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BBA

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Posts posted by BBA

  1. 3 hours ago, rh3000 said:

    Ben - "Francesco! You don't want us to be here?!"

    Francesco - 'Yes! Yes! [inaudible]'

    CUT

    Ben - "[inaudible]"

    Any ideas? "something something some people feel about that" ?

     

     

     

     

    the inaudible bit he says'something like. "its the most insulting thing that could ever happen"

  2. On 2/1/2021 at 6:23 AM, erdb said:

    1) and 2) - I have no idea what you're talking about, but feel free to modify the drawing anyway you want to demonstrate your point. BTW, with those arrows I just wanted to show how the direction of a vector perpendicular to the foil wings' plane can be diverted up or down by differential flap settings. It wasn't meant to show accurate summation of foil wing lift vectors. 

    As for your 3rd point, certainly lateral rudder force would come into this as well, but I'm pretty sure it's negligible compared to lateral force provided by the foil. If there was any significant lateral force on those skinny rudders they would visibly bend (which happens sometimes in hard turns, but not while sailing in straight line).

    Hi erdb, 

    Firstly great posts here. 

    I modified your sketch to show what i think this is what notsofast is talking about. The sum of the forces will act through the point at which their lines intersect. So the resultant force will not necessarily act through the centre of the foil as in your original sketch. 

    image.thumb.png.ce4ac1896c396a09032a60089867a638.png

     

    image.thumb.png.af108adc00788ca6196ebe4ca9ae2ed3.png

     

    image.thumb.png.a9e1a290b8d3a61f8dde3a9f15719df1.png

    • Like 1
  3. 4 hours ago, Raked Aft\\ said:

    bending the mast and taking on Cunningham do not achieve all of the same results.

      where bending the rig will flatten in general, move the draft slightly aft and twist off the top.

      Cunny will also flatten and twist open, but move the draft forward.

    Right and they can mechcanical control the sail top so why not have seperate cunninghams to control draft independently in skins and have more control of overall wing shape?

     

    4 hours ago, MaxHugen said:

    Interesting.

    I gather that compression of the mast is to induce mast bend and thus reduce sail camber? If so, isn't it a rather inefficient way of achieving this compared to the running backstays?

    Running backstays dont go to the mast top

  4. 33 minutes ago, Dave S said:

    I suspect that with these sails, the cunningham works mainly by putting compression into the mast; that was certainly the case when I sailed much lower-tech skiffs. It's a very different mechanism to stretching the cloth in a dacron sail. If that is the case, a second cunningham wouldn't be that useful (unless one of them breaks, of course!)

    Right, yeah that makes sense. So essentally it controls the bend of the mast which effects sail shape rather than affecting the sail directly. 

  5. 2 minutes ago, enigmatically2 said:

    Don't think 2 is barred, but if you had 2 you would need to keep them consistent or you would mess up the foil shape of the 2 skins I think

    Yeah i can see that it could screw the shape a bit. Maybe differential system with a single ram and on adjustable offset. 

    Just thinking of the possisbilites to create a flattter inner skin and deeper outer skin. 

    Sure the design teams would have thought about it but wonder why they decided agaisnt it. 

  6. 6 hours ago, nav said:

     

    With the cunnighham problem on ineos i was surprised that everyone is talking about a single cunnigham. Assuming this means that there is one ram for both sails. I would have thought that there could be some advantage to controling each skin independently as with the outhauls. 

    Anyone know if this is restricted by the rule?

  7. 2 hours ago, NotSoFast said:

     Gitana 17 is lighter than idec with same overall dimensions. Foilsystems increase loadings. Combine those and you should realize why Gitana 17 either uses better materials, better structural design or less safety factors. It makes no difference if the part that actually failed had something to do with foiling or not. It could have been made stronger and heavier for the same overall weight of the boat, if it would have had less and/or smaller foils.

    Is it not just a matter of time. My take on it is that a boat needs to be fully bedded in before being able to complete a jules verne lap (macif and Gabart being the exception that proves the rule). This is a race for seasoned old in the tooth ocean yachts. 

  8.  

    Jimmy and Francesco (?) comments here are telling. Two people with eyes on the course and who know something about getting these things around a course. Both would have taken the right gate. Maybe seeing americans on its side has had an influence but still they seem genuine in what they say.

  9. Looks to me as though they will be going full throttle for coming days. Currently 35knots and dont look like slowing for the ext 4 days. Cant imagine what it must be like for them on board. 

    The whole teams preparation, experience and ability has created a lot of luck for them this far! Lets hope it continues.

  10. 46 minutes ago, Sailbydate said:

    Yes. Completely airborne and definitely smashed back into the water on her side, the port foil taking the full force, by the look.

    Screen Shot 2021-01-17 at 8.54.23 PM.png

    Can anyone extrapolate how quickly they are falling from the bird the flies past the stern?

    • Like 2
  11. 14 hours ago, weta27 said:

    Looks more like a change of mind, sit-down and think again

    Yeah maybe you are right. I reckon would be a good move to be able to do though, especailly if we are going to be having close racing. They do the rounding and tack at the bottom mark which is similar, guess they have a bit more boat speed to be able to pull it off.  Has anyone been practising maneuvres that could be described as a dummy/double tack?

     

  12. 3 hours ago, terrafirma said:

    It isn't being powered by a diesel generator that would be something else you are hearing. Obviously a diesel something is running behind the camera. Irrespective of that they are not racing and only testing so they can do what they want.

    Surely this was a joke, just a bit of a laugh. Why so serious?

  13. 5 minutes ago, Horn Rock said:

    All these boats will be at or close to the specced minimum weight. Weakening the structure to may be put some ballast lower down might only yield a minimal gain in a foiling boat. I guess this is what they're trading?

    Could be though I center of mass is also stipulated in the rule.

    image.thumb.png.c35de78d60616a651a2d0b01ebae59ad.png

    So they have 50 cm to play with in fore and aft position. Could be important for balance/trim.

    17 minutes ago, Horn Rock said:

    All these boats will be at or close to the specced minimum weight

    I had a look for a minimum weight but seems what with the foiling we now have maximum weights.

    image.thumb.png.00aec7aa818f7ad43f6d7f024d5ec984.png

    I couldnt see a minimum weight anywhere. so i guess they are building to maximum weight for max righting moment. 

    I guess having less weight at the extremties of the boat also effects the inertial properties. Wether or not that has any serious effect idk. 

     

  14. 5 minutes ago, Horn Rock said:

    Evidence is building that this boats structure has been under specced. Deck areas around the mast had warped. They had a no step sign on the foredeck. Repaired cracks were also visible. Chainplate of the forestay failed dropping the rig, and now the nose has ripped off. They've been finding the limits and exceeding them a tad too often imo. With a boat like this the crew would start to lose confidence in cranking on the loads. This boat might get scrapped.

    Its easier to add laminte and strengthen a boat than it is to take layers away. Also I think the natur of these boats is that they will all be scrapped post AC. You dont see many AC72's sailing around these days do you.

    I agree they have probably pushed it a bit to far in too many areas causing them excessive downtime. But, if they can learn from these failures and boat two has all these items beefed up to overcome the the failures they have seen then maybe it could just be that edge needed to win. Maybe.

     

    • Like 3
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