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Old 15 January 2006, 15:04   #1
DJL
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Country: UK - England
Make: Ribcraft 6.5
Length: 6m +
Engine: Suzuki DF175TG
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Engine/Boat Performance Database

There seems to be a continual need for data regarding fuel consumption/speed/props etc - thereís always a thread about it.

What do people think about doing a RIBnet version of the Performance Bulletins on the Yamaha website?

We could have a form on the website to collect data. RIB/Engine make model, weight of boat, prop model/make/dimensions and then fuel/speed info. Fuel flow meters seem to becoming more common so it wouldn't be too difficult for people to scribble down fuel consumption/RPM/speed. The site could then create a little graph etc. If people don't have fuel data then most people seem to know there average fuel consumption which would still give an idea.

I know that there would be no data control but I think it could still be useful. We all seem to wait for magazines to publish group tests, which as seen recently, donít always produce useful results.
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Old 15 January 2006, 15:53   #2
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in principal yes... ...but in practice the criticism of the RI fuel consumption figures is that they were unscientifically obtained and not subject to any sort of intelligent scrutiny. This is potentially the problem with asking everyone to do their own experiments.

The other problem I can see is that if the boat design (rather than say length or weight) has any major effect on the results then there are so many different people here with different boats it will be difficult to interpret the data, so if someone posts data from a 2 stroke 115HP Yamaha on a Parker 630 how will the same engine perform on a Zodiac Huricane 630 or Solent 6.5. In this regard the collective intelligence on ribnet can make educated guesses.

Then presumably you need to consider engines as individual models, as if the same manufacturer brings out a new engine that performs better than a previous similar sized one that won't show up. There are a very large number of boat models and engine models so finding an exact combination that relates to the one you are interested in is tricky.

However - whilst I am sceptical about the ability to obtain enough valid data I think it might be possible to create a reasonably sophisticated empirical model (on the other hand there are theoretical calculations and rules of thumb around) that would collect data from as many rib netters as possible then allow a user to select a chosen size of boat (both weight and length), engine HP, prop, wave size etc to predict the top speed and average fuel consumption.

The alternative - probably much easier and possibly more meaningful option is to just put together a standard layout of information, pop a thread up and ask people for complete the information - and people could search it and if the combination (or something similar) is there - draw their own conclusions.

Anyway - thats my 2p worth!

Neil
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Old 16 January 2006, 03:04   #3
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Good idea

I'd be interetined to know how much a boat engine combination used. Perhaps on the next Ribnet jolly everybody could state boat, engine size and consumption.

Maybe you could go around the Island. I'd certainly be interested to know the difference between, lets say a 200 opti and a 200 etec on 6.5 hulls and that would be relatively easy to do if the owners were willing.

I can sort out a floating refueling station so you go out full and come back and top up. That would give you a realisric consumption figure and providing equal sized engines went at the same speed I think it would be a useful figure.
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Old 16 January 2006, 16:55   #4
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Sounds like a top idea Daniel. Would trust data from quite a few peeps on RN.


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Old 17 January 2006, 14:59   #5
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I think it's a great idea.

Maybe a bit hard to tell exactly whats what as there are so many variables but the more the merrier.

I will be testing my boat as accurately as I can - will also try to calibrate my fuel flow meter using know quantities of fuel etc.

Wonder what sort of difference my transom jack will make???
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Old 17 January 2006, 20:14   #6
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I have a non-RIB:

12' (3.5m) Prestige Conquest 1998
16" (30cm) tubes
wood floor w/inflatable keel
15 HP /2 cycle/Tohatsu
Weight with 2 pax = 650 lbs.(300kg)

Top Speed - 18 MPH (29 KMPH)
Gallons/Hr. (GPH) = 1 (3.8l) at wide open throttle (WOT)

Test conducted on smooth water, no wind
Link to slide show of test boat: www.boating.alfelker.com
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Old 18 January 2006, 10:30   #7
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Quote:
Originally Posted by CaptAl
Gallons/Hr. (GPH) = 1 (3.8l)
3.8Litres...Call that a gallon? Bloody Colonials... worse than the damned Frenchies.....
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Old 18 January 2006, 13:15   #8
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Quote:
Originally Posted by CaptAl
I have a non-RIB:

12' (3.5m) Prestige Conquest 1998
16" (30cm) tubes
wood floor w/inflatable keel
15 HP /2 cycle/Tohatsu
Weight with 2 pax = 650 lbs.(300kg)

Top Speed - 18 MPH (29 KMPH)
Gallons/Hr. (GPH) = 1 (3.8l) at wide open throttle (WOT)

Test conducted on smooth water, no wind
Link to slide show of test boat: www.boating.alfelker.com
Some lovely photos there - nice to see the Yanks sticking to imperial although
how a US gallon comes to be so much smaller has always been a mystery to me!!!
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Old 18 January 2006, 14:14   #9
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Thanks for pointing out my error. I cannot edit my post.

I am conflicted. Posting on UK site from USA about a South African boat. RIBs are not as popular in USA.

I forgot we don't agree on what a gallon equals! Must be more careful in future. (Imperial Gallon = 4.5 liters = 1.2 U.S. gals)

I am hope this encourages more postings of performance data. They don't have to be "perfect".
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Old 10 February 2006, 03:54   #10
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Join Date: Feb 2006
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Xtrim 10m+2x225 4str Johnson

the first is the XTRIM with 2x225 4str johnson...weights about 3.5-4tonnes full load (700ltr fuel+300lt water+4person+laggage) gone up to 47kn in 6.100rpm with 21" props.average speed is 33-34kn in 4300rps and consumption about 2.6lt/m both.

The other is a BOSS 8m passing through the channel of Corinth in Greece weights 3ton with 2x140hp johnson. In 4500rpms about 28-29kn - 2.3-2.4lt/m
nautical mile = 1852m (about).
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