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What to Build?

The Need


It all seems simple, doesn’t it?  You’re going to head out across the water and you need some sort of boat.  As long as it will get you there it doesn’t have to be big or broad or beautiful.  It just needs to be sufficiently seaworthy to rest your mind a little.  Ah, but what a deceptive word: seaworthy.  At the end of the day, seaworthy is all about safety and comfort is not a big part of the equation.

The open ocean is where seaworthiness is truly tested and this voyage in Kobuk will not involve much of that.  Ocean passages are there waiting to be done, but they will be in the tropics where temperatures are warm and storms are few and they will be day passages between islands or coastal ports where the chance of getting caught in adverse conditions is less than on a lengthy ocean crossing.  It still can happen but it is less likely to happen and if it does there is some reason to hope that you can make emergency radio contact with someone helpful or that other boats will be passing by.  All in all, getting on a boat is a risk, but life-threatening risks are less on rivers and in coastal waters than they are hundreds of miles from land.  All of this is justification for selecting a boat that cannot claim to be seaworthy in the eyes of the master mariner who knows the ferocity of the open sea.  In short, Kobuk is held to different standards of seaworthiness than those expected by Joshua Slocum of Spray or Harry Pidgeon of Islander.

 About half the projected voyage will be on fresh water where sensible and accurate navigation is far more critical than hull sturdiness or astute boat handling.  The first line of defense will be caution—and especially navigational caution.  The biggest risks are likely to be unpredictable currents, submerged hazards, nasty lake chop, and sudden microbursts—all of which have the ability to do Kobuk in but none of which need be deadly if speed and course are chosen by a timid person.

 At the other end of the spectrum, Kobuk will be expected to spend about fifteen percent of her time doing ocean passages where the risk of an open boat getting swamped is somewhat magnified.  It is also a time when Kobuk will need to run an adaptive course, avoiding direct strikes against lumpy water and generally seeking out the path of least abuse.  These concerns must weigh in the choice of a boat design, but the compromise should be one in which the final product handles well on the inland waters and behaves merely tolerably on the open sea.

 Every boat design is a compromise, of course, so the grander task is to know the strengths and weaknesses and steer the final product clear of the latter.  If you have a dear friend who finds it hard to tell the truth about anything having to do with money, it is best to avoid that particular topic if you are looking for the truth.  So too with a boat: if she doesn’t like to see waves climbing up her stern you look for ways to keep her clear of that particular situation.

 When I started looking for a design for Kobuk I was most concerned with finding something that would be (1) cheap and easy to build, (2) small enough to be handled by a single person, (3) capable of operating in shallows, and (4) sufficiently sturdy to ride out rough water.  These are the things I worried about most, and I generally worried about them in the specified order.  Fortunately, the first two are not incompatible.  Every foot of additional boat length would, I knew, astronomically increase the cost of construction and the total time needed to do the building.  Enthusiasm declines with age and so when in my early fifties I decided to take on this project I no longer had a compulsion to undertake something grand.  A small, simple boat would do. 

 Since river running is a more or less continuous gauntlet of submerged snags and hidden hazards—even in flat water areas—there seemed to be a real advantage associated with shallow draft.  It would of course keep the vessel on the surface where the grasping current might only hope to scrabble with its fingertips, but to my mind the bigger advantage would be the lower risk of an unseen boulder or floating log or submerged reservoir stump punching a hole in the hull’s thin skin.  But very shallow draft means that a boat is beamy and flat-bottomed, and this often translates into a very harsh motion in rough water.  A compromise would have to be made. 

River Rat
Kobuk under snow

CHARACTERISTICS

Length overall

   20'-2"

Beam

   8'-0"

Hull draft

   11"

Freeboard forward

   3'-0"

Freeboard aft

   2'-0"

Average passengers

   2-4

Hull depth midship

   3'-3"

Hull weight (approx.)

   1100 lbs.

Displacement

   3040 lbs.

Cockpit size

   13'-6" x 6'-0"

 

Hull type: Modified sled garvey with 12o deadrise. Developed for sheet plywood or aluminum planking with built-in chine flat spray rail.

Power: Single or twin long shaft outboard motors; 50 hp minimum, 100 hp will suffice for general use, with higher hp optional. Inboard stern mounted engine coupled to an inboard/outboard or jet pump are optional. Maximum weight of 1000 lbs. An engine in the 300 hp range should be ideal for most purposes. V-drive can also be used but not detailed.

Can the hull be extended or shortened? Yes. Up to 10% as detailed in the plans. We do not recommend increasing the beam.

 

Cross Section of River Rat
Cabin Skiff
Cabin Skiff Lines
Photo of Cabin Skiff
Cabin Skiff: Interior Layout


Picking a Plan

When I first started poking around in my search for a suitable boat design I discovered Glen-L Marine, a California company that specializes in selling boat plans to home builders.  They sell plans for most any kind of boat you might ever think of building, and all their plans are tailored to the limited skills and resources of the typical amateur builder.  Two different boats in their catalog caught my attention and for some months I struggled to make a choice.

One was the River Rat, a 19’ runabout that it appeared could be lengthened somewhat without much additional work.  It was promoted as a cruising boat, but it looked as if a cabin and bunk could be added without risk of compromising the hull.

The other was a very popular Glen-L design called the Cabin Skiff.  This was a fascinating little craft—a mini-cruiser only 17’ in length with a cabin and a bunk and an intriguing method of construction called “stitch and glue.”  Stitch and glue construction is revolutionary because it eliminates the need to build a framework for the boat: no keel and no ribs.  The hull is planked in plywood.  Ply sheets are butt joined to make a long strip that is then cut to a shape specified on a large piece of paper (much like a seamstress cutting a pattern for a dress).  Fabricate another such strip cut in mirror image and—voila!—you have the two halves of the hull.  To assemble, you stitch the two strips together using cheap copper wire and then slather the stitched seams with very powerful glue that holds the entire boat together.  The wire has no structural importance.  It simply holds the hull together while you apply the glue.  The whole job can be done on the garage floor, even if it isn’t flat.

The Cabin Skiff has enormous advantages.  In addition to being quick and easy to build, it is very light (because it has no heavy structural members) and can therefore be pushed at good speed with a relatively small outboard engine.  This would be a very economical design for the trip I had in mind and, besides, I find innovative technologies like stitch and glue almost impossible to resist.  Nevertheless, in the end I reluctantly opted for the more traditionally constructed River Rat.

The River Rat, I decided, would have just enough additional size to accommodate an inboard engine and water jet propulsion system—and I very much wanted to use this sort of power train for two reasons.  The obvious one is that a jet draws no water and its impellors are almost totally protected from damage (although fouling with rope or weeds or the like is not uncommon).  This struck me as a great, good thing because it would mean that nothing protrudes below the hull which can therefore be navigated in as little as a foot of water.  Such a boat could even negotiate small rapids.

The second reason has nothing to do with jet drives and has a lot to do with childhood.  As a youth my father had a little Penn Yan rocket with a towering, black, 90-horsepower Mercury outboard hanging heavily on the transom.  At that time—in the 50’s—it was the meanest, fastest boat around, but there was a gleaming mahogany Chris Craft kept in an expensive boathouse at the other end of the lake and I secretly lusted after the deep rumble of its powerful engine.  At the time I feigned disdain for this underperforming piece of affluence, but in my heart I loved to listen to its gurgling idle at the dock and its baritone roar under way.  Now in these later years speed is less important to me and the sound of an inboard has been calling, calling.

It also seemed that the River Rat would be a reasonably tough and sturdy boat.  It would be entirely glued together—just as with a stitch and glue project—but it also would have a keel and ribs and stringers that I could slightly oversize without adding a significant amount of weight.  All boats are more or less eggshells if they strike immovable objects while afloat, but I should think that a heavier structural system would be less susceptible to the wracking and twisting and pounding that any hull must put up with in rough water.  On rivers and protected waters, I thought, either design would work sufficiently well, but in rougher conditions the heavier construction of the River Rat might be an advantage.  This thinking was exactly opposite that of the promotional literature, for River Rat was billed as a specialized river craft whereas the Cabin Skiff was praised for its all-purpose nature.  I was able to convince myself of the contrary, however.

I had mulled over these considerations for some months when in the late summer of 1995 I found myself driving a U-Haul truck from Texas to Colorado.  Alone in the cab with nothing but my thoughts to keep me company, I stopped at a gas station in the lonesome Texas panhandle and placed a call to Glen-L Marine to order the River Rat plans.

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