Things I have learned

I am happy to report that I finished gluing the sheerstrake yesterday.  

The new techniques I tried in the hope of producing a sheerstrake worthy of finishing bright worked really well, although not quite well enough to achieve their intended purpose.  A couple of scarphs glued up with a bit too much glue line showing, and when I applied the quality test (i.e., what would the guys at Workshop on the Water   (WoW) think of my work?) I concluded that discretion is the better part of valor.  Thus, a nice contrasting paint color will be selected for the sheerstrake, sometime down the road.  


Speaking of the guys at WoW, in one of our frequent philosophical discussions, we reached the conclusion that by the third time you build a design, you will probably do a pretty decent job.  Never having done a glued plywood lapstrake hull before, and having learned an encyclopedia of things in the last six or eight months that I wish I had known going into the project, I agree with the "third time is a charm" rule.  Here, in no particular order, are some of the things I have learned:

• Scarphing plywood is tricky business, but unless you are in a position to buy and work with 24 foot sheets (they are obtainable,) you need to  do a lot of scarphing, and you need to get good at it.  While I have become a pretty good, and pretty fast scarpher, I learned that the conventional technique of planing to a feather edge doesn't work with plywood as well as it does with solid lumber.  You are probably better off ending your scarph with a couple of laminates intact and notching the inner edge of the scarph to that depth.  That way, you will have a very tight, straight glue line, and should you need to sand the completed scarph joint a bit, you won't risk going through the outer laminate of the plywood. 
• Speaking of sheet length, I opted for 4' x 8' sheets throughout the hull.  If I had it to do again, I would have ordered a sheet of 5' x 10'.  As noted previously, in the last three strakes, I exceeded the 23' total length that 3 sections made from 8' sheets (2 scarph joints per side) allow, and had to go to a 4th section (3 scarph joints per side) for each strake.  If I had used 2 8' sections and a 10' section on those three strakes, I could have completed the hull using only 2 scarph joints per side -- a significant time saver.   Obviously, this particular situation is peculiar to building a Grey Seal, but it is worth thinking about, regardless of the design, when building a plywood lapstrake hull.
• The spiling technique I used in laying out the sheerstrake, which I described in my  post "Logistics and boat building," using hot glued strips to fasten a lower batten and an upper batten together into a lattice, works much better than the spiling batten and compass technique I used previously.  I don't know why this is, but I consistently got perfect patterns with the lattice technique, whereas the planks done with the batten and compass frequently seemed to be curved too little.
• On my first several strakes, I determined the top edge of a new strake by measuring a constant 1 inch up from the bottom of the installed strake above it.  I found that doing this compounds any cutting or measurement errors  in the installed strake, by incorporating them into the top of the new strake.  A better technique is to measure up from the bottom mark of the new strake at each station using a strake width obtained from the 1/4 scale station drawing in the plans, and mark the strake.  (I made myself a spreadsheet showing the width of each strake at each station to use for this purpose.)  Then, clamp a full length batten along the marks, check for fairness, and mark the line, which will serve as the top edge of the land bevel as well as the top edge for spiling the new strake.
• The wooden clamp and wedge technique I started using when I did the sheerstrake not only makes a clean, hole-free job of gluing strakes, but also saves the time of removing the temporary screws and filling the holes left behind.  I had initially thought the clamps were too clumsy, and wouldn't give me a tight enough grip, but I am now a believer.
• The new director of WoW, Bruce, who started at the shop last week, is a highly experienced glued plywood clinker boatbuilder (where was he when I needed him?) I picked his brain about the difficulty scarphing plywood well enough to permit finishing it bright. Bruce advises using solid wood for parts that must be scarphed, if varnishing is the end objective (e.g., my sheerstrake.)  The cost would have been slightly higher, but the result would have been significantly better.

With a list like that, I guess I ought to be pretty humble by now.  In fact, I am.  Building a boat is a humbling activity for the amateur.  There is always something you could have done better, every step of the way.  All in all, though, I am very satisfied with my results so far.  The lines are reasonably fair, the sides are symmetrical, the glue joints look solid, and the measurements are very consistent with the plan drawings.  The errors and false steps I made along the way are ones I can live with, and served as learning opportunities for me, and perhaps for you as well.