Model Boat Mayhem

The Shipyard ( Dry Dock ): Builds & Questions => Yachts and Sail => Topic started by: rmaddock on July 18, 2011, 04:32:50 pm

Title: Some early thoughts.
Post by: rmaddock on July 18, 2011, 04:32:50 pm
The summer holidays are nearly here  O0 and while I've still got an assignment to write  {:-{ thoughts are turning to the "project".

See HERE (http://www.modelboatmayhem.co.uk/forum/index.php?topic=30888.0).

Before I do anything to the hull, I'm trying to get my head around what needs to go in there, and where. Thoughts so far are:

to alter the ratios of the fore and main sheets so that I could effectively move the rig's CE forwards and backwards as I sail.

I'm sure I'll think of some more as I go. Can you tell I've been reading proper sailing books? Probably a mistake. I realise that it'd be silly (but not impossible) to recreate in RC all of the controls available even on a turn of the century sail fishing boat but I'm sure it'd be possible to get quite a lot of trick things going on.

Any comments? I'm sure I'm not the first. Can anybody point me at builds like this that've been done before?

There's nothing like being ambitious!  {-)

Robert.
Title: Re: Some early thoughts.
Post by: rmaddock on July 22, 2011, 04:50:16 pm
I dug my PICAXE developer board out today. It's got a, now, antique 18X chip on it but it served the purpose for today.
I've managed, rather easily, to get the PIC reading the signal from a receiver and turning a light on and off. Not exciting, I know, but it'll lead on to dual foresail sheet control before you know it.
HERE (http://youtu.be/eCGJq0Od43Y) is a very boring video of a very strange man demonstrating it.  :embarrassed:

http://youtu.be/eCGJq0Od43Y
Title: Re: Some early thoughts.
Post by: rmaddock on July 25, 2011, 06:39:57 pm
My, but you're all seriously underwhelmed by this, aren't you?  ;)
Never mind, I shall carry on regardless  :P Genius is often ignored.  {-)

Here's another demo video.....more obvious this time, I hope. Two servos being controlled in turn from the throttle stick and the gear switch used to change tack. There's still some jitter in the servo's that I'm working on ironing out at the software level but I think you can see where I'm going with this.  %%

http://youtu.be/iglPu5DVjPE (http://youtu.be/iglPu5DVjPE)
Title: Re: Some early thoughts.
Post by: tigertiger on July 26, 2011, 03:47:17 am
Maybe trying to teach you how to suck eggs.

If you are looking at controlling several servos on one channel, but with different throws, have a look at the ACTion Electronics ServoMorph gadget.

There are also a number of switches that will allow you to control different things on the same channel at different times. And I believe you can do the pulse thing with stick channels as well. Although multi channel TX are not always expensive.

I would also suggest a big model is easier with all that running rigging and halyards for raising sails etc. Getting sails to go down may be a bit difficult as model sails do not have a lot of weight. If you add weight to the top of the sail, this will be high up when sailing and need to be compensated for below the water line. The alternative would be to run the halyards in a loop, so that they pull up and pull down,.
Title: Re: Some early thoughts.
Post by: rmaddock on July 26, 2011, 08:29:26 am
Hello Tiger!

Thanks for the comments, but I don't think the Action stuff does quite what I'm intending. There's been a recent posting on here (that I can't find now) in which the correspondents came up with a complicated arrangement of 3 (or was it two?) servos, some on sliding mounts, to control the foresails of a scale model. The intention was to get the unused sheet to be slack to allow the sail to set properly and realistically.

That's what I'm trying to do here. I'm trying to recreate the effect of having two separate jib sheets and a crewman working them for you.  I will issue the order to "tack" by switching the gear toggle on the Tx. This will signal the PIC to let both sail sheet loose. The foresail will flap...this should reduce it's reluctance to tack.  Then, once through the wind, I flick the toggle back again and now the signal from the main sheet stick will be sent to the other side. And vice versa. So I'm trying to both select a channel but also feed another proportional signal through to that channel.

It's probably massively overkill and hugely expensive on servos or winches but I'm enjoying getting it to work  %%

As to raising or lowering the sails, I had a closed loop system in mind....but may give it a miss right now simply due to the complexity and expense I'm already letting myself in for  <*<

Cheers!

Robert
Title: Re: Some early thoughts.
Post by: Netleyned on July 26, 2011, 03:49:45 pm
If she is slow coming through the wind on to the opposite tack you could get her to back the jib to help her round

Ned
Title: Re: Some early thoughts.
Post by: dreadnought72 on July 27, 2011, 12:01:02 pm
Hello Tiger!

Thanks for the comments, but I don't think the Action stuff does quite what I'm intending. There's been a recent posting on here (that I can't find now) in which the correspondents came up with a complicated arrangement of 3 (or was it two?) servos, some on sliding mounts, to control the foresails of a scale model. The intention was to get the unused sheet to be slack to allow the sail to set properly and realistically.

It's here (http://www.modelboatmayhem.co.uk/forum/index.php?topic=22679.msg307983#msg307983), Robert.

I like the idea of using a microprocessor for sail control ... but as you go down this route, I can't help but feel that the natural end result would be something along the lines of how you really sail a boat. For example:

You could use the Picaxe inputs to monitor the tension on the sheets via something like the PICOSTRAIN (http://www.acam-usa.com/Strain-Gage-Circuits.html). If the strain is ~0N, then the sheets are loose. Tighten them until the sail's drawing, and no further.

Get the software to constantly "play" the sheets - keep them just drawing.

Human input would then boil down to steering only - the boat would be doing the work of the sailing.  :-))

Andy
Title: Re: Some early thoughts.
Post by: rmaddock on July 27, 2011, 01:06:52 pm
It's here (http://www.modelboatmayhem.co.uk/forum/index.php?topic=22679.msg307983#msg307983), Robert.

I like the idea of using a microprocessor for sail control ... but as you go down this route, I can't help but feel that the natural end result would be something along the lines of how you really sail a boat. For example:

You could use the Picaxe inputs to monitor the tension on the sheets via something like the PICOSTRAIN (http://www.acam-usa.com/Strain-Gage-Circuits.html). If the strain is ~0N, then the sheets are loose. Tighten them until the sail's drawing, and no further.

Get the software to constantly "play" the sheets - keep them just drawing.

Human input would then boil down to steering only - the boat would be doing the work of the sailing.  :-))

Andy

And then they'd take over the world!  :o {-)

I know what you mean.  I'm not sure I'd want to go that far.....although my mind has wandered in that direction recently. I even wondered about using the picaxe GPS module and simply telling the boat to go to the other side of the pond.  O0 But maybe not this week.

Things like the foresails though seem to be a compromise at the moment. I thought my picaxe solution would be like being the skipper and shouting at the crew.  >>:-(

I've nearly got the software sorted now. I wanted to make sure it'd work before I started fitting the hull out with lots of winches.

Thanks for the link b.t.w.
Title: Re: Some early thoughts.
Post by: Watchleader on July 28, 2011, 04:20:24 pm
Hi Maddock
As this project comes on stream, you really must run it as a build blog.   :-)  :-)
I know it would be followed with much interest. O0  O0
Look forward to it. :-))  :-))
John
Title: Re: Some early thoughts.
Post by: rmaddock on July 28, 2011, 06:12:18 pm
I know it would be followed with much interest. O0  O0
Look forward to it. :-))  :-))

"Me thinks the lady doth protest too much!"  :embarrassed:
But then I'm also always up for a bit of narcissistic blogging.  :-))