Index of Entries, 9/25

 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                      9/25

Designing a New Hull Shape          9/25

What should I Build Next?              9/25

Planking the New Kayak                6/25

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

Designing a New Hull Shape

 The initial boat type, pictured in my mind, was of a slender canoe which could be paddled with a double-bladed paddle.  Speed was not a goal, reduced weight (no deck) and slightly more forgiving stability were the goals.  The first thing was to picture the midships cross section; a bottom slightly wider and flatter.  I 'played with numbers' in an equation, used to define the major chine.  I could alter the coefficients of X, Y, Z in parabolic equations to get the right length (X), width (Y), and upsweep (Z) that I was seeking.

Next, I needed to decide the X:Y:Z ratio in the bottom projection; get the midships deadrise desired with progressively steeper deadrise approaching the stems.  In order to achieve this, the major chine needed to be reconsidered.  Position and spacing of frames needed to be included as well as width of the keel.  

Creating the topsides is perhaps most critical.  At this point, I had to start over with all new numbers for the equation for the major chine; however, there were multiple choices/combinations to pick from.  Incorporating three more projections to create a more rounded topsides shape, I discovered, would result in a hull that was wider than desired.  I used a paper sketch to help decide the coefficients for my topside projections.  I had to choose a major chine equation with less beam (Y).  Iterative process, but I was making progress.

When I started to achieve harmony between all the equations and coefficients, I had more aspects to consider.  Just how slender do I want this hull to be?  What should the overall length be?  What should the sheer look like?  How much depth amidships?   Height at the stems?  Should I consider creating a transom at one end; should the hull shape be symmetrical or should one end be slightly more tapered?  But those factors are not requirements- they are choices to create the specific boat you want.

With the offsets already generated, I needed to make two more projections: first to see a lateral view of the stems and secondly to see the shape of the plank keel.  All offsets need to be charted on paper before I can visualize the result.  (Hey, all I use is a TI pocket calculator: no computer screen.)

Tomorrow, I hope to start making full-size paper patterns for the frames required, a little drafting practice.

     

What should I build next?

 When we were out on a lake recently with our kayaks, I noted that rarely was speed the goal when paddling; we were just poking around in the channels of a flooded forest in a reservoir backwater, seeing ducks, geese, and even eagles.  And I thought, "I could build a boat for that type of outing."

I have started sketching out the dimensions for such a boat:  I imagined: a bit shorter, wider, and more open, less decking in order to reduce weight.  Right now, I am considering a hull 156" long and 30" wide, but I still have more numbers to calculate and sketches to create.  I envision it as a double-ended-paddle canoe, but right now I only have numbers to look at.   

I don't see any making any further modifications to my latest kayak design/build.  It fits our uses well, but the joy and challenge of building another boat is still calling.  This could be my next project.

Planking the new kayak

 Sorry for lack of progress, but we have been busy (mainly traveling) for the past three months.  Now I am getting back to planking the new kayak design.  Starting from the keel, the first projection is comparatively wide, Thus, I used 2" wide planks for that section.  As the cross-sectional shapes start to include more curvature, I will switch to narrower planks.  Using no fasteners, many clamps are required to hold each plank in place while the epoxy adhesive cures.

A straight, full-length plank is placed butted alongside the keel, and its position is marked on all frames.  At the ends of the hull, a short plank is placed by hand, marked by hand with pencil, then removed and tapered to fit the open triangle between keel and full-length first plank.  It takes a small plane and some trial fitting.  A much smaller scrap of planking is similarly marked and adjusted to fill the remaining small space.  These pieces were then immersed in a bathtub overnight before being clamped in place to dry.  This is an area of maximum curvature, the soaking makes them more pliable when clamping requiring less force.

The first full-length plank has been placed port and starboard, and the second plank has been clamped in place for a trial fit.  The planks may look straight at first glance, but almost every plank has a slight curve which needs to be accommodated or removed using a small plane.  There will be one scarph joint per side.

These are full length, straight planks.  As you see, the planks are already reaching sheer height.  Following planks will be tapered and less than full hull length.  I do cleanup frequently, light sanding, knocking off resin blebs, vacuuming, so that I can make a better assessment of progress and note any flaws to be corrected.

Creating and fitting these tapered-less-than-full-length planks is exacting.  Each one requires a scarph joint.  Each plank about 11 feet long by 1 1/2 inches wide and with slight curvatures instead of being truly straight.  This is definitely not for the beginner boat builder or anyone with limited patience.  Then you must wrap each plank around the ever-changing frame curvatures and come out with consistent results.

Soon, the hull will be sheathed up to the sheer level, and I will post some new photographs.  Planking the deck should be much easier, but the inside of the hull needs to be finished prior to decking.

Before I start on the deck, I really need to finish the hull interior (while I have access), and perhaps I should finish the hull bottom.  The bottom sequence will be to sand any gross high points, do a penetrating coat of unfilled epoxy, then sand lightly, then a fill coat of epoxy slurry for any low points, and finally sand in preparation for primer and a final paint job.

  

The view is from the starboard side of the stern.  If you look closely, you can see that there are three partial length planks which taper to a point short of the stern (also short of the bow).  With somewhat straight planks and a changing bevel to the topside frames, this is what you get.  Some clamps are present because that final tapered plank has not been bonded yet and is held in place only by the clamps.

The hull has now been sanded with an orbital sander and 60-grit discs.  I am waiting on varnish ordered from Amazon.com; Colorado has no dedicated marine supply stores.  I need to varnish the hull interior before beginning the deck.  No new photos because the sanding does not alter the hull sufficiently for much of a visual difference. 

I now have three coats of varnish on the hull interior, and the first decking plank has been bonded, port and starboard.  "The decking planks should be a comparatively quick task.  It is just a matter of trimming the ends."  Fitting the cockpit edging will be slightly more difficult. 

Contrasting planks, light/dark, planks many of which are only resting in place.  Cockpit edging also passively placed.  As I work towards the centerline, access to the underside of the deck becomes very limited.

What I wrote above is wrong:  Fitting the deck planks is an exacting task.  Those planks, as initially cut, have variations (mainly curves) which need to be accommodated.  If you plane the planks until they are truly straight, they may end up being noticeably narrower.  The deck is highly visible, and the boards have to appear uniform and centered.  The centerline reference constantly needs to be rechecked.  I spent time planing boards to get what was needed.  Anything more than about 1/4-inch variation stands out.  Joints need to be tight, but not so tight that resin is excluded.  I can't have resin-filled gaps showing with exposed wood grain.

All those loose planks were trimmed, epoxy was applied, and they were all set in place in one session.  I used bricks for weight to hold the planks in place.  What you see here is after further trimming and sanding.  Using bricks seemed like a risky method, but the result looks good.

The deck does not look as good as it should.... my fault.  I used too coarse sandpaper and did some cross-grain sanding which left scratches in the wood.  The first coat of varnish really made those scratches stand out.  I was too impatient.

I probably have 2-3 more coats of varnish to apply.  Then, I turn the hull over and start painting.  The blue stripe is painters' tape.  Should I paint the hull blue/gray with a white stripe (where the tape is), or reverse it? These are the colors I have on hand.  The completed hull weighs 46 pounds; not light, but it is size, not weight, that makes it awkward to handle.  The frame with keel, prior to planking, weighed 17 pounds.  I think that I prefer a more rugged hull rather than a lighter but more delicate hull.
  

Having all the right tools is such a blessing.  When on active military duty (moving often)), I had a very limited tool set.  Now I have a well-equipped shop; no fancy tools, but a variety of modest tools that can get the job done.    

 

Final finish, and I am happy with it.  In places, I was impatient, and the finish could have been better, but the design looks good.  Visitors have said, "Why don't you build these to sell?"  I expect that I will be selling the oldest one, but only to make space for new projects.  We are going to be busy traveling for much of the next year, so I can't put a time schedule on a future boat project.

We took my two completed kayaks out to a local lake recently, along with another couple who brought their own plastic kayaks.  There were wind and active powerboats (wakes) on the lake, and these kayaks handled everything okay.      

At this point, I am pleased with all the dimensions/ proportions chosen for this project. I am wondering if my use of a slightly wider keel plank will noticeably increase hull stability. 

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 and 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.

We have been gone for the past seven weeks.  Now we are in full Spring mode, although some rain in the weather forecast.  Hopefully, I can get back to this boat project soon.

  

  

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.

   

Creating a new kayak, establishing dimensions and offsets

 General Considerations

My goal was a nice-looking kayak for safe general use on lakes.  Something better than the plastic sit-on-top hulls at the sporting goods stores, but less demanding than the long narrow high-performance kayaks.  The plastic hulls are generally about 12 feet long or less and 30 inches wide or more.  High performance means a hull closer to 20 inches wide.  Most light duty trailer descriptions state "for hulls up to 14 feet long".  This provided general parameters for my design:  12 to 14 feet long and 25-30 inches wide.  Displacement is a tradeoff between length, width, and depth.  Displacement at a 4-inch waterline is often used as a reference level.

The first step in design for me is to mathematically describe a midships cross section and the initial (major) chine.  I chose a maximum half-width of 9 inches at the chine; curvature extending upward to the sheer would add about 4 inches to those 9 inches, resulting in a total overall beam of about 26 inches.  Generally, the bow of a kayak has a finer entry angle than the stern exit angle; thus, bow and stern are calculated separately.  Working with thin wooden planks, frames need to be spaced about 15 inches apart or less to provide fair curvature without unplanned deflection.  I always create a table of dimensions for length using twice as many exact points as planned frames to ensure exactness.  Also, the end of each calculated curve should include a short straight section with no further curvature because there is no lever to exert torque at the end point.  X denotes length starting from the bow.  Y denotes width starting from the midline of the hull.  Z denotes height starting from the initial plank keel position. 

Starting Calculations, the Major Chine  

Creating fair curves is simple; most useful is the trajectory curve, also called 'parabolic'.  Divide the curve into as many equal sections as you need to provide adequately spaced offsets while also considering the total offset required.  In this case, I chose 9 sections (each 7 inches long) with an offset increment: 0.1 inches.  At the starting point (0) the offset is 9 inches, full width amidships. At the next point (1) the offset is 0.1", reducing beam to 8.9 inches.  Next point (2) has an offset reduced by 2 squared (4) for a beam of 8.6".  Next point (3) has an offset reduced by 3 squared (9) increments for a beam of 8.1".  At each section, the beam is further reduced by the square of the section number.  At the end of the curve, the initial beam has been reduced by 0.1" multiplied by 81 for a resulting beam of 0.9".  At this point, a short section without further bend is added, 0.9" width Y and 3.5" length X of straight line.

Each of those numbers are exact.  This major chine is the basis for all projections above and below.  Yes, there are many numbers, but this provides close-spaced points of projection so that when you 'connect the dots' when drawing frames, stem profiles, and plank keel plan view you have adequate accuracy.  This is about twice the number of dimensions that I will actually use, but the additional accuracy is there if needed.

The angle of this short segment can easily be calculated as twice the total offset of the curve divided by the length of the curve.  For the bow section of this design, I used a total curve offset of 8.1 inches and a total curve length of 63 inches.  (8.1 X 2)/63= 0.2571 (a 14.4-degree half angle).   0.9 inches divided by 0.2571 equals 3.5 inches, resulting in a total length of 66.5 inches.  The initial chine curve needs to curve upward as well as in width to provide a proper bow profile.  For this, the same curve length is used but with an offset increment of 0.08 inches resulting in a total offset of 7.73".  The planned height, keel to sheer is 9 inches.  Curved deck beams will add to the hull interior height.

For the stern section, the sequence is similar except that the exit angle, and curve leading to it does not need to be as fine.  This is done by reducing the curve length (by 20%) while using the same total offset.  Instead of 3.5-inch sections, 2.8-inch length sections are used.  Five of these sections totals 14 inches.  The frame spacing will be every 14 inches both forward and aft.  Half angle at the stern will be 17.8 degrees.

Next, we start to develop the midships cross-section curvature and determine the parallel projections used to create the entire topsides.

(This entry is done in conjunction with the actual design and construction of a kayak.  To be continued.  I will try to add some diagrams for clarification.)