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  #1  
Old 06-29-2008
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Lift Keel Locking Mechanism

I have a Swarbrick S80(26 feet) with a lift keel.The survey done at the time of purchase states that part of the keel locking mechanism is missing. The locking mechanisms which are present appear to lock the keel in the 1/4 and 1/2 down position.
The locking mechanism is a screw which pushes the rectangular centreboard aft in a rectangular keel trunk (my apologies if the terminology is not correct).
This seems to me like a substandard arrangemet because even with the keel locking bolts done up as tight as possible with a 15" shifter the keel rocks about fore and aft as well as side to side.
The keel is a torpedo shaped lead ballast of about 350 kg on a centreboard 700mm X 75mm by 1200mm deep.
Anyway my question is if I have to come up with a new keel locking mechanism, should it be strong enough to support the rest of the vessel in case of a grounding or deliberate beaching or should it be the weak point which allows me to regain safe water in an emergency?
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It sounds to me, if I'm reading your description correctly, that the mechanism you are describing holds the keel in position and is not related to the lifting or lowering mechanism.

My concern would be the sloppiness in the keel. Is it moving about when fully lowered or only in the partially retracted position? I'm thinking that something is worn in either the keel trunk (perhaps missing bushings) or on the centerboard itself. If so, that wear is going to promote more wear, potentially in more serious places. I'd investigate that fairly soon.

There are two schools of thought on locking pivoting or drop keels/centerboards. The first holds that it should always be locked in the event of a knockdown or rollover. Aside from the loss of righting moment (stability) there is the potential for hull and keel trunk damage, perhaps quite severe. The second school of thought advocates keeping the keel unsecured so as to ride up in the event of a grounding.

There is some logic to the second school of thought in that it may not result in quite as hard a grounding but the keel will most likely have to be further retracted to unground the boat in any event. Much depends on the force of the grounding. Unsecured may lead to damage to the keel and it's mountings as well by it's being potentially torqued in a hard grounding. In a softer grounding, one may be able to just raise it a bit and sail or motor off.

I suspect that there are many, if not most, keels wandering about out there unsecured. It really depends on the sailing conditions encountered, I suppose. I would though, take the sloppiness seriously until there is evidence that it is "normal". I suspect that it is not.

The problem with designing a locking mechanism that can intentionally fail, as in a grounding, is in constructing it so that it still offers the strength to hold the keel in a potentially violent rollover. I have what is called a swing keel of some 400lbs (181kg) and I leave it unlocked for gunkholing (puttering about in shallow water) but lock it when sailing in deeper waters. I've a steel pin that secures it and have thought many of the same thoughts that you no doubt have. I'd rather have it shear than bend in a hard grounding, while still supporting the keel in more traumatic circumstances. So, I've ruled out a softer pin of brass or aluminum as they'd offer me the worst of both world's-a jammed locking pin. And I've not seen anything else, in a 1/2" diameter, that I'm sure I'd trust in a rollover. I've thought that some two hundred year old oak from an old farm-house, the kind you can no longer pound a nail into, might be the ticket but that has not gone past the speculation stage. (g)

If you can post some photos I'm sure that others might have some good information to offer.
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Old 06-29-2008
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First, you don't have a centerboard. A centerboard is a specific type of lateral resistance device on a sailboat that consists of a "centerboard" that pivots in a centerboard trunk. A swing keel is often a heavily weighted version of a centerboard.

It sounds like the way your lifting keel is locked is by pushing it aft and using friction to lock it in position against the aft end of the keel trunk.

Depending on the profile of the keel trunk, the keel and the locking mechanism, it may indeed have some slop. Without knowing the profiles of the various pieces, you can't really say if the slop is normal or abnormal.

The problem with a lifting keel is that any serious grounding will generally apply forces in two directions—aft and upwards. This is probably why the existing mechanism pushes the keel aft—to minimize the damage that can be caused in a grounding, by reducing the aftward movement the keel can make. Unless the keel has some sort of positive locking mechanism, I don't think you can remove the slop or prevent the keel from moving in a grounding—friction alone probably isn't sufficient. However, using a positive locking mechanism, like Sailaway's "pin" will cause other issues.
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IMHO, boats in the 25' size range with ballasted swing keels are primarily designed to be sailed on inland lakes and on coastal waters in reasonably fair weather. You can put a pin through the keel, and that might prevent it from retracting in a rollover, but if the fiberglass structure isn't strong enough to withstand the stress on the pin, structural damage will likely occur. Generally, I would avoid sailing any small, trailerable, pocket cruiser with a ballasted swing keel in conditions so severe that a rollover might result. Use the boat for the purposes for which it was designed. As long as the boat remains upright and isn't pounding too much, the keel's weight will hold it down reasonably well. The greatest danger arises only when a rollover might occur, or with excessive pounding.
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I think you're a bit confused. The OP doesn't have a SWING KEEL, at least from his description, as it has a bulb on it. I believe it is an actual LIFTING KEEL. Sway has a swing keel.

Quote:
Originally Posted by Sailormon6 View Post
IMHO, boats in the 25' size range with ballasted swing keels are primarily designed to be sailed on inland lakes and on coastal waters in reasonably fair weather. You can put a pin through the keel, and that might prevent it from retracting in a rollover, but if the fiberglass structure isn't strong enough to withstand the stress on the pin, structural damage will likely occur. Generally, I would avoid sailing any small, trailerable, pocket cruiser with a ballasted swing keel in conditions so severe that a rollover might result. Use the boat for the purposes for which it was designed. As long as the boat remains upright and isn't pounding too much, the keel's weight will hold it down reasonably well. The greatest danger arises only when a rollover might occur, or with excessive pounding.
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Old 07-01-2008
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My boat had a plastic rod, about 1", that used friction only to keep the keel from banging around. It was badly rusted (the mechanism for holding the rod against the keel) and did not function anymore so I just removed it. No one with a Chrysler 22 had one anyways so it may have been an after market modification. The keel, at 900 pounds with its pivot right at the bottom of the boat a good foot below the water line (the boat displaces 3000 lbs a lot for a boat that size), has not done any banging yet even in heavy weather, and though I've not been offshore yet, the previous owner frequently was and never had the problem. I'll not be testing it in any typhoons myself in the foreseeable future though. I am not sure a locking mechanism that does anymore than minimize vibration is a good idea, especially on a swing keel. I think if conditions are such that the keel retracting from flipping over was possible I would already have it retracted, sails down, motor on or sea anchor deployed to wait out the storm.
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Old 07-01-2008
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Perhaps the missing parts are something the fits into some sort of notch that forces the keel into stability.

You might have to drop the keel to replace.

Rick


[quote=Uglydave;334980]I have a Swarbrick S80(26 feet) with a lift keel.The survey done at the time of purchase states that part of the keel locking mechanism is missing. The locking mechanisms which are present appear to lock the keel in the 1/4 and 1/2 down position.
The locking mechanism is a screw which pushes the rectangular centreboard aft in a rectangular keel trunk
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More information

Firstly thanks everyone for your replies
I have done a little bit of investigation and now I'm sure I'm going to change the way I lock the keel. I took the top locking screw out of the keel trunk.Think a round plate with a nut welded to it and a bolt threaded through. The plate is fastened to the keel trunk with three self tapping screws...This is the reason the bottom locking screw is missing. It was tightened up by someone with a bigger spanner than I had, just pulled those self tappers right out.
Anyway the reason I took the screw out was to get a better look at where the screw goes in the keel, maybe a stainless recessed plug of some kind or a textured rubbing strip to add resistance to movement? Nope, straight onto the fibreglass. So now I'm thinking a stainless pin around 1/2 inch diameter to slide into a bush drilled into the keel. I'm going to have to pull the keel out anyway to repair the damage, might as well fix it properly
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Good idea, Dave. Best to do it right, once. Given that it's a moving part, you'll probably find more about it to repair and re-do. good luck to you
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