Hi Arne, since we're on the subject of panels, what would be the consequences of adding an eighth (8th) panel to your design?

I started out with a fairly low-aspect johanna sail (AR 1.87) and lopped off a panel to lower the CE even more, resulting in a very low-aspect 6-panel sail (AR 1.65).  

I've been looking at different boats and considering the idea of repurposing the sail by increasing the aspect ratio and area by adding two panels (8 total, AR 2.07). This would allow the sail to be used with a slightly larger and heaver boat and get a better aspect ratio on the sail, at the cost of missing out on all the fun of building a completely new sail. Other than switching to an 8-panel sheeting arrangement (7 sheetlets?) for the extra panels would there be any other issues to consider?

Stavanger, on a rainy
1. Mars

Phil.
You can of course design your own top section  -   it’s a free world. Let me rather explain why my master sails ended up the way they did:

• 1.      I wanted to use seven panels as long as the AR stayed between 1.80 and 2.25. I have found seven panels to give about the ‘right step’ when I reef away a batten panel..

• 2.      I wanted a sail, which can be set with little balance. I prefer little balance  (5 – 15%) so that the mast will not cut too much into the cambered panels on the ‘bad tack’. The natural consequence of this is the yard angle of 70°.

• 3.      I wanted 10° rise in the boom, to get good clearance, and let me reef without needing to touch the topping lifts.

• 4.      I wanted the sail to be based on the Hasler-McLeod standard design, to get as easy lofting and sewing as possible.

• 5.      Last, but not least, I wanted all the batten panels to be of about the same area, over the whole range of master sails.

This last point is quite important to me: I had learned from the blue, cambered sail of Malena that her oversize top panels resulted in much increased twist in the sail. With an even distribution of sail area on all batten panels, there will be much less guessing and tweaking needed to get the sheet setup right. The transition panel is the joker here. With all other parameters set, the shape of panel 3 lets me fine-adjust the panel size so they all ended up about equal in area.

If you rather want to add a fifth parallelogram panel, I suggest you redesign the top panels so they end up at the same area as the lower panels. This will result in slightly lower peaking of the yard, but it should not be a big deal on that sail.

Good luck!
Arne

PS: If you have another look at the range of master sails, on Sheet 1 you will find the sail area written on each batten panel. You will then notice that the panels are of about constant size from panel 1 to 7, no matter what AR you look at. Getting this area distribution correct was the major job when I designed these sails.

 

I've cut and started sewing the four lower sail panels of a 200 sq ft sail scaled down from one of Arne's master plans with an A.R. Of 2.15, I have a question on the transition panel. With this somewhat higher aspect ratio I wonder about using the lower panel design (7-4) for panel 3. As the aspect ratio goes up the transition panel, no.3, grows closer to the parallelogram shape of the lower panels.  Also the size of a two panel head becomes smaller compared to low aspect sails. This has me considering that I might get away with a just the two panel head keeping the yard at 70 degrees but am unsure what I might lose. The batten of at the leach of panel two in a two panel head would be only 8 inches lower at the than the point where the long batten leaves the luff in a transition panel. It would add about 3.5 sq ft to each of the two top panels, an increase of 12% in the panels, and 3.5% of overall area. I think the benefits would be eliminating the longer batten, getting 7 sq ft more sail area than I'd planned and one less pattern to lay out. I'm not sure all the negatives. One cost would be eight more inches in mast height. How much would I lose in sail control as far as twist or in reefing? I must admit I don't have a good understanding of twist and wonder if I'm missing much usefulness of the angle and length of the longer batten beyond clearing the leach.