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Old Dec 28, 2012, 04:43 PM
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Joined Sep 2012
6 Posts
Help!
DIY (very) SailBot build

Hello forums.

I'm working on an autonomous sailboat for a Science Fair Project.

My budget is very limited (obviously problematic) so I've opted to use the materials on hand.

I've slapped together something of a monstrosity with some ripstop nylon, and Aeromarine Rio Roses hull, an old fishing pole and some epoxy.

Now that I have... something... of a rig, how should I go about setting up my sail winch? I've found directions but they all seem to be specifically for a type of boat.

Is there a "universal" way to do this?
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Old Dec 28, 2012, 05:20 PM
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Australia, TAS, Penguin
Joined Mar 2012
550 Posts
Gday Captain_Dimak

Firstly you do not mention how large the boat is, this will affect what you need to do.

Googling "Aeromarine Rio Roses " comes up with a 21" hull for a fast electric - this will provide you a lot of challenges to make a sailing boat.

Firstly, I would assume that hull has no keel fin? Certainly Google Images suggests that... If so, I would suggest that you need to add a keel fin about the centre of the boat - it needs to be maybe 6 or 8 inches long with about 300 grams of lead on the end. Maybe a couple of rulers and a fishing sinker? Without a keel fin it will just be blown flat in any sort of wind.

I will also assume you are planning a sloop/bermuda rig using one central mast with a mainsail behind it and a jib in front of it.

Next step is to work out how much sheet travel you need. A reasonable guide would be the distance from the mainsail pivot (gooseneck) to where the sheet attaches to the boom plus a bit. The correct amount of travel will allow the boom to be hauled right in (parallel to the centreline) or sheeted right out (right angles to centreline) For example, if your attachment point is 100 mm from the gooseneck, then you will need about 140mm travel...

The distance from main boom pivot to the main sheet attachment point should be the same as the distance from the jib pivot point to the jib sheet attachment point. This will allow you to control both sails with one winch.

For a boat this size, you may be able to use a standard (largish) servo with an arm - making an arm type winch. Standard servos usually swing 90 degrees so you can work out arm length and travel with the formulas relating to chord of a circle. You can also use double haul to get twice the travel (but half the torque)

If the arm type does not work out you will need to go to a drum type winch. With these, the travel is circumference of the (winding face of) the dum x number of turns. Sailwinches are typically 4 to 6 turns. They are available online, search around a bit, there are some cheap ones (HobbyKing is a good place to start if they have any stock)

Hope this gets you started...
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Old Dec 28, 2012, 06:05 PM
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Joined Sep 2012
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mrpenguin,

Thanks for the reply.

The hull is 30" long and I have a mast and sails already on it (mast is ~630mm).

I'm putting together some insulation foam outriggers with daggerboards on them. I have an interesting steering method: a control rod will connect to the daggerboards (which are mounted on a hinge) and turn them back and forth via a solenoid or servo. (edit: i'll have a fixed rudder in the stern)

Thanks again for all the info. I'm going to try to replicate what you say.
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Last edited by Captain_Dimak; Dec 28, 2012 at 06:07 PM. Reason: clarification
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Old Dec 28, 2012, 06:38 PM
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Ontario Canada
Joined Mar 2009
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Quote:
Originally Posted by Captain_Dimak View Post
mrpenguin,

Thanks for the reply.

The hull is 30" long and I have a mast and sails already on it (mast is ~630mm).

I'm putting together some insulation foam outriggers with daggerboards on them. I have an interesting steering method: a control rod will connect to the daggerboards (which are mounted on a hinge) and turn them back and forth via a solenoid or servo. (edit: i'll have a fixed rudder in the stern)

Thanks again for all the info. I'm going to try to replicate what you say.
A fixed rudder in the stern will be fighting the hinged rudders you mentioned.
It will will try to keep it going in a straight line.
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Old Dec 28, 2012, 07:11 PM
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Joined Sep 2012
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That's the idea. if I have two fairly large daggerboards (and speed isn't an important factor) then it should be able to turn and then continue straight.

Since it's autonomous, that lowers the number of turns I have to make in the programming.
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Last edited by Captain_Dimak; Dec 28, 2012 at 07:14 PM. Reason: clarification (again)
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