Just received my JSII kit yesterday and am very interested in the answer to your question.  I've wondered about that very thing for several days now.  I will build the hull prior to ordering my sailing rig so I hope we can find out that this substitution is possible. 

Caveat: I ain't no sort of naval architect.  I may be all wet here.  However....

From what I've read, I'd agree that a sprit-boomed leg-o-mutton sail like those on the Jimmy Skiffs can be difficult to reef, and impossible if the sails are laced to the masts rather than hoisted, as I believe is the case with the Jimmy Skiffs.  Working boats using this rig generally had at least two different rigs, maybe "winter" with a smaller sail and "summer" with a larger sail, and the waterman would pick whichever one he thought would be best when heading out for a day's work.  If the wind got to be too much, he'd strike the rig and row.  Those were tough men and women in those days, and they tended to die young, anyway.

I couldn't find a sail plan of a gunter rigged Skerry for comparison, but, looking at the sail plans for the sprit rigged Skerry, the Jimmy Skiff II, and the gunter rigged Passagemaker, it looks as if they all place the center of the sail area pretty much right over their daggerboards.  IF the distance between the Jimmy Skiff II mast and daggerboard is about the same as with the Passagemaker with the gunter rig (the mast location with the lug is different), you MIGHT get away with it.

If you're clever with Photoshop, Visio, or some other tool which allows you to measure images, you might be able to check this by using known dimensions to get the two drawings into the same scale for comparison.  Mind you, the Jimmy Skiffs' daggerboards have consiterably more "rake" than the Skerry or Passagemaker, which may matter here.

I say this with a great deal of caution.  This whole business of establishing the "lead" (the distance of the center of the sail area ahead of the center of the lateral immersed plane area of the hull in plan view) in boat design is a mighty tricky thing, and even experienced naval architects sometimes get surprised.  The idea is to produce a result which gives the boat a wee bit of weather helm in most conditions, and never a lee helm, which is more complicated than just comparing the lateral areas in plan view.  Hull shape enters into it, as much depends on what happens as the boat heels, etc.  Also, the nature of sail rig plays a role, as well, e.g., tall vs. short, length of booms relative to boat length, etc.  However, with small, light displacement, shallow-bodied boats like these, maybe the location of the sail area relative to the daggerboard/centerboard/leeboards is the the main thing.  But, what do I know?  I just get this stuff from reading.

...or, you could call or write John Harris and ask his opinion.  He loves to hear from builders and surely knows more about it than I do!

.....Michael

���John and his crew are goid about getting back on questions. As for reefs in leg o mutton sails, it certainly is done, even with laced sails but easier with sail tracks . It's not CLC, but B and B Yacht Design does a lot of kits with such rigs. I've talked with Graham and Alan a couple times and they are serious on small boat performance. One key on the leg o mutton is being able to reposition the snotter . Here's a pic from their site of o e of their boats sailing with reefs in. No detail, but you can see the idea. Their rigging tends to be mote elaborate but not bad. I didn't build one yet because I wanted a simpler build at the time. http://bandbyachtdesigns.com/wp-content/uploads/2016/04/Graham-sailing-Carlita.jpg

���Crap. That's what I get for trying to post on my phone.

   OK, at the computer.  Let's see if I can do this:

In this system, there's a reefing clew that the sprint is pulled to, and a tack cringle, so the reef is pulled in sort of like on a marconi main, where the tack is pulled down after slacking the halyard and either hooked or downhauled with a tackle, the sprit is hooked or hauled to the reef clew, and the snotter is slacked so the extra sprit length moves forward of the mast.  The height of the sprit may also change.  

Bob,

What is it that you don't like about the JSII sail rig? It's actually a very good match to the boat's design goals and changing the rig can have some knock-on effects.

For example, the leg-o'-mutton is self-vanging. The foot of the sail keeps the sprit down, so the sheeting is lighter and the rigging is simpler since no mechanical advantage is needed. Switching to the larger gunter with jib means a heavier pull on the main sheet, as well as a second sheet.

The sheeting geometry also changes. With the original rig you pull from in front of the sheet, with the gunter you pull from behind. For most comfortable sailing, you may have to change your seating position from the center of the boat to the back, but that could upset your balance and make the transom drag, really slowing you down. The tiller could also end up too long and need to be shortened to keep from having it constantly knock into you.

There's also other issues, all of which can be addressed and eventually fixed, but my point is that you're trading a simple inexpensive rig that is tuned to the hull and designed sailing experience for something a lot more complicated with a lot more parts to buy, build and maintain. Maybe instead of just a different sail rig you really need a different boat?

I've been sailing Jimmy Skiffs off and on since the early 2000's and they are a delight to sail just as they are. I wouldn't go to all the trouble of changing the rig if it was my boat. I also understand that it's your boat, so you get to do what you want. I'd say keep in mind the couple of things that Gramps said - talk to someone at CLC about it and remember that striking the rig and rowing is a perfectly reasonable option.

Good luck,

Laszlo

Wise words from Laszlo, as usual.  I didn't mean to be as down on the sprit-boomed leg-o-mutton rig as I may have seemed.  As Laszlo points out, it is a simple rig which can make a lot of sense in a simple boat like the Jimmy Skiff, and it is another example of a "low-tech-is-go-tech" rig which can perform well without a lot of expensive hardware--exactly why Chesapeake watermen used little skiffs like this employing this rig for crabbing, a heritage from which John has drawn for the Jimmy Skiff designs.

The rig does permit easy flattening of the sail as it breezes up, which can mitigate the need for a reef, up to a point, and facititates feathering off the gusts.  As Laszlo points out, the sail remains flat, tame, and easy to sheet through it's range of motion (which is a lot--no shrouds or other standing rigging in the way), which also contributes to it being safe and effective in heavier wind.  As with other "low-tech-is-go-tech" rigs, e.g. the balanced lug, it's all about understanding what makes the rig work and then figuring out how to get it to work for you.

I just watched the CLC Jimmy Skiff II video, and I see that John had that one rigged with the sail hoisted on a track, which means it'd be easier to set it up to reef, if that is what's wanted.  In some of those shots, he's got her boiling along nicely in a good breeze without any strain, which should tell us something, too.

.....Michael

I have a question about the fordeck on the jII . Are there supposed to be cleats on the inside of the hull? There are stitch holes right there but I don't have a pre cut part to put there. Got plenty of ideas but I want to ask before I jump here