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Old 07-12-2014, 10:07   #1
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Shoal Draft v. Full Depth Keel

I have been looking at new boats and am wondering what the advantages/disadvantages are with shoal draft keels. Beyond the obvious draft difference what are the pros cons?


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Old 07-12-2014, 10:17   #2
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Re: Shoal draft v. Full depth keel.

Shoal draft might loose a little pointing ability which would show up if you are racing around the cans. Otherwise I don't think you could tell from just sailing the yacht.

You used the plural "keels" now they have real advantages and you can park the anywhere. One day all yachts will be built this way, once people stop buying Hunters that is.
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Old 07-12-2014, 10:22   #3
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Re: Shoal draft v. Full depth keel.

Generally better performance to windward with a deeper keel.

The deepest keel that still allows access to the waters you wish to sail could be a benchmafk for boat selection.
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Old 07-12-2014, 10:25   #4
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Re: Shoal draft v. Full depth keel.

Yep windward ability. With a caveat though: a heavily loaded cruising boat may not go to weather that well anyway. Most cruisiers avoid going directly to weather as much as possible.... the problem is; if there is any wind you can sail to weather, but the seas pound and try to stop you! If the wind is light and the seas flat... the boat wont move!
I motorsailed to weather a lot.. there are always batteries to charge and water to make!
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Old 07-12-2014, 15:58   #5
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Re: Shoal Draft v. Full Depth Keel

Windward ability and some several hundred more kg of boat weight (on the ballast) to compensate draft.

You will note the difference sailing upwind even cruising. To have an idea of the very considerable loss in performance go the a PHRF list and see the difference of rating between the same boat with deep draft and swallow draft, a considerable one.
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Old 07-12-2014, 16:23   #6
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Re: Shoal draft v. Full depth keel.

Quote:
Originally Posted by Pete7 View Post
Shoal draft might loose a little pointing ability which would show up if you are racing around the cans. Otherwise I don't think you could tell from just sailing the yacht.

You used the plural "keels" now they have real advantages and you can park the anywhere. One day all yachts will be built this way, once people stop buying Hunters that is.
That's funny. Those keels presume a tidal variance of more than 2 feet.

Of course, Brits have funny tastes in food also.
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Old 07-12-2014, 16:31   #7
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Re: Shoal Draft v. Full Depth Keel

I fell pretty sure Hunter made a "bilge keel" at least 356, maybe others?
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Old 07-12-2014, 16:33   #8
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Re: Shoal draft v. Full depth keel.

Quote:
Originally Posted by Pete7;1694814....
You used the plural "keels" now they have real advantages and you can park the anywhere. One day all yachts will be built this way, once people stop buying Hunters that is.
British Hunters had two keels

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Old 07-12-2014, 16:50   #9
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Re: Shoal draft v. Full depth keel.

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....

Of course, Brits have funny tastes in food also.
Not comparable with the French in what regards elegance: just look at those stubby legs on the Hunter and compare them with elegant French legs

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Old 08-12-2014, 04:34   #10
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Re: Shoal Draft v. Full Depth Keel

Greetings and welcome aboard the CF, PsychoPatH.
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Old 08-12-2014, 05:40   #11
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Re: Shoal draft v. Full depth keel.

Quote:
Originally Posted by Pete7 View Post
Shoal draft might loose a little pointing ability which would show up if you are racing around the cans. Otherwise I don't think you could tell from just sailing the yacht.

You used the plural "keels" now they have real advantages and you can park the anywhere. One day all yachts will be built this way, once people stop buying Hunters that is.

Shoal draft you'll lose a lot of pointing ability.

And if you're willing to give that up, then you ought to at least get the huge advantages of bilge keels, like on Pete's boat, at least, if you sail in tidal waters. How cool is being able to dry out anywhere, any time. You don't worry about running aground, and you will hardly ever have to pay for a lift anymore. I would love to have a bilge keel boat! It would open up huge cruising areas in tidal places like here.

The idea of bilge keels goes really well with the idea of a motor-sailer -- in both cases, you trade being able to go to windward much under sail in exchange for other abilities.

How about a pilothouse ketch with bilge keels, a super-reinforced rudder, a really big engine, and vast fuel tankage? Say, a ketch-rig Nauticat with bilge keels -- something like that. Or maybe even make it with twin propulsion engines, with one shaft behind each keel -- how about that?

As far as I know, no one has ever made such a thing -- but it would be a fantastic vessel for high latitude, tidal places, like the Channel and North Sea. I can imagine wanting something for that for my retirement years -- after I finally get tired, once and for all, of bashing to windward under sail.
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Old 08-12-2014, 06:12   #12
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Re: Shoal Draft v. Full Depth Keel

Shallow draft can go into shallow waters. It may also beach easier. It may also sail better upwind vs. an identical hull with a finer, deeper foil.

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Old 08-12-2014, 06:35   #13
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Re: Shoal draft v. Full depth keel.

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Originally Posted by Dockhead View Post
Shoal draft you'll lose a lot of pointing ability.

And if you're willing to give that up, then you ought to at least get the huge advantages of bilge keels, like on Pete's boat, at least, if you sail in tidal waters. How cool is being able to dry out anywhere, any time. You don't worry about running aground, and you will hardly ever have to pay for a lift anymore. I would love to have a bilge keel boat! It would open up huge cruising areas in tidal places like here.

The idea of bilge keels goes really well with the idea of a motor-sailer -- in both cases, you trade being able to go to windward much under sail in exchange for other abilities.

How about a pilothouse ketch with bilge keels, a super-reinforced rudder, a really big engine, and vast fuel tankage? Say, a ketch-rig Nauticat with bilge keels -- something like that. Or maybe even make it with twin propulsion engines, with one shaft behind each keel -- how about that?

As far as I know, no one has ever made such a thing -- but it would be a fantastic vessel for high latitude, tidal places, like the Channel and North Sea. I can imagine wanting something for that for my retirement years -- after I finally get tired, once and for all, of bashing to windward under sail.
A twin keel system means not necessarily a bad upwind performance (small draft does). On RM (the blue boat that I posted above) they purpose the boats with twin keels and single keels and with their NA, Marc Lombard, they performed a lot of studies, on computer an on the water, to know what were the real differences between a really well designed twin keel and a slightly bigger draft torpedo keel.

Off course, the torpedo keel performed better but the difference would be negligible for most cruisers (I posted about that with the real numbers elsewhere). That's why the vast majority of RM clients (and they are many) prefer the twin keels, even on a sportive performance cruiser. Lots of advantages for some small loss.

Regarding a true blue-water boat for high latitude cruising, Pierre Delion /Pierre Rolland designed one, the Iroise 46. It is a fast boat in all points of sail, including upwind. not properly a motor sailor but the 50hp of the engine should be more than enough to the 9000kg of displacement and if not a 75hp would not be a problem.





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Old 08-12-2014, 06:35   #14
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Re: Shoal Draft v. Full Depth Keel

For cruising, not a lot to lose by going shallow draft. (bilge keels or not)
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Old 08-12-2014, 07:18   #15
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Re: Shoal Draft v. Full Depth Keel

Whether you will lose a lot of windward ability, or only a little, depends entirely on the particular boat, as well has how you have it loaded, not to mention how aggressively you sail it in the first place. If you do look at the PHRF numbers you will see that in some cases you lose a significant amount, and in other cases practically nothing.

If you are worried about performance, and like to squeeze the last possible knot out of your sail trim, then you will be much happier with a deeper draft. If you are a more casual and laid-back type then there is a very good possibility that you would never notice the difference. It really depends on you and your particular boat.

Of course, if you want to sail in the Bahamas, on the west coast of Florida, or anywhere else that a deep draft can severely limit where you can go, then the decision is pretty much already made for you.
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