Fin Keel vs. Full Keel

[Dick Pluta]

PS for Hiracer. I just re-read your post and want to clarify. I agree 100% with what you said. I just didn't attribute my boats windward ability to the keel. Actually, maybe I did. She really doesn't go very well to windward but she's magnificent at sundown in a quiet cove.

Dick

[keelbolts]

I should probably point out that my opinions on fin keeled boats are not based on my Westerly. She's all about useable volume and sitting upright when the water goes away and, at those things, she really delivers. She's a Giles design, but nobody could cram standup headroom and all the creature comforts she has into a 23' sailboat & come up with speed, windward ability, and ravishing beauty. Until the wind is honkin', she's something of a slug, but I love her for what she is. I base my opinions of fin keeled boats on those that many of my friends have and a J29 I raced on for a season or two.

While I've also sailed on several of my friends' full keeled boats, I've done most of my full keeled sailing on Favona and L'orien, an Anker-Jensen 10 meter. Perhaps those boats have distorted my view of things somewhat. Favona won the Fastnet Race and I was once on L'Orien when she blew by a local race like they were anchored. They were going downwind with their 'chutes up, we had our main and a jib, and we blew by them so fast a committee boat came over just to see what we were sailing.

Mr. Perry, you might find it interesting that Favona is a Robert Clark design. Clark was a proponent of the Metacentric Shelf theory of design. I gather modern designers sort of poo poo MS theory, but I also gather that it never produced a boat that wasn't well balanced and sweet. I guess I've been lucky enough to have been spoiled by the boats I've sailed.

[Hiracer]

Originally Posted by Dick Pluta

The Islander, with it's attached rudder, was the right boat at that moment.

Bullseye.

'Performance' for cruising purposes is more than just about speed, which is to be distinguished from racing. For cruising applications, a full keel has a lot going for it, even it a little something is given up to the windward. It is the total package that counts.

I've been complaining for some time that I think the industry has made a wrong turn with its obssession with 'racer/cruisers.' Too much cruising 'performance' is given up by that genre. If the cruise ain't fun and comfortable, who cares if you're going a 1/2 knot faster. I guess not everybody agrees with me--yet; give'm a couple of decades, they'll get there.

[TAREUA]

There are some interesting points here, I think. My own experience cruising (more ocean crossing than harbor hopping) on a fin keel boat had me wanting among other things a full (or modified full) keel boat. This was based on about 4 different boats I sailed on that were modified (except for a Banjer) full keels. Those boats ‘directional stability’ were so much better than all the many fin keel boats I had sailed on that the advantage for long distance passage making seemed like something I really wanted for my next boat. Underwater hull shape excluding the keel didn’t enter much into my thinking. I can see how that could be a big mistake. However I would still judge from my own experience on many boats that full keel boats tracking so effortlessly is more than a coincidence. To be fair the great majority of fin keel boats I’ve sailed were racing boats and speed performance was the goal not directional stability. The idea that there are fin keel boats that have great windward ability and can move across the water like they are on rails doesn’t surprise me. If my lottery number comes in I would call Mr. Perry and put him to work on something just like that. Based on my limited budget however, and the fact I don’t buy lotto tickets; a full keel used boat was a safe way to get the performance attributes I was after.

I had a 30 foot boat with a short stick and a long boom, which was great for cruising because a reef in the main made a quick fix to an unruly boat, but that is the opposite of what I’d want on a racing boat, and the opposite of what a lot people seem to want period. I also wanted a center cockpit, which along with the full keel, is a disadvantage going to weather, but I have no interest in spending most of my cruising time going into the wind. As you guys have said, it is a collection of things that work to get you the boat you want, or should, based on what you want to do with it. So trade wind passage making for me meant, full keel, center cockpit, and ketch rig.

[bob perry]

Clark's Metacentric Shelf Theory:
Yes I am aquainted with that if not familiar with it.
But that was well over 50 years ago and I have my own opinion on why his boat's were sweet sailors and it does not involve the MST.

Most of us in the yacht design busines have moved on from the MST.
My ICON and AMATI are as different from Clark designs as physically possible but both are very sweet sailing, well balanced and forgiving boats to sail. Time marches on.

I think it is very clear here that some of you have permanent ideas on design.
That is fine for you. But in my postion I must keep an open mind.
VMG is not open to opinion, upwind or down.
Comfort can be open to opinion as can be sailing styles.
I have designed as wide a range of sailing yachts as any other designer, maybe with the exception of Nigel Irons, so I have no dog in this fight other than accuracy.

[keelbolts]

I think, that even in Clark's time, there were those that didn't buy MS theory. I remember reading that it wasn't any good since it was figured on a static hull and was irrelevant once the boat was in motion. I can't say.

I guess I need to recognize that when I'm saying "full keel" not only is it a modified full keel, but I'm also thinking of a wine glass hull shape of narrow beam. I have seen some boats, a Rhodes comes to mind, that had, what I think of as a fin keeled bottom, except it a relatively thin full keel bolted to the round bottom. I never sailed it so I don't can't comment on what it would do.

I haven't meant to offend anybody here or stir things up. I swear I thought that a modified full keel's superiority to windward was common knowledge. I thought there was room for comparisons of turning radius, downwind speed, of agility, but not of windward ability.

Also, remember that the original question dealt with the search for a cruising boat and, even if I was convinced of the fin keel's windward superiority, I'd recommend a modified full keel w/ an attached rudder and a tiller.

I know many of you will be surprised to find that I am something of a luddite in other matters as well.

[bob perry]

Keel:
If there is any area here where there is no room for argument at all it is in the fact that fin keels are superior upwind to full keels. If you and I cannot agree to that then we have lost any common vocabulary to discuss yacht design.

Maybe I should just go fishing again. But I have some work to do on a 43' full keel motor sailer.

[TAREUA]

I better go buy that lottery ticket at lunch then.

[Cheechako]

I love those Freeport 41's, never had one, but admired many......going to windward (which means my planning was poor!) has always been a motorsail no matter what I've owned anyway!

[Hiracer]

Originally Posted by keelbolts

I haven't meant to offend anybody here or stir things up.

Please don't think for a second that you have offended anybody. You haven't. Some of us, me in particular, love to mix it up about sailboat design, largely because that's how I go about learning the subject. I've been making Mr. Perry educate me here for some time now. I have never taken offense at the fact that somebody has a different idea or opinion, even though sometimes I'm a bit vociferous with my opinions and thoughts. By pressing people about the 'whys' of their opinions I can sometimes divine a new angle and learn something.

FWIW, I very nearly purchased a 36' designed by an Englishman whose name escapes me right now that was similar to your Favona. I've always had a soft spot for that narrow hull, wine glass form, with truncated keel that approaches the shape of a long fin keel. Modern designers may scoff at the attached rudder and say it doesn't work very well for spinnaker work, but I see a solid form for cruising purposes with enough speed to get the job done. Certainly a design that I would prefer over, say, an Island Packet, to use an extreme example. I apologize if anybody here has an Island Packet, but really that's not my kind of hull shape. To far at one end of the spectrum. Having said that, I don't think Favona would be competative in today's Fastnet against the top boats because she doesn't have a deep, high aspect fin keel. Just guessing, of course, because I've never sailed her; but I do think that as a cruiser she would superior to many of the boats that would beat her to windward in today's Fastnet. Further, she's a damn sight prettier than most.

[keelbolts]

Mr. Perry, please don't be in any way offended by any of what I've said. I feel a bit like I'm arguing flight characteristics with the Wright Brothers. I do think that we have a language problem in that, lift on a wing and lift on a keel aren't the same thing and I was thinking aircraft. Also, I said full keel when I should have said modified full keel.

To tell me that a fin keel is better than a modified full keel to windward effects my brain in the same way it would if you said a Volkswagen is faster than a Ferrari. Even if it was true it would take a while to fully register.

HiRacer, it's funny that you bring up the Fastnet. I agree that she wouldn't be competitive today, but it reminded me of something from the '79 Fastnet. One if the competitors was an old boat that had been a much earlier winner. I don't remember which boat. Anyway, while the crews of the cutting edge racers were fighting for their lives, her crew hove to and went below to wait out the storm. Food for thought if you're planning on going bluewater.

[bob perry]

Keel:
I'm not offended at all. Just amazed that you still believe a "modified full keel" is faster to weather than a fin keel. Keels are like wings ( think the wings on a glider). Keels need aspect ratio in order to be efficient. In short it's all about leading edge and aspect ratio. When designers with experience sit down to talk design there is no argument on this. We all strive for aspect ratio and we often resort to "tricks" in order to get additional "apparent aspect ratio" out of a fin. But in the end it's all about aspect ratio. Any full, fullish or modified full keel lacks aspect ratio more than anything else. Most do not even have foil shaped waterlines. They have clumsy leading edges and crude trailing edges. They are far from the NACA derived foils most of use today so we can have some asurance of the stall, lift and drag characteristics of the keels we design. In fact, lift on a keel and lift on a wing ARE the same thing, i.e. foils with an angle of attack that produces lift.

I could suggest some very good books if you are interested in learning more.
Start with mine, YACHT DESIGN ACCORDING TO PERRY. There is a good chapter on keels. Steve Killing also has an excellant book YACHT DESIGN EXPLAINED.

[gbanker]

how can you trust what Robert Perry says? Didn't he design all those canoe stern boats that were just a design fad and cramped the storage in the cockpit area? Just kidding, I agree with your comment about fin vs full keel Bob.

[keelbolts]

Still trying to learn - not simply arguing.

You state that a keel and a wing function in the same way.
one question, one observation:

Question: does a keel create lift without leeway?

Observation: no aircraft could fly with wings whose tops matched their bottoms.

[Hiracer]

Originally Posted by keelbolts

Question: does a keel create lift without leeway?

Does a sailboat ever sail without leeway? If not, why ask the question?

While it's true that keels and airplane wings operate in different contexts, (a keel is a wing that must produce lift on both sides unlike an airplane wing) how does that translate into making aspect irrelevent?