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Author Topic: A bit of advice would be appreciated.  (Read 1769 times)

Bugsy

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A bit of advice would be appreciated.
« on: October 31, 2010, 09:36:26 AM »

My winter project this year is a French Customs Boat from a free set of plans I obtained.
I have decided to build a larger version (1 metre rather than 750mm) and this is where I have a problem.
I have absolutely no idea as to the correct power/drive system to use.

The original plans (750mm) show two MFA Stingray 500 motors driving 32mm x12 props.

I obviously need to go up in size for the bigger boat and would appreciate advice on the following,

1. Would two 700 motors be OK.

2. The prop, on my 'blown-up' plan comes out at 45mm, does this sound about right.

3. Would I be right in thinking that M5 propshaft would be the correct size for this unit.

Do I need one or two controllers for this setup.

Sorry to be a bit of a dummy on this but I can't afford to make any mistakes in my purchasing.

Thanks.
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Shipmate60

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Re: A bit of advice would be appreciated.
« Reply #1 on: October 31, 2010, 07:27:00 PM »

Bugsy,
Most of the information you are asking for will be on the larger plan or just scale up the original size.
What speed do you want her to be, fast, sedate or very fast?
How many Speed Controllers is up to you. 2 are obviously more expensive but 2 give better control.
Firstly lets get the motors sorted out then go for the controller(s).

Bob
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Bugsy

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Re: A bit of advice would be appreciated.
« Reply #2 on: October 31, 2010, 07:51:02 PM »

Hi Bob,
I don't have a larger plan, I simply enlarged (135%) the original. That shows '500' motors which, I'm guessing, will be too small?

I want the boat to plane and run scale speeds.

I would add that I have built and flown IC powered planes, I currently sail a One Metre  yacht but I have never built an electric powered model. I've tried reading up on a lot of posts but its a bit like a 'black art' to me  {:-{

thanks.
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triumphjon

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Re: A bit of advice would be appreciated.
« Reply #3 on: October 31, 2010, 08:19:53 PM »

personally id fit some 4m propshafts as there are a greater range of plastic propellers to fit onto them ,
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Bugsy

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Re: A bit of advice would be appreciated.
« Reply #4 on: November 04, 2010, 09:16:01 AM »

Thanks for that.

Am I thinking along the right lines with a couple of these motors?

http://www.giantcod.co.uk/xyh3542-1000kv-brushless-outrunner-p-402744.html

Or am I out of my tree, as usual  O0
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ZZ56

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Re: A bit of advice would be appreciated.
« Reply #5 on: November 04, 2010, 08:03:45 PM »

Original props are 32mm, increased 135% would be around 40mm or 45mm (commercially made props go up in 5mm intervals).

45mm props have a 7800 RPM maximum effective speed according to the manufacturer. 

Therefore, yes, those motors would be okay up to a 7.2 volt system.  45mm props do not require much torque even at full RPM, but it would be nice if these brushless motors came with a torque rating for comparison purposes. 
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