Good boats w/ shoal draft keels?

Have any of you sailed a shoal draft monohull that you thought was surprisingly good? By that I mean going upwind well, and not really compromised overall. And I'm thinking about mainstream production sailboats, with the typical keel designs -- simple shallow keels, Scheel keels, wing designs, etc. -- from small daysailors to trailersailors, and larger sailboats too. Which ones have you sailed that were surprisingly good? What do you think made them better than usual?

 

Ive taken a 13 foot catboat upwind against a Rhodes 19 keeled sloop. we could point higher than them and in some cases actually be sailing faster than them. I think it was called a Crosby Fast Cat. This is an old boat, so my reply may very well be completely useless to you, but oh well. Do you consider large centerboarders shoal draft?

 

Here on the Chesapeake, where grounding is part of sailing, center boarders are the preferred trailer sailers. If you hit the bottom, you crank the board up, if that's not enough then go over the side and push. Most of the fixed keel boats produced in both standard and shoal draft will draw four feet standard and 3.5 shoal, at least that ratio. You just get stuck a little closer to the beach but still waist to chest deep. And did you ever notice the resembilance of a wing keel and a Bruce anchor?

 

Back in the mid 1980s the MORC class was booming, giving us great racing for boats under 30 feet. That rule penalized draft. Steve Schock fitted a Tandem Keel to a Wavelength 24, which was a competitive boat in the fleet when using a standard elliptical fin keel. Most of us thought that he would not be able to keep up, even with the credit he received for less draft.

In fact, in the only regatta we sailed against them they actually led or were right in it on every beat. I think they might have been a touch slower downwind, but within the rating. This was a light air regatta.

I was really surprised, and I believe the MORC rule was modified soon after to treat these keels differently.

I think there was also a big deal being made of the patent and license fees, which limited the appeal.

So, if you are looking for a fixed keel that performs well, while providing a shoal draft option, you might look into this.

http://www.westboundadventures.co.uk/gallery/yacht/aai

 

Do you remember the name of this boat? ISTR it being talked about back then. (I'm actually from Newport Beach, until a couple of years ago.)

I'll look into that if I can.

I'm actually just trying to understand the hydrodynamics of all this. I understand the basics pretty well. But since everything in boat design affects everything else, I wonder how much draft can be compromised without compromising the boat too much -- especially if the effects can be mitigated elsewhere. That's why I'm asking about particularly good shoal draft designs. So to the centerboard fans, your points are well taken, but...

I've seen that before, and I don't understand what they're trying to achieve. To me it just looks like the rear half is just running in the turbulence of the front. Perhaps someone could answer this one for me -- it's been discussed here before.

 

Herreshoff H-28.

Maybe bigger than you are looking for. But if you could find a good one, I think I have rarely, if ever, sailed a shoal draft monohull, without a keel/centerboard configuration, that could go to weather as well.

Robert

 

My father had an Alan Payne-designed Columbia 23 with 1'10" draft. It was **NOT** what you want. If it heeled in a puff, it would slide to leeward yards at a time. Great design for casual sailing in very shallow water, although the construction was questionable.

I have a Capri 22 with a wing keel, 2'10" draft. I don't feel at a disadvantage racing against a Saber 28 or Catalina 27. I've never sailed against the 4" fin keel version, though, so I can't comment on the difference. I have not gotten a pot buoy's line tied in a know around the wing, yet.

I have often sailed/raced on a Tartan 33 with the Scheel keel. All around performance is quite good, though it's pretty heavy/beamy for light airs.

We have a shoal draft Hunter Legend 37 in our fleet. I forget exactly what bulb/wing he has. He has been winning.

If you go back to the 1950's, the keel/centerboard boats had quite small centerboards. I think the thought process was "The keel should have 10% more area, I will give it that extra area in a CB." It was found later that a big CB that did most of the work upwind was better. Charley Morgan was among the first to use a big, high aspect ratio board.

 

Gulfstar 40. Sailed and raced on one. Ted Hood design, heavy centerboarder, draws 3'11" with the board up, and 11'3" with board down. Narrow hull, low wetted surface, unbelievably quick for a heavy boat. Points and goes upwind like crazy with that high-aspect 7 foot blade down. We would sail boat for boat with boats of same waterline length weighing half as much.

 

I don't recall what Steve named it for that regatta. I think the boat was converted to an elliptical keel and sold soon after.

It's been a long time, but IIRC the rule was modified to add half the width of the wings to the keel depth. That pretty well nullified the rating benefit of the shoal draft of the Tandem Keel.

You have to remember that the keel is running at an angle of attack of probably 4 - 6 degrees. So the two "keels" are really working as one slotted foil. Slotted foils can be as much as 30% more efficient than solid foils (although this one is probably not anywhere near that effective).

 

I used to sail on a classic S & S centeboard yawl. 58'3" LOA, beam was 14' 6", and it drew 5' 6" with its board up. It weighed 35 tons. With the big board down, it drew 11 feet and went to windward surprisingly well. Off the wind, we used what we called the "baby" board, something like a fixed trim tab to improve the tracking, located aft of the big board. We got into a tacking duel somewhat with the 12 metre Valiant in 20 knots of wind and did reasonably well until they figured out they were like 3 knots faster upwind then we were and then they just sailed off. I think the reason we managed to do well upwind was partly the design, partly luck, and partly the crew skill.

 

kirby designed nightwind 35 centerboarder, sails upwind with the best of them

 

What makes the slotted foil keel 30 % more effective than a solid foil?

Thanks,

John

 

I don't have my copy of Theory of Wing Sections with me, but basically the flow through the slot delays turbulent separation, if you are viewing the two elements as a whole. The 30% increase in efficiency is a recollection on my part from reading an example provided in the book. I don't recall the section, thickness, or angle of attack. I am sure that the keel in question is not operating under those conditions.

Solid Wing sails like those used on C-Class cats use slots to great advantage, especially at greater cambers, where separation happens readily.

I'm sure Tom Speer can give us all a greatly detailed description and mathematical model for this. I can't.

I want to clarify that I am not advocating the Tandem Keel as the best solution. I was simply giving anecdotal evidence as to the performance in a single regatta where I witnessed it in a semi-controlled situation. There were at least two other well sailed WL 24s with normal keels in the same races to compare with.

Regarding your rudder, I would not add any wings to the rudder on your boat.

 

Paul,

Thanks for the reply. As for the wing on the rudder... I am building a rudder to replace the long blade type on my Precision 18. It's just a prototype I'm playing with. My rudder sticks down about 6 inches below my shoal draft keel. So sailing in 18 inches of water isn't really true because of the rudder length. I took 8 inches off and I'm adding a wing in an effort to make up for the 8 inches. Any thoughts?

Thanks,

John

 

I think I'd hold off adding the wing on the rudder. Maybe try it out first and see if you really need it.