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Mikey 14778 View Drop Down
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Posts: 298 		Post Options Post Options   Quote Mikey 14778 Quote  Post ReplyReply Direct Link To This Post Topic: 'Weight on the Wire'
    Posted: 25 Mar 09 at 3:14pm
It was cool 20 years ago you young whippersnapper - we were proper men in those days.

I remember when all this was just fields
Fireball 14778 - 'Cruel and Unusual'
Draycote Water, fantastic !
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G.R.F. View Drop Down
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Posts: 4028 		Post Options Post Options   Quote G.R.F. Quote  Post ReplyReply Direct Link To This Post Posted: 25 Mar 09 at 3:40pm
Originally posted by turnturtle

even old grumpf's can't do cool on a long
board these days, far better he sticks to the ASBO..


That's a matter of opinion.

https://www.ease-distribution.com/
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Medway Maniac View Drop Down
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Posts: 2788 		Post Options Post Options   Quote Medway Maniac Quote  Post ReplyReply Direct Link To This Post Posted: 25 Mar 09 at 4:14pm

There's a definite theme emerged here (or had before it became the usual banter thread )

Evidently it's all about handling, ease of maintaining balance and trim, and not power. I'm happy with that - thanks very much everyone.
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Guest View Drop Down
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Posts: 0 		Post Options Post Options   Quote Guest Quote  Post ReplyReply Direct Link To This Post Posted: 25 Mar 09 at 4:27pm

Having sailed a number of trapeze boats there is definatly a cross over point.

I remember in the 470's that the top French guys would hike resonably hard before they got on the wire ... they were quick.

I think atctually it has more to do with how you are able to squeeze the boat forwards in a response to a gust keeping the boat flat and not inducing a windward roll at the end of the gust and hence using loads of rudder.

I will usually hike if there is not enough wind to be comfortable on the wire all the time and if I have to pinch a bit in a gust to avoid getting on the  wire I'm OK with that.

 
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JimC View Drop Down
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Posts: 6662 		Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 25 Mar 09 at 4:57pm
Originally posted by Guest#260

I remember in the 470's that the top French guys would hike resonably hard before they got on the wire ... they were quick.


The 470s were one of the first single string single spreader classes to figure out that the thing to do is to put so much rig tension on that it makes very little difference to the behaviour of the spreaders whether there's someone dangling off the wire or not...

If you've got 140lbs tension down the shroud and then dangle a 140lb crew off the wire then there is suddenly 0 lbs tension in the shroud and the spreader stops doing much... If on the other hand there's 500lbs down the shroud then when it drops to 360lbs the spreaders are still working pretty much the way they were before...

The other alternatives are not to use spreaders (Laser II, RS600) or to lock out the lower mast throughly with checks and goodness knows what like the skiff two spreader rigs.
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Mikey 14778 View Drop Down
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Posts: 298 		Post Options Post Options   Quote Mikey 14778 Quote  Post ReplyReply Direct Link To This Post Posted: 25 Mar 09 at 5:30pm
It's a bit worse than that Jim. If you've got 140lbs tension in the shroud and hang a 140lb crew on the wire, you're
right that you are unloading the tension in the windward shroud. But you also just loaded up the leeward shroud with
280lb, and that kink that the spreader puts into the leeward shroud wire would like to be straight. So it shoves the
leeward spreader and the mast with it to windward.

Of course we're ignoring the sail here, which is doing precisely the opposite....

But I have observed on my furball that this effect never goes away, even with 570lbs on the shrouds. All that an
increased shroud tension can do is reduce the ratio of tensions, thereby reducing the effect.

You could always ditch the spreaders and adopt diamond wires, which wouldn't suffer this problem and are
(incidentally) still legal on the furball. Might be worth a try....
Fireball 14778 - 'Cruel and Unusual'
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Chas int505 View Drop Down
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Posts: 31 		Post Options Post Options   Quote Chas int505 Quote  Post ReplyReply Direct Link To This Post Posted: 26 Mar 09 at 2:51pm

The 505's all ease off the shrouds as the crew gets out on the wire.  So the big shroud tensions (350-400lbs) are replaced by the crew's weight from about 8/9 knots.  Shroud tension drops to about 320-300 lbs.  Thus the sails stay in the same flying shape....except below 4 kts, when you bend the whole damn thing to keep it working..!

We find that it all works better with the crew on the wire as early as possible(unless it is very choppy, with big holes in the wind).  So when the wind dies off, the crew weight prevents the mast from re-straightening - which would close the leech of both main and genoa....even if the crew bends their legs for the lull, the weight component remains the same at the hounds, where the trap-wire attaches.

Cheers,

 


CW

 

 

 
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MikeBz View Drop Down
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Posts: 536 		Post Options Post Options   Quote MikeBz Quote  Post ReplyReply Direct Link To This Post Posted: 26 Mar 09 at 5:22pm

Originally posted by Mikey 14778

Kinda difficult to explain Mike. Going upwind, when you lean back and get the sail over you, a lot of the
force from the rig (sideways & forwards as well as upwards) travels to the board through your body. If you
happen to be sailing a long-board (ie, one with a centreboard, now deeply unfashionable no doubt), you can
put both feet either on it or on the side adjacent to it and effectively transmit all the sideways force
directly to the board / centre of lateral resistance. This removes a lot of the sideways force that would
otherwise have gone into the skeg, and feels more 'connected'. It also means you've got your legs together,
so look pretty cool

But... but... but... whether the force is applied to the board or the skeg or somewhere in between isn't affected by where you put your feet (assuming you can hold yourself still and not get swung around), it's purely down to where the centre of effort (fore & aft) of the sail is.  Everything must balance out (ask Newton!).

I would respectfully suggest that there is an advantage in having your feet/legs together (apart from looking cool) in that you're keeping your mass concentrated in the middle, i.e. reducing the fore-and-aft moment of inertia ("keeping the weight out of the ends" in common parlance).

Mike
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Roy Race View Drop Down
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Posts: 275 		Post Options Post Options   Quote Roy Race Quote  Post ReplyReply Direct Link To This Post Posted: 26 Mar 09 at 6:33pm
Originally posted by Chas int505

The 505's all ease off the
shrouds as the crew gets out on the wire.  So the big
shroud tensions (350-400lbs) are replaced by the crew's
weight from about 8/9 knots.  Shroud tension drops to
about 320-300 lbs.  Thus the sails stay in the same
flying shape....except below 4 kts, when you bend the
whole damn thing to keep it working..!


We find that it all works better with the crew on the
wire as early as possible(unless it is very choppy, with
big holes in the wind).  So when the wind dies off, the
crew weight prevents the mast from re-straightening -
which would close the leech of both main and
genoa....even if the crew bends their legs for the lull,
the weight component remains the same at the hounds,
where the trap-wire attaches.
Cheers,

CW



It never ceases to amaze me how boats which in the grand
scheme of things appear to be very similar - in this
case, 505's, 470's and Fireballs - arrive at such very
different solutions for rig set-up.

The 470s have crazy rig tension (like 400lbs on the
FORESTAY), and long-ish spreaders with a moderate amount
of pre-bend locked in. The high rig tension serves to
keep the whole rig quite static and like JimC said,
reduces the effect of the crew on the wire.

Fireballs have arrived at a straighter rig, shorter
spreaders and less rig tension. Why, I have no idea, but
it seems to work.

And 505's are constantly fiddling with their rig
tension!

I'd have thought that single string, single spreader,
alloy mast symmetric kite dinghies would all present
roughly the same problems and therefore the top crews
would arrive at roughly the same rig set-ups, but it
doesn't seem to be the case at all.

Just an observation...
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Noah View Drop Down
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Posts: 611 		Post Options Post Options   Quote Noah Quote  Post ReplyReply Direct Link To This Post Posted: 26 Mar 09 at 7:20pm
Considered opinion recommends 400lb on the jib luff for a Fireball that'll take it...
Nick
D-Zero 316

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