The Dreadad Yaw

Is that when you get so drunk that you have no spit in the morning, and your tongue is stuck to the roof of your mouth?

I hate that.

Why must you always lower everything to your crass level? Have you no couth?

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I just love it when I can sound superior.

Yes. I have no couth.

...and you're welcome.

I'm drinking tonight because the professor died. We will never get off the island, and Mary Ann is still hot.

I know nothing about this, but a big honkin' rudder would seem to be a start.

What's a dreadad yaw?

Are you referring to the tendency of powerboats when not on a plane, to wander excessively in the direction and to have very imprecise feel to the steering?

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Or are you referring to a similar but somewhat more rhythmic (and therefor predictable) tendency for a sailboat running downwind (especially when close to dead downwind) to alter course as the force of waves attempts to position the boat perpendicular to the direction of wave travel (lowest energy would be hull low in a trough pointed down the trough) ?

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Or something else entirely?

Thanks for your reply, and thanks for all of the people who also replied.

I am mainly interested in monohull work type Power boats, such as fishboats, crewboats, offshore supply boats, patrol boats, which are required to work in undesirable weather.

Most of the responses were from sailors of sailboats, and multihull or foil types, which are not within my own experience.

The dreaded yaw was named by sea going captains who experienced first hand the yaw when running off large seas, which made steering impossible and in too many cases caused the hull to roll over.

Alphonsus Forgeron-

Yaw in a sail boat, motor boat, larger work boats and row boats is the same and handled in the same manner. The differences are in its effects.

In a sail boat the deeper keel acts as a stabilizer and the sails do somewhat the same depending upon the wind direction.

In smaller power boats such as outboards, whose throttle and motor can be control comparatively the response is relatively quick. These can adjust their speed and steer correctively to minimize the yaw on the boat.

Larger power boats (inboards) such as the fishing boats, crew boats, offshore supply boats, larger patrol boats, have the advantage of greater weight so the yaw must be greater to effect them but their steerage response and speed control is much slower. If the yaw is adversely affecting them, their options are fewer but can change course to minimize its effect.

Extremely large boats ships, ocean liners, naval cruiser and larger up to aircraft carriers very seldom are bothered by a yaw. If they start to yaw they usually have other problems which came before it.

All of these, with it being most effective in the smaller boats are to be extra cautious with the steering and the speed control. It is easier to travel at the speed of the waves if it is a following sea. Likewise the speed must be kept at exactly the same as the waves. The hardest to handle is if the waves are perpendicular to the direction of travel. All this takes acute awareness, outstanding steering and fast responsive speed control. Most of all it takes practice, practice, and more practice to become skilled at minimizing the effect of the yaw. This practice should be in boats similar or the same boat to be used in these sea conditions.

Bon Voyage.

Good Luck, Old Salt

truth is not a compromise-

Thank you for your reply. Based on my knowledge and experience and your reply I would make the comparison that we are both correct. Correct in what is said but each going different "depths" in our descriptions. My statements were not intended to instruct the reader in a detailed description of each possible situation but to give a general familiarization.

The differences and similarities of each type of boat and how yaw in general is handled, for each, were briefly discussed. I had no intention of going into the difference between the various hull designs within each type listed by the OP. As one can imagine, each different hull design/shape, the topside configuration and especially the person steering are all characteristics that need to be considered when determining how a boat/ship will handle a yaw. Combine that with the different characteristics of the wind, currents, tides, wave shape, heading and several other things must be considered. Add to that many minor items that will also affect the handling characteristics of each type of boat.

Yaw, no matter what type of boat/ship, each is handled in the same overall manner. This includes: an acute sense of awareness, skilled speed control; careful course direction and the constant evaluation of all conditions. Each boat/ship must have these items

I did not go into explicit details for each boat/ship because to do so would be volumes of information presenting an information overload to the OP. Also I very infrequently handle the larger boats/ships so, although I may have general knowledge on them, I do not have the experience that I would want to provide valid descriptions of yaw with them.

Had I felt an essay in yaw and each boat was requested by the OP, I would have directed him to other more descriptive and authoritative sources such as: Chapman's "Piloting, Seamanship, and Small Boat Handling"; Nigel Calder's "Cruising Handbook"; the "Annapolis Book of Seamanship" series; or other similar books. These are certainly more complete, accurate, and knowledgeable than I could ever be, even in my wildest dream. To take selective small portions of my short answer to the OP and going into extensive criticism of these selected parts is confusing to the OP or anyone else reading the reply. Also, the most important factor is the skills of the operator. What seems important to some may be incidental to others.

Although my answers were short for each size boat group, each statement is true under general conditions. Thank you for providing some more detailed information on some of the items. Hopefully with both the OP will better understand the what, how and why of "yaw".

Good Luck, Old Salt

Thanks for your reply. You seem to have been there, or well read on the problem.

I agree with your response.

I am trying to find a person(s) who is encountering the problem in their boat design, their boat hull, or in their frequent work in unclement weather. A team of wisemen would be not undesirable, but quite time consuming if based on discussion only.

I happened to run across this and thought you might find it helpful.

Well now you know why I sold it to the guy you bought it from for $1.

How much did you pay?

You can eliminate this almost completely by filling the hull with water....

Do you do helmsmanship lessons?

Truth is not a compromise-

There is at least one situation where yawing is desirable. Of my sailboats, the one that is the most fun in a stiff breeze is my sunfish, one of the first ones made of that model. I take it out sailing in a slightly protected and do some sailing there. One type of sailing that is very interesting and fun is to run as close as possible with the wind and with a wave chop slightly off of the direction of travel. This is a lot of fun especially when you try to compensate the yaw with the rudder and body weight.

To do this in a strictly technical manner can be quite challenging. To do it for fun and try to get as much yaw as possible, without changing your overall heading, is up higher on my list of adrenaline list than watching it being done. Watching can be a lot of fun but not as much as doing it yourself!

May the wind always fill your sails!

Good Luck, Old Salt

I sailed a lot as a teenager and it was a blast. I crewed for some larger boats, but I had the best times sailing small boats. My favorite was a race rigged coronado c-15. It was set up with twin-trapeze and a lot of sail area for its size. It would get up on a plane in just a moderate wind. It would hold several people if needed, but three was about all comfortably. It was best with two, and quite a handful solo. Downwind the Hobies and Prindles would be faster, but pretty much and course upwind that boat was faster. Dolphins would commonly swim with the boat, and often right under me on the trapeze.

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The reason I brought it up is because what you described reminded me of how fun that boat was on a broad reach when the waves were big surfing down the side and then powering up the next as the mast straightened up and caught more wind, there was definitely a particular rhythm where the boat would be making much better speed.

My experience is with powered workboats. Thanks for your input which could also be helpful for powerboats, but my keenest interest is in proper hull desgn as a major answer.

Mono-hulls equipped with hydrofoils have no appreciable yaw due to the hull being out of the water.

With any sailboat jibing, there are no problems associated with it. It is the uncontrolled jibe that is the dangerous one. Ever wonder why the boom is called the boom? Could be its effect on your head when the jibe is uncontrolled?

Another way to reduce yaw in a sailboat when running is to use a Genoa jib (jib is the smaller triangular sail in front of the mast, Genoa is a larger than the normal sized jib and sometimes called a jenny along with the main sail behind the mast. These are configured so that the jib is placed on one side of the boat and the main sail placed on the other side. This is usually referred to as "running wing on wing" (this sometimes looks similar to the wings on a bird) or some variation of that. If the boat is sailing directly with the wind and the waves and the sails are set to run wing on wing there is very little yaw in its performance. One thing it will do is pitch, the dipping and rising of the front/rear due to the waves following the boat or the waves in front of the boat.

The only set of sails that will grab more wind is a spinnaker and the mainsail; the parachute shaped one used instead of a jib.

Enjoy the yaw, it can be fun!

Good Luck, Old Salt

I agree, a jibe shouldn't be dangerous if intentional. I think unintentional jibes are where the boom got its name, from knocking unsuspecting crew overboard.

Mono-hulls equipped with hydrofoils are usually motor driven or relatively small according to the web pages I looked at, can you post details of larger Mono-hulls equipped with hydrofoils please?

I have never ever seen one myself....though the big Cats seem to be almost standard with foils on the Admirals Cup!! Fantastic....

You are obviously one of those sailing people who is worried about jibing, of course many people are and you are certainly not alone. Probably most if not all Monohull only sailors....Its not difficult to do properly when correctly learnt.

If you got a few years of intensive owner multi-hulling under your belt and then perhaps you will change your mind, especially with a good teacher, as I was lucky enough to have many years ago, sailing the English channel and the North Sea with all its weather problems.........Around Tasmania I am told its far more dangerous......nver sailed there and never done the Fastnet either, though I wanted to.....never got the time....

Unwanted jibing can also happen if you sail where there are sudden changes of wind direction and can be dangerous to any sailboat type, but in my personal experience around the UK/Europe, there are usually warnings of that possibility that should not be ignored...and sail reduced......

On a Multi-hull, they being far "stiffer" that a monohull, you need to be very aware, for example when the lee hull gets buried, or the main/opposite hull wants to lift for example...reduce sail, early rathe rthan later!!

The Genoa idea certainly works to a degree to my mind, but in the varied boats I have sailed, especially monohulls, not enough to allow any of my wives/girlfriends not to get queasy/uncomfortable.....OK for the men generally.

Its a "point" of sailing that I personally make a "point" of not using whenever possible.......just a few degrees "off" course ( witha big Genny!) usually solves it to a great degree, especially on Multihulls....and knowing correct jibing techniques helps of course for that!!!

Generally, a Multi-hull above 25 feet overall length in my experience, allows even cooking without gimbals, even when underway, except in the most extreme conditions for that size of hull.

I personally never ever saw a Multihull WITH gimbals.....but thats just me maybe....I am sure some where they have them.....

Hot cooking was something that I always left alone on trips of less than 12 hours in Monos if possible....or only with a VERY calm sea, seldom seen around the UK...I might be persuaded!!

"Most if not all monohull sailors' are certainly not ignorant about jibing, especially anyone who has been involved in any races.

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I think when when it comes to hydrofoils, it is sufficiently different from monohull or multihull sailing to be considered its own distinct thing.... to me, a hull means a part that is interacting with the water....in which case, hydrofoil sail boats become zerohulls.

Both those have the same number of hulls interacting with the water.

Andy Germany-

So good to hear from you again. I was not aware that you were such a proficient participant in the boating community.

The largest monohull with hydrofoils that I was able to find, although I haven't ridden on it, is a Pegasus class vessel, a PHM "Patrol, Hydrofoil, Missile". These were in service from 1977 to 1993 for the US Navy. These were constructed by Boeing, most often known for their airplanes. These units had a l.o.a of 132 ft, beam of 28.8 ft and a displacement of 241 tons. Their speeds were 12 knots hullborne and 48 knots foilborne. I once rode on a passenger ferry equipped with hydrofoils. Its length was somewhere around 60 ft loa but was taken out of service because of harbor flotsam damaging the hydrofoils. It was placed in service elsewhere.

http://en.wikipedia.org/wiki/Pegasus-class_hydrofoil

My interest in the larger races diminished when they went multi-hulled so I can't comment on them. My interest was in the monohulls such as Vim, Columbia, Courageous, Intrepid, Freedom, Sceptre and Anitra.

As with most sailors, I consider myself to be good, not an authority to everyone, not the best by any means or a reference about it to all. I'm a recreational sailor who particularly likes to sail. It is much more important to enjoy this hobby than it is to represent oneself as an expert at it. As such I never make presumptions about anyone's sailing skills or knowledge until I have talked with them and have sailed with them several times. This thread certainly shows that there are many good and knowledgeable sailors among the membership that know a lot about it and many other subjects and enjoy sailing even more.

Despite your comment that I am "obviously one of those sailing people who are worried about "jibing", I am not at the least worried about jibing or in fact any facet of sailing mono's or multi's. I don't know how that could have been construed from my previous answer. It is part of sailing and can be done safely and swiftly. It is those sailors who don't do it correctly and with sufficient notification to their crew that make it dangerous. It is no more dangerous than coming about on a close hauled reach, a very simple task. I have no worries about jibing, a maneuver I do fairly well and safely.

Although I have not owned a multi-hulled sailboat, I started sailing them around the time J F Kennedy was elected president. Most of my experience has been in Hobies but also some in larger lengths. A friend has a Hobie and we exchange our boats quite frequently. I guess that those years would count as sufficient experience to comment on them. I like monohulls and multihulls so therefore I guess I don't have to change my mind about which I like better. Both are fun.

Some people don't like sailing with a jenni so they sail with a 100% or that reefed. Personally I like the jenni and the spinnaker. My wife has found a liking towards the Jenni and prefers to sail with it, especially wing on wing. Since my 20' cabin sloop is equipped to be sailed single-handed she can get more fun out of it and I can rest or navigate with confidence. This sloop is one my father and I built from scratch when I was an adolescent. It is over 50 years old and still is still in like new, if not better, condition. This was definitely not a slap together boat. It was made with love, extraordinary skills and engineered to perfection. We still sail it every chance we get. If I have my preference I will sail it instead of the larger one.

Jibing is something that is part of sailing. It is easier to learn how to do it correctly and enjoy it than it is to fear it. Despite most of my sailing being in salt water protected somewhat by barrier islands I am considered by my friends to be a competent sailor under all but extreme hurricane conditions. That is how I got the nick-name of "Old Salt" from my friends. Many of them feel one transatlantic trip to England as a teenager in a 50' ketch, numerous coastal spelunking cruises and several Newport-Bermuda trips makes me more than a beginning novice. At least they enjoy sailing with me.

Good Luck, Old Salt

Maybe my question was not clear enough, my fault.

My badly phrased query was:-

"Mono-hulls equipped with hydrofoils are usually motor driven or relatively small according to the web pages I looked at, can you post details of larger Mono-hulls equipped with hydrofoils please?"

I meant large sailing ones......sorry that it was not that clear.

I guess by your answer you know of none too.

We have some large motorized ones here on the Rhine, its the only way to travel!! I did a long trip on the Rhine first in 1981 on such a boat, on an even bigger one in the late 60's between Hong Kong and Macao, really great!!! They still run even today!!

My apologies if I misunderstood your stand on Jibing......even one not anticipated should not find any part of the crew in its way....certainly all of many jibes I had were in small sailing dinghies when I was still learning. I started at 4 years old.....

The only time I ever got hit by a boom any size or type of sailing boat was when the boom lift/Halyard failed as I tightened the main sheet after securing at a buoy and dropping all sail in Dover Harbour, England!! IT HURT!! But having a thick skull (still do!!) saved me from worse!!!

On modern racing boats the crew have helmets on for good reasons, not just the boom either.

Surprise jibes should almost never happen, a boat crewed by amateurs may have a different take on that comment though!

All jibes need to be controlled and executed correctly, there is simply no other way to do it!! As you well know!!

All boats and aircraft will yaw. It is the nature of the beast. And the yaw has to be corrected using the rudder. My boat has a full deep keel and a large rudder and the vessel weighs 25 tonnes. But a big wave on a quarter or slamming into one or the other bow will cause it to yaw but that yaw is easily corrected. I have never thought the yaw to be dreadful.

A good fix is to not buy a mono-hull, but only multi-hulls (Cats or Tris) and then tack them downwind to beat the dreaded yaw),

Its also usually faster from A to B than actually heading straight from one to the other!!! With most multi-hulls that is. I cannot guarantee all though, old Piver designs will probably not be faster, but they won't yaw.....

Some modern high performance mono-hulls can also be tacked downwind and get there faster with less yaw as well.....but any mono-hull, not heading directly downwind will yaw less, but may lose time as the distance increases....

Due to the fact that each tack is actually a jibe when running, many mono-hull sailors "jibe" at the thought!!! They have sadly never learnt how to jibe in a safe and correct manner.....its only an accident when they do it and the boom slams from one side to the other, possibly damaging boat and crew......

It is actually a standard sailing manoeuver that can also be used to return quickly and directly to save a man overboard under many circumstances and needs to be properly learned and used when needed.....one of us would throw say a cap overboard and we had to recover it before it sank - good training.

So Alphonsus...... now that many have responded with excellent commentary, might you indulge the contributors here with that which you have found to...... "reduce or eliminate this hull design flaw, with some good results"? I would be most interested in some of your theory and proof of concept and maybe even a video on YouTube. Thanks for your contribution.

Neither you or any of the responses to your post have explained what a 'dreaded yaw' is. As I have said, all boats regardless of size and regardless of hull count will yaw. They, and aircraft, will also pitch, roll, heave, surge and sway. It comes with the territory. None of them should be 'dreaded'.

Don't confuse yaw with a broach which maybe considered 'dreaded' and can also be dangerous.

Oraka-

Very interesting comment you have presented. After goggling "Dreaded Yaw", conferring with a sailor, a power boater and "Chapman Piloting, Seamanship and Small Boat Handling", we see no basic difference between a "dreaded yaw" and a "yaw". The only difference between the two is not a technical difference but a relative difference. A yaw is a yaw as commonly known and a dreaded yaw is a yaw that is beyond your abilities to travel safely.

This relative situation would also apply to: pitch vs. dreaded pitch; roll vs. dreaded roll; heave vs. dreaded heave; surge vs. dreaded surge; or sway vs. dreaded surge. Dreaded anything is anything you fear and cannot control within your skills. What may be a dreaded thing to you may be well within my skills so I do not consider it to be dreaded. An example, although perhaps an over simplification, might be in wrestling. I enjoy "fun wrestling" with kids in my family. For me to do this with a collegiate heavy weight would certainly be dreaded wrestling.

Thank you for your reply and comments. I hope my reply has clarified this subject.

Good Luck, Old Salt

Old salt marine architects use the "dreaded yaw", as a dreaded condition all sailors would want to avoid, since the typical outcome results in the hull rotating over and in many cases a loss of life. The "non dreaded yaw" is typically a steering and speed adjustment which most experienced sailors handle without serious problem.

It is worthwhile mentioning that numerous books on the subject, don't provida an answer to eliminate yaw, since it still exists and is just as deadley.

Thanks for your input.

I have changed the title on my post as I do not accept that yaw, with a properly trained, competent & experienced crew, on a properly rigged and outfitted boat/ship of any sort is dangerous, as the (trained) crew if the yaw becomes unreasonable, react instantly without even the need for discussion. A short command from the wheel man/Captain will be enough......

I have to say that I personally (I am sure that a) I am not alone here or b) I am not the MOST experienced sailor on CR4 either), with about 50 years of mixed sailing experience on Monohull power, RN Warships, Monohull sailing boats, Catamarans and a few Trimarans, that all have demonstrated to some degree Yawing at some point of sailing, mostly downwind with a following sea.

The Tris and Cats that I sailed on were all far "quieter" and also could be tacked downwind to handle it really well, which we usually did. Most good multihulls make a far better speed and are usually at the destination before a direct, downwind course.

Do please remember, that sailing before the wind means that the boat will ALWAYS sail slower than the wind due to losses like water resistance for example. On a "reach", most (good) boats are faster.....but may not still "make good" on the wished course, as with the direct course.

Good Multis usually can make good/better, especially with a good steady strong wind of a speed that suits the boat concerned.....sailing on the crests with such a boat is fast and exhilarating experience.

I served in the RN on Frigates, subs, Aircraft Carriers and Destroyers, again all demonstrated some degree of Yaw when sailing at 90° to the wave movement, moving in the same direction as the waves - a following sea.

Older Diesel Subs (I never served on any atomic subs) on the surface can really get wobbly, but a minor course change cures all....

One Frigate (HMS Puma) could get quite uncomfortable with a measured 85° movement from side to side, so that we could partially walk on the bulkheads!, which was quickly reduced by letting the seas come on a stern quarter and running out the stabilizers...... I am talking about 30-40 foot Pacific waves by the way..........

The other ship in our company was an old WW2 destroyer, which had no "under deck" passages to get to the Galley from some of the accommodation aft, some of the crew hardly got fed for the 2 days of the storm.....they suffered badly from Yaw as those older ships were built for straight line speed in relatively calm water....

Here is an online copy of the log of HMS Caprice in 1968, check the entries for November 68, between the 10th and the 13th. I was on HMS Puma by the way:-

http://www.hmscaprice1968.org.uk/Capricepdfs/1968CalendarREVISED.pdf

All of the other RN vessels I served on reacted in a much reduced manner even though other than the Destroyer, they had no stabilizers.

Subs tend to dive when it gets really rough...........

Yaw was handled generally by the fact that we were able to increase speed over that of the waves. How much more I cannot say anymore....nor whether it was the absolute reason the problem was seriously reduced or did not happen, but we certainly believed it was!!

My point here is that for anyone with reasonable Ocean experience for the vessel concerned, yaw is not really a "problem". Its just part of life on the high seas......

It might be though for a rank amateur crew with no experienced person to assist/teach him/them, but only a complete idiot (I know, there are enough around!!), goes sailing without a full and proper certificate of competence for the type of sailing/motoring he is undertaking. EVER!!! NO BUTS!!!!

Due to the fact that many years ago, there was no requirement for such a Patent (Captains certificate) type document in the UK (I believe it has been changed since), I was caught out with a complete idiot as "Captain" on a yacht delivery (he was the Buyer), that nearly drowned both of us!!! My sailing colleague of many years who was selling the boat to him told me he was a good experienced sailor and that all I needed to do was crew!!!

His experience turned out to be ONLY ON SMALL DINGHYS!!!!!

Which my friend had neglected to mention!!!!!! DUUUUHHHHHH!

Not a yacht on the high seas around the UK.....

We were actually pushed backwards past a wreck buoy a few meters away, due to his stupidity. It was as big as a London Double Decker Bus, hissing up and down in 20 foot waves over a wreck that was marked as having no water over it at high tide.......before I took over the boat (Mutiny?).

He went below and sulked till I tied us up in Brightlingsea, UK......

Are there any other old sailors here who are afraid of the "DREADED" Yaw, or do you feel the same as I that proper training should handle this under "Normal Business"???

Also, can you give us your experiences in this area and how you have handled such situations, please?

Thanks in advance to all concerned.

You are right. In the right boat with well trained competent crew, yaw is not something that should be capable of inducing dread.

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That said, the OP seems to be asking because something in that set of requirements was missing. I'd venture that anyone worthy of the descriptor 'crusty' or even merely 'salty' has found themselves numerous times in situations that, despite initial appearances, turn out to be deficient in an important aspect of the criteria above. Ending up short handed, having something important damaged and unserviceable at sea, being forced into conditions that exceed the capability of the vessel to reliably handle. Dread isn't a helpful state to have induced, but it probably doesn't feel like a choice to those experiencing it. The OP's dread is undoubtedly real as it is undoubtedly for many people. I think requesting input from others concerning subject of dread is a good reaction.

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All in all, aside from thinking it would be better to take it a little easier on those confessing a dread, and a wildly different opinion about the relative value of monohull vs multihull sailing, we hold very similar views.

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Just to stir the pot a little though..... the following sentence of yours needs some additional conditions to be true:

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"....Do please remember, that sailing before the wind means that the boat will ALWAYS sail slower than the wind due to losses like water resistance for example....."

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It is actually quite possible to travel down wind, faster than the wind, powered by the wind alone. All examples proving the point have been of sailcars so far, but the possibility for accomplishing the same feat on water cannot be ruled out.

GA

Extremely good answer!

Thank you

Good Luck, Old Salt

Liked your post-

What do I need to qualify that sentence for? When the motor is also being used maybe.......? I personally have never sailed in a sailing boat that could sail faster than the wind, directly down wind.....

Read the second sentence here:-

http://en.wikipedia.org/wiki/Sailing_faster_than_the_wind

OK?

Furthermore, I was/am one of those sailors who likes to sail into a harbour (where allowed to, not all allow it nowadays) and dock without using an engine if at all possible.....its good practice.

But I am also sailor who goes on long trips with the fuel tank completely full!! (After a long winded (pun intended!) north sea crossing with very little wind, it took far, far longer than it should have done. We all got very tired. Motor/sailing should under those conditions should be considered/not be avoided, but we only took enough fuel for harbour manouvers.)

Yes, I think the sentence you linked is correct. I don't think it can be done with simple square sails perpendicular to the wind.

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However using set of rotating blades, a vehicle has been built that can go faster than the wind only using the wind directly down wind and directly upwind as well. Downwind, the blades act as a propeller driven by wheels in contact with the ground. Going upwind, the blades act as a turbine driving the wheels. Going from a land vehicle to watercraft would require a large prop to take the place of the wheels, and while that hasn't yet been done, in theory it could.

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I was really just baiting you a little, because I though it might interest you if you hadn't already heard of it.

The biggest problem is that a prop in water (or air) has a loss, it does not have a 100% grip on the water as a good wheel does on ground.

Plus, these systems can work on water, but in the event of a large change in wind direction and strength, this can overwhelm the hull they are attached to.....

"Furling" can be very difficult to achieve.....which is why such devices have remained in specialist hands and are not (yet) on every sailboat.......maybe one day.....

Even modern properly designed windmills on land demonstrate occasional problems with "shutting down" when wind speeds exceed design parameter......a boat on water is in an even more precarious position!!!

Here are a few prize examples:-

http://www.youtube.com/watch?v=NLInrjUtFGI

Luckily they were not in a boat design of any sort........

Yeah, the prop would have to be sizable, which in itself would present some problems to attaining high speed.

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I was going to say that wingsails also have problems with not being able to reef or furl. After watching the video you posted though, it makes clear the additional danger of spinning blades.

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The idea is intriguing though, even if just for RC scale...

Thats perfectly true and I am sure that many have fun making such things.....and trying them out!!

Thanks for your well thought out response to the earlier comment.

At the shipyard we did a prototype Special Operations Craft for the Seals.

It was a catamaran type, about 70 ft craft with with 3,000 HP motors with surface piercing props. Held I believe 20 Seals with a crew of 7. (SOC MARK V)

WE had taken it to FL for sea trials, and I received a call at home, at about 7:00 PM to return to work, and fab a rudder that was 6" longer, the sketches will be waiting for me there. BTW, our shipyard was in Wisconsin.

It seems that when they opened it up, with no passengers, it lifted right out of the water and danced like a flat pebble skipping across a calm pond.