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OK not to start another keel thread but, OK I guess I will do just that.

I was out in the ICW this weekend and severial large fishing boats passed me on there way in from the guldstream. These guys spend a lot of time on the water and think they own it and dont worry too much about their wakes around smaller boats. We were motoring with the keel up and bing tossed around pretty good. So I put the keel down to damper the rolling motion which did help. But what tremondus forces it must put on the keel. Any thoughts.

Forces like that are definitely hard on the pivot hole, and especially with the keel in the "up" position. In the up position, all of that weight is held up by that relatively narrow stretch of metal between the pivot bolt and the trailing edge...the weakest spot on the whole thing.

ChockFullOnuts22 wrote:Forces like that are definitely hard on the pivot hole, and especially with the keel in the "up" position. In the up position, all of that weight is held up by that relatively narrow stretch of metal between the pivot bolt and the trailing edge...the weakest spot on the whole thing.

While I would agree with there being a lot of stress, I would have to disagree as to where it's the worst. If the keel is pulled up, the lead at the base is directly under the cable, aft. So the stress on the keel bolt would be less in the up position than when it was lowered all the way down. When I rebuilt my keel , it was very awkward to work with because the center of the weight is only about 3 or 4 inches from the bottom. When the keel is pulled up tight to the hull, very little weight is on the pivot bolt.

Yes, you're right about the weight distribution. But there's still plenty of weight on that bolt, even if only a fraction of what the cable is supporting. Still, that relatively narrow stretch of metal between the pivot bolt and the trailing edge is the most vulnerable spot on the keel, itself, when forces are applied. Hence keel failures. And gravity isn't the only force at work on the pivot point. As Pete stated with his experience, lateral movement at that point is also a concern. The cable holds the weight of the keel up against gravity, but does nothing to prevent the end of the keel from swinging side-to-side when the boat is rocked. Now you have the weight of the keel moving in a different direction than gravity, rotating the wrong way against the pivot bolt.

Granted, a keel in good condition is not going to experience a failure from a little bit of rocking around on the water; but that movement repeated over a longer period of time will accumulate mechanical wear that will oblong the pivot hole and could eventually lead to a keel failure.

The forces that I was concerened about were the side forces of the water against the keel not the weight. The stress IMO would be concentrated where the keel exits the trunk, like trying to break it off. I would guess the hull would fail before the keel.

You know, I mis-read your first post. I thought you were talking about forces on the keel in the UP position while in rough swells, rather than the down position. Sorry about that.

If you're worried about your keel fracturing off at the bottom of the trunk in those turbulent conditions, don't be. Like you said, hull failure would likely happen first. The greatest stress points would probably be concentrated where the trunk meets the hull bottom, rather than near the pivot point.