keel modification

[steve34609]

I am considering a professional keel modification on a 45 foot aft cockpit SV. She has a cast iron keel, bolted on. Total displacement is roughly 25,500 lbs with roughly 10500 lbs of ballast. It's a full keel with a little over 6 feet of draft. I've found a company that will cast the new 'twin torpedo' end piece. I'm aware of the pros and cons concerning stability, possible loss of re-sale value etc...I want to remove roughly 3000 to 3200 lbs of keel. My question is: how to calculate fairly precisely how much of the keel to remove in order to equal that weight, and how to cut a straight line through cast iron? Any helpful suggestions?

 

[Prime Time]

I would talk to a naval architect. As it stands now your ballast is less than 50% of displacement. By changing the depth to a bulb type keel you are changing the center of mass of the boat. You will be more tender. You will need to add more iron to maintain the same righting moment.

 

[Jackdaw]

Your trick will to be to keep the righting moment the same or close. I'd contact Bob Perry. Tell him Jackdaw sent you. He'll either cut you a deal or raise his price, I'm not sure which! ;^)

RHP-BOB@threshinc.com

 

[Bill1565]

I am considering a professional keel modification on a 45 foot aft cockpit SV. She has a cast iron keel, bolted on. Total displacement is roughly 25,500 lbs with roughly 10500 lbs of ballast. It's a full keel with a little over 6 feet of draft. I've found a company that will cast the new 'twin torpedo' end piece. I'm aware of the pros and cons concerning stability, possible loss of re-sale value etc...I want to remove roughly 3000 to 3200 lbs of keel. My question is: how to calculate fairly precisely how much of the keel to remove in order to equal that weight, and how to cut a straight line through cast iron? Any helpful suggestions?

Don't think you will be happy removing weight and draft. You need to ADD weight to compensate for less draft.

 

[Ron20324]

Have you googled your boat to see if there is a different draft model, and maybe give you an idea of the ballast difference?

 

[LloydB]

I found bilge keel on google but not ('twin torpedo' end piece) that made sense to me as a single keel mod. Might there be another name for that or an example of it?

 

[trainmanjess]

hello all

here is a site article about a couple who changed the keel on their boat and added custom made torpedoes on the new keel....

sales@marskeel.com

Mars Keel Technology

sincerely
Jess

 

[Crazy Dave Condon]

Mars had made many keels over the years for many and know how to cast keels. However, a well made point on how will it affect the riding moment and that needs to be considered re. stability. Talk with a naval arechitect first,.

 

[Gunni]

Just because manufacturers are selling boats with <30% ballast to displacement ratios doesn't mean it is a good idea. But hey, in the interest of American ingenuity here is how I would do it:
Find a surveyor with a total-station laser and have her create a 3-D point-file volume calculation and image of the keel. Factor this against the weight and generate weight/volume value. Then have her CAD tech calculate the volume of the keel stub that must be removed. Transfer those measurements to keel and hire some crazy shade tree mechanics with cut-off saws to remove the required stub. You are on your own after that!