David,

for such a little rig I suggest you rather make a wooden mast. If you can find two good 2-by-4” spruce planks, 5 to 5.5m long, you would have what you need to build one. My Oslo-dinghy, Broremann, at around 220kg was given a 5.3m long spruce mast at 9cm diameter (4cm in the top), after a season with a borrowed mast with only 7cm diameter.

The 9cm mast came out at 10.0kg. It has a big advantage over the straight aluminium tube in  that the mass centre is lower and the slimmer top section also has less windage. The 2-pot varnish I gave that mast is both robust and long-lasting, so will do without re-varnishing for several years.

If you look up the second article I wrote about Broremann, you will see more details.

Anyway, good luck!

Arne

Hi David

I've just seen your posting as I'm currently in very limited contact while in the Norwedian fjords, but will be back home very soon and contact you then. You have some interesting ideas and I'd be happy to discuss them with you.

Cheers,  Slieve

Hello, I recently joined the JRA having taken an interest in Junk Rigs since Poppy's article in PBO.
I have a MKII Wayfarer (designer Ian Proctor) dinghy which I am thinking of converting to Junk Rig. There are over 10,000 of these dinghies (4.8M, 15'10") being raced and cruised around the world. It has a Bermudan sail area of 13.5M2 or 140Sqft.
My reasons for thinking about converting are the ease of single-handed reefing and the reduction of active sail control to basically just one sheet. Another reason is that I hope to shorten the mast to enable me to sail under a local bridge (5.5M@ Highest Astro Tide)without having to lower the mast each time I go in and out.
The boat is of GRP construction and has a large buoyancy tank, just forward of and underneath the foot of the the mast, which I do not want to modify as the buoyancy is a safety feature necessary on a dinghy. I hope to use a split junk rig and maintain current mast position. The max mast length above sea level I can use is approx 5.5M. With this restriction, I have found the CE of the original Bermudan rig, drawn up a junk rig of max luff length 4M and found its CE iaw PJR guidelines. With the Junk CE placed on the same line over the Bermudan Rig CE, I end up with a balance of 28-30% forward of the mast. The Junk CE is taller than the Bermudan. But the aspect ratio is only 1.23. PJR recommends a min of 1.4. What would the effects of the lower Aspect Ratio be? Is it unusable?
Also,the original mast section is only 54mm across, fits in a tabernacle and is sort of keel-stepped onto the top of a buoyancy tank. As I am restricting myself from major structural modifications, I was thinking of making a steel (for strength) structure , to fit in the original tabernacle, and rising above the deck to the height of the junk boom. The structure would be widened above deck level to whatever diameter would be appropriate for the mast required for the original sail area. This steel structure would then be braced just below the boom by short shrouds coming from approx the same area (which would probably have to be strengthened) as the original bermudan shrouds and a front shroud coming from the original forestay position (already reinforced). The new junk mast would slot into the steel tabernacle and be attached by a bolt. A timber insert would help strengthen and support the steel where it changes section from 54mm to the new mast diameter. What do experienced Junk builders think of this idea? Would steel shrouds, more or less using the original shroud and forestay positions be good enough to take the forces of a swaying bending junk mast.
Finally, the original sail area is 140 Sqft or 13.5 SqM with 30-32% in the Genoa. Could anyone recommend aluminium tubing sections/materials and suppliers in the UK for the mast and battens if my above proposal sounds at all feasible.
Unfortunately, despite trying to use paragraphs to make this post easier to read, I haven't been able to transfer them through to the forum text. Sorry about the long post, Regards David.