Ribcraft 5.85 max design speed. - Page 2

Razorbill RIBs · 06 September 2010, 08:43

Quote:

Originally Posted by martini

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

Downhilldai · 06 September 2010, 08:45

Quote:

Originally Posted by Dan Worth

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.

Pablo · 06 September 2010, 08:58

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 !

Ian M · 06 September 2010, 15:47

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.

Pablo · 07 September 2010, 05:40

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...

Pablo · 07 September 2010, 05:46

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.

Erin · 07 September 2010, 08:05

Quote:

Originally Posted by Dan Worth

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.

Razorbill RIBs · 07 September 2010, 08:16

Quote:

Originally Posted by Erin

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

9D280 · 07 September 2010, 14:48

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.....

Pablo · 07 September 2010, 15:15

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

GordyP · 07 September 2010, 15:24

The elusive 50kts, have had just over 49kts but thats a white nuckle ride on the edge of a violent chine walk on glass like water, I don't think i would be that comfortable even trying it with anyone else in the boat. As a few others have said its more the comfortable cruising speed thats important.

GJ0KYZ · 07 September 2010, 17:17

I've can get 46kts with a 4-bladed Cyclone and 47kts with a 3-bladed Rebel. The ride with the Cyclone is rock steady but a bit twitchy with the other prop. By the way, why does this advert keep popping up on this thread? -

"Dating Asian Girls
Soft & Pretty Asian Girls Seek Men for Dating, Love & More Join Free!"

willk · 07 September 2010, 18:27

Quote:

Originally Posted by GJ0KYZ

By the way, why does this advert keep popping up on this thread? -

"Dating Asian Girls
Soft & Pretty Asian Girls Seek Men for Dating, Love & More Join Free!"

You might want to clear your cookies

Mrs willk uses my PC and asked me, rather plaintively, "Why do Amazon and Ebay and Argos keep showing me yellow pressure washers and boaty things?"

Dunno Mrs willk I say, and I hide me credit card bills

deeyup · 07 September 2010, 18:29

I see 54 knots most times I go out on my work boat (that's if the trim is working correctly for a change)
It's a little larger than the op's boat, but still a ribcraft. A 9.0m with twin df300's!!
It's rock solid at those speeds, but it does weigh over 3 tonnes.

I have a friend with a 5.85 and 150 mercury. Fantastic boat. Like an overgrown PWC.

GJ0KYZ · 07 September 2010, 18:50

Quote:

Originally Posted by willk

You might want to clear your cookies

Mrs willk uses my PC and asked me, rather plaintively, "Why do Amazon and Ebay and Argos keep showing me yellow pressure washers and boaty things?"

Dunno Mrs willk I say, and I hide me credit card bills

Right, I just assumed that because of my browsing history (bragging about speed, MSM etc) that the dating site targeted me as someone in need of a "soft and pretty asian girl". It reminds me of an old copy of the Karma Sutra that I read once and which had an advert in the back telling you how to become a chartered accountant.

willk · 07 September 2010, 20:01

Quote:

Originally Posted by GJ0KYZ

It reminds me of an old copy of the Karma Sutra that I read once and which had an advert in the back telling you how to become a chartered accountant.

Figures, they're a dab hand at the auld double entries...

JABS · 07 September 2010, 20:24

I assume you don't want to try the other prop?

BogMonster · 07 September 2010, 21:17

Quote:

Originally Posted by willk

Figures, they're a dab hand at the auld double entries...

willk · 07 September 2010, 21:47

Quote:

Originally Posted by BogMonster

Yeah, if FIBnet gave triple scores, I'd be "in" with that one

ppenman · 15 September 2010, 11:28

I have had 46 kn from my 585 with a new (12hrs old) 150 Suzuki, 200 kg of passengers and 40 gal of fuel. The engine was sitting at 6000rpm which implies that the propping is pretty spot on. When Ribcraft delivered the boat to me they mentioned that it had done 46kn during the sea trial so i reckon that's about it for this combo. Gets a bit flighty at this this speed and i wouldn't want to travel far in it at these speeds. (35kn is much nicer)