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08-10-2005, 01:56 AM
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#1
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Large member
Country: England
Location: On the farm
Occupation: General Trouble Causer Salterns Boatyard
Interests: Official smartass
Boat name: Seahorse.org
Boat make: a V24 and a SLOW unstable ICE Bladerunner
Engines: 2x300 promax, 320 Volvo
Cruising area: England/France & Med
Join Date: May 2005
Location: On the farm
Posts: 2,681
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Saltwater vs Freshwater
The density of sea water is about 1.027 g/cm3 at 15 degrees C, whilst the density of freshwater is about 1.000 g/cm3 at 15 degrees C.
The difference in density is about 3%
What difference does this make to the top speed of a boat?
What changes do you think are required for props?
Will the engine rev higher or lower?
Some opinions suggest that the added boyancy in salt water would make the boats 'lighter' and the added density will improve the efficiancy of the propellor, which would reduce the 'slip', increacing performance.
Ideas?
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08-10-2005, 04:23 AM
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#2
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Registered User
Country: England
Location: Great Horwood
Join Date: Mar 2005
Location: Great Horwood
Posts: 2,372
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Most race boats, and even more speedboats do not normally have their times calculated over a measured mile / kilo.
So the many guys that zap down i.e. Southampton Water with their GPS on and record xx mph watch the top speed - not the average!
To make your boat work at full speed – over two ways (one up one down) takes time, analysis, and dedication.
Forget all the B***S*** about density (Salt Vs Fresh), and you missed one there, the altitude of Coniston!
Make sure your engines are at their best; your hull is polished, and take the biggest run up possible before attempting the run.
My very opinionated view is this. “You know you have the right boat, set-up, props, before you go up to the lakes”
I have run 83 mph one way with 90 hp Yamaha - dont ask me about the other way!
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08-10-2005, 06:13 AM
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#3
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Registered User
Country: uk
Location: brighton
Occupation: CABINET MAKER
Interests: SPEED BOATS,MOTO G.P
Boat name: MOTIVATION
Boat make: MARSHAN 21
Engines: AINT GOT ONE!!
Cruising area: sea
Join Date: Sep 2005
Location: brighton
Posts: 1,223
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what about the other way?
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08-10-2005, 01:33 PM
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#4
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Large member
Country: England
Location: On the farm
Occupation: General Trouble Causer Salterns Boatyard
Interests: Official smartass
Boat name: Seahorse.org
Boat make: a V24 and a SLOW unstable ICE Bladerunner
Engines: 2x300 promax, 320 Volvo
Cruising area: England/France & Med
Join Date: May 2005
Location: On the farm
Posts: 2,681
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Quote:
Originally posted by Ciao
My very opinionated view is this. “You know you have the right boat, set-up, props, before you go up to the lakes”
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Thanks for that.
I did notice at Windermere that the boat appeared 'sluggish' to pop nto the plane, like about 2 seconds longer to pop.
Secondly the revs on the engine were at 4700, whilst in the sea, in flat clam, I hit 4850. ( our engines are limited at 5000 )
I will be 'tuning' the prop after tests in freshwater on Monday, so that in fresh water I am maxing at 4950 rpm.
Polishing the hull? I had not thought of that! Would this be just the last 1/3rd of the hull?
What about oil for the gearcase? Can this safely be played with? For example the Bravo Six drive uses ol spray in a dry gearbox to achieve ( claimed ) 50hp more power due to not having fluid in the gearcase. Could you replace the oil with something else? Run lower oil level?
My best time to date ( at Windermere ) was 0.8 miles from the record. I need ( due to the 0.3% rule ) to go 1mph faster than my best time. So my need for speed is minor in actual terms....
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08-10-2005, 01:36 PM
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#5
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Large member
Country: England
Location: On the farm
Occupation: General Trouble Causer Salterns Boatyard
Interests: Official smartass
Boat name: Seahorse.org
Boat make: a V24 and a SLOW unstable ICE Bladerunner
Engines: 2x300 promax, 320 Volvo
Cruising area: England/France & Med
Join Date: May 2005
Location: On the farm
Posts: 2,681
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Conniston is 135 foot over sea level.
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08-10-2005, 02:46 PM
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#6
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Registered User
Join Date: Mar 2004
Posts: 6,891
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I have heard that ATF can give a little extra in the gearbox - but with a very short life for the box.
You could also thin the prop blades further - at the expense of sacrificing life.
Remove the alternator belt for the run? Dunno how much power an alternator draws?
Perhaps go to a 30 weight synthetic race oil in the motor?
Mix a bit of methanol in the fuel?
Take a large dump before the race?
And of course, make sure the hull is perfect.
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08-10-2005, 03:18 PM
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#7
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Registered User
Country: England
Location: Midlands
Occupation: Builder
Boat name: Classified 2
Boat make: Jeanneau 42i
Engines: 50hp janmar
Cruising area: South Coast
Join Date: Mar 2004
Location: Midlands
Posts: 126
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[[B]I have heard that ATF can give a little extra in the gearbox - but with a very short life for the box.
SHORT LIFE WHY?
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08-10-2005, 04:00 PM
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#8
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Registered User
Join Date: Mar 2004
Posts: 6,891
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In the words of Jay Smith, in 2002 (sometimes my memory works):
Quote:
For racing I like the "0" weight Anylsyn ( -5 pts for spelling ) I've even in tight races with inches needed to win used ATF but it is not load bearing to protect gears at all, a gear oil without the sulpher smell won't live long as the sulpher additive in lube oil takes up the space and shock of the meshing teeth ! For laking I like the 100 % Pennzoil Syn at Walmart..... I know you all get tired of me talking about the Pennzoil but I haven't found anything better on the market !
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08-10-2005, 04:03 PM
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#9
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Registered User
Join Date: Mar 2004
Posts: 6,891
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And, in my words, I reckon it's probably got feck all shear strength.
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08-10-2005, 04:29 PM
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#10
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Large member
Country: England
Location: On the farm
Occupation: General Trouble Causer Salterns Boatyard
Interests: Official smartass
Boat name: Seahorse.org
Boat make: a V24 and a SLOW unstable ICE Bladerunner
Engines: 2x300 promax, 320 Volvo
Cruising area: England/France & Med
Join Date: May 2005
Location: On the farm
Posts: 2,681
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Well the gearbox will only be in use for 10 minutes, so I think I will look into that. Also - regarding taking a dump, that does not work for a weight restricted class, due to Ana, I have to add 35 kg of ballast to the boat to make the minimum weight, all nicely packed under her seat!
Methanol in the fuel is illegal ( much like running E3 props to set the record initially, and hope the people at Windermere will not notice ( they did not apparently )) - No, I want to do it within the rules. I know some records are set using dodgy methods, but I dont want to play that way.
I have found the perfect oil for the engine. So that part is done and dusted!
I would like a tad more info on the oil for the gearbox, so I have a clear understanding of what you are saying:
To clarify:
According to the rules.....
951.6 Changes in spare parts are allowed as long as the driver, at races, can show that there is change from the manufacturer (a part number being replaced by another, etc.).
This would allow me to change the 'chip' as the new replacement chip has slightly better response. It is in fact the same part number, but the mapping has changed slightly at the 4500 - 5000 rpm range.
952.2 Sparkplugs may be changed for any other.
952.3 The propellers to be only Volvo Penta E2 duo props, these may be modified. The Volvo Penta E2 markings must be clearly visible on each propeller.
952.12 It is allowed to add rubber hose to the end of the exhausts.
953 - FUEL Fuel regulations according to U.I.M. rule 504.
So - any idea on the 'add rubber hose' to the end of the exhausts?? This seems VERY odd, but it is in the rules as allowed. Why?
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08-10-2005, 04:41 PM
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#11
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Registered User
Country: UK
Location: South West
Boat make: Cyclone/ Cyclone/Rinker
Engines: Merc 2.5 efi's/300XS/5.0 v8
Join Date: Feb 2005
Location: South West
Posts: 592
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Years ago I purchased a Astrs GTE when I asked why the Cavalier SRI produced more BHP from the same engine, I was told that it was because the exhaust was longer, I may be barking up the wrong tree, any body else got any ideas ???????
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08-10-2005, 04:50 PM
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#12
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hello
Join Date: Mar 2004
Posts: 2,739
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Quote:
Originally posted by verytricky
Also - regarding taking a dump, that does not work for a weight restricted class. I have to add 35 kg of ballast to the boat to make the minimum weight
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Dude that is one big dump!!!! How many flushes to get rid of that one?
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08-10-2005, 05:00 PM
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#13
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hello
Join Date: Mar 2004
Posts: 2,739
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Quote:
Originally posted by Wacky Racer
Years ago I purchased a Astrs GTE when I asked why the Cavalier SRI produced more BHP from the same engine, I was told that it was because the exhaust was longer, I may be barking up the wrong tree, any body else got any ideas ???????
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Was the inlet manifold different on the Astra due to less clearance between the motor and the bulkhead?
The 16v motor made the same power in the Astra as it did in the Cavalier!!!
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08-10-2005, 07:48 PM
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#14
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Registered User
Location: Scotland
Interests: Hole maker
Boat make: Humber Ocean Offshore
Engines: KAD 300/DPX
Join Date: Mar 2004
Location: Scotland
Posts: 958
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Quote:
Originally posted by verytricky
Well the gearbox will only be in use for 10 minutes,.....
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How about a dollop of grease. Mix it with a small amount of gear oil so it slops about a bit. Feck all cooling though.
__________________
JW.
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08-10-2005, 08:01 PM
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#15
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Registered User
Location: Scotland
Interests: Hole maker
Boat make: Humber Ocean Offshore
Engines: KAD 300/DPX
Join Date: Mar 2004
Location: Scotland
Posts: 958
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Quote:
Originally posted by verytricky
According to the rules.....
952.3 The propellers to be only Volvo Penta E2 duo props, these may be modified.
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If E3's are better, why don't you tap the E2's with a hammer?
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JW.
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08-10-2005, 11:17 PM
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#16
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Large member
Country: England
Location: On the farm
Occupation: General Trouble Causer Salterns Boatyard
Interests: Official smartass
Boat name: Seahorse.org
Boat make: a V24 and a SLOW unstable ICE Bladerunner
Engines: 2x300 promax, 320 Volvo
Cruising area: England/France & Med
Join Date: May 2005
Location: On the farm
Posts: 2,681
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We are allowed to 'work' the props. So we can set the props to match the water and conditions.....
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09-10-2005, 09:43 AM
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#17
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BananaShark Member
Country: UK
Location: Salcombe South Devon
Occupation: Racer and builder
Interests: Winning races
Boat name: BananaShark
Boat make: BananaShark 34' Race
Engines: Twin Yanmar BY 260's
Join Date: Mar 2004
Location: Salcombe South Devon
Posts: 4,638
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Why not move the 35kg of ballast to the back of the boat - surely you can put the extra weight where you need it?
__________________
Cookee
British Champions! RIB Formula 1 2005
National Speed Record Holder at 90.15 (still)
www.bananasharkracing.com
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09-10-2005, 12:00 PM
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#18
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Large member
Country: England
Location: On the farm
Occupation: General Trouble Causer Salterns Boatyard
Interests: Official smartass
Boat name: Seahorse.org
Boat make: a V24 and a SLOW unstable ICE Bladerunner
Engines: 2x300 promax, 320 Volvo
Cruising area: England/France & Med
Join Date: May 2005
Location: On the farm
Posts: 2,681
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Quote:
Originally posted by Cookee
Why not move the 35kg of ballast to the back of the boat - surely you can put the extra weight where you need it?
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Within the cockpit ot cockpit liner.
( besides, I like the balance left vs right when its under Ana's seat...)
I could get a steal engine mount I suppose.....
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10-10-2005, 09:34 AM
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#19
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Le Cat
Country: France
Location: Paris
Occupation: Computer Sales
Boat name: Le Cat
Boat make: Argo Cat 18
Engines: Mercury 2.4EFI
Cruising area: Paris
Join Date: Mar 2004
Location: Paris
Posts: 753
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Ciao, 83mph with a 90hp !!!
You gotta give me your setup. I won't tell anyone ...
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