As promised in the other thread with offshore in its name, heres a idea I’ve been playing with. My main aim is to produce a boat that can be sailed for long distances at a fast pace, mostly reaching and offwind. A light displacement planeing design is what I’ve gone for, but with the provision of putting 2.4kg of water ballast in either quarter of the hull to keep the thing stuck down when over-powered (i feel a canting keel would be too power hungry, water ballast just needs a pump to throw it about, and then once a valve is closed it’ll stay there. I belive most model canting keel systems use the motor to lock the keel out. also you can just ditch the water ballast if the wind dies). I haven’t decided on a rig yet, but I think a fairly low aspect squaretop una rig with an assymetric kite would suit it well, just gotta suss out how to make it work. Once thats done I’ll play with foils, wich should be fairly conventional, but with a lighter bulb than would be expected on a boat this size.
first, i am no technician at all! but i like the idea of the pump and using water as a ballast…sounds nice.
just a thought, using a pump is nice…but, well i use a pump for fun in my rescue tug and to throw water outside …i need a 7.2 volt NiCd battery…maybe a bit heavy for a yacht…sure the pump i use is kind of powerfull…so i was wondering, what kind of pump would you use?..light pump…pumping takes time but setup light…motor+batt
or “heavy” pump…throwing water in no time, but heavy…
I put this link up in the other offshore forum but the section was flooded with usless information and I don’t believe anybody cought it. I am posting it again so if you don’t wanna see something you have already seen I am sorry
Matthew glad you did this-I’m sure Chad will help keep this on topic: technical considerations more or less only, right?
At any rate you are misinformd about the canting keel: it uses very little current when maxed out or stopped at any point! At least on my design. I think if you look at an analysis of the stability using a canting keel(19-22" strut) you’ll find that you gain far more from the canting keel than you would from the water ballast.The disadvantage is that you would need some form of daggerboard or centerboard or forward foil as well.
You should plan on using a 7.2 volt battery -maybe lithium- since the water pump will do better on that voltage and the spinnaker winch needs it; the Guyatt winches come with a built in regulator so you plug the battery into the winch and the winch supplies 5 volts to the receiver. Or you can use the regulator I use to supply 6 volts to the receiver.
More later…
Wis; I think because the boat is not gonna need to tack all that often, a small lightwight pump could be used, without much loss.
Doug; it might be very little current for a canting keel, but water should take none! Also downwind the keel would need to be moved back, which can be done I know but how???. And again you cant ditch some of the keel weight in light wind…
The canting mast mechanism that i have been designing uses a cam mounted to a servo. At the “tip” of the cam lobe is a tube that slides along the mast base (the mast pivots at the deck). When this system is at max travel, the cam lobe is oriented so that a line drawn from the “tip” of the lobe through the servo shaft is perpendicular to the mast. Thus, the force of the mast trying to center itself produces no torque on the servo. This allows the servo to “hold” the mast without actually consuming any power.
This same system could be used to actuate a canting keel. Thus when the keel cant was maxed out, the servo would not use any power. However at cants other than max, it would use some power. So if the design requirement for the boat is that you expect to have the keel at max cant (either one side or the other) most of the time, then you can get away with very low power consumption.
As far as a water pump goes, Tower Hobbies sells a pump made by RAM that is called the “boat saver”. It can operate on anything from 6 to 12 volts. It is designed with a water sensing switch that turns it on automatically, but I’m sure you could figure out a way to turn it on with the radio instead. I’m sure you could figure out a way to use this pump to pump water ballast around. You might need one for each side of the boat as I am guessing it is a one way pump. Either that or you will need some valves to direct the water.
I would think the tricky bit with water ballast would be getting the water into the boat from the outside. You would not want to have a big hole in the bottom of the boat.
For my canting mast boat, I am planning on having the rudder cant as well. The canting rudder will be in a narrow bay between two bulkheads. I am not planning on sealing this bay, so it will be wet an nominally flooded. Perhaps a wet bay like this could be used to allow water into the boat prior to pumping it to the high side tank.
As far as your design goes. It looks pretty good. Take a look at the bow sections of some of the full sized open 60 boats. You may want to add a bit more overhang to your design. This will also fix that nasty inflection in the topsides near the bow…
This is very similar to the design that Hal Robinson has built and he tells me it works really well.
Some details to help you sort out the picture: At the end of the cam lobe on the servo is a sliding sleeve that slides up and down the base of the mast. The mast pivots at the deck. The sliding sleeve pivots relative to the lobe.
This orientation is the most “torque balanced” configuration. The moment arm from the mast pivot to the tip of the cam is greatest when the mast is in the center of the travel. As the mast gets closer to max cant, this moment arm gets smaller, but the force vectors get more favorable, so the canting torque actually goes up. At max travel, the cam “locks off” such that the torque on the servo due to the mast trying to re-center is zero.
I played with the idea of turning the servo upside down relative to this configuration. That would give me more canting torque near max cant, but it would seriously hinder the canting torque near the middle of the throw.
Anyway, I think it is clear to see how this design could be turned upside down and used to actuate a canting keel.
This is a close approximation of the Righting Moment available from water or a canting keel.
With water you have to also assume at least some ballast in a bulb fixed or not. Just as an example if you had a 2.5" diameter tube at(weather side of the tube at the beam dimension) the maximum beam of the boat-- say about 16"-- then the CG of the tube filled with saltwater would be approz 10.75 " from the heeled center of buoyancy. The filled tube would weigh 3.32lb.'s and the Righting Arm would be 10.75" for a maximum righting moment from the water of 2.9 ft lbs plus the RM from say a 2.6lb bulb on the fin of about 1.3 lb for a total RM of 4.2 ft.lb.'s with a total ballast of 6lb.'s.
Now if you used 6 pounds of lead at the end of a 19" strut and canted it 55 degrees plus at least 20 degrees of boat heel the approximate RM due to the canting keel would be: 10.75 ft. lb.s.
Both examples use six pounds of ballast yet the canting keel develops 2.5 times the righting moment of the water ballast/ballast bulb combo!
There would be no advantage to the water ballast in this type of boat even in light air or downwind because, like a scow or Open 60 this boat will be faster when heeled; if you dump the water ballast in light air the boat is still sitting flat though with a canting keel the keel could be canted to leeward to heel the boat.
Similarly this boat will probably carry a spinnaker which means you won’t want to dump much ballast off the wind at least at angles higher than 10 degrees from deaddownwind.
I think if you analyze it carefully you will find that the power to carry sail using a canting keel is far greater than with water ballast and that that advantage is much more important than the very few times you could dump water ballast. Coupled with the canting keels ability to heel the boat to reduce wetted surface in light air I don’t think you can beat it…
UPDATE: Matthew- didn’t see that you had posted a 740mm(29") beam for the boat; I used 16" above but even increasing it I think you would find the canting keel superior.
My personal opinion is that 740mm is way too much beam…
Doug, A few things; Firstly the idea behind this boat is to make a fast boat for mostly reaching and downwind courses. I think you find an open 60 off wind is fastest sailed flat, a bit like a skiff type boat, heel the thing and you won’t keep it in a straight line without using way too much rudder. The reason Ive gone so wide is mostly to help early planeing, like a widestyle windsurfer the idea is that the boat sits on the top of the water and the huge flat areas will give lots of lift at low speed and it will pop up on the plane in fairly light wind. When you consider a 2.5m formula windsurf boards are up to 1.7m wide, and they plane in 6 knots or less… ok, their sail area:weight ratio is pretty crazy, but we havent really talked abut rigs yet!
Rigwise the closest to what i have in my mind is this;
Now as you can see by the position of the moveable ballast on this boat, the weight needs to be a good way back, way back. Now i doubt you’d get a canting keel to do that.
Matthew, Simon Rogers canting keel system in Mini 6.5’s(full size) move 1.2 metrs(approx.) fore and aft-equivalent to 10.15" or 257mm in your boat; they are adjustable in both directions by hand from the cockpit using block and tackle.
A una rig makes using an asymetrical easy since you can use a non snagging boom like the Hoyt boom for the clew of the spin and a long automatically retracting pole for the tack-as shown in your picture. It will set and retract using only one Guyatt and no trim winch or a very small one since the sheet can be tied into the mainsheet winch.Gybing is instantaneous and simple.
Otherwise, an asymetric requires two Guyatts…
That would work great, the only prob being the chute would have to be a fair way back (like just infront of the mast), othewise it will fill with water faster than it can drain in waves and trip the boat up.
Matthew,on a model using a spinnaker in winds over about 8k you absolutel MUST have the angle of the halyard right or else the sail will not lift the bow: with a symetrical system the angle thru the pivot point of the poles(on my system) to the intersection of the halyard measured relative to the WATERLINE should be about 62. 5 degrees or less: less is better.An asymetric would tend to be less angle if set on a pole which you would want even if you angled the pole up; the symetric would be highly unlikely to ever catch any water even in big waves. A model must have vertical lift generated by the sail or it will pitchpole in stronger winds…
In my experience asymetrics give way more lift than a symetrical kite, the Tornado boys love the kite on the Tornado Sport 'cos it keeps the bows up so well, pitchpoles happen alot less now. I think as a rule of thumb the foot has to be half as long as the leech, and the kite must not bulge beyond the end of the pole at any point. Thinking again, im not all that keen on having the mainsheet and spin sheets on the same winch, as a good way of dumping power quick is to ‘rag’ the kite without letting off the main (its normaly undersheeted anyway in overpowered conditions) so the main keeps the boat moving fast as the gust passses. The other thing is a seperate sheet winch for the kite will you allow you to pump it, which is the best way to keep a kite like that trimmed.
The spinnaker system I use on my boats is entirely different than a normal big boat symetrical spinnaker system; it will go deaddownwind better than an asymetric but probably wouldn’t be as good as an asymetric on reach if both systems were used without a jib.
Used with a jib however the Hoyt-Lord System is likely to be close to if not equal with an asymetric on any angle and is way simpler than an asymetric with a jib.
Realy the only way to test this is to build two boats and test one against the other. I think an assymetric is the way to go, however, The only advantage to a symetrical kite is that you can barn door downwind, but then if you can carry an assymetic slightly higher and sail faster then I dont think its worth the complication, better to keep things simple and light and sail fast(and gybe more).
Do you know of anyone whos made a succesful carbon flexitop mast on a model? If it can be done you only need an on water ajustable downhaul on a big roach main and de-powering it would be easy.
Closest I’ve heard of is Bob Sterne’s Marblehead rig.(Viper?)
You really should try the rig concept I use with the bent back tip-excellent control and adjustabilty with upper and lower outhaul in all conditions and a superior planform-make one up and try it.Excellent gust response.Probably far better than a fully roached or “normal” squaretop or flex top rig. Better yet make up two small rigs and test against each other…
How exactly does your concept work? Ive seen the pics on your site but there not close up enough to really see whats happening. Can twist be adjusted by just one control line for on water control?
OK, how about this: LOA 60" ,Beam: 9", all up weight 15 lb, 9lb. in 24"(max extension) revolutionary telescoping(16"-24") 55 degree canting keel. Sail Area: upwind 1800 sq. in including a telescoping wing mast(reefable) and square top over rotating jib; 2800 sq. in. downwind with newly developed square head ASY/SYM spinnaker(rectangular planform high aspect LIFTING spinnaker); CBTF or newly developed TOP SECRET underwater lateral resistance when keel cants.
On board tv transmission for sail trim and instruments(one mile range).
Designed to be able to be configured for extraordinary upwind VMG or lightning downwind speed for minimum 20 mile distances in minimum 10k wind in almost any sea condition. Name: “Thunder ONE” Comments, Matthew and?
The telescoping mast and canting keel strut present some interesting challenges but nothing American ingenuity can’t solve! But what about the 9" beam and square head spinnaker?? Have you done any calcs yet on a waterballast system?
Flash: Skandia is the first offshore canting keel yacht to ever win the Sydney-Hobart first to finish! Saying the boat has a canting keel is using the term loosely: because of the peculiar Aussie rule the thing is limited to a static angle of heel of 10 degrees with the keel at max(legal) cant. Contrast that with a real canting keel static test of Maiden Hong Kong of over 37 degrees and around the same or more for Pyewackett!
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