First steps for the new design

Today I modified the previous drawings for the 14 guide boat frames (2 each of 7 different shapes) and made an estimate of how much lumber will be required.  I want the frames to be 1/2" thick and will need some 1" to 2" wide pieces to bond and trim into the required shapes.  I already have a 12' x 7 1/4" x 1/2" beautiful piece for the plank keel which required some careful trimming to remove a slight curve.  My full-size drawings of the frames, keel ends, and plank keel were made on rosin paper.  I like that the rosin paper comes in three-foot wide rolls and is fairly strong and stiff.  I think I may want something even stiffer when I make patterns for the planking.  I just discovered a new candidate for patterns- Ram Board, it is stiffer, smoother, and has a lighter color (so pencil lines show up better), but it is also more expensive.

Once I get the frames almost done, I will be looking for material for the ends and for the battens at chines and sheer.  Sheathing decision will wait; I can always use thin plywood, but would like to incorporate some solid but thin planking.  I just need to see what will take the required curvatures.  With developable hull surfaces, many options exist for sheathing it.

Below is a print out of the essential dimensions for a slightly revised guide boat.  The previous published dimensions will produce a good result with a few less details, but I made a small revision, creating one more chine, to create a smoother, more refined, visual shape.

The blemish on the photo is due to an internal "floater" in the camera.  The numbers are still legible, but I may be looking for a new camera.

Below is a drawing of several stations in the series of cross-sectional frames for the new hull shape.  As you can see, adding an additional chine allows a more rounded hull shape.

One of the advantages of this design is the low seating position it provides; occupants are seated very close to the level of the 4" waterline.  This provides great ultimate stability.  The level of the oarlocks has to be coordinated with the level of seating; thus, the low seating position also facilitates less required freeboard and a lighter hull .  I have started cutting out pieces for the future frames but won't post an pictures until things start being joined together.

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 wgrabow.blogspot.com)  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.