Replacing Encapsulated Keel with Bolt On Keel

The only time simple things make a difference... "Many times the simple things greatly improve performance." is when they were bad to start....

"Like cleaning the bottom"..... please!


Like everything else, performance IS power versus drag... it's no complicated for other craft.....

You add non-linear hull drag i.e. wave drag and suddenly magical "hull speed"...

 

By itself, "performance" can be interpreted many ways, certainly. In sailboat design, in my mind, improved performance means better boat speed, better speed made good to windward (VMG) and better pointing ability. These are all interdependent, but they are three measurable quantities that determine sailboat performance.

This is all INSHORE performance , great for fun in front of the yachty club BUT

offshore performance will include climbing up 15 waves which requires POWER.

Tiny sheet angles and all the rest of the buoy boats tricks fail when POWER is required.

Loads of sail, wider sheeting angles are needed.

ADM Lord Nelsons fleet needed 90 deg tacks to get to windward , and in heavy weather or large seas , so does the modern cruiser.
One can not climb 15 ft waves with a 15T boat , and tack on 65 deg.

FF

 

Correct observation FRED.. I never...NEVER.... go upwind offshore. Only a crazy man would. Upwind abilty is valued inshore...when to enjoy the day you must slip upwind thru an island archipego. Its a mistake to orient a sailing yacht toward upwind performance.

 

Do you want to restate or rephrase your last comments, before I call you an experienced clod, Michael?

 

Its simply not necessary to address your thoughts PAR... they come in very short sentences and reveal nothing of your experience. Even your vocabulary is lacking

 

Gentlemen,

We are talking about keel design here, and how it relates to sailing yacht performance, which is what FirstLight's original inquiry is about. The question was how to do a new keel design and how much analysis is involved. No one said anything about sailing offshore. Certainly, there are factors to consider when sailing offshore, and the thought of sailing upwind into 15' waves does not appeal to me. However, there are times when sailing upwind in strong winds is necessary, and so you'd like to think that your boat can handle that. In those situations, much more comes into play than just keel design.

Eric

 

Sure Eric...and Id imagine that every yacht coming out of your studio has good all round..and good upwind, performance. This is what makes a professionally designed yacht.
When Im crossing an ocean and upwind becomes a necessity...40 to 45degrees awa is all the yacht, its sails, its rigging and its crews stomach can withstand.
I have yet to meet a customer seeking a great cruising boat, who valued upwind performance over reduced draft for actually using and exploring with their boat. Never.
If they insist on superior upwind performance ,Id recommend taking them on a strapped in, dead upwind, 100 mile ocean beat.. on a regatta yacht....then asking them once again.

 

I'm not sure what your problem is Michael, but I suspect it's that you read a lot of Sail and WoodenBoat magazines, but haven't really a clue as to the realities of sailing or building or design. You make comments in direct contradiction to your own previous comments, you continuously show a real lack of understanding, and frankly until direct attack, I thought it was a translation issue, but clearly you are clueless.

Your posts often, adding nothing to a thread, but at times you've shown some understanding, such as one of your latest comments on a CPP thread, but then just to follow it up with ridiculousness in other threads like the comments here. I don't know what your life is, but it does seem to an arm chair quarterback approach, one with lots of supposition, but based in nothing substantial.

Well just sit on your log and hold up your shirt man, the wind will blow you some place . . .

Yep, right on the mainstream pulse there big guy . . . you're so in touch . . .

Yea, man you're on to something here, you should consider a news conference or something.

I asked if you wanted to rephrase or at least recant. A simple justification or at least a rationalization of your comments would have sufficed. Then again, maybe I'm wrong and all of us designing ocean going yachts, should have our respective heads examined, because you've discovered this "windward bugaboo" in the market. Of course, we'll assume you have the appropriate research to substantiate your claims . . .

If you're this afraid then why bother releasing the dock lines?

 

Where we are.

In writing the original post I was mostly referring to two things:

1. Ability to achieve higher than 55 degrees COG. Pointing ability is significantly higher than this however the leeway of the boat pushed the COG down substantially.

2. The overall feel of the boat. While she is tender she also tracks quite poorly on a broad reach and her motion through the water is quick versus steady. For instance, this past week we took the boat offshore and were motorsailing in 25 knots of breeze at approximately 75 TWA with 3-4' chop with an 8 second frequency. The boat felt like a 25 footer (with a 40' waterline). I've been in identical conditions on a friends 42 Westasail (full keel) and it felt MUCH better.

I completely understand that a deeper keel will change the moment of intertia and improve these sailing characteristics.

Our plan is to take the boat to the Bahamas this winter (enjoy the 5'2" draft) and then look at upgrading the keel.

Our goal will be to address the motion and tracking of the boat versus the COG. She is a crusing boat and her ketch rig will never be a great upwind performer. I'm ok with this.

The question is how does one upgrade an encapsulated keel? Cut it off and bolt on an addition to the existing keel? We'd like to keep her weight near her exiting weight of 28,000 lbs which lets her sail quite well in lighter conditions.

We'd love to add a centerboard i possible but cutting in the trunk seems like a monumental task. Although we've seen people try this with chainsaws and reciprocating circular saws...

 

Attaching a 'shoe' on to the bottom of the keel would
be a very feasible solution. My boat, which has an encapsulated keel,
has a 1' extension which is molded to the foil shape of the keel and
lag bolted on.
Replacing the entire keel with a 'bolt on' would entail rebuilding
the entire structure of the bilge.
It would make much more sense to start over with
a boat that meets your requirements.

 

FirstLight,

In order to change the keel with proper engineering and accuracy, you will need to have the boat surveyed by a naval architect. He will take measurements of the existing keel and inside structure as well as the rig. He will take pictures, lots of them. He will make an assessment of how much new structure will be needed to build onto the boat to fasten on a new bolt-on keel. He will also have to assess where the center of the rig is in relation to the keel so that when the new keel goes back on, the weather helm will be the same or improved. In fact, it would be most worthwhile for the naval architect to go sailing with you first, to do some tacking angles in a given wind speed so that he has some measure of existing performance so that he has something to compare to when the new keel goes on.

The new keel will have to be designed to have a bolting structure that is compatible with your boat, and the naval architect will specify all that boat modification work. He will design the new keel according to your draft and performance requirements so that the keel fits into the new rebuilt bottom hull structure that will also have to be designed.

If you want a centerboard, that is a whole additional matter because you have to design the centerboard blade appropriately, and its lifting mechanism, and make sure there is a convenient place in the boat to install it all. The keel would be designed accordingly with an appropriate hollow recess molded into the keel to house the centerboard. The centerboard will have to be designed, built and installed into the keel. The hull structure would be modified accordingly to account for the lifting pennant and its watertight housing.

Finally, the naval architect will make an assessment of your rig. A new keel at a significantly deeper draft will add righting moment to your boat. This will stress the rig higher, so a check has to be made of the size of the mast and the rigging. If it becomes undersized because of the addition of the new keel, then the rig may have to be changed--larger diameter standing rigging wires, new mast perhaps, maybe even new chainplates.

Current prices of lead, molded, are running about $2.25 a pound or a little higher. So if you have a 10,000 lbs keel, say, for your 40', 28,000 lb boat, you are looking at at least $22,500 for the casting. Add in another $10,000 to $12,000 to make the patterns, the mold, the keel bolts, and the exterior finish. So just for the keel, that's $32,500 to $34,500. On top of that you have to include the naval architect's design fee and expenses. My basic keel designs start at about $4,000, so add to that the design for the hull structure, and the travel time and expenses, and you are breaking over $10,000 at least for the design. Add in the cost of the centerboard, and that's probably another $2,000 to $4,000 for the design, plus at least that, may double that amount depending on how you build it, for the board itself. So, complete, you could be into the project for $48,000 to $56,000, and that is if your rig does NOT need any changes.

That should give you a rough idea of the costs. Can be done, but is it worth it? Only you can make that assessment.

Good luck.

Eric