7mt RIB, 125hp, 65mph!! Possible??

[DaCostaGreene]

I recently sold some decking and lights to a RIB manufacturer. The boat looks stunning, deep V and staggered steps along the hull, the deck obviously looks great, the consoles and the seats and the tubes, the whole thing is georgeous.

The builder claims that the boat will top 65mph on a single 125hp engine, on a 7mt hull. Is this possible?? IMHO, having seen the RIB, I reckon its possible - the boat weighs less than 800kg and cost very little compared to the rest of the market.

What do you think??

 

[neale]

I have driven a number of rib around this size and would say probably not. I guess more like 40 knots (46mph) ish at best, maybe less.

 

[jhr]

I don't think you will get a coherent answer out of this lot. Responses will be divided between:

<ul type="square"> They'd be better off getting a diesel

It won't perform properly unless it has/hasn't got a bow thruster

It might do it on the East Coast/West Country/Severn Estuary/Mediterranean but you won't manage it in the Solent

Not if it's weighed down by all that strangely realistic wood substitute

No - and it's all Tony Blair's fault. [/list]

Or you could try asking on FibNet. Hope this helps.

 

[DERF]

Hmmmm... don't think so not with a 125hp.

 

[Nick_H]

The stepped hull makes a hell of a difference. Beneteau make a walk around cuddy boat with a stepped hull and air injected at the front of the hull, and they claim over 50 knots on a single outboard

 

[Channel Ribs]

Possible, but a very fine art.

We were experimenting at the weekend with power to weight trade-offs, for some large inflatables we are putting together with consoles etc.

If the hull is well engineered and the weight kept down and well balanced, it should be possible. The problem then becomes handling and sea keeping, as everything is a trade off.

 

[AJW]

Nah, Dont think so. My 7.5m/200hp would top out at 50kts. Driven a 6m with 150 XR2 and IIRC that topped out at 55ish. Anyway, not sure that anyone makes a 125hp O/B these days? Mebbe they mean 225?! /forums/images/graemlins/wink.gif

 

[Magnum]

Nope. 40-45 knots tops.

 

[mjf]

Re: 7mt RIB, 125hp, 65mph!! Possible??

He might be right as its light - the stepped hull will make it 'fly' but at the cost of stability. I guess its very narrow compared to other 6.5-7.0m RIBs too?


The extra wt of the tekdek is a huge draw-back so maybe 40mph after all.

 

[victoraspey]

I reckon you need to lean over the front and blow bubbles under the hull. I will gladly watch to see if it is possible.

 

[Dave_Snelson]

I'm going with the - "no, and its all Tony Blairs fault"

Thats because it is! /forums/images/graemlins/grin.gif

 

[Dave_Snelson]

I don't think so - even with a stepped hull. Stepped hulls do make a difference but not that much! /forums/images/graemlins/shocked.gif

You basically have a 22 foot boat and 125HP, and it doesn't stack up. My experiences with the wonderful Searay 19BR (19 foot with a great hull and 260HP) give about 60 mph with just one up and ducked down behind the closed screen. The engine was running at 4600rpm (and you should have heard it) and the trim was as high as I dared, so I can safely conclude that the boat was flat out!

So, a nearer estimate for yer man's RIB would be in the region of 40-45kts (46-51mph). And lets be honest here, anything over 40mph on water is actually fast - even these days!

 

[BrendanS]

My 21' with stepped hull has more weight than a rib, but still only does 44knts (50 mph) with 200hp. I suspect that 65mph with only 125hp would require a very very light build.

 

[Jonmendez]

We run a 7m Ribcraft with 175hp, not a light build but a great hull, just touches 40knots so highly unlikely!

 

[DaCostaGreene]

I've been invited to go out on it in the next couple of weeks, i'll keep you posted. for everyone's info its being launched at RIBex, not on the water though on the dry standing.

Yes, it is a narrow build but there is room to walk around the console and the fixtures and fittings are very well made and very comfy.

I reckon the markets in for a big surprise with this one!!!

 

[MapisM]

A key point is the weight, what does "less than 800kg" mean exactly?
Performance hulls can be lighter than that, for such size.
And they can achieve 65mph, with 125hp, no doubt.
But personally, I wouldn't use them in anything else but dead calm lakes.

 

[tcm]

hm, 65 mph is short of 57 knots?

i rekcon just about poss on lake-flat water. We are 175 hp in 3.6 rib but porpoise above 30-35 knots really, max so far under 50knts.

 

[duncan]

previous boat was 800 kg, 21ft but 175hp - 48 knots.

Not a stepped hull of course.

At these weights dont forget the weight of the driver and or fuel - ie no fuel no driver (well a mere waif at 81/2 stone say) and, as already suggested a fair bit under 800kg and it may well manage it (down wind down hill and with reading the boats pitot driven speedo (overeading by 10%)