Design for DSS-Foil Assist for Keelboats

That comment has now been removed from the original post as it does seem be an innuendo/insult which is not appropriate.

Let's please keep the discussion here productive and not stoop to insults or innuendo about others. Thanks to everyone for helping to keep the discussions above board and idea based and avoiding personal attacks and insults.

 

OK, back on track again!

While I agree the DSS principle is potentially useful I still have reservations about its practicality, and suitability for wide-scale adoption. The DSS contribution to RM is highly dependent on speed unlike hydrostatic stability, and cannot be changed quickly, unlike moving crew weight. It must be vulnerable to gusting, in a rapid heel it may well stall, it is virtually useless in light airs and downright ticklish in heavy conditions.

While there may well be more performance to be obtained by crew familiarity and boat tuning, it must remain a limited application. Deployment time will be too slow for short round-the-buoy racing, it is too risky to trust for long distances, and there's no way it will be adopted for the marina-queen class of boats.

I remain unconvinced but intrigued . . .

 

This is not DSS but the shallow inverted Y foils are similar in that the lifting foil area does the same job. These shots are in light airs and the lee foil has easily lifted the float out, speed is good and the drag, I figure, is less than a slightly pressed lee float with no foil.
So much to do, so little etc... but a future project is to fit DSS to the Cox's Bay Skimmer, or sistership. This will not be a large foil and probably set at close to the same shallow angle as the inverted Y lifting area on the trimaran. There is no keel on the skimmer, just a dagger; DSS will add stiffness, righting moment and allow more sail to be carried in stronger winds. Maybe? We'll see.

 

So Silver, it's normal practice to remove insults about other forum members, but personal insults by forum members towards named people are fine? If forum members were willing to accept personal insults then things would be different. In this case, it seems that some people were prepared to complain when they were insulted, but happy to insult others.

Surely people should either be prepared to take insults without complaint, or they should not throw them to others. You may be happy to see people who you respect and correspond with slagged off by others, but not all of us are like that.

In this case we have had information about DSS performance from two interested parties, but only one of them has been personally accused of being dishonest. If we are trying to discuss boat design then surely we must be even handed.

Oh, and you can speak for yourself, Silver, rather than telling me to get a life.... mine is damn fine in every way, thanks!

Over and out.

 

Silver's post tempted me to reply in kind, but that kind of tit-for-tat is just what we are trying to avoid isn't it?

Please read the moderator's post again, Silver, and understand what we are trying to create here. There's always Sailing Anarchy for those for whom a reasonable, polite discussion is just not enough . . .

 

Terry:

Your post concisely sums up my position as well.

Overshadowing all the debate and rhetoric here is the voice of the market. It has been conspicuously quiet on large scale adoption of many of these technologies - supporting your position quite well. Yes, the very few record chasers and rule beaters with cash to spare will try these things, but as Sean9c points out, racing class inclusion or exclusion of technologies is more a marketing consideration. It would be very different if a new class of DSS-enhanced one design boats emerged and had hundreds of buyers lined up to be able to race against each other - spurning the choices available today.

I've found that Vlad Murnikov's apparent movement away from DSS-like technology on his SpeedDream is quite notable. Since this is a definitive record chasing project, his choices are critical. Mass market choices in sailing are one thing, but when a technology-driven, cost no object record-breaker decides to focus elsewhere I take a little more notice.

Much like religion and politics, there are true believers who will champion their cause far past objectivity or available evidence. This unshakeable faith has always been a mystery to me - because I question everything, including my own opinions constantly (my faith is pretty shakeable). On forums like this there is little point debating with true believers (and their astroturfing sockpuppets & meatpuppets).

From my perspective, the jury on DSS is still out - and it may not ever come in. This isn't an indictment on the technology - it is more an indictment on the marketplace. Better technology is not an automatic winner in sailing - the "establishment" often suppresses promising ideas just because they want to keep things as they are. Revolutions are costly and unbalancing the status quo is uncomfortable.


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CutOnce

 

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From what I've been told deployment time is very quick-no problem on any course. And for small boats using plug in DSS foils eliminates the inside trunk and associated mechanism with the attendent disadvantage in very light air of extra drag. Depending on how the boat is used that may be acceptable.
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Terry, these comments are not reflected in the comments made by anyone who owns and sails a DSS boat(as far as I know)-are they your own speculation on the characteristics of DSS?

 

Dss 36

New DSS 36(Infinity 36 GT) just launched:

"The Infiniti 36 GT has been developed as a high performance yacht with the ability to either day sail short handed or race fully crewed; performance and ease of handling are paramount for the owner. The Infiniti 36 GT is intended to redefine the genre of ultimate carry-on day sailor for superyachts and will deliver unequalled performance, balance and versatility.
The Infiniti 36 GT VPP projects performance unequalled in this size and genre of yacht. Upwind the Infiniti 36 expects VMG gains of up to 10% greater than comparable yachts. When reaching the Infiniti 36 GT will provide exhilarating performance with speeds comfortably in excess of 15 knots. The lightweight, low drag hull form in combination with DSS ensures that speeds well into the 20 knot range will be possible when sailing downwind."


click on image-

 

Dss

From Hugh Welbourn on SA one year ago talking about DSS in general, drag, the Quant 28 and the 27' test boat:

Draaaag....and no, none us do drag without a good reason

Look at it this way - every item in the water causes drag, so to be there it has to have a good reason to be doing something important...so keel holds a lump of lead on the end and also provides sideforce which you need. Rudder produces sideforce. Both have viscous and induced drag but you need them.
Hull supports the thing in the water thanks to Archimedes, and has viscous, induced ( from leeway ) and wave drag.

So the DSS foil adds viscous and induced drag, but also can operate in various modes depending on immersion depth - so close to the surface it can be a nice effective planing surface, partially ventilated then likewise but a lot of the viscous drag has gone and if its got there then you aren't using all the RM/lift that it might be producing so it doesn't need to be working hard as a fully immersed foil.

Lift and RM....both are significant, and each design has its own requirement in how to best approach the foil and overall balance.

If you look at the video then you can visibly see how little the hull is contributing to wavemaking, wetted surface is low and also well aerated, and so we're bimbling along steady 15-16 knots and maxed 17 in about 10 TWS and only three up - me driving, German Journalist along for the ride and Kos up front.
Boat is in perfect balance, wouldn't be doing those numbers without the foil.
Bit later on the breeze came up from a thunderstorm and we were doing the same numbers and a bit more just on the working jib.

Lots more video from that day, and the weather side views make it look as if nothing is happening - practically no spray, stuff all hull in the water. But note, I'm not trying to fully fly the boat as then you get into all the trim problem - so its designed to have natural dynamic stability.

And btw - we've done extensive testing on the 27 in big waves and seas down off Sotogrande and never had any issues from launching off waves or burying or any signs of tripping.

 

Dss

More from Hugh one year ago: (highlights by DL)

Upwind - well the thing here is to match the wing parameters to the boat so that the net result - in steady state - is just slightly in your favour. So RM gain outweighs the drag cost.

However, what we then find is that as soon as there's any chop or seaway to move the boat around, then the damped motion in all axes makes a significant improvement that is seen on the VMG - even when you only seem to be sailing maybe a tenth quicker than you might. Now that comes from logged data and was a bit of ( pleasant! ) surprise to me until I figured out the dynamics of what was going on.

And don't forget, you don't need to use the wing at all until you are running out of natural RM, so no draaaag....until its starts to work and then the balance is in the your favour.
Its all a pretty finely balanced configuration but we've got a good handle on thing now from all the r&d and sailing and how to configure the different types of boat to work.

Downhill vmg - then same again - if you don't need the wing trickling along then its out of the water, but as soon as you can get into the situation where you can AWA sail then the more power you have to use the better. Bit like cats or skiffs, but cats can't get the spare hull out of the water until theres enough breeze, and skiffs or canters all have a fixed max RM.

So the AWA you sail on the 28 downhill is always well forward, but the angles you actually gybe through can be less than more conventional boats.Thing is, got two boats in one here - the light wind one is skinnyish with very low drag, but you can add in the grunt when you need it....

Start of the Bol d'Or - dead downhill, bit of breeze - ourselves and the 36' trapeze/canter Full pelt bolted off the line at 15+ and were a mile clear of the fleet in 10 minutes - and crossing gybes with some of the cats that started 300m in front of the mono fleet....they were a bit confused to see us in 'their' water.

 

- of course they are Doug! I want the technology to succeed because it's a really neat idea (I don't follow the crowd unless it's going my way) but those are the worries I have that may (IMHO) prevent it.

However, it does occur to me that foil lift could be adjusted automatically, perhaps adopting a version of the surface sensing methods used by foilers. That could open up long range racing as a valid application. But again, like foilers, large-scale market acceptance may be a long time coming. Cutonce wrote that the jury is still out; I'd have to agree on that. We have to accept that these fascinating ideas may turn out out like the flying cars of 50 years ago.

That doesn't mean that I won't try them out if I get a chance though . . .

 

I thought what was interesting about SteveM's comments and the pics of BBB form the regatta was that it appeared that they were not using the DSS upwind, which is curious as that is a total RM situation. Is the boat faster without it?
Also that downwind, in planing conditions that foil attitude effects boathandling which sounds completely logical. If you are relying on the DSS foil for RM and it stalls, or aerates or comes out of the water speed, or something, is likely effected.
Also curious how SteveM's comments were discounted as marketing hype. How's that? Sure he's pro Shaw but there is no marketed DSS competition, so there really isn't anything for him to be anti except maybe the concept. Give him some credit for actually being there and making the observation.
Also BBB is 1M longer than the Shaw 650, if the boats are of equal spec BBB should be dramatically faster than the Shaw. You're not comparing similar boats. If BBB is not faster than the 650 there's a problem.
Also this was one regatta, it's too little info to make any sort of judgement.

 

Dss

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Have you read the comments by Hugh Welbourn? The foil is not used upwind until it is needed.
From post 161 above: "And don't forget, you don't need to use the wing at all until you are running out of natural RM, so no draaaag....until its starts to work and then the balance is in the your favour".

 

Here's how it works. The comments from SteveM should be discounted as marketing hype because he is in the business of selling boats without DSS, while the comments coming out of the DSS spin factory should be taken as gospel even though they are in the business of selling boats with DSS.

Simple.