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Packrafting with thruster

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Packrafting with thruster

Old 12-26-2020, 12:27 PM
  #1  
Packrafter
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Default Packrafting with thruster

Hi!

I am considering to try to run my packraft using a thruster. The plan is to have a thruster attached to a rod that is loosely attached on the side of the packraft. That way I can both turn the rod and thereby the propeller, and I can easily pull it out of the water. If this works, I may also try to change the device later on, and control it with some rc unit.

I consider these components:
Thruster: From aliexpress: DIY ROV Submarine 5KG Underwater Thruster 12V 460KV Waterproof Brushless Motor with CW CCW Propeller 40A ESC for RC Fishing Boat ("CW thruster")
ESC: From aliexpress: ZMR 12A/20A/30A/40A/50A/60A/80A Bidirectional Brushless ESC for Remote Control Car Pneumatic Underwater Propeller ("80A")
Throttle: From aliexpress: Electric two-wheeled tricycle electric bicycle universal type conventional turning throttle inner diameter 22mm free shipping ("Black big throttle")
Battery: From biltema no: ("BATTERI SMF 12V 20AH Art.nr. 80-2201") (This is a 12V leisure battery).

Will this work? I worry that one of the components, especally the battery or the ESC, can be overheated. Can some component start to burn, or explode?

Grateful for all answers!
Old 12-27-2020, 02:02 AM
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mfr02
 
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Without links to the actual items, a search from here just gives a pile of google guesses. In all probability none of them are your items, so finding specifications for them isn't going to happen.

Your chosen battery (12AH/12v SLA) is a big heavy lump of a thing that has, by todays standards, poor energy density. This will give short run times, and if worked hard, probably a short battery life. If not subjected to heavy discharge or fast recharge, they can have a long service life.

The description sounds like a powered paddle or hand held long shaft outboard - you will probably get more control and power out of a manual paddle. A guy I used to see at my lake several years ago was a keen operator of his inflatable kayak, possibly an earlier name for a "packraft". When he wanted an easy run downwind he opened a small umbrella.
Old 12-27-2020, 07:01 AM
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I am not allowed to put in links, until I have 10 posts... But these should still work, if you google it or if you put in the html rearmost in the three first:
Thruster: aliexpress.com/item/4000384252281. ("CW thruster")
ESC: aliexpress.com/item/4000235650720 ("80A")
Throttle: aliexpress.com/item/32978751144 ("Black big throttle")
Battery: biltema.no/bil---mc/bildeler/elsystem/bilbatterier/vedlikeholdsfrie-batterier ("BATTERI SMF 12V 20AH Art.nr. 80-2201")

The battery is a so called "leisure battery" (not a starter battery), used for example for electric outboard motors. The particular battery I have in mind, does not have a lot of energy, but is not as heavy as other batteries that is more dedicated for outboard motors (20Ah and 6,8 kg, vs for example 100Ah and 20,0 kg). I will of course appreciate suggestions of more appropriate batteries.

Yes, it will be like a hand held long outboard shaft in the first place. The speed is of less importance - as long as the boat goes faster then 3 km/h, I will be satisfied. A packraft has very poor "gliding" abilities, even worse than todays inflatable kayak's. (But it floats on top of the water, so it blows easily with the wind, yes!).

The questions then, are:
Will this work at all?
Are my components ok?
Other suggestions for better components?
Are there any danger?
Could for example the ESC become overheated, and if so, what could be the worst outcome if that happens?


Last edited by Packrafter; 12-27-2020 at 11:12 AM.
Old 12-27-2020, 11:38 AM
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Packrafter
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Originally Posted by mfr02
you will probably get more control and power out of a manual paddle..
Here is a packraft with similar system and components. However, I can't tell exactly what components he is using. He achieves a speed of up to 4,7 km/h.

youtube.com/watch?v=HutFHeWgdZw ("Packraft with electric motor")
Old 12-28-2020, 02:13 AM
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mfr02
 
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Just looking at the numbers in the links, if the thruster and its motor wants a 40A ESC, the next rating up will do the job (60A in the examples shown). A 3S LiPo will give a nominal 11.1 volts, but probably more when freshly charged. 12 volts cuts into the safety margin. A fully charged "12 volt" SLA will be nearer 14 volts, so best to look at an ESC that is rated for 4S or more.
Making an ESC work harder than it should will cause it to heat up. What then happens depends on the design. Most electronics items are rated at an ambient temperature of 25C, operating at higher temperatures quickly cuts into their design margins.
An overloaded ESC might go into a thermal shut down mode, where it cools down and tries again. It might just let the magic smoke out, when it doesn't restart, ever. If it fails with a full short, the power leads start to melt. A fuse in the battery lead is a good idea. You do not want to be close to overly hot wires. Being close to a battery which is releasing all of its stored energy suddenly is also not good.
For real advice, finding a packrafting forum might be a better bet. Model boaters thinking is largely about getting the boat back, but without any worries about personal survival. Being on the boat raises a lot of other considerations. LiPo batteries with a rating for the demand that is going to be put on them are a fraction of the weight of any similarly rated SLA, but cost more and tend to need the right charger to do so safely. In between are NiMH batteries, it becomes a choice of balancing convenience, cost and weight, and deciding which is the best for you.
My inflatable kayker was probably putting out maybe 200 watts when paddling, 1/4hp or so for a gentle walking speed. A thruster will need to do much the same. 12 volts and 40 amps, when considering losses in the system converting electrical energy into mechanical, then whatever losses get introduced converting the motor output into moving water, seems about right.
I suspect that the control box in the Utube link is basically a servo tester (about $3) inside a nice box (probably a lot more)
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