Boat Keel

[gnaumovich]

Hello,

I have a 1974 Pearson 10M (33 ft) with a 5'11" draft. I was wondering about cutting down the keel and putting on a bulb so I can get up the North East River. I would ideally enjoy putting her on a dock so the family can easily access the boat. I know that MarsKeel has a program that can design the correct amount of weight to place the bulb to balance the weight of the sails however I was curious...does anyone know what the maximum amount of keel I can remove without really hampering the performance of the boat?

Thank you

-George

 

[tommays]

Its really a Naval architecture issue as somebody has to know enough to ensure the keel sump is up the added leverage of the bulb


Zzzoom 1970 C&C 35 had a few keels done by a Naval architect and there were still some long term issues with the mast trying to punch a hole though the hull were the keel use to be

 

[Cool Beans]

You can figure it out if you know the righting moment and sail area, and some basic hull measurements. I personally wouldn't make any keel mods though even if the numbers say it will work. Your deep keel doesn't just affect heeling but also your ability to point. . .

It is fun to run the numbers just to see, but do consult with a naval architect before doing anything like this. . .

And, if you had to hang another 1000 pounds of ballast under the boat to get it to sail "right", that is 1000 pounds less cargo you can carry

 

[Cayennita]

Since you know how far up the keel you want to cut, you can calculate the volume, thus the weight of the section. This weight has to be then added further up. The bulb concept will not help as much as a wing concept. The wings help to keep the boat from side slipping. Similar to the Hunter legend series such as the 35.5.
It is true that the ability to go to windward is directly proportional to the draft. you'll need a naval architect to help you with the design. One thing to remember is that you will alter the angle at which the boat will not return from a severe knockdown. Be careful because of the liability issues with passengers on board. Read about the 2011 Chicago-Mac incident. I was on one of the boats that stopped racing to look for the crew. This year that design is not allowed and the righting angle value has increased.

 

[JohnShannon]

Expensive, for the same money I bet you could buy an entire boat with the correct draft.

 

[RichH]

The 10M has an encapsulated cast iron keel .... going to be VERY difficult to 'cut' one or remove it from its encapsulation (cement and iron 'punchings'). Once you do this any resale value of the boat will be approaching .... zilch.

Probably would be better to sell the boat and buy one with an external lead keel and simply change/swap (Mars, etc.) the keel to exactly what you want/need. .... OR move to deeper water such as the Sassafrass, HdGrace, Bohemia (actively shoaling in).