Barry Stellrecht wrote:

Jeff McFadden wrote: I am, as usual, competely befuddled here. Does a steep yard angle automatically provide more sail area on a given rig? True, it enables the peak to be carried higher, but what you gain in the peak you give up in the luff and to a lesser extent in the leach. Yes? Or no?

Err...I think it is a bit more complicated than that.

PJR Fig 6.28 shows how they construct the mast to fit on a sail.  It has to be a bit taller than the sling point (usually mid-yard).  If you know what sail you want and are about to build a mast, this tells you what you need to know.

I've already got a mast...

I'm in almost the same position, although not quite.  My current project is such a tiny boat that I have a maximum reasonable mast, and my objective is to put as much sail on that mast as I can.

 and I'm trying to calculate how the sails I want are going to fit on the masts.  I went nuts with an excel spreadsheet to model things and made a LOT of variations along the way and saw what happened.  In this case, for the same mast, I found that generally lowering the yard angle made for more sail area, up to a point, then further decreases didn't result in significantly more area.  If I were to go lower, it would probably start to decrease again.  This maximum area point is at a lower angle for sails with more balance.  Below is a chart showing my results for a bunch of earlier sail plans.

Yard Angle	Main (17% Balance) area	Mizzen (5% Balance) area
45	MAX	(not tried)
50	-0.1%	MAX
55	-0.5%	-0.5%
60	-1.6%	-1.5%
65	-4.3%	-3.3%
70	-7.8%	-6.4%

Both sails started losing measurable sail area at a yard angle above 50 degrees, but it still wasn't significant until 55 or 60 degrees.  It was a bit worse on the sail with more balance. 

That is very useful information to me.  My old flat sail was below 45%, due to an error in layout, but I think I'll just go with 45% on this one.

I've seen claims from reasonable knowledgeable people that aerodynamic efficiency is better for both low angle yards or high angle yards.  I'm mostly avoiding the question and going for an angle that looks like it will hang properly and allow enough sail area.

Since the 45% angle will obviously be more aerodynamically efficient, or either it won't. :-)

Jeff McFadden wrote:It seems to me that a high peaked sail also puts more sideways (bending) force on the top of the mast.???

I don't know.  Intuitively I would think that having more sail area up high puts more bending load on the top of the mast, rather than the yard angle.

Changing the yard angle would probably change the sail area or move it around, so it could have some effect.

Barry Stellrecht wrote: David & Kurt, thank you for your comments.  I appreciate the help and the challenges to my assumptions.  My goal here to build a simple, reliable, and good performing rig capable of crossing oceans.  I'm not trying to develop something new--just trying to get the best ideas previously tested to fit well on my boat.

Sail Shape & Area

I chose differing yard angles because of differing amounts of balance--It appears to me that for a sail with a lot of balance (my main) a lower yard angle will hang better, and for a sail with very little balance (my mizzen) a higher yard angle will hang better.  I've also gone toward yard angles that allow me to put up more area on my masts.  I haven't actually tried raising and peaking sails with differing balance and yard angles, so I could be completely wrong with this concern.

I haven't thought about the aerodynamics of yard angles, and I claim no expertise in that field anyhow.

Regarding the yard angles, what is "high" and "low?"  The Van Loan shape has a 55 degree yard angle.  Looking at a drawing of Poppy's sail, I see something lower, maybe 42 degrees (Can't find my protractor tonight)  Hasler-McLeod is usually 60 but they did use 70 sometimes.  Arne goes with 70 on his sails.

The sail area as designed is the most I could fit with the masts I've got.  I figured that easy junk reefing is my reason to put it up there.  I have enough sailing experience to appreciate too much sail for conditions being up, but I don't understand where I'll find trouble with having too much sail available.

I am somewhat concerned about raising the sail's CE too much over her original rig's CE.  But I figure that a reef is a quick fix for that too.

One other note--I worked pretty hard to get all the panels to have the same amount of area, by modifying the nominally triangular head panels.  This was based on Arne's observation that one of his designs had head panels too big, with some problems (twist, I believe).  With my high AR sails, I was trying to make my head panels bigger rather than smaller as Arne did on his later designs.

Sheeting & Dmin, etc.

I am planning to leave the top batten unsheeted.

I don't want double sheets--For me it seems like too much rope and too much bother.  (Same feeling about downhauls....but I've got less idea how they would bother me, as I've not really thought about how many I would need and how I would work them.)

I did select simple sheeting based mostly on the Dmin/P numbers.  Two batten spans of 1.25P or 1.38P would fit onto my deck.  Reading PJR on sheeting systems, any three batten spans needed significantly more length.  I didn't really want all the string of 6 (or 7) part sheets.

It looks like the main would just support a 1.75*P Dmin, which gives me options.  It should be easier to sheet--it has lots of balance, and I could easily put that sheet on a winch.  I think I will revisit its sheeting options.

The mizzen is a very high AR sail, but my masts pretty much force that on me, at least if I put them to good use.  The clew is too low to support a 1.75*P Dmin.  There is a track for the sheeting point just about on top of the transom.  This sail is smaller, but has less balance. It also doesn't have a reasonable winch to help me sheet it in.

If I were to raise the clew (probably by reducing height and hoisting it higher), I would be raising its CE even more compared to the original mizzen's CE, and that doesn't make me feel good.  Perhaps I should let this last objection go?

Tonight I am too sleepy to try and figure out how differing panel heights would affect sheeting arrangements. I'll get back to this later, along with anything else I was too tired to think about.

Please keep the comments coming!