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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: Wiki Sail by GRF
    Posted: 27 Mar 13 at 12:38pm


I think you lot are ignoring the loads that go through the rig..
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fab100 View Drop Down
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Post Options Post Options   Quote fab100 Quote  Post ReplyReply Direct Link To This Post Posted: 27 Mar 13 at 12:41pm
Daniel

You are my hero!

Clive
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Daniel Holman View Drop Down
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Post Options Post Options   Quote Daniel Holman Quote  Post ReplyReply Direct Link To This Post Posted: 27 Mar 13 at 12:44pm
There is no horizontal component to the aerodynamic force on the rig unless sailing upwind with significant heel - i.e. not in this case. Those lasers are sailing in chop of length and height equivalent to the length and freeboard of the boat, and are making about 6 kts through the water, so plenty of bow wave. This is when the extra 25cm above the static waterline could be said to make a difference.

Another effect is squat - prob less significant on boards which are essentially flat, but more curvature in the buttock plane as is a feature of most dinghy hulls to one extent or another goves rise to hydrodynamic forces which suck the boat downwards. This is particularly pertinent in very curved boats (generally synonymous with being heavy for their length) and in the pre-planing speeds, as is the case here.
For a 14ft boat at 6 to 8 kts squat can be over an inch.
Obviously when planing (over 12 kts for a 14 ft boat) the CoG actually rises a bit because the craft, if correctly shaped, is now generating hydrodynamic lift
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winging it View Drop Down
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Post Options Post Options   Quote winging it Quote  Post ReplyReply Direct Link To This Post Posted: 27 Mar 13 at 12:54pm
it's all going to end in tears...
the same, but different...

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Post Options Post Options   Quote fab100 Quote  Post ReplyReply Direct Link To This Post Posted: 27 Mar 13 at 1:04pm
Originally posted by winging it

it's all going to end in tears...

Clap

I think we've been there for some time now: I'm just not sure whether they are tears of frustration or hilarity - or now Dan is aboard, tears of joy that Graeme finally might listen and give it up.

But the fun is far from over - we are now set for another 7 pages about how the rig pushes the hull into the water, unless counter-acted by bubbles in the construction material of course.

I reckon we can get this thread to be longer than the photo one...


Edited by fab100 - 27 Mar 13 at 1:05pm
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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: 27 Mar 13 at 1:07pm
Only one thing will resolve this issue..

Cut the Laser in half, add in the inches and see which goes faster.

Nothing of anything written here will convince me that the bigger of the two lasers will not out pace the smaller of the two around a race circuit under all but full planing conditions.

Edited by iGRF - 27 Mar 13 at 1:09pm
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GarethT View Drop Down
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Post Options Post Options   Quote GarethT Quote  Post ReplyReply Direct Link To This Post Posted: 27 Mar 13 at 1:07pm
I've tried following this thread, and I really can't work out who is winding who up?
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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: 27 Mar 13 at 1:19pm
Originally posted by Daniel Holman

Another effect is squat - prob less significant on boards which are essentially flat,



Not quite



That flat.


So, tell me, there are these two boats, a stock Laser and my Laser which has been professionally cut in half and it's freeboard increased by a couple of inches, you have to race a series with some big money prizes at the end, are you going to ignore the big Laser? (Given it was altered by someone who could build down to weight rather than that last place you used to hang out at)

Edited by iGRF - 27 Mar 13 at 1:21pm
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fab100 View Drop Down
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Post Options Post Options   Quote fab100 Quote  Post ReplyReply Direct Link To This Post Posted: 27 Mar 13 at 1:22pm
Originally posted by iGRF

Only one thing will resolve this issue..

Cut the Laser in half, add in the inches and see which goes faster.

Nothing of anything written here will convince me that the bigger of the two lasers will not out pace the smaller of the two around a race circuit under all but full planing conditions.

I think we've now got to the point where its not about the physics anymore (hint: listen to Dan - he actually knows what he's talking about) but about your desire to attack a laser with a chainsaw. 

If you ran a poll for that, James for one would vote with you. In fact, I would love to see your 3 foot freeboard laser, weighing twice the standard hull. 

So do it. If it floats with less hull in the water than a bog-standard one, as you insist, I'll personally drive to Kent and buy you a beer
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Post Options Post Options   Quote Rupert Quote  Post ReplyReply Direct Link To This Post Posted: 27 Mar 13 at 1:24pm
I can see that greater freeboard might help in no wind when heeled over to leeward, as the deck would take longer to hit the water, and down wind when heeled to windward for the same reason. I'm not sure that the first one is the main thing on the mind of a designer, and the second one has the downside that the CofG of the helm is now higher up, making the boat less stable when in an already slightly wobbly position.

The idea that extra freeboard makes a boat go faster is just amazing. The Mirror16 must have been the quickest thing out there - same length as a 49er, but far more freeboard...
Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686
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