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G.R.F. View Drop Down
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Joined: 10 Aug 08
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Posts: 4028 		Post Options Post Options   Quote G.R.F. Quote  Post ReplyReply Direct Link To This Post Topic: V Twin
    Posted: 19 Jan 11 at 12:00am
Er yes, and someone (maybe you) bought the problem up before, so there's only one way to find out and yes I specc'd it with a retracting plate of at least Contender proportion but with a fast section. Something else that will depend on the final weight, if I don't hit target, I'll probably have to go for a slower section.

I know I often jest and make light of it all as is my ironic way, but there actually is quite a lot to get right to make these things work, just like racing boards which at the end of the day were just dinghies scaled down, well they were in my day.

But back then we didn't have all this fantastic computer stuff, I can't wait til tomorrows conference call to talk about how we go about altering the spec on this print out for example..

Draft Amidsh. m 0.084
Displacement kg 155
Heel degrees 0°
Draft at FP m 0.084
Draft at AP m 0.084
Draft at LCF m 0.082
Trim m 0
WL Length m 4.125
WL Beam m 1.9
Wetted Area m^2 4.534
Waterpl. Area m^2 4.421
Prismatic Coeff. 0.481
Block Coeff. 0.346
Midship Area Coeff. 0.812
Waterpl. Area Coeff. 0.778
LCB to Amidsh. m 0.130 Aft
LCF to Amidsh. m 0.122 Fwd
KB m 0.063
KG m 0
BMt m 8.95
BML m 25.081
GMt m 9.013
GML m 25.144
KMt m 9.013
KML m 25.144
TPc Tonne/cm 0.045
MTc Tonne.m 1.#IO

By the look of it they've run a 155kg crew & rig weight which is probably a bit high, I also over specified the widths of the rear sponsons which probably don't need to be the width they are. I don't want that much wetted area, but then what I'm used to thinking about for a planing hulled board and what I'm going to have to apply to a planing hull, rather than just educated guess (which was what I'd done) can be quite accurately derived from programmes like these.

I wish I'd met these boys twenty years ago, I'd be loaded now.

I fully take back all that windsurfing technologically is way ahead of dinghies, this stuff is brilliant.


Edited by G.R.F. - 19 Jan 11 at 12:02am
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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: 19 Jan 11 at 12:11am
Originally posted by winging it

presumably you've trawled through all the detail on tunnel hull moths?

the rig says 'contender'



No, Wing Wang, if there's any intel you could point me at, I'd like to check it out, Moths have always been a hot bed of quite radical development.
 Which then gets taken from the sublime to the ridiculous until another tangent arrives, Lord knows how they got up on stilts.

Other than searching out what a Scow was, my inspiration for this is more Contender Crossed with Vortex.
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oldarn View Drop Down
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Posts: 440 		Post Options Post Options   Quote oldarn Quote  Post ReplyReply Direct Link To This Post Posted: 19 Jan 11 at 11:45am
Originally posted by G.R.F.



Other than searching out what a Scow was, my inspiration for this is more Contender Crossed with Vortex.


Most interesting idea, and well done for ignoring the usual anti Grumph rhetoric.

You don't need to be a naval architect to have a good idea which might change dinghy sailing fashion.  Clearly the skiff fashion era is now over.

Good luck Graeme

mike
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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: 19 Jan 11 at 12:01pm
Graeme, I need a plate fixing into my hand this spring, so my contender will be lying idle if you want to try it.  I hate to have do this to you, but the best source of info for tunnel hull moths is the cvrda...or the moth site.
the same, but different...

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NickA View Drop Down
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Posts: 784 		Post Options Post Options   Quote NickA Quote  Post ReplyReply Direct Link To This Post Posted: 19 Jan 11 at 12:44pm
If you want more righting moment - why not just fit racks or a trapeze (or both) to the RS100?
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Ruscoe View Drop Down
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Posts: 1514 		Post Options Post Options   Quote Ruscoe Quote  Post ReplyReply Direct Link To This Post Posted: 19 Jan 11 at 12:49pm
Nick, I think Graeme wants a more stable platform to start from.
I think its great, i really hope it works.  I wouldn't bother with the 100 rig though as i am sure you could develop something lighter and better suited to the boat for not much money. Not that the 100 rig is heavy i am sure, but a fully adjustable stayed rig has surely got to be better especially if you are going to trapeze off it??!

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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: 19 Jan 11 at 1:06pm
Originally posted by winging it

Graeme, I need a plate fixing into my hand this spring, so my contender will be lying idle if you want to try it.  I hate to have do this to you, but the best source of info for tunnel hull moths is the cvrda...or the moth site.

Lost another massive response even though it involved uploading images.

That's very kind of you.

Sorry to hear of the plate wing wang, although it ought to be an entire kitchen imv.

Where's the Contender lying laying? whatever and where is the nearest water?

I'll come back again with the other renders I lost maybe a bit later.
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oldarn View Drop Down
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Posts: 440 		Post Options Post Options   Quote oldarn Quote  Post ReplyReply Direct Link To This Post Posted: 19 Jan 11 at 1:06pm
Originally posted by G.R.F.



Other than searching out what a Scow was, my inspiration for this is more Contender Crossed with Vortex.


What ever it is about the vortex and the tunnel hull, it is certainly an interesting craft. I have always felt  it could have been slightly longer, but I'm sure Jo Richards chose the optimum length for the tunnel effect.

There is a Vortex sailed  by Alan Grant at our club. it is the only boat to challenge us for line honours and now with a jib but no kite he usually wins. He has used the kite but feels the boat becomes too lethal a weapon amongst other craft on our water. Without the kite he used to sail off 960, but with the jib sails off 955! We sail the AltO off it's realistic PN of 930 and are usually beaten by all streakers and most often by the 200 and the 300's.

Sorry, after my AltO PN plug, back to the Vortex. There is a certain wind strength/sailing angle at which the vortex takes off with incredible acceleration.  I guess the tunnel effect comes in.

And now back to the V Twin. Surely the dinghy designs do incorporate  the good points from others which in this case could be the Vortex, Fireball and Contender. but Graeme don't forget your past, because even sailboards have had some good design features. What about incorporating the swinging c/b which rotates up under the hull into the tunnel.  At Hythe you could then have a 'how far up the beach' trophy without damaging the hull. Just the gell! Dont go for epoxy!

Mike
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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 19 Jan 11 at 1:11pm
I reckon you'll want a pretty big rig with that hull as the initial stability, righting moment and wetted surface area are all very high. Maybe an RS700 rig?
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sailfree View Drop Down
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Posts: 3 		Post Options Post Options   Quote sailfree Quote  Post ReplyReply Direct Link To This Post Posted: 19 Jan 11 at 1:16pm
Originally posted by oldarn

Originally posted by G.R.F.



Other than searching out what a Scow was, my inspiration for this is more Contender Crossed with Vortex.


What ever it is about the vortex and the tunnel hull, it is certainly an interesting craft. I have always felt  it could have been slightly longer, but I'm sure Jo Richards chose the optimum length for the tunnel effect.

There is a Vortex sailed  by Alan Grant at our club. it is the only boat to challenge us for line honours and now with a jib but no kite he usually wins. He has used the kite but feels the boat becomes too lethal a weapon amongst other craft on our water. Without the kite he used to sail off 960, but with the jib sails off 955! We sail the AltO off it's realistic PN of 930 and are usually beaten by all streakers and most often by the 200 and the 300's.

Sorry, after my AltO PN plug, back to the Vortex. There is a certain wind strength/sailing angle at which the vortex takes off with incredible acceleration.  I guess the tunnel effect comes in.

And now back to the V Twin. Surely the dinghy designs do incorporate  the good points from others which in this case could be the Vortex, Fireball and Contender. but Graeme don't forget your past, because even sailboards have had some good design features. What about incorporating the swinging c/b which rotates up under the hull into the tunnel.  At Hythe you could then have a 'how far up the beach' trophy without damaging the hull. Just the gell! Dont go for epoxy!

Mike


I don't think the Vortex tunnel effect hull actually works does it? Someone once told me it was just a bit of marketing talk....
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