Woorabinda Lake - Stirling South Australia

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SAIL MAKING - Creating Seams  
by Ben Morris (last edited 21/07/2013)

Shape in Sails Building Board Making Seams Set the Seam Curvature Making a Sail Sail Material Diagonal Seams etc Back to Intro page Setting the Sails The Claudio Tool Measuring Procedures


Using the Board to make a seam

Prior to using the board I have found it most convenient to mark it with a line across the two sections of the board with a line corresponding to the point of maximum curvature (originally 40% now 43%).  By marking the sail panels at the 40% (43%) point and lining these two up as in the first photo ensures the maximum curvature is at the correct location on the sail.  Alternatively or as well additional lines representing various fractions of the leading section and trailing section of the board  can be drawn and numbered in pairs such that the 40% (43%) line still applies.  That way spreading the material between two lines of the same number also ensure the point of maximum curvature is at the correct position.

  1. Place the correct lifting blocks under the front and rear edges of the board corresponding to the correct curvature.  Place the first piece of sail material on one side of board and secure with masking tape.  Place it so that the seam to be lies next to the opening between the the sections of the board


  2. Secure next piece of sail material on other half of board.  Overlap the gap between the boards and sufficient of the first piece of the sail to allow for a seam equal in width to the double sided tape being used to join the sail.


  3. Peel back one corner of the top sail material and temporarily secure down.  Apply the double sided tape to the lower sail section.  Do not peel back the protective layer yet!  It may be easier to add the masking tape before placing the second piece of sail material in place.  This makes it easier to see the amount of overlap required just to cover the tape.


  4. Add a diagonal piece of masking tape passing through the corner of the top sail section.  Peel back about 50 mm of protective layer and using the diagonal piece of tape lower the the top sail material onto the sticky surface.  A gentle tension on this tape will ensure the overlap is correct.  (It is too easy to get a 'soft' leech or luff if this tension is not applied.  A similar diagonal piece of tape must also be used at the other end of the seem.  Peel back the protective layer and use your hand to sweep the top sail over the lower to allow the sticky tape to do its job.


  5. Remove all of the protective layer from the double side sticky tape ensuring tension on the last diagonal tape.  Run your thumb along the join to ensure the adhesive is making contact with both sail surfaces.  Remove the tapes carefully.  This should produce a very smooth and accurate seem with the built in curvature defined by the board and its lifting blocks

  6. Rather than using masking tape to secure each sail panel to the board a much better idea is to spray the board surface with spray contact adhesive prior to using the board.  This holds each panel very securely yet allows the panels to be removed easily.  It particularly holds the middle part of the panel (near the 40% mark in the above picture) where slight movement here during the joining will vary the curvature quite significantly (thanks Lawrie)  As an alternative to having the spray over the whole board which will be very difficult to remove and replace later, lay a strip of double sided sticky tape on either side of the join across the whole board.  Remove the backing layer to leave a thin layer of adhesive right at the position that it is needed underneath the seam.  The stickiness off this adhesive will need to be reduced by repeated touching it with the heel of the hand a few times.  This is a much neater solution to the problem of holding the panels in position while the seam is being made.