Keel Doesn't Quite Match Hull - Cherubini H36
- Thread starter rardiH36
- Start date
Rardi's point about keel misplacement
Rardi, I can't possibly imagine that some minor shortening or malpositioning of the keel could matter much in the real world. For one thing, if you had even a little too much chain in the bows it would then probably be a good thing. Most boats squat terribly by the stern, due to gear and too many people and added accessories; keel weight a little too far forward will help. Indeed most boats should float, when entirely empty, a little higher by the stern, in anticipation of how they'll be loaded.
As for the lateral resistance, the same case can be made. If the boat were to be trimmed down by the bows, that's more boat under water, more wetted area and more lateral resistance. It's also an increase in weather helm, which, in low doses, amounts to higher pointing ability. If it were deeper by the stern, you'd have the opposite. Either of these 'errors' could actually make up for some imperfections of design or build quality; which is why I so often try to make the point that there is very little precision or purity in design to be expected of mass-produced boats. What appears 'right' or 'true' on paper may be precisely countered by the reality. So let's not worry too much about these things. Half the time (or more often), tactfully asking the heaviest person on the boat to move 12 inches one way or another can make a difference. (The rest of the time, nothing that's done will ever show you a result!)
And, as far as fairness goes, my boat's keel had a pronounced bulge along one side (I forget which; it's in the blog) so I actually started grinding and planing down the lead. Then I reconsidered what an idiot I was and, after researching some NACA airfoil shapes, applied filler to the flatter side instead. I suspect most deep-draft H25 owners will have asymmetrical keel shapes as well. :cry:
Rardi, I can't possibly imagine that some minor shortening or malpositioning of the keel could matter much in the real world. For one thing, if you had even a little too much chain in the bows it would then probably be a good thing. Most boats squat terribly by the stern, due to gear and too many people and added accessories; keel weight a little too far forward will help. Indeed most boats should float, when entirely empty, a little higher by the stern, in anticipation of how they'll be loaded.
As for the lateral resistance, the same case can be made. If the boat were to be trimmed down by the bows, that's more boat under water, more wetted area and more lateral resistance. It's also an increase in weather helm, which, in low doses, amounts to higher pointing ability. If it were deeper by the stern, you'd have the opposite. Either of these 'errors' could actually make up for some imperfections of design or build quality; which is why I so often try to make the point that there is very little precision or purity in design to be expected of mass-produced boats. What appears 'right' or 'true' on paper may be precisely countered by the reality. So let's not worry too much about these things. Half the time (or more often), tactfully asking the heaviest person on the boat to move 12 inches one way or another can make a difference. (The rest of the time, nothing that's done will ever show you a result!)
And, as far as fairness goes, my boat's keel had a pronounced bulge along one side (I forget which; it's in the blog) so I actually started grinding and planing down the lead. Then I reconsidered what an idiot I was and, after researching some NACA airfoil shapes, applied filler to the flatter side instead. I suspect most deep-draft H25 owners will have asymmetrical keel shapes as well. :cry:
John:
Thanks your insights in regards that small mis-alignments of the keel on the stub probably don't mount to much. I am not going to do anything about it to my boat.
Looking back through this thread at my posts, I guess the main conceptual element I had considered was my back-of-the-envelope calculation of lead weight shortage since the keel on my boat isn't only mounted too far back, but also appears to be short across most of the width as well (as compared to the width of the keel stub.) If I was along the northeastern seaboard where boats are hauled for the winter -- affording lots of futz around time -- I might contemplate finding a hunk of lead of say a few inches thick. Then maybe 3M 5200 bedding it to the flat bottom of my existing keel. Figure out a way to mechanically reinforce the joint. And see what happens under sail. In normal/low winds I wouldn't expect anything. But in the strong blows of SF Bay, maybe the extra mass low down would cause a bit less heeling and a bit more of lateral resistance afforded by the larger keel profile might be noticeable. An "academic folly" however. Never to be done.