Rounding corners. Freehand or exact?

So my philosophy with building stuff is shoot for 100%, settle for something less. Inevitably, as hard as I try there are errors and mistakes. So I try to cover all my bases and hopefully even with the errors, I end up with a 90% or better job. I have plowed through projects on the fly and have had to take it apart, adopt wierd changes or perform difficult cuts while something is already installed.

Rounding off of the corners was the next issue I was presented with when I was going to draw it out to get cut by a computer. In the past you measure 12" in each direction and approximate a curve. I figured the curves would mate best if I could make specific arcs for each angle. Picture throwing a circle down that touches the edges at 12" from each side of the angle.

Everything went back to the solving for X problem, but I figured 2.5" was close enough and made the following calculations:

Armed with my angles, I can figure for the radius of an arc that intersects at 12" from the angle.

Now it's time to find some string and tie a pencil to it to draw an arc. I can then cut it out and have a template to draw for each specific angle. The very shallow angle that has a radius of 461" only cuts into the corner 1/4" and I'm not sure if that's worth drawing out. The next shallowest angle cuts in about 1/2" and the sharpest angle cuts in 7/8" from the corner.

Using a board as a transom

So I really liked the idea of having 100% of the plywood being 100% of the hull, and then I thought "Hey, a 1x12 would make a perfect transom". When I drew it out, it looked even more like a boat. The use of a board means you can clamp a trolling motor to it without re-inforcement. It also allows the scaling of the boat into two and three sheets creating a 13'6" fishing boat and a 16' runabout with only three sheets. They all look exactly the same, here is the 2 sheet drawing:

All of a sudden I wanted to bypass building the one sheet version and go straight to building the more usefull 2 sheet version that uses 12" and 24" panels instead of the 8" and 16" panels of the 1 sheet model. Things got a little more complicated, I figure I have a small trailer and two layers of 3/4" plywood would make a good transom, etc. etc. I liked the idea of being able to take a few people on the water even if the logictics were getting more complicated. Then I thought "what would the yield be if you used 16" and 32" panels and make a 3 sheet boat?" It yields and almost passable for normal 16' runabout!

 

 Everything seemed to fall in place. 1/4" ply for the one sheet. 3/8" for the two sheet and 1/2" ply for the three sheet. The logistics got even more complicated for the 16' boat, including the addition of a sole, bigger trailer, etc. I filed that away to dream about only. Back to the one sheet design. I think my boy's batman action figure will get a ride in a 1 sheet skiff in the next few days.

 

 

 

 

Solving for offset "x"

So, I'm trying to work on the measurements for cutting the sheet of plywood. It lays out really nice until you get to one irritating little detail. What is the exact offset point on the 16" wide panel? The 8" panel is straight on one side, so no thinking there. The other panel comes to a point a little bit away from the edge. When the measurement is taken off the graph paper, it comes to about 2.5". This seemed good enough for the model and probably even for plywood so why bother?

It really started to bug me when I thought of making the cut drawing into a bitmap so I could give it to a customer of mine. He has a machine that I believe is called a flying router something. You throw in a sheet of plywood, a vacumm sucks it down and a bit comes out and cuts it perfect everytime. I thought of giving him 4 or 6 sheets of plywood and letting him cut them for me, perfectly.

When preparing for this, I stared at the halfbreth and tried to find two sides and an angle or two angles and a side, without success. With the right angle of the 8" side, the three side measurements locked in and the right angle between the top and the verticle, I can't imagine it moving or having any variables. Yet I still can't figure it out. I even asked my High School Junior, who right away denied knowing how to do it or even having a clue, despite taking pre-calc.

So, I'm reaching out to anybody who can help me solve for "x".

The idea gets modeled

I once heard a chef say that the first thing a chef does is throw down a piece of meat and decide what to do with it. Ever since then I found myself thinking of this everytime I throw down a piece of plywood and decide what to do with it. Sometimes you have a pretty good idea. Sometimes, you need to measure it to know what your options are.

I cannot think of a finer end to a sheet of plywood then to make a boat out of it. When you don't actually want to go in the garage to cut & glue, it is a fine excercise to try to optimize the boat/plywood relationship. The prism certainly had efficiency and theory going for it, but I wanted something that looked more like a boat.

Following is what I came up with:

I looked at this half bredth for a while and decided, for now, this was the best comprimise between depth and width. I kept one side of the 8" piece a 90 degree to eliminate another lengthwise splice. There are a bunch of ways to use this concept. I'm still undecided between making the kayak or skiff version, but decided in the end to make the kayak, because it is purest to to 100% of the hull/ 100% of the sheet. This is how it cuts up and lays out:

I have a sheet of 1/4" BCX laying around and almost subjected my brother in law and his buddy to partying around my sheet of plywood last Friday. Not wanting to take over the garage, I cut it up out of cardboard instead. The next day, I handed my kid a 6" ruler and asked him to bring me one of his action figures. After rejecting the transformer, I settled on batman and took the following pictures:

Sure I felt a little silly when my wife saw me playing with an action figure in a paper boat. I got over it because I, unlike her, know it's a significant development in one sheet boat design. I still feel a little like a geek though. Hey, she likes to kayak and one day she could be taking the place of batman in a full sized "Bittner" one sheet boat.

The lure of one sheet boats

In life, bigger isn't always better. If you have to carry it, that cetrainly applies. It is considered efficient and a good use of resources to make small things engineered to a specific task. It is easier to make and maintain small things. These factors certainly apply to small boats. Sure they have their useful limits, but good use can be made of them.

One sheet boats have a certain draw. Theoreticly 32sq ft of hull is all a person needs for a beach toy, small fishing boat or row boat. This has been accomplished in a myriad of different designs as will be illustrated in upcoming posts. The "OSS" has had success, even I have built a few. Barges and prams have been done with good success and offer utility to their owners.

It was the "Prism" that offered up the design constraint of using 100% of the sheet on the hull. It only makes sense to max out all 32sqft. The variation on the designs were all intriguing and fun to study. In an effort to make the design look more "boat like" and still use all 32sqft, I have come up with my own way of cutting up a sheet of plywood.

Much like the "Prism" variations, I have made variations for longer, wider and designs that use a board for a transom. These latest units may not meet the purists requirements, but do produce the most "boat like" version and can be adapted to engines. The basic design can be adapted to a 2 sheet 12' Jon boat or a 3 sheet 16' runabout.

It is winter in Chicago. There is nothing you can do to scratch the boating itch, but get it ready for spring, or if you don't have one, build one. My design has been modeled and tested. Now, to decide between the Kayak or Skiff, clear the garage floor and let the cutting and gluing begin. This blog serves as a location to post my resources in a handy, universaly accessible place.

The internet is a wonderful way to bring people with such specialized interests as "one sheet boats" to gather and discuss their ideas and experiences. So I would like to offer this very specialized community of boat builders and designers, my take on the best way to make a single sheet of plywood into a boat you can use.

I hope you like what you see and try to build one yourself. If you do, post pictures of a completed project for others to use as inspiration. If you find a better way, please advise. If you have questions or concerns, let's hear them. It's collective inteligence and building off other's ideas that advances development. I can hardly wait for the next innovation in one sheet boat design.