# Wing Keel - how does it work?



## Daveinet (Jun 10, 2010)

I've read many discussions on Wing Keel vs fin keel. Most of those discussions deal with how the boat acts, comparing one to the other, but no one talks about how a wing keel works.

I understand that with a wing keel, there is lift, that makes sense for down wind, as the boat should displace less water and should go faster - all well and logical. What I have difficulty understanding is what happens on a beam reach as the boat heels? You have a keel which by its shear weight is supposed to reduce how far the boat heels, but then you have a wing that is lifting on the keel. It seems to me that lift when heeled over would be counter productive. That's the part I don't quite get.

In context, I was thinking about what would happen if one added a pivoting wing to a boat with a center board. When the centerboard was down, the wing would function normal. As the centerboard is cranked up, the wing would pivot - staying horizontal and pretty much be neutral in its function - or atleast would not drag, so you could motor in to shore with the centerboard up.

Just trying to understand the advantage of the wing, and if it has value in other types of keel setups.


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## deniseO30 (Nov 27, 2006)

I'm no expert on this but I think the "wing" is just the way of getting enough mass to make up for the shortness of the keel and giving it less turbulence in the water. I don't think it has "lift" in the sense of wings on planes, but again.. I don't really know


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## nickmerc (Nov 2, 2008)

I believe the wing portion of the keel "adds length" when heeled over. The wing that extends horizontally when not heeled. As you heel the wingtip actually goes deeper in the water.

Now, this may not work really well for the stubby wing keels, but this was the intent of the design.
________
1LovelyKiss


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## Faster (Sep 13, 2005)

I think there are a couple of things at play here.. hopefully Jeff H will weigh in with the definitive answer!

Center of gravity is lowered with a heavier mass deeper in the keel - this is nothing new, and a lot of keels in early years had a thicker section down low than at the root in a similar attempt to lower CG and hence addding righting moment. Another leading example of this idea was the Scheel Keel that was offered as a shoal draft option prior to the 'wing' trend. Our 1963 Shark had an "anvil shaped" keel that accomplished a similar goal. Stars and Cal 20s had bulb keels years ago too...

The 'wing' came into popularity after the Aussies took the AC from the US, when Ben Lexcan designed the 12 meter around a winged keel concept - in theory the wings add an 'end plate' that minimized keel tip vortex losses - blocking the high-to-low pressure path across the keel tip and increasing overall efficiency. The idea is similar in the winglets you see on airliners' wing tips today. 

In practical terms, I think the wing keel has gained favour partly due to the initial 'trend', but mostly from the ability to offer shallow draft and a less compromised CG in the same package.

One of the knocks on the idea is that, once aground a conventional keel can be 'heeled off' whereas a wing keel actually gets deeper with heel as mentioned previously... in this case that's not a good thing... Of course the idea is not to run aground in the first place!


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## seabreeze_97 (Apr 30, 2006)

As I understand it, the wing is essentially producing lift, but in the opposite direction. It reduces lift-induced drag by acting as a winglet on the foil. This improves the aspect ratio. The inverted lift provides additional stability. When heeled, the same properties actually make the boat point better upwind. They usually suffer downwind due to greater surface area wetted surface drag. It does reduce draft.


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## southshoreS24 (Aug 31, 2009)

from a pro seaward site:Straight Talk about Seaward



> The wings aft accomplish several things; 1.) They force laminar flow over the main keel section. 2.) They become miniature keels as the boat heels. 3.) They act as skegs (like feathers on an arrow) contributing to excellent directional stability They do not interfere with trailering at all.


while i do own a seaward, mine does not have the winged keel, and this sit is very skewed in opinion towards seawards. I love mine and find it a great boat for my uses.


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## Omatako (Sep 14, 2003)

I don't know what winged keels do for boat specifically so this is just my uneducated take . . .

On race cars they have foils on the rear to produce down-force but this only becomes effective when the car reaches about 150 mph. On a passenger car at 70 mph, it's just additional weight.

On sailboats . . . . . I suspect it's pretty much the same.


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## nickmerc (Nov 2, 2008)

The winged keel is not for adding downforce to a boat. No point in lowering the waterline as you go faster. I would buy the reduction in tip vortices but I am not sure how much of a return you would get at 5 kts.

On street cars the wing on the trunk is a spoiler to spoil the lift as cars go faster. It helps to keep the rear wheels on the ground. It is also for looks. Some of the street racing cars do have wings that produce downforce and at high enough speeds they do work. Those speeds are not legal in the US.
________
Glass weed pipe


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## Faster (Sep 13, 2005)

nickmerc said:


> The winged keel ...... I would buy the reduction in tip vortices but I am not sure how much of a return you would get at 5 kts.


That's probably true.. this was the touted theory at time of the 'breakthrough', but of course the entire Australian 12 was designed around it (the keel idea) and it had a lot of other advantageous features as a result.

In reality, I think it's a trendy way to get the ballast low.. if wings really worked I doubt we'd be seeing the proliferation of narrow corded deep bulb keels on the various new (non-canting) high performance boats out there now from Farr and others. In any event any "wing related" gain is probably only recognizable at a very high level of racing.


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## deniseO30 (Nov 27, 2006)

don't see how tons of lead or iron could do anything like hydrofoils do! and yes, some wing keels look like they were styled after hydrofoils

this is not in anyway to be confused with wing keels
HydroSail


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## johnshasteen (Aug 9, 2002)

What wing keels do best is firmly implant you if you run aground on a muddy bottom.


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## PalmettoSailor (Mar 7, 2006)

johnshasteen said:


> What wing keels do best is firmly implant you if you run aground on a muddy bottom.


That is so true, and its why you rarely find a wing keel boat in the shallow, mud bottomed Chesapeake Bay....Oh Wait, wing keels are very, very popular here (and much of the rest of the east coast). People run aground with wing keels in the Chessy's mud bottom, regularly and motor themselves off with no problems. I've found the bottom several times myself and have manged to get of with no drama and both of my boats have had wing keels.

This criticism fall in the category of old wives tails to me you hear it repeated endlessly on the internet yet you never really meet anyone at the marina that has such a horror story. If you ground yourself so hard that you're not able to motor or kedge yourself off, you get a tow, wing keel or no. I'm not buying that you're way worse off than you would be with a fin keel. Also, you're less likely to run aground in the first place with over a foot less keel.

There are better reasons to criticize a wing, keel like a tendency to round up more than its fin keel counterpart.


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## Classic30 (Aug 29, 2007)

Faster said:


> That's probably true.. this was the touted theory at time of the 'breakthrough', but of course the entire Australian 12 was designed around it (the keel idea) and it had a lot of other advantageous features as a result.
> 
> In reality, I think it's a trendy way to get the ballast low.. if wings really worked I doubt we'd be seeing the proliferation of narrow corded deep bulb keels on the various new (non-canting) high performance boats out there now from Farr and others. In any event any "wing related" gain is probably only recognizable at a very high level of racing.


IIRC from what was written by people actually on the boat at the time, the Australian 12 success you speak of had less to do with the physical characteristics of the newfangled wing keel than the psychological effect it had on the opposition.. A large number of yacht races at all levels are won long before the start.

I for one agree with you that it's a trendy way to get ballast low and gives you a shallower draft than you could get otherwise, but it's other advantages are probably nil - especially at a high level of racing - since at least one disadvantage is that any damage to one of the wings will stuff your windward performance quite dramatically. I suspect that's the real reason you don't find wing keels on high-performance boats.


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## Omatako (Sep 14, 2003)

nickmerc said:


> The winged keel is not for adding downforce to a boat. No point in lowering the waterline as you go faster. I would buy the reduction in tip vortices but I am not sure how much of a return you would get at 5 kts.
> 
> On street cars the wing on the trunk is a spoiler to spoil the lift as cars go faster. It helps to keep the rear wheels on the ground. It is also for looks. Some of the street racing cars do have wings that produce downforce and at high enough speeds they do work. Those speeds are not legal in the US.


Sorry, I obviously never made my point very well. The point I was trying to make is that at the speed at which the average cruising boat sails, the winged keel is having zip effect on the performance pretty much the same as the foil on the average sedan (which you appear to agree with  ).


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## Daveinet (Jun 10, 2010)

I assumed the wing was designed for lift, not down force, is that true? 

Trivia: The guy who was really the pioneer on down force was Peter Byrant in the late 60s. The car he developed was the T22 which developed 1.6Gs at 100 MPH. He passed away a little over a year ago. Nice guy, I actually emailed him a few years back - in his off years he was VP of engineering for the company who made my motorhome.


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## Classic30 (Aug 29, 2007)

Daveinet said:


> I assumed the wing was designed for lift, not down force, is that true?


IIRC, the wing is designed to minimise 'spill' off the tip of the keel and hence improve the keel's lift characteristics to windward. Just like the 'winglets' on a Boeing...

They found out years later that a properly-designed keel bulb achieves the same effect - near as makes no difference - with less drag and better impact resistance... but 'wings' allow shallower draft - and are trendier!


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## Vasco (Sep 24, 2006)

As for groundings, I've done it more than once in my CS36M with its patented Hydrokeel in the 22 years I've had this boat. No problem getting off. Only needed assistance once when a friendly Hunter 27 pulled me off at Bakers Haulover near Miami. My main complaint with the keel is that it is very difficult to get the boat to sit right in the cradle at haulout time.


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## Jeff_H (Feb 26, 2000)

This is from a draft of an article that I had written for another purpose:
Wing keels 
Wing keels are a specialized type of bulb keel. Instead of a torpedo shaped bulb there are small lead wings more or less perpendicular to the keel. These concentrate weight lower like a bulb and properly designed they also can useful in reducing tip vortex. There has been some discussion that wings increase the effective span of the keel when heeled over but this does not seem to be born out in tank testing of the short wings currently being used in production sailboats. Not all wings are created equal. They potentially offer a lot of advantages, but they are heavily dependent on the quality of the design and I really think that many wing designs are not really working to their potential. 

Then there is the whole grounding issue. The popular perception is that wing keels are harder to free appears to be accurate. The theory is that if a boat is moderately vertical when it runs aground, the usual remedy of heeling the boat over, simply digs one wing into the bottom. This seems to be born out by discussions that I have had with towboat skippers on the Chesapeake who tell me that freeing boats with wing keels is noticably more difficult and that they always ask before attempting to free the boat since the need to use more force and different techniques.


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## rmeador (Jan 16, 2010)

These repeated comparisons between a wing keel and the spoiler on a race car are specious. Water is about 1000 times more dense than air, so you will realize the "downforce" at a much lower velocity. Also, the primary use of a spoiler on a non-race car is reducing drag due to turbulence, which is probably a similar effect to that noted above with the winglets on many modern airplanes -- they increase efficiency by 6-9% on an airliner. I don't know how that number translates to use in water, but it could be enough for it to make a difference for a racing sailboat.


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## Daveinet (Jun 10, 2010)

Trying to think about what one could do with lift. If the wing was slightly v-shaped and fairly wide, you could get some lift as well as reduction in heeling. As the boat heels over, one wing would be level providing lift, while the other wing would be also pushing sideways, trying to straighten the boat up. I suppose the question becomes at what cost of drag. More sail area can compensate for drag. With a planing hull, it should get you on plane sooner. 

Just doing some brainstorming.


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## Classic30 (Aug 29, 2007)

Daveinet said:


> Trying to think about what one could do with lift. If the wing was slightly v-shaped and fairly wide, you could get some lift as well as reduction in heeling. As the boat heels over, one wing would be level providing lift, while the other wing would be also pushing sideways, trying to straighten the boat up. I suppose the question becomes at what cost of drag. More sail area can compensate for drag. With a planing hull, it should get you on plane sooner.
> 
> Just doing some brainstorming.


Brainstorming is good! If you're really interested, have a look at the foils on a Moth..

...but you'll find that the forces required to vertically "lift" anything other than a planing dinghy are not going to do the keel on a larger boat any good, because they'll be trying to bend it at 45 degrees meaning you'll need a far stronger keel than would otherwise be necessary kind-of negating any perceived benefit. 

Besides, the LAST thing you want on a displacement keel-boat is to provide vertical "lift"! All this will do is reduce your waterline length and slow you down.

Jeff_H has already explained it all much better than I can.


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## COOL (Dec 1, 2009)

Daveinet said:


> I suppose the question becomes at what cost of drag.


That is generally the downfall of a wing keel.
Their benefits seldom out weigh their cost in drag.
While the wing keel did seem to be effective within
the confines of the 12 Meter Rule, all the production
builders that built wing keel versions of their boats to
acheive shallow draft, created boats that were much slower
than their fin keeled sisterships.


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## Daveinet (Jun 10, 2010)

I as thinking more along the lines of a semi-planing hull, such as the Beneteau 210. Centerboard weighs 770 lbs. If one could create 700 lbs of lift, the centerboard would have a neutral effect on the weight of the centerboard. The difficulty would be making sure some of the lift was as aimed the right direction to prevent heel, hence the V. 

Seems from the responses, I need to find a good hydrofoil calculator for a reality check. Don't want to be trying something as silly as creating perpetual motion.

BTW: I've seen those moths on Youtube. They are pretty cool. I like where one guy said he got a ticket for going to fast in a restricted area. Too funny to get a speeding ticket on a sail boat. Seems that ticket is more like a trophy.


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## Classic30 (Aug 29, 2007)

Daveinet said:


> I as thinking more along the lines of a semi-planing hull, such as the Beneteau 210. Centerboard weighs 770 lbs. If one could create 700 lbs of lift, the centerboard would have a neutral effect on the weight of the centerboard. The difficulty would be making sure some of the lift was as aimed the right direction to prevent heel, hence the V.


To my way of thinking, hypothetically, if you had a Bendytoe 210 you'd be better off trying foils than any kind of winged-keel. Seeing something like that lifting off the back of a wave in a 30kt blow should be enough to scare the opposition into retirement!! 

The issue with centerboards is that by nature they tend to move around in the centercase. To get any kind of 'lift' translated into something useful, you need the foils rigidly connected to the boat.


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## mccary (Feb 24, 2002)

I am not marine architect. The 12 meter "formula" allows for different designs. If the mast height gets bigger something else has to be reduced to accommodate the change. But a wing keel has a limited depth and when heeled, the wing has the effect of a deeper keel. So the formula is cheated a bit. In a race that the difference is measured in 100ths of a knot, any "advantage" is positive.

I have to wonder how a wing keel compares to a fin keel when all other aspects of the boat are the same...


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## Faster (Sep 13, 2005)

mccary said:


> .....I have to wonder how a wing keel compares to a fin keel when all other aspects of the boat are the same...


There's a noticeable difference in performance between, say, a Catalina 34 or 36 wing keel vs fin keel... with the fin coming out ahead (at the expense of draft, obviously) I believe that's essentially true of any of the production boats offered in both versions.


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