robert self wrote:

Erik and Evi Menzel Ivey wrote:

A factor driving the decision, other than what I've previously discussed, is space.  I think I would need space equal to the full panel size to properly lay out and loft the sail if I were to use either the barrel method or the shelf method.

Hi Erik--I too have space constraints but came up with a work-around that allowed me to sew-up a 550 ft^2 split junk inside the cabin space of a 35 ft'r. But there is the additional cost for a canvas shop to cut the pieces for you to sew ($680 to cut & ship the 550 sqft in 12/2016).

Fortunately for us on the west coast USA Amy Poe at Wyckam Canvas http://wyckam.com/ in Portland, OR has cut out the pieces for both of my sails. Husband and wife team. He is the North Sails rep and she runs the canvas shop. I send her my DXF files from QCad. She cuts the pieces from her fabric inventory or you buy fabric elsewhere and drop ship to the shop (I bought Odyssey from Rochford). The fabric cutouts delivered to you will have the seam offset penciled in. You line up the offset. Use 2-sided tape and staples to keep the pieces together while you sew a seam. No full scale lofting req'd.

The largest panel I've sewed was 1.3m x 5.95m. You've previously mentioned 1.45m x 4.1m sized panels. So we're in the same ballpark.

Example 3-piece panel with seam offset rotated 10 deg to align with fabric.

Meshplot of my best guess of panel shape.

Test sail last month in F1-F2...boat barely heeling. I'm happy with the set in this very light wind. 

Summary of my steps:

1. Panel shape, dimensions, camber, rise, sheeting angle are determined in a spreadsheet. I use 1:5 scale.

2. X,Y coordinates for the shapes copy-paste to text files.

3. Use free Libre_CAD program to load coordinates from the text files..save as dxf file.

4. Use Qcad to furthur manipulate dxf files.

5. Email final dxf files to Wyckam Canvas.

I'd upload the spreadsheet but can't find how to do it; and I only find one XLS file on the whole site on Slieve's public access page so perhaps loading an executable might be restricted. Contact me offline if you want the spreadsheet.

robert self

My plan is to have the cloth cut or at least lofted by my BM sailmaker.  His table is size is something like 2mx 12m.   Its good to know of another source.  I think Odyssey III, with the coating can be cut with a standard cutting wheel and it will not unravel.  I am considering using Weathermax or a Topgun line of fabric that doesn't have a coating and thus should be cut with a hot knife. I've not had luck in finding a outfit that does that, so presently I am planing of doing the cutting myself. The design I am using has all straight lines though, so it sounds doable.  

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Erik and Evi Menzel Ivey wrote:

A factor driving the decision, other than what I've previously discussed, is space.  I think I would need space equal to the full panel size to properly lay out and loft the sail if I were to use either the barrel method or the shelf method.

Hi Erik--I too have space constraints but came up with a work-around that allowed me to sew-up a 550 ft^2 split junk inside the cabin space of a 35 ft'r. But there is the additional cost for a canvas shop to cut the pieces for you to sew ($680 to cut & ship the 550 sqft in 12/2016).

Fortunately for us on the west coast USA Amy Poe at Wyckam Canvas http://wyckam.com/ in Portland, OR has cut out the pieces for both of my sails. Husband and wife team. He is the North Sails rep and she runs the canvas shop. I send her my DXF files from QCad. She cuts the pieces from her fabric inventory or you buy fabric elsewhere and drop ship to the shop (I bought Odyssey from Rochford). The fabric cutouts delivered to you will have the seam offset penciled in. You line up the offset. Use 2-sided tape and staples to keep the pieces together while you sew a seam. No full scale lofting req'd.

The largest panel I've sewed was 1.3m x 5.95m. You've previously mentioned 1.45m x 4.1m sized panels. So we're in the same ballpark.

Example 3-piece panel with seam offset rotated 10 deg to align with fabric.

Meshplot of my best guess of panel shape.

Test sail last month in F1-F2...boat barely heeling. I'm happy with the set in this very light wind. 

Test sail in F3-F4.

Summary of my steps:

1. Panel shape, dimensions, camber, rise, sheeting angle are determined in a spreadsheet. I use 1:5 scale.

2. X,Y coordinates for the shapes copy-paste to text files.

3. Use free Libre_CAD program to load coordinates from the text files..save as dxf file.

4. Use Qcad to furthur manipulate dxf files.

5. Email final dxf files to Wyckam Canvas.

I'd upload the spreadsheet but can't find how to do it; and I only find one XLS file on the whole site on Slieve's public access page so perhaps loading an executable might be restricted. Contact me offline if you want the spreadsheet.

robert self

Arne - That is a very helpful comparison between boats and some insights that I had not considered.  The experience I've had with our current wishbone ketch rig is that reefing the aft sail is ok around 15kt of breeze when sailing upwind (although she is a bit under powered at that point), reefing the second sail above 20-25kt is a good idea if comfort is of interest. I've had both sails fully raised downwind in 25kt  and we did better than hull speed but it was also a too exciting for cruising.  At present the boat and  tanks are empty of most gear, water, or fuel (200 gallons water, 100 gallons diesel) and the anti fouling paint line is about 20 cm  above the water.  

Increasing the SA from the current 72.5 sqm to 85.4 sqm (118% increase) has me thinking that reefing is in my future.  As a matter of coincidence, dropping a panel in each JR sail gets the boat back to its original SA.  

I realize that on a JR the draft and camber are fixed while sailing.  A BM has sail controls such as cunningham (smart-pig), outhaul, backstay, or vang. Thus the struggle as to the amount of fixed camber to strive for in the JR design never mind how to get the camber.  Both your and Paul's comments on camber are helpful and encouraging.  Maybe there isn't a bad amount of camber, its just that one or the other may work better in different conditions boat, or the type of sailing preferred.

Arne - I have great admiration for the barrel method of making JR - it is simple, well tested, and easy to fabricate. And you have done a tremendous job of documenting your experience and providing clear and straightforward instructions on making the sails.  In looking at all the pros and cons of the various methods, I am currently trying to use the broad seaming method for panels 1-5 (bottom up numbering) and for six and seven am likely going to use rounding rather than broad seaming.  A factor driving the decision, other than what I've previously discussed, is space.  I think I would need space equal to the full panel size to properly lay out and loft the sail if I were to use either the barrel method or the shelf method.  When broadseaming, I just need the space to connect two adjacent panels - half as long.  In any case, it seems like a more  manageable job. 

Paul - your comments regarding the luff of the main not settling down sounds to me like it is being backwinded by the foresail.  On a BM that usually means the foresail is sheeted too far in relative to the main, or the main is too far out relative to the foresail. And in either case, a large amount of camber on the main would make things worse. I wonder if on a ketch or schooner, the proximity of the luff of the aft sail to the leech of the foresail could become an issue, too.  In any case, duly noted that for the main, moving the max chamber further aft, and possibly decreasing the amount of camber, may be good ideas.  

Erik,

now I have made some comparisons between your boat and Paul’s.

The Freedom 40 is quite long in the wl. (35’) for a given displacement of 9.1ton (metric). This has let you spread as much as 85.5sqm sail on her which gives a SA/disp=20.0 (or 9.4sqm/ton). The 35’wl. should give a hullspeed of 7.9 knots.

La Chica, at 31.5’ (LWL around 29.3’) is said to have a displacement of 14000-18000lbs. If I guess her to be 16000lbs, that would be 7.3ton. With her JR of 62.1sqm, her SA/disp = 16.8 (8.6sqm/ton). Her waterline of 29.3 should give a hullspeed of about 7.0 knots.

La Chica’s smaller rig clearly calls for maximum power from the sail, even at the cost of a couple of degrees pointing angle, so 12% camber makes sense. Your Freedom 40 on the other hand, could be said to be generously rigged. If she were mine, I would consider stopping at 8% camber. Just as with my smaller, lighter boats, this would save you from having to reef or un-reef between upwind and downwind legs. Besides, the 8% camber will probably let you point a little higher than the 12% sail.  Remember, in your longer, faster boat, the relative wind will be more on the nose than in a smaller, slower boat.

Cheers,
Arne

PS: From time to time I can read assumptions on these pages that the barrel cut method of producing camber is not as good as the other methods. Frankly, if performance and life expectancy is what we are looking for, then it remains to be proven that the barrel cut method is inferior. The recent photo of Ingeborg’s sail on my posting below also shows that the ugly “Johanna-wrinkles” along the battens are just about gone. The photo was even taken after I had eased the tension along the battens with about 4cm. The measured camber in Ingeborg’s sail is now 40-42cm, which gives a camber/chord=8.3-8.7%.

If one wants to make another step up on the performance ladder, I think Slieve McGalliard’s split JR is the way to go. As for me, I’m too lazy and content with what I have, so I don’t bother.

Both Alan Martiensien & myself use 12% camber in our foresails (boats are HM schooners) and it works very well for both of us. Alan has 9% in his main and I have 10% in my main... the mains could possibly be 8% as they need to be sheeted somewhat harder than the foresail. You never get the luff to completny settle. Possibly having max camber at 40% in the main might be better as well.