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iGRF View Drop Down
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    Posted: 03 Jan 22 at 2:27pm
Originally posted by tink

Originally posted by iGRF

So what’s now being suggested the Contender doesn’t need a wire and trapeze at all because you’re an Engineer and I’m in marketing?


You could fit wings on a contender and the crew could create the same righting moment as a trapezing crew, the key thing is where the crew c of g is. As a engineer this stuff is my bread and butter so my understanding of this stuff is rather relevant.


Well I would beg to differ, then what do I know, I've only spent thirty odd years marketing harnesses and harness hooks in wind and more recently kitesurfing where the idiosyncrasies are very different. So you'll excuse me for choosing to find out for myself, when I can find a suitable harness with the option to vary hook height.

As for fitting racks on a contender, or using your Toy example, they may very well apply sufficient righting force but they will be slower. If you are truly an expert engineer, then I shouldn't have to explain why, but if you wish, I'll try and find a better drawing programme to illustrate why.

Edited by iGRF - 03 Jan 22 at 2:29pm
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tink View Drop Down
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Posts: 789 		Post Options Post Options   Quote tink Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jan 22 at 1:56pm
Originally posted by iGRF

So what’s now being suggested the Contender doesn’t need a wire and trapeze at all because you’re an Engineer and I’m in marketing?


You could fit wings on a contender and the crew could create the same righting moment as a trapezing crew, the key thing is where the crew c of g is. As a engineer this stuff is my bread and butter so my understanding of this stuff is rather relevant.
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Tall people have more righting moment not because the trap hook is further from the boat but because their CoG is further from the boat. Moving the hook doesn't change that.

How high up the mast the wire attaches (almost always at the hounds IME) is also irrelevant WRT righting moment but the lower it is the more load on your legs to stay standing horizontally off the side of the boat

You have to have the trap hook at or slightly (but only slightly)* above your CoG to be able to move around the boat, if it's too far above and you feet slip off the gunnel your legs will fall in the water, if to low your head/body will fall into the water.

* In practice slightly above your CoG has proven to be most efficient.


Edited by Sam.Spoons - 03 Jan 22 at 1:31pm
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Posts: 3401 		Post Options Post Options   Quote Sam.Spoons Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jan 22 at 1:21pm
Originally posted by Do Different

I have a friend who is an engineer. He once told me that he spent half a night in a pub with a bloke who was convinced putting a wind turbine on his car to generate electricity as he drove along could feed an auxiliary motor to save petrol.   
Nuff said.

I'm guessing this is something to do with the 'apparent wind' effect we know and love.
 



Edited by Sam.Spoons - 03 Jan 22 at 1:31pm
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iGRF View Drop Down
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Posts: 6499 		Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jan 22 at 12:58pm
Originally posted by mongrel


Originally posted by iGRF

Originally posted by 423zero

Think about the angle the wire is from your body to the mast, it's not much off vertical, if you stood at the side of your boat and tried to tip boat on its side using the exact same angle, you wouldn't tip it over.
Youve just made the case for me. Exactly why moving the wire further away helps pull the boat over.

& why in a lull you bend your knees to reduce your righting moment.


And why you'd have to bend your knees further and earlier with a higher hook?

Edited by iGRF - 03 Jan 22 at 12:58pm
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Posts: 304 		Post Options Post Options   Quote mongrel Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jan 22 at 12:15pm
Originally posted by iGRF

Originally posted by 423zero

Think about the angle the wire is from your body to the mast, it's not much off vertical, if you stood at the side of your boat and tried to tip boat on its side using the exact same angle, you wouldn't tip it over.
Youve just made the case for me. Exactly why moving the wire further away helps pull the boat over.

& why in a lull you bend your knees to reduce your righting moment.
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Posts: 3420 		Post Options Post Options   Quote 423zero Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jan 22 at 10:28am
Griff, if you didn't have a trapeze you couldn't have your feet on side of boat and lie out horizontally, you would have to put your feet under hiking straps, but because you are nearer centre line of boat you have less righting.
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Posts: 742 		Post Options Post Options   Quote rb_stretch Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jan 22 at 10:22am
Originally posted by Paramedic

So:

If the height of the wire on the mast makes no difference why bother with a trapeze at all?

If the angle of the wire to the body (Position of the wire on the body effectively) doesn't make a difference why not just trapeze off the centreboard case all of the time and reduce your windage?

A higher hook on the body must make a difference but isn't practical and probably doesn't make enough difference to make the impracticalities worth dealing with.


If the mast and the body were perfectly stiff, then you would have the wire at the tip of the mast and the top of the head, as that creates the least tensile force in the wire. The closer the wire moves to the foot of the mast and to your feet, the higher the tension in the wire. Actual positions are really determined by the highest, relatively stiff point in the mast (usually where supported by shrouds) and where our bodies are most comfortable with the force.
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Posts: 6499 		Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jan 22 at 10:22am
So what’s now being suggested the Contender doesn’t need a wire and trapeze at all because you’re an Engineer and I’m in marketing?

Edited by iGRF - 03 Jan 22 at 10:24am
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Posts: 1312 		Post Options Post Options   Quote Do Different Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jan 22 at 10:17am
I have a friend who is an engineer. He once told me that he spent half a night in a pub with a bloke who was convinced putting a wind turbine on his car to generate electricity as he drove along could feed an auxiliary motor to save petrol.   
Nuff said.
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