Hi,
I'm converting a GRP 'clinker' dinghy to junk rig and would welcome any advice.
The dinghy was apparently custom made for its original owner, but I suspect that any design was on the back of an envelope - the best example of which was the original rudder only just touched the water! (She now has a new rudder, made over the winter.)
The original rig is a standing lug, but this doesn't work well:
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The spars (yard, boom) are heavy and dangerous when hoisting and make the boat less stable than I’d like (I want to take small children out in it);
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The aspect ratio is less than one and the sail is cut flat, so windward performance isn't great;
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With the boom off (giving a curve in the sail) it goes to windward quite well on one tack; on the other tack it just goes downwind.
The overall aim is to end up with something that is:
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Fun to sail;
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Safe to take small children out in;
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Not too hard to build – this is a first project;
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Low hassle - quick to launch, easy to dismantle.
Naturally a junk rig seemed the obvious choice, with the caveat of keeping weight aloft to a minimum.
I’ve uploaded my current rough drawing.
The original mast is fairly short, so the drawing shows a replacement – an extremely light alloy mast from a windsurfer, 1.2mm wall, base 53mm diameter, top section tapered. I have my qualms as to whether it will be strong enough but it was very cheap so we’ll see… The original mast position is well forward so the key issue is getting the centre of effort far enough back to suit the centre board, which necessitates a large chord. The CoE is probably still a bit far forward – comments welcome. Possibly the sail is a bit big given the objectives? The design is based on Arne’s notes, for which I am very grateful.
The first sail might end up being a 200g/sqm polytarp as per this reference: http://www.duckworksmagazine.com/06/howto/junkrig/; ideally I’d use something like this given enough time: http://www.ripstopshop.co.uk/PBSCCatalog.asp?ItmID=10448738
Anything I need to change? I think my next task is to make up a dummy sail with garden cane and string to see how it hoists and furls (a full-sized model).
Thanks in advance for your comments.