Return to Winged Keels

Santanasailor

Charter Member. Scow Mafia
1,341
700
North Louisiana
That's actually pretty close to what I remember of Australia II's keel; I think her wings were angled slightly forward.

- DSK
I believe they were angled downward.  Probably one of the better shoal draft designs for pure sailing.  (Yes, I know, 12’s were not shoal draft boats but its the design). As far as another aspects, maybe not so much, good for gathering weeds and other items found close to the surface…Oh for the days when weeds were short, and the oceans were clean. 

D1811A86-7353-4E5C-BC92-85E27C4E98AD.jpeg

 
Last edited by a moderator:

Ishmael

Yes, we have no bananas
50,756
11,148
Fuctifino
I believe they were angled downward.  Probably one of the better shoal draft designs for pure sailing.  (Yes, I know, 12’s were not shoal draft boats but its the design). As far as another aspects, maybe not so much, good for gathering weeds and other items found close to the surface…Oh for the days when weeds were short, and the oceans were clean. 

View attachment 483155
Do they have that block chained to it so nobody steals it?

 

Hukilau

Member
410
183
Branford, CT
without some pretty sophisticated tank/wind tunnel/CFD most winged keels are pretty draggy and useless. At best they keep the VCG low with shallow draft.
And this is why they are still making wing keel boats.  They allow for a shoal draft version; your average sailor of today isn't as concerned about racing as he is about running aground.

 
What's the difference in the real world. Here are some comparisons of base ratings for some Catalina models (YRA/LIS data):

Catalina 270 - 198

Catalina 270W - 204

Catalina 34 - 156

Catalina 34 Wing - 165

Catalina 400 DK - 108

Catalina 400 W - 111

So the wing is assumed to have a penalty of 6-10 sec/mile around the whole race course. The upwind penalty is higher, but the offwind penalty is negligible, and the wing might actually be an advantage there. Cruisers sail upwind a smaller percentage of the time than racers. It's no wonder that cruisers find the wing keel boats satisfactory.  
Does the PHRF rating reflect drag, or the higher pointing of a conventional keel?  A boat with a nice deep fin keel that points 3-5 degrees closer to the wind on each tack should be *a lot* faster than a wing keel over the same course.  6, 9 and 3 seconds / mile don't reflect the differences I would expect based only on drag differences.  

 

European Bloke

Super Anarchist
3,407
826
Does the PHRF rating reflect drag, or the higher pointing of a conventional keel?  A boat with a nice deep fin keel that points 3-5 degrees closer to the wind on each tack should be *a lot* faster than a wing keel over the same course.  6, 9 and 3 seconds / mile don't reflect the differences I would expect based only on drag differences.  
They point in roughly the same direction. They travel in completely different directions.

 

IStream

Super Anarchist
10,784
2,970
Does the PHRF rating reflect drag, or the higher pointing of a conventional keel?  A boat with a nice deep fin keel that points 3-5 degrees closer to the wind on each tack should be *a lot* faster than a wing keel over the same course.  6, 9 and 3 seconds / mile don't reflect the differences I would expect based only on drag differences.  
FWIW, I believe Catalina increased the ballast a bit on their wing keeled boats vs. their fin keeled sisters to keep the VCG about the same and offset some of the performance loss.

 

Panoramix

Super Anarchist
And this is why they are still making wing keel boats.  They allow for a shoal draft version; your average sailor of today isn't as concerned about racing as he is about running aground.
Tbh, here they've pretty much disappeared. For staying close to the shore, IMHO a twin keel is superior in about every aspect except may be a few cm of extra draft (10cm or 4 inch may be) but as you can dry the extra depth doesn't really matter.

 

Steam Flyer

Sophisticated Yet Humble
42,317
8,610
Eastern NC
Does the PHRF rating reflect drag, or the higher pointing of a conventional keel?  A boat with a nice deep fin keel that points 3-5 degrees closer to the wind on each tack should be *a lot* faster than a wing keel over the same course.  6, 9 and 3 seconds / mile don't reflect the differences I would expect based only on drag differences.  
It only reflects drag or greater keel efficiency in that those things produce different finish times.

PHRF is NOT a measurement rule, although a lot of committees want to build in their own personal rocket science-y bullshit so their buddies can win

- DSK

 

SemiSalt

Super Anarchist
7,752
269
WLIS
It only reflects drag or greater keel efficiency in that those things produce different finish times.

PHRF is NOT a measurement rule, although a lot of committees want to build in their own personal rocket science-y bullshit so their buddies can win

- DSK
It's seconds/mile around the course. The shoal draft boat, with wing or not, may be faster than the deep keel boat off the wind, so it could be -15 sec upwind but + 7 sec downwind,  and 8 sec on average.

Now where did that 3-5 degree number come from? Sailing a bit lower can reduce the amount of lift required from the keel quite a lot, and is probably the right thing in a wing keel boat. A designer may think this gives him leave to make the spreaders 5 inches longer which can be a good thing.

PHRF has adjustments for all sorts of things like different propellers, different jib overlaps, pole lengths, etc, including keel variants. As far as I know, they are mostly swagged. 

 
Tbh, here they've pretty much disappeared. For staying close to the shore, IMHO a twin keel is superior in about every aspect except may be a few cm of extra draft (10cm or 4 inch may be) but as you can dry the extra depth doesn't really matter.
I agree: while a shoal draft keel of whatever design reduces your probability of running aground, that probability is always high when sailing in shallow water. Once you do hit bottom, a twin keel seems a far less dire predicament, even if that means a bit more difficulty in a glancing impact. And in many cases, being able to hit bottom and stay there, drying out, is in fact quite an advantage.

So for shallow water, twin keels seem more sensible than one keel, regardless of the bottom of the keel.

It's not all about raw performance or righting moment. As was noticed above, a deep keel wedged into the bottom is much slower than a shallow keel not hitting the bottom, and twin keels hard aground are much better than any single keel hard aground.

In deep water, the deeper keel essentially always wins. Putting anything at the end -- winglets, bulb, a big fat tip -- is worse than stretching into the depths from a coefficient of lift point of view.

Roll in the trade-offs. There are always trade-offs, there is no achievable ultimate solution.

 

DDW

Super Anarchist
6,313
1,011
DDW, I still have a hard time wrapping my head around the practice of 'filling our sailplanes with water' and I know the theory and stats and all but it seems contradictory to me. That is until I think back to skiing down hill and how a heavier skier will reach a higher speed on the same skis and the same slope. I have never had the privilege of flying in a ballasted sailplane but would love for you to show me sometime just what that is all about. Do you have a photo of your aftermarket winglets? It seems like it would be a very hard thing to do to pick up a saw and shop off the wing tip of a 6 figure sailplane just to fit a unknown winglet. That is as ballsy as flying sailplanes in the first place!
The winglets I installed (or I should say had installed by a licensed shop) came from the original manufacture (Schleicher) bespoke for that sailplane, so not an unknown. In fact until the end of the model run they continued to mold them without the winglets, if you ordered them from the factory they would cut the tips off and install their kit (probably near 100% were sold that way after they introduced the winglets). Yes, you simply sawsall the tip off, install a tip rib with the connection features, plug it in (they come off in the trailer), and fair and finish. Makes you a little sick when you see the sawsall bite in at first.... I don't seem to have great photos of the winglets before and after but I've added some bad ones. 

Increasing the weight just moves the whole performance curve up the speed range. In fact in the last 3 decades by far the largest increase in performance is associated with increasing ballast capability. A Jonkers JS1 for example can carry about 400 lbs of water. I've flown right next to sisterships for long glides (>50 miles), with our glass cockpit instruments and anti-collision devices I can track the other sailplane's location, speed, and sink rate. One friend flies an ASH 31, basically the same sailplane as mine with 18m wingtips, but optionally 21m wingtips, and the ability to load to 12 lbs/ft^2 (I can only go to 9). If he is flying 21m but unballasted, there is a noticeable difference but not dramatic (claimed glide ratios are 50:1 and 54:1). If he makes a mistake or two I will stay with him (though as a former and current national champion he doesn't make many).  If he is flying ballasted we achieve approximately the same glide but he is going 10 - 12 knots faster and that is a dramatic difference, simply no chance of hanging on. That is why in our Truckee FAI contest, we weigh the gliders and adjust handicap based on weight. 

My glider is only about 50 lbs below max takeoff weight with me sitting in it, so though I do have water ballast capability I do not bother with it on the ASH. When we had a Duo Discus we would fill that thing up and it made a big difference. 

No winglets, just slightly upturned as originally molded:

NoWinglets.jpg

Winglets added. They split just inside the tip wheel:

Winglets.jpg

 

slap

Super Anarchist
5,690
1,156
Somewhat near Naptown
So for shallow water, twin keels seem more sensible than one keel, regardless of the bottom of the keel.
Except for one thing - heeling a single keel boat reduces the effective draft but heeling increases a twin keel or wing keel fitted boats effective draft.    Unless you are able to heel the boat *way* over.     And there have been times where I've gone aground, pointed the boat in the other direction and gotten off.    Seems like a twin keel or wing keel boat may be harder to turn around.

 
Now where did that 3-5 degree number come from? Sailing a bit lower can reduce the amount of lift required from the keel quite a lot, and is probably the right thing in a wing keel boat. A designer may think this gives him leave to make the spreaders 5 inches longer which can be a good thing.
I have a boat that is exceptionally good at pointing and that I race in OD, a J/35.  I'm very sensitive to pointing and VMG, and have heard some J/35 old timers talk about some shorter keel versions that didn't point as well until their keels were brought up to class standards - understanding there is a weight distribution issue and other factors involved.  Have seen this with other shoal draft boats locally that don't quite point with their regular fin keel counterparts - this was a problem in the 105 fleet for a bit until a group of owners got together and got a bulk discount on keel repair.  Never measured how much worse they pointed but have heard tales...

So it's a SWAG and based on second hand info as well.  Not pulled completely out of my ass but it's definitely from the rear left pocket of my jeans... 

 

Panoramix

Super Anarchist
Except for one thing - heeling a single keel boat reduces the effective draft but heeling increases a twin keel or wing keel fitted boats effective draft.    Unless you are able to heel the boat *way* over.     And there have been times where I've gone aground, pointed the boat in the other direction and gotten off.    Seems like a twin keel or wing keel boat may be harder to turn around.
Yes, with a twin keel if you run aground while the tide is going out, the chance are that you are stuck unless you were going to windward fully powered but then you have to deal with the potentially bigger issue of hitting the bottom @ 6 knots! 

If you are taking risks like this with a fin keel, chances are that sooner or later you will end up on the side waiting for the tide...

IMO, the big advantage of the twin keel is that you can go somewhere nice while the tide is up, let it go, dry the boat and enjoy the place while others are anchored in the swell! Thus draft is less relevant, it just means that you dry a bit sooner or anchor a bit further out but still much closer than shallow draft fin keel boats. You can also stay in small ex fishing harbours while others are in packed marinas.

 
Last edited by a moderator:

Elegua

Generalissimo
4,377
1,945
Lower Loslobia
I've gotten the feeling that shoal draft is a bit like 4-wheel drive; you just get stuck in places that are harder to get out of. 

 

weightless

Super Anarchist
5,607
581
I've gotten the feeling that shoal draft is a bit like 4-wheel drive; you just get stuck in places that are harder to get out of.
Maybe less of an affectation. I've yet to see "shoal draft" painted on the topsides of a boat.

It seems to me that there are a couple of different flavors of shoal draft with different uses. I grew up in an area with a lot of interesting but shallow water. The bottom was stone and the tides were negligible. Keel / centerboards were popular there for a while. When the centerboard started bumping on the bottom is was just past time to tack ;) . Shoal draft was nice. And, for a time, 6 feet was considered a very deep keel. Over the years folks ditched the boards and moved on to ever deeper keels. Perhaps the summer cruise went away for most folks and there were enough deep anchorages for a weekend? The ability to dry out wasn't ever much use there. A place with interesting tidal waters would make bilge keels a more appealing option. I spent a bunch of time bopping around the Pacific in a boat with about 1 meter of draft and there were places that I thought even that limited my options a little. I know folks who have cruised with the best part of 3 meters of draft in the same areas who claimed to never find it limiting. I don't think it's strictly an engineering problem. Expectations and the dark and mysterious realms of headology play into it.

 
Last edited by a moderator:

SemiSalt

Super Anarchist
7,752
269
WLIS
Back a pretty long time ago, Yves-Marie Tanton wrote in a blog that he had been studying the French development of "biquille with bulb" boats. These have two high aspect ration keels with bulbs as seen the picture of a Django 7.70. YMT was favorably impressed. It's interesting to me how the concepts of twin keel and shallow draft have be ripped apart. 

2022-01-04_19-10-28.png

 
Top