Now that you have your sail block made and sail cloth at hand, it is time to the sail together. Before we go any further make sure that you cut the panels in the direction of the roll. Also, when putting panels together, alternate each with one curl up and the next down. This will neutralize the roll's curl along the leach. (For clear mica film, shiny side up first, next shiny side down).
If you want fullness, position the 40% draft locations at the forward part of the molding block. If flatter sails are wanted, move the 40% locations to the end of the block.
Now for the most important point of broad seaming. When laying down each panel and applying the seam tape, be very careful of tension. Tension causes puckers and that is not what you want in your sails!First Step: Lay the first panel on the molding block, (shiny side up for clear mica film). Don't try to follow the centerline with entire length of the panel's edge, see Fig. 1.
I use brown masking tape to keep the panels in place. It does not harm the panels and sticks well to the block. Here is the important part, when laying the panel down on the block, do just that, let the sail cloth lay easily. After you have the panel in place and got the first masking tape isstuck down, carefully stick the second masking tape without putting any tension on the panel.
Once done, you now put the double-faced basting tape in place. I use the Double-Faced Basting Tape made by Dritz. It can be found at most sewing stores. Again, lay the tape down on the first panel, along the block's centerline without any tension. Take your time and be sure you lay it straight. Any tension you put in these irst two steps will cause puckers. Note: the tape has a sticky side and a plastic strip on the other, use the sticky side first, see Fig 2.
The last step is placing the next panel on the first. To do so place the panel so it's middle section just covers the first panel. Again, take your time and like the first panel and tape don't put any tension when laying it on the block. Remember back a few issues when I wrote about making your sail block wide? It allows the sail cloth to lay down on the block by it's self, without effort. When you have this done, you will notice at each ends of both panels and how they arch and overlap. See Fig 3. That is what you want, your sail block has just put Camber in your sail.
Once the next panel is taped down (without tension), carefully pull the basting tape's top plastic strip off. When doing so, pull straight up. The top panel will naturally lay down on the basting tape. Carefully and softly, press down the top panel. Next take off the masking tape and check your work. If the job did not turn out right, un-stick and redo.
It should now be clear about the construction when putting panels together. If any part, the laying of the two panels and or the laying on the basting tape has ANY tension it will effect the quality of the job and sail. So think, take your time and practice first, it all matters.
After all panels have been put together it is time to check the total job. Tape the sail's head to the table and pull on the luff while holding the crew and tack. The sail should take on it's shape. If there are any wrinkles in the panels or in the seam, stop and fix. Do this by un-seaming the tape. If this can not be done, cut out the seam and go back to the block.
Next issue will be on sewing and finishing the work. It would be best if you practice putting panels together. This way you will get the feel, plus it saves on the cost.