[Chris 249]

Does anyone here know whether it would be more effective to "cant" ballast in the air, rather than in the water?

How would a yacht go with the ballast sliding on a crossbeam? It would be sort of like the sliding seat we use on Canoes. The penalty of tea-bagging a seat is much less than the penalty for dipping a wing, because the seat has a wedge-shaped underbody that allows it to plane across the water at speed, and it has buoyancy at low speeds. It gives you time to react. You also have no problem with the lee wing dragging.

The ballast would still be well to windward, but you wouldn't have the hydro drag of the keel and bulb (although there is the aero drag of the beam).

The advantage over a "conven tional" wing boat is generally more effective beam, plus for offshore sailing the ballast is lead, not bodies.

I know it's a looooooooong way from being a new idea, but so are most ideas. I can see lots of problems, but how many are insoluble?

I still don't know why you'd both with a slider or canter setup in a mono (if speed's what's important, go multi) but would it work?

[Phil]

Chris,weight and windage would be the difficult thing,aside from the awkwardness of having something extra on the deck to clomb over.

[Doug Lord]

Chris, I've done several radio controlled prototypes using a "Trapeze Power Ballast System" that simulates the function of a crew on a trapeze. On rc models they are extremely difficult to sail without some form of ballast in the keel. It appears that a combination of sliding on-deck system and canting keel may be very fast in models.
On fullsize boats I think it would be unseaworthy. A while back the editor featured or should I say showed a picture of a French boat that has two canting keels : one on each side.The windward keel is sticking straight to windward-parallel to the water!
Instead of getting the ballast out of the water my feeling is that getting the boat out might produce better ,faster and safer results: use a canting keel for stability and a retractable hydrofoil forward of the canting strut and a foil on the rudder-just two foils and a canting keel--I'd bet it would be really fast.

[Pete M]

chris, after the mechanics are worked out...some kind of material transfer technology would be involved...and assuming you didn't have to build some kind of monster truss bridge...I think I would be happy to trade the areo drag for hydro drag

[Ned]

then comes the joy of getting the weight from one end of the pry to the other.

[Chris 249]

Yeah, getting it from side to side MAY be a problem but whether it's more of a problem than moving a keel or water is a Q. There's a lot of plumbing in the other solutions, and maybe there are already lots of sestablished systems (hydraulics, travellers) to move loads quickly on deck. I think a Herreshoff had ballast on rails back in the sandbagger days, under the deck.

Windage would be low, and one of the things about sliding seats is that because they need no vertical clearance to leeward, the girder depth can be greater than with wings AFAIK.

I started doodling, drawing up a minimalist small slider sportsboat". A 28' Canoe/moth inspired simple box hull, long and skinny, easy to build in ply. Like the IC and Moth, it has a pintail, to stop transom drag and nosediving.

Thing is, when you draw a boat like that and suspend weight out to one side, you realise you've basically a big-rig International 110! There's nothing new. Actually a canting keel was one of the first-ever sailboat patents.

It's just a daydream. There's some small link with modern wings, 'cause although the Moths had them for decades, and the Kiwi R Class boys were double trapping from wings in '74, the wings really broken through with Richard Court about '78 when he made a giant sliding frame for his 18. The sliding frame, though, was too much for a 3 man skiff racing on short courses and the thing only slide 2'6" so there was no width benefit v twin wings.

[Big Show]

I'll take the canting keel thanks. There has to be a finite point/size where it becomes impractical having no lead regardless of what you save on displacement. How long can the boat be and how large of a sail plan can you put on it with no righting moment and actually manage to negotiate a race course?

There has to be a point where the size and power of the boat would be unmanageable even for a large crew of, say…, the best 18 skiff sailors it would take to sail it. If anyone knows what it’s like to sail an overpowered boat at breakneck speeds with nothing but themselves to keep the boat up, it’s those guys.

If you ever hope to go uphill you’re going to need a foil for lateral resistance. If you’re going to build, for example, a turboed 86 foot boat, lead at the end of the foil is going to help stabilize the boat if a puff or wave isn’t sailed/trimmed/driven optimally. Let’s face it, a turboed 86 foot boat would be b-e-y-o-n-d manageable without lead.

All the better if you can fully cant the ballast from side to side in 10 odd seconds. Imagine how fast we'll be able to do it in a production 25, 30 or 40 footer...

I think we’re seeing a whole new realm open up when one considers the performance capabilities of monohulls with canting keels.

[Ned]

Chris, this thing is starting to sound alot like Slingshot, the Proa with twin pods, one on each end of the 'iako. Now that we can use stored energy to shift ballast, zoom, you can use the winching to accelerate the boat through the tack.

[Chris 249]

You're right, it is very Slingshot-ish in concept - and probably about as practical (which is not very, AFAIK!). Or like a proa, which makes one wonder (as always) why guys who beliedve speed is all would build a mono...

Hey Big Show, I wasn't thinking of having no ballast in the hull. It would have a nice little foil with lead, it's just that most of the sail carrying power would come from the slider. There could be fewer problems in sliding than swining, and because you're not restricted to a narrow foil, you may be able to get a longer span and shift the ballast further out. That would mean less weight for the same righting moment. Furthermore, the flotation and planing lift of the slider help support the ballast when the boat heels to far to windward and that makes a huge difference in action. The planked International Canoe is still unparalleled upwind, even by the singlehanded skiffs (and that's info from the guys who sell and sail the skiffs).

When a canter is caught in a lull and heels to windward, the lead still develops righting moment - excessive righting moment that's trying to capsize the boa tto windward. With a slider, the slide would become immersed when the boat gets caught aback or in a lull, and then the lift generated by the slide would help reduce the effect of rhe ballast and keep the boat on a more even keel (allowing for both boats to have teh same RM). I think....

I have no intention of building one of these (well, I suppose I already have a 50% version of a 34 footer in the shape of my IC) but I may work out some numbers to see how effective it could be.

It would have almost no use at all, of course. Most of our beer can races are in more restricted waters where manouvrability is everything.

Frank Bethwaite tested the strange proas and captive kite rigs you see in his book in front of our old home. Their performance showed all who saw them how vital all-roound performance was, compared to theoretical BS that assumes perfect conditions. He did end up with the HSP which was an absolute hoot and showed how effective a very wide boat with minimal weight can be.

It also showed that you need very little planing surface to provide a surprising amount of support when the boat heels to windward and you tea-bag. If the underside of the wing (or float) is shaped well, it skips along the surface and the boat stays fast, which keeps the apparent up. On something like a skiff, when the wing hits the water the drag causes the boat to stop, and apparent wind drops radically and makes the windward heel worse. Of course this is just what comes out of my head at 1.30 am when I can't sleep.....

[Chris 249]

You're right, it is very Slingshot-ish in concept - and probably about as practical (which is not very, AFAIK!). Or like a proa, which makes one wonder (as always) why guys who beliedve speed is all would build a mono...

Hey Big Show, I wasn't thinking of having no ballast in the hull. It would have a nice little foil with lead, it's just that most of the sail carrying power would come from the slider. There could be fewer problems in sliding than swining, and because you're not restricted to a narrow foil, you may be able to get a longer span and shift the ballast further out. That would mean less weight for the same righting moment. Furthermore, the flotation and planing lift of the slider help support the ballast when the boat heels to far to windward and that makes a huge difference in action. The planked International Canoe is still unparalleled upwind, even by the singlehanded skiffs (and that's info from the guys who sell and sail the skiffs).

When a canter is caught in a lull and heels to windward, the lead still develops righting moment - excessive righting moment that's trying to capsize the boa tto windward. With a slider, the slide would become immersed when the boat gets caught aback or in a lull, and then the lift generated by the slide would help reduce the effect of rhe ballast and keep the boat on a more even keel (allowing for both boats to have teh same RM). I think....

I have no intention of building one of these (well, I suppose I already have a 50% version of a 34 footer in the shape of my IC) but I may work out some numbers to see how effective it could be.

It would have almost no use at all, of course. Most of our beer can races are in more restricted waters where manouvrability is everything.

Frank Bethwaite tested the strange proas and captive kite rigs you see in his book in front of our old home. Their performance showed all who saw them how vital all-roound performance was, compared to theoretical BS that assumes perfect conditions. He did end up with the HSP which was an absolute hoot and showed how effective a very wide boat with minimal weight can be.

It also showed that you need very little planing surface to provide a surprising amount of support when the boat heels to windward and you tea-bag. If the underside of the wing (or float) is shaped well, it skips along the surface and the boat stays fast, which keeps the apparent up. On something like a skiff, when the wing hits the water the drag causes the boat to stop, and apparent wind drops radically and makes the windward heel worse. Of course this is just what comes out of my head at 1.30 am when I can't sleep.....

[jeff E of the GWN]

Its ideas like this that make this site sailing anarchy
thyre was talk awhile back ab0ut a sailing anarchy20 footer ( the 30 footer as we know ..a concept has all but died) a sliding seat of some type for live or ded ballast i thought would be great.
i have ,thought of installing a sliding bracket down below in my own boat so i could slide some kind of weight around while i was sailing shorthanded, not racing of course PHRF would not like that.
it would be a hell of alot easier building something like this above water rather than the a narrow foil and bulb required for below water use.

[Steve Clark]

Chris, although "lead weighs less in the water than it does in the air" the real thing you are doing is shifting the center of gravity away from the center of bouyancy. It really doesn't matter in which medium the shift is accomplished. It gets more complicated as you start to model the dynamics and things like roll inertia start to play a part in gust responce etc.

Otherwise those Uffa enthusiasts in us have always wanted to build the Brunhild (sp?) the famous two person IC. Done with the modern stuff this should be a wildly fast ride.
SHC

[Ned]

Steve Clark, on Mar 9 2004, 06:17 PM, said:

Otherwise those Uffa enthusiasts in us have always wanted to build the Brunhild (sp?) the famous two person IC. Done with the modern stuff this should be a wildly fast ride.
SHC

sounds kind of like the tandem sailboards

[Trevor B]

Tandem Sailboards- now that was a hoot!
Double duck jibes at twenty knots... lots of fun.

[Chris 249]

Steve, I wasn't referring to "lead weigh(ing) less in the water than it does in the air", just the fact that the buoyant and dynamic lift of the "slider" itself would help to support X % of hte ballast weight when the boat was caught aback or heeled to windward - but you know all that stuff much better than I do. I was just musing dumb ideas while staying up late to hassle UK designers over the 'phone.

By the way, did you ever sail Bethwaite's HSP? I often wonder whether it was not close to the ultimate Canoe in many aspects; pointy, very narrow, very fast. I don't think the little planing floats did significantly more to keep the whole deal right way up than an IC's planks does.

You'd know our 2 man Payne Mortlock Canoes still exist, but they are much fatter than a modern interpretation would be, and even with the kite they are slower than a 505 or IC.

[Chris 249]

Down South - there's interesting stuff from Smith, thanks for the link.

Tut the problem is that when Frank Bethwaite spent about 10 years trying to get Smith's theories working in real life, he failed. Frank's boats inspired by Smith were sometimes fast for about 100m (and from memory even that was rare) but then they'd just stop or become completely uncontrollable. They were tested in front of my house when I was a kid. They were interesting, but unworkable.

The work did end up inspiring the rather wonderful Bethwaite HSP, but that's a very different beast from Smith's theoretical constructs. And I don't even know if Smith was the first to use inclined rigs on models. The Kiwis Peter and Graham Mander, who won 18' skiff worlds and Olympic gold, had inclined-rig models in the 1940s!

I've always been amused by boffins with test rigs set up on old canoes and such, and the breathless reports of tests sessions in 5 knots of wind. There's a wonderful contrast between the fact that propeller heads always search for the Holy Grail of lift of inclined rigs, while in "real life" those who can incline their rigs (windsurfers) try to incline them as little as possible. Ask the Olympic windsurfers and their coaches, you don't want a sail that lifts you up, you want a sail that pushes you forward!!

Re Guest's "Actually, the mass of the lead is the same in water or air, which is the important thing"

Yep, I know. The thing is that lead on a "slider" would be carried in a bouyant structure (the slider arm) thast provides buoyancy and dynamic lift. When the lead and the slider hit the water, the dynamic lift and the buoyancy of the slider STRUCTURE (it would be maybe 3' fore-and-aft on a 25 footer, and extend say 10' from the gunwale) would provide maybe (very, very roughly) 150 kg of buoyancy. That would reduce the boat's tendency to capsize to windward.

The same sort of thing happens to a Pacific flying proa, but their "ballast" is the weight of the windward float (which is normally above the water) and they use the volume buoyancy of the float to prevent capsizing to windward. A slider would use the dynamic and volume buoyancy of the slider arm, and some normal lead in the keel.

re "How about tracks following the hull for inside." Been done, Herreshoff about 1850!

[JimC]

Steve Clark, on Mar 9 2004, 06:17 PM, said:

those Uffa enthusiasts in us have always wanted to build the Brunhild (sp?) the famous two person IC. Done with the modern stuff this should be a wildly fast ride.
SHC

Wasn't Brynhild something of a disappointment speedwise though? In Sail and Powe Uffa mentions he'd measured 16.something knots in a single seat canoe but only 15 in the two hander.

Still be a thing to do though...

[julian]

Chris, the mass of lead is NOT the same in water or air! In air it has a density of about 11.3, in water it has a density of 10.3. The water pushes everything up! So you are ahead with the lead out of the water.

[MonkeyBoy]

Quote

Chris, the mass of lead is NOT the same in water or air! In air it has a density of about 11.3, in water it has a density of 10.3. The water pushes everything up! So you are ahead with the lead out of the water.

This is rubbish. Density of an object is Mass/Volume

Mass is measured in Kg which is a universal measurement a 1kg mass of lead still has a mass of 1 kg on the moon. What changes is the weight (should be in Newtons) a measure of the force exerted between 2 bodies.

The MASS of an object is the same everywhere. It is the weight you are talking about which changes dependant on the amount of bouyancy provided by the medium in which it is suspended.