Probably far from a new idea

[gonzo]

A divided boat can be an advantage. It would create watertight compartments.

 

[Southern Cross]

Righting moment.

Borrowing from others including Doug, could you solve righting moment with outboard foils that generate enough lift to counter sail pressure? I don't know the correct word?

But then am I just adding 2000lbs to a scaled down Hydroptere design?

I'm going to rule out the capsizing issue since it's not an issue with catamarans and tri's. Once they are over, it's over.

 

[Doug Lord]

I hope you've read some of the links I've provided. Heres another one about a boat that uses DSS(patented worldwide)-Dynamic Stability System- where a foil sticks out from the lee side of the boat and generates tremendous RM(righting moment). DSS combined with a "normal" fixed keel or another type of movable ballast( on-deck lead or people) allows a boat to have more sail area than it otherwise would in light air and allows it to develop the RM to use that SA(sail area) in heavier air. The boat-Quant 28-has a most impressive race record.
http://www.boatdesign.net/forums/sailboats/quant-28-foil-assist-keelboat-dss-38421.html

 

[Doug Lord]

Would there be any advantage to dagger boards that could turn changing the angle of attack, doubling, say, as a steering mechanism? One placed forward and the other aft.

The dagger board could slide into a chamber that is fixed through the deck angled to be vertical when the boat is at optimum heel, like the daggers on the IMOCA, only they could turn through 40 degrees more or less?

==========
Google "CBTF"(Canting Ballast Twin Foil) which is a patented system that has a forward "rudder" and an aft rudder to provide the lateral resistance for a canting keel boat. It has two methods of steering that can be used simultaneously: "Collective" in which both rudders are turned the same direction to zero out leeway or to move to weather in a tactical situation, "Normal" in which the rudders turn opposite directions for steering.
-----
Just a note:
1) Angle of incidence refers to the angle between a foil and a reference on the boat-like a static waterline or the boats centerline. It is normally used when referring to foil angles because the frame of reference remains the same,
2) Angle of attack refers to the angle of the foil with respect to the flow around it. This angle can change frequently while sailing.
======
Illustrations: L=Angle of Attack, Right =Angle of incidence-in this case with reference to the longitudinal axis of an airplane.

 

[Skyak]

It's all been done, but that doesn't mean that it is not of value.

The thing you seem to be missing is that righting moment is not a single value, it needs to be considered at all angles of heel. Your original sketch has maximum righting as shown at 0 and declines to zero righting at -90 with your rig in the water and waves washing into your boat until it sinks.

The original open class offshore racers had large water ballast tanks on either side of widened boats. This was in addition to bulbs on the end of long keels. The reason they still had keel bulbs was for secondary and ultimate stability. After some deaths, rules were modified to add stability and recovery requirements that limit the internal ballast shifting. Since then the canting keel has become the winning ballast system for open class monohulls.

About internal ballast shifting -it is discouraged by most if not all rating regimes. It doesn't win against canting keel in open classes due to stability/safety rules. It isn't offered on production fast cruisers, but that might just be due to the fact that the market is not proven -yet.

There are some wide keel boats that depend on heavy crew for initial stability. The Viper class comes to mind. And it seems that all the most popular new one designs are ultralight with comically small bulbs that are lighter than the crew needed to sail in even modest wind. I think that water ballast tanks and a high speed pump setup would be a popular addition if for no other reason than increased wind range/shorthanded high performance sailing.

My idea is to design a small fast cruiser that has a rotating storage/accommodations setup so that I can carry all the little luxuries and still sail faster than the racers. The cockpit would be a circle and beneath the seats the storage would be able to rotate 180. Then things would be packed based on density -batteries, water tanks, anchor, and generator on the dense side, sails, bumpers, and canvas on the light side. The way I figure it, I should be able to add about the entire accommodation weight times ~0.3 beam. So a 24 ft by 9ft beam trailer sailor with 1000 lb of equipment would be adding 3000 ft lbs of righting.

 

[Southern Cross]

Doug,

Isn't it crazy how ideas populate with the spread of information. I had never seen the twin foil idea yet I seemed to be moving towards the same conclusions. Makes me think that there is some sort of evolutionary process behind it. Something in the coincidence. Anyway.

The Swiss boat I had seen before and and I think I remember someone was trying to develop the same application to be installed on existing boats.

I am going to read the links more thoroughly and maybe try to come up with some sketches.

I'm still not completely discouraged.

 

[gonzo]

Similar problems often get similar solutions. The history of technology throughout the world shows that.

 

[Southern Cross]

P.S. I'm getting hooked. How can I put foils on my O30?

 

[Doug Lord]

Doug,

I'm still not completely discouraged.

=======================
You shouldn't be ,even remotely, discouraged. You've got a lot more to learn and to study, you've got people trying to help you. But most of all I hope you have the determination to go ahead regardless of little bumps in the road. New development is not easy- it is very, very demanding but whether one idea or a combination of ideas is the final "answer" or if there is no answer and
you find this particular idea not worth the time and trouble you will have learned a lot. The most important skill you can develop is the ability to focus and take one step at a time. Good Luck!

 

[FAST FRED]

While water or diesel tanks to change CG might work on a flyweight it was unsucessfyl on our cruiser. DL 333

A Lone Gull II blown up to 28lwl . 33loa, 28lwl 10.6boa 16500lbs. disp.

3- 35G tanks per side with bladders so either diesel or water could be loaded.

With one side full of water , the other empty the change is about 2 deg in heeling.

With a 40% ballast ratio and a long full keel, no difference in sailing can be observed .

BUT having large multiple use tankage does help in cruising.

 

[Southern Cross]

I used to have an S&S designed 24', shoal draft with a center board.

LWL: 19'
Disp: 4250 lbs
Ballast: 1650 lbs
BD: 38.8%
DL: 276
Draft: 2.83
SA: 295 sq'
Sa/D: 18.04

The centerboard while aiding in upwind performance added little to ballast and lateral stability at most points of sail. Some owners rarely used it. In fact, one owner who sailed from California to Tahiti and back never used it all.

Because of slack bilges it was one of those boats that was tender initially, but once healed at 15 - 20 degrees it would hold steady. I never once got the rail in. Once we were fully loaded, 2 adults and 2 kids and all our gear and food for a weeks holiday on the Island. Early in the evening the wind piped up to 25knts gusting to 30 - 35 knts. I switched up the 110 to a 95 but never needed a reef in the main. The stars were out. The kids slept soundly. What a night!

Granted the keel ran maybe 2/3 the length of the LOA, the lead ballast was encased in the layered-up glass starting from the base of the hull to 2.83' away from the bottom of the hull.

My point.

If you could take that sail "power" and fix it to a low drag, low displacement hull, something that weighs a 1/2 to 2/3 of the original weight, take the lead ballast and swing it up to windward, replace lateral resistance from the keel to dagger boards, hull form and foils ....

I was watching the video of Speed Dream's trial run. With the keel flying out of the water it still took 3 guys on the rail hiking out to keep it at the designed point of heel. Balance? Too much SA? Too much sail aloft?

Also, I hate to be a naysayer, I really hope Speed Dream works, but a telescoping keel with how much in the bulb? The loads a large confused sea can generate are terrific. I'm still often surprised by how much force a little 3' wave produces when body surfing.

 

[Southern Cross]

My point.

If you could take that sail "power" and fix it to a low drag, low displacement hull, something that weighs a 1/2 to 2/3 of the original weight, take the lead ballast and swing it up to windward, replace lateral resistance from the keel to dagger boards, hull form and foils ....

Add to this a wing...hey isn't that something like a moth?

 

[Southern Cross]

Is there a "Dummies Guide to Boat Design"?

 

[Leo Lazauskas]

Is there a "Dummies Guide to Boat Design"?

You are here.

 

[Southern Cross]

Well, I have come up with some of the same conclusions you all probably knew. Mostly the amount of lead needed for any serious ballast would take up a great deal of interior volume.

So, I started to think along the lines of Doug's ideas about foils but trying to keep it looking like a monohull. We should print T-shirts saying"Save the Monohull".

In keeping with the thread about using certain parts of the brain, I did some sketches. They're just sketches... And I don't have any formal training.

In one of the sketches I thought about using twin dagger boards that swing 180 degrees to become foils. The pivot point would need some sort of bulb to minimize drag. Also, ideally the dagger board would need an elastic skin, such as carbon impregnated with silicone, so that when it curves up to 90 degrees it would provide a truer foiling shape.

Notice that while the lee board could be used to foil and improve righting moment, the windward board could be angled at 90 degrees to the water surface to provide additional directional stability.

I suppose ballast could be attached at the pivot points in the shape of a bulb. The idea could also be applied to a Canting Keel.

Any thoughts would be appreciated...