Speed Dream 27 Prototype

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Ilan, did you read the web page I suggested-about the 60' monofoiler? You reference RM as one of the reasons a monohull can't beat a multihull. Are you familiar with Veal Heel? It's a technique that can only work on a monohull foiler and it adds up to 40% to the RM of the boat. It's one of the significant advantages of any monohull foiler that uses just two main foils. And thats one of the reasons the 11' Moth is faster than any other sailboat under 20'.
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Note the increase in righting arm with Veal Heel. If the crew is sailing the boat level he(she) can heel the boat up to 20-30 degrees and add RM w/o the crew moving relative to the boat. Same thing on a larger boat where movable ballast mostly replaces the crew for ballast.
click on images below for better detail:

 

It all comes down to drag and RM. The Moth is only faster than anything under 20ft because it's a foiler, that was an OD decision. If the I14 class decided to foil it'd be quicker than a Moth. If a 20ft cat class decided to foil it'd be faster than both of those.
Back to SD, as a 27ftr I can't see where he'll get enough RM to hold it down. I'd think on a boat that small that lower ballast weight, racks and crew weight would win.
Also can't figure out, with so little volume forward, how SD could go downhill in a breeze. Snorkels and periscopes I guess.

 

Here are some comments of Don Jones on canting keel design:
http://www.sailinganarchy.com/general/2006/vor_keeldeal.htm
Links to more articles and info concerning the failure on Skandia/Wild Thing can be found at:
https://sites.google.com/site/mgmorris3993/works-cited

Since the SpeedDream 27 is supposed to be a prototype of a larger boat I'm going to take this opportunity to publish my opinion that canting keels should be controlled my worm-gear type linear drives, not hydraulic rams, and not ropes or wires. In case of failure the mechanical advantage would remain, allowing the keel to be locked down or perhaps controlled with manual overrides. If I were Vlad looking to redesign the 27's keel canting mechanism my first stop would be the Edson website to see if their traditional worm-gear steering parts could be adapted.

Agree? Disagree?

As you know, Doug, I'm with Ilan on the ultimate speed potential of foiling monohulls. My thoughts appear at http://www.boatdesign.net/forums/sailboats/next-2016-so-americas-cup-ac-35-a-44996.html#post586588.

 

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I don't know whether or not a worm gear set up would be fast enough. I don't have an aversion to the system he has now ,once it's properly sorted. It's probably a lot lighter than the worm drive?
DSS could eliminate the requirement for a canting keel-which might be the best solution. But that would require a small fixed keel to assure righting.And depending on the characteristics of the boat upside down the keel might have to move to right the boat like on an Open 60.
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As far as the monofoiler vs the multihull-the comparison that was made in the 60' monofoiler thread showed the potential of the design to beat a 60' ORMA 60 sailing 30% on the ama and 70% on the ama foil.

 

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The I-14 would be hard pressed to be faster than a Moth but it might be possible off the wind-it wouldn't foil upwind. So far, cats have not been faster
on foils than they are off foils with the probable exception of the AC 72's and cats using Martin Fischers 4 foil system(Phantom F18, GC 32 and another one I can't think of). The AC 72 that most reliably foils(TNZ) has been clocked at nearly twice windspeed in a 20 knot wind.
With Veal Heel a monohull foiler can drastically increase RM with no movement of crew or ballast relative to the boat. That is a significant advantage. I'm real curious to see the results of the Phantom F-18 on Fischers foils vs a Moth. A two foil foiler using Veal Heel should have an advantage over 3 and 4 foil foilers that can't use Veal Heel.
Oh, just because it is larger, uses Veal Heel, has two foils, more SA, more RM and has the same or better ratios doesn't mean it will be faster than a Moth: the 26' Mirabaud is closer to equal in speed with a Moth than it is faster(though it has beaten a Moth but not by much so far as I know).
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Pitcures: Top, Phantom F18 on foils, Bottom-I-14 on foils--
click-
than it is faster.

 

In response to Doug's sketch, a "Veel Heeled" moth with a second hull, making it a catamaran.
For purpose of supposition consider canting rig is constrained at hounds in manner of Dick Newick's Ocean Surfer (mast step moves - photo),
and suppose windward hull has a raised T-foil that I've omitted from sketch as irrelevant.

 

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Here's a trimaran using two "power foils" that do add to the RM from Veal Heel. The windward "power foil" pulls down and is angled such that a component of the downforce is to windward similar to the component of lift on the main foil also to windward:

 

Until several weeks ago I was generally unaware of SpeedDream although I had read some of the posts about it here. Also I didn't know who Vlad Murnikov was. Then by chance I had dinner with him and he briefly described his rationale behind some of the SpeedDream design. Most of the dinner conversation was about other topics.

Vlad noted that when a catamaran is "flying" one hull essentially the only role the windward hull is serving is as ballast to provide the righting moment. He also claimed that most of the time while sailing offshore large multihulls only infrequently "fly" a hull because the risk of overturning is too great. This limits the potential average speed of a multihull during ocean crossings, etc. Hence the concept of replacing the windward hull with movable ballast which would shifted to windward above the water. A monohull with movable ballast would only capsize 90 degrees or so and could be righted by shifting the ballast.

Vlad's initial idea was to have the ballast on a transverse sliding platform which extended above the water. (This sounded to me like a scaled up IC sliding seat with ballast instead of or in addition to crew weight). Then he decided a canting keel which could rotate close to 90 degrees to either side would be more feasible. He is expecting the large version of SpeedDream to have a higher average speed than other boats for long ocean voyages.

I'm interested in how the concept works out. Clearly an essential element is a reliable, robust mechanism for moving the canting keel and holding it in position.

 

OK, I accept your sketch. Now imagine your sketch with a larger rig and the crew farther outboard. Result = more power. Now imagine lifting the windward foil until it's just skimming the water and its drag is next to nothing. It's not the foil that makes it a trimaran after all, its the float.

In theory you could equip a moth with a huge hiking board to get the sailor way out to windward, but as a practical matter you would never do it without putting a hull or float under him/her.

Oh, the windward foil pulls downward. OK, you could do that, too. My point is that one way or another you can always show a way a monohull can be made faster by being made a multihull.

 

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David, thats very interesting! I "met" him here and we've had one very long phone conversation-he's a fascinating guy. He sent me his book on the Whitbred on Fazisi- "Race to Freedom"-its quite a good read. Thanks for the post!

 

Agreed. Are you familiar with the Skandia/Wild Thing mishap? My answer to Doug's objection is that the drive, whatever it is, needs to be powerful enough, fast enough, and geared correctly to move the keel at whatever rate is deemed necessary. This can be done via a worm gear type linear actuator. What must never be allowed to happen is a situation where an out-of-control swinging keel endangers anyone trying to stop it and tears the boat apart. Needless to say sudden capsizes are also undesirable.

 

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The power foils were just an offhand idea that would only be used in maximum conditions. And the design would have to be done very carefully for them to be worthwhile. I did a fairly detailed analysis of the 60' monofoiler( I posted the link earlier) if you check it out also check out post 104 in the same thread. Its a comparison of the 60' monofoiler with a 60' tri using an ama foil(lifting 70% of the boat). Did a little less rigourous analysis for the 30' self-righting keelboat-link in the same earlier post.

 

almost 40knots of boat speed in 20k wind is not bad, but 28-31knots of boat speed in 7-8k is even better, the best there ever was, Dogzilla and Alinghi 5. (Anyone has any ideas on their approx disp? less the helium..)

Actually sailing at twice+ the speed of the wind for a big racing tri is normal, 100% lifting foils not needed.


mono-hull + 100% lifting foil = monofoiler, and so a moth becomes a monofoiler not a monohull. When names make sense then we all can agree on what we are talking about.

 

I didn't know there was a terminology problem. It seems to me a monohull with foils is a monohull with foils. In fact I think the moth rules specify that a moth must be a monohull.

 

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Come on, idkfa-monofoiler is "shorthand" for monohull foiler-I think you know that. Same with multifoiler.... And "bi-foiler" is a two foil foiler which can be a multifoiler or monofoiler.......