16' Keel boat-high performance

I think it is related in the amount of balast one needs to go fast. Under water these 18' skiffs are pretty slim, the decks are very confusing. The rigs are enormous for such a short hull, and the ballast apart from the helm can be 400lbs and about 10' away from the roll axis, that's about 4000 ft`lb of righting moment.
In a tack at the hint of the helm this ballast moves very precisely and self adjust, it doesn't just swing from one stop to the other, or balance is thrown off and the whole thing capsizes.
2.4m are not very fast and things react slower. The faster you want to go the faster AND more precise adjustments and controls need to be, which for a 16-18' boat to do by one person it becomes TOO much. F16s (fighter jets) were very fast and capable of enormous forces of lift, acceleration, etc. The problem jets of that caliber have is control. They switched from manual mechanical/hydraulic controls to electronic controls that would over ride hand controls to limit human over reaction and abuse of its forces.
By no means do I want to dismiss the idea, it sounds very interesting and I hope it is tested out and evolved, but I have the sense that the systems required to control such a boat may weigh a bit themselves and the actual adjustment to be far more complicated to produce "speed".
I also feel uncomfortable with the idea of sitting "in" and low when a boat capsizes.

 

This boat idea of yours

Not to be contrary, here, as I feel the idea is a fun exercise of what-if's and the like.

But.... Are you going to be the self-insuring liability party for wheelchair dudes in this fancy speed demon of a boat?

I'm of the opinion that it is always cool to think of those who are less able than the average guy may be. There has to be a limit, though, to that largesse when it comes to the business of getting one of these guys or gals out from under the boat as it does its slow motion, maybe-gonna-right-itself, routine. Were the upside down righting calcs done with a paralyzed guy hanging under the boat entangled in the strings providing his own ballast against the fact?

I have to hope you know how difficult it can be to get out from under a boat in those types of conditions. Able bodied sailors sometimes don't do that move all too well, much less a person with dead legs. And that's where the insurance thing comes into play. That issue, more than any single other, is what makes this a what-if head game and not a real project in the, lets' go do it sense.

I do like the conceptualizing, though, and feel that there are a couple of other ideas that could come from the process.

Chris

 

I agree about the difficulty to be strapped in the middle of a hull while it capsizes being a hazzard for anyone. But when we are talking about racing machinery the insurance/liability is minimal. Think about all those race cars and race bikes out there that people have killed themselves on, manufacturers informed them of the high risks and they were willing to take them.
People have died from trapeze entanglements too though, and from being knocked unconcious by booms... etc. Still in the Olympics I didn't see any quick releases on the 49ers or crews wearing helmets!
A PHYSICALLY CHALLENGED racer with an appropriate vest can outswim most of us on this board.
The other issue I'm thinking about is what shape and how much resistance those wings will have when they will hit the water at high speed. Maybe I've misunderstood from reading the thread on how they will differ from a trimaran, but if their shape doesn't accomodate low friction they would act as an off balance brake that will spin the whole boat to leewards.

 

Sdb

The only value this boat would be to disabled people is if it IS self-righting not "maybe self righting". However,it does have the potential to be sailed at a lower all up weight if the self righting capability was eliminated in which case it would still be rightable by an able bodied crew.
The Bethwaite UD 18(lead assisted skiff) uses variable "lead assist" in a boat where the crew can sit in a chair that slides side to side(if I understand their publicity correctly). They ,apparently, have variable keel weights but they have no way to even APPROACH the RM of the SDB concept. But the idea is similar: to give an exciting ride to ablebodied and /or disabled people.
There are all sorts of answers relating to this concept that will only be understood by testing the actual boat; the potential is so great that it sure looks worthwhile to me.

 

"Maybe I've misunderstood from reading the thread on how they will differ from a trimaran, but if their shape doesn't accomodate low friction they would act as an off balance brake that will spin the whole boat to leewards."

Thats probably exactly what would happen, and it would make it harder to recover.

Another thing these pods would do is allow it to float inverted if it ever capsized.

I think the problem with this is the design spec.- "16' keel boat high performace". Okay that can be done, as compared to a 2.4 metre. But then Doug wants to make it comparable to to an Aussie 18. No way is that happening. A 16 footer with lead on it is not beating a way overpowered 18' skiff with 3 guys hiking way out on racks.

At the 16' range for keelboats, high performance would mean sailing upwind at 5-6 knots and downwind at the windspeed..maybe. I dont know of any keelboats that can currently do that at the 16 foot size.

Another question is, what is the demand for a boat like this?
Most disabled sailors who sail in the 2.4 metre fleet are happy with it, because they are simple, and competitive. Its like with R/C boats, make it go as fast as it can with as few buttons to push/levers to adjust/knobs to turn.

I think that in the event that the boat is not self righting, or could get caught with the ballast on the wrong side and capsize/sink, it should not be made or sold. A disabled sailor getting pinned underneath a boat and subsequently drowning would not be a good endorsement for this type of boat.

 

Liability???

I don't know Zerogara, maybe it's the translation of your being in Greece and I'm in the litigation happy nation of the the USA, but the last time I talked with the nice folks in the Yamaha legal department, they were up to their necks in lawsuits. The same is true for Honda, Suzuki and any other motorcycle company you want to name.

Now, many of these may be totally unfounded, but if you were a small-time boat producer, how many of them could you sustain before the insurance company just flat out tells you to take a hike? I am more than certain that this fictitious small-time boat maker is not cash funded like Honda is, so it's only a matter of time and good fortune before the string runs out and it's time to close the doors.

Reference: I was a motorcycle journalist/photographer for seven years and the liabilty issues of racing from that sport to the boating world events are very comparable. It doesn't really matter if you have a signed release or not. If you get named, it's going to cost you big money. If it costs you enough big money often enough, then you're now out of money.. or you're out of insurance to help pay the big money.

Either way, it's over.

Chris

 

18 vs SDB

You know, any boat can be a hazard if something breaks. I think if an SDB is designed well and built well it offers an extraordinary sailing experience.In model tests with SDB systems with and without buoyancy pods there have been no control issues when the wing contacts water even at high speed. It slows the boat down-less with a properly designed pod.Keep in mind that the wing pivots as well as slides side to side & fore and aft.
I don't know if any of you have sailed a real fast boat sitting down inside it but I've done it with a tri and being low and close to the water gives a significant increase in the sensation of speed.The idea of the SDB is to add self righting for disabled sailors to the equation-and to be easly rightable by one person w/o the selfrighting capability.
As to beating an Aussie 18: the only chance a boat like this would have is sailing with a full flying hydrofoil system and even then unless it had an unstayed, camber induced rig I doubt that it would. But that is another advantage of the SDB: it is well suited to using a bi-foil hydrofoil arrangement whether full flying or "foil assist". And the extraordinary efficiency of a well designed monofoiler is being amply demonstrated by the Moth.
Lots of room for experiment and development with this concept.
====================
As to work load sailing this boat with movable ballast and an asy spin: just look at the mini 6.5's and other singlehanded movable ballast boats. There may have to be some powered systems as,for instance ,on the Martin 16 but the current design has the capability to handle the extra weight ,in most cases, w/o exceeding the designed displacement.

 

Some small cats and tris use a boyancy "pod" on the mast head. Only if inverted in calm water will they stay inverted, but with the weight of a single crew member on one side the balance is thown off and the boat begins to right itself, "slowly". Doug's proposal is of the wings being able to move from side to side, maybe like a trimaran whose beams slide. So the balance is thrown off and there is a definite righting moment.
In windier choppier conditions the balance is usually thrown off by gusts and waves, so the boyancy aide on the mast head becomes much more effective.

So I think we can move off this "disadvantage". How would someone in the water now adjust the wings to aid rigting the boat up? The bigger he rig of a boat under water the more dumped the motion of righting is. If you have capsized a Laser imagine what it takes to recover a 150-250 sq.ft worth of sails under water.

I like the idea of trimarans very much, despite of their disadvantages, but I think it is something worth messing with in 30+' of hulls and not in dinghies.

How about hydrofoils at the ends of the wings instead of boyancy pods? They create lift without the capsized stability problem.

 

Hydrofoils

Zerogara, I think the best use of hydrofoils on a boat like this is probably for lift only and not stability. The foils are a lot more efficient if all they have to do is lift and by using them for lift only you can stay with the bi-foiler concept which is more efficient than three foils
because you have fewer surface penetrations and no induced drag caused by the RM. Which translates to early takeoff and relatively light air foiling.The disadvantage compared to boats like the Rave and Hobie Trifoiler is lower top end speed.

 

What I meant about stability was the lack of stability hydrofoils would have in a capsized situation. That is the kind of stability cats and tris have capsized that nobody wants.

 

sorry, sounds a bit crazy, like "pimp my laser"
why not?
take an old fiberglass laser (under U$S500) , give it a 100kg keel (another U$S150), some extra cabling on the mast(add U$S50) and you will even carry a spinnaker... enough fun for the buck?

 

Here is something I was working on a while ago - 4.5 metres and AC inspired, but buildable in a fortnight of evenings and weekends. Its pretty simple, stitch and glue ply sheathed in glass with a spruce mast hollowed using a router and reinforced on the sidewalls with carbon uni. Should come in at under £1000 and am aiming at two thirds of that if sails etc are home made. The idea is to sell plans soon, including SailCut files for home sail making. More expensive than the laser but should be quicker I hope. The keel and especially rudder arrangement may change to allow easier packing, but I like the efficiency and looks of having the rudder under the boat. The rig may be reduced slightly too, as its over 8m2 upwind at the moment...:?:

Andy

 

very nice (and fast) looking boat Andy.

 

16 or so

Nice looking , Andy. Any numbers to go with it? Have you considered any form of movable ballast? Will the boat be steered by the skippers feet?
Do you think the keel and rudder should be vertically retractable to allow sailing off a beach? Will the spin go thru an opening in the deck forward?

 

Hi Andy,
That is so like what I have been drawing.I have had one ready to build for a year now but other things keep getting in the way.
I think its a great concept.