Keel too deep

pmagowan

pmagowan

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Has anyone ever heard of cutting the bottom off the keel? We draw 7’4” which is a bit of a pain. Boat is 41 ft Sweden Yacht. Was just musing the possibilities of cutting the bottom off and bolting on a ‘bulb’ of some type. Thoughts?
 
It's unlikely that the keel bolts will go right down to the bottom of the keel, but into galleries located higher up.

So, in theory, you could slice off the bottom 24 inches (but it's going to need some awfully industrial machinery) and then put on a hydrodynamic shape (again, lots of clever industrial welding) and casting a one-off shape (expensive). Calcs needed to preserve the CofG of the keel.

Does the original boat maker offer a choice of keels ? Perhaps they may have a variant on the deep fin sitting around the yard ?
 
I presume if it is a Sweden Yacht the keel is lead? Might be more practical to cast a new one but you will still need at least 2m. for a boat like that. Hard to see a practical difference between that and 2.5m. and you will lose a fair bit of the hydrodynamic leverage of a longer wing.
Where could you go with a 2m. keel that you would not go with a 2.5m. one (the only place I can think of is a transit of the Crinan Canal) but then I sail in Scotland where you worry if the depth goes below 5m.
 
Keel depth and weight has different sizes for the weight of the boat for a reason, to cut down heeling. Cut it shorter and expect to heel more, also most boats go slower when heeled more than about 15 degrees. I expect cutting off the bottom of the keel and fitting a bulb would cost serious money.
 
pmagowan said:
Has anyone ever heard of cutting the bottom off the keel? We draw 7’4” which is a bit of a pain. Boat is 41 ft Sweden Yacht. Was just musing the possibilities of cutting the bottom off and bolting on a ‘bulb’ of some type. Thoughts?
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Have you contacted Sweden Yachts and discussed this with their marine architect?
 
If your keel is lead, then you may not be able to cut it down. Many thin lead keels have the keel bolts as part of a massive cage that is cast into the keel to stop the lead from bending. I would expect that with your keel.

Personally I would not alter the keel. At a pinch you could change the keel with advice from Sweden Yachts, but would be expensive. Your cheapest option would be to change your boat if it was that much of a problem.
 
We just spent 3months cruising the Bahamas ( super shallow) with a 2.2m draft. Inconvenient at times but very happy with the deep draft when we are out in the ocean. I wouldnt change anything
 
pmagowan said:
Has anyone ever heard of cutting the bottom off the keel? We draw 7’4” which is a bit of a pain. Boat is 41 ft Sweden Yacht. Was just musing the possibilities of cutting the bottom off and bolting on a ‘bulb’ of some type. Thoughts?
Click to expand...

Well-----you did ask so------I think it is an absolutely bonkers idea.;)
 
There was a recent article in the American magazine God Old Boat on this precise topic. The costs were pretty horrendous, and there were no benefits -apart from the draft reduction. The boat was less stiff did not point as high etc etc.
A good way to devalue a nice boat.
 
pmagowan said:
Has anyone ever heard of cutting the bottom off the keel? We draw 7’4” which is a bit of a pain. Boat is 41 ft Sweden Yacht. Was just musing the possibilities of cutting the bottom off and bolting on a ‘bulb’ of some type. Thoughts?
Click to expand...

We did several modifications of that type to our former racing yacht, an IOR 2nd class so very similar size.
The formula took into consideration both righting moment and draft, so to optimize rating one was tempted to do all sorts of modifications, especially as righting moment was relatively penalized.
First we took off a section of keel, sliced it at about 30-40 from the tip: reduction in righting moment, reduction in draft. New rating and testing not satisfactory.
Then we replaced the chunk with a piece of hardwood, bringing it back to the former draft (good for better pointing), roughly the same RM.
Eventually, we fine trimmed the RM by adding some lead ingots in the bilge.
The boat sailed 30-40k miles with no keel problems, it hit its share of underwater rocks we just had to do some cosmetics on the hardwood tip.

I was tempetd to do the same modification as you (that is, cutting and adding a bulb, two halves on the side of the remaining keel, then I had to give priority to other things; at that time I investigated and there was an US shipyard that had developed an interesting method, sorry I:have lost the reference they might still be there (?)
 
Not heard much recently about those Warwick (?) winged keels with two fins and a big aerodynamic end plate. Might be worth a look. Lowered the draft but kept the windward ability. Plus, the boat could sit on it.

Knut, just looked at your link. Interesting that an outfit offers a range of bolt on bits, so there must be a market.
 
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Ha ha thanks for all the advice. It was not a well developed idea I was simply pondering. It was launch day today and I was worried I wouldn’t get enough tide to float her off the trailer. I suspect the idea is a bit mad and I will live with a quicker bump
 
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