One Sheet Jonboat

The town I live in has a boat building/ racing contest every year. The challenge to this contest is the materials you are allowed to use as well as the ones you are not. You are limited to One sheet of plywood, Two 2x4's, One roll of duct tape, One pound of fasteners and no other adhsieves

This year my wife expressed an interest in entering the contest so I designed a boat for her that is more stable than last years version.
I ran into some problems with my prototype. The design was good but I needed some extra screws in the bottom and I will explain that further in the instructable. There ended up being two slightly different versions of this design built.

Warning: Woodworking is inherently dangerous. You are using sharp tools some of them spinning at large RPM's. You need to be wearing eye protection at all times, hearing protection as needed and because you are going to be working on some very small pieces you must use a push stick. Niether I or Instructables bear any responsibility if you do something stupid, lose focus, act carelessly, or recklessly.
The same can be said about boating, you should be wearing a life vest anytime you are in a boat and always acting in a safe manner.
Please note that this design was inspired by the "one sheet wonders" group at Yahoo. For other great designs please stop and visit them. You may make and sell copies of this design but please give credit where it is due.

1) 1 4'X 8' sheet of 1/4 inch B/C grade plywood
2) 2 8" 2x4's (As few knots and a straight as possible, Yeah, Yeah I know) If you are not entering a contest like I was you might want to get a knot free 1x4 for the chine logs.
3) 1 Roll of Duct tape. (Once again if you are not entering a contest like I did get yourself some waterproof adhesive, chaulk and maybe some fiberglass tape and resin for the seams.)
4) 1 Lbs of fasteners, I used about 1/2 lb of 1"x6 coarse thread drywall screws. I f you can get 3/4 inch that will be great for the Chines and Gunwales and Inwales (Pronoucned gunnel and innel).
5) You will also need a scrap piece of wood 32" x12" that you will use for a removable form
* same as First Instructable

Here is a list of the tools I used:
1) Jig Saw/ portable scroll saw
2 ) Battery powered drill
3) Belt Sander
4) Circular saw
5) Hand plane
6) Adjustable artist triangle
7) Drill and countersink set including #6 Drill and Phillips head bit.
8) Squares ( I used a Try Square, and a Framing square. but you can use a straight edge instead of the framing square)
9) Tape measure
10) Clamps- as many as you can get your hands on, there is no such thing as to many clamps.
11) Disc Finish Sander
12) Back saw
Not pictured:
8'+ Straight edge
Protractor
Band saw
Table saw
* Same as first instructable

The transom is the back or the stern of the boat.. This design uses a flat transom.
The easiest way to construct it is to measure up 11" from one of the ends and mark with a straight edge across the 4' width of your plywood. 
I slipped two 2x 4's under the plywood and set my circular saw depth for a little over 1/2 inch and cut away the tansom.

.The purpose of the frame is to hold the sides in place so that you can add the transom and bow pieces, Chine logs, and finally the Bottom (You can also leave it in place to install the Gunwales and Thwarts as I did).
The first step is the measurement of the bottom width.
This is obviously the maximum width you can have. I subtracted about an extra inch to account for the (2) 1/4 inch thick sides and I wanted about a 1/4 inch over hang on both sides for margin of error.
The plan I used called for the maximun width at the top to be 32 inches, but I felt that would torture the plywood just a little to much for my taste so I reduced that by a little over an inch (Use your own judgement here).
My final dimensions ended up with the top at 30 3/4 inch, base at 22 1/2 and the height of 12 inches. There are two ways to determine the angle to cut this to on the table saw. You can either use the adjustable triangle or set it on top of the saw and line it up with the miter slot. Loosen the miter guage and slide it up to the frame and lock the angle into place. (You will want to save one of the triangles you cut to set the blade tilt for your chine logs.)
Next you want to notch all four corners. the ones at the Bottom are going to be 1" tall and 2" wide. This gives you clearance for the chine logs. The top ones are going to be about 1/2 inch wide and about 2" tall for installing the gunwales ( I didn't cut out the gunwales notches and had to remove my frame cut them out and reinstall the frame, save this step and cut them out ahead of time).
I cut mine out with a band saw but you could use a hand saw or jig saw.
*Same as in First Instructable

Use the Tape measure and measure in from each of the side factory edges 12". Do it on both sides and both ends. I marked it using a sharpie so it would show up in the pictures. Next set it on top of the 2 2x4's leaveing a gap of 3-4 inches.

Set your Circular saw so that it just cuts through your ply and does not cut into your work surface.

Run it down both lines so that you have two strips 12 inches wide and 1 piece that is about 24 inches wide.

Constructing the temporary frame first gives you a pattern to use and you can use the exact same table saw set up.
I layed the temporary frame on top of my plywood so the bottoms lined up and then just traced the sides.
I then cut both of my sides to the same angles as the temporary frame.
Next I ripped two pieces from the 2 x4 with the least knots. Both of these should be about 3/4 inch thick.
Take one of the newly cut pieces and lay the bottom of the transom on it and trace your size on it. You can use the transom and the miter guage to make sure the angle is dead on
Cut this with your table saw and repeat for the top piece. Screw both of these into place. Next cut the sides. The fit on the bottom and sides needs to be very good since this is going to give you your seal and keep the boat water tight. 
Note If you are not doing this for a contest like the one I entered you will want to use a good quality adhesive for this step.

I wanted this boat to be more stable than my first one since I designed it for my wife. I kept the sides a constant width but up swept the front about 6 inches to give it some planing ability.
I measured 3" down from the end I had cut (Leaving the factory edge att he bottom) and 42" back along the length of the bottom.
You can see that I put a nail at each location. I them laid a thin stip of wood against both nails and gently pulled it till it had a fair curve by eye. In the third photo you can see that I put a nail on the inside fo the curve to hold it in place.
I used a sharpie marker to draw the curve.
***NOTE***: To make sure that both sides are identical they need to be cut together.  
I used a band saw but a scroll saw or hand jig saw works jsut as well to cut the curve out. Once the curve is cut use a hand plane or sander to get rid of any bumps and make sure the curve is smooth and fair.
Note: Save the pieces you cut off you will use them to make your paddle.

Safety note: Make sure you are using a push stick for this operation.
Use the second 3/4 piece that you cut in step number six Find the center of piece from both edges and mark a cross on it. Laying the 1 1/2 wide part on the table use the scrap triangle from step 4 and run an angled line through the center of the cross.
Set the blade angle with the same triangle.
Place the 3/4 edge up against he saw fence and eye it up so that you will be cutting right through the line you just made. You want this to be a centered as possible to that both pieces are identical.
*Same as first instructable.

NOTE: The sides need to be mirror images of each other so make sure that you are attachng the chines to the insides. The only thing as bad as making two left sides is making two right sides.
I began by attaching the chines near the bow (front) with two screws. I slowly pulled the chine along the curve attaching it with screws as I went along. The first two screws were about 5 inches apart and the distance increased till I got  to the straight edge.
Now the straight edge should be your factory edge this will give you a perfect edge to be lining up with the chine log and help you get a good seal.
You can see in the last photo that I trimmed the chine log so that I had 1 inch of clearance to attache the transom.
Note If you are not doing this for a contest like the one I entered you will want to use a good quality adhesive for this step.

For this part you may want to enlist the aid of an assistant. I did not have that luxury so I lined up the bottom of the side and the bottom of the transom and used a couple of nails to hold them together untill I could put the screws in place. One again this is going to be a water tight joint so you want everything to line up as good as possible.
Note If you are not doing this for a contest like the one I entered you will want to use a good quality adhesive for this step.

Lay one end of the 2 x 4 agains the top of the transom and cut this to the same size. This will make sure that you boat keeps a constant width the whole length.
You are not going to permanently attach this until after the bottom is in place. 

Using the marks from when you measured your 42 inches install the temporary frame.
You want the chine logs to line up with the "bottom" of the frame (Remember you are building this boat upside down)
I used two screws on each side make sure that the frame is at right angles to your work surface.

Line the remaining factory edge of the bottom up with the transom Mkes sure it is square. I used 5 screws to hold this in place. Once this was done I attached the bow piece in place as a temporary frame as well. Make sure that you have an equal amount of over hang on each side and attache the bottom to the chine logs. I used screws about every 8-9 inches.
Unless you are very sure of your self work from side to side putting in 1-2 screws then doing the same on the other side. This will prevent the boat from racking.
When you get to the bow end you will realize that your bottom is too short. This is not a problem, just go to the next step.
I had about 3/8th of an inch over hand on each side. This is intentional so that you don't come up short and have a gap.
After I completed step 14 I came back with a plane and made the bottom and sides flush. You can use a hand plane, electric plane or even a belt sander.
Obviously the last two are (much) faster but the hand plane has (much) less risk of taking off to much material.
*** NOTE *** When I installed the bottom on the first version of this I forgot that I was not using an adhesive and I put the screws approximately 8 inches apart. When I put her in the water I had a leak on both sides. Not very big, but a leak none the less. If you are using a good waterproof adhesive 8 indces should be fine. If you are building like I did that you need to have them closer, much closer, about 3 inches should do it. I also added addtional gunwales to the bottom. (See the next step)
Note If you are not doing this for a contest like the one I entered you will want to use a good quality adhesive for this step.

As I mentioned in the previous step I added these on the second version of this. Cut these gunwales out at the same time you cut out the ones for the top. They should be about 1/4 inch thick. ** NOTE** Because these will have to curve to match to boats bottom you want pieces that are as knot free as possible and this is the same. process used for installing the chine logs in step 9.
I clamped the gunwale to bow end and began to drill and screw this into place. 
Now the gunwale is straight (more or less) and the bow has a curve on it, so the gunwale will not match the curve.  I used a squeeze clamp to GENTLEY draw the gunwal up to match the curve. I would drill and place one or two screws until I reached the flat section of the boats bottom. Then you can drill allyour holes and come back and put the screws in place. This is the same method used for installing the chine logs in step 9
Note If you are not doing this for a contest like the one I entered you will want to use a good quality adhesive for this step.

Remove the screws that held the bow in its temporary postiion.
You can have the bow piece flush with the bottom, or standing proud about 3/4 of inch like I did. Which ever way you decide mark the location on the side and remove as much chine long as you need to make it fit.
You can either chisel it or  cut it with a small hand saw. I used both methods to make sure that they would both work. The chiseling is faster but the sawing is more accurate. Once this is done screw the bow piece into place on the sides and bottom and trim the sides to length as shown in the third picture.
Note If you are not doing this for a contest like the one I entered you will want to use a good quality adhesive for this step.

Safety Note:Make sure to use a push stick for this part. Take the remaining piece of the 2 x 4 that you used to make the bow piece and rip it into strips 3/8th to 1/2 inch thick. If you cut them just over 3/8 ths thick you will have a bit heavier skeg for the bottom. You will need five pieces.

Start at the bow end and place one piece on the inside and one on the outside. these are your Gunwales (Pronounced gunnel) and Inwales (pronounced innul). Clamp these so that they and the sides are all as even and level as possible. Screw through all three pieces. Don't worry if the screws stick through a bit we will fix that later.
You are going to be about a foot short on each side so this is where you use the fifth piece you cut.
At this point you can remove the temporary frame and set it aside.

I wanted a bit more rigidity so I took the remaining piece of the 2 x 4 that I had used for my chine logs and transom framing measured the width of my boat at the 42inch point and cut the piece that is now about 2 x2 to fit in there and attached it with two screws per side. You can cut angles at both ends so that you get a nice tight fit. I did this by angleing the miter guage and sneaking up on the angle. It should be about 15 degrees. 

Note If you are not doing this for a contest like the one I entered you will want to use a good quality adhesive for this step.

I used the remaining piece of the the 2 x 4 that I used for the gunwales and inwales and made a skeg. the purpose of the skeg is to protect the bottom and to help the boat track in a nice straight line.
I measured center along the length of the boat and made a mark at the transom and at the point that the skeg reached from the transom. I attached it with screws every 12" or so and them flipped it over and put screws in from the other side in between the other screws (you will see them sticking through the bottom, don't worry we will take care of that int he next step).
Note If you are not doing this for a contest like the one I entered you will want to use a good quality adhesive for this step.

Depending on how long the screws were that you bought you may have some points sticking up. I borrowed a small grinder and knocked the points off. This is especially important if you added the skeg.
You can use pretty much any kind of an abrasive wheel or a belt sander if you are careful.
Make sure you get every point off you don't want to be in the water and find one.
For the record this is not me in the photo, It is one of my adult students who built a copy of my prototype. I was not able to take a picture of myself using the hand grinder. I really hope He is not in the witness protection program.

I strongly advise you to get a good quality primer and put on one or two coats. I had latex paint left over from my last boat so that is what I used. The primer really does a great job of making sure that the paint sticks.

Here she is in her natural environment. This is the first version. One of the neighbor kids is going to use this one in the contest. She wants the name her the Sea Dragon. My wifes boat is going to be called the Holzkiste, which is german for wooden crate.
Please keep in mind that I am an amatuer designer and make no warranties or guarantees about this design. I also strongly advise you to only use it in flat calm water and wear a flotation device at all times.