I made it at TechShop
Step 1: Cut up the existing cover
To start with I noted down where all the snaps and fasteners are in a notebook and tried to note as well as possible how the parts went together, especially in the areas that go around the shrouds and mast.
After that I used a seamripper to separate all the pieces. For this design, all the small pieces are rectangular strips. There are really only 3 main pieces that need to have patterns made.
Step 2: Make patterns
I used the workspace at TechShop Detroit to lay everything out to trace the patterns. The longer piece of this cover is 15 feet long and quite awkward to work around in a small home workshop.
Step 3: Cut the large pieces
Lay the patterns onto the canvas and trace them out. For marking on navy colored canvas I found the best thing was a "jelly" white permanent ball point pen I found at Micheal's arts and crafts. I have had no luck trying to use a soapstone pen which is always the recommended tool for this. The generic canvas usually has a top and bottom with one side coated so you need to be careful putting your patterns down so that the coated side is facing inwards in your finished product.
Cut out the pieces using a pair of high quality scissors from a sewing supply store. Your hands will thank you verses using a set of cheapy scissors from Walmart. The material cut will be cleaner and take longer to fray.
Step 4: Sew it together
For sewing this you can use the Industrial Straight Stitch or Walking Foot machine available at TechShop. I used a home heavy duty single stitch machine. It is borderline adequate for this job. A normal home machine will not work. Use a quality 18-20 size needle or you will be bending or breaking the needle constantly.
Sew the 3 main pieces together first.
Use a technique after sewing the first time called "top stiching" which is where you hold the seam down and sew back over it again.
From there I sewed the bow and shroud snap edges. These are rectangular pieecs that are folded in half so that they are too layer and then sewed to the appropriate seem on the main pieces. Cut all the rectangular pieces extra long by 7 or 8 inches. Sew them on 90% of the way. Stop and fold and cut the excess off the rectangular piece, sew that seam and then finish sewing it to the main piece. This allows you to be much less precise with cutting out the smaller pieces and also allows you to not be super accurate when sewing around curved seams.
I sewed the 2 zipper flap edges on. These are also again rectangles that are folded in half so they are double layer and sewn to the main pieces.
Sew the zipper on. I use YKK zippers available from sailrite. In this case a 2 foot long fixed length locking zipper. Pay attention to make sure your zipper will be able to zip after you install it. I try to keep stitching around an 1/8 to 1/4 inch from the edge. If you get any closer to the zipper it may be difficult to zip it later on. When sewing on the zipper side with the pull, sew 5 or 6 inches of the zipper, you can then bury the needle, lift up the foot and you can pass the zipper pull under the foot to the area you've sewn already and then sew the remainder of the zipper on.
Sew the edge skirting on. These are very long pieces. The bow sections in this case are 9 feet by 9 inches and the stern sections are 12 feet by 9 inches. For each of these I made a sub assembly by flipping the bottom seam up and sewing it and then sewing the 2 sides over. Sew these onto the main pieces. They will all be a foot or so too long. Shorten as we did for the other smaller rectangular parts.
Sew a bungee cord into the bottom skirt. I used 1/4 inch bungee cord from Sailrite for this with bungee hooks and stainless steel rings. To start with you can sew one continuous piece into the bottom of the skirt. I folded the bottom skirt up about 2 inches to make the pocket for the bungee.
Sew some small reinforcement pieces into the rear corners. This will help keep the corners of the boat from wearing through.
Sew a reinforcement under the middle of the cover. This will be used to hold the cover up using a halyard so that water will flow off of it and not puddle on the boat. Sew a small piece of webbing onto the top in this area to clip the halyard too.
Sew a small piece of velcro to the strip going around the mast.
At this point you are finished with sewing and it's time to finish the bungee and add snaps
Step 5: Finish the bungee
You will need to split the bungee at the bow and the 2 side shrouds. At each of these use a bungee hook on one end and tie a bungee ring onto the other end. Leave some extra bungee in all of these areas for now. You can tie more tension into the rings after the next step.
Step 6: Add snaps
Add snaps at each shroud, at the mast and above and below the zipper. I used snaps available from Sailrite along with the tool to attach them. The tool is a small metal die and tap that you use to smash them in like rivets. There is an inexpensive plier like tool available from West Marine to attach these. It doesn't work well, don't waste your money on it. Either use the hammer tool or spend a lot to get the sailrite tool that looks like a large set of vice grips.
Put a snap on the skirt where the bungee exists each part of the skirt. Put the snap as close to the bungee as possible. This will prevent the bungee hooks and rings from sliding into the skirt. After this you can tie the bungee cord so there is more tension.