Monday, January 9, 2017

Stack Pack, Step I: Thinking

 It's cold outside.

Eolian sits in her slip, double-tied and with our additional "winter fenders" as prevention against the winter storms, with temperatures in the 20's, 30's and 40's and winds the same.  It is a time for dreaming, for planning.  (Well, except for the occasional repair, like the lazarette drainage problem which I'll write about some time...).

So what am I thinking about?  I'm designing, in my head, a stack pack sail cover for our mizzen.  I like to have the whole of a project firmly understood, run thru completely in my head...  before I start.  There are always surprises, but this minimizes them.

Why the sail cover?  First, our existing sail cover is shot.  It will make it thru this winter, but the next one is doubtful.  So some kind of sail cover is called for.  But why a stack pack?  I assure you, this not a fashion statement - there is a sound design reason.  Eolian's mizzen boom extends well beyond the stern rail:

Can you imagine putting on a conventional sail cover?  How would you do it?  Well, what this 69-year old man has to do is stand on the stern rail, wrap his right arm over the boom, and with only his left hand reach waaay out there to the end of the boom and single-handedly make up the three Common Sense fasteners on the cover at the end of the boom.  I haven't fallen in the water yet.  Yet.  But my right shoulder has been giving me some trouble of late, and so I can see the end of this procedure coming...  A stack pack solves the "dangling old man" problem.

A stack pack is supported by lazy jacks, which I installed last fall as the first step in this process.  This brings us to the first design issue:  how to actually support the cover with the lazy jack lines.  You might think that this was a "solved" problem.  Not so, by any means.  A walk down E dock showed this:
1. Lazy jacks attached to short straps sewn to the cover

2. Lazy jacks attached directly to the batten thru a grommet in the cover.  Note that there is no provision for adjustment of the lazy jack leg length

3. Openings cut in the batten support tube and lazy jacks tied to the batten

4. Lazy jacks attached to full-length straps sewn to the cover

All of these sail covers were professionally made; all are different.  In each case, I find something that is objectionable:
  • Two sail covers, examples 1 and 4, have the jack lines attach to straps;  the batten provides no vertical support.  Consequently the cover "drapes" around the straps.  Example 4 provides far better support for the cover fabric than does example 1.
  • Example 2 has the jack lines supporting the batten directly, but because of the single grommet hole, there is only a line entry.  I conclude that the line is terminated on the batten internally.  That must mean that there is no provision for adjustment of the jack line lengths.
  • Example 3 also has the jack line support going directly to the batten.  In this case, the lines are tied around the batten which gives good shape to the cover (as in example 2).  However, all jack lines have a forward component to their pull.  As you can see, this has caused the attachment to slide forward against the opening of the fabric and will eventually cause a chafing problem there.

I have decided to use a variation of example 3.  In my case, I will drill a hole in the batten (sched 40 PVC pipe), and pass the jack line end thru that hole.  This fixes its location on the batten and yet provides for adjustment of the jack line length.

In order to make those openings in the cover to admit the jack lines, I will make the cover sides of two pieces of fabric: a side and a top.  If it were a single piece, sewn to make a loop or pocket for the batten (as for example, in the Sailrite design), cutting and finishing the openings out in the middle of a large piece of fabric would be very difficult.  In addition, if the top edge of the sail cover is to have any curve at all (a curved sheer is always more graceful than a straight one...), then the side of the cover and the top must be made of two separate pieces of fabric.

I think I have the seaming details worked out:
  • Cut out the fabric pieces, and then for each side of the cover:
  • Cut out the jack line openings in the top edge of the side piece.
  • Apply finishing binding to the edges of the cut out openings
  • Sew the top surface to the side surface at the top edges, wrong sides together
  • Make a loop or pocket with the stitched seam folding it back against the side piece, leaving sufficient room to slide in the batten pipe.  Stitch it down.
  • Done properly, this should provide lazy jack openings which are finished on all but the bottom edge; the bottom edge is formed by the seam between the side and the top.

See what I mean by "thinking it out?"

OK, now I have to think about the forward and aft ends of the cover and what they will look like...


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