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Author Topic: 25 ft clinker boat 1:1 scale  (Read 2294 times)

hemayann

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25 ft clinker boat 1:1 scale
« on: April 17, 2012, 10:25:02 AM »

i have a motor thats marine 39hp, the shaft is 1200mm, what size boat and prop can it handle?
i need a formula? 


does it matter how long the shaft is?
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Tug-Kenny

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Re: hey
« Reply #1 on: April 17, 2012, 10:34:42 AM »



39 horse power should get you across the pond.     %)


ken

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hemayann

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Re: hey
« Reply #2 on: April 17, 2012, 10:41:20 AM »

ha its for a big boat :-))
na i've got a 25 ft clinker boat its got a 12hp yanmar n a 28mm saft n a big prop
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Mad_Mike

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Re: hey
« Reply #3 on: April 17, 2012, 10:43:19 AM »

is that a full scale boat??
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hemayann

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Re: hey
« Reply #4 on: April 17, 2012, 10:45:08 AM »

1 to 1 scale
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Mad_Mike

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Re: hey
« Reply #5 on: April 17, 2012, 10:51:46 AM »

out my depth here  {:-{
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hemayann

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Re: hey
« Reply #6 on: April 17, 2012, 10:52:04 AM »




here she is
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Neil

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Re: hey
« Reply #7 on: April 17, 2012, 11:17:45 AM »

Think you need to join this lot matey   .....They might have a lot more knowledge about this sort of thing than we mere modelling mortals will have about the subject........


http://www.classicboat.co.uk/forums/forumdisplay.php?f=17

neil.
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Mad_Mike

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Re: hey
« Reply #8 on: April 17, 2012, 11:29:00 AM »

I suppose the principle is the same but on a larger scale. When we over prop we get heat and smoke but were on the bankside not sat in the boat smoking with it! %% %%
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essex2visuvesi

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Re: hey
« Reply #9 on: April 17, 2012, 11:43:28 AM »

Be nice to see it with a brushless setup  {-)
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hemayann

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Re: hey
« Reply #10 on: April 17, 2012, 12:18:27 PM »

ha i know there is some brainy people on here
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boatmadman

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Re: hey
« Reply #11 on: April 17, 2012, 01:11:01 PM »

Size of boat and prop will depend on whether you want to go watersking really  {-)
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Neil

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Re: hey
« Reply #12 on: April 17, 2012, 02:28:44 PM »

ha i know there is some brainy people on here


well, a good question like yours brings out the brainiest of us, lol {-) {-) {-)
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John W E

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Re: 25 ft clinker boat 1:1 scale
« Reply #13 on: April 17, 2012, 06:56:17 PM »

yes there are several formulas kicking around, along with several charts to give an approximation of:
: prop size and pitch for a known horsepower and rpm of the motor
: if the boat's weight and size are known & you know what speed you wish to go - there is a formula for that as well
but first of all; you need several known factors
output shaft rpm of the motor, weight of the boat (in this case its going to be a displacement weight) and we need to calculate the block co-efficient

For a semi displacement hull, the block co-efficient should fall between 0.4 - 0.45

For a displacement hull, the block co-efficient should be between 0.45 - 0.55
K = speed in knots
Bhp = brake horse power at the propeller

K x √bhp
displacement in tons


This should give you some idea of the formula which you require

Aye
john
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hemayann

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Re: 25 ft clinker boat 1:1 scale
« Reply #14 on: April 18, 2012, 11:46:14 AM »

^^^^^
told you there is some brainy people here
cheers mate it'll help lots
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