Keel Designs

Discussion in 'Boat Design' started by ptoliv, Mar 19, 2010.

  1. ptoliv
    Joined: Mar 2010
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    ptoliv Junior Member

    Any ideas on keel conversions on old ocean racing boats? The standard keel is cast lead bold on fin with standard tapers and 2 rows 8 stainless bolts, a 1980's design. The keel weighs about 8500# with much of the weight in the upper section, the boat is 45x13. This will have to be a budget operation because of the age of the boat. What about modifying a used bulb keel to get weight down a bit? This boat will never see IOR again, but would make a fine PHRF racer. Thanks for any comments.
     
  2. gonzo
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    gonzo Senior Member

    Why are you trying to modify it? With PHRF if you improve a boat they will penalize you more. Also, adding stress to the keel attachment area will involve a lot or re-engineering. You are unrealistic to want this kind of job on a budget, at least a low one.
     
  3. ptoliv
    Joined: Mar 2010
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    ptoliv Junior Member

    Keels

    The existing keel is damaged and some of the bolts are missing or bent. Also the area of the stringers where the original keel was attached is damaged (aluminum hull). Not bad but bent in slightly near the rear of the keel area. It would make sense to broaden the attachment area and spread the load over more stringer and move the keel weight down at the same time. The PHRF is already 36: if re-rated it might go up a bit. Do you thing there is a used bulb keel out there that could be modified?
     
  4. gonzo
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    gonzo Senior Member

    You can use the same lead and recast it. I think that if the bolts are bent and damaged, you need someone knowledgeable to inspect the boat. There may be metal fatigue that will eventually crack and fail. Local reinforcement can be worse if not engineered properly. They often create hard spots that overstress and fatigue small areas.
     
  5. daiquiri
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    daiquiri Engineering and Design

    I agree with Gonzo's last post. Not only fatigue, but if stringers are damaged due to a grounding, or a hit against something, the bent area needs to be inspected in order to assess the residual resistance of the deformed area.
     
  6. ptoliv
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    ptoliv Junior Member

    Thanks for the good info. We will be doing a major inspection in the damaged area with that in mind. The stringers are on 2' centers and have 6" round hole cutouts for weight reduction, stress relief, and damaged control. I think your idea about recasting the keel is good. Do you have anyone in mind that may be able to do this in the southeast. The draft of the boat is near 10' and to race coastal needs to come up to 6'. I know that sounds short, but with the bulb design 80% of the ballast is moving to 6'. If the keel is fabricated for lead filling instead of casting what is the best metal? How about Alum. boat and Alum keel with the new fabrication getting heat treated to alloy grade.
     

  7. gonzo
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    gonzo Senior Member

    You can make an aluminum box keel and set the lead in with epoxy or other adhesive. A welded keel can reinforce the keel attachment area.
     
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