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wallcfa

Centerboard Performance

132 posts in this topic

post-32003-0-10914100-1383879733_thumb.jpg

Ted Hood's Robin; the One tonner. Probably the winningest of Ted's centerboard designs since 1959. A little left alone these days.

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Great! We're state of the art 1959. My uneducated eye sees a lot of that bottom in my boat.

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That twin centerboard MacLear & Harris got me thinking about the old triangular centerboards. Most of them were just flat sided plates so doubly inefficient, but what if one made one with an efficient foil shape? It would never be as efficient as a high aspect board, but with a composite trunk that paralleled it's shape, there would never be that open slot or open cable to cause drag.

 

Be kind Bob, I'm the guy who figures out how strong stuff needs to be and how to actually build it. Not the guy who does all the flow studies and comes up with the fast shapes.

 

It would only be an efficient foil at one angle, like all the way down...and as you swung it up and down the foil and the effective slot shape would change.

 

True, but I think you could do better than flat plate, neglecting the problem of the width of the case and the slot.

 

Absolutely agree. I was just pointing out the compromise. A good NACA foil at any point would likely be better than a flat plate.

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Do all centerboards rattle? If we leave the board down at anchor to damp the rolling it clunks as the boat rolls, but with it up the boat can develop an unsettling rapid roll.

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attachicon.gifRobin.jpg

Ted Hood's Robin; the One tonner. Probably the winningest of Ted's centerboard designs since 1959. A little left alone these days.

Wow! They really knew how to build them back then; look at that cabin, it's built like a brick shit house!

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attachicon.gifRobin.jpg

Ted Hood's Robin; the One tonner. Probably the winningest of Ted's centerboard designs since 1959. A little left alone these days.

Wow! They really knew how to build them back then; look at that cabin, it's built like a brick shit house!

Roar of laughter. Brill.

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That brick cabin trunk was simply a rule aberation in order to get the minimum righting moment allowance, CGF, i.e an artifact of rated speed.

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I thought the expression was "on the bricks". I think that boat has it backwards.

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I have a Precision 23. I love my little boat modest yacht. It has a CB and it is a total pig upwind. A dog. I'm sure this is due to some other design features, as well.

 

However, something like 25% of the Chesapeake Bay is 6' or under. I can't think of a better boat for gunk holing around here. We slither up creeks to some secret spots that other boats can't. But I had to make peace that I will never race it-- not even in "casual" phrf wendsnight beer can stuff. Just too damn slow upwind. On the other hand, the little guy really really goes downwind with the CB up. I put in a mast track and rigged a sym. spinnaker. We haul ass down wind.

 

I think it's all about doing a harms/benefit analysis about where you are planning to cruise and if losing upwind performance is worth the more shallow draft.

 

I've gotten into the dreaded Meredith Creek near Annapolis. Which has a 1' bar in front and a tiny slot to squeak through.

 

U02auouViThy89wrhssCFn6SnDAMumcE1zr_CZXX

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That twin centerboard MacLear & Harris got me thinking about the old triangular centerboards. Most of them were just flat sided plates so doubly inefficient, but what if one made one with an efficient foil shape? It would never be as efficient as a high aspect board, but with a composite trunk that paralleled it's shape, there would never be that open slot or open cable to cause drag.

 

Be kind Bob, I'm the guy who figures out how strong stuff needs to be and how to actually build it. Not the guy who does all the flow studies and comes up with the fast shapes.

 

It would only be an efficient foil at one angle, like all the way down...and as you swung it up and down the foil and the effective slot shape would change.

 

True, but I think you could do better than flat plate, neglecting the problem of the width of the case and the slot.

 

Absolutely agree. I was just pointing out the compromise. A good NACA foil at any point would likely be better than a flat plate.

I made my original statement off the top of my head. After the comments, I decided to actually model the board in SolidWorks and look at how it worked out.

 

I picked a 6% foil with max thickness at 45%. The foil was "borrowed" from a centerboard system I engineered some 5+ years ago for another designer. I made the slot match the board shape at full down so obviously there it was a good fit. From there, the thickness is always a little thinner so the board always clears at any point of lift.

 

Yes, as the board is raised, the foil section shape rotates around the local max thickness. Always a foil and no different a shape change than a deep skinny board partly raised. The clearance in the slot gets greater forward as the board lifts, but in all cases of partial lift, it is better (or at least no worse) than the deep board. With the board fully raised, the slot is the same due to leading edge taper.

 

I don't have any CFD capabilities to see what the lift/drag is.

 

To answer some other questions of boards banging around.......

The Night Wind 35 that, I mentioned in another post, used a set of hard rubber discs. as shims around the pin area. That took nearly all of the slop out.

The centerboard system that I mention above in this post had the pin in a bracket system that fastened from the bottom of the keel. This was to make it easy to remove for service when in a travel lift and still have a positive stop to limit the board to its upwind sailing position if the cable broke. The inside of the brackets have Acetal shims to keep the board snug and are replaceable for wear over time.

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I have a Precision 23. I love my little boat modest yacht. It has a CB and it is a total pig upwind. A dog. I'm sure this is due to some other design features, as well.

 

However, something like 25% of the Chesapeake Bay is 6' or under. I can't think of a better boat for gunk holing around here. We slither up creeks to some secret spots that other boats can't. But I had to make peace that I will never race it-- not even in "casual" phrf wendsnight beer can stuff. Just too damn slow upwind. On the other hand, the little guy really really goes downwind with the CB up. I put in a mast track and rigged a sym. spinnaker. We haul ass down wind.

 

I think it's all about doing a harms/benefit analysis about where you are planning to cruise and if losing upwind performance is worth the more shallow draft.

 

I've gotten into the dreaded Meredith Creek near Annapolis. Which has a 1' bar in front and a tiny slot to squeak through.

There is one on Lake Monroe that does OK under Portsmouth so it might be that the PHRF committee doesn't like you or the class splits are not equitable. OTOH, his main competition is a Hunter 23, an S2 6.7, a Pearson 26, a MacGregor 21, and a Catalina 25. The Hunter 23 is one of the few that actually has a wing keel / centerboard combination.

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attachicon.gifRobin.jpg

Ted Hood's Robin; the One tonner. Probably the winningest of Ted's centerboard designs since 1959. A little left alone these days.

Wow! They really knew how to build them back then; look at that cabin, it's built like a brick shit house!

 

 

Like THIS??

 

brick2jpg_sml.jpg

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attachicon.gifRobin.jpg

Ted Hood's Robin; the One tonner. Probably the winningest of Ted's centerboard designs since 1959. A little left alone these days.

Wow! They really knew how to build them back then; look at that cabin, it's built like a brick shit house!

 

 

Like THIS??

 

brick2jpg_sml.jpg

 

Take it to the Ugly Boat Admiration Thread! (Funny pic!)

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I have a Precision 23. I love my little boat modest yacht. It has a CB and it is a total pig upwind. A dog. I'm sure this is due to some other design features, as well.

 

However, something like 25% of the Chesapeake Bay is 6' or under. I can't think of a better boat for gunk holing around here. We slither up creeks to some secret spots that other boats can't. But I had to make peace that I will never race it-- not even in "casual" phrf wendsnight beer can stuff. Just too damn slow upwind. On the other hand, the little guy really really goes downwind with the CB up. I put in a mast track and rigged a sym. spinnaker. We haul ass down wind.

 

I think it's all about doing a harms/benefit analysis about where you are planning to cruise and if losing upwind performance is worth the more shallow draft.

 

I've gotten into the dreaded Meredith Creek near Annapolis. Which has a 1' bar in front and a tiny slot to squeak through.

 

U02auouViThy89wrhssCFn6SnDAMumcE1zr_CZXX

 

Nice! When cruising who motors to weather anyways? That's what the engine is for! :D

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I have a Precision 23. I love my little boat modest yacht. It has a CB and it is a total pig upwind. A dog. I'm sure this is due to some other design features, as well.

 

However, something like 25% of the Chesapeake Bay is 6' or under. I can't think of a better boat for gunk holing around here. We slither up creeks to some secret spots that other boats can't. But I had to make peace that I will never race it-- not even in "casual" phrf wendsnight beer can stuff. Just too damn slow upwind. On the other hand, the little guy really really goes downwind with the CB up. I put in a mast track and rigged a sym. spinnaker. We haul ass down wind.

 

I think it's all about doing a harms/benefit analysis about where you are planning to cruise and if losing upwind performance is worth the more shallow draft.

 

I've gotten into the dreaded Meredith Creek near Annapolis. Which has a 1' bar in front and a tiny slot to squeak through.

 

U02auouViThy89wrhssCFn6SnDAMumcE1zr_CZXX

 

Nice! When cruising who motors to weather anyways? That's what the engine is for! :D

 

 

I have a Precision 23. I love my little boat modest yacht. It has a CB and it is a total pig upwind. A dog. I'm sure this is due to some other design features, as well.

 

However, something like 25% of the Chesapeake Bay is 6' or under. I can't think of a better boat for gunk holing around here. We slither up creeks to some secret spots that other boats can't. But I had to make peace that I will never race it-- not even in "casual" phrf wendsnight beer can stuff. Just too damn slow upwind. On the other hand, the little guy really really goes downwind with the CB up. I put in a mast track and rigged a sym. spinnaker. We haul ass down wind.

 

I think it's all about doing a harms/benefit analysis about where you are planning to cruise and if losing upwind performance is worth the more shallow draft.

 

I've gotten into the dreaded Meredith Creek near Annapolis. Which has a 1' bar in front and a tiny slot to squeak through.

 

U02auouViThy89wrhssCFn6SnDAMumcE1zr_CZXX

 

Nice! When cruising who motors to weather anyways? That's what the engine is for! :D

 

 

Ha! We been in there....

 

I dunno what it is with the Precisions, I suspect they told Jim Taylor they want a boat that is easy to build and easy to sell, and cared less about performance. They sail OK but it's a bummer to have a boat that looks fast but isn't. There just aren't many good trailerable options. You could always get a Santana 23!

 

FB- Doug

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That twin centerboard MacLear & Harris got me thinking about the old triangular centerboards. Most of them were just flat sided plates so doubly inefficient, but what if one made one with an efficient foil shape? It would never be as efficient as a high aspect board, but with a composite trunk that paralleled it's shape, there would never be that open slot or open cable to cause drag.

 

Be kind Bob, I'm the guy who figures out how strong stuff needs to be and how to actually build it. Not the guy who does all the flow studies and comes up with the fast shapes.

It would only be an efficient foil at one angle, like all the way down...and as you swung it up and down the foil and the effective slot shape would change.

True, but I think you could do better than flat plate, neglecting the problem of the width of the case and the slot.

Absolutely agree. I was just pointing out the compromise. A good NACA foil at any point would likely be better than a flat plate.

I made my original statement off the top of my head. After the comments, I decided to actually model the board in SolidWorks and look at how it worked out.

 

I picked a 6% foil with max thickness at 45%. The foil was "borrowed" from a centerboard system I engineered some 5+ years ago for another designer. I made the slot match the board shape at full down so obviously there it was a good fit. From there, the thickness is always a little thinner so the board always clears at any point of lift.

 

Yes, as the board is raised, the foil section shape rotates around the local max thickness. Always a foil and no different a shape change than a deep skinny board partly raised. The clearance in the slot gets greater forward as the board lifts, but in all cases of partial lift, it is better (or at least no worse) than the deep board. With the board fully raised, the slot is the same due to leading edge taper.

 

I don't have any CFD capabilities to see what the lift/drag is.

 

To answer some other questions of boards banging around.......

The Night Wind 35 that, I mentioned in another post, used a set of hard rubber discs. as shims around the pin area. That took nearly all of the slop out.

The centerboard system that I mention above in this post had the pin in a bracket system that fastened from the bottom of the keel. This was to make it easy to remove for service when in a travel lift and still have a positive stop to limit the board to its upwind sailing position if the cable broke. The inside of the brackets have Acetal shims to keep the board snug and are replaceable for wear over time.

We use nylon usually for the lift keel trailer sailers in Aus to stop board slop. Nice and slippery, and cheap.

Hold down pins are pretty handy if you are out in a bit more breeze than the boat can handle. There were a bunch of sonata 7 yrailerables that sunk in Aus after turtling and having their keel exit through the top of the case at high speed, taking a chunk of hull with them. Centerboards wouldn't have the same destructive force, but its one more thing you don't want to be worrying about when giving the masthead a wash. Hydraulic systems don't have this problem

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I have a Precision 23. I love my little boat modest yacht. It has a CB and it is a total pig upwind. A dog. I'm sure this is due to some other design features, as well.

 

However, something like 25% of the Chesapeake Bay is 6' or under. I can't think of a better boat for gunk holing around here. We slither up creeks to some secret spots that other boats can't. But I had to make peace that I will never race it-- not even in "casual" phrf wendsnight beer can stuff. Just too damn slow upwind. On the other hand, the little guy really really goes downwind with the CB up. I put in a mast track and rigged a sym. spinnaker. We haul ass down wind.

 

I think it's all about doing a harms/benefit analysis about where you are planning to cruise and if losing upwind performance is worth the more shallow draft.

 

I've gotten into the dreaded Meredith Creek near Annapolis. Which has a 1' bar in front and a tiny slot to squeak through.

 

U02auouViThy89wrhssCFn6SnDAMumcE1zr_CZXX

 

Nice! When cruising who motors to weather anyways? That's what the engine is for! :D

 

>

I have a Precision 23. I love my little boat modest yacht. It has a CB and it is a total pig upwind. A dog. I'm sure this is due to some other design features, as well.

 

However, something like 25% of the Chesapeake Bay is 6' or under. I can't think of a better boat for gunk holing around here. We slither up creeks to some secret spots that other boats can't. But I had to make peace that I will never race it-- not even in "casual" phrf wendsnight beer can stuff. Just too damn slow upwind. On the other hand, the little guy really really goes downwind with the CB up. I put in a mast track and rigged a sym. spinnaker. We haul ass down wind.

 

I think it's all about doing a harms/benefit analysis about where you are planning to cruise and if losing upwind performance is worth the more shallow draft.

 

I've gotten into the dreaded Meredith Creek near Annapolis. Which has a 1' bar in front and a tiny slot to squeak through.

 

U02auouViThy89wrhssCFn6SnDAMumcE1zr_CZXX

 

Nice! When cruising who motors to weather anyways? That's what the engine is for! :D

 

 

Ha! We been in there....

 

I dunno what it is with the Precisions, I suspect they told Jim Taylor they want a boat that is easy to build and easy to sell, and cared less about performance.

 

 

They wanted the biggest, beamest cabin to fit on a regular trailer, me thinks. It is pretty damn cozy for a 23.5 boat. I don't have any complaints, really. It's well built and fairly stout, now that I've reinforced the rudder box with space age, a-lu-minium brackets.

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I have a Precision 23. I love my little boat modest yacht. It has a CB and it is a total pig upwind. A dog. I'm sure this is due to some other design features, as well.

 

However, something like 25% of the Chesapeake Bay is 6' or under. I can't think of a better boat for gunk holing around here. We slither up creeks to some secret spots that other boats can't. But I had to make peace that I will never race it-- not even in "casual" phrf wendsnight beer can stuff. Just too damn slow upwind. On the other hand, the little guy really really goes downwind with the CB up. I put in a mast track and rigged a sym. spinnaker. We haul ass down wind.

 

I think it's all about doing a harms/benefit analysis about where you are planning to cruise and if losing upwind performance is worth the more shallow draft.

 

I've gotten into the dreaded Meredith Creek near Annapolis. Which has a 1' bar in front and a tiny slot to squeak through.

 

U02auouViThy89wrhssCFn6SnDAMumcE1zr_CZXX

 

Nice! When cruising who motors to weather anyways? That's what the engine is for! :D

 

>

I have a Precision 23. I love my little boat modest yacht. It has a CB and it is a total pig upwind. A dog. I'm sure this is due to some other design features, as well.

 

However, something like 25% of the Chesapeake Bay is 6' or under. I can't think of a better boat for gunk holing around here. We slither up creeks to some secret spots that other boats can't. But I had to make peace that I will never race it-- not even in "casual" phrf wendsnight beer can stuff. Just too damn slow upwind. On the other hand, the little guy really really goes downwind with the CB up. I put in a mast track and rigged a sym. spinnaker. We haul ass down wind.

 

I think it's all about doing a harms/benefit analysis about where you are planning to cruise and if losing upwind performance is worth the more shallow draft.

 

I've gotten into the dreaded Meredith Creek near Annapolis. Which has a 1' bar in front and a tiny slot to squeak through.

 

U02auouViThy89wrhssCFn6SnDAMumcE1zr_CZXX

 

Nice! When cruising who motors to weather anyways? That's what the engine is for! :D

 

 

Ha! We been in there....

 

I dunno what it is with the Precisions, I suspect they told Jim Taylor they want a boat that is easy to build and easy to sell, and cared less about performance. They sail OK but it's a bummer to have a boat that looks fast but isn't. There just aren't many good trailerable options. You could always get a Santana 23!

 

FB- Doug

 

 

Or a First 235. Same LOA as the Prec, but more usable space inside. MUCH faster to boot.

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>

I have a Precision 23. I love my little boat modest yacht. It has a CB and it is a total pig upwind. A dog. I'm sure this is due to some other design features, as well.

 

However, something like 25% of the Chesapeake Bay is 6' or under. I can't think of a better boat for gunk holing around here. We slither up creeks to some secret spots that other boats can't. But I had to make peace that I will never race it-- not even in "casual" phrf wendsnight beer can stuff. Just too damn slow upwind. On the other hand, the little guy really really goes downwind with the CB up. I put in a mast track and rigged a sym. spinnaker. We haul ass down wind.

 

I think it's all about doing a harms/benefit analysis about where you are planning to cruise and if losing upwind performance is worth the more shallow draft.

 

I've gotten into the dreaded Meredith Creek near Annapolis. Which has a 1' bar in front and a tiny slot to squeak through.

 

U02auouViThy89wrhssCFn6SnDAMumcE1zr_CZXX

 

Nice! When cruising who motors to weather anyways? That's what the engine is for! :D

 

 

Ha! We been in there....

 

I dunno what it is with the Precisions, I suspect they told Jim Taylor they want a boat that is easy to build and easy to sell, and cared less about performance. They sail OK but it's a bummer to have a boat that looks fast but isn't. There just aren't many good trailerable options. You could always get a Santana 23!

 

FB- Doug

 

 

Or a First 235. Same LOA as the Prec, but more usable space inside. MUCH faster to boot.

 

Good friend of mine had one of those... unfortunately the details of making it trailerable seem to have escaped the French almost as badly as it escaped the Californians (on the S23). If it had a CB or lifting keel plus a workable tabernacle, it would be an awesome boat. Unbelievable combination of roominess & sailing ability.

 

FB- Doug

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>

I have a Precision 23. I love my little boat modest yacht. It has a CB and it is a total pig upwind. A dog. I'm sure this is due to some other design features, as well.

 

However, something like 25% of the Chesapeake Bay is 6' or under. I can't think of a better boat for gunk holing around here. We slither up creeks to some secret spots that other boats can't. But I had to make peace that I will never race it-- not even in "casual" phrf wendsnight beer can stuff. Just too damn slow upwind. On the other hand, the little guy really really goes downwind with the CB up. I put in a mast track and rigged a sym. spinnaker. We haul ass down wind.

 

I think it's all about doing a harms/benefit analysis about where you are planning to cruise and if losing upwind performance is worth the more shallow draft.

 

I've gotten into the dreaded Meredith Creek near Annapolis. Which has a 1' bar in front and a tiny slot to squeak through.

 

U02auouViThy89wrhssCFn6SnDAMumcE1zr_CZXX

 

Nice! When cruising who motors to weather anyways? That's what the engine is for! :D

 

 

Ha! We been in there....

 

I dunno what it is with the Precisions, I suspect they told Jim Taylor they want a boat that is easy to build and easy to sell, and cared less about performance. They sail OK but it's a bummer to have a boat that looks fast but isn't. There just aren't many good trailerable options. You could always get a Santana 23!

 

FB- Doug

 

 

Or a First 235. Same LOA as the Prec, but more usable space inside. MUCH faster to boot.

 

Good friend of mine had one of those... unfortunately the details of making it trailerable seem to have escaped the French almost as badly as it escaped the Californians (on the S23). If it had a CB or lifting keel plus a workable tabernacle, it would be an awesome boat. Unbelievable combination of roominess & sailing ability.

 

FB- Doug

 

Not on the French. In Europe 90% of these boats have the same lifting keel that BlueJ has... 6 foot draft down, 2 feet up. Finot and Beneteau have put it on tens of thousands of boats. That wing that my 235 had was a pure Beneteau USA invention. Never sold in Europe.

 

beneteau-first-235-405420201307665250555

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I'm not sure they ever used a chopper gun- the building of the boats might have been primitive by today's standards, but then they were there almost at the beginning. My guess is a Raven was a little long and low freeboard for the simple construction- might have wanted for a stringer or two.

 

I grew up sailing a Rhodes 18 they made. Last time I was there was in 2008 and the place was barely changed. (Just checked and it still looks the same in Google Earth). The Goodwins had resisted the call of condos and you could still walk through old boat houses untouched by decades. They did not charge me for docking my trimaran there for three days as they figured they knew me (Rhodes had been purchased in 1965).

 

I cherish that place and those people. I've always wanted a wooden Raven

the boat was early 50's f/g with no woven glass at all

so it could have been just matt layup

but I guessed choppergun as it looked like that textures

sure was eazy to knock a hole in

no gel coat ether just paint so it was eazy to see how she was built

 

I am sure they learned to build them better over the years

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That twin centerboard MacLear & Harris got me thinking about the old triangular centerboards. Most of them were just flat sided plates so doubly inefficient, but what if one made one with an efficient foil shape? It would never be as efficient as a high aspect board, but with a composite trunk that paralleled it's shape, there would never be that open slot or open cable to cause drag.

 

Be kind Bob, I'm the guy who figures out how strong stuff needs to be and how to actually build it. Not the guy who does all the flow studies and comes up with the fast shapes.

 

It would only be an efficient foil at one angle, like all the way down...and as you swung it up and down the foil and the effective slot shape would change.

 

True, but I think you could do better than flat plate, neglecting the problem of the width of the case and the slot.

 

Absolutely agree. I was just pointing out the compromise. A good NACA foil at any point would likely be better than a flat plate.

I made my original statement off the top of my head. After the comments, I decided to actually model the board in SolidWorks and look at how it worked out.

 

I picked a 6% foil with max thickness at 45%. The foil was "borrowed" from a centerboard system I engineered some 5+ years ago for another designer. I made the slot match the board shape at full down so obviously there it was a good fit. From there, the thickness is always a little thinner so the board always clears at any point of lift.

 

Yes, as the board is raised, the foil section shape rotates around the local max thickness. Always a foil and no different a shape change than a deep skinny board partly raised. The clearance in the slot gets greater forward as the board lifts, but in all cases of partial lift, it is better (or at least no worse) than the deep board. With the board fully raised, the slot is the same due to leading edge taper.

 

I don't have any CFD capabilities to see what the lift/drag is.

 

While I'm sure a NACA foiled pie board could be more efficient, I'm not convinced its worth it.

 

I think its worth pointing out that flat plate keels aren't terrible. They're not as efficient as a well formed keel with lifting foil sections, but there are plenty of weatherly, spirited sailboats with flat plate keels. The first example that comes to mind is the Star, which has, essentially, a flat plate with rounded edges for a keel. (It's possible that the modern Star class is fairing their keels, The difference in efficiency, especially in rougher conditions, would be worth it to such a competitive class.)

 

image001.jpgy4u7B2d.jpg

 

Would the Star have been better with a NACA foil keel? Probably, but she was designed 5 years before the National Advisory Committee for Aeronautics was even convened.

 

Also, off the top of my head, I see problems for the geometry. Foils sections arranged radially (so that it will retract with without a gap) will only be optimal from a fluid dynamics standpoint at the root, and quite bad at the tip. Foil sections which are arranged horizontally, will have thickness that varies along the radius, making it hard to get a close fit. Foxxy, I'd be curious to see a Screenshot of your CAD model if you feel like sharing, since I'm having a hard time visualizing your geometry from the description.

 

At any rate, the gain in performance will be slight most of the time, and probably not worth the expense to someone who's sailing a boat with a pie-board CB. It's a cool idea, though.

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I sailed Stars for a number of years and it is obvious that there has been a lot of time, thought and experimentation spent on development. The tolerances are quite loose and there are large variations in the shapes of leading and trailing edges, bulb shapes etc. Just take a look at your drawing VS the boat hanging in the slings. Some have even been CNC machined to get them exactly as wanted for certain conditions like rough or smooth water.

 

I can't show you a screen shot of my experiment because the shape used and the board I compared to belong to someone else. However, the foils were arranged horizontally, not radially. I mentioned that the foil shape of the partially lifted board. is not much different from that of a deep narrow board. The main benefit was from having the slot filled at full down which reduces the slop in the trunk. How much? I don't know.

 

I did a lifting keel with kelp cutter several years ago and, if you left the top off the trunk, there was a considerable up flow of water in a very close fitting trunk. Not so bad upwind, but when on plane.........

Even with a well sealed cap, there was a geyser from the kelp cutter tube when on plane so even that needs to be well sealed with shaft packing or something if it is inside the cabin.

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I sailed Stars for a number of years and it is obvious that there has been a lot of time, thought and experimentation spent on development. The tolerances are quite loose and there are large variations in the shapes of leading and trailing edges, bulb shapes etc. Just take a look at your drawing VS the boat hanging in the slings. Some have even been CNC machined to get them exactly as wanted for certain conditions like rough or smooth water.

 

Very interesting, is it common for boats to change out keel for different days of racing?

 

It's not altogether surprising, though, in such a competitive class there's ample payoff for that sort of thing. However, the class was able to establish itself as a fun and exciting boat with very unsophisticated foils, and old boats with flat plate keels will still be fun to sail, although not as fast as boats with better foils. One could certainly do a lot worse. Even full keeled boats, like 6 meters, which often have very little distinct keel stub, will sail well to windward. Generally, I think people overestimate the amount of "state of the art" required to make a boat fun and rewarding to sail.

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The Cal 20 is another class with a plate keel with a bulb. I own and race one and can say that it goes to weather decently and since it is one design racing who cares about the lack of a true foil. We fair the leading edge but that's about it.

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Or a First 235. Same LOA as the Prec, but more usable space inside. MUCH faster to boot.

 

Good friend of mine had one of those... unfortunately the details of making it trailerable seem to have escaped the French almost as badly as it escaped the Californians (on the S23). If it had a CB or lifting keel plus a workable tabernacle, it would be an awesome boat. Unbelievable combination of roominess & sailing ability.

 

FB- Doug

 

Not on the French. In Europe 90% of these boats have the same lifting keel that BlueJ has... 6 foot draft down, 2 feet up. Finot and Beneteau have put it on tens of thousands of boats. That wing that my 235 had was a pure Beneteau USA invention. Never sold in Europe.

 

beneteau-first-235-405420201307665250555

 

 

Y'know a number of people I respect have said good things about those French swing keels but they just seem like the worst form of liftable foil to me. It requires a highly loaded structure in the trunk, relatively sophisticated (and highly loaded) lifting gear, doesn't reduce draft by as much, is still outside the hull dragging in the water sailing down wind... just no thanks. It may be residual prejudice from the awful versions of the same idea by Venture & Catalina.

 

If you're going to all the trouble of an appendage that pulls in, have it pull -all- the way in. Boats are supposed to be female after all !!!

 

FB- Doug

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The other thing that always seemed like a design difficulty for those swing keels, is that the ballast moves longitudinally a fair amount when raised. I imagine these boats are fairly low ballast ratio boats to begin with, but still, that's a substantial percentage of the weight of your boat moving aft. Something that might be a pain to account for.

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I sailed Stars for a number of years and it is obvious that there has been a lot of time, thought and experimentation spent on development. The tolerances are quite loose and there are large variations in the shapes of leading and trailing edges, bulb shapes etc. Just take a look at your drawing VS the boat hanging in the slings. Some have even been CNC machined to get them exactly as wanted for certain conditions like rough or smooth water.

 

Very interesting, is it common for boats to change out keel for different days of racing?

 

It's not altogether surprising, though, in such a competitive class there's ample payoff for that sort of thing. However, the class was able to establish itself as a fun and exciting boat with very unsophisticated foils, and old boats with flat plate keels will still be fun to sail, although not as fast as boats with better foils. One could certainly do a lot worse. Even full keeled boats, like 6 meters, which often have very little distinct keel stub, will sail well to windward. Generally, I think people overestimate the amount of "state of the art" required to make a boat fun and rewarding to sail.

They don't change keels for different days of racing, but there were different optimizations for the different olympic and trial venues. There was also a shift in weight placement after the hiking harness was allowed and again after the crew weight limit got lighter. The biggest breakthrough in Stars was not in keels or hull shapes as much as in the ability to self bail well. The newer boats will empty themselves when sitting still and at any angle of heel. One had to keep my oldest Star footing upwind to bail and once you took a big wave, it was all over. The boat wouldn't bail itself until you went around the windward mark. The older boats are still quite competitive on lakes and sheltered harbors. But when you get to waves and chop, like on Biscayne Bay, your boat better bail well.

 

As long as the boats are relatively close in speed, class racing is fun whether the boats are new or old. The people in the class, not the boat, is what matters. At some clubs you see a class of boats that has been there for years and years. At others, there is a revolving door of boats being sailed.

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Or a First 235. Same LOA as the Prec, but more usable space inside. MUCH faster to boot.

 

Good friend of mine had one of those... unfortunately the details of making it trailerable seem to have escaped the French almost as badly as it escaped the Californians (on the S23). If it had a CB or lifting keel plus a workable tabernacle, it would be an awesome boat. Unbelievable combination of roominess & sailing ability.

 

FB- Doug

 

Not on the French. In Europe 90% of these boats have the same lifting keel that BlueJ has... 6 foot draft down, 2 feet up. Finot and Beneteau have put it on tens of thousands of boats. That wing that my 235 had was a pure Beneteau USA invention. Never sold in Europe.

 

beneteau-first-235-405420201307665250555

 

 

Y'know a number of people I respect have said good things about those French swing keels but they just seem like the worst form of liftable foil to me. It requires a highly loaded structure in the trunk, relatively sophisticated (and highly loaded) lifting gear, doesn't reduce draft by as much, is still outside the hull dragging in the water sailing down wind... just no thanks. It may be residual prejudice from the awful versions of the same idea by Venture & Catalina.

 

If you're going to all the trouble of an appendage that pulls in, have it pull -all- the way in. Boats are supposed to be female after all !!!

 

FB- Doug

Doug,

 

Let me help you out here! ;^)

 

First, this engineered keel system has NOTHING in common with the POS wire jobs that Catalina, Hunter, and Venture foisted on an ignorant American sailing public in the 70s and 80s. While introducing some complexity, the system is immensely strong, and allows a very deep draft with shoal anchoring and beaching capabilities.

 

It was never designed to be a ZERO draft solution. if you need to get into 6 inches of water, look elsewhere, but keep in mind that that capability chews up huge amounts of interior space for very little benefit.

 

Unlike cheap lifting board solutions like S2 7.9s, it is designed to be used ONLY when full down, just like a regular keel. As such, it assumes an NACA 631A012 profile in that position. In 8-14 knots of breeze, our 260 will out-point a J/24. And I can ramp launch it. We have sailed a Pogo 12.50 with the same designed keel. That boat is a class legal Class 40 and is the highest performance boat I've even been on. Highly stable with 10 feet of draft when sailing, but you can back the transom right up to a sand beach for lunch. Amazing.

 

quille_zps667b0669.jpg

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... ...

 

If you're going to all the trouble of an appendage that pulls in, have it pull -all- the way in. Boats are supposed to be female after all !!!

 

FB- Doug

 

Doug,

 

Let me help you out here! ;^)

 

First, this engineered keel system has NOTHING in common with the POS wire jobs that Catalina, Hunter, and Venture foisted on an ignorant American sailing public in the 70s and 80s. While introducing some complexity, the system is immensely strong, and allows a very deep draft with shoal anchoring and beaching capabilities.

 

It was never designed to be a ZERO draft solution. if you need to get into 6 inches of water, look elsewhere, but keep in mind that that capability chews up huge amounts of interior space for very little benefit.

 

Unlike cheap lifting board solutions like S2 7.9s, it is designed to be used ONLY when full down, just like a regular keel. As such, it assumes an NACA 631A012 profile in that position. In 8-14 knots of breeze, our 260 will out-point a J/24. And I can ramp launch it. We have sailed a Pogo 12.50 with the same designed keel. That boat is a class legal Class 40 and is the highest performance boat I've even been on. Highly stable with 10 feet of draft when sailing, but you can back the transom right up to a sand beach for lunch. Amazing.

 

I would really love to try out a Pogo. Another boat with a swing keel such as this is the Beneteau First Class 8 which is a super boat... still on my short list although less trailerable than I really need. OTOH they have their bad points: the structural footprint in the hull is very small, it needs to be perfectly built for both laminate & tolerance. They do swing weight farther aft than other configurations. It may be that the hydraulic ones are easier to maintain than the older/smaller screw/jack ones which I've seen be very troublesome (to be fair, all were long past their due date).

 

A good friend has a Ranger 23 FUN which has this keel. It's cast iron which is not an ideal material. The alignment & leeway forces are all 100% dependent on the pivot & bearings which were rather sloppily done by Ranger in it's corporate death throes. The screw/jack needs regular maintenance which it never gets because the only way to access it is to take a sawz-all to the keel back & top of the trunk.

 

But I admit none of that is the design's fault.

:rolleyes:

 

FB- Doug

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A good friend has a Ranger 23 FUN which has this keel. It's cast iron which is not an ideal material. The alignment & leeway forces are all 100% dependent on the pivot & bearings which were rather sloppily done by Ranger in it's corporate death throes. The screw/jack needs regular maintenance which it never gets because the only way to access it is to take a sawz-all to the keel back & top of the trunk.

 

But I admit none of that is the design's fault.

:rolleyes:

 

FB- Doug

 

In a slight defense of Ranger, the company was building the Fun exactly as Jeanneau dictated. All the keels, rigs and other bits came from France and were installed as received. If I remember correctly, you remove a U shaped cap on the back and the SS screw will simply back out of the bronze nut enough to add grease. Probably best done with the keel full down. Also If I recall correctly, the pin was glassed over and it would be pretty tough to remove it and drop the keel to re-paint it once the rust started. Not good there and other similar keels may have the same issues. Hard to tell from pictures and a concept sketch, but certainly worth checking out if you are going to buy a boat with one.

 

Really any of the swing keel boats are designed to sail with the keel down all the time and you only lift it to trailer or bring the boat into a shallow water dock. Drag and change of trim are not much of an issue in those cases so neither is a valid criticism. Most lifting keels are also designed to be sailed with the keel down all the time. Nobody lifts the keel while sailing a Melges, an SR, Viper, or most other sport boats.

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Doug,

 

For sure they are maintenance items. Benteau figures that the originals should last 15+ with regular care. They are easy (if costly) to replace with a diver, or the boat in a lift. One HUGE change Beneteau made to the design of the systems is turning the jack upside down. The early models had the screw attached to the keel, and the 'nut' twisted down via a crank from above. This worked fine but subjected the threads to salt water. Now its turned around, with the nut/pipe down and the screw out of the water. An annual greasing and the thing should last a lifetime. makes you wonder why they didn't do that from the start.

 

Regarding the structural footprint; there are several delrin 'pucks' attached to both sides of the round center part of the keel that rotates in the keel trunk. These pads hold the assembly snugly and bear part of the lateral loads on keel.

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