New records!

Cookee · 08-11-2007, 02:57 PM

Been up to Coniston to set a record and came back with two!

RIB Sport Professional 90.418 89.873 = 90.15 average

Outboard Immersed Propeller Monohull 92.207 90.932 = 91.57 average

The second one is for any monohull, not just a RIB, and was set with just me in the boat. Engine was a Mercury 2.5 Offshore rated at 280 HP on our race boat which was weighed at 970kg - photos to follow soon - here's one of the rig on the way back yesterday.

By the way the RIB record is basically the old Formula 1 RIB class, but up to 300 HP to allow our European friends race against us.

Cyco · 08-11-2007, 03:49 PM

Well done mate.....bloody good speed.

What length is that hull

Cookee · 08-11-2007, 04:08 PM

Quote:

Originally Posted by Cyco

Well done mate.....bloody good speed.

What length is that hull

7.3 metres - and here is the photo I promised!

The most interesting thing about the experience is that at some points the water was more disturbed than others, and it felt like I was driving over corrugated iron! Quite unnerving at the time!

Cyco · 08-11-2007, 06:00 PM

Nice tow

Cookee · 09-11-2007, 09:08 AM

Quote:

Originally Posted by Cyco

Nice tow

Thanks - here's a photo:

cfun · 09-11-2007, 11:06 AM

Nice going, that's fassssssst

cfun · 09-11-2007, 12:50 PM

Does the speed of 91mph with a 280hp bend any theory of quadrupling power to go X amount faster, as I think Cookee does around 77mph with a 200hp so the figures don't stack up in my way of thinking anybody??? I guess Cookee must of done some calculations to give him a rough idea how fast the boat should go and therefore what kind of pitch and diameter prop to chose for the set up

verytricky · 09-11-2007, 01:24 PM

JF says double the power to go half as fast again...

Soooo..

200 vs 280 = 80hp diff. = 40% more power = 10% more speed = 87mph - so it does not really work.

Where did you get the 77mph from?

Jon Fuller · 09-11-2007, 01:38 PM

The formula says that if cookees boat did 91mph with 280hp, it should do 76mph with 200hp.

The 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 of (power divided weight)

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

================================================== ====

Cookees constant ( 'C' ) works out at 5.3, which is pretty good for a mono.

Cookee · 09-11-2007, 02:24 PM

I did get 76 once going down Southampton water in very flat conditions from the XS200!

I must tell Lorne what a good job he did!

cfun · 09-11-2007, 02:51 PM

I remember reading a few times about the boat doing around the mid 70's with a 200hp so I would assume set up for a speed run as the 280hp was I guessed 77-78mph would be in keeping...going by JF calculation it does appear to be resonably accurate and I conceed I had got it wrong...Thanks for pointing it out correctly...as it is simular in hull form to the bladerunner shows it can work well or at least in mono form

paul tilley · 09-11-2007, 02:52 PM

must be down to the aerodynamics of the tubes not hull design

Cookee · 09-11-2007, 05:34 PM

Without tubes next year?

You can at least tell people your tubes are good for 90mph +!

Jon Fuller · 09-11-2007, 07:40 PM

Quote:

Originally Posted by Cookee

Without tubes next year?

Coming of age??

Matt · 09-11-2007, 09:31 PM

Ya means he's had a wet dream?

Scand · 10-11-2007, 10:17 AM

Quote:

Originally Posted by Cookee

I did get 76 once going down Southampton water in very flat conditions from the XS200!

I must tell Lorne what a good job he did!

Congratulations with the records…
An ignorant question:
Could a banana shark racing boat be used in offshore 3C or is there some rule against tubes?

verytricky · 10-11-2007, 10:43 AM

It can be used in 3C.
In 3C guise the exact boat will do IRO 76mph and would kick ass in the rough!

It is within the weights for 3C and I think this boat actually has a current measurement certificate!

red 5 · 11-11-2007, 09:48 PM

Quote:

Originally Posted by cfun

Does the speed of 91mph with a 280hp bend any theory of quadrupling power to go X amount faster, as I think Cookee does around 77mph with a 200hp so the figures don't stack up in my way of thinking anybody??? I guess Cookee must of done some calculations to give him a rough idea how fast the boat should go and therefore what kind of pitch and diameter prop to chose for the set up

No just pot luck. Just borrow as many props as you can and test em. If your lucky your lucky.

verytricky · 12-11-2007, 12:22 AM

Quote:

Originally Posted by red 5

No just pot luck. Just borrow as many props as you can and test em. If your lucky your lucky.

That sounds like the Marc Lamont school of prop testing...

FIVE sets of E3 props, in all possible iterations makes up 25 runs to test them all over a three week period! By which time you have about four 'good' sets, which you test back to back to determine the 'best' set over a two day period a week later.

red 5 · 12-11-2007, 09:46 AM

Quote:

Originally Posted by verytricky

That sounds like the Marc Lamont school of prop testing...

FIVE sets of E3 props, in all possible iterations makes up 25 runs to test them all over a three week period! By which time you have about four 'good' sets, which you test back to back to determine the 'best' set over a two day period a week later.

All depends who you borrow the props of !!!!!!