Design for DSS-Foil Assist for Keelboats

Discussion in 'Sailboats' started by Doug Lord, Dec 6, 2011.

  1. Doug Lord
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    Doug Lord Flight Ready

    Dss

    ===================
    No reason you couldn't do that on a boat like this except water ballast would be problematic on such a small boat wouldn't it? I "assumed" that they wanted the self-righting characteristics of a keel so I kept that and showed what DSS could do-it is true that it can 100% replace a canting keel in some applications.
    ---------
     
  2. ancient kayaker
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    ancient kayaker aka Terry Haines

    Post #103 confused me -

    If a ballasted canting keel can no longer cant to do its job then the boat has to heel or the weight is merely cargo. However, the DSS is designed to provide RM at a low angle of heel. So what’s the point of the weight on the retractable fin or daggerboard?

    It seems to me that the canting keel and DSS foil make a complementary pair. If the canting ability is removed and a DSS is added it makes sense to remove the weight and make the board easier to retract (and retrieve!) in an emergency.
     
  3. Doug Lord
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    Doug Lord Flight Ready

    Design for DSS

    =================
    AK, the fixed keel on the proposed mod to the SK2 is there primarily to assure the level of self-righting that would have been possible with the canting keel.
    Without the fixed keel, especially on larger boats, capsize would be likely. The performance boats designed specifically for DSS-Quant 28 and Brace- have fixed keels. My idea was to see that if DSS was used could it replace the RM lost with the canting keel-the answer: it could-upwind and downwind. Note that the DSS foil is designed to work at an angle of heel-from 8-12 degrees depending on the boat(10 degrees for the proposed SK2 mod).
    There is no reason that you couldn't use the canting keel and DSS-but why? The fixed keel + DSS provides more RM than the canting keel alone upwind and downwind and is simpler.
    If the weight in the keel was removed the SK2 would barely have enough RM upwind with just DSS and the crew and would not be self-righting.

    PS- At the 10 degree angle of heel of the SK2 with DSS, the fixed keel provides just enough RM along with DSS to exceed the RM provided by the canting keel alone at the same angle of heel.....
     
  4. Doug Lord
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    Doug Lord Flight Ready

    DSS Design

    AK and Gary, I've become convinced that "plug-in" DSS foils may be the ideal solution on a small(12-15') dinghy as opposed to a board in a trunk. I'd use two small trunks and tapered asymetrical straight boards. One board is always out of the water and they're easy to remove and plug the trunks. Much less expensive as well. But you guys already know this-I think it was your idea!
     
  5. Doug Lord
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    Doug Lord Flight Ready

    DSS(Dynamic Stability Systems)

    Interesting information about the DSS equiped Magic Carpet:

    Data:

    120 degree True Wind Angle (TWA) – performance summary:

    Percentage performance increase at 120’ TWA delivered by DSS is from 1.2% at 6knots of wind speed to 44.2% at 25 knots of wind speed

    This equates to being 0.14knots faster at 6 knots wind speed and 7 knots faster at 25knots wind speed

    The DSS powered Magic Carpet is always faster than the standard Magic Carpet

    90 degree True Wind Angle (TWA) – performance summary:

    Percentage performance increase at 90’ TWA delivered by DSS is from 3% at 6knots of wind speed to 39% at 25 knots of wind speed

    This equates to being 0.3knots faster at 6 knots wind speed and 5.7 knots faster at 25knots wind speed

    The DSS powered Magic Carpet is always faster than the standard Magic Carpet

    70 degree True Wind Angle (TWA) – performance summary:

    Percentage performance increase at 70’ TWA delivered by DSS is from 4% at 6knots of wind speed to 29% at 25 knots of wind speed

    This equates to being 0.5knots faster at 6 knots wind speed and 4 knots faster at 25knots wind speed

    The DSS powered Magic Carpet is always faster than the standard Magic Carpet

    40 degree True Wind Angle (TWA) – performance summary

    Percentage performance increase at 40’ TWA delivered by DSS is from 2% at 6 knots of wind to 8% at 25 knots of wind, almost a knot faster

    The DSS powered Magic Carpet is always faster than the standard Magic Carpet

    Additional benefits are derived by the reduction in pitching and the increased efficiency of the sails when sailing close to the wind

    Upwind and Downwind VMG differencesWhilst DSS provides unparalleled performance gains in reaching conditions it still provides significant gains in a windward/leeward environment as shown by the gains in the upwind/downwind analysis

    Further gains can be made with a bespoke yacht design where DSS is central to the initial design process


    Images-click on image for better detail, Last image of Magic Carpet sailing by Nico Martinez:
     

    Attached Files:

  6. Cheesy
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    Cheesy Senior Member


    Some more results of a DSS boat against other sportboats
    http://forums.sailinganarchy.com/in...3&hl= crime scene&fromsearch=1&#entry3708873

    Ill be a nay sayer at least in the sub 30' boats
     
  7. Paul B

    Paul B Previous Member

    Seems you have not included any photos of the DSS installation on Magic Carpet.

    Maybe there is a good reason for that. You might figure it out someday.
     
  8. ancient kayaker
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    ancient kayaker aka Terry Haines

    The DSS requires speed through the water to operate, the faster the better, so it's performance will be favored by application on fast boats. Large boats do tend to be faster but there are lots of small, fast boats out there. DSS is only practical on a boat specifically designed for it, not as an afterthought. Below 10 k boat speed it is not worth anything, which might be disappointing for a lot of boat owners whose boats never get to that speed let alone above. Of course, there are many boating concepts that are useless on the majority of boats . . .
     
  9. Doug Lord
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    Doug Lord Flight Ready

    Brace ,Brace Brace

    Brace, Brace, Brace was quite fast but it sounds like maybe crew decisions(too much sail for the conditions) played a role in the final results:
    http://www.topofthegulfregatta.com/results/TOG2012_Class 5 Sport Boats.htm

    The Welbourne looked very quick in the 10-12 knot range, but above that, the crew said it was tricky to control the leeward horizontal fin to keep the pitch right, it would be overtaking waves and then would go down the next wave with a huge spray and be a bit stop start and carrying way too much sail area probably didn't help them much on the first day; in the bigger breeze of around 20-25 knots on day 1 the Shaws seemed (from where we were sitting) the quickest downwind on the water, sailing lower and faster; as it slackened off in day 2 (15-18) and day 3 (10-12) the Welbourne started to shine, and the sea state was a bit smoother as well which helped a bit.
    ------
    More on Day One:

    Both the bigger boats capsized gybing around the outside of the rock. The big IRC boats and most of the rest of the fleet other than multihulls only went to mark B so we were the last class to start and it was after almost 2 hours of upwind so no other boats were around, there were no safety boats and seas were around 1-3m, confused and extremely steep with 20 - 25 knots in gusty conditions; Crime Scene had passed the 2 bigger boats on the water as they all went to gybe together and at that point we would have been maybe 5 minutes behind and gaining rapidly, the Shaws are pretty quick downwind and we were running the big running kites (whereas I think the two bigger boats had switched to smaller flatter reachers at this point).

    The guys on board can say more, but I would say probably the extremely gusty nature of the winds out there, confused sea state (2 knot tide in 30m deep water around that rock), sailing hotter angles using a reacher, a bit of complacency on board as it was the final gybe before the finish another 8NM away and the fact that boat those big boats are 3.5m wide with wings meant once they started going over, the wind catches them and pushes them over, then the sails get caught in the current.

    The Welbourne popped up easily, and I expect if there was a support boat, the P8 would have been popped straight back up by the crew; as it was the bigger boats are sailed open hatch, so if you go over, then they are full of water when they come back up, so they kept it on its side and bouyant until help arrived, and the Welbourne stood by to make sure they were ok (as did we briefly, but they were obviously ok, just needing a support boat)




    Analysis about "keeping the pitch right" is interesting but highly suspect. Other reports indicate the wide wings stopped the boat in the heavy conditions on the first day.(Report 1 on the Asian site, I think) No doubt a very fast boat but tough for the crew for some reason....(high powered??) "Getting the pitch right": lets see the foil is fixed at a positive angle of incidence. The foil is also the type of foil that lifts even at a degree or two of negative angle of attack. So if the "pitch" were wrong it wouldn't be controllable by the crew:
    1) if the angle of attack were too high the foil would breach the surface;
    2) if the angle of attacke was too low the boat would roll to leeward with the hiking wings hitting the water and, perhaps stopping the boat. But the foil, in and of itself would not stop the boat.
    It seems to me that with the boat overpowered(as mentioned above), tough conditions, confused seas what may have happened has a lot less to do with DSS than it does with decisions made by the crew. Describing this in context of a performance problem with DSS in over 10-12 knots wind is a big stretch and likely a faulty analysis of the facts.
    -----
    Congratulations to Hugh for the overall race victory of Neil Prydes Welbourn 52!
     
  10. Doug Lord
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    Doug Lord Flight Ready

    Dss

    ===============
    Actually the foil can be beneficial-just- between 7 and 10 knots....
     
  11. Doug Lord
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    Doug Lord Flight Ready

    Brace, Brace, Brace

    =================
    The boat finished 3rd overall despite a DNF* in the first race and obvious boathandling problems. Nay say all you want but the thing is damn fast....

    *BBB asked for redress for the DNF since they stood by another boat in distress.....
     
  12. sean9c
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    sean9c Senior Member

    You do have to wonder about a horizontal foil that's not pitch adjustable. Boats pitch, the foil's angle of attack is going to be constantly changing. Angle of attack is critical, a couple degrees of change is a big deal.
    Couldn't you compare it to foiling Moths, they're an extreme example but, they control the foil angle of attack with the wand so it's constantly adjusting.
     
  13. ancient kayaker
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    ancient kayaker aka Terry Haines


    Not so: two entirely different things.

    The boats' direction of motion is parallel to the surface and the boat's waterline is (more or less) parallel to that also. The boat pitches because the surface is wavey and it has to in order to maintain displacement, which happens hydrostatically. In order to do its job the pitch of the foil has to be constant relative to that motion not to the horizon.

    Therefore there is a single optimum angle and the foil can be fixed - not constantly adjusted to suit the moment-to-moment motion of the boat.

    On the other hand, the foil angle on a Moth is required to be dynamic because the height of the boat above the surface is established and controlled hydrodynamically by foil angle, since it uses submerged foils, not surface piercing foils which can maintain height automatically by varying submerged area.

    In both cases wave height sets a practical limit on foil performance.
     
  14. Doug Lord
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    Doug Lord Flight Ready

    Dss

    Excellent comment ,Terry! The SA poster attributed the "pitch" comments to the crew-be that as it may I seriously doubt the narrative because it was simultaneously reported that the boat was over canvassed for the conditions and, maybe, rather than blame themselves for that decision they( who in the crew is that comment attributed to???) invented a role for the foil in their demise in the first race. Nevertheless, even with a DNF the boat finished third overall which is not too shabby.
    Nay sayers will glum onto every little faltering step in the development of new technology ascribing every negative situation to the new technology. They will call what is a good finish for any boat a failure, describe the technology for all boats under 30' as ineffective because they choose not to look at all the facts(Quant 28) and project a negative agenda when it comes to the technology. This same boat has had remarkable victories but those get lost in the obfuscation created by the demands of their agenda-too bad. But one way you can tell it's an agenda is to look at the different DSS threads and note who exactly makes the disparaging-facts be damned- comments time after time after time.......
     

  15. Doug Lord
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    Doug Lord Flight Ready

    Dss

    =============================

    The foil designed by Hugh Welbourn can take a 2 degree change in angle of attack without ever losing vertical lift-just a fact. The narrative about the "pitch change" is highly suspect given the other known conditions that day including the fact that the boat had too much sail for the conditions-a direct result of poor crew judgement.
    --
    Another example of the fallacy of the foil behaving in the way the "crew" said it did is the use of fixed fore and aft surface piercing foils like on Hydroptere and numerous other boats. There is no altitude control system (other than speed) and pitch control is designed into the boat thru proper foil placement as it is in a DSS boat where the hull provides built-in pitch control--for the most part regardless of conditions. Again, it is much more likely that the overcanvassed configuration of the boat caused the "crew"(or someone) to misinterpret what was happening.
     
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