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twin props

Old 02-26-2009, 11:10 PM
  #1  
maxs
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Default twin props

hi
i need to know if i am going to use twin counter props a left and a right ,i am using three bladed dumas brass do i have them turning in on each other or the other way,some one told me to put the left on the right and the right on the left if i was counter rotation them in on each other ,that dont sound right? thanks maxs
Old 02-27-2009, 09:17 AM
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Ron Olson
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Default RE: twin props

Actually it does.
The scale boaters brought this up some time ago. The port one should be turning clockwise and the starboard side counter-clockwise.
Old 02-28-2009, 09:48 AM
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Default RE: twin props

hi

so then i put the left on the right and the right on the left ? as for prop size its a cabin cruiser 44" by 16- 2 -700 graupuaers i got two dumas three blade 2" that i am going to use ? hey what do you think of this water pick ups at the bottom of the page at #224 post
http://forums.radiocontrolzone.com/s...9&pp=25&page=9
Old 02-28-2009, 12:36 PM
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Default RE: twin props

It really depends on the type of boat.
Tugs, and push boats will mount them as Ron describes.
Military ships are usually clockwise on the right(starboard) side.

Here's an old diagram from a Chris Craft owners Manual that
shows the propeller rotation for mounting postions. [8D]
.
.
.
Propellers from the Europe come labled backward from
how prop rotation is viewed in the US, they label the
counterclockwise rotation as right handed. Hences some
of the confusion for putting the left hand prop on the right shaft.
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Old 03-01-2009, 06:58 AM
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pompebled
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Default RE: twin props

ORIGINAL: maxs
hi
hey what do you think of this water pick ups at the bottom of the page at #224 post
http://forums.radiocontrolzone.com/s...9&pp=25&page=9
Hi Maxs,

I think it's rather elaborate, I don't like the fact this builder moved the position of the shaft to accomodate the ease of construction, as it will increase the strain on the servo('s).

For your cabin cruiser, a pair of angled and/or slanted pipes sitting in the propstream should work just as well, maybe even better, as they don't turn away partly when the rudder moves.

I've added a few sketches.
The slanted tube is for fast electrics, a cabin cruiser will most likely not run full throttle all the time...
If you make the exit under water in the same way, but make the tube facing towards the transom, it will create suction and assure flow through the cooling system even at low speeds.

Regards, Jan.
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Old 03-01-2009, 11:05 AM
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maxs
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Default RE: twin props

thanks guys
i am going to do #3 picture from jan
Old 03-01-2009, 01:43 PM
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Default RE: twin props


ORIGINAL: maxs

thanks guys
i am going to do #3 picture from jan
That's the one that requires some 15mph hull speed to get the flow going and will only work in combination with a sucktion outlet when running at lower speeds.
When you putter around without making a fast pass, the flow will most likely not get going at all, due to air in the system.
Inlet #1 and 2 may have slightly more drag, but will provide cooling water at low speed aswel.

Regards, Jan.
Old 03-01-2009, 02:10 PM
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Ron Olson
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Default RE: twin props

For low-speed running it shouldn't need much if any water-cooling anyway.
Old 03-02-2009, 01:29 AM
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maxs
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Default RE: twin props

hi
thanks, ok i took out most of the angle very little forward now ,the prop wash should pump water thought the system, i like water coolers on the engines and the esc i am using 2- 700 garuapuer 12 volt 7 amp gel cell mdc sc-480 water cooled and progamable these are great but the guy take forever to get it to you
http://www.modelcontrol.com/sc480.htm

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