Laser 161752 Tynemouth |
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Laser 28 - Excellent example of this great design Hamble le rice |
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Laser 140101 Tynemouth |
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List classes of boat for sale |
Gybing Plates |
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JimC ![]() Really should get out more ![]() ![]() Joined: 17 May 04 Location: United Kingdom Online Status: Offline Posts: 6662 |
![]() ![]() ![]() ![]() Posted: 26 Jan 16 at 9:44pm |
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I think he's more wrong than right though. It is striking that all the classes I know of where they seem to have gained a significant measure of popularity are two sail classes. I see two possible factors. They're all about the fact that what gybing boards do is in effect rotate the hull round the foil. So the first effect is that if you get the gybe angle right then the hull centreline is aligned with the direction of travel, not crabbing by two degrees or whatever. I used to think that was probably insignificant, but I've seen some calculations by someone I respect which suggests it isn't. The second effect is that the alignment of jib and mast changes (if you have a jib). The 505 guy goes into great flights of enthusiasm, in which I think he's forgotten that sailors sheet their sails relative to the apparent wind, not the hull, but nevertheless there is a change in an area where I find tiny changes matter. As for the weight thing, well, yes, if your gybing board arrangement means you have a fatter case than someone without one, then that is a little more weight. Not convinced about the significance though. Edited by JimC - 27 Jan 16 at 11:36am |
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maxibuddah ![]() Really should get out more ![]() ![]() Joined: 06 Mar 09 Location: United Kingdom Online Status: Offline Posts: 1760 |
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Draftsight is a free 2D CAD program that runs on windows, Linux and Mac. The link to the download pageis http://www.3ds.com/products-services/draftsight-cad-software/free-download/ Its from the same people who make Catia and Solidworks and is a pretty straight copy of autocad. Only does 2D stuff though
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Everything I say is my opinion, honest
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iGRF ![]() Really should get out more ![]() ![]() Joined: 07 Mar 11 Location: Hythe Online Status: Offline Posts: 6499 |
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Yep even we used to try that in light weather with a foam block but it really doesn't make much difference unless of course your flushing strips are not cutting it as they should, which at championship level you really couldn't afford to happen, back in the day some of us would have a fresh set every major event.
The key thing about water in the centreboard case, isn't wether it's there or not, it's how badly it's moving about. Edited by iGRF - 26 Jan 16 at 7:38pm |
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RS400atC ![]() Really should get out more ![]() Joined: 04 Dec 08 Online Status: Offline Posts: 3011 |
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Some people stuff the centrebox, instead of relying on slot gaskets. |
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iGRF ![]() Really should get out more ![]() ![]() Joined: 07 Mar 11 Location: Hythe Online Status: Offline Posts: 6499 |
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That guy if you'll pardon my impatience is talking bollox. So much crap in what he was saying then, typical example of a good sailor having an opinion, juxtapositioning facts to support it and I can't be asked to pull it all apart, but he's wrong. Allthough I'm grateful nonetheless for you posting me a link I will have to come back to it later some of those equations annoyed me..
![]() Carrying 2 kgs of water around in the centreboard case, yeah right... Whatever water is there, is there regardless and any more or less is a result of the efficiency or inefficiency of flushing strips, now attention does have to be paid to them if you are going to use gybing plates, but it's not beyond the wit of man to overcome. Edited by iGRF - 26 Jan 16 at 7:54pm |
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GarethT ![]() Really should get out more ![]() ![]() Joined: 21 Apr 07 Online Status: Offline Posts: 714 |
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I vaguely recollect an article by a top OK sailor in the eighties where he said that any benefit from gybing a board had to be offset by the weight of the extra water you carried round in the centreboard case.
Edit: found it http://www.okdia.org/boat/manual/tm2_work.php Edited by GarethT - 26 Jan 16 at 6:07pm |
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iGRF ![]() Really should get out more ![]() ![]() Joined: 07 Mar 11 Location: Hythe Online Status: Offline Posts: 6499 |
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Thanks, and I know what you're thinking, it wasn't me, I've got an alibi!.. |
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davidyacht ![]() Really should get out more ![]() Joined: 29 Mar 05 Online Status: Offline Posts: 1345 |
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Yep really sad, something we worry about in Salcombe, 80% of the Active Yawl fleet are in two barns, albeit on different sides of the estuary.
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Happily living in the past
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gordon1277 ![]() Really should get out more ![]() Joined: 24 Mar 10 Location: United Kingdom Online Status: Offline Posts: 665 |
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Hi GRF
Have a look at a free download called Trueview which allows you to view and plot CAD files. Gordon What a shame about all the boats lost at Cowes some peoples years of effort in restoration just gone plus classics we will never see again. Awful for all concerned. |
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Gordon
Lossc |
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davidyacht ![]() Really should get out more ![]() Joined: 29 Mar 05 Online Status: Offline Posts: 1345 |
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There was a level of how helpful I was intending to be, and do my day job! In essence our board had a diamond shaped head, which was slightly thrupenny bitted at the shoulders. It worked fine. My experience was that the biggest gain was by sailing slightly free, relative to how high you could point, but being really powered up, so in the 12's the biggest gain was if you were heavier, rather than lighter and feathering. My suggestion to GF would be to make a template of the centreboard case and of the centreboard head section and trim the head section to achieve the desirable gybe angle. If the board was not loaded up it could slop around a bit. I know that Ray Rouse's 14 had a device that locked the board when the board was retracted. There is a view that the boards can "self" steer downwind, don't think that this is a problem on the run, but could be on a reach, but I never found this to be the case. We used all of the efficiency gains of the centreboard and rudder to reduce the foil areas. With hindsight probably a little too much, since there was a cost in getting flow going in dead boat situations.
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Happily living in the past
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