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G.R.F. View Drop Down
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    Posted: 21 Jan 11 at 9:31am
Not a big fan of anyone called "Bethwaite". Believe it or not, I do know a bit about 'drag' on "Hulls" have been wrestling with it on and off for close on forty years, both engine and sail powered, as an amateur and in a professional capacity, so in my total arrogance, I'm minded there's not much I'd learn from some Convict who designed a boat that clearly doesn't work unless you have the rest of your life to spend practising and only then if the sea doesn't move around too much. I'd trust our boys over Bethwaite any day of the week

Whereas I don't know if two split planing surfaces give better support than the sum of their surface thereby permitting  reduced contact over a wider area.

This will either prove or disprove that theory as well as giving me something fast and easy to play with.

One thing I am reasonably confident in achieving.. and that is kicking D1 backside all over the Ocean. Wink

Edit: Doesn't look like many other folk like Bethwaite either judging by his facebook page




Edited by G.R.F. - 21 Jan 11 at 9:39am
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winging it View Drop Down
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Posts: 3958 		Post Options Post Options   Quote winging it Quote  Post ReplyReply Direct Link To This Post Posted: 21 Jan 11 at 9:45am
Originally posted by G.R.F.

Originally posted by winging it

Is it me.

It's just you, is that a plate I can see in the sink that needs washing?


The only plate I care about is the titanium one going in the back of my hand any time soon.....good excuse to get out of the ironing for another year though.

Early moth info, inc tunnel hulls.
the same, but different...

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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 21 Jan 11 at 9:50am
Originally posted by G.R.F.

Not a big fan of anyone called "Bethwaite". Believe it or not, I do know a bit about 'drag' on "Hulls" have been wrestling with it on and off for close on forty years, both engine and sail powered, as an amateur and in a professional capacity, so in my total arrogance, I'm minded there's not much I'd learn from some Convict who designed a boat that clearly doesn't work unless you have the rest of your life to spend practising and only then if the sea doesn't move around too much. I'd trust our boys over Bethwaite any day of the week

Whereas I don't know if two split planing surfaces give better support than the sum of their surface thereby permitting  reduced contact over a wider area.

This will either prove or disprove that theory as well as giving me something fast and easy to play with.

One thing I am reasonably confident in achieving.. and that is kicking D1 backside all over the Ocean. Wink
 
He He.
 
Actually he does comment on the boards and how good they are at making hulls.
 
He designed the Tasar ( you don't need too much training for that ) and it was his comments about hull "fine entry" and drag that lead to the Tasar hull design that lead me to believe that you might have trouble when it gets wavey with your current diagram design.
And given your design brief I thought you might be interested.
 
It's your requirements for "all round" conditions performance I think you may have trouble.
Interesting though.
Good Luck.....(kicking my backside that is) LOL
 
Timg
 
 
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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: 21 Jan 11 at 9:59am
I'm not sure if I mentioned, this is a second attempt, the first failed badly by being a tad too small and not that well built (I used wood), I'll try and find a picture of  the now infamous 'Water Pusher' as my nephew christened it at Weymouth speed week.


It failed because the nose didn't contain enough volume to spring the device onto the plane in order to engage the twin surfaces.
 It was overwhelmed by mast foot pressure, something I've come to realise is even greater on a dingy than it is on a board where it is at least dynamic.

The down force on the nose of even that RS100 is immense even in relatively light wind, I noticed it once whilst trying to trail it rigged down the beach in an offshore wind, virtually impossible to lift the tailor in the puffs, which is why the nose of the V Twin has so much volume, which, once on the plane should come clear. Obviously it will bounce down in waves, but again hopefully with so much comparitive volume it should quickly bounce back up again with out going down the mine.

Anyway that's my thinking and how I've come to all this.
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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 21 Jan 11 at 10:56am
Originally posted by G.R.F.



Whereas I don't know if two split planing surfaces give better support than the sum of their surface thereby permitting  reduced contact over a wider area.

Dan Holman will be well familiar with Savitsky's work on planing hulls, but just for you grumph...
http://www.boatdesign.net/forums/attachments/boat-design/12703d1177638152-savitskys-papers-savitsky_brown_76.pdf
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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: 21 Jan 11 at 11:40am
Originally posted by Peaky

Originally posted by G.R.F.



Whereas I don't know if two split planing surfaces give better support than the sum of their surface thereby permitting  reduced contact over a wider area.

Dan Holman will be well familiar with Savitsky's work on planing hulls, but just for you grumph...
http://www.boatdesign.net/forums/attachments/boat-design/12703d1177638152-savitskys-papers-savitsky_brown_76.pdf

Yes I've seen that before when I was trying to calculate a 'rough guide' to planing surface v sailor weight on windsurf boards, we ended up with board width = 10% of sail size and board volume in litres = approx sailor weight in kilos.. 

Which was when boards started being marketed by volume rather than length.

Then width came in and screwed the equation.

There is nothing absolute, it's like flight, the more you look into it, the more 'theoretical' equations appear and the more you realise no-one knows, well, not absolutely.

Take all the calculations then take them to the Red Sea and Compare the result with what happens on Q.M. reservoir. Same with wind and sails, test a sail here in the cold damp atlantic breeze, then try and get it to perform the same in the faster less dense saharan spin off.

At the end of the day, the only answer ever is 'suck it and see' and even then it wont taste the same to someone else.
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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: 21 Jan 11 at 11:41am
Originally posted by jwlbrace

Originally posted by G.R.F.

 

One thing I am reasonably confident in achieving.. and that is kicking D1 backside all over the Ocean. Wink


in that design?  me thinks not...

Oh and don't exclude yourself from that arse kicking - yours will come. Wink
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WoodenBoatLuvver View Drop Down
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Posts: 40 		Post Options Post Options   Quote WoodenBoatLuvver Quote  Post ReplyReply Direct Link To This Post Posted: 22 Jan 11 at 10:11pm
the cats retirement home?
no, kitty litter



Edited by WoodenBoatLuvver - 25 Jan 11 at 7:32pm
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ex laser View Drop Down
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Posts: 725 		Post Options Post Options   Quote ex laser Quote  Post ReplyReply Direct Link To This Post Posted: 22 Jan 11 at 10:12pm
as a person who likes scows its so nice to see g.r.f re-invent the wheel ie; tunnel moths 
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Rupert View Drop Down
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Posts: 8956 		Post Options Post Options   Quote Rupert Quote  Post ReplyReply Direct Link To This Post Posted: 23 Jan 11 at 9:47am
Only it is backwards to a tunnel Moth, where the tunnel forward was to promote lift, with planing sections aft, so the theories are rather different. The Moth was bound by class rules to prevent Catamarans, though. Not sure what GRF is bound by...
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