what came first the keel or the boat?

[jackason]

Hello

What came first the keel or the boat. Is there another way to ask this question?
Does the Hull design dictate the keel design or keel design dictate hull design. Is it a 50/50 proposition.

Maybe a better way to phrase this...For any given hull design is there only one applicable keel design. Although the sailboat I've started building is only 14' it has a 40" (somewhat retractable)deep keel, see attachment. Is there life after a deep keel? Are twin keels and relocated ballast a option? The hull in question is a shallow/planning hull I plan on a little more shallow water than bluewater cruising initally.



Thanks -Christian

[gggGuest]

Every design is a compromise and balance between lots of competing factors, and there's rarely a single solution. It just depends how your priorities between those factors go.

Looking at that your priorities amd aims are a mile away from mine, an I couldn't even begin to comment...

[the_sphincter]

why not just buy a laser? Throw a tarp on it if you want to sleep.

[jackason]

A Laser? Hhmm, never thought of that...Hell, I do have a old ironing board and a 1/4 roll of Tyvek housewrap in the garage.


-Christian

[the_sphincter]

Sounds like a plan. Now back to the question "is there life after a deep keel?" for performance, no. But going aground is also even worse performance. with a boat that size, the loads are small, and you may be able to devise some type of lifting mechanism (though it'd probably be at the expense of interior room). Don't go with double keels. A single with a nice foil shape and the bulb at the very bottom (or as far as you're going to go with your boat) would probably be your best bet.

[jackason]

sphincter,

Yeah, the plans I have detail a retractable keel held by 4 bolts down at floor level via a reinforced floor flange. It can be lifted via a simple pulley system which is fine, easy enough. The question is how to do it while underway without leakage, that opening can only by so watertight no matter what you do and how to leave it in the upright position while underway while in shallow waters without it leaking.

Here's a Idea I just thought of. I don't care about interior space when it over rides function. I guess I could build I raised/reinforced housing like a sleeve or a slot that is (just) above the waterline, kinda like a centerboard case. I'd have to build the keel a little longer. The keel could bolt the same way but to the top of the base with a neoprene gasket instead of at the floor.

The sleeve/slot It could also serve as a base for a small removable eating/chart tabletop while the keel is down. This might work out well because there is no good spot for a flipdown model hanging on a bulkhead or hull wall. To take it a step further a properly built braced housing would displace some of the keel pressure from a small part of the floor to a wider area I would think.


O.k. back to the ironing board, er drawing board. sorry - bad pun but I couldn't help myself.


-Christian

[Robjl]

Jackason,
Start wih a rough hull shape.
Work out your layout... work out construction..... then you can find to CG.
Now go back to your hull shape design (armed with CG) and see where she will float. CG and CB must be in vertical line. If it's not you will need to adjust the hull shape..but remember there is a recommended relationship between the centre of the waterline length and CB. (Refer any good book on Yacht Design)
Once you have refined your design a bit you can have a look at the "lead". This effects the balance. You need to calculate centre of effort (CE) of the sailplan and the centre of lateral resistance (CLR) of the hull.
Again... any good book will give you some guidelines.
It now becomes a back and forth process of trying changes and checking their effect.
What comes first?? ... doesn't matter so long as it all works together so that the boat floats level on her waterline and the balance is right so that she sails well.
Good Luck.
Rob.

[sharpii2]

Originally Posted by jackason

Hello

What came first the keel or the boat. Is there another way to ask this question?
Does the Hull design dictate the keel design or keel design dictate hull design. Is it a 50/50 proposition.

Maybe a better way to phrase this...For any given hull design is there only one applicable keel design. Although the sailboat I've started building is only 14' it has a 40" (somewhat retractable)deep keel, see attachment. Is there life after a deep keel? Are twin keels and relocated ballast a option? The hull in question is a shallow/planning hull I plan on a little more shallow water than bluewater cruising initally.

Thanks -Christian

The shallower you go, the more ballast you need to get the same righting moment. Or the less sail area you can carry.

My own design concept had to have its sail area cropped by over 20% (180sf to 140sf) in order to get rid of enough ballast to have a decent carrying capacity.

It seems that in this case, the deep keel bulb is central to the design concept, so changing it to a shallower, heavier one will probably not work. It will force you to either shorten the sail area or make the boat so much heavier that it will not perform like it would otherwise.

Perhaps you should look at a Pelican 16 which is based on the more famous S.F Pelican 12. It has been known to plane also, but gets its sail carrying ability from wide beam and low sail plan rather than deep ballast.

Bob

[h_zwakenberg]

Originally Posted by jackason

Does the Hull design dictate the keel design or keel design dictate hull design. Is it a 50/50 proposition.

Hi Christian,

I suggest you go to the local library and get a book called: "The symmetry of sailing". The book's title might give you a clue, though...

bye
Hans