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Old 07 March 2017, 05:41   #31
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Country: UK - England
Town: East Cowes
Make: Solent
Length: 5m +
Engine: Inboard ,diesel 400
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Gas Turbine RIB

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Originally Posted by beamishken View Post
It looks like your going direct to the drive is there a reduction gearbox on the engine to get the rpm to a useable range?
Don't those things do mega rpm's?

Thanks for your interest, yes the engine only develops 400hp at 6000rpm, I used to have it connected to a Bravo2 leg (2:1), so 3000rpm propeller speed!!, worked fine, it uses a gas turbine brake, (see picture, also google "Y2K bike by MTT", same system!), so you can change gear and stall out the power turbine or let it tick over in neutral (2800rpm!) as this engine has a "free power turbine", (like auto car torque converter) it is very forgiving, all very smooth, no clunks and bangs hence the Bravo drive 1:1.65 ratio so higher prop speed, will need a fine pitch prop! (and not a clunky Alpha drive!!)
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Old 07 March 2017, 05:48   #32
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Country: UK - Scotland
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Boat name: charlie girl
Make: reiver 3.8/regal3760
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Engine: 40hp 2st 2x6lp 315
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Ah OK I thought those things were reving in the 10-20,000rpm range I guess some of the big hp tuned v8's will be doing 6k and more and more than 400hp
Are you going bravo 1 drive this time?
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Old 07 March 2017, 08:25   #33
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Country: UK - Scotland
Town: denny
Boat name: breezy
Make: northcraft
Length: 6m +
Engine: honda 150
Join Date: May 2016
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RIBase
Quote:
Originally Posted by Gasturbine59 View Post
Thanks for your interest, yes the engine only develops 400hp at 6000rpm, I used to have it connected to a Bravo2 leg (2:1), so 3000rpm propeller speed!!, worked fine, it uses a gas turbine brake, (see picture, also google "Y2K bike by MTT", same system!), so you can change gear and stall out the power turbine or let it tick over in neutral (2800rpm!) as this engine has a "free power turbine", (like auto car torque converter) it is very forgiving, all very smooth, no clunks and bangs hence the Bravo drive 1:1.65 ratio so higher prop speed, will need a fine pitch prop! (and not a clunky Alpha drive!!)
haha I've got to laugh when you say it only develops 400hp what does the engine burn is it multifuel
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Old 07 March 2017, 09:38   #34
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Country: UK - England
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Make: Solent
Length: 5m +
Engine: Inboard ,diesel 400
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Yes , this is a Bravo 1, with about a 15 inch pitch prop,

The gas turbine runs at 52,000rpm full chat!
the power "free" turbine runs at 33,000rpm that then runs down through the gearbox to become 6000rpm output
fuel is anything!!, but paraffin is prefered , so i'll be using red diesel.
tickover is 8 to 10 gals an hour
full bore is 20 to 30 gals an hour, so fuel tanking is an issue on a small Rib!!


enclosed pic of engine in line with drive shaft via flexi-coupling to bravo
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Old 07 March 2017, 10:28   #35
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Country: UK - England
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what a great project, very envious.. def the right outdrive with that ratio, should be very smooth. 15 pitch prop will be way under i think. 21 poss? or trial an error?
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Old 07 March 2017, 13:07   #36
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Country: UK - England
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Make: Solent
Length: 5m +
Engine: Inboard ,diesel 400
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Gas Turbine RIB

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Originally Posted by matt h View Post
what a great project, very envious.. def the right outdrive with that ratio, should be very smooth. 15 pitch prop will be way under i think. 21 poss? or trial an error?

Yes looks more like 29inch pitch for 100knots!!!!,

OK I know this is not a rib, but just thought these pics of a boat in USA might be of interest?, this boat is 1300hp!!! lycoming t53, ......horny?
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Old 18 March 2017, 03:07   #37
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Hows the project coming along?
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Old 18 March 2017, 09:50   #38
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Hows the project coming along?


Been busy welding up steel crossmember and support braces!Click image for larger version

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Old 18 March 2017, 11:47   #39
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Interesting thread. I used to own that RIB until I sold it to Sam about a month ago who you must have bought it from.

I'm currently working on a 47m motor yacht over in the states, also fitted with a gas turbine (along with two diesels for slow speed manoeuvring). It's an interesting setup - the two diesels running on shafts and props with the turbine coupled to a Kamewa jet drive in the middle. Pushes the boat along at 36 knots (not bad for something that weighs about 500 tonnes).
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Old 18 March 2017, 12:02   #40
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Country: UK - England
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Tim m, lol!, there's me hacking up your old Rib!!!!,
Fine on your super yacht, amazing bit of machinery by your description,
Yes this engine I have was fitted in my old 27ft sun seeker and wasn't appropriate, so I bought the Rib from Sam for a laugh?
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