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Author Topic: Fairmile D - brushless?  (Read 977 times)

shadysadie

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Fairmile D - brushless?
« on: December 23, 2016, 02:03:30 PM »

Last October I received invaluable advice from this forum regarding brushless power for my 36" Vosper MTB based on a Kingston Mouldings hull. This was my first foray into the brushless world and I have since been very impressed with the performance of the boat.


A couple of years ago, I built a 5 foot RAF LRRL, again based on the excellent Kingston hull and powered it with 4 x 545 low drain motors as this seemed to be a good idea at the time. Unfortunately, I find that the battery drain from the motors gives very poor endurance on the water and consequently this particular boat has had very little use of late.


Could brushless power be the answer ? Could I


 power just two props and freewheel the other two? If so, should I power the outers or the inners? What size outrunner  would give respectable scale performance - unlike the Vosper I don't require this boat to plane.


Any advice from you good people will be much appreciated.


Regards, David.
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derekwarner

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Re: Fairmile D - brushless?
« Reply #1 on: December 24, 2016, 03:11:14 AM »

Hullo David.......I have no real experience with these craft or and the question between brushed and brushless motors

Having said that, from a simple engineering point there are a few things to consider

1. a 5' long model is of significant size....having 2 propellers [of 4] free wheel will create substantial drag and consume power
2. removing 2 propellers will spoil the visual aspect of the vessel drive

The apparent cost effectiveness in terms of electrical efficiency in going over to brushless motors together with newer format battery technology could be a better option........

Derk
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Derek Warner

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Illawarra Live Steamers Co-op
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www.ils.org.au

canabus

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Re: Fairmile D - brushless?
« Reply #2 on: December 24, 2016, 08:44:59 AM »

Hi Shady

I suggest two 3639-750kv brushless motors ( diameter 36mm, length 21mm, shaft 5mm, 800watt, no loaded on 3S Lipo battery 8325rpm, prop 40-50mm 2 blade.).
ESC 45 amp for each motor via a Y connector.
Personally I buy the Hobbyking car ESC's as these handle 4S batteries and also the sister motor the 3639-1100kv and 3648-1450kv.
The 30,45, 60 and 100 car ESC use the same program card.
Electric fan on the ESC for cooling, so no water cooling required.
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gra2

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Re: Fairmile D - brushless?
« Reply #3 on: December 24, 2016, 08:57:53 AM »

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shadysadie

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Re: Fairmile D - brushless?
« Reply #4 on: December 24, 2016, 01:39:57 PM »

Sincere thanks for the advice folks. Looks like it's going to be the Turnigy 3639's (or very similar) on the centre two props and the outer two freewheeling. I can always remove the outer props when on the water if they give too much drag. Fantastic build and write-up gra2 !


Have a great Christmas, Regards, David.


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