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16-01-2005, 01:22 PM
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#1
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Registered User
Country: UK
Location: Weston Super Mare
Occupation: Electrical Engineer
Join Date: Mar 2004
Location: Weston Super Mare
Posts: 6,351
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Any knowelegeable person help please
dudes, me and Cyco been out in our boats today, we went up the river Avon from Avonmouth to Bristol docks. I jacked my engine up right to the top which is about an inch above the transom and trimmed out. i turned a 22.5" Et prop to 8000 rpm my cheapo speedo was round past 80mph and on the stop just wondering if anyone could calculate a rough actual speed. cheers
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16-01-2005, 03:45 PM
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#3
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Registered User
Country: Ireland
Location: Dublin
Occupation: Boatbuilder
Boat make: Hydrostream V-king, 650SS OCR ,Ring 21, Ring 18, Phantom 18.
Engines: 300Hp Mercury 2.4, 130 Yamaha, Bridgeport EFI, XR6, Merc 200.
Cruising area: Malahide, Dublin
Join Date: May 2004
Location: Dublin
Posts: 1,803
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Speed
Presuming 1.87 gears and 10% slip
22" = 84.31
23" = 87.98
Sorry calc don't do 22.5!
Nice speed too!!!
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16-01-2005, 04:26 PM
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#4
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Registered User
Join Date: Mar 2004
Posts: 5,724
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22.5" = 86.14mph
 thats movin':wink:
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16-01-2005, 05:01 PM
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#5
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Registered User
Country: Job Centre
Location: In a box
Occupation: Chaos's gofer
Interests: Skiving
Boat make: Spectre 30
Engines: 2 x Promax 225
Cruising area: In the bath
Join Date: Mar 2004
Location: In a box
Posts: 5,201
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You lot need new calculators! If it's 1.87:1 with 10% slip, then your getting 82.037 mph
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16-01-2005, 05:28 PM
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#6
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The Doc
Join Date: Mar 2004
Posts: 8,291
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is 10% slip realistic? I used that to calculate some speeds for my 21.........and i was getting all happy with 15%
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16-01-2005, 06:36 PM
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#7
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Registered User
Country: Ireland
Location: Dublin
Occupation: Boatbuilder
Boat make: Hydrostream V-king, 650SS OCR ,Ring 21, Ring 18, Phantom 18.
Engines: 300Hp Mercury 2.4, 130 Yamaha, Bridgeport EFI, XR6, Merc 200.
Cruising area: Malahide, Dublin
Join Date: May 2004
Location: Dublin
Posts: 1,803
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Quote:
Originally posted by Captain Chaos
is 10% slip realistic? I used that to calculate some speeds for my 21.........and i was getting all happy with 15%
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Thats prety good for a deep vee. Slip is different with each boat even two similar boats could have dif. slip!
Slip is a good thing, without it your not going anywhere slip = thrust.
Diferent amounts of thrust are needed to push diferent weight boats.
I think the average slip for my boat is about 9%
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16-01-2005, 06:38 PM
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#8
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Registered User
Country: Ireland
Location: Dublin
Occupation: Boatbuilder
Boat make: Hydrostream V-king, 650SS OCR ,Ring 21, Ring 18, Phantom 18.
Engines: 300Hp Mercury 2.4, 130 Yamaha, Bridgeport EFI, XR6, Merc 200.
Cruising area: Malahide, Dublin
Join Date: May 2004
Location: Dublin
Posts: 1,803
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prop calc
Heres the program I use, you can download it and run it from your computer. No need to go online 
http://www.hydrostream.org/Prop.htm
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16-01-2005, 06:39 PM
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#9
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Registered User
Country: England
Location: Plymouth
Boat make: Fletcher Arrowflyte
Engines: Mercury 75
Join Date: Nov 2004
Location: Plymouth
Posts: 402
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Re: Any knowelegeable person help please
Quote:
Originally posted by Burty
...up the river Avon from Avonmouth to Bristol docks.
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<b> 80+</B>
You must've been going about twice as fast as the cars on the Portway! Bet you had to slow down for Horseshoe bend though.
Every time I drive on that road, I think about how great it would be to go flat out down that river.
Respect.
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16-01-2005, 08:54 PM
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#10
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hello
Join Date: Mar 2004
Posts: 2,739
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Just out of interest what is the speed limit on the River Avon? 
I would imagine Burty would have good drive (low slip) because he has 8" of setback!!!
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16-01-2005, 11:42 PM
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#11
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Registered User
Country: UK
Location: Weston Super Mare
Occupation: Electrical Engineer
Join Date: Mar 2004
Location: Weston Super Mare
Posts: 6,351
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Re: prop calc
Link don't work hydro dude, says page not found 
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16-01-2005, 11:44 PM
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#12
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Registered User
Country: UK
Location: Weston Super Mare
Occupation: Electrical Engineer
Join Date: Mar 2004
Location: Weston Super Mare
Posts: 6,351
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Quote:
Originally posted by Johnny Boat Dude
Just out of interest what is the speed limit on the River Avon?
I would imagine Burty would have good drive (low slip) because he has 8" of setback!!!
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6 knotts i have since been told by the 2 sail boats we upset with our wakes
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16-01-2005, 11:57 PM
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#13
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Registered User
Country: UK
Location: Weston Super Mare
Occupation: Electrical Engineer
Join Date: Mar 2004
Location: Weston Super Mare
Posts: 6,351
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Re: Re: Any knowelegeable person help please
Quote:
Originally posted by TheOrs
<b>80+</B>
You must've been going about twice as fast as the cars on the Portway! Bet you had to slow down for Horseshoe bend though.
Every time I drive on that road, I think about how great it would be to go flat out down that river.
Respect.
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had too slow down for every bend cus my steering locks up when i got my engine really high at that speed
plus had to keep avoiding cycos wake
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17-01-2005, 09:59 AM
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#14
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Registered User
Country: England
Location: South West
Occupation: Development engineer
Interests: Fast boats
Boat name: Xtreme
Boat make: Bernico 21
Engines: Mercury F1, 300 Drag, XR2 "Fingerported"
Cruising area: South West
Join Date: Mar 2004
Location: South West
Posts: 1,043
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Wanted to do that for years.
Every time I drive along the portway or Clifton Suspension bridge I think about it.
What a buzz.....dead calm water for miles, Burty and I flat out all the way.
We didn't hang around long at the cumberland basin tho.
Lots of people and road workers looking from the Portway must of sounded amazing echoing around Clifton george.
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17-01-2005, 10:00 AM
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#15
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Registered User
Country: England
Location: South West
Occupation: Development engineer
Interests: Fast boats
Boat name: Xtreme
Boat make: Bernico 21
Engines: Mercury F1, 300 Drag, XR2 "Fingerported"
Cruising area: South West
Join Date: Mar 2004
Location: South West
Posts: 1,043
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And another pic
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17-01-2005, 10:53 AM
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#16
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numbskull
Country: United Kingdom
Location: South
Occupation: none
Interests: none
Boat name: Leviathan
Boat make: Phantom 28
Cruising area: South Coast
Join Date: Mar 2004
Location: South
Posts: 15,959
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Looking at those pics, I keep getting the soundtrack from the boat chase scene in 'Live and Let Die' going round & round in my head
I bet that was great fun!
Next time you need someone on those vantage points with video camera in hand! ....excellent footage for the next video night 
__________________
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"I Agree with everything you say really!" - John Cooke to Jon Fuller - 26-01-2013
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17-01-2005, 11:22 AM
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#17
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The Doc
Join Date: Mar 2004
Posts: 8,291
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you wanna do another one?
glutton for punishment!
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17-01-2005, 11:31 AM
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#18
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numbskull
Country: United Kingdom
Location: South
Occupation: none
Interests: none
Boat name: Leviathan
Boat make: Phantom 28
Cruising area: South Coast
Join Date: Mar 2004
Location: South
Posts: 15,959
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Well I quite enjoyed it!
__________________
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"I Agree with everything you say really!" - John Cooke to Jon Fuller - 26-01-2013
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17-01-2005, 11:38 AM
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#19
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The Doc
Join Date: Mar 2004
Posts: 8,291
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just dont go mentioning that @ the hunton stand
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17-01-2005, 11:47 AM
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#20
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numbskull
Country: United Kingdom
Location: South
Occupation: none
Interests: none
Boat name: Leviathan
Boat make: Phantom 28
Cruising area: South Coast
Join Date: Mar 2004
Location: South
Posts: 15,959
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