Hmm, thank you for the input Arne. I’m hoping the conversion will work because I’d rather not keep it as a sloop. I got ahold of some magazine (from the early 60s) of the sail plan. The mizzenmast in your drawing won’t work because the boat itself is set up to have the mizzenmast mast just behind the tiller.

‘’would making the sail smaller be better? To keep the mizzenmast where it is I mean. Or maybe a smaller sail can go more forward?

For trailering question, I can put it on a trailer because it fits in U.S. road limits. I would say that it’s a trailer sailer such that you can take it home every weekend. I would only take it home during winter. The vehicle will be my 3/4 ton suburban or I’ll by a 1 ton truck.

I was hoping I could raise the mizzenmast sail and be near the tiller and slowly , comfortably sail out of the harbor. Then when I’m clear of obstructions I can raise the rest of the sails and be on my way.

The panels I want to make are like Roger Taylor’s Mingming 2. The 4 bottom panels being separate and the top panels being one piece. Or I might try and make them all separate.

If it’s truly not feasible to do a junk rig, I’ll leave it as a sloop. The price was right and I’ve always wanted a yawl. Having one this size was too good to pass up.

On CLR CoE etc I think Arne has nailed it perfectly. I like Arne's expression "fudge factor". ("Magic art" and "educated guess" was perhaps being too polite).

Jan, referring to Dave Zeiger's "Thai lashing" method of attaching the individual panels to the battens - you might have missed the essential reason for it.

It's hard to make contact with Dave at times as he is often in remote areas, so in case he can't chime in ... (my first thought was, I'll bet he won't do that again next time! It must have taken a lot of work...)

You see, Dave was intending to use the "shelf foot" method to build his sails, but he ran out of time to make the shelfs for the mains panels, so he just attached the centre part of each panel to the battens, with longish lashings in place of the missing "shelfs". This left some pretty big gaps in the sail. I am assuming the lengths of the lashings are carefully varied along the battens, in order to dummy the shape of the shelfs and give the correct camber.

It must have taken a lot of work and time measuring bits of string and getting the knots in the right place. That might be another reason why the mizzen on that boat is uncambered!

I think Roger Taylor's "hinges" are also varied in length along the boom to give camber to the sail, and I must say I think that might be a better way if the panels need to be not sewn together, but that too must have taken a bit of time to calculate and measure accurately. The reason, I believe, was to be able to make the sail within a confined work space. Dean, why would you want to do that?

I think what Dave did was only intended to be temporary - interesting that the shelf foot sails did seem to perform perfectly well without the shelfs. Maybe that's the way to go - save a lot of cloth and a lot of sewing! Possibly saved time in the long run. It gives a whole new meaning and dimension to the term "split junk"!

Perhaps Dave stumbled onto something there!

I hope Dave can read this, and reply.

Dean, some of your comments raise slight misgivings - I hope before you make too many commitments that you contact Arne with some drawings of your proposed rig, and structural considerations etc. Its a lovely looking boat and with that long overhang aft the yawl rig makes a lot of sense.

Centre of effort: Wouldn't the pointy sloop CE, yawl CE, and junk CE all be the same given the same hull? 

In reality, there is actually no such thing as centre of effort (and also no such thing as centre of lateral resistance).

Both are moving targets, quite variable as the hull heels and pitches, and sails flex and billow and "angle of attack" constantly changes. They exist only in theory.

The convenient reference points which are used by designers, because they are static and simple to calculate, are usually referred to as CE and CLR but in fact they are merely the geometric centres of the sail and the hull profile.

There are rules of thumb as to how these two geometric points should relate to each other, [edit: the "lead"] but it is a bit of a magic art and I think experience on the part of the designer, with the type of hull in question, is what most likely will give the best (or optimal) relationship for most of the time. [edit: with some hulls the equations change markedly when the boat heels, so there is no "lead" which is going to be correct all the time - sometimes, with SOME boats, you just have to live with a bit of lee helm in light airs, and too much weather helm when the boat is heeling a lot. Or reef early.]

All of the articles I have read suggest the centre of area on a junk rig should be slightly aft of that of a BM sail.  I have noticed that too, so it probably means something.

However, for the record (I am speaking only of the SJR) Slieve, who created the rig, reasoned that in the case of a conversion from bermudan rig to SJR, the SJR should be able to have its centre of area pretty much exactly where the centre of area of the designed bermudan rig would go. So far as I know that has proved satisfactory in all cases, and it proved satisfactory on mine.

For the "contiguous" or "unsplit" junk rigs, Len is probably right. In any case, its only ever an educated guess, and I would follow the advice of the designers of those rigs.

As for Dean's suggestion of sailing on mizzen alone - I think Jan is gently pointing out that sailing on mizzen alone is hardly likely to be possible. Perhaps Dean was meaning "under mizzen and staysail alone" ie without the main. But with a junk mainsail, I am sure Jan's suggestion would be better. 

I'm interested too in your idea of sailing on mizen alone, surely you can sail out of the harbour gently on one or two panels of the junk rig when it's in place. The mizen will just be handy for balance.

As for making individual panel sails, isn't that what David Zeigler of triloboats.com did except they were laced on to each batten rather than the "curtain-tab" method. Is David Zeigler in Alaska and able to offer help?

Centre of effort: Wouldn't the pointy sloop CE, yawl CE, and junk CE all be the same given the same hull? 

Previously I was going to buy a boat here in Alaska. Right after that a 30 foot Yawl came up for sale. I've always wanted a yawl and this one can be trailered. That's another benefit. I can invest resources into it and not have to sell it if I move jobs down to the continental U.S.

I'm going to put cambered Johanna sails on there but do the Roger Taylor mod where he makes separate panels. Does anyone know if drawings like that have been put on the website? I haven't found them if they're on here.

I've got the mast located far forward because I don't know where the CE is with the yawl. I've only got the sloop CE. from my drawings though I think I'll locate the mast step in the forward half of the water tank. That'll mean I can have mast partners on a flat deck instead of trying to get it to work where the coach roof comes up.

I plan on keeping the mizzen mast. We have fairly constant winds in Seward AK. With the mizzen I think I'll be able to sail out of the harbor nice and gently with mizzen alone. That will be cool.

The nice thing about a boat this size is I can put a heater in it and try my hand at some winter sailing.

I'm going to buy a 38 foot flagpole. I need to do the math but I'm guessing it will work as a mast. 38 foot is the longest one section flagpole that I can guy. Flagpole stores sell them listed as 35 feet with total length of 38 feet. I've used two of Johanna's sail plans, scaled to the sloop drawing to get what I think is going to be the sail layout.

The mast weight is over Arne's goal of 2.5% of the boats displacement. Not a lot but some. I wanted the sail to be as high and as large as possible because we have light winds here.