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Dinghys with keels

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Sam.Spoons View Drop Down
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    Posted: 18 Jan 17 at 9:42am
Not sure where to put this one but I was watching the 2.4s training on Sunday in 15-20 knots and thinking about Eric Twiname's classic bit of dinghy advice about sailing the boat flat. Obviously the 2.4 is a full on keelboat so I assume the hull form is designed to sail well at 45+ of heel. Dinghies are designed to be most efficient with less than, say, 5-10 heel. So what about 'dinghy keelboats' like the VXOne (and bigger 'sports boats' like the Melges 24 et al). I guess their hull shapes cover the spectrum from VXOne (pure dinghy hull, hiked like a dinghy, best sailed flat) and optimised for increasing angles of heel as they get bigger and crew weight becomes a smaller percentage of the whole?
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Post Options Post Options   Quote zippyRN Quote  Post ReplyReply Direct Link To This Post Posted: 18 Jan 17 at 11:51am
i think you've  recognised the funamentals of it 

if you look at  Uffa's smaller 'Flying'  boats ,  the 15  being the best known they are  dinghys with  keels , ditto something like the Tempest ... 

I suppose there is a line to be drawn   with regard to whether the boat is hiked ( or  trapezed)  or  whether it has guard rails / wires and the  windward side  self moving ballast sits facing outwards  ... 
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Sam.Spoons View Drop Down
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Post Options Post Options   Quote Sam.Spoons Quote  Post ReplyReply Direct Link To This Post Posted: 18 Jan 17 at 12:08pm
Yes, that's what I was thinking, Ultra 30s and their ilk being an extreme case in one direction. It was a reference to the VX-One and looking at the Yachting World video review that set me thinking today. Just a skiff with a bit of lead in the daggerboard by the looks of it.
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Post Options Post Options   Quote blueboy Quote  Post ReplyReply Direct Link To This Post Posted: 20 Jan 17 at 6:07am
FF is not a dinghy. It is a keelboat. There are no dinghies with keels. If it has a keel it is a keelboat.
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Post Options Post Options   Quote Rupert Quote  Post ReplyReply Direct Link To This Post Posted: 20 Jan 17 at 8:00am
I think the OP knows that...

I seem to remember that Paul Handley designed the K1 to work well when heeled. Bet they sail them flat, though! The rig must be more efficient upright even if the hull is good heeled.
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Post Options Post Options   Quote Wiclif Quote  Post ReplyReply Direct Link To This Post Posted: 20 Jan 17 at 6:26pm
The K1 is quite narrow, and since you don't get that same build up of weather helm with a narrow boat when heeled, this means that the tiller still feels quite light, even at the normal 30 degree heel if it is breezy.

And the keel isn't really going to keep the boat upright until it heels a bit, so it just works.

But yes, you still want to keep it as flat as possible, though with 11 sq m of sail it is not underpowered
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Post Options Post Options   Quote Sam.Spoons Quote  Post ReplyReply Direct Link To This Post Posted: 20 Jan 17 at 6:35pm
My take is that a fixed (i.e. non canting) keel has zero righting moment when the boat is flat/upright so it's impossible to sail a keelboat flat without moving ballast (or 'crew' as it's known) on the windward side. Even in a drifter there will be a little heel. The effect of the ballast will depend on a number of things including how far from the centreline they can get and weight relative to the displacement of the boat and it's ballast ratio. So 10 blokes wiring of the racks of an Ultra 30 make a huge difference but a couple sitting on the windward rail of a J24 have a relatively small (but obviously still useful) effect.
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Post Options Post Options   Quote zippyRN Quote  Post ReplyReply Direct Link To This Post Posted: 23 Jan 17 at 5:13pm
Originally posted by blueboy

FF is not a dinghy. It is a keelboat. There are no dinghies with keels. If it has a keel it is a keelboat.

i think you've missed the point of the OPs question 


despite the hull form  of the Flying boats , despite the fact that  everyone from Uffa  onwards sails them like dinghies in terms of  'flat ' being fast ...  and we've seen subsequent designs of that  nature of a hiked / trapezed  planing  keelboat that  sail in  dinghy like manner  (  although  the last 30 or so  years of ULDB  yachts  had muddied the hull form waters especially  with regard to planing like behaviours  )
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Sam.Spoons View Drop Down
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Post Options Post Options   Quote Sam.Spoons Quote  Post ReplyReply Direct Link To This Post Posted: 23 Jan 17 at 5:33pm
Those Vendee Globe boats look like huge dinghies when their doing 25 knots + off wind. I wonder how long it takes to tack one...... the list of tasks must run :- pump the ballast from one side to the other, cant the keel, lift the windward daggerboard and lower the leeward one, turn the boat and re-sheet the foresail..... And probably several other jobs too.
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Post Options Post Options   Quote ColH Quote  Post ReplyReply Direct Link To This Post Posted: 06 Feb 17 at 8:14pm
Originally posted by blueboy

FF is not a dinghy. It is a keelboat. There are no dinghies with keels. If it has a keel it is a keelboat.



It can plane though - it's a bit odd but a real buzz.
Like the 470 - maligned for being 'old hat', but still very classy, and unrivalled by many of the newer classes despite being decades old....
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