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Author Topic: Electrifying an old powerboat  (Read 346 times)

chris1

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Electrifying an old powerboat
« on: May 09, 2021, 06:29:12 am »

Hi gents. My Dad has a very old fibreglass model that he designed himself 40+ years ago, based around 8 Sunny Levi designs. Used to run pretty well with an HP 61 Gold Cup.  He would like to run it but go electric without breaking the bank.  I have two 3S batteries (5000mAh, 60C) so could use those.  The boat is approximately one metre long and has a submerged drive, which he is keen to retain as the drive and rudder are all home made.  The HP 61 produced 2.1hp (roughly 1650 watts) at 16,000rpm according to google.  What motpr and esc would you recommend I look for? Thank you.
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Stuw

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Re: Electrifying an old powerboat
« Reply #1 on: May 09, 2021, 08:48:46 am »

I donít know how much you know about brushless motors (Iím a relative beginner) so donít want to say the obvious, but one factor is the rpm that you want as a maximum I suppose. The ďkVĒ of brushless isnít kilovolts but ďthousands of rpm per voltĒ. So:


1000 kV on 3S (11.1v?) is 1000 x 11.1 = 11,100rpm no load


500 kV on 6S is the same rpm.


This is where my knowledge isnít good,  but the wattage of the motor is also a factor i believe. Prop size will feed back to the motor. What determines the ESC rating I canít  seem to find much definitive info.


For reference Iím planning on putting a 1900kV with 120A marine ESC on 2S in a 1 metre Lesro Javelin but others have got lower kV with higher cell pd. my spec was taken from a Proboat combo as I hadnít found this forum when I was trying to make up my mind. My version isnít cheap at all.

Iíve found this thread that may help:


https://www.modelboatmayhem.co.uk/forum/index.php/topic,58719.0.html

This motor is mentioned in that thread, but I donít know how it will suit you? https://wheelspinmodels.co.uk/i/262234/?gclid=EAIaIQobChMIi9Dgzvm41QIV2KntCh3nngVeEAYYAiABEgLjwPD_BwE


Itís a minefield with lots of different combinations of motor/prop/cell count and ESC.


Sorry probably not much help, but wanted to try.... :-))



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tonyH

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Re: Electrifying an old powerboat
« Reply #2 on: May 09, 2021, 09:44:40 am »

Hi Chris, which Sonny Levi boat is it and what's the size of the prop? The boat shape may have a bearing and the prop size you want to drive certainly will.
Lovely boats as well
Cheers
Tony
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chris1

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Re: Electrifying an old powerboat
« Reply #3 on: May 10, 2021, 05:25:51 am »

Stuw, I'm reasonably familiar and comfortable around brushless motors having flown rc planes for a few years.  But whereas there are some simple guidelines (watts per pound) for different aircraft types, i have found nothing similar for boats.  I'm leaning towards a hobbyking T600 880kv on 5S lipos right now.
Tony, it's not any particular Levi design but a mix-together of 8 of them, with a very deep vee throughout.  I'llget my Dad to measure the prop diameter and seeif there are any markings.  It's got a BA, not metric, shaft with a coupling to bring the driveline parallel to the keel, which I am tempted to rip out and replace by a flex drive.  Will get some pics later
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Stuw

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Re: Electrifying an old powerboat
« Reply #4 on: May 10, 2021, 01:50:25 pm »

Apologies then for my ďexplanationĒ! Oops. There doesnít seem to be much definitive on this for boats as you say. Lots of helpful info on here though, some of it buried away.
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Stuw

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Re: Electrifying an old powerboat
« Reply #5 on: May 18, 2021, 07:55:07 pm »

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