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Weight equalisation

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iGRF View Drop Down
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Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Topic: Weight equalisation
    Posted: 03 Jan 22 at 5:11pm
I've worked it out but you'll have to wait.

Mrs iGRF is not happy, I've tried to explain to her but she won't listen.


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Oatsandbeans View Drop Down
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Post Options Post Options   Quote Oatsandbeans Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jan 22 at 4:59pm
The mast has nothing to do with it. As I said it is two moments which are balanced and composed of two forces and it the magnitude of these force and their separation that is important.
The heeling moment is composed of the heeling force (sideways) from the rig and the lift (sideways) from the foils. This is balanced by the righting moment, which is composed of the crew weight and the buoyancy of the hull.
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Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jan 22 at 4:50pm
So why does the windward shroud go loose when I'm hanging on the wire?

I'm not suggesting a vertical force, is it not a sideways force?

And if the wind suddenly dropped without me getting back in the boat the weight of the wire will pull the boat over.
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Post Options Post Options   Quote tink Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jan 22 at 4:42pm
Originally posted by A2Z

Interesting isn’t it?  Lots of people have told you that you are wrong about moving the trapeze attachment outboard increasing righting moment but no one has really explained why.  

I have explained 3 times, and giving up now 
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Post Options Post Options   Quote Old bloke Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jan 22 at 4:38pm
I know its only because its Christmas and you're bored.
However, 2 simple proofs
1, picture the telltale on your main. They flow horizontally and the stronger the wind, the more horizontally they flow. So with an upright mast and horizontal flow there can't be a vertical force for the trapeze hand to counteract
2, go out to the garage, loosely screw 2 pieces of wood to form a L. Then keeping the angle the same use a piece of line as your trapeze wire, attach it to various places on the "mast" and the "trapezing sailor" and see if you can feel a difference.
It nay or may not convince you, but it will get you out from under the long suffering Mrs iGRF's feet
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Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jan 22 at 4:34pm
Had to revert back to schoolboy maths and moments, now this is not a statement, it's still a question.

So lets say racks, and our helm is 90 kgs and the racks are 2.5 metres out from the pivot point which we'll call the mast base. So Distance from pivot times mass to get moment is 2.5 x 90kg equals 225Nm yes?

So now with a trapeze do we not have to accept that the pivot distance changes from the foot of the mast to the end of the rack, to the foot of the mast to the point at which the weight is acting on the mast which is the new lever at say 4 mtrs to the hounds? So our 90 kilo mass now supported flat wiring from the mast must be 4 x 90 kgs and 360 Nm?

This doesn't asnwer my question but it does give some maths to start with.

Or, do we totally discount the mast lever suggestion because it's neutralised by the sail sideforce and the calculation remains directly from the pivot point to the point at which the harness is attached or the height of the sailor?

If it's the harness hook attachment point then my suggestion holds water, if it's the height of the sailor then it doesn't.

Those holding the racks trapeze makes no difference answer will hold with the view that wether racks or trap the c.o.g of the sailor distance prevails, i.e. 250 so 225 Nm righting moment either way.

I maintain that there is an element of mast leverage and probable weight reduction as a result, but it's an interesting thing to continue to work on and I hate maths, but there has to be a formula there somewhere to support what I'm sure I've read somewhere along the path.

Edited by iGRF - 03 Jan 22 at 4:41pm
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tink View Drop Down
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Post Options Post Options   Quote tink Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jan 22 at 4:34pm
Originally posted by iGRF

Originally posted by tink



I give up if you are not prepared to accept basic laws of physics I not going to try and change that


Humans wrote the basic laws of physics and they have frequently been proved wrong.

That's the trouble with engineers, they only do as they're told and never question anything.

Rules are and have always been, made to be broken.

?? The whole focus of Engineering is to question everything, that is what we do. I’m dyslexic and look at problems with very fresh eyes. PS  not sure my IQ but it is in the 99.99 percentile from full educational physiologist evaluation. I’m not questioning your intelligence either, hope I haven’t come across that I am. The physics we are talking is the same as a see-saw uses it’s not going to disproved 
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Post Options Post Options   Quote sargesail Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jan 22 at 4:29pm
Originally posted by iGRF

Originally posted by Do Different


Give it up people, there's nothing to be gained here.    iGRF has an undoubted history of being a demon windsurfer and marketeer but time and time again he has demonstrated that he entirely missed out on secondary school physics lessons. I have respect for skills and wish him well with his Contender experience.


I entered the Grammar School in the A stream, passed Physics at O level, questioned the physics master on his definition of light at the time 1964-5 and was proved right many years later. Have an IQ according to some of 166. (stupid logic puzzles) Question everything always, sometimes I'm right, sometimes I'm wrong, have probably been wrong more often than right, but that's not reason to stop questioning.

I do come here for a laugh, I don't take anything too seriously, but I hesitate to accept suggestions of not being as well educated or as bright as the rest of you. I just never ever accept the status quo and none of you have provided a convincing argument supporting the fact that a trapeze wire set further away from the boat does not provide better righting moment.

Do we have to re run the lee bow argument that proved my point?



Bubbles tell us about the bubbles please…

And then we’ll move on to laughing at your Lee bow vanity!
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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jan 22 at 4:27pm
Interesting isn’t it?  Lots of people have told you that you are wrong about moving the trapeze attachment outboard increasing righting moment but no one has really explained why.  
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iGRF View Drop Down
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Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jan 22 at 3:54pm
Originally posted by Do Different

iGRF. I did not say that you are not a bright bloke, which you obviously are and an innovator.
However. Sometimes you are simply plain wrong on the most basic theory.


This time I'm not wrong, I may not be correct in the harness hook positioning on my person, but the ([s]argument[/s]) discussion has gone beyond that, 'they' are now questioning the efficiency of a trapeze and how it functions and are wrong. Racks do not work the same as a Trapeze and unless you understand that, in my mind the argument against my higher hook theory also fails, though I suspect is probably right for altogether different reasons to do with the percentage of weight loss the further up the body you go, yet the bending knees fact still supports the attachment point being as far out as you can get. Why I'm still hanging on for a definitive answer.

Edited by iGRF - 03 Jan 22 at 3:56pm
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