Design for DSS-Foil Assist for Keelboats

There's a lot of discounting of comments going on, the moderator's included . . .

 

That's why I thought it was interesting. In the pic all the crew is sitting out, looks like there is plenty of wind, sails look twisted which would indicate they're dumping power or at least have more power available, still not using the DSS

 

Dss

In addition to the boats below these boats are almost ready: 1-two lake racing DSS boats, 2- two Quant 30's, 3- first JK 50 cruiser/racer, 4- Mini 6.5 DSS
This is just a little summary of the current boats that are sailing using DSS(no pictures of the experimental 27 or any conversions) :

Pictures,L to R: 1& 2-Brace, Brace, Brace DSS 25, 3-4-Quant 28, 5- Infinity 36 DSS just launched

 

Those who lack opportunity and money to get involved in a practical sense far outnumber those who can have “skin in the game” :?: and thus we have few if any marketing type promoters, a thin scattering of academics and a surfeit of mutually incompatible personalities This makes for long threads, informational underload, and lots of folk who - like me - occasionally get frustrated when their towering, self-evident genius and awesome mastery of the topic - any topic at all - goes unrecognized by the intellectually underprivileged

 

I'd already deleted the original post, upon reflection it seemed I was wasting my time.

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CutOnce

 

DSS-Speed Dream

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According to Vlad Murnikov, the reason for this is because he has chosen to experiment first with a stepped planing hull. That decision precludes DSS because the foil would probably not have enough submergence with such a hull.
click on image:

 

People choose the priority of their experiments in the order they assess provides the highest potential for success. This seems to support my theory, not refute it. Thanks for providing this confirmation.

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CutOnce

 

Don't really understand that statement. Hull depth is sort of a displacement thing, putting a step in the hull doesn't change displacement so shouldn't have much effect on hull depth.
I hope the step in that pic is hyper exaggerated.
I'm guessing that the SD guys have a lot on their plate adding one more variable like DSS is likely not wise
This looks pretty cool. saw it on SA and it's actually been built .
http://www.kuka-light.com/log-book/

 

Considering the original DSS 27 proto, the Brace^3, and the Quant 28 are all extremely light displacement, shallow hull forms it seems they are in the same ballpark as this new boat. So if it works on those boats why wouldn't it work on the SpeedDream?

The whole notion that the SpeedDream team is now eliminating the very thing (leeward lifting surface) that they originally touted as the reason their craft would be so revolutionary is quite surprising.

So now they have just a basic canting keeler, but have added a planing step. The step does not add any RM, but does add a lot of drag in non-planing conditions. That means it will have some big problems upwind and in light air. Also, without the magical extra RM of the leeward lifting surface they should be slower when pressed.

 

Dss

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A boat planing on a stepped hull has no room to immerse a DSS foil-the water level is at the bottom of the step-- and a DSS foil would likely not work unless the boat was heeled -probably over 10 degrees- which would then tend to reduce the effectiveness of the step.
When Yves Parlier did his cat with steps they found the step was a drag until a boat speed of 20 knots after which the drag dropped to less than 20% of that at 20 knots boatspeed.
Murnikov has looked closely at Eugene Clements work on steps(I know because I sent Clements booklet to him at his request). Clement's step is very, very small compared to a "normal" step -something like 3/4" on a 40' powerboat- and seems most suitable to sailboats. Clements system uses a cambered planing area(white in the picture below) just ahead of the step and a t-foil on the transom to keep the back end out of the water. But I think to have all round performance some form of variable geometry(like on Hydroptere.ch and proposed but never implemented by Parlier) would be required. The Speed Dream rendering may not be all that accurate for a variety of reasons.

Picture-shows cambered area on bottom just ahead of step. The step would not be immersed and so is not suitable for DSS which has to be 1 chord below the surface for highest efficiency.
click on image:

 

I wouldn't think there'd be many times when you were heeling less than 10 degrees.
Seems like about all the data on steps is from powerboats. Hydrodynamics on sailboats are different. Trying to get it right the first time has got to be tough. How do you figure out if it's hurting or helping? I guess you have to try something to make your deal unique

 

Therein lies the most serious challenge sailing has in actually making progress on most fronts. Measurement.

All these disparate development efforts, generally unique and unrepeated result in few to no indisputable conclusions regarding the efficacy of the developments. Most independent development efforts are a combination of many multiple ideas at once - and attributing results good or bad to any one idea is difficult.

In the past, development class racing provided a framework upon which individual efforts could be measured. Unrestricted development class racing today is under siege - perhaps due to global financial recession and declining interest from the general public. Did the America's Cup motivate me to use Oracle for my client's SQL database needs? No. Did I buy a BMW instead of a Toyota/Lexus? No. Was the sponsorship they provided effective in generating business or profile? Not sure, and the markets are not indicating they did.

We just do not know how much most of these technical developments actually provide benefits, if at all. Claimed benefits and anecdotal reports from interested parties just aren't acceptable evidence. There are so many variables in play and so little comparison to control groups.

On top of all these "hardware" questions remains the other problems: software and environment. Conditions and crew can and do dramatically affect the performance of any given "hardware". In the early days of Moth foiling, two people on identical equipment on the same day would perform so differently you could think the boats were wildly different. Technique differences were huge even though at the time everyone was sailing a Bladerider.

If money, resources and time were no barrier, Mr. Murnikov should build a series of basically identical boats - each incorporating one major technology difference (plus a unmodified base model) and then race them head to head across all conditions - that would quickly define what works versus what doesn't. But it is doubtful that will happen. Frank Bethwaite was able to do this methodical type of assessment, and his experimentation resulted in a major leap forward in design - planing boats that were able to exceed windspeed around a race course. Frank's chosen field was small, (relatively) inexpensive dinghy/skiff development.

Given the huge cost, time and effort required in keel boats to conduct a proper scientific study, I doubt we'll really get enough feedback to quantitatively evaluate DSS and ideas like stepped hulls. If there were military applications to fast sailboats, I have no doubt there would be taxpayer-funded research in progress right now.

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CutOnce

 

Dss

What I find interesting is that regardless of the years of extensive testing from RC models, to tank testing, to full size testing, to race results showing that DSS not only works but is fast that there are still those using gut feelings to question the efficacy of the technology. Leads me to believe that there must be something else going on. No confidence in the testing, no confidence in the race results, no confidence in the inventor/designer based on what? Amazing to me.....

 

What boats were these?

 

You mean race results that show the much lighter and newer DSS 25 being about the same speed as a Magic 25 from 20 years ago (without any lifting foils)?

Or the results that show the T30 without a DSS being faster than the T30 with the DSS?

Or maybe the results that show the DSS 25 being slightly faster than a much smaller Shaw 6.5 in optimum conditions, and slower in not-so-optimum conditions?

What about the result from the Centomiglia? Oh, the Quant 28 didn't show up for that. Maybe they haven't resolved the drive issues.

A couple of weeks ago the mini fleet in Europe raced around the Fastnet Rock. Where was the DSS Mini in those results?

It may be that the DSS is the greatest thing since sliced bread. So far the race results have not shown this to be true.

It will be interesting to see the new 36 footer in some big regattas against things like the McConaghy MC38, the Farr 400, and the like.