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NickM
United Kingdom
53 Posts |
 Posted - 08 Mar 2012 : 21:24:49
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Following a thread on another sailing forum I spootted that a fellow sailor has come up with a spreadsheet formula to calculate the potential handicap of new dinghies. He says it needs careful interpretation - like any data feeding into a handicapping system - but is indicative. Anyway I asked him to input the stats of the Stratos C/B vs the Keel, which he did very kindly and this a summary of what he told me:
"Laser are now claiming that the boat is lighter and more heavily canvassed than they did when I input the data originally. Then again, who knows - for years they claimed the L2000 had a hull weight of 100kg, but finally conceded it was 140!
Overall, my sheet suggests a PN of 1074 for the c/board and 1125 for the keel. I'm assuming there that you are supposed to sail the boat upright, like an ff, so don't actually get any benefit out of the keel when sailing optimally.
How the difference pans out across the wind range, is as follows:
In very light airs, there's not much in it: 1113:1129, c'board:keel versions respectively.
There is a great myth that weight mostly affects light airs performance - that's just not so. Light airs is all about wetted surface drag and that doesn't in fact vary very much with weight. That's why I can beat V3000's with my Laser 3000 on the water in the light stuff, despite a 15% difference in displacement (boat+crew)
In moderate weather, when you're generating waves, the difference increases to 1086:1119.
Once you get to planing weather and you're either at hull speed or planing, the difference is 1073:1104 when not planing, and 1085:1180 when you are (which is only a small, but critical part of your total race time, of course).
But that's not the entire picture, because in between, in marginal planing weather, the c'boarder will start planing before you, and that's when the biggest differences will occur. I have a formula to estimate that, but in the absence of lots more data it's a bit of a guesstimate.
Not considered also, is the ease of sailing the keel in realy rough weather - I gues you can push it harder, so that can win you back time. So you can see why releasing my sheet on the world would probably mislead as much as it informs!
All those PN figures are relative to a Wayfarer, by the way. Had I made a 3000 the reference boat, for example, you would find that compared to us you'd rate closer to 1030 before we started planing and something like 1200 in a blow - hikers can't touch trapeze boats once the crews start wiring (unless they're upside down, of course!), but it does mean that in mixed PY racing, you should be looking to win in light or v.v.heavy conditions."
I rest my case (though the evidence might be challenged in a court of law!)
NickM |
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Handicaps
