Is adding a fin or bulb to a fin keel ok? - SailNet Community
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post #1 of 11 Old 09-10-2008 Thread Starter
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Is adding a fin or bulb to a fin keel ok?

Greetings,
I would like to get some educated opinions about adding some weight to my dagger board. It weights about 370 lbs now and I would like to add more. The reason is that my boat heels quickly and I mostly sail alone, no rail meat. The boat displaces 3000 lbs, and has 1140 lbs of ballast (including the dagger board). I can not add any length to the DB, but I could add a bulb or a fin to the sides. How much weight should be added to get any benefit? I sail on a large inland lake and we get thermals that come up fast and I want more stability before I have to reef.
Kevin
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post #2 of 11 Old 09-10-2008
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Lay of the vang a little... I have read articles about people changing their deep fins to shoal draft but bulbs on a daggerboard? Whenever you have a fin the pivots or lifts its initial design and construction is usually adequate to handle its design weight but no more. Learn to handle your sheets like you would in a dingy, let off the boom vang, maybe get your sails cut a little flatter but don't go modifying the hull. Even if your modifications were reasonable successful they would probably trash the resale value of the boat.
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post #3 of 11 Old 09-10-2008
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The force on the sails goes up with the square of the wind. It is not then feasible to increase the righting moment say 4 fold to cope with a sudden doubling of the wind speed.
Use your traveller more maybe, but the adequate sail area for say 15 knots will be excessive at 20 so you have to use other sailing techniques.
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post #4 of 11 Old 09-10-2008 Thread Starter
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Thanks guys,
But I do move the traveler etc.... I am just wondering if I added say, 100 lbs to the bottom of the keel, it has to help with the righting forces of the boat. My other boat had more ballast to displacement ratio and resisted heeling better, of course. So has anyone else considered or done something like this? The dagger board in the boat is lead encased in fiberglass and is strong enough to handle the added stress, as is the mechanical lifting winch.
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post #5 of 11 Old 09-10-2008
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I would be cautious about adding ballast, especially at the bottom of the board. Increasing the ballast on the board will increase the forces the board is subjected to, the forces on the lifting rig and the forces on the shrouds. If not done properly, you're much more likely to snap a shroud and lose the mast.

Have you done as much as possible to flatten/de-power the sails?? Are the sails in good shape or are they all blown out.

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post #6 of 11 Old 09-10-2008
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Despite your handle, this does not sound like the Ranger 26 that I'm familiar with.. knowing more about your boat would help.

I doubt that 100 lbs would make a significant difference to the behaviour of your boat, and you may well stress the daggerboard system somewhat.

If it's a new-to-you boat with older sails, you may be amazed at the improvement that would come with a fresh set.

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post #7 of 11 Old 09-10-2008
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Quote:
Originally Posted by sailingdog View Post
I would be cautious about adding ballast, especially at the bottom of the board. Increasing the ballast on the board will increase the forces the board is subjected to, the forces on the lifting rig and the forces on the shrouds. If not done properly, you're much more likely to snap a shroud and lose the mast.

Have you done as much as possible to flatten/de-power the sails?? Are the sails in good shape or are they all blown out.

I agree SD, and my caution would be in direct proportion to how much I cared about the boat.
If you push the envelope far enough something will break.
If you don't mind getting wet and fixing what you break, Whose to say whether it's worth it or not.

I am often asked about up sizing rigging. My usual response is that it was designed by someone who actually went to school to learn how to design things, and it has performed for however many years without failing and that I don't feel qualified to second guess the designer.
I tell them that there is always a "weakest link" and unless they are willing to follow through and beef up the entire system, then they are not really gaining much.
But the customer is always right. And if it helps them sleep better at night, I'll take their money.
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post #8 of 11 Old 09-10-2008
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Put some bricks or stones into the bilge. If you start to get the effect tht you're looking for, then buy some proper pig iron ( actually cast lead weights). Rig some type of restraining mechanism so that they don't move when you heel.

Don't alter the boat permanently. You will affect the balance and you will never be able to sell it.

Good Luck ! Hope everything works out well
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post #9 of 11 Old 09-11-2008
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sail area -disp.

If yours is the model I think it is you have almost a 22 to1. No wonder she heels quickly, but that is the design. How about upgrading battery bank and adding some weight that way, try different locations for trim before fastenig and wiring.
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post #10 of 11 Old 09-11-2008
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IF you do add internal ballast, avoid loose stones, bricks lead shot etc., if at all possible. The last thing you want is to heel, spill the ballast and really unbalance your boat. Lead pigs, make certain to secure whatever you use. If you add lead, cover it well and don't allow water to slop all over it, acting as a vehicle taking lead residue wherever the slop goes.
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