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This was kind of a fun project, driven by a lack of money and a desire to go sailing! I had looked at several sail options for my Navigator including having Duckworks make a set for me (about $800 if I remember right), putting together a Sailrite kit (about $500) or making a Polytarp sail. I pulled a bit of info from Dave Gray's website (hope you don't mind Dave!). He does a good job of laying out the process of cutting the sails and putting them together. The key questions I had were around how I get a reasonable shape to the sails, in terms of building in draft and placing the draft in the right place. Dave and other sources talk about building in draft by using edge curves, rather then cutting straight edge lines, and by using darts, or folds in the material.
The other "tool" I used was the spreadsheet that Thomas Hamernik put together, called "SailDart". This is a spreadsheet that has formulas built in that help you calculate the actual size of material you need to cut, taking into account the material needed for any darts you are building in. I think Thomas has this tool posted on the Duckworks site. Besides giving you the lengths you need, it graphs the sails for you, based on your inputs, so you get a visual of what you are trying to do. It took a little bit of playing around, but worked well! (thanks Thomas!!) I did have to convert the sailplan measurements from metric to standard (or visa versa) as the spreadsheet is in english standard.
Figuring out what "proper" draft and "edge curve" actually means:) was one of my big questions. I remember asking someone from the group for help with this and have a note in my files....I think this may have come from Thomas...it says...."
The point of maximum draft is often placed from 30-40% aft of the luff. This too, can vary, depending on rig design. I'm not sure if JW has any specific recommendations. Put it high enough to look right, but, too high, you'll lose effective area since the camber flattens out below the point of maximum draft. Don't forget to add edge curves. The luff on a lugsail can be slightly concave (curved inward) to help it set tightly. The head should have a bit of convex shape to offset yard flexing. The foot should be cut dead straight."
SO....some of this ended up being "what looks right!
For material, I ended up using Lumber wrap material. This is the stuff that you see wrapped around pallets of lumber being shipped by train, truck..etc.... It is a woven laminated, lightweight, tough and not nearly as crinkly as tyvek (which means it's not LOUD in the wind). It appears that different companies make this different ways. I went down to the local lumber store and told them what I was doing and asked if there were any extra sheets of this laying around. They helped me out by pulling some of the nicer sheets that had come off of lumber and they were saving to reuse...else I could have pulled what I wanted to out of their dumpster. This material has worked great..tough and hasn't stretched in a year and a half of sailing.
I cut the sail on the floor of our church fellowship hall...nice big flat surface!
Tools and materials were, weights for holding flat, marker, measuring tape, scissors, 100' poly rope 3/16", 3" vinyl tape (tarp tape)100', double back carpet tape 3" - 100', 3/8" grommets and 7/16" grommets....rubber mallet. Most tape companies suggest you use a mallet to help bond the tape to the material you are taping.
I think that was about it! (Check Dave's site for more details or just buy a kit from him with all the materials you need!)
Couple more notes: I did tear out the clew corner the first season because I didn't take enough care to reinforce. Sailrite sells plastic "jiffy head boards" which I added to the corners and has worked great. They're a few bucks a set. I also learned that you really do need battens for the main and mizzen. I made the batten pockets with vinyl tape put over a strip of the wrap material (ie:cut a strip of wrap material a little bigger then batten width, then taped that down on the sail to create a pocket. I used strips of Alaskan Yellow cedar for battens initially...then found some used fiberglass battens.
The sails do seem to work quite well, though I still question if they are quite as efficient as professionally made sails. I do plan on buying a real set..some day...I think : ).
Tim I
Navigator
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