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.

   

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.)   

                 

A leaner kayak

 While I am still adding varnish coats to the new deck of my current kayak, I am already thinking ahead.  The plan is to add a blue/gray stripe at the sheer on my kayak's white hull and then add a white stripe on my wife's blue/gray kayak hull.  Aesthetic touches to make the two boats coordinate more closely.

But I also have an idea for a new modified kayak hull.  With minor changes to the current offsets, I want to produce a hull 159 inches long by 25 3/4 inches wide with almost the same height (depth?) as our current kayaks, not drastically different, just slightly 'leaner' than what we already have.  It should be lighter and more cartoppable.  Every time I design and build something, I am always asking how it could be improved.  These are not meant to be high performance kayaks, just nice looking and functional.

I already have outline drawings for the ten frames, plank keel, and two stems that will be needed.  The most critical piece of lumber is the plank keel.  Looking for a plank about 9 inches wide, 11 1/2 feet long, and 1/2 inch thick was asking a lot.  Couldn't find what I wanted in one piece, so I bought two shorter planks and will scarph them together to get what I want. Anything thicker than 1/2 inch will add extra weight and be more difficult to bend for the keel rocker.  I plan to plane it down to 0.4-inch thickness.  

The culmination of my previous project.  I had to rebuild that trailer and replace the deck on the more distant kayak hull in the photo.  Yes, that is snow outside.

 

You may notice the previous kayak deck lying on the floor on the right side of this photo.  I can't think of any use for it; probably will end up cutting it into pieces for trash pickup.  The price of progress; the new deck is better looking.

I am going to start a new blog entry.  I discovered that the new 'leaner' design requires more than a minor change in my table of offsets.  Also, I want to explain (to remind myself) just how all those dimensions are obtained.

Boating is more Satisfying when the Boat is your own Design

 

I designed and built this 18.5-foot-long runabout which was completed in 2014.  Size-wise, it has ample space for up to six people.  The 75 HP engine is good for about 35 MPH, although altitude, load, prop pitch, and even wind resistance can be factors.  Someday, I would like to run it at low altitude to see how much more speed might be attained.  It is light and easy to tow, due to the wood/epoxy construction, which is important because here in Colorado there are very few nearby lakes.  We have towed it as far away as Coeur d' Alene, Idaho.   Being light also means that it takes less horsepower to move it through the water, and it is very fuel efficient.  The only drawback to being light is that when maneuvering for retrieval to its trailer on a windy day, wind can push it off course when at idling speed.

Behind my runabout in the above photo, "Mountain Dancer", the larger green and white boat is my brother's 27-foot Sea Ray cruiser.  It is ocean-capable and has twin engines totaling about 450 HP.  

This past weekend, we ran the boat on Ruedi Reservoir (7,800' elevation), near Aspen, Colorado.  The weather was perfect except for an uptick in wind speed during retrieval of the boat.  The weather this past weekend was unpredictable with quick shifts between sun and clouds or rain.  Fortunately, everyone did their part to properly position the boat and trailer.  The dock at Ruedi is pathetically small which didn't allow much space for handling of the docking lines.

A few years ago, when my brother, Jay, and I both had our boats on Jackson Lake, Grand Teton NP, his wife, Connie, made a short video of my runabout on the lake.  The scenery there is spectacular, and you can see the runabout moving smoothly across the lake's surface.  If we are lucky, you may be able to view this video on YouTube at the following address:

 https://youtu.be/X1m7WiJS7S8

                  

We have the full canvas enclosure for our runabout in case of bad weather or the rare choice to sleep aboard.

What is Next?

 I sold two rowboats boats this week, helping to clear out the shop.  I have one more that I want to sell. (Now sold to a gentleman in California; he drove here to get it.)  If you have been following my blog, you can see that as I build a design, I am always asking "What could I do better?"  Then the next build incorporates those changes.  The boats I am letting go are perfectly adequate but have been replaced with slight improvements, sometimes with only aesthetic differences.  And I am at a point where few new improvements come to mind on my rowboats.  A sailboat would be a different project, but the Colorado mountains might not be a good place for consistent winds and sailing.  

I have been looking for the proper trailer for transport.  I finally located one, but it needs work (23 years old) and modification; it had been set up for hauling bicycles.  I bought it; used boat-type trailers are hard to find in Colorado, especially light duty.  I have replaced the tires, inner tubes, bearings, and axles.  I exchanged its setup for bicycles with a 5 1/2' by 5 1/2' deck for small boats.  Next project:  I have discovered that not all the trailer lights work.  The wiring is old (obviously) and not well protected.

I need to get out on a lake with my newest boats; that use may suggest further improvements.  The boating season at the altitudes where we live, 7000+ feet, is only about six months long, making for a limited opportunity on our lakes. 

The blue/gray kayak was my first recent design attempt.  The natural finish on the second kayak is a design for my wife.  I already have ideas for an improved design to slightly reduce width and weight.

 

This trailer came with a short tongue and a long tongue.  I attach the short tongue for use while in the shop.  The trailer (a commercial build from California) has coil spring suspension and motorcycle-type tires.  New tires are not easily found, but I was able to get some off Ebay.com.

I had a contractor come by to look at some home repairs.  When he spotted my boats, that is what he wanted to talk about.  He told me to call him when I get ready to sell the next one.  My most recent sale was for $400.  The gentleman from California told me I am underpricing my boats.  1) Colorado is a boating desert.  There are few buyers here.  2)  Mostly, I care for an appreciative home for these boats.  Each one is a unique design and product.

UPDATE: With everything completed, we got out on a local reservoir today, and I learned some lessons about kayaks compared to guide boats.  My guide boats have a steeper deadrise but are more stable, not just due to the slightly wider waterline beam but also due to having two oars in the water instead of one paddle blade.  Two oars also make for quicker turns, but the kayaks had good directional tracking when paddling.

While we were out on the lake, at 9,000' altitude, the wind increased in gusts, and I gained appreciation for the influence of increased freeboard.  As the wind became stronger, it shifted, and we realized that we would be paddling to windward to get back to the launch area.  Those of you familiar with kayak design can laugh and shake your head at this amateur (me) making mistakes instead of using a proven design.  For me, it is just another project which I can fix.    

How to fix the kayak with excess freeboard?  Why you simply take a circular saw and cut around the topsides about three inches lower than the original height.  Then you replace the deck beams and start planking the new deck.

  I am putting a new lower deck on a previous kayak hull.  I like the results using solid lumber rather than plywood; it allows more creativity.  However, it does take more work, not so much in bonding the planks in place, but in individually fitting the planks.  Beyond knots, cracks, or any other defect, almost no plank is ever straight.  Thus, each plank must be fit into place.  Edge-setting 2" wide planks is not reliable, and I do not want to perpetuate existing variations.  I start by marking any convexity/ concavity in the plank shape.  Adjacent planks must have the same shape with imperceptible curves.  I have straight edges (2', 4', 6') for checking and multiple planes for adjustments.  The deck will be 15 planks wide with the last plank centered on the midline.  All planks are bonded edgewise with epoxy as well as being bonded to the deck beams and sheer. 

The new cockpit will be tapered forward, similar to the shape for my wife's kayak.

All bonding completed.  All that is left to be done are sanding, varnish, and paint.  The curve used for the forward part of the cockpit is from the same curve form used for the deck beams.