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post #71 of 847 Old 03-06-2012
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Re: Full or fin keel?

The first large (42') fiberglass cruising sailboat was called Arion. Designed in 1950 by Sidney Herreschoff she had both a fin keel and a spade rudder. She is still sailing. damian mclaughlin corporation - Arethusa

It is not that new an idea and well proven.
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post #72 of 847 Old 03-06-2012
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Re: Full or fin keel?

utchuckd,
So there; see what I meant when I said "if you can decide in your own head" full vs fin keels?
There really is now way to simplify this decision but to think hard about the kind of sailing you are going to do and where you are likely to do it and then mentally start building the boat of your dreams. Then comes the hard part of finding that boat without having to commission a naval architect.
And then you come to uderstand that saying "every boat is a compromise."
I think very very few people ever got their last boat with their first boat. So don't kill yourself trying to find that perfect boat right out of the box.
Have fun with this journey.
John
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post #73 of 847 Old 03-06-2012
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Re: Full or fin keel?

Arion is a very pretty boat. I imagine a modern version of that would sell a few copies.

Back home on Lake Ontario after something over 36,000 nm circumnavigator. Not surprisingly there is a lot of stuff I want to get done on Ainia both cosmetically and functionally. Getting an early start so it will be ready to go for next summer (Lake Superior?).
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post #74 of 847 Old 03-06-2012
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Re: Full or fin keel?

that's a nice sailboat...thanks for posting MiTiemp...My own boat has an 8 foot beam too...but she's only 29-feet long ! This is interesting...Perhaps alot more 40-foot+ boats would be speedsters like this one if folks didn't have that understandably strong desire for roominess....that canoe stern helps her get out of her own way too though....

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post #75 of 847 Old 03-06-2012
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Re: Full or fin keel?

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Originally Posted by sea_hunter View Post
Fin Keels have nothing to do with seaworthiness; they're about speed/production costs = profits. Do a "loses keel" on Google. Check out the images too.
The single keel on my 36 footer has over 4.6 million pounds of tensile strength in the steel supporting them. Not much chance of that breaking. Keel loses are on high aspect ratio , minimum design racing boats , not on longish fin keels, common on cruising boats.

Brent Swain, Boat designer, Builder, and author of "Origami Metal Boatbuilding"
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post #76 of 847 Old 03-12-2012
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Re: Full or fin keel?

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We have been given the opportunity to modify the full keel of a 38 ft Sabre we are in love with to a bulb keel by Mars metal. What would the consequences be? We would be choosing this option because we are very inexperienced sailors looking to learn on our liveaboard. The modification would take 1 1/2 feet off of a 6'6" keel and allow us coastal cruising and maybe a trip south.

Thanks,
newbee
If I were you, I would talk to Sabre. The new Sabres show a wing keel for a shoal. Probably a smaller wing though. Not sure about the year of your boat, but the Sabres appear to be a great example of a typical American cruising design. A lot of keel weight, good solid hull.

No doubt anyone can design a bulb keel to create the same righting moment as your existing keel. Unfortuneately, such a keel only adds drag with no hydrodynamic benefit. You will clearly lose some pointing with the bulb. If you want to do something useful with the bulb mass, reshape it to a wing.

My feelings are that a good wing design needs considerable area to gain some hydrodynamic benefit. The benefit to gain is the same or increasing resistance to leway movement with heeling. And possibly some benefit to resistance to vertical moment.

The problems I see with adding a wing to the bottom of an existing shortened keel deals with vertical forces. Movement of the hull vertically creates large forces on the keel-wing joint.

The wing keel is unique in that it can create large resistance to vertical moment. Like a huge rocker stopper. It resists downward movement (same as the hull). And more interestingly enough, it resists upward movement unlike any other keel design.

Again, I would contact Sabre.
Bryce

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post #77 of 847 Old 03-12-2012
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Re: Full or fin keel?

Quote:
Originally Posted by mitiempo View Post
The first large (42') fiberglass cruising sailboat was called Arion. Designed in 1950 by Sidney Herreschoff she had both a fin keel and a spade rudder. She is still sailing.

It is not that new an idea and well proven.
Boy, it is pretty tough to compare this to newer fin keel boats. This boat only has an 8 foot beam and its 40 feet long. And 50% of its mass is in its keel. And its hull is more V shaped than flat. The keel is longitudinally long rather than vertically long like a newer fin keel.

Because its so narrow and v-shaped, this will have a lot in common with the full keel boats. The full keel boats owe much of there sea handling capabilities to the hull design, not necessarily to the keel design.

I think the Valiant is probably very similar. Its hull design is more v-shaped than flat. This contributes immensely to its sea handling.

But you are quite right, the fin design and even the flat hulls have been around for centries.
Bryce

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post #78 of 847 Old 03-12-2012
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Re: Full or fin keel?

Fin keel or full keel, a boat doesn't have to be fat.

The Valiant of course isn't quite as narrow as Arion. But after almost 40 years it helps prove a full keel isn't necessary for a boat to be "offshore" capable. There are also many others that have traveled far and wide with fin keels.

I can't think of many full keel boats with high efficiency keels - just large ones with a great deal more wetted surface than necessary.

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post #79 of 847 Old 03-12-2012
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Re: Full or fin keel?

With in the matter of a year I went from swing keel (Chrysler 22) to fin keel (Chrysler 26) to modifed full keel (Endeavor 32) is my only claim to knowadge.

The swing keel was great for the lake sailing we did and it being our 1st sailboat made learning what running aground meant with the ease of dealing with it. I could see sailing it on the coast in fairer weather. Also great for getting in and out of the water. we stored it on the hard between outtings with mast up.

The fin keel was on our coastal/sound boat that we sailed long weekends on unfamiliar waters. Great for the rougher larger waters but it didn't stop me from thinking how nice if it was also the swing keel version when we ran aground a few times. Fun all around thou I'm never sure the other boats knew we were racing at times.

Now that we are liveaboard cruisiers the modified full keel meets our needs very well.
With the experiance we gained with the other 2 boats, We have been able to cruise the east coast sailing alot on the outside or even sailing the ICW due to its shallow draft. I guess we have learned how to handle it well enough that I have been able to back it out of tight spaces with out much trouble. I know I don't sail as fast as the fin keel boats but I'm in no hurry and it is my home. I don't think I would like it as much if I was only useing it on weekends and I was out to play.

So me being NO expert can only say that it really depends on what type of sailing you do as to what type of keel is better.
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post #80 of 847 Old 03-12-2012
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Re: Full or fin keel?

This is just my 2 cents and all its worth. I must have missed it but did anyone mention the safety factor of being able to heave to? If you have ever been in a third world boat yard you will appreciate the ease and safety of hauling out a full keel vs a fin keel. A full keel boat can be safely careened for a quickie bottom job, try that with a fin keel. If you haven't seen what happens when a fin keel hits a reef at 6 knots you should come to the Pacific North West and visit any boatyard, its pretty scary. Just a few thoughts
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