Monohull Speed: Speed Dream by Vlad Murnikov

Hi CT 249.
Sorry it took me so long, but finally I’ve got a few minutes to try to answer your technical queries.

1.SpeedDream hull is slim, yet it is wide and flat enough, especially near transom to have excellent planing characteristics.
Slim hulls are not necessarily less efficient at planing. True, at lower speed, a wider hull generates more lift, but as the speed grows, its drag grows even faster.
Long and slim hull needs more power to start planing, but at higher speed it generates less drag than a wider hull. That’s why relatively slow power cruisers are wide, while speedboats, like Cigarettes, are long and narrow.
SpeedDream’s planing characteristics are optimized for speeds of 35 knots and higher.
As a rule, multis’ hulls are too narrow and rounded for efficient planing. There exceptions, of course. Yves Parlier’s Hydraplaneur demonstrated a great potential, but then she capsized and I haven’t heard of her since...

2. At high speeds SpeedDream's wetted surface, even without using foils or a stepped hull, will be less than half that of a classic multihull flying a hull. To compensate for this, multihull must have higher RM and should carry more sails. In a sense this is a battle between monohull’s efficiency and lower drag, and multihull’s power. A problem for multi is that more power means higher loads on hull and rig, which in turn calls for stronger – and heavier – structure.
The real challenge for a monohull is not to be faster than a multi in absolute terms. That’s easy. Actually, even now their top speed is not that different. Banque Populaire’s top speed is 47 knots. Only half its size, a Volvo 70, a rather conservative design, has reached 44 knots. A radical super-light 100’ mono will sail much, much faster.
The real challenge for a mono is to maintain high average speed. That’s where a huge disparity is: 25knots for the best 24 hours by VOR70 versus almost 38 by Banque Populaire. By giving the SpeedDream a slender, wave-piercing hull we are encouraging her maintaining high speed for long time, just like multis do, without slowing down with every wave’s hit, typical for monos.

3. I believe I’ve somewhat covered this in the first paragraph.

At the end I’d like to say that my experience in designing multihulls is short and it would be great to see opinion of the multihull specialists as well.
Cheers,
Vlad

 

Well, Vlad, it really comes down to this.

You build it, you prove it and someone will find serious merit as to what you have to say about the proposals you present. With a smaller boat to be built, tested and sorted to satisfaction, it sounds like a long, expensive ride is in front of you.

The distinction between 47 and 44 knots is not a trivial matter, as you know. I'm not sure as to why you suggest it as such. I'd be willing to bet that all of the WSSRC speed trial boat designers would tell you the same if they are working in that realm of performance. These guys are scrapping for tenths of a knot in speed and you are suggesting that it's a simple matter of three knots difference. That's one of the problems with peak speed claims. They illuminate something that amounts to one half of a soccer game when everyone in the Round the World racing business is playing as if it’s several seasons worth of hard nosed scrapping out on the pitch.

This point is brought home conclusively within the actual, 24 hour average speed records, which are really the only kind of speed records that begin to matter to a Jules Verne Trophy style of boat. Even the 24 record held by Thomas Coville sailing solo is higher than the best of the VOR boats... and he wasn't using a lifting foil to get that record. Monohulls have a long, long way to travel before they even get into the game, much less stake a claim as the fastest.

I'm of the opinion that you are placing an inordinate amount of dependence on the lifting foil as the magical solution for getting a monohull to go as fast as a multihull. The same is true for the keel structure within such a defined, slender hull.

We've all seen the ongoing problems that all of the high performance, canting keel monohulls have experienced. Even after several years of pushing these setups to high levels of demand, the engineering solutions are still failing on a regular basis. Adding another structural element with such big loads is bound to have similar, extended teething problems. All of your claims for high speeds revolve around the ability of the foil to reduce wetted surface area. With such a narrow and concentrated structure to house all of the needed engineering solutions, I'm pretty much expecting the figuring-out process to take every bit as long, if not longer.

As far as I know, you are out there in your own world of design proposal with this boat. All of the canting keel boats had several, very high-powered design houses all working on solutions and look how long it has taken them to get things wired. I know that the canting technology absolutely drove the mast builders up a wall, trying to get things sorted.

I wish you luck, Vlad, but while this search goes on, big multihulls will continue to scorch the routes of established events and they will experience their own growth, albeit, likely much more incrementally than a radical jump in techno requirements, such as you propose.

Please keep us informed of your journey.

 

Maybe we're about due for a new breakthrough ... I'd like to see the monohull make a comeback competitively speaking.

 

Hi Vlad,
it seems to me that when flying with a canted keel above the surface of the water, further heeling would reduce the righting moment ( unless additional form stability is realized). Do you agree and if so, how do you see this problem being overcome?

I'm not looking to fault your concept. I just want to explore the topic a little.

 

Speed Dream

New on-line brochure: http://issuu.com/speeddream/docs/brochure

An email from Vlad:

SpeedDream progresses very well and keeps me extremely busy.
Design went from conceptual into development stage with more designers
and researchers involved and it takes a lot of efforts to coordinate them.
The SpeedDream Team is growing and needs constant management and
motivation. Plus constant communications with sponsors and prospective
supporters and never-ending search for funds. Plus dealing with the
media, with literally daily requests for information and interviews...
It's exhausting but also so exciting!
Currently we are finishing structural analysis with the SP-High Modulus,
gradually making our boat lighter and stronger.
Simultaneously we've started a series of CFD studies of different
configurations of hull shapes and appendages within a wide range of boat
speed and heel angles. Every new step helps us increase performance a
little bit, turning the SpeedDream into an awesome record machine. I
hope to post elements of this latest studies on-line within a month or so.

 

There is money for marketing, apparently...

1. I have a problem with the last page : "going green"
A canting keel requires energy, especially if you try to keep a constant heeling.

2. from the begining, it seems that Mr. Murnikov believes that multihulls are sailing in an usual mode, regarding waves production. THAT IS WRONG. A phenomenon, very similar to planning, occurs to multihulls above a certain speed. The drag due to wave production almost disappears, like for a planning monohull. Then, your only ennemy is the wetted surface, and a round shape will always have less surface for a given volume than a flat surface. To be competitive, the monohull should have redans (hope the translation is good here !), especially if it is realy optimized for speeds above 30knots.

3. I like the position of the foils, but I am quite concerned about the wave impacts on all these profiles. Alain Thebault and his HYDROPTERE are using shock absorbers, between the hull and the foils. (and Mr. Murnikov should read more newspapers. HYDROPTERE max speed is 61 knots, 51 on one mille.)

 

Further heeling (above horizontal) will reduce a little the righting moment, but 95% of it will still be here while the sails, more inclined, will produce much less momentum. Therefor, it is not at all a problem. 49ers have their "keel" (the crew :-D) well above horizontal.

 

While this is true, Eric, the 49er crew doesn't really have a choice in the matter... if they wish to stay a Class Legal 49er.

 

Hi, you've put a good question -- and the answer is even better.
Unlike multihulls that reach their max RM as soon as they start flying a hull, and after that loose it rapidly, The SpeedDream maintains her max RM all the way up to the 90 degree heel.
Just imagine the boat heeled to 20-25 degrees with the keel canted to 70-75 and out of water. if wind increases and the boat heels more, lifting keel away from water, all is needed is to release the cant a bit, constantly keeping keel horizontal and slightly above water. Ultimately, with the boat heeled to 90 degrees, keel would still remain horizontal, but now back to CL (simply by gravity, without any energy needed) and RM still at the max - well, almost. (For simplicity sake I'm putting aside hull form stability and stabilizing effect of the foil).
Anyway, that's infinitely safer than in the case of a multihull, and would allow our crew to push the boat harder without taking unduly risks.
Vlad

 

I can see how releasing the cant can be used to restore max righting moment and that only gravity is required for this process. What happens when the gust abates and the keel is only just above the water? Splash? OK - this isn't a show stopper but it would be very interesting to see this work in the ocean.

 

Could the rig not be designed to respond to gusts ( free standing or fractional with bendy top)?

 

A bendy top isn't going to help you recover from a knock-down with the kite up in the middle of the southern ocean - I think I'd want something more mechanical and brutish. Gravity and lead are pretty reliable.

 

Speed Dream-Target:worlds fastest monohull!

Here are the May and June Press Releases-the project is coming together:

 

Hydrofoils??

Hi to you all,

Sorry I know that this maybe leading away from your project discussion but I am curious as to wither or not the hydro foils would work on any modern yacht?? Also would it be costly to fit?? I am asking you guys as you seem to know what your talking about!

Kind regards,
Dave

 

Here is a thread on Hugh Wellbourn's DSS system-a "foil assist" a single retractable foil similar to Vlads application on Speed Dream though his foil configuration is not locked in yet to the best of my knowledge.
Foil assist uses a hydrofoil(s) to reduce wetted surface* resulting in increased speed and possibly some improvement in handling. The application has to be carefully considered-just adding a foil is not likely to be a good way to approach it.
My best answer to you is that the design world is fraught with opportunity to apply hydrofoils to modern keelboats in both a full flying configuration and foil assist but ,in most cases, an effective application will have to be made on a boat designed for it-probably not adapted to it. However, there is potential to adapt foils to some boats as long as is done by a foil savy NA. Opportunity exists across the board from dinghies to keelboats to multihulls and maxi's of all sorts. You'll be seeing a lot more of this as time goes by....
Hope that helps!

http://www.boatdesign.net/forums/sailboats/hugh-welbournss-dss-25-a-32138.html

*UPDATE(due to brain fade): And in the case of DSS(a form of "foil assist") the foil can dramatically increase righting moment as well.