Keel Modification: Increase stability

[chrisr]

Originally Posted by Fore and Aft

Chrisr I hear what you're saying. I can remember working in one boatyard where the owner was making some wild keel modifications. In the end the boss asked the owner to truck the yacht out of the yard. Even though we were not doing the work, just the stigma of having a keel fall of from a boat that had been in our yard was enough to get him booted out.
Cheers

yep, so true

we modified the keel of a mumm 36 i had, by adding 200kg shoe to the bottom. this was at noakes in sydney and we had to do a lot of talking with sean before he would agree.

it helped that a sister boat had been modified the same way a year or so earlier.

cheers,

[malbert73]

Originally Posted by jtsailjt

I think that removing material above the keel bolts is very doable with little to no effect on structural integrity. Additionally, I think you could drill a series of 1” holes through the keel below the keel bolts to further lighten the top 2/3 of the keel. Of course all these holes would be filled and faired. Many lightweight materials that could be used to fill the voids are quite strong in compression so any loss in structural integrity would be very minimal.

“I think” so also. And, I’d be wanting a NA to sign off given the stakes… there’s a lot of loading at the keel root, in many directions, with significant margins needed (hit a rock at 6 knots)

[Capt Ben]

... AGREED, and that is why I engaged the designers of the boat to do just that. Initial posting....

Originally Posted by malbert73

“I think” so also. And, I’d be wanting a NA to sign off given the stakes… there’s a lot of loading at the keel root, in many directions, with significant margins needed (hit a rock at 6 knots)

[Lee Jerry]

Capt Ben,

A couple of questions:

Did you price out having your current keel melted down and re-cast into a new shape with bulb? Would likely cost more, but since you would be providing all of the material maybe not as much as many might expect (especially if you include the cost of the cutting, filling and fairing of the holes), and I think you would get a "better" final result. I'm sure Farr could design that keel for you as well. Might want to at least ask for comparison.

In your modification, it looks like the CG of the 4000+ lb keel is moving a couple of inches aft. Has the affect on trim been considered? (Doing above might minimize or eliminate this concern.)