For iGRF: New tunnel hull dinghy concept
Printed From: Yachts and Yachting Online
Category: Dinghy classes
Forum Name: Dinghy development
Forum Discription: The latest moves in the dinghy market
URL: http://www.yachtsandyachting.com/forum/forum_posts.asp?TID=12658
Printed Date: 07 Jul 25 at 6:17am
Software Version: Web Wiz Forums 9.665y - http://www.webwizforums.com
Topic: For iGRF: New tunnel hull dinghy concept
Posted By: skslr
Subject: For iGRF: New tunnel hull dinghy concept
Date Posted: 10 Feb 17 at 11:58am
http://www.brainstorm-sail.de/en/home/ 
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Replies:
Posted By: fab100
Date Posted: 10 Feb 17 at 12:21pm
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Help me, I don't get it - the immersed part of the hull is not fore and aft but at an angle to the direction of travel (given the hull is sort-of triangular). Hence, energy from the rig is needed to push water sideways. How can that be efficient? Alternatively, the boat sort of crabs sideways, in which case the foils cannot be lined up fore and aft but offset, so you have to raise and drop a plate on each tack/gybe or they'd fight each-other. This is why I am not a boat-designer...
------------- http://clubsailor.co.uk/wp/club-sailor-from-back-to-front/" rel="nofollow - Great book for Club Sailors here |
Posted By: tgruitt
Date Posted: 10 Feb 17 at 1:01pm
BS-15, the name says it all.... ------------- Needs to sail more... |
Posted By: iGRF
Date Posted: 10 Feb 17 at 1:21pm
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Who was it on here that came up with almost exactly that design when I was postulating about the V2, the guy on the IOW makes Canoes, Foils and things, my memory is just f**ked, blue something or other, anyway he had a CAD drawing for a similar triangular approach, it ovbiously relies on being heeled and the lee side gives it forward direction it wouldn't necessarily go sideways, well no more than a conventional hull makes leeway.
It's basically the same idea I was trying, to ditch half the wetted surface on the upwind leg and the tunnel affords a wide stern for stability with less wetted area, I was perhaps trying to be a bit too clever with a three stage rocker and wanting it to plane, which it did on flat water, but didn't so well in waves, I under estimated the downforce at the nose that dinghies suffer with, never something we're really aware of with free rigs that we windsurferssail with since they get canted over. Knowing what I'm now aware of I would probably have done that V2 differently with a more rounded underside than a flat planing hull, it would probably have worked just the same but not have been as sticky in the light nor as difficult to transition from displacement through gliding into planing although I'm not convinced any dingy actually planes at all in the same sense we windsurfers know as planing, actually skipping over the water surface, probably why foiling offers such efficiency and in truth is probably a better future direction. ------------- https://www.corekite.co.uk/snow-accessories-11-c.asp" rel="nofollow - Snow Equipment Deals https://www.corekite.co.uk" rel="nofollow - New Core Kite website |
Posted By: JimC
Date Posted: 10 Feb 17 at 1:32pm
I imagine some kind of gybing foil could be arranged. Making a fair and smooth hull/foil junction could be challenging as it would have to move through a very large angle. |
Posted By: tgruitt
Date Posted: 10 Feb 17 at 2:08pm
Bloodaxe Boats? ------------- Needs to sail more... |
Posted By: iGRF
Date Posted: 10 Feb 17 at 5:06pm
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Yep Andy something from Bloodaxe foils he had a cad drawing which could be that boat. ------------- https://www.corekite.co.uk/snow-accessories-11-c.asp" rel="nofollow - Snow Equipment Deals https://www.corekite.co.uk" rel="nofollow - New Core Kite website |
Posted By: Sam.Spoons
Date Posted: 10 Feb 17 at 5:29pm
| Upwind the leeward 'keel line' would be lifting the boat to windward. The DB on the drawing on the media page seems to be at a slight angle to that 'keel line' but taking the boat to leeward. You'd really want the DB's toed in by slightly more than the angle between the 'keel lines' and the centreline, a bit like a gybing board but fixed. And, yes you would need to lift the windward on or suffer considerable drag. The whole thing's been done before anyway, they called it The Vortex...... |
Posted By: Presuming Ed
Date Posted: 10 Feb 17 at 6:46pm
Easier as they've shown it - two (asymmetric?) foils. Deploy one at a time.
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Posted By: I luv Wight
Date Posted: 10 Feb 17 at 7:55pm
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yeah I did a design concept for V2+ ... triangular, asymmetric boards - i just have to find it!
------------- " rel="nofollow - http://www.bloodaxeboats.co.uk" rel="nofollow - http://www.bloodaxeboats.co.uk Andy P foiling Int Moth GBR3467 Freedom 21 Codling |
Posted By: I luv Wight
Date Posted: 11 Feb 17 at 10:51am
------------- " rel="nofollow - http://www.bloodaxeboats.co.uk" rel="nofollow - http://www.bloodaxeboats.co.uk Andy P foiling Int Moth GBR3467 Freedom 21 Codling |
Posted By: Rupert
Date Posted: 11 Feb 17 at 12:36pm
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So, presumably the boat simply looks like it isn't pointing very high, but the leeward hull is facing the same way as all the other boats?
Why go to so much trouble to design something just so it isn't a catamaran? ------------- Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686 |
Posted By: RS400atC
Date Posted: 11 Feb 17 at 12:51pm
So we talk about it on here perhaps? What happens in choppy water? It would need to be nearly capsized to keep the windward hull out of Solent chop! |
Posted By: iGRF
Date Posted: 11 Feb 17 at 2:08pm
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My logic for not wanting a catamaran was simply because they nearly always trip over the lee hull and cartwheel in the waters off here when you're punting them hard, so I wanted the benefit of twin hull without the negatives, I still think that part of the idea is relevant, what was questionable was going for planing hulls rather than rounded displacement.. ------------- https://www.corekite.co.uk/snow-accessories-11-c.asp" rel="nofollow - Snow Equipment Deals https://www.corekite.co.uk" rel="nofollow - New Core Kite website |
Posted By: Rupert
Date Posted: 11 Feb 17 at 2:18pm
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Something with a topper shape but hollowed out would give better angles, surely? Tunnel hull scows have been around for a long time, but Moth rules limited what they could do. The Vortex went too cat like, in some ways, so the "gap" (one boat?) is still there! ------------- Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686 |
Posted By: Cirrus
Date Posted: 11 Feb 17 at 3:26pm
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So how on earth would it work on a reach or downwind - always flying one side of the 'hull' ? Sounds tricky because if you don't it inevitably has the hydrodynamic shape of a brick - complete with 'toed-in' foil(s) to put a further damper on progress. The only variant of this I've ever seen work well was Shaun Cox's unique board more than 25 years ago with 2 'bows' coming to a common aft section with conventional single pivoting board. It had a fair bit of rocker and this allowed him to sail it relatively flat on the reach and/or offwind by keeping the bow(s) largely clear of the wet stuff. It worked very up and down wind. |
Posted By: Sam.Spoons
Date Posted: 11 Feb 17 at 3:32pm
Yup, so the powers that be changed the rules to outlaw it 
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Posted By: Cirrus
Date Posted: 11 Feb 17 at 6:10pm
Yup, so the powers that be changed the rules to outlaw it  And just look where their other 'edicts' for the good of the sport soon got them ... disaster and rapid decline snached from the jaws of wild success.... so long ago now I can hardly remember who exactly was involved - probably just as well....  |
Posted By: Sam.Spoons
Date Posted: 11 Feb 17 at 6:32pm
| 'Oop North', at about the same time, Martin Page, John (and possibly Roger) Tushingham and the Escreet brothers were involved in the design of the PET which went on to become the Free Radical Div 1. basically a rectangular cross section with a rounded plum bow a bit like a Lark. Very quick in the typical inland light stuff, quick too in a blow but not the easiest thing to gybe. Then, as we said, they changed the rules......... |