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Torque of Rudder Servo

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Torque of Rudder Servo

Postby nabberuk » August 1st, 2016, 7:41 am

I'm building an RS2000 hull that will sail autonomously across the Atlantic (well, that's the attempted plan).

I'm just trying to analyse the spec of rudder and sail motors i will need. Does anyone know what sort of forces both the sail and rudder will encounter on a RS2000?
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Re: Torque of Rudder Servo

Postby racingSparrow » August 1st, 2016, 1:51 pm

Wow an RS2000. A big model indeed. The rudder would need some power for sure. Probably not as much as you might imagine I would say.

It depends on the size of rig you plan on carrying which I'd imagine would be quite small to cope with high winds.

I'm not sure on exact specs but quite a large rudder servo with 4kgs+ of power. The sail would need to be a winch. The most simple setup however would reduce risk. A sail arm is simple compared to a winch.

In saying this, the type of sailing this boat would be doing wouldn't be your standard model sailing with constant trimming and refinement of boat placement in the water. It would be set and forget, very forgiving sail setup so less battery power gets used throughout the day adjusting trim. The rudder would then be doing most of the work keeping the boat powered up.

Very interesting stuff.
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Re: Torque of Rudder Servo

Postby m-o-t- » August 3rd, 2016, 4:58 pm

I have been following the autonomously across the Atlantic attempts my self very interesting.
2m boat is a big boat, I would be interested in following your build.
I considering doing something similar but as I am in Sydney I was thinking of using New Zealand as a marker buoy ;) and doing a round trip back to Sydney.
I was thinking a 1.2m sparrow boat design with a solid wing for the sail.
Have started with a test boat and now looking at moving to full size test boat.
Lots to think about to make it have any chance of working
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Re: Torque of Rudder Servo

Postby racingSparrow » August 3rd, 2016, 5:17 pm

I have thought about this topic quite a bit myself. I feel like the racing sparrow is perhaps not the best design for the task. It's great people like the boat, don't get me wrong, but if you're going to go and spend so much effort on a project like this I think it's fair to harshly critique the suitability of the design.

The racingsparrow is designed for a lake / pond via remote control with moderate / light winds. Big waves, I mean huge waves 7m+ out on the open sea would need a special kind of hull. A big concern would be a long keel with bulb to catch on debris / seaweed / jelly fish etc.

I have designed a hull (sketch) that could handle the debris aspect. It is not too different to an old ship from the 1800's with a full keel rather than a wing.

The rig too would need to have some great range and be super simple. Perhaps a stayless thick carbon tapered rod. Like a laser dinghy rig that can react to gusts automatically, not requiring constant trimming and balance.

It is a subject I would like to delve into more, perhaps design a boat for these long haul missions with the huge variety of conditions and autonomy it would need.

It is something that rarely succeeds.

The coolest drone sailboat i've come across is this:
http://saildrone.com/

are there other sites?
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Re: Torque of Rudder Servo

Postby BiggsDarkLighter » August 7th, 2016, 9:41 am

I found a few more hunting, but nothing that even came close to the Saildrone. What an AWESOME idea!

I would say that using a center hull, perhaps a Racing Sparrow one, with outriggers like the Saildrone would work. But I am also thinking that the solid wing idea for the sail is almost mandatory.
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Re: Torque of Rudder Servo

Postby nabberuk » August 7th, 2016, 8:53 pm

I'm planning on using a depowed rig and Ive added some more buoyancy to the hull. It may not be the perfect hull but it will certainly float and sail.

Looking at all the past attempts the main issues tend to be;

- mast isnt strong enough
- power failure
- rudder arm failure
- boat is too small that it struggles to get out of the tidal pull near the coast
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Re: Torque of Rudder Servo

Postby m-o-t- » September 7th, 2016, 6:46 pm

Here a autonomous that made it from California to Hawaii next stop New zealand
http://makezine.com/2016/08/22/solar-po ... mous-boat/
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