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Old 12-12-2006, 05:49 PM   #1
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B23 Weight

How much does a fully rigged B23 weigh, excluding fuel?
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Old 12-12-2006, 10:04 PM   #2
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depends if i'm still stuck in it after eating me ginsters
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Old 12-12-2006, 10:45 PM   #3
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Funny aint it , nobody ever seems to know the weights of boats! and most manufacturers tend to shy away from publishing them!!

in the last few days ive been told a P25 weighs 450kgs, a P20 weighs 300kg, does anyone have actual figures or are we all obsessed with ultra light boats. I sometimes wonder wether it ever occurs to people that when a boat is designed it has a destined weight particular to that hull design, no wonder a lot of boat owners have difficulty setting em up!

Just my humble opinion of course!
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Old 12-12-2006, 10:51 PM   #4
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Matt,
Couldnt tell ya weight excluding fuel but mine weigh'd in at just over 820kg after a race at ramsgate this year think from memory i had about 30litres of fuel left in her! Mine is i think one of the heavier if not heaviest B23 running at the mo though! Hope this helps ya!
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Old 12-12-2006, 11:14 PM   #5
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Boat weight is one of those parameters which is usually under estimated, Manufactures will cloud the data in order to safeguard there information. All i will say is that any hull is designed for an optimal weight, If the vessel then exceeds this weight a penalty in terms of drag has to be paid over and above the additional weight.
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Old 12-12-2006, 11:53 PM   #6
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Quote:
Originally Posted by Gav View Post
Funny aint it , nobody ever seems to know the weights of boats! and most manufacturers tend to shy away from publishing them!!

in the last few days ive been told a P25 weighs 450kgs, a P20 weighs 300kg, does anyone have actual figures or are we all obsessed with ultra light boats. I sometimes wonder wether it ever occurs to people that when a boat is designed it has a destined weight particular to that hull design, no wonder a lot of boat owners have difficulty setting em up!

Just my humble opinion of course!
Are these the production weights of standard boats?
Am I right in thinkin some Phantoms are lighter lay-ups thn others?
I've heard of "Featherlight" P21's being thinner than others?
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Old 13-12-2006, 12:07 AM   #7
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I don't think it's quite as cut & dry as that! A major league manfr like formula for example, do. My boat's published weight is 3357kg, and last time we weighed it on the yard crane, it came up at 3.4 tonnes - so spot on. Manfr's like phantom would build to the customers requirements - which was sometimes a lighter and sometimes a heavier boat depending on requirements & budget! So publishing the weight would be largely.

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Funny aint it , nobody ever seems to know the weights of boats! and most manufacturers tend to shy away from publishing them!!
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Old 13-12-2006, 12:19 AM   #8
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A bare B23 hull should be in the region of 512kg
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Old 13-12-2006, 09:11 AM   #9
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My 21's, when built by Mark Pascoe for the Honda race series, weighed 500kg, (+ or - 5 kg's) as a fully bonded boat, with all structures etc, ready for fit out. Once they'd been fitted with sunpad, front and rear seats, side panels, cabin cushion, together with battery, fuel tank, wiring, steering and 130hp motor on setback bracket they weighed 1050kg's.
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Old 13-12-2006, 11:07 AM   #10
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Quote:
Originally Posted by Gav View Post
Funny aint it , ....are we all obsessed with ultra light boats.

Yes, that's because the weight is one third of the three factors that dictate how fast a boat will go.

Also, contrary to popular belief, a light boat runs much nicer, and softer than a heavy one.

The tough bit is making it stay together when the going gets tough, whilst being 'featherlight'.

Ross asked me if I knew what the black Aramat P25 currently for sale would weigh as a bare boat, I said I didn't know for sure, but would guess at about 450-500 Kg's, this estimate is based on knowledge of the other Phantom models, and knowing what similar boats weigh. I also suggested he ask Neil Holmes, as he did some work on that particular boat, so might know.

I assume this conversation is where the figure of 450 kg's you quoted came from.

The thing is, if weight wasn't an issue as far as performance goes, very few boats would ever suffer with crazing, or any form of structural failure, coz it would cost very little in knowledge, or money, to throw in enough material to build an almost unbreakable boat, but that aint the way it is.

Here's the 'Levi' speed formula, though it's only any good if you know the 'constant' figure for a given design/setup.



Levi speed formula

Speed = C x sq-rt hp/weight

Speed(in mph) is equal to the “constant” times the square route of the “power” divided by the “weight”

So, for my boat the speed in “mph” is equal to: 4.8 (C) X the square root of 650 (“bhp” divided by 3 (tonnes))

4.8 X 14.7 = 70.56 mph

speed = 'C' X square route of (power divided weight)

...............................power
Speed = 'C' X SR of -------------
...............................weight

----------------------------------------------------------------------------

The 'constant' figure, can only be translated to another identical design, if the CofG is in the same location, same drive height/type, etc.







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Old 13-12-2006, 12:04 PM   #11
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So if you know the top speed for your boat, and all the parameters you can calculate the new speed if you add more Hp...

determine your constant C = speed/( sqrt hp/tonnage )

Use your newly found constant to calculate the new speed using speed = 'C' X sqrt of (power / weight)


Correct?
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Old 13-12-2006, 12:12 PM   #12
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Even easier, go to www.go-fast.com
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Old 13-12-2006, 03:26 PM   #13
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b23 weight

just out of interest matt, why do you want to know the wieght of a b23
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Old 13-12-2006, 03:52 PM   #14
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mine WEIGHS IN @11500 lbs (sterling)
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Old 13-12-2006, 05:10 PM   #15
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Quote:
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Even easier, go to www.go-fast.com
Yes, the very same formula, though of course it's using pounds for the weight, rather than Kilos, so the 'constant' comes out as a different value.

The main thing is though, that both these formulas show the simple fact, that to double your speed, you need to quadruple the power.
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Old 13-12-2006, 07:30 PM   #16
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The main thing is though, that both these formulas show the simple fact, that to double your speed, you need to quadruple the power.
Boath?

A formula was worked out for me using a very very very complicated method by my boats designer, and the end result for my new power was 4 Mph off the simple rule given above. I thought that was realy very funny.
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Old 13-12-2006, 07:40 PM   #17
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the end result for my new power was 4 Mph off the simple rule given above. I thought that was realy very funny.
Which was closest in actual speed results?
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Old 13-12-2006, 10:24 PM   #18
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Which was closest in actual speed results?
I will tell you in February.
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