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Old 06 September 2010, 04:43   #21
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It'll only do that downhill
Mind if I ask where you found the slope? Only i've been hoping to do some waterskiing and am struggling like mad to find anything with any serious gradient locally
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Old 06 September 2010, 04:45   #22
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Mind if I ask where you found the slope? Only i've been hoping to do some waterskiing and am struggling like mad to find anything with any serious gradient locally
There's a couple of mogul fields around the Bitches.
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Old 06 September 2010, 04:58   #23
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I've a friend with the same boat and a 150 Optimax. He gets it to 47 knotts max I think but is now looking for a Tempest or Vensura prop in the hope of getting that bit closer to 50. Maybe he should just go down tide !
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Old 06 September 2010, 11:47   #24
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Max speed

I've found that flat calm is not the best of conditions for a max speed attempt. Certainly with my tank, which is way off optimum set up, a slight chop is better to 'unstick' the hull and get an extra 2 to 3 knots. Has to be slight mind you, otherwise bottles get well and truly lost.
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Old 07 September 2010, 01:40   #25
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Hi, my friend has given me some further info :
Quote:
quand la mer est un peu clapoteuse (sur mer plate, c'est un peu moins rapide), pas trop de vent, sans l'influence de la marée et seul à bord.
L'hélice était une Enertia 13.75 x 22'.
La plaque anti cavitation est remontée à + 6.5 cm.
Le trim est neutre.
RPM +/- 5500 trs.
Cette hélice est correcte au niveau accroche à l'accelération. Très bonne accroche aussi en virage. Par contre par mer formée, elle a tendance à caviter un peu trop. Et comme je suis un peu perfectionniste, ça ne me suffit pas. C'est par ça que je cherche une autre hélice. Je préfère perdre 2knts en vitesse de pointe mais gagner en accroche. Comme je traine pas mal du côté de Ouessant, je tiens à avoir un bateau qui réagit instantanément...
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Old 07 September 2010, 01:46   #26
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As i'm kind I will translate that for you.

He says that when there is a small chop his top speed is around 47knotts alone onboard. In flat calm conditions he loses some.

His prop is an Enertia 13.75 x 22'

The anti cavitation plate is at +6.5cm (no I will not translate that to inches).

At that speed the trim is neutral (which is a bit surprising to me).

The boat accelerates well, grips well in corners but cavitates a bit in the rough.

As he is in the rough quite a lot, around Ouessant mainly, he needs a prop that grips better, even if he must lose a knott or two.
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Old 07 September 2010, 04:05   #27
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Quote:
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Mind if I ask where you found the slope? Only i've been hoping to do some waterskiing and am struggling like mad to find anything with any serious gradient locally
Looking at the tide tables the other day, I realised that HW springs Jersey is about 11m whereas at the same time in Alderney it is around 6m. By definition there must be a nice downhill slope from Jersey to Alderney which would be a good start for your quest to find a skiing gradient. I suspect theres a fundamental flaw in my premise, but I can't see what.
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Old 07 September 2010, 04:16   #28
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Looking at the tide tables the other day, I realised that HW springs Jersey is about 11m whereas at the same time in Alderney it is around 6m. By definition there must be a nice downhill slope from Jersey to Alderney which would be a good start for your quest to find a skiing gradient. I suspect theres a fundamental flaw in my premise, but I can't see what.
Makes perfect sense to me too Nice nursery slope to get started on
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Old 07 September 2010, 10:48   #29
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And of course we are all forgetting the satnav's ability to just record the highest speed it thinks it sees - I once apparently did 328 knts down the slip at Largs marina - unit was showing something like 50M EPE when it first grabbed a position. The trace showed a very quick dash half a mile up the hill & back again.... Now based on how often it samples position to work out speed.......

All you need is a few seconds of wonky signal at a believable positional error and the extra 40m over the second or so it does the maths for will momentarily up your absolute speed. It's programmed to record a max, that's what it will record.

=> use Average speed for accuracy (having of course remembered to zero / reset it while at WOT)

And of course, the magical 50 knots when unwitytinly read off a display set to MPH is around the 43 knot mark.....
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Old 07 September 2010, 11:15   #30
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You won't see me touching a GPS at WOT !

At St Malo you can have 12m tides. The slope would be even longer then. Maybe you could even hang a right at La Hague
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