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[GeoffB]

I’ve been building and flying RC aircraft for around 12 years but have become fed up to the teeth with the weather being very disruptive to the time I can enjoy flying. So I decided to add a bit of variety to my hobby and build a boat that I can enjoy when the weather is too bad for flying.
I’ve started building an aero-naut Princess which up to now is very enjoyable….just fitting the side and bottom panels.
I need to buy the power train but can’t find anywhere on t net that shows how to calculate it. The handbook gives recommendations …..Race 650, actro C5 and Speed 700 motors but I can’t find them on the internet. I’ve found similar boat kits with recommended power trains so I’ll probably try one of those.
Can anyone advise  me to where I can find information on calculating a power train and can anyone advise me what would be a good system for the aero- naut Princess.

[dougal99]

Welcome to the forum. Not sure bad flying weather is necessarily good sailing weather. I prefer low wind and preferably sunny conditions. Here is  a suitable 700 motor https://www.hobbies.co.uk/graupner-brushed-speed-700-race-motor-9-6v-model-boat-electric-motor other providers are available as a quick google shows. You will also nee an electronic speed controller (ESC) and a suitable motor mount. If you want to go the brushless route you will need an appropriate ESC.
HTH

[GeoffB]

Welcome to the forum. Not sure bad flying weather is necessarily good sailing weather. I prefer low wind and preferably sunny conditions. Here is  a suitable 700 motor https://www.hobbies.co.uk/graupner-brushed-speed-700-race-motor-9-6v-model-boat-electric-motor other providers are available as a quick google shows. You will also nee an electronic speed controller (ESC) and a suitable motor mount. If you want to go the brushless route you will need an appropriate ESC.
HTH

Thanks….I feel stupid now. I’ve just done another search and there are loads of them out there 🫣
I do want to go the brushless route and am aware of needing an ESC etc. I was hoping to calculate a suitable power system similar to the system we use with aircraft. Do you know what 700 relates to with the brushed motors ? It may help in deciding on the correct size brushless motor.

[tonyH]

Hi Geoff, there's an old thread on here for, I presume, the same build with brushless. It goes back about 9 years but could be a starting point. So if you do a search under the following topic "Another mahogany Princess" you should find it.There aren't any pics but the data could still apply.Otherwise, look through all the umpteen boats of similar size in the powerboat threads since half of them use brushless.Good Luck

[canabus]

Hi Geoff


A speed race 700 brush motor runs 19000 rpm unloaded on 9.6 volts.
Weight 360 grams.


A brushless Banggood C3542-1250kv (850Watts on 4S(14.8 volts) Lipo battery 18500 rpm unloaded.
Weight 132 grams.
ESC 60 Amp( I use car ESCs with fan on top and have reverse).


Prop 35/40mm 2 blade.


To workout the rpm require divide the voltage by the kv of the motor.


Also the diameter size and the length of the motor will made a difference.


Canabus

[GeoffB]

Hi Geoff, there's an old thread on here for, I presume, the same build with brushless. It goes back about 9 years but could be a starting point. So if you do a search under the following topic "Another mahogany Princess" you should find it.There aren't any pics but the data could still apply.Otherwise, look through all the umpteen boats of similar size in the powerboat threads since half of them use brushless.Good Luck

Thanks…..I’ve found it.
The motor is discontinued but I’ve got all the specs from the HobbyKing website so it gives me a good starting point 👍

[GeoffB]

Hi Geoff


A speed race 700 brush motor runs 19000 rpm unloaded on 9.6 volts.
Weight 360 grams.


A brushless Banggood C3542-1250kv (850Watts on 4S(14.8 volts) Lipo battery 18500 rpm unloaded.
Weight 132 grams.
ESC 60 Amp( I use car ESCs with fan on top and have reverse).


Prop 35/40mm 2 blade.


To workout the rpm require divide the voltage by the kv of the motor.


Also the diameter size and the length of the motor will made a difference.


Canabus


Thanks….I was hoping to use 3cell lipos as I’ve got plenty for flying. Do you think I’ll need 4 cell for the Princess ?