Any knowelegeable person help please

[Burty]

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

 

[Gav]

try this it was on another thread you were posting on a few months ago!

http://www.rbbi.com/folders/prop/propcalc.htm

 

[Hydrostream]

Speed

Presuming 1.87 gears and 10% slip
22" = 84.31
23" = 87.98

Sorry calc don't do 22.5!

Nice speed too!!!

 

[Gav]

22.5" = 86.14mph

thats movin':wink:

 

[Tony Davis]

You lot need new calculators! If it's 1.87:1 with 10% slip, then your getting 82.037 mph

 

[Captain Chaos]

is 10% slip realistic? I used that to calculate some speeds for my 21.........and i was getting all happy with 15%

 

[Hydrostream]

is 10% slip realistic? I used that to calculate some speeds for my 21.........and i was getting all happy with 15%

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%

 

[Hydrostream]

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

 

[TheOrs]

...up the river Avon from Avonmouth to Bristol docks.

<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.

 

[JamesM]

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!!!

 

[Burty]

Re: 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

Link don't work hydro dude, says page not found

 

[Burty]

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!!!

6 knotts i have since been told by the 2 sail boats we upset with our wakes

 

[Burty]

Re: Re: Any knowelegeable person help please

<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.

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

 

[Cyco]

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.

 

[Cyco]

And another pic

 

[Jon Fuller]

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

 

[Captain Chaos]

you wanna do another one?

glutton for punishment!

 

[Jon Fuller]

Well I quite enjoyed it!

 

[Captain Chaos]

just dont go mentioning that @ the hunton stand

 

[Jon Fuller]

just dont go mentioning that @ the hunton stand