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propellers

why cant you use 2 of the same.........

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Jake Knight14/06/2008 19:12:00
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90 forum posts
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just wondering why cant you use 2 of the same propellers on a twin screw boat

will it make the boat go around in circles?

Paul T14/06/2008 21:03:00
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Hi Jake

There is a long and a short answer to this question.

The long answer involves complex maths, hydrodynamics, thrust vectors, prop wash vortex and the coriolis effect.

The short answer is .......Yes. your boat will go around in large arcs 

Paul

Jake Knight15/06/2008 14:24:00
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90 forum posts
24 photos
thanks paul i guess i should stay away from the long answer
Manxman15/06/2008 21:10:00
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No Jake - ask for the long answer !

I want yo see how long it takes Paul to write ...

Paul T16/06/2008 09:30:00
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Bug***r off Ken

I've got enough on my plate redesigning the TID to include free flooding, sometimes I just write to much and get myself into all sorts of bother. 

Building the TID is going to take weeks and I am still refitting the Trent in readiness for the Birchwood show. So writing 20 pages of technical blurb that no one will read is just out of the question.

But thanks for thinking of me.

Paul

Bob Abell16/06/2008 10:03:00
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Hello Paul and Ken

As a matter of  fact......................My old Broom launch has got the same hand of props on and it has no noticeble tendency to go off course!..............and Ducky the new owner, assumed they were handed and had them contra-rotating!..........No wonder his wife was disappointed with it`s handling!

I`d like to know how you`re gonna fill 20 pages on the subject?

Bob

Jake Knight16/06/2008 11:10:00
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90 forum posts
24 photos

hi bob does your old broom launch go fast ?

Bob Abell16/06/2008 11:23:00
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9337 forum posts
2985 photos

Hello Jake

It has two 540 motors....no water cooling and runs at just a little over scale speed.

There is a photo of it in my "Other boats" gallery

Regards ...Bob

Paul T16/06/2008 13:50:00
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7335 forum posts
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2 articles

Hi Bob

You have got me again... of course I realise that 20 pages is a gross understatement on the amount of math involved but I didn't think that anyone would pick me up on it, we both know that Hasslberger's equations will fill at least 9 pages and as for Einstein's contribution!!!!

Still it is nice to know that a fellow mathematician is also a first class model builder.

Paul

Jake Knight16/06/2008 17:11:00
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90 forum posts
24 photos

ok thanks bob

i already have 2 same handed props so il give them a go

if not il just have to buy some

thanks again guys

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