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Old 25 January 2007, 22:31   #21
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have you used both then coders? i have not seen many ribs with Rolls Royce jets. hamilton seem well used in NZ's commercial relm, i have to say i am not an expert on jets so all comments are taken into consideration.

madmat do you run on surface drives?

Jhon i am right in thinking the yellow fin never got off the ground, am i not?

thanks
In fact more and more RIBs etc will use them - the new Offshore Raiding Craft for the UK use 2 jets to give 36kts fully loaded.

http://www.rolls-royce.com/marine/ma...fast_craft.jsp

Have a look at the slides on the page - it shows a US RIB that does 50kts with RR jets. Can't save the piccies out though - looks awesome!!!

Some of the latest advanced warships use KaMeWa/RR jets - the new stealth designs in particular.

They tend to concentrate on the bigger units but they also do them for smaller craft. Hamiltons go up to about 3000kw - the Rolls Royce units go up to 36,000kw!!!
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Old 26 January 2007, 00:07   #22
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Yer they do look nice and that rib seems to go well 50kts, but how much faster than 50 can you get from a jet? speed was not important in the beginning but its becoming more and more appealing. the hard part is to combine both good sea worthiness with the option to do over, or 60kts when the conditions will allow.

i know that jet skis and smaller jet boats get over 50 so why do hamilton say that its hard to get over 50?

do you know a ruff price on the RR jets?
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Old 26 January 2007, 04:37   #23
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hamilton seem well used in NZ's commercial relm, i have to say i am not an expert on jets so all comments are taken into consideration.
My guess is that you'll end up using Hamilton Jets. They seem to be pretty much the industry standard in NZ , and you've got easy access to a lot of local expertise. If you go that route you've got a good chance of getting it right first time, but if you go for a less common surface drive you'll basically be building a prototype.
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Jhon i am right in thinking the yellow fin never got off the ground, am i not?
They're not on the market yet, but I fully expect to see them for sale in the next year or so.

What are you going to use the boat for? Is it just for fun, or for racing?

If, on the other hand, it's for commercial passenger carrying does it actually need to be that fast? For thrill rides 30-40 knots is usually plenty as the perceived speed is so much higher. You may even have trouble insuring for passenger carrying at higher speeds.

Just a thought . . .

John
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Old 26 January 2007, 06:38   #24
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Adam's designing the boat - let him guide on choice of drive as well.

Considering the hull design seperately from the drive package would be a mistake. Depending on the weight, power, stepped, unstepped etc etc will guide the suitability of any given drive.

e.g. If it's an unstepped hull looking to go 50 knots, IMVHO a surface drive would be a difficult choice since they provide little bow lift.

Conversely a jet on a stepped hull might also be a bad choice since the water going into the jet may well be highly aerated losing efficiency
etc etc

What about a pair of the new 350ish hp yammie V8 outboards.
Best of both worlds.
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Old 26 January 2007, 15:47   #25
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John, the first rib is for me and yes i would like it to be able to do around the 60kt mark. i will be using it to get out in the wilderness and extended cruising. the second rib will be for passanger carrying, the current boat runs at around 50. the only speed restriction set in nz is by the insurance you are right and they will not insure unless you stay under 70kts i was happily suprised. i would like to think the passager one will reach 55-60.

madmat
your comment "why dont you let adam decide the drive unit" ofcourse adam will have a huge part to play with the spec of the rib however if you are spending the money and time that i am on the rib its quite nice to talk with friends about what possible drives i can use to propel the rib, plus if i want to be told how my rib looked, worked etc i would not be using adam on the other side of the world i would just get another scorpion. the outboard option is just out of the question on my rib but i could get interested in the passenger rib haveng outboards.

got any pics of your rib? what engines do you run?
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Old 26 January 2007, 16:00   #26
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I think the only sensible way to get that speed is to use outboards - have a look at the big Ring and Revenger boats.
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Old 26 January 2007, 16:21   #27
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I can see your point coders but i cant get petrol where i live only diesel, there has to be away around this and buying a tanker is not it.
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Old 26 January 2007, 16:41   #28
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Shafts with V drives? Engines at the back and shafts run underneath them.
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Old 26 January 2007, 16:56   #29
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Here is a good link for the US RIB running waterjets capable of 50kts

http://www.specwarnet.net/vehicles/NSW11mRIB.htm

I think surface drives must be the way to go for very high speeds though - have a look at the Sunseeker XS2000 - uses Trimax surface drives with 2 speed gearboxes - already proven so not so much messing about!!!
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Old 26 January 2007, 17:06   #30
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have a look at the Sunseeker XS2000 - uses Trimax surface drives with 2 speed gearboxes - already proven so not so much messing about!!!
. . . and it's a great feeling when the gearbox is flicked into second. Lots of grin value!

If you want to talk high perfromance stuff have a look at www.boatmad.com - when they've stopped taking the piss out of you for building a RIB not a speedboat you'll probably find some useful info.

John
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