Below deck autopilot

[testmonkey]

Why not use an innertube as a lifejacket whist your foraging!

Though not been sailing long, the autopilot is a the very top of my safety on board equipment list

I would not be without a well engineered and reliable system

Fiat starter motor? Yiu having a giraffe?

If Fiat's not good enough then how's this as an autopilot drive unit? It's apparently built from a truck windlass and RC plane motor

 

[maby]

Where home made is concerned, I guess it comes down to the question of how good you are with your hands and how much free time you have. You are only talking about building your own drive unit and a medium power Raymarine unit costs less than £1,500. My bet is that, starting from scratch, it's going to take a good engineer several weeks of hard work to come up with something that is simultaneously reliable, sufficiently powerful and small enough to mount in the available space. How highly do you value your time? I'm pretty sure I can earn enough to buy the Raymarine unit in less time than it will take me to design and build an acceptable replacement. (And I am an experienced engineer, though I don't now have access to all the good things like a lathe and milling machine)

 

[DaveS]

this got me into thinking - what electromechanical part readily available at any scrap yard has a built-in clutch you drive with 12v power? Well any automotive or motorcycle starter! So how about salvaging e.g. a fiat uno flywheel, removing excess weight, bolting it to the rudder stock under deck, then build a bracket for the starter. To engage the autopilot apply voltage to the solenoid and by providing positive/negative voltage to starter from control head steer the boat. Automotive starters come in many sizes so with some experimenting or calculation an optimal size might be found... If this works all mechanical parts could be found for very low cost. Then some diy electronics to drive it. To get a head start in autopilot software & control board the ArduPlane & DIY drone projects might help http://diydrones.com/profiles/blogs/ardupilot-mega-home-page https://code.google.com/p/gentlenav/

While I have absolutely no problem with re-using scrap bits for a boat - which some seem to find a bit offensive (a bit like the guy in Zen and the Art of Motorcycle Maintenance who refused to contemplate sullying his BMW by using a bit of beer can as a shim to secure a loose handlebar control), there is one practical problem with using a starter motor. It's a series wound device and will turn in the same direction regardless of the applied polarity.

 

[uxb]

I could attach a car windscreen wiper motor to my steering quadrant- that would work at least as well as my current autopilot...

 

[AngusMcDoon]

I'm pretty sure I can earn enough to buy the Raymarine unit in less time than it will take me to design and build an acceptable replacement.

That's not the point of YAPPfoolery though. The point of YAPPing is to have no point.

 

[nimbusgb]

Magnetic clutches that work on only 2.5 watts, put between motor and pinion drive.

http://www.tinyclutch.com/magnetic-clutches/

 

[nimbusgb]

I'm pretty sure I can earn enough to buy the Raymarine unit in less time than it will take me to design and build an acceptable replacement.

At £1400 plus ( Raymarine type 1 from the US - plus shipping and VAT at import ) perhaps not and certainly a valid YAPP project.

Using one of the widely available hobbyist autopilots one could develop an inboard autopilot and actuator for significantly less than £1000 all in and that would include a heading sensor, 3 axis gyros and accelerometers and enough grunt to do waypoint following etc.

 

[maby]

At £1400 plus perhaps not and certainly a valid YAPP project.

Ah, well - but it had not been proposed as a YAPP, as far as I can see.

As far as cost is concerned, £1400 is only a little over a month at minimum wage - and I would suggest that it would take that sort of time to do an acceptable job of designing and building an acceptable drive unit. Fine, if you have plenty of time on your hands, but not something to make you give up the day job!

 

[nimbusgb]

Ah, well - but it had not been proposed as a YAPP, as far as I can see.

As far as cost is concerned, £1400 is only a little over a month at minimum wage - and I would suggest that it would take that sort of time to do an acceptable job of designing and building an acceptable drive unit. Fine, if you have plenty of time on your hands, but not something to make you give up the day job!

Less tax, less NI, less food and petrol and insurance and payments and rent. £1400 is a hell of a lot more than one months 'disposable income' for a LOT of people! not that someone on minimum wage is likely to be looking at a £4000 autopilot are they. I'd guess that £1400 is more than a few people on £50k per annum could happily fork out in a single month let alone a single transaction!

 

[maby]

Less tax, less NI, less food and petrol and insurance and payments and rent. £1400 is a hell of a lot more than one months 'disposable income' for a LOT of people! not that someone on minimum wage is likely to be looking at a £4000 autopilot are they. I'd guess that £1400 is more than a few people on £50k per annum could happily fork out in a single month let alone a single transaction!

Perfectly true - but my comment was meant to be a bit tongue in cheek. I was trying to point out that you have to value your time pretty cheap for it to make sense economically to build your own linear AP drive - there are, of course, other reasons to build something like that yourself - personal satisfaction, for example. I would not fork out £1400 every month on boat bits - one does rather hope that your AP drive is going to have a service life measured in years.