You have a point there, Hans-Erik; a sheltered place for the watch-keeper is nice to have. The suggested rig, with central sheeting on the mainsail, should also be easy to keep from snagging people in the cockpit. An arc (bar) over the aft end of the cockpit would do wonders.

David Tyler’s worries about making the sails this big, are quite rational. As the sails are being scaled up, the people on board are not. The forces in the sails and sheets can be dangerously high, so things must be properly organised to avoid problems. However, since the JR is handled entirely by pulling on strings, it is mostly a question of gearing down the forces with blocks and winches  -  and then keep the tails tidy. The result in this case is slower handling than on a 20sqm sail, but after all, when the sail has been hoisted and trimmed, there is not another sail waiting for you to do it all over again (..the triangular sprit-boom mizzen is set first, and is just a toy, compared to the main...).

To make sewing and rigging the big sail easier, one may finish it as two sections, so that the upper and lower section is tied together at batten 3 from top.

Performance-wise I am convinced that a Gazelle with this yawl rig (and with camber in the main) will sail rings around a sister boat with the original Colvin rig.

The rig is quite similar to the one fitted to Pol Bergius’ Cornish Pilot 30, ‘Annie’, and Pol is very happy with it. Unlike on Annie, there will be much better work space on the foredeck of the Gazelle.

Arne

David,

My main reason for starting with this yawl rig was that I don’t know where the Gazelle-owners would accept to have the masts. A schooner or ketch without a jib would not work with the original mast positions, and I wanted to do away with the jib. The suggested mainmast (raked 1° aft) fits in the original foremast’s position, so I just tried to see how it could be combined with a mizzen to get the CE right.

I think it looks promising. The sail’s chord is only 69% of the waterline, so steering downwind should be doable without adding a Thompson rudder.
As for size of the sail, it depends of what sort of sailing the users have in mind, and how strong the crew is. For coastal cruising, I think this rig will be good. Hoisting the sail can easily be left to an electric winch. The energy needed to hoist such a (100kg?) sail is surprisingly low. The mainsail of the schooner Samson is 70sqm, and the owner still hoists it manually. His use of separate upper and lower (central) sheet lets him have good control. The sloop JR of Peregrine is 80sqm, and that boat has done a lot of offshore work. After a couple of years, they added an electric winch for the halyard.
The mainsail I suggest could be made in any size between the shown one and down to 60sqm. By simply removing the lowest panel of the shown sail, the area would drop to 61.4sqm and the mainmast could be shortened with 1.5m, leaving it shorter than the original mainmast.
That should be doable.

There are still many loose ends here. The actual keel appears to vary with different boats, and as said, the intended use must be counted with.

Arne

PS: I'll mail you the sailplan in .dxf format, so you can play around with it.

Here is my first go at designing an alternative JR for a Colvin 42’ Gazelle. This ended up as a yawl, which lets one make use of the original foremast opsition. I have given the masts a 1° aft rake. I suggest using double (central) sheeting with the upper sheet being a 4-part purchase and the lower sheet with 3-part sheet. I have seen this in use ona 70sqm junksail and it works fine.

My guess is that performance  (with cambered panels) will be much improved and handling will be much easier than with the original rig.

The chosen JR is actually taken from the same master sail as the rig for my Ingeborg( 35sqm), with AR=1.90. That planform has proven to work well.

If two junksails are to be used, I guess a ketch will be needed to get the CE right.

Arne

Maxime wrote:

Arne,

I wasn't able to find the sail plan with the keel profile. I think I have the full plans somewhere in storage, but not at hand. I found a fairly clear profile photo of a Gazelle out of the water, though.

I'm a little dismayed by this report that it can't sail upwind at all, not even a close reach, if there are any waves at all. But then, I'm a total newbie, so I don't know if that's normal!

Max

OK, and the LOA without bowsprit is 42ft, right? Now I see that the boat on the photo is a hard chine design. I thought the Gazelle had a round bilge. Anyway, the sailplan seems to show the CE of the total rig, which is helpful. 

Arne

Is there a clear sailplan available (hopefully also showing the keel profile), so guys like me and others could play with and hopefully design a better sailplan for it?
To me the hull appears to be allright.

Arne