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Old 23-06-2016, 08:38   #226
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Re: Cockpits like Amel Super Maramu

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Originally Posted by jtsailjt View Post
LOL, if you seriously think that reading a (almost 40 years "behind the times) 1978 article dealing with rudder design for "high performance small craft" is the last word on either rudder design OR the practical considerations involved in deciding what's best for a cruising sailboat, then I suggest that MUCH more studying is in order. FYI, my Bachelor of Science was in Civil Engineering focusing on structural design, and I've spent the last 35 years flying all types of high performance aircraft, from F-16's to most Boeings, so I think I'm reasonably well informed about how forces act on structures as well as how airfoils work, but thank you for your attempt to educate me about what you call the "real science."

We do agree that spades yield better low speed maneuverability but how important is this to a competent helmsman on a cruising sailboat? If your idea of "cruising" is parking your shorthanded boat in a marina slip every night, then I suppose the ability to make 90 degree bat turns is very high on your list of priorities. But I think most "real cruisers" tend to anchor out or pick up a mooring much, much, more often than they spend in a slip, so that the somewhat lesser low speed maneuvering that a skeg mounted rudder offers isn't something that they find limiting. Besides, I've had 2 skeg mounted rudder sailboats and have always managed to find my way into a slip when I needed to and I make no claim to being anything better than an average cruising helmsman. Also, most boats in the size range you are considering will be fitted with a bow thruster, which will allow any skeg equipped sailboat to turn 360 degrees in its own length if needed. How much more maneuverability do you need?

But enough about impressing all onlookers as we squeeze our 50'+ boats into tight marina slips all by ourselves. What we all do for the vast majority of our time on the water is to sail, and a skeg mounted rudder performs just fine in this regime, both in a straight line and while tacking (no need to "wear ship") while offering greater longitudinal stability, especially in a "rudder free" situation, as well as offering a more stable hove to platform, and greater protection from unexpected obstructions or ground contact.

One interesting experience I had many years ago, while sailing my full keel Hinckley Pilot 35 downwind in about 20 knots of breeze and 6-8 foot seas, was to catch a glimpse of something just beside the bow followed by few seconds of a rumbling sound followed by a spinning telephone pole(!) surfacing just astern that I had hit broadside at 6+ knots. My boat suffered no ill effects, my current boat would probably have had damage to my maxprop and superficial damage to my skeg, but I probably wouldn't have lost the ability to steer. Besides possibly breaking your wrist as your rudder instantly snapped sideways, what do you think hitting a telephone pole broadside at 8+ knots would do to a cruise in your 50' spade rudder equipped sailboat? Real world situations such as this one weren't mentioned in that 1978 article that you keep posting a link to....

There's no doubt that spade rudders are popular among some sailors and some builders, but is what's "best" for cruising their primary motivation? For builders, it's a lot easier to not have to deal with a skeg, either in the hulls mold or bolting one on and fairing it in. Spades are "sexy" and can make almost any helmsman seem like Dennis Connor as he zips around the marina, which can be a selling point, but take that same potential customer out in 30 knots of wind with a bit too much sail area up and he may find himself wishing for the stability of his good old skeg hung rudder. Your list of builders who have switched to spades leaves quite a few out who are still using skegs, and includes a few that I don't ever seem to see doing much actual cruising out of sight of land.

I recognize the superiority of spades for tight maneuvering and for racers (BTW last Sunday I won my race by about 1/4 mile in my spade rudder equipped Sunfish in a steady 20 knot breeze!) where every bit of drag counts for a lot and rescue is never more than minutes away so the potential loss of the ability to steer isn't anything worth worrying about, but IMHO for a cruiser planning to be as self sufficient as possible in whatever conditions mother nature throws at that cruiser, he/she has other priorities that are better met by a skeg equipped sailboat.

Of course I realize that each of us have our own ideas about how to order our list of priorities regarding the perfect cruising sailboat and I'm completely OK with that. But I think you should be a bit more cautious about assuming that because someone disagrees with your opinion that it's due to a lack of knowledge or education about the "real science" or subject...on their part.

Good writeup, and I'm with ya man. I'll take a Tayana 47, 48, 52 (Perry), or a Hylas 49 (S&S) over a single spade rudder boat any day if there is a choice in the matter, on all oceans. I have seen how intolerant spades are to wild AoA changes (due to water currents in wave tops) when the going gets tough on broad reaches and runs.
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Old 23-06-2016, 08:48   #227
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Re: Cockpits like Amel Super Maramu

Quote:
Originally Posted by jtsailjt View Post
LOL, if you seriously think that reading a (almost 40 years "behind the times) 1978 article dealing with rudder design for "high performance small craft" is the last word on either rudder design OR the practical considerations involved in deciding what's best for a cruising sailboat, then I suggest that MUCH more studying is in order. FYI, my Bachelor of Science was in Civil Engineering focusing on structural design, and I've spent the last 35 years flying all types of high performance aircraft, from F-16's to most Boeings, so I think I'm reasonably well informed about how forces act on structures as well as how airfoils work, but thank you for your attempt to educate me about what you call the "real science."

We do agree that spades yield better low speed maneuverability but how important is this to a competent helmsman on a cruising sailboat? If your idea of "cruising" is parking your shorthanded boat in a marina slip every night, then I suppose the ability to make 90 degree bat turns is very high on your list of priorities. But I think most "real cruisers" tend to anchor out or pick up a mooring much, much, more often than they spend in a slip, so that the somewhat lesser low speed maneuvering that a skeg mounted rudder offers isn't something that they find limiting. Besides, I've had 2 skeg mounted rudder sailboats and have always managed to find my way into a slip when I needed to and I make no claim to being anything better than an average cruising helmsman. Also, most boats in the size range you are considering will be fitted with a bow thruster, which will allow any skeg equipped sailboat to turn 360 degrees in its own length if needed. How much more maneuverability do you need?

But enough about impressing all onlookers as we squeeze our 50'+ boats into tight marina slips all by ourselves. What we all do for the vast majority of our time on the water is to sail, and a skeg mounted rudder performs just fine in this regime, both in a straight line and while tacking (no need to "wear ship") while offering greater longitudinal stability, especially in a "rudder free" situation, as well as offering a more stable hove to platform, and greater protection from unexpected obstructions or ground contact.

One interesting experience I had many years ago, while sailing my full keel Hinckley Pilot 35 downwind in about 20 knots of breeze and 6-8 foot seas, was to catch a glimpse of something just beside the bow followed by few seconds of a rumbling sound followed by a spinning telephone pole(!) surfacing just astern that I had hit broadside at 6+ knots. My boat suffered no ill effects, my current boat would probably have had damage to my maxprop and superficial damage to my skeg, but I probably wouldn't have lost the ability to steer. Besides possibly breaking your wrist as your rudder instantly snapped sideways, what do you think hitting a telephone pole broadside at 8+ knots would do to a cruise in your 50' spade rudder equipped sailboat? Real world situations such as this one weren't mentioned in that 1978 article that you keep posting a link to....

There's no doubt that spade rudders are popular among some sailors and some builders, but is what's "best" for cruising their primary motivation? For builders, it's a lot easier to not have to deal with a skeg, either in the hulls mold or bolting one on and fairing it in. Spades are "sexy" and can make almost any helmsman seem like Dennis Connor as he zips around the marina, which can be a selling point, but take that same potential customer out in 30 knots of wind with a bit too much sail area up and he may find himself wishing for the stability of his good old skeg hung rudder. Your list of builders who have switched to spades leaves quite a few out who are still using skegs, and includes a few that I don't ever seem to see doing much actual cruising out of sight of land.

I recognize the superiority of spades for tight maneuvering and for racers (BTW last Sunday I won my race by about 1/4 mile in my spade rudder equipped Sunfish in a steady 20 knot breeze!) where every bit of drag counts for a lot and rescue is never more than minutes away so the potential loss of the ability to steer isn't anything worth worrying about, but IMHO for a cruiser planning to be as self sufficient as possible in whatever conditions mother nature throws at that cruiser, he/she has other priorities that are better met by a skeg equipped sailboat.

Of course I realize that each of us have our own ideas about how to order our list of priorities regarding the perfect cruising sailboat and I'm completely OK with that. But I think you should be a bit more cautious about assuming that because someone disagrees with your opinion that it's due to a lack of knowledge or education about the "real science" or subject...on their part.
I don't really quite understand what you're trying to say here. So the understanding of hydrodynamics of rudders has changed in 40 years? There has been a movement away from spade rudders during that time, and back to skeg rudders, during the last 40 years since that study was published? If you have a more recent study on rudder hydrodynamics, which shows that skeg rudders work better, I would be happy to read it. I'm always interested in learning more about this interesting subject, and since you are obviously so much better educated on the subject, maybe you can help me out.


Everyone will make up his own mind, what qualities he prefers in his cruising boat, but if you're buying a new boat, it has become almost impossible to buy one with a skeg rudder (other than Oysters and some motor sailers). There is not a designer in the world as far as I know who still thinks that the benefits outweigh the disadvantages, of skeg rudders. But I am not trying to sell you anything -- if you like them, then by all means, like them.


As to WHY spade rudders have taken over - it's not just because of better maneuvering. We covered that in the first dozen posts of this thread. It's much more because they work better sailing upwind, when you need the keel and rudder to produce lift. I do agree with you -- and I said it already in this thread -- that for cruisers who are of the "gentlemen don't sail to weather" persuasion, this won't matter. But some cruisers (like me) do really care about sailing upwind, and for them, the difference in performance of spade vs skeg makes a huge difference. The difference in efficiency is about double, so very much noticeable.


As to strength -- I think it's been well stated by a whole range of posters in this thread -- strength in rudders can be achieved in different ways, and putting on a skeg is not the only or even the best way to make a rudder really strong. If you want a really, really strong rudder, to resist groundings or telephone poles or whatever, having a skeg is not the only way to achieve that. Look at Steve Dashew's designs as an example.
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Old 23-06-2016, 09:18   #228
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Re: Cockpits like Amel Super Maramu

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Originally Posted by Dockhead View Post
I don't really quite understand what you're trying to say here. So the understanding of hydrodynamics of rudders has changed in 40 years? There has been a movement away from spade rudders during that time, and back to skeg rudders, during the last 40 years since that study was published? If you have a more recent study on rudder hydrodynamics, which shows that skeg rudders work better, I would be happy to read it. I'm always interested in learning more about this interesting subject, and since you are obviously so much better educated on the subject, maybe you can help me out.


Everyone will make up his own mind, what qualities he prefers in his cruising boat, but if you're buying a new boat, it has become almost impossible to buy one with a skeg rudder (other than Oysters and some motor sailers). There is not a designer in the world as far as I know who still thinks that the benefits outweigh the disadvantages, of skeg rudders. But I am not trying to sell you anything -- if you like them, then by all means, like them.


As to WHY spade rudders have taken over - it's not just because of better maneuvering. We covered that in the first dozen posts of this thread. It's much more because they work better sailing upwind, when you need the keel and rudder to produce lift. I do agree with you -- and I said it already in this thread -- that for cruisers who are of the "gentlemen don't sail to weather" persuasion, this won't matter. But some cruisers (like me) do really care about sailing upwind, and for them, the difference in performance of spade vs skeg makes a huge difference. The difference in efficiency is about double, so very much noticeable.


As to strength -- I think it's been well stated by a whole range of posters in this thread -- strength in rudders can be achieved in different ways, and putting on a skeg is not the only or even the best way to make a rudder really strong. If you want a really, really strong rudder, to resist groundings or telephone poles or whatever, having a skeg is not the only way to achieve that. Look at Steve Dashew's designs as an example.
DH-you are the moderator.

Here are some boats currently offered with skegs-

Tayana, Caliber, Island Packet, Passport, and Hylas use full or partial skegs currently.

Nigile Calder has a Malo 46-

http://www.maloyachts.co.uk/images/u...na_Malo_46.pdf
http://www.yachtingmonthly.com/yacht...atistics-30154

I have the same rudder-skeg as you. What is wrong with the way your current boat sails ?
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Old 23-06-2016, 09:45   #229
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Re: Cockpits like Amel Super Maramu

Quote:
Originally Posted by jtsailjt View Post
LOL, if you seriously think that reading a (almost 40 years "behind the times) 1978 article dealing with rudder design for "high performance small craft" is the last word on either rudder design OR the practical considerations involved in deciding what's best for a cruising sailboat, then I suggest that MUCH more studying is in order. FYI, my Bachelor of Science was in Civil Engineering focusing on structural design, and I've spent the last 35 years flying all types of high performance aircraft, from F-16's to most Boeings, so I think I'm reasonably well informed about how forces act on structures as well as how airfoils work, but thank you for your attempt to educate me about what you call the "real science."

We do agree that spades yield better low speed maneuverability but how important is this to a competent helmsman on a cruising sailboat? If your idea of "cruising" is parking your shorthanded boat in a marina slip every night, then I suppose the ability to make 90 degree bat turns is very high on your list of priorities. But I think most "real cruisers" tend to anchor out or pick up a mooring much, much, more often than they spend in a slip, so that the somewhat lesser low speed maneuvering that a skeg mounted rudder offers isn't something that they find limiting. Besides, I've had 2 skeg mounted rudder sailboats and have always managed to find my way into a slip when I needed to and I make no claim to being anything better than an average cruising helmsman. Also, most boats in the size range you are considering will be fitted with a bow thruster, which will allow any skeg equipped sailboat to turn 360 degrees in its own length if needed. How much more maneuverability do you need?

But enough about impressing all onlookers as we squeeze our 50'+ boats into tight marina slips all by ourselves. What we all do for the vast majority of our time on the water is to sail, and a skeg mounted rudder performs just fine in this regime, both in a straight line and while tacking (no need to "wear ship") while offering greater longitudinal stability, especially in a "rudder free" situation, as well as offering a more stable hove to platform, and greater protection from unexpected obstructions or ground contact.

One interesting experience I had many years ago, while sailing my full keel Hinckley Pilot 35 downwind in about 20 knots of breeze and 6-8 foot seas, was to catch a glimpse of something just beside the bow followed by few seconds of a rumbling sound followed by a spinning telephone pole(!) surfacing just astern that I had hit broadside at 6+ knots. My boat suffered no ill effects, my current boat would probably have had damage to my maxprop and superficial damage to my skeg, but I probably wouldn't have lost the ability to steer. Besides possibly breaking your wrist as your rudder instantly snapped sideways, what do you think hitting a telephone pole broadside at 8+ knots would do to a cruise in your 50' spade rudder equipped sailboat? Real world situations such as this one weren't mentioned in that 1978 article that you keep posting a link to....

There's no doubt that spade rudders are popular among some sailors and some builders, but is what's "best" for cruising their primary motivation? For builders, it's a lot easier to not have to deal with a skeg, either in the hulls mold or bolting one on and fairing it in. Spades are "sexy" and can make almost any helmsman seem like Dennis Connor as he zips around the marina, which can be a selling point, but take that same potential customer out in 30 knots of wind with a bit too much sail area up and he may find himself wishing for the stability of his good old skeg hung rudder. Your list of builders who have switched to spades leaves quite a few out who are still using skegs, and includes a few that I don't ever seem to see doing much actual cruising out of sight of land.

I recognize the superiority of spades for tight maneuvering and for racers (BTW last Sunday I won my race by about 1/4 mile in my spade rudder equipped Sunfish in a steady 20 knot breeze!) where every bit of drag counts for a lot and rescue is never more than minutes away so the potential loss of the ability to steer isn't anything worth worrying about, but IMHO for a cruiser planning to be as self sufficient as possible in whatever conditions mother nature throws at that cruiser, he/she has other priorities that are better met by a skeg equipped sailboat.

Of course I realize that each of us have our own ideas about how to order our list of priorities regarding the perfect cruising sailboat and I'm completely OK with that. But I think you should be a bit more cautious about assuming that because someone disagrees with your opinion that it's due to a lack of knowledge or education about the "real science" or subject...on their part.
Hummm,,, This post say everything..
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Old 23-06-2016, 13:03   #230
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Re: Cockpits like Amel Super Maramu

Quote:
Originally Posted by Ericson38 View Post
DH-you are the moderator.

Here are some boats currently offered with skegs-

Tayana, Caliber, Island Packet, Passport, and Hylas use full or partial skegs currently.

Nigile Calder has a Malo 46-

http://www.maloyachts.co.uk/images/u...na_Malo_46.pdf
Understand your boat and her statistics

I have the same rudder-skeg as you. What is wrong with the way your current boat sails ?
My boat would be faster and better with a spade. But as I've said -- I don't think it's critical for cruising boats, which aren't typically sailed upwind much. So don't think I'm actually any kind of fan-boy. I just like truth and facts.

As to boats being made with skeg keels:

Island Packet is bankrupt and not producing.
Tayana are no longer in business.
Caliber are semi-long keel boats of '70's design, produced in very small numbers.
Passport -- you are right; missed that one. How many are sold every year?
Hylas -- the new ones have spade rudders; others have semi-balanced rudders with short skegs.
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Old 23-06-2016, 13:10   #231
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Re: Cockpits like Amel Super Maramu

As far as I know Tayana are still in business and producing boats with rudder skegs. Www.tayanaworld.com


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Old 23-06-2016, 13:21   #232
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Re: Skeg or Spade?

I suppose if one is doing a new boat AND one has a choice between a spade and a skeg... all the rest being equal... you can pick the one that suits your type of sailing. The spade seems more performance and race oriented... but for the typical cruiser this may not be the driving factor for the choice. DH's post summed it up nicely.
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Old 23-06-2016, 13:28   #233
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Re: Cockpits like Amel Super Maramu

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As far as I know Tayana are still in business and producing boats with rudder skegs. Tayana | Tayana Yachts Official Website
Yes, you're right -- I stand corrected.

"News of my death are highly exaggerated".

Latest Tayana designs, however, which are from Bill Dixon (who designed my boat), have spades.
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Old 23-06-2016, 13:42   #234
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Re: Skeg or Spade?

Caliber is no longer building boats, but yes all of their designs feature big skegs.
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Old 23-06-2016, 15:12   #235
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Re: Cockpits like Amel Super Maramu

Re jtsailjt's post.

Quote:
Originally Posted by neilpride View Post
Hummm,,, This post say everything..
Me too
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Old 24-06-2016, 00:43   #236
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Re: Cockpits like Amel Super Maramu

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Originally Posted by jtsailjt View Post
LOL, if you seriously think that reading a (almost 40 years "behind the times) 1978 article dealing with rudder design for "high performance small craft" is the last word on either rudder design OR the practical considerations involved in deciding what's best for a cruising sailboat, then I suggest that MUCH more studying is in order. FYI, my Bachelor of Science was in Civil Engineering focusing on structural design, and I've spent the last 35 years flying all types of high performance aircraft, from F-16's to most Boeings, so I think I'm reasonably well informed about how forces act on structures as well as how airfoils work, but thank you for your attempt to educate me about what you call the "real science."

We do agree that spades yield better low speed maneuverability but how important is this to a competent helmsman on a cruising sailboat? If your idea of "cruising" is parking your shorthanded boat in a marina slip every night, then I suppose the ability to make 90 degree bat turns is very high on your list of priorities. But I think most "real cruisers" tend to anchor out or pick up a mooring much, much, more often than they spend in a slip, so that the somewhat lesser low speed maneuvering that a skeg mounted rudder offers isn't something that they find limiting. Besides, I've had 2 skeg mounted rudder sailboats and have always managed to find my way into a slip when I needed to and I make no claim to being anything better than an average cruising helmsman. Also, most boats in the size range you are considering will be fitted with a bow thruster, which will allow any skeg equipped sailboat to turn 360 degrees in its own length if needed. How much more maneuverability do you need?

But enough about impressing all onlookers as we squeeze our 50'+ boats into tight marina slips all by ourselves. What we all do for the vast majority of our time on the water is to sail, and a skeg mounted rudder performs just fine in this regime, both in a straight line and while tacking (no need to "wear ship") while offering greater longitudinal stability, especially in a "rudder free" situation, as well as offering a more stable hove to platform, and greater protection from unexpected obstructions or ground contact.

One interesting experience I had many years ago, while sailing my full keel Hinckley Pilot 35 downwind in about 20 knots of breeze and 6-8 foot seas, was to catch a glimpse of something just beside the bow followed by few seconds of a rumbling sound followed by a spinning telephone pole(!) surfacing just astern that I had hit broadside at 6+ knots. My boat suffered no ill effects, my current boat would probably have had damage to my maxprop and superficial damage to my skeg, but I probably wouldn't have lost the ability to steer. Besides possibly breaking your wrist as your rudder instantly snapped sideways, what do you think hitting a telephone pole broadside at 8+ knots would do to a cruise in your 50' spade rudder equipped sailboat? Real world situations such as this one weren't mentioned in that 1978 article that you keep posting a link to....

There's no doubt that spade rudders are popular among some sailors and some builders, but is what's "best" for cruising their primary motivation? For builders, it's a lot easier to not have to deal with a skeg, either in the hulls mold or bolting one on and fairing it in. Spades are "sexy" and can make almost any helmsman seem like Dennis Connor as he zips around the marina, which can be a selling point, but take that same potential customer out in 30 knots of wind with a bit too much sail area up and he may find himself wishing for the stability of his good old skeg hung rudder. Your list of builders who have switched to spades leaves quite a few out who are still using skegs, and includes a few that I don't ever seem to see doing much actual cruising out of sight of land.

I recognize the superiority of spades for tight maneuvering and for racers (BTW last Sunday I won my race by about 1/4 mile in my spade rudder equipped Sunfish in a steady 20 knot breeze!) where every bit of drag counts for a lot and rescue is never more than minutes away so the potential loss of the ability to steer isn't anything worth worrying about, but IMHO for a cruiser planning to be as self sufficient as possible in whatever conditions mother nature throws at that cruiser, he/she has other priorities that are better met by a skeg equipped sailboat.

Of course I realize that each of us have our own ideas about how to order our list of priorities regarding the perfect cruising sailboat and I'm completely OK with that. But I think you should be a bit more cautious about assuming that because someone disagrees with your opinion that it's due to a lack of knowledge or education about the "real science" or subject...on their part.


I'll take the pictured skeg rudder set up any day over a spade rudder alone. I really don't see how it will perform any less hydrodynamically than a spade. The rudder and skeg are integrated shape wise top to bottom, and look like what I see on all airplane wings and tail fins with the flaps. On planes we don't see the entire wing or tail fins/rudders (or whatever the hell they're called) rotating to create lift. Maybe this example is too simple, but I'd figure the reason why an airplane wing doesn't rotate in it's entirety has to do with strength.
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Old 24-06-2016, 01:23   #237
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Re: Cockpits like Amel Super Maramu

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. . . On planes we don't see the entire wing or tail fins/rudders (or whatever the hell they're called) rotating to create lift. . . .
This was discussed. Airplane wings are cambered, so generate lift with zero angle of attack. There is no reason to make a whole airplane wing movable, because it is always working the same way. Keels and rudders can't be cambered, because they have to work both ways. An uncambered foil works by being angled to the flow. If you break up the flow by dividing up the wing into a fixed and movable part, this seriously harms the efficiency of the foil. These are very basic facts which are not controversial -- aerodynamics/hydrodynamics 101.

And modern airliner tailplanes usually ARE all moveable. That's because, unlike the wing, these may be called on to produce varying amounts of lift depending on the loading of the aircraft, and it's more efficient as a spade.


That being said, for cruisers who don't sail upwind that much, these things may not be all that important. Still, there are so few advantages to skeg rudders that there's hardly any reason to build them that way even if you don't care much about upwind performance. The only cruising sailboat built today in large numbers with full skeg rudders, as far as I know, is the Oyster. As someone above showed, Oysters have massively built rudder shaft structures which are several times stronger, all by themselves, than is required by the most stringent ratings. You could chop the skeg off, and the rudder would still be stronger than that of 99% of boats out there. You have to think that the skeg on Oysters is just decoration, made to appeal to very conservative buyers who haven't gotten used to spade rudders yet (IIRC, the average new Oyster buyer is a Brit in his late '60's -- and a very wealthy one ). Even so, the newer and larger Oysters, the 825 and 885, have spade rudders. I bet we won't see any more new designs from Oyster with skegs.
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Old 24-06-2016, 03:16   #238
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Re: Skeg or Spade?

As far i know there is a bunch of good clasic boats with skegs performing upwind or to weather like freaking trains....i dont get the point ...the ability to sail well to weather is not skeg related...
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Old 24-06-2016, 03:35   #239
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Re: Skeg or Spade?

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Originally Posted by neilpride View Post
As far i know there is a bunch of good clasic boats with skegs performing upwind or to weather like freaking trains....i dont get the point ...the ability to sail well to weather is not skeg related...
If that were true, we would see skegs on race boats. But the last skeg on a race boat disappeared decades ago.

Actually there are very clear and very objective reasons why spade rudders work so much better upwind. There is no controversy about it among boat designers. It doesn't mean you can't go upwind at all with a skeg rudder -- it's just that it's quite a bit less efficient. Very much like a full keel -- we all know classic full keel boats which go like freight trains (Jolie Brise!), but you don't see full keels on race boats, do you?


Spade rudders are of no benefit when sailing off the wind, though, which is why most cruisers don't really care. That's because -- like an airplane's vertical stabilizer -- there's no angle of attack in normal conditions.

The rudder does need an angle of attack, however, when sailing upwind -- just like an airplanes horizontal stabilizer. That's why practically all large airplanes have movable horizontal stabilizers, even if they also have elevators. That's because if you operate an elevator continuously to produce lift to trim the plane, you create a lot of drag with the skeg-rudder type configuration. So modern large aircraft move the whole stabilizer for that purpose, and use elevators (if they even have them) only for maneuvering.

This is very much how sailboat rudders are used -- turning, and producing lift upwind, are somewhat different functions. Actually there's no reason why you couldn't build a sailboat rudder like an airplane's horizontal stabilizer -- the whole rudder moves within say 5 or 6 degrees, and anything more than that, you use a separate movable surface (like a skeg rudder) at the end. That would probably have a few advantages over any of the rudder types we actually have -- probably better stall resistance, better feel, and easier to make really strong. But I guess this would probably be too complicated and expensive to be worthwhile.
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Old 24-06-2016, 03:38   #240
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Re: Skeg or Spade?

It seems to me this is a hill of beans. The measurable improvement to the cruising yachtsman has not be demonstrated to me at least. And it seems to me lift will cause the stern to move to lee assuming it's present (lift).

Not having seen the Oyster required support at the lower end... because you are turning a simply supported beam into a cantilever.
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