The mizzen is useful in several ways. It has a sail area of only about 3 m² so doesn't offer a huge amount of drive, but it does help. When running, it can be deployed "wing on wing", to counter some of the yawing effect from the imbalance of the sail off to one side. In light airs it can help when tacking by being physically pushed over to windward to help as an "air rudder". It also is very useful as a "weather vane" when parking (heaving to), to help maintain a constant aspect to the wind. This effect is handy when at anchor to limit "fish tailing" on the rode. 

Plus it looks cool, which is important too.

Ok, here's a first draft for your comment and suggestions. I have kept the high angle top panel, and reduced the panels overall to 5. This still gives me a substantial increase in sail area to my current lug sail. It is based on your Johanna sail, scaled down from AR 1.8, but what it is now I don't know. :)

Here's the link to the photo in my album. https://www.junkrigassociation.org/resources/MemberAlbums/64623582/Junk%20Rig%20Sail%20Plans%20etc_/thumbnail/Junk%20Rig%20Draft.jpg

I can upload the file itself if that is more practical.

Steve, do you have a sailplan to show us, with some dimensions on it?

Arne

Well, here I am about to defend my decision to convert to a junk rig against two heavy hitters in the junk world! :)

Firstly, my decision to convert to a junk rig was "baked in" at the beginning of my build, but at that time I wanted to see how the boat handled as designed before going to the new sail. I had not sailed with a lugsail before and it seemed that there were many features similar to the junk sail, so I put off the decision until I had pretty much come to a conclusion after some experience. As it turns out I much preferred the sailing characteristics of the junk rig on my previous Hartley TS16. It was pretty much bullet proof in all weather and I never got into any trouble like I have on a couple of occasions with the lugsail. Yes the lugsail can be modified, but I still think it would not be a junk sail.

Secondly, I can significantly improve the sailing characteristics of my boat I am sure, particularly upwind, and in lighter airs. The first due to the better aerodynamics of a junk, the second because I can increase the sail area substantially simply due to the sail shape. The lug sails acceptably, but is both slow upwind, and doesn't point particularly well in any case. I cruise in the company of other sailboats, who are all bermudas, and I often lag behind on a long upwind run, which although I know that I won't achieve the close wind performance of a well tuned bermuda rig, this would improve with a cambered junk sail.

And on top of this, I am always up for a DIY project. I built the boat myself, and have managed several customisations on her already. This is one that I am very keen on doing.

As for the design of the sail itself, I was going to ask about the top panel issue. It seems to me that there are many junksails out there with a lower angled top panel, so I wasn't concerned about this. But there are other alternatives, such as reducing the sail to a 5 panel sail, which would keep the top panel and allow me to use my current mast. Actually the main reason for wanting to keep the current mast as is, is that I don't want too much overhang as the mast may exceed 6.5 metres, which is 1.5m longer than the boat. Not a major issue but it is a preference. If you think it is going to compromise the performance significantly I would keep the high angled top panel and either reduce the panels to 5 or extend the mast enough to accommodate it. Either way I am sure I can make it work.

And finally, I would still have a backup sail in the event that it is needed, which I don't have now.

Does all that make sense?

Steve wrote: I am planning a Johanna style cambered sail, with the top panel removed so I can keep the current mast as is. I can still get an increase of over 50% in sail area and no compromise on safety or sailability.

I might be getting a little out of my depth here - but I think that to get the maximum possible sail area from a given mast height, geometry seems to dictate a high yard angle and the concomittant low balance.

I am wondering, if you leave the top panel off, with the somewhat lower yard angle, you may find that you can't easily hoist the sail quite as high, and what you gain on one hand you lose with the other. (I do know that with very low yard angle sails (such as mine) more mast height above the yard is needed, or you are fighting against horizontal forces on the halyard). It all seems to come down to the angle between the halyard and the vertical when the sail is fully hoisted, which must not become too large. Which suggests to me that to get the maximum area from your mast height, the full Johanna sail might be best.

I stand to be corrected, and am interested to learn. Have you discussed this with Arne?