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V Twin

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bferry View Drop Down
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Post Options Post Options   Quote bferry Quote  Post ReplyReply Direct Link To This Post Topic: V Twin
    Posted: 30 Aug 11 at 11:18am
Maybe a sufboard type leash would ensure that the boat stays attached to you, provided its safe to wear. 
 
Or.. you could sail with a pair of flippers on to make you swim faster Tongue
Bernard
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2547 View Drop Down
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Post Options Post Options   Quote 2547 Quote  Post ReplyReply Direct Link To This Post Posted: 30 Aug 11 at 10:08am
GRF with the flotation in the rig and the solid wings I fear you risk your contraption will blow downwind much faster than you can swim should you ever become seperated on a windy day.

I know you say only an imbecile could capsize it ... but it's worth considering the "what ifs" ... easy to slip and fall over the side, or miss a toe strap should you decide on some mild hiking.
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Post Options Post Options   Quote Hughph Quote  Post ReplyReply Direct Link To This Post Posted: 29 Aug 11 at 8:56pm
Sounds like a great idea, but how would the cunningham work with the inflatable luff?
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Post Options Post Options   Quote boatshed Quote  Post ReplyReply Direct Link To This Post Posted: 29 Aug 11 at 8:00pm
Originally posted by G.R.F.

'mains with jibs' always seem prone to backing which I don't actually like,


And often noticeable on yachts.   This is generally because there is a fault in the cut of the jib.   It is impossible to keep the jib luff straight as it always sags.  This causes the camber of the jib to change and in many cases the jib leech hooks, backing the mainsail behind the mast.

The jib camber needs to be the same or slightly reducing all the way up to the head.  If it increases due to luff sag, even the best mainsail will back wind. 

A sail maker has to account for jib luff sag and cut a corresponding hollow into the jib luff to compensate and keep the camber even or slightly reducing towards the head.

Of course there are other reasons for mainsail back winding but when not over powered and both jiob and main are pinned in and  boat is upright, this is the main reason. 


Steve
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Post Options Post Options   Quote G.R.F. Quote  Post ReplyReply Direct Link To This Post Posted: 29 Aug 11 at 6:59pm
Originally posted by Hector

Originally posted by boatshed

Have a look at the first few moments of this video

http://www.youtube.com/watch?v=D-kTmlCxvh8

Stop the movie when the boat is on it's side.  JimC said they are ok to right.   I think this is because they have twin dagger boards.  It is very easy to get from the water to the lower board and then hang on to the upper board.

Your Vtwin has a board in the middle and it will be very hard to get on to.   Unless..... the crafty tunnel under the hull is a useful step !


Woo hoo that was me in the Video. It was unusually sudden - or maybe my reactions are shot and I need a V twin?
Graeme - as you know, I've been following this on facebook, but here are some more thoughts.
  • You'll need to know if things you try have worked, or not, so in the absence of a tune up partner, next time, fit a GPS - better to know relative speeds than speculate.
  • I've always thought the Vortex main (that you're using) is a bit open at the leach - at least on the softish mast used. That looks like it could be a Vortex mast as well and if so, maybe upper stays have stiffened it sideways? Anyway when you do go for a custom rig, consider how you're going to adjust it to allow hardish leach for height in lightwinds and open for higher winds.
  • In stacks of wind, going forward  to grab a new kite sheet is bad news. So get a kite designed to sheet from as far aft as practicable. 
  • Vortex main is not optimised for a jib - improvement available there.
  • It might be very difficult, but it if you take it out in enough wind, it will capsize - simple physics. So, RE Righting it, Vortex is easy to get from turtle, so I dont see why this should be any different. Nonetheless, a righting line and/or flotation may not be a bad idea to start with. And try it in a deliberate lightwind capsize first - not after a  F6 wipeout.
  • Love the idea of inflatable bladder in luff - hoisting and lowering would be an issue but idea has huge potential
  • Dont talk up the speed too much - unless you want a PY of sub 800! Wink
My initial  scepticism is partly removed, but unless it tacks like a dinghy, it may not fulfil one of your wishes  (that you can enjoy close 'tactical' racing. Any comment on how it tacks?  I guess it will need to be compared to the like of an MPS, Contender or Vortex rather than a Laser / RS200.

Well done again for putting your money and time into this.

It tacks really well, got back in the Alto yesterday and now can't wait to get out of it. The only thing I don't like the look of is the lee side bow wash, but that's me nit picking, it gybes as sweetly as it tacks, even with the kite up. The kite goes up and down better than anything I've ever experienced, point taken about the Vortex, the mast is an RS700 mast, I'm wondering if it's a bit soft for that Vortex main.
 I plan to make what I can best describe as an Air batten sail, like a kite surfing kite, so the leading edge will have an air bladder, maybe with split batten either side of the mast maybe not, it might be too complex, but definitely air bag battens, anyone familiar with our Slingshot kites and their split strut construction, so the air bags get their air off the main leading edge bladder, a single point inflation system, blow it up to about 8-9 psi they get quite rigid, I've got all the necessary bits to do it at work. I shall probably have conventional battens on the trailing edge, so the sail will be semi soft but the foil should be quite defined yet tuneable. This will fulfill two things, one the sail will be lighter and two, no way will it sink. I'd also thought about messing with the leading edge of the jib in the same way, but conventional wisdom (Jamie) has warned me off messing with the jib. The only thing that's not been done before, is air battens that tack, kites tend to stay on the same tack, so some R&D work will need to be done over the winter.

I don't envision it being anything like as fast on our water and I certainly don't expect it will plane up wind, that's only the second time I've ever truly planed upwind in a dinghy ever, unless it's offshore wind and the sea flattens out, which is why it's also going to be important to me to sail it high on one hull and the racks don't dig in to lee side waves.

One quick point, when you say the Vortex main is not 'optimised' for a jib, what should I be doing to that end, they 'mains with jibs' always seem prone to backing which I don't actually like, I appreciate the airflow gets detached and rejoins further down the rear of the main, but other than making the main keep it's shape what more should I be looking for?
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Post Options Post Options   Quote RS400atC Quote  Post ReplyReply Direct Link To This Post Posted: 29 Aug 11 at 6:24pm
I think you will need a lot of masthead buoyancy (or equivalent) to be truly 'inversion proof'.
These days, it seems the majority of my capsizes are some sort of 'gybe-sploosh' experience. If you wipeout at speed in waves, inversion is always a possibility. A wide, buoyant hull probably makes it more likely as the boat will capsize to more than 90 degrees before the mast hits the water. The inertia of the hull means it's unlikely to stop at that point unless you're already on the plate.
Particularly in a decent chop.

I've followed this with interest, not really sure what the success criteria are, but it looks as if it could be fast in flat water. Not so sure about the sea though, but happy to be proven wrong.
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Post Options Post Options   Quote Hector Quote  Post ReplyReply Direct Link To This Post Posted: 29 Aug 11 at 3:29pm
Originally posted by boatshed

Have a look at the first few moments of this video

http://www.youtube.com/watch?v=D-kTmlCxvh8

Stop the movie when the boat is on it's side.  JimC said they are ok to right.   I think this is because they have twin dagger boards.  It is very easy to get from the water to the lower board and then hang on to the upper board.

Your Vtwin has a board in the middle and it will be very hard to get on to.   Unless..... the crafty tunnel under the hull is a useful step !


Woo hoo that was me in the Video. It was unusually sudden - or maybe my reactions are shot and I need a V twin?
Graeme - as you know, I've been following this on facebook, but here are some more thoughts.
  • You'll need to know if things you try have worked, or not, so in the absence of a tune up partner, next time, fit a GPS - better to know relative speeds than speculate.
  • I've always thought the Vortex main (that you're using) is a bit open at the leach - at least on the softish mast used. That looks like it could be a Vortex mast as well and if so, maybe upper stays have stiffened it sideways? Anyway when you do go for a custom rig, consider how you're going to adjust it to allow hardish leach for height in lightwinds and open for higher winds.
  • In stacks of wind, going forward  to grab a new kite sheet is bad news. So get a kite designed to sheet from as far aft as practicable. 
  • Vortex main is not optimised for a jib - improvement available there.
  • It might be very difficult, but it if you take it out in enough wind, it will capsize - simple physics. So, RE Righting it, Vortex is easy to get from turtle, so I dont see why this should be any different. Nonetheless, a righting line and/or flotation may not be a bad idea to start with. And try it in a deliberate lightwind capsize first - not after a  F6 wipeout.
  • Love the idea of inflatable bladder in luff - hoisting and lowering would be an issue but idea has huge potential
  • Dont talk up the speed too much - unless you want a PY of sub 800! Wink
My initial  scepticism is partly removed, but unless it tacks like a dinghy, it may not fulfil one of your wishes  (that you can enjoy close 'tactical' racing. Any comment on how it tacks?  I guess it will need to be compared to the like of an MPS, Contender or Vortex rather than a Laser / RS200.

Well done again for putting your money and time into this.
Keith
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Post Options Post Options   Quote ham4sand Quote  Post ReplyReply Direct Link To This Post Posted: 28 Aug 11 at 10:45pm
thats the problem i had first thought of, what with all the "chasing the jib" we do upwind. I reckon its worth a try though, for the novelty if nothing else
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Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 28 Aug 11 at 5:18pm
Originally posted by ham4sand

thanks for the tip though, what actually goes wrong generally?

Well, I'm not one of the people who's tried it, but I think it would be extremely hard to keep the boat in the groove and driving because you've no reference points.
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Post Options Post Options   Quote ham4sand Quote  Post ReplyReply Direct Link To This Post Posted: 28 Aug 11 at 12:25am
Originally posted by JimC

Worth noting that self trimming jibs have been tried any amount of times on Canoes over the years and always abandoned... If you want to know why go out two handed with your regular crew in the Cherub and try sailing upwind easing the jib with the main on every gust...
 
jim, at the moment we have to on the new boat, the jib is flipping huge, this idea is only intended for a bit of single hand playing, where i can still capsize in relatively small gust even with the main fully dumped, and flat wiring!
its more for my curiosity than anything else! :)
thanks for the tip though, what actually goes wrong generally?
 
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