Sunday, October 14, 2018

The improved guide boat.

Sorry for the lack of recent entries on this blog,but instead of building boats, we have been planning and traveling on vacations.  (Those trips, if interested, are documented at  But I still have the "itch" to build a boat.  I completed plans for a new powerboat, but have no justifiable reason to exchange a new boat for the one we already have.... and a new build is expensive to fit out.  I have always liked the simple, continuous curvature of the faux guideboat I built almost twenty years ago.  I built it in a basement using hand tools.  The cost was low, and it has performed well.  However, every time I design and build a boat, I keep evaluating how it could be improved.  Thus, recently I dug out the plans for my previous guideboat and altered the plans to include improvements based on experience.

The previous hull was designed for maximum portability; light and compact.  See my previous entry "Guideboat pictures" to get an idea of the hull shape.  One person can manage cartop loading of the hull, but two are obviously more convenient.  It is not the weight, but the size that is awkward.  On the new design I added 6" length, 3.2 " width, and 1.8" in depth.  I changed projections for this developable design to reduce localized curvature (making it easier to sheath) and reduced the number of frames (spacing at 12" instead of the previous 9").  The hull can easily be built with increased length if desired by re-spacing the frames and adjusting the stem and keel profiles (or adding a parallel segment midships using the X=90" offsets), but 15' was chosen as a convenient length.  All dimensions are mathematically exact forming perfectly fair curves.  Dimensions are for a lines plan, to the inside of planking; add about 1" to width and 2-3" to length for the finished boat.

I used 4mm ply for sheathing on the previous hull which has functioned okay but seemed kind of flimsy when building, hence the 9" spacing of frames.  I will look for better plywood or solid wood sheathing for the next build.  The only real area of difficulty will be to sheath the pronounced curvature at the keel ends of the hull.  The plank keel is sized for use of easily obtainable nominal 1" x 8" lumber. Final overall dimensions will be about 15' 2" by 44" with amidship depth of 14" and a height of 23" at the ends.

At the 4" waterline, the hull is only about 30" wide which makes for an easily-driven hull.  Although tippy when you first get in, the low seating position and flare of the sides creates impressive ultimate stability.  That flare and the fine ends make for a dry and buoyant ride in waves.  The straight keel causes it to track well, and counterbalanced 8' oars provide good leverage for maneuvering.  These are all qualities inherited from the original guide boats.  The above-waterline beam I have added creates a more efficient rowing arrangement. 

I intend this to be very much a spare time project; so the start will not be immediate and progress will be slow.  I'll post more photos when I get time.  A typed, complete compilation of dimensions is posted below to aid others to build a similar boat if interested.  The dimensions are listed for only 1/2 of the hull length since both ends are symmetrical.  X= length from stem; Y= beam from center line; Z= height from keel base.

While on vacation, I had time to think about this project and decided on an additional "improvement".  By creating just one more chine, the cross section shape of the hull becomes more smoothly-rounded to the point where you can describe it as a true planked guide boat and not just a plywood semi-replica.  Each plank is roughly 3" wide.  Just home from our trip, I will be busy for the next week or so, but, as an addictive hobby, I will be providing more detail in few days.  Eager to get started.