Index of Entries, 3/25

  Find a topic of interest in the lefthand column and note the associated date (month/year), then click on the associated year in the righthand column, and you should find your chosen entry nearby.

Index of Blog Entries                      3/25

Putting the Pieces Together             3/25

New Kayak Design, Part 2              1/25

Creating a New Kayak                    12/24

A 'Leaner' Kayak                             12/24

 Boating is more Satisfying....          8/24

What is Next?                                   6/24

Careers and a Hobby                        6/24

A Smaller Kayak                              12/23

Finishing the Planked Hull                7/23

Rules for Developable Hull surfaces 6/23

Finalized kayak Design                      1/23

Starting a New Design: Kayak           1/23

Now I Have a Boat to Look at            8/22

Next Step in Design Evolution          11/21

A Real Sharpie                                    3/21

Another Guide Boat                            2/21

Finishing the Guide Boat                    12/20

Finishing the Planking                        5/20

Creating a Developable Surface         5/20

Solving the Hull Sheathing Conform. 4/20

Planking the Guide Boat                     9/19

Garboard Sheathing                            7/19

Viking Ship Museum, Hull Fairing     6/19

Defining the Shape                              3/19

Creating a Boat 'Skeleton'                    3/19

Starting to Cut Wood                            2/19

First Steps for the New Design            12/18

The Improved Guide Boat                   10/18

Getting Ready to Build                         7/17

Completed New Model                         9/16

New Design Model, Part II                   8/16

Creating a Model for a New Design     8/16

Beautiful Boats of Scandinavia             7/16

Vietnam Memories                                10/15

Along the Adriatic Coast                       10/15

Grand Tetons N.P. Boating                     8/15

Modified 'Next Boat' Design                  4/15

Sail Design                                              2/15

Next Boat?                                              12/14

A Day at the Lake                                    9/14

Resting on its Design Waterline              7/14

At Flaming Gorge, Utah                          7/14

What a Day!                                             5/14

The New Boat Looks Complete               3/14

Why I use Rosin Paper                             3/14

The Boat Windshield                                2/14

Winter Progress                                         2/14

A Voyage to Remember                             11/13

Instrument Panel                                        11/13

Now for the Accessories                            10/13

Sample Developable Design Calculation   7/13

To the Deck and Onward                            7/13

Slow but Steady Progress                           5/13

Finally, the Hull is Turned Over                 1/13

Hull Sheathing                                            7/12

The Origin of Boat Bowls                           4/12

Another Year, Another Boat                        4/12

First Season Report                                     9/11

A Trial Run                                                  6/11

Finally in the Water!                                    5/11

Out of the Shop                                            12/10

Ready to Leave the Shop                             10/10

Finishing the Stern, Onto the Windshield     7/10

Wood Decking                                               7/10

Interior Details                                               6/10

Finally, the Hull is Upright                            4/10

Planking the Hull                                          11/09

Initial Hull Sheathing                                      8/09

The Design Becomes a Reality                       5/09        

Hull Design Using Simple Mathematics       12/08

Design Evolution                                             7/07

New Direction                                                 7/07

Model Lobster Boat                                       11/06

Updated Drawings                                           9/06

Maiden Voyage                                                5/06

A Semi-planing Powerboat                              5/06

Guide Boat Pictures                                         5/06

Adirondack Guide Boat Concept                     5/06

A Real Disappointment                                    5/06

Panama Skiff                                                    5/06

Kayoe or Canak?                                              5/06

Where did this Unusual Interest Originate?     5/06

Putting the Pieces Together

Keel and frames temporarily clamped together, the start of a new kayak.

 For all of my earliest boat-building projects, I used plywood sheathing.  For recent builds, I have used no plywood.  Part of the reason is due to the type of boats I have recently taken an interest in.  Smaller boats tend to have sharper curvatures requiring narrower panels for sheathing:  Why not just use solid wood for these narrow panels?  When you sand solid wood, there is no concern about sanding through one of the plywood layers.

Using solid wood for the frames does require more joining of narrow boards, but it also provides better strength by aligning all the wood grain in the proper direction.  I use epoxy adhesive except for the laminated deck beams; there I use Titebond III.  In bonding the multiple layers of the curved beams, you expect to get 'squeeze-out' to ensure complete bonding.  Epoxy is messy and hard to clean up in such situations.  I have been using Titebond in limited applications for many years with no failures.  These underdeck beams will not be exposed to much moisture.

Next step is to create the stems for this hull.  I usually start with 2"X4" lumber for these pieces.  I want plenty of bonding area where everything ties together at the ends of the hull.

Creating the bow & stern stems will be my next project.

Stems are completed, ready to bond the sheer strip in place

All the pieces appear to be aligning quite nicely with no strongback required.

I used full deck beams for all frames.  That will allow me to size and place the cockpit wherever desired, although I already have decided except for details.  The stems look chunky now, but, when fairing, they will lose a lot of mass in beveling the ends.

All clamps removed.  We are looking at the framework from the stern.

With proper clamping, all pieces fit snuggly at the bow.  At this point, the hull is 158" x 25", but it will get bigger when the sheathing is complete.

I am adding one more longitudinal member to define the major chine, where the bottom and topsides come together.  It is not strictly required; the bottom is a single developable surface (beyond the keel), but the topsides consist of three separate projections blended together.

Bow stem prior to fairing.  Because the stems have a continuously changing bevel, it is best to fair the entrance angle after the piece is assembled into the frame.  I consider this step to be more sculpture than typical woodworking.  You have to do this in steps, frequently stopping and checking wood removal with a batten until it all blends together.

Bow stem after fairing.  The best tools for this are an angle grinder with 40-60 grit flap disc and a belt sander with a 60-grit belt.  I have a power plane, but it does not handle this 'sculpture' as well.  The exact bow taper is x/y/z = 14/3.6/1.

The stern stem is faired in the same way but with a slightly different angle due to its greater taper.  The next step was fairing together all the frame edges that make up the outside of the framework.  Routing a landing area at the edges of the plank keel, was the final step in preparation to start planking the hull.

Unfortunately, I was distracted, not focusing sufficiently, and gouged the keel in a couple of places when free handing the full-sized router used to make this rabbet.  The keel edge is curved near the ends (for about three feet) and the bevel is constantly changing, so 'free handing' is a requirement.  The router blade rotates clockwise.  If you pass the router from right to left along a board edge, the blade spins along that edge like a wheel, and things go smoothly with moderate wood removal and using multiple passes.  But, if you slide the router from left to right, the router tip can dig into the wood; you will not be able to hold it firmly enough, and a gouge results.  Why didn't I recognize that initially!  Yes, it is minor fixable, but still an impairment.

Now I start slicing planks.  Results will be delayed.  For the next 4-5 days, wet weather, including some snow, is predicted.  The cutting and planing produce ample sawdust which I would prefer to deal with outdoors.  My goal is for planks that will be 5.6 mm. (0.22") thick.

  

  

New Kayak design, Part 2

Topsides Projections 

The hull topsides shape is created by adding surface projections and secondary chines.  The goal is for the result to form a smooth curvature rather than the angularity of a single hard chine.  For this purpose, a parallel projection is used with a constant ratio between the changes in the x, y, and z dimensions.  The first projection will use the ratio x:y:z = 7:1.8:1.5.  All projections will be directed from the major chine toward the center section of the hull.  The second projection will use the ratio x:y:z = 7:1.8:3.5.  The third projection will be vertical in the z dimension with z=9 at the sheer line.  From this an entire table of offsets can be created listing offsets for all the frames above the major (initial) chine.

Where do these numbers for the projection come from?  The half angle at the bow is 0.9" increase in beam (y) in the first 3.5" of length (x). Because we are plotting length (x) at 7" intervals, we double the numbers: 1.8" increase in y for every 7" increase in x.  This ratio will give us the desired plumb bow.  Increments of height (z) vary as we go from keel to sheer:  keel is horizonal; deadrise is 0.5" increase in z for 1.8" increase in y up to the major chine; 1.5" per 1.8" increase in y in the first topsides projection, 3.5" in the second projection, and vertical in the third projection.  Together, these values help create a curved midships frame profile from the bottom to the sheer.

If we connect these points with straight lines, we have a faceted surface with five projections from centerline to sheer.  If we connect these points with a French curve or flexible batten, we can create a somewhat (the major chine does not completely blend in) smoothly rounded surface with the exactness of mathematical curves and projections.  Using narrow planks for sheathing the hull will preserve the rounded cross section.

Bottom Projections

Next, the offsets for the area below the major chine are developed.  For a narrow hull, like a kayak, a flat bottom, transitioning to a gradually steepening deadrise to provide both stability and a rounded cross-section is a good choice.  A flat plank keel is the starting point and the foundation for the entire boat.  However, if the keel is too wide, the hull will rock and pound in waves.  Laterally, on both sides of the keel will be a constant x:y:z slope of 7:1.8:0.5 (15.5 degrees deadrise).  All projections below the major chine will be directed toward the ends of the hull. 

This is a complete table of all the dimensions used to create the ten frames.  These are exact dimensions* resulting from projections from the major chine and the two additional chines for the topsides.  (*except for four numbers at the sheer obtained by graphic solution)

Stem Profiles

The next step in creating the new design is to project down from the major chine to the midline (y=0) to define the stem profiles, bow and stern.  Most of these numbers are not exact but can be calculated to whatever accuracy is desired (usually to 0.01" accuracy). The equations used for these calculations are listed. 

Plank Keel 

We can also calculate the offsets for the plank keel.  At my lumber source, I was able to get a plank about 10 feet long and 8 5/8 inches wide; then bought a second plank because the proposed keel would be about 140 inches long.  The original hull design was for a narrower 7.2" wide plank keel.  To take advantage of the additional width, I changed the projected distance from the major chine to the keel at the hull midpoint from 1.5" to 1.35" which is reflected in the table listed below.    

The bottom portion of the table above shows the calculations for the plank keel offsets.  The width (y) is the same fore and aft, but the length dimension, measured from bow and stern stems, is reduced by 20% for the stern portion.  As a check on calculations, intersections of frame dimensions at the keel should be consistent with the listed keel width at each "x" frame position.  Also, the "x" intersection of each stem profile with the keel should be consistent with the ends of the keel where y=0. 

Keel Rocker

It can be seen that we are designing the entire kayak with accurate numbers before starting building.  Only one more step to include:  It is recommended to include "rocker" (a slight upward curve) in the keel of our kayak for improved performance.  This will change the keel taper and length and induce a small change to the frame heights toward the ends of the hull.  I used keel rocker of 0.1", 0.4" and 0.9" over the 14" frame spacings toward both stems.  Total keel length will be 140.5 inches with the bow portion ending 9.3 inches short of the absolute stem and the stern section 7.7 inches short of the stern.

The numbers given are enough to build the entire kayak hull.  I already have the keel cut out and tapered.  Although using plywood cutouts for frames would have been easier, the frames are roughed out by half-lapping sections of solid wood on top of full-size patterns and bonding them together.  Much needs to be done to finish the frames, and work on the stems comes next.