Design for Speed and Efficiency-Lessons from Hydroptere

Discussion in 'Multihulls' started by Doug Lord, Sep 8, 2009.

  1. Doug Lord
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    Doug Lord Flight Ready

    We've all grown up knowing that the fastest multihull designs 24' long were the C Class cats with their wing rigs and fanatical emphasis on lightness. So why then does the fastest sailboat on the planet use soft sails and only one sail with a semi-rectangular planform? Imagine a triangular jib on the fastest sailboat in the world!? (And the fastest sailboat under 20'-the foiler Moth-also uses a soft sail)
    You can see pictures of Hydroptere with a damn sail drive hanging off the bottom! That's not fanatical "weight consciousness",is it? And 11 guys and water ballast? The aussie foiler Spitfire also sailed with twin soft sail rigs -and 1000lbs of ballast! What gives?!
    It must be something to do with getting the basics right and not getting too hung up on "high tech". I think there are some pretty astonishing lessons starring us in the face-what do you think?
     

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  2. nero
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    nero Senior Member

    It points out how limited people are in their ability to comprehend technology and integrate it into a project.

    Hydroptere also is a project of how a lot of desire and funding can compensate for incompetence. As well as a bunch of resources pissed off on something with no application.

    It was in Marseille doing trials for a while last year. Interesting to see, but not a very high-tech machine. They even have a marketing crew that stayed in the same quarter as my home. Nice fokes tho.
     
  3. bad dog
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    bad dog bad dog

    Good critical approach to ask these questions.
    First thought is obviously to credit the foils - their load carrying
    ability is well known from ferries etc.
    The applications in commercial passenger craft in the post oiler are obvious.

    The soft sails is a tougher question - especially when you look at such 'competitive' craft as Macquarie Innovation with its wing sail...
     
  4. bad dog
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    bad dog bad dog

    Typo - post oiler should read post oil era.
     
  5. Chris Ostlind

    Chris Ostlind Previous Member


    It's a simple matter of building to the design brief and the intended application. Hydrop, if it truly does go out on the big blue water in search of records, is designed for different reasons than a boat that operates in a much tighter set of controlled conditions. You can't reef a hard sail and quickly reduce exposure when you are a thousand miles from land.



    Mostly because they are not toys, Doug. They involve real live human beings who will be traveling as a mass at a pretty good clip. There has to be some mechanism for reducing the potential of tossing it, or nice folks will get hurt.



    There aren't any more "astonishing lessons" here than there are with any properly functioning boat that lives on the edge. Last October, when Hydrop tripped the light fantastic and remained upside down in the Med... what was the basic lesson to be learned by the readers from that exercise? That something can break, that the driver was inattentive, that the boat has a fundamental flaw and is unstable at speed, that they may have been over-powered by a huge gust... what?

    These guys can run all the complex calcs that they want on the fastest computer known to man. In the end, the boat is crewed by live men and the actual trim of the vessel will be attained by the "feel of the boat" that has been learned by those men after many hours on the water. I'm of the impression that this recent record was achieved, specifically, because the guys on board had the collective sack to push it past anything that they knew before. Simple as that.
     
  6. Gary Baigent
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    Gary Baigent Senior Member

    Chris, I've said this before but Hydroptere, I read somewhere, cartwheeled when they were SLOWING down (in what looked very savage conditions) - and it would be very interesting to know what made this occur .... so far, no clarification.
     
  7. Chris Ostlind

    Chris Ostlind Previous Member

    Yeah, me too, Gary. You have to know that a team this well funded had a crew of shooters on site to correlate the tape footage with the data on board. Not putting it out there right now, when there's nobody running anything even close to their configuration, is interesting.

    Slowing down and tripping would sound like a rotational inertia issue. Tell me if this sounds anything like correct...

    The boat slows... traveler, sheet, whatever, and the boat drops down on the wider portion of its forward foils. This induces higher drag, pitching a bit forward, lifts the rudder and at the same time the rudder emerges from the face of a swell, losing all grip. Inertia and yaw, induced by wind direction, does the rest and cablooey, over she goes with the crew totally helpless to do a thing about it.

    Whatever; That must have been one scary-*** ride for the guys out on the ama. They fly through the rig and then the boat, with it's ballast intact, drops over on top of them. Luck and serious swimming skills are probably heavy screening items when reviewing resumes.

    Dudes are very lucky and it warms me that there were no injuries that sent people to the barn.
     
  8. Gary Baigent
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    Gary Baigent Senior Member

    Yes, that's probably very close to the scenario Chris - however I wonder if the whole platform got into a rocking mode, like: boat slows from nose bleeding speed to say 20 knots, and as you say, leeward foil sinks to broader chord area which, with a combination of lumpy waves, suddenly jerks the lee float up, at the wrong fargo trucking moment when the beam sea to windward becomes a trough, **** then occurs ... or something like that. Hey Alain, or one of your doughty crew, we'd like to know .... not that that information is going to help anyone much in a similar situation ... where you'd just be a passenger (but now enlightened and educated) with tight sphincters.
     
  9. DocScience
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    DocScience Wishful builder

    rudder needed for negative lift

    With that design, The rudder has negative lift most of the time to keep it from pitchpole, so as you describe, as the rudder gets nearer the surface for any reason, it looses the negative lift that is desperately needed.

    I mentioned about the proposed Hydroptere Maxi putting the main foils farther forward because of this. This would reduce the negative lift, needed on the rudder for stability.
    My opinion is that this is a week link in the whole design, and that the new design does not eliminate the problem, but is an attempt to minimize the problem.

    I think that they have put lot of good thought into the designs which shows in achieving sailing records.
     
  10. Gary Baigent
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    Gary Baigent Senior Member

    No DocScience, the rudder doesn't supply negative lift all the time, just the opposite; it is positive - to lift the stern of the platform up, otherwise Hydroptere wouldn't be able to fly. Instead, in that configuration, the two main beam foils, would lift and the platform would drag along with its bow in the air, going very slowly. But in a crash situation from flying, bow down and main beam half underwater, the movement of solid water flowing above the inverted T rudder would slow the lifting of the stern completely out and yes, angled down like that, the stern rudder foil is providing negative lift - and a great help it is too. But once stopped, no more water flow, then it would pop clear ... and you complete the pitchpole.
     

  11. Doug Lord
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    Doug Lord Flight Ready

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    On Hydroptere and equally boats like the 26' Mirabaud monofoiler -and most other foilers- the rear foil will lift initially and, as speed builds, it will become nearly neutral or pull down. The amount of lift initially varies depending on setup-some foilers like Raves take off with an almost level attitude with something like 20% of the weight supported by the rear foil up to a crossover point where the rear foil pulls down or runs in neutral. Mirabaud takes off with 50% of the load on each foil gradually transferring all the load to the main foil with the rear foil essentially running in neutral maximizing its response to pitch excursions.
     
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