Design ideas for disabled sailors

[tspeer]

I've built and sailed a tail-controlled wing on a landyacht. it does, indeed, do a good job of gust alleviation. Too good, actually. When a gust hits, the rig automatically "sheets out" and the boat doesn't get the acceleration from the gust that a conventional rig does. This certainly makes it safe, but it's also frustrating for experienced sailors and racers.

We found that when given a choice, sailors invariably chose to fix the tail in position, using it as a balance surface. This reduced the moments on the rig so much that one could simply position the wing manually wherever desired. BTW, we implemented the controls so the pilot could control flap and tail separately, or use the flap and tail linked together so they moved in opposite directions in response to the pilot's control. The pilot could also vary the ratio of flap to tail deflection. And the configuration was such that the pilot could simply reach up and grab the tail to manhandle the rig.

It would be a good solution for a day sailer but not for a cruising boat. The inability to reef makes the wing highly problematic for cruising.

We like the Harry proa a lot for this purpose. Although I'm starting to lean toward the pure Atlantic proa. The main difference is the Atlantic has the rig on the windward hull while the Harry puts it on the leeward hull. The Atlantic's rig is thus much more at hand than the Harry's. And the inclination of the rig would be to leeward instead of to windward, which would make it more stable.

[wingsails]

Tail size can help the prob of too much weathervaning. We use a small tali and it takes longer to react so you still get some surge of power from the gust. Its mainly trial and error though for individual requirements. Reefing is done by lessening the tail angle to what is suitable, no problem at all.

[tspeer]

Like a wing, it's impossible to reduce the area of the wingmast any further once the sail is down. From what I've read, the racing skippers that have taken large-chord wingmasts offshore have come back saying, "Never again!"

I can't imagine taking a full wing offshore.

[SailDesign]

Tom,
Did you ever read John Walker's description of bringing PlaneSail (the trimaran) through a hurricane on his transAtlantic crossing?
Interesting.

Steve

[MalSmith]

Originally Posted by SailDesign

Tom,
Did you ever read John Walker's description of bringing PlaneSail (the trimaran) through a hurricane on his transAtlantic crossing?
Interesting.

Steve

Is the account on the net anywhere? I admit to being skeptical of using a full size solid wing in bad weather. It would need to be flutter free and very responsive to changes in wind direction when operating al low Cl to avoid getting bowled over.

Mal.

[MalSmith]

Originally Posted by tspeer

We like the Harry proa a lot for this purpose. Although I'm starting to lean toward the pure Atlantic proa. The main difference is the Atlantic has the rig on the windward hull while the Harry puts it on the leeward hull. The Atlantic's rig is thus much more at hand than the Harry's. And the inclination of the rig would be to leeward instead of to windward, which would make it more stable.

The problem with that idea (inclining the rig to leeward) is that two "trapeze" wires may be needed because the mainsail must pass over your head during a shunt. Would that be acceptable? You might be swapping wires right when you need it most. On the Mi6 (http://www.cybernautics.com.au/mi6.html) the mast is on the leeward side of the main hull. It may be better to hang a crane out from the hounds. The jib might still be a problem. Maybe a una rig would be better, but then you loose the advantages of the balanced rig.

Mal.

[tspeer]

Originally Posted by MalSmith

The problem with that idea (inclining the rig to leeward) is that two "trapeze" wires may be needed because the mainsail must pass over your head during a shunt. Would that be acceptable?

Yes, now that you mention shunting, our original concept was a Harry proa with rig inclined to windward. That would have the mainsail passing to leeward of the flying wires. When I composed the post, I was thinking of one of Dick Newick's proas and transposed the concept to an Atlantic proa to get the sails within closer reach and go with the more stable leeward tilt.

You're right - there is a definite conflict between the trapeze wires and an Atlantic configuration.

[wingsails]

I agree with sail design.
no I haven't been offshore ith a wing during a storm , but I have been on a 16ft tri ,on enclosed waters in a full on gale that wrecked several roofs and uprooted trees, and the feeling I got was of amazment of how stable the rig was. You cant be just general in remarks like this but have to consider each boat and rig and the conditions as a whole.
I am building a much larger boat and will be using 4 wing masts but the concept has been thought over completely over the last 10 years and still working on details but having been rescued from a conventional rig during a storm years its something that I will not take lightly.

Originally Posted by tspeer

Like a wing, it's impossible to reduce the area of the wingmast any further once the sail is down. From what I've read, the racing skippers that have taken large-chord wingmasts offshore have come back saying, "Never again!"

I can't imagine taking a full wing offshore.

[sharpii2]

Originally Posted by tspeer

Like a wing, it's impossible to reduce the area of the wingmast any further once the sail is down. From what I've read, the racing skippers that have taken large-chord wingmasts offshore have come back saying, "Never again!"

I can't imagine taking a full wing offshore.

Hi Tom:

I sympathize with your concerns. However, I think there is a notable difference between a wing mast and a wing sail. The difference is that one, at least as I understand the concept, has a tailplane atached to it and the other dosen't. The purpose of the tail plane is to keep the leading edge pointed into the wind. As with an airplane, the center of lift tends to be aft the maximum thickness of the foil. This, at least in airplanes, tends to make the wing want to nose over. The purpose of the tailplane is to exert opposite pressure to counteract this tendency. Because of the long lever arm of the fueselage, The tailplane size can be relatively modest in relation to the wing (it contributes nothing to lift).

With the wing sail equiped with an extend boom and a tailplane (much like an airplane standing on its wing tip) and a symetrical foil, the sail should always want to point directly into the wind and produce zero lift. A flap on the tailplane (much like the elevator an airplane) could then be used to produce an angle of attack sufficient to produce lift. In its 'neutral' condition, the only force left to contend with would be drag.

I have read in another thread that an airfoil shape produces one tenth the drag of a cylindrical shape of the same thickness. This seems highly counter intuitive and I have trouble believing it. But if it is true (and I would like to do an experiment to see if it is) then the wingsail, trimmed directly into the wind, should have less drag (maybe cosiderably so) than a bare mast!

Of course, there are a few assumptions here. One, that the sail does not flap or flutter at all. Two, that the airfoil design is optimal for the strongest wind it is likely to face (say 120 knots to be safe). And three, that the weight of this rig is not so much that it makes the center of gravity unacceptably high. If these three assumtions can be met, I see no theoretical reason why this rig could not work.

With the wing mast, I think you have a totaly different animal. Without a tailplane to counteract its tendency to nose over, It will then do just that. Once it has, it will then create drag. And the center of drag would be approximately the same place the center of lift was. This would cause it to angle back into the wind giving it lift again. The lift would then cause it to nose over once again setting up a vicious cycle which is refered to, in the airplane business, as flap flutter. Flap flutter can easily shake a wing to pieces in next to no time and is justly feared by most test pilots. (never again)

All that being said, I agree with you in being reluctant to take such a rig (wingsail w/tailplane) off shore. I would first mount a scaled down version on a dinghy and take it out on a small lake in full gale conditions (with a crash boat nearby). If it passed that test, my reluctance may then start to lessen.

I do believe that fear of the unknown serves an evolutionary (survival) purpose. Hehe.

Bob

[tspeer]

A good wing can have low drag - at zero lift. The problem is keeping the lift at zero.

I agree about the need to add a tail to a wingmast to stabilize it when the sail is struck. I've often considered a unit that would have a bar that extended ahead and behind the mast, with a molded clamshell to clamp it onto the mast. The aft end of the bar would have a crossmember that could be unfolded to deploy a kite-shaped tail. The forward end of the bar would have a weight to mass-balance the mast and improve its flutter stability. I've had a fluttering wingmast pitchpole me backwards when tacking a landyacht - more than once.

Here are three things to consider about a wing offshore: moment of inertia, wind gradient, and gust spectrum.

The mass and corresponding moment of inertia of a wing will affect the dynamics of the boat in a seaway. Most sailors endeavor to reduce weight aloft as much as possible. The added inertia of a wing will lower the natural frequency of the boat's motion and can increase the amplitude. A related issue is mass balance of the wing. If the center of gravity of the wing is not on the pivot axis, it will swing about in response to the boat's motion in waves. It will also be more prone to flutter if the c.g. is behind the pivot axis.

With gusts and swells (which shadow the bottom of the wing when in the trough), the top of the wing doesn't necessarily see the same wind as the bottom of the wing. So it becomes very difficult to keep all parts of the wing neutral. When you get lift on the wing, or any part of it, you get induced drag and have to deal with the lift force itself. With a soft sail, reefing not only reduces the sail area, it lowers the center of effort and reduces the linear size of the sail. A feathered wing doesn't have any of these characteristics.

Finally, one has to consider the gust spectrum and the required dynamics from the wing. The damping of the tail goes up by the square of the tail length. So for the same tail volume (area x moment arm), a small tail on a long arm has much more damping than a large tail on a small arm. You need to design the tail so that the natural frequency of the response of the wing is faster than the expected gust onset rates. Otherwise, the gust will load up the wing before it has a chance to feather and alleviate the gust.

This requires consideration of the static stability from the tail (which sets the tail volume), aerodynamic damping, and moment of inertia of the wing and tail. On our long-tailed landyacht wing, we noticed that the response was quite sluggish. I've wondered if this is one reason the Walker wings were so short-coupled.

[sharpii2]

Originally Posted by tspeer

A good wing can have low drag - at zero lift. The problem is keeping the lift at zero.

I agree about the need to add a tail to a wingmast to stabilize it when the sail is struck. I've often considered a unit that would have a bar that extended ahead and behind the mast, with a molded clamshell to clamp it onto the mast. The aft end of the bar would have a crossmember that could be unfolded to deploy a kite-shaped tail. The forward end of the bar would have a weight to mass-balance the mast and improve its flutter stability. I've had a fluttering wingmast pitchpole me backwards when tacking a landyacht - more than once.

Here are three things to consider about a wing offshore: moment of inertia, wind gradient, and gust spectrum.

The mass and corresponding moment of inertia of a wing will affect the dynamics of the boat in a seaway. Most sailors endeavor to reduce weight aloft as much as possible. The added inertia of a wing will lower the natural frequency of the boat's motion and can increase the amplitude. A related issue is mass balance of the wing. If the center of gravity of the wing is not on the pivot axis, it will swing about in response to the boat's motion in waves. It will also be more prone to flutter if the c.g. is behind the pivot axis.

With gusts and swells (which shadow the bottom of the wing when in the trough), the top of the wing doesn't necessarily see the same wind as the bottom of the wing. So it becomes very difficult to keep all parts of the wing neutral. When you get lift on the wing, or any part of it, you get induced drag and have to deal with the lift force itself. With a soft sail, reefing not only reduces the sail area, it lowers the center of effort and reduces the linear size of the sail. A feathered wing doesn't have any of these characteristics.

Finally, one has to consider the gust spectrum and the required dynamics from the wing. The damping of the tail goes up by the square of the tail length. So for the same tail volume (area x moment arm), a small tail on a long arm has much more damping than a large tail on a small arm. You need to design the tail so that the natural frequency of the response of the wing is faster than the expected gust onset rates. Otherwise, the gust will load up the wing before it has a chance to feather and alleviate the gust.

This requires consideration of the static stability from the tail (which sets the tail volume), aerodynamic damping, and moment of inertia of the wing and tail. On our long-tailed landyacht wing, we noticed that the response was quite sluggish. I've wondered if this is one reason the Walker wings were so short-coupled.

I agree with you on all counts. Reasons one and two may be why I only hear of these things on multihulls. I can imagine on a mono things could get mighty agravaing in sloppy conditons and mighty exciting in gale ones. Though not as exciting as one might think. The wind gradiants may actually do more to dampen roll than to create it. However, The almost inevitably high CGs on these things may do much to limit their sail areas. This could be to such an extent that this rig on a mono would be limited to only sail assists on displacement powerboats.
In that capacity it could be well worth trying.
I still would like to try it on an mono offshore cruising yacht and just see how it goes. Which brings to mind a "bare naked ladies" tune: If I had a million dollars.

Bob

[brian eiland]

I was rooting thru some old mags and ran across this ad with a good overhead shot of "Impossible Dream". Note the wheel chair accessible deck around the entire perimeter

And I don't believe this 'handicap subject on boats' has come up in a long time.

[Guillermo]

Just popping in to say hello to Nicolás, Fernando and Rafael. Good to see so many spanish NA's (or close to be) showing up together in these forums.

Nicolás,
at my office we are at the beginning of the process of developing an small recreational motor boat concept for disabled persons (just motor, not sail). I agree with betelgeuserdude one of the main challenges is getting the disabled persons on and out of the boat with as less help as possible.

Cheers.

[Nordic Cat]

I think that Toms idea sounds very promising, as well as the wingsail concept.

I definately think that a cat or a proa is the way to go. Enclosed is a picture from a british built boat that used to be called Baden-Powell. It was aquired by a Swedish organisation to take disabled people sailing, and is somewhere around Stockholm at present.

I will discuss this with my good friend, who fell of the plug of a cat he had designed, hit his head on the concrete floor in a very unlucky manner, and has been disabled since. He now only has limited use of his left arm, and impaired vision as well. He was one of the best sailors I have ever sailed with.
In good weather, I lift him on board my cat in his wheelchair, and tie it down to the side deck for a sail. Sometimes he helps with the sail trim using his good arm and his teeth, it's just great to see the light come on in his eyes again, and his smile! Maybe we need to get him a boat like the one Tom described?

Regards

Alan

[Nordic Cat]

Originally Posted by Guillermo

I agree with betelgeuserdude one of the main challenges is getting the disabled persons on and out of the boat with as less help as possible.

Cheers.

There are small hydraulic cranes available, and rigging them up for wireless control is pretty standard these days. Simpler manual versions are used to help disabled people in to bathtubs/swimming pools. If there is a helper available it would be easy and not too heavy to implement.

On a sailboat, a boom crane is easy to implement, add some bearings and in/out control lines...

Regards

Alan