motor/winch to handle the centrerboard system? Seaward uses one on their retractable keels. Their keel arrangement is different (vertical lift) but there is the precedent of using power to do the work. Then the Admiral can just push a button!

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dlucier
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Response Posted - 05/08/2007 : 10:31:06

Just curious...How many pounds of force does it take to raise the centerboard?

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bear
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Response Posted - 05/08/2007 : 18:21:52

As hard as it apparently is I think you would still want to feel the action of this system. My centerboard is not to bad, but I still have an unpainted bottom thusly no paint on the turning ball or pulley, my pre-launch includes coating the turning points with WD 40.

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britinusa
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Response Posted - 05/08/2007 : 19:49:24

Don, in answer to your question <blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">How many pounds of force does it take to raise the centerboard?<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

Not sure how to spell it "^%$(*&$# weigh to much!" There is no way the Admrial could raise the centerboard.

Paul

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Arlyn Stewart
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Response Posted - 05/09/2007 : 06:19:42

Randy... actually there is a tech tip illustrating the installation of an electric winch for the center board. The tip has been there a very long time.

My concern with doing so is that to raise the board hard up might be part of the cause of failures of the cable so I'd want a system that had limitations. That seems doable but begins to make an electric winch a little more complicated.

However, for someone not physically able to handle the board, it would be well worth the effort to design and construct such a system.

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dlucier
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Response Posted - 05/09/2007 : 06:43:13

If it's that heavy, I'd consider increasing the purchase on the centerboard tackle. As Martha would say, "Mechanical advantage...It's a good thing".

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britinusa
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Response Posted - 05/09/2007 : 07:24:44

Decided to take baby steps to improve the lift.
Objective: Make the current 5:1 ratio a true 7:1 ratio
Method: Replace the upper block with a Harken Big Bullet Tripple block with becket (#130 WM2006Catalog Page 867) and add a Harken #082 Single block attached to a new eye strap to stbd of the existing eyestrap.

The moving block will still be the upper one, but it will have 7 lines.

FWIW, during the research for this, I found that the blocks currently used are kinda inappropriate. According to the Manual, the line is 3/8" Dacron, but the #86 & #85 Harken blocks have a max line size of 5/16". I see no benefit in using the thinner line, so for now I'm going to get the bigger block for the top and the additional block.

As this mod can be easily implemented on the water, I'm going to add the addtional eye strap before our next trip, then when on the water I'll try to measure the load to lift prior to the mod and again after the mod.

Anyone got appropriate blocks they want to release?

Edited by - on

Nautiduck
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Response Posted - 05/09/2007 : 09:39:24

Arlyn, could a person add a rheostat to the electric motor and make a mark on the cable 6" from the stop point? Use the motor at full power until the mark is seen and then power down the final few inches.

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Arlyn Stewart
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Response Posted - 05/09/2007 : 20:12:39

Paul... going back to your original question about the travel distance... I'm doubting there is enough travel distance. If I recall correctly there is only a few inches of tolerance in where the cable is clamped to the upper block but to have the lower block do the cable hauling is to yield the travel distance from where the eye strap is pretty low to just above the radiator hose. That is a fair distance if I recall and probably more than can be subtracted and still yield the needed travel.

As to how to manage an electric winch... the simplest way would be to mark the cable in some way and simply watch it as the winch is operated but that would require going below to manage the board, not all would like that.

Also, the hand system when not working well quickly tells the owner that maintenance to the system is needed... an electric winch might not telegraph a system in need of maintenance and an electric winch might break things.

An alternative might be a trailer winch. For example... the original mast raising system used a block and tackle almost identical to the boom vang that provided a 4:1 ratio only slightly less than the 5:1 ratio of the center board system. That mast raising system required a fairly strong pull on the B&T at certain positions of the mast. However, when I converted the mast raising system to a trailer winch bolted to the gin pole... the winch was almost effortless to lift the mast.

If I were attempting to provide a system to make it easier to handle, I'd think either a trailer winch operated from the cabin or somehow redirect the line to a sheet winch.

It seems to me it would be quite easy to do a small trailer winch.

Edited by - Arlyn Stewart on 05/09/2007 20:29:06

Oscar
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Response Posted - 05/10/2007 : 11:12:59

Don't recall it being THAT hard......you sure everything is running on the sheaves and the sheaves are turning? Also, I assume there's no side load on the board when you're pulling it up? Does it swivel freely? Time for a haulout/check or a swim?

If all of the above is in order and you still need improvement I would look at putting a small winch in the cockpit....no need to get crazy with electric.

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britinusa
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Response Posted - 05/10/2007 : 13:53:05

I can peek down the 'radiator' hose and see the vectran line is in the groove of the turning ball. Cannot dertimine if the ball rotates without dropping the keel (boat is on the trailer) the keel appear to move ok, it just seems that the rigging is wrong, it has always been this tough to pull it up.

Paul

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Dave Bristle
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Djibouti
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Response Posted - 05/28/2007 : 13:41:49

If you do a trailer winch, you could probably substantially reduce the B&T purchase, and thereby the turns of the winch needed to raise and lower.

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zebra50
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Response Posted - 06/06/2007 : 11:29:06

Arlyn
when you relocated the twist shackle to the lower block, what did you use to attach the single block at the top block?

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Arlyn Stewart
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Response Posted - 06/06/2007 : 11:46:23

I simply traded the straight shackle for the twist shackle.

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zebra50
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Response Posted - 06/06/2007 : 12:12:45

thanks, I will make the change. I didnt notice a straight shackle on the lower block. I did find the upper block needed a bit of WD 40 to run smoothly.

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Arlyn Stewart
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Response Posted - 06/06/2007 : 22:02:36

My upper block needed some attention as well. It was nickel plated and the straps squeezed in a bit and it really drug. I removed the sheave and sanded off the plating to the brass and opened the straps slightly adding thin nylon washers to keep the block off the straps. Every effort in that whole system adds up.

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