Cheap One-and-a-half Sheet Plywood Boat

Want to go sailing or fishing, but don't have the money to buy a fancy new boat? Well, you've come to the right place! Like you, I am also a wannabe sea captain on a tight budget. You won't learn how to build a luxury yacht here, but you will have a unique, durable, little boat at the end of this tutorial, and you'll have fun making it--buying complete products is so yesterday.

Those who have lurked around this site regularly will know that there are many Instructables that teach boat-building, but I wanted to build a boat that drew its inspiration from Chinese style fishing boats. The design is loosely based on some images I have found online. Although Chinese fishing boats are usually long and narrow, I had to adapt the design to fit the low cost of this build--I only have a budget of about $150, which includes wood, resin, etc. The end result is much shorter than traditional Chinese fishing boats and is made from different materials. The boat I will make has a similar shape to western canoes, except the stern and bow are flat instead of tapering to a point. This design makes the boat more resistant to larger waves and splashes, but at the cost of some speed. Anyway, enjoy!

Materials:
(there is usually a scrap wood section at your local Home Depot where they sell perfectly good lumber for extraordinary prices ($0.5, $1, etc). Always check these places first. You can also reduce the cost of this boat significantly by sourcing materials from Craigslist or other places.)

4'x8' 1/4" plywood
(You want marine or exterior decking quality wood. Find one that is straight and that has very few knots. I bought mine from Lowes. Ask them to cut it into three 16"x8' strips. ~$27)

4'x4' 1/4" plywood
(~$16)

0.5"x3"x4' wood boards
(These are just the common rectangular wood planks you will find at any Home Depot. They don't have to be these exact dimensions. Just get a couple of strong, long, and skinny boards so that you can make yourself a few support studs for the spine and a seat. You should be able to find these in the scrap section of Home Depot. ~$3) 

1"x2"x8' wood sticks (x6)
(While Lowes had these labeled as 1"x2", I found the actual measurements to be around 0.7"x1.5". You'll want to get something around the dimensions that I have, because you will be bending these sticks. If they are too thick, then they will crack and potentially break. ~$20)

80 grit sand paper
(~$5)

1" drywall screws (buy a box of it)
(This length should be slightly shorter than the combined thickness of your plywood and the sticks you bought. Any longer and it will come out the other side when you attach the plywood to the sticks.~$6)

3" screws (20)
(~$5)

Wood glue (1 medium sized bottle)
(~$4)

Epoxy/polyester resin (1gal) & fiberglass tape (8 square feet) ***updated***
So I noticed that the picture of the "epoxy resin" I had posed previously was in fact polyester resin (thanks to Jobar007 for pointing that out). When I had asked the employees at Home Depot for epoxy resin, she had pointed to the one I had used. At the time, I saw that the container read "fiberglass resin" and just assumed it was epoxy. Don't make the same mistake I made! Read the ingredients list on the back of the container! So, here, you have a choice to make to either coat your boat with epoxy resin or polyester resin. While polyester resin is not as impact resistant, waterproof, and sticky as epoxy resin, it is significantly (4 to 5 times) cheaper than epoxy resin. And although polyester resin forms a strong bond with itself, it forms a much weaker bond with other materials than epoxy resin. To be honest, many boat builders swear by epoxy resin, but my research tells me that polyester will work fine on a small boat that will not be constantly in the water. So make your choice depending on how you will use your boat. Personally, my boat is functioning fine, but then again I only use it 2-3 times a month. Thanks for reading and I apologize for the inconvenience. 
(~$35 & ~$6)

Opaque Waterproofing/weatherproofing base paint (1 gal)
(Behr is a good brand. Make sure the paint is water resistant and is opaque. Epoxy resin is what allows your boat to stay water proof, but it is afraid of sunlight. You need to cover it with a good opaque paint. ~$25)

Recommended tools:

Japanese hand saw
Plainer
Electric drill w/counter sink bit&Philips head bit
Measuring tape
Disposable paint brushes (~$0.5 ea)
A friend/helper
(the more electric versions of these tools you have, the easier it will be)

This is an optional step, but I found it helpful when I made my boat. I am quite tall (6'4"), so I had to make sure that I would fit before making the plywood boat. A good way to do that is to make a scaled model of the boat and of you out of 3x6" index cards. This also gives you and idea of the shape and dimensions of the boat. By using a 3x6" index card for your model of the boat, which is made from 4x8' plywood, you will end up with a 1:16 scale for your model. Be sure to make a small version of you with the correct height and width so that you can see how you'll fit in the boat.

As this is an optional step, I won't go into the details of how to make the model. Read on to the meaty part of the Instructable. 

***VERY IMPORTANT***
It is very difficult to verbally describe the process of building the boat. So please look at the images. I've included many dimensions in the pictures. Click on them to get a better view. Thanks again.

The first thing we'll want to do is to cut the two big pieces of wood (the 4'x8' and 4'x4').

4'x'8':

The easiest way to do this is to ask the attendants at Lowes or Home Depot to cut your 4'x8' lengthwise into three pieces. Each piece is 16"x8'. Set aside one of the pieces; you'll use that for the boat's bottom. We are going to focus on the remaining two pieces, which we'll use to make the port and starboard sides of the boat. Take one of the pieces. Measure 24" from one side and 16" from the other. Then draw a line from the mark you just made to the opposite corner, creating a triangle. Mirror your procedure onto the other piece of wood. 

4'x4':

Now take your 4'x4' and measure out a 16"x28" rectangle. Then measure in 4" from two of the vertices on one of the short sides. You will now have a trapezoid. Cut this trapezoid out--it will be the bow of your boat. 

Now measure another rectangle with dimensions of 24"x16". Again, measure in 4" from two of the vertices on one of the short sides. You will end up with another shorter trapezoid. Cut it out. this will be the stern of your boat.

Take one of the six long sticks that you bought and cut it to the length of the longer sides of the two trapezoids you have. Attach them to those sides by first drilling with the countersink bit. Attach the sticks to the trapezoid using wood glue and the drywall screws you bought. This is the bow of the boat.

Next attach the bow to the port and starboard pieces you cut out in the previous step. Remember to always use wood glue and the countersunk bit to make the screws flush with the side.

Cut out two pieces of sticks--one 15" long, the other 32" long. Then measure 24" from the stern of the boat along the port and starboard panels (you haven't attached the stern yet) and mark the spot. Take the 15" stick that you just cut and screw it to the two marked spots. This hold the sides apart as you try to attach the stern of the boat and create the familiar curved shape. Being that this is my first boat build, I made several mistakes, one being that I installed this piece of wood flush with the bottom of the boat. You don't want that. Instead, attach it about 1 inch below the bottom.

This next step is very important! Once you've finished with the previous step, take your construction outside and water it down with a hose. If you don't do this, you might crack the wood.

While the wood is still wet, attach the stern. The process is very similar to what you did with the bow, except that the wood will resist your efforts. You might want a friend to help you out.

Once you have that completed, you will recognize the familiar curved boat shape. At this point, however, the boat is still very narrow. So, with the help of your friend, insert the 32" stick directly above the 15" one. This is extremely difficult, but work at it and you'll be able to do it. 

Measure the length of each side of the bottom of the boat. Mine were 56", but yours could be slightly different, so take your measuring tape and measure along the curve of the bottom of the port and starboard sides. Now collect two of the six 1"x1"x8' sticks you bought and cut them to the correct length. Then cut the tips of each of them at a 45 degree angle so that they will fit against the stern and the bow.

Get a friend to help you with the next part. It is best if both of you hold the stick while you stand at the stern and your friend at the bow. Put wood glue over the sticks. Starting from stern, aline the stick with the inside of the curve of the side of the boat. Drill a hole from the outside through the plywood into the stick with your countersunk drill bit. Then use the drywall screws to fasten them together. Make your way from the stern to the bow using one screw every two inches or so. As you make your way across the boat, communicate with your friend, telling him whether you need him to raise, lower, or bend the wood. Do this step slowly and methodically, and please use the countersunk drill bit so you don't crack the wood. 

Once you are done with the bottom "trim" (?) you'll want to add the spines that hold the sides of the boat apart. You will be using two of the wood boards that you bought for this operation. Starting from the back of the boat, measure 18" toward the front and make a mark on the trims you just installed. Then make two more marks at 40" and 49".

Now you are going to cut your wood boards and use them as the spines. Once again, because of human error, the measurements you need might be different than the ones I used. So the best way to do this is to simply place the boards at the appropriate marked locations and pencil in the measurements. Due to the curvature of the boat, the ends of the boards will also be curved. I have to warn you that cutting these pieces to the right size is quite time consuming. This is when using the plainer comes in handy, as you can shave small pieces of wood to create the perfect shape. Apply wood glue and attach these spines to the rest of the boat using the 3" long screws you bought. Take care to screw in horizontally when using the longer screws, because any error will cause the screws to poke the top or bottom of the spine. Use two screws on each side of each of the spines. 

Up to now, the sides of your boat were held apart with the two sticks from step 5. With the addition of the spines, you can now remove the bottom stick. You'll want to remove the top stick as well, but you must add alternative support structures before then. This is what this step is about. 

Everything will happen above your middle spine. First, take one of the six 8' sticks you bought and place it flush against the side of the boat, above the middle spine, and resting it above the bottom trim. You want to mark and cut it so that the top of the stick is flush with the top of the port and starboard sides. Repeat two more times to create the triptych. Next, you will want to triangulate the corner using one the rectangular wood planks you bought. Cut it to 8", and cut the two ends of the 8" plank at about a 30 degree angle. Once again, you'll want to fine tune this with the plainer due to human error. When you are done, you should have a piece of plank that will fit nicely against the middle spine and the triptych you just created. Repeat the whole process for the other side. You can now remove the top stick that hold the sides apart.

One thing that I forgot to do is to cover the triangular openings that the triptych, the spine, and the support plank created. This made it incredibly difficult to coat the inside of the opening with epoxy and paint. You should cut out a piece of wood that fit this opening and cover it up. Actually some of the scrap wood you trimmed from the 4'x8' will do nicely.

Okay! This is the last piece before your boat actually starts looking like a boat! Excited? If not, go eat some chocolate, get a sugar buzz, then continue reading.

Flip your boat over. Take that third piece of the 4'x8' that you left in the corner and place it on top of the bottom of the boat. While your friend is holding the plywood down, trace the contours of your boat onto the plywood. Then take your hand saw (or electric saw if you are rich) and cut along the line you just drew. Put some wood glue onto the trims and the spines and screw the bottom to the rest of the boat. You should drill between the screws you had already installed back when you attached the trim so that the two screws don't bump into each other.  

This is a very short step. Take the remaining two 8' sticks and attach it to the outside of the top of the port and starboard sides. Since the stick and the boat are both 8' long, it should fit perfectly along the side of the boat.

The attachment process is very similar to the installation of the bottom trims. Smear some wood glue on the stick. Getting your friend to help you, start from the stern and work your way toward the port of the boat. This time, you'll want to install the screws from the inside of the boat pointing out. Remember to always drill a hole with the countersunk bit so you don't crack the wood. Do the same on the other side.

As I mentioned in step 1, under "Epoxy/polyester resin", I chose polyester resin instead of epoxy, but the process should be very similar. From what I read, other than the mixing ratio (consult the label on your container) and the color of the liquids, everything else is pretty much the same. You can choose to use whichever one you like. I have described the pros and cons of each, so choose appropriately.

Now this is where it gets messy and smelly. You definitely want to wear safety goggles and a gas mask while doing this (well you should already be wearing safety goggles). So for those who don't know, polyester resin is a brownish liquid that is very difficult to get off of your hands, so you'll also want to wear kitchen rubber gloves while working with it. For the resin to be useful, you have to mix it with a gardner, which is a clear liquid provided with the polyester resin. You mix the two together so that the mixture will harden more quickly (about 10-20min depending on the product). When the resin is fully hardened, which only happens at a warm enough temperature (so don't do this outside during winter), it will become a hard plastic. My brand of polyester resin is waterproof, resilient to damage, and a very good adhesive, although epoxy will be better at all these things but at an increased price. Once it dries with the correct mixing ratio, trying to remove it from the wood will usually result in damage to the wood. Sanding is a good alternative. 

Mixing either polyester or epoxy resin is a very precise process. You must follow the instructions provided with your brand of resin. Personally, the Bondo brand I chose specified a mix of 1 ounce of polyester to 10 drops of hardener. I found that the best way to do the mixing is to get a glass cup (styrofoam melt and paper cups break), find the 1 ounce mark by adding one ounce of water to the cup and drawing a line on the outside of the glass cup with a permanent marker. Remember that one ounce is 2 table spoons. Pour the resin to the mark, and add the appropriate amount of hardener. Then mix thoroughly with a scrap wooden stick. If possible, you should allocate a few hours to apply all the resin at once. If you wait too long (some times as short a time as 15min) the resin will harden in your cup and turn your brush into a rock, and you'll have to replace both. If you must take a long break, I suggest you finish applying what's in your cup and pour in a fresh batch of resin, but don't add the hardener. You can leave this liquid out overnight without it hardening on you. Unfortunately, your brush will probably become unusable, but this is why you buy the cheap $0.5 brushes. 

Before you do anything else, please note that there are two ways to proceed from here, and the choice is yours (yes, even more choices!). You can either choose to encapsulate your boat in resin, or just apply resin to the important parts. There are pros and cons to both methods.

If you choose resin encapsulation, which is basically covering every exposed surface of your boat with the resin so that the boat is effectively contained within a layer of plastic, you will have a more durable and water resistant boat. The trade off is that you will need significantly more resin, and the stuff is not cheap. Furthermore, one weakness of wooden boats is that they are susceptible to rot if not constructed properly. This usually happens when water is trapped in the wood for any extended period of time. Since you are covering the entire boat in resin, if you missed even the smallest spot and water gets into the wood, it will have nowhere to escape. This will inevitably result in rot. So if you choose this route, please be meticulous when applying the resin and put on at least 2-3 layers. You will then cover the whole thing with exterior grade water resistant paint.

The other option is to only cover the parts of the boat most in contact with the water, specifically only the outer surfaces of the boat. What you don't cover with the resin, you will cover with the exterior grade paint. The downside of this option is that the boat is not as well protected against water and wear. However, the upside is that rot is less likely to occur because there is room for water to evaporate. 

Anyway, the choice is yours. But before doing any of that, you need to fill the gaps and seams that you inevitably created between pieces of wood due to human error. Unfortunately, your brand of resin is likely not thick enough to fill these gaps, so what you do is add flour to your resin and hardener mix. Yep, just normal household flour. So, create your concoction like you would normally do, and add as much flour as you need. You won't mess up the mixture by adding flour as long as you mixed the initial ratios correctly. I found that by picking up the wooden stick and letting the liquid drip into the cup, I could tell if I had the right viscosity. You want something just past the point being able to flow--something with the consistency of peanut butter. 

To apply the mixture, scrape some up with your stick and put it on your gloved finger. Then use your finger to smear and smooth the resin to the seams. You'll want to add the mixture to every seam, gap, and perhaps even over the screws to prevent water penetration.

As you can see, I did not sand my application very well. Take my advice and sand the resin to as smooth as possible to make your boat more esthetically pleasing and your life a lot easier later.

Once you are done with both the inside and outside of the boat, proceed to the next step.

Now that you have sealed all the cracks, it's time to apply the normal resin (without the flour) to the boat. Before we do that, you want to make sure that the boat is completely dry. If it has been a day since you soaked the wood with water to bend them, it should be fine. 

This step will differ depending on which route you choose to take (encapsulating the entire boat in resin or just the outside), but the process of both are essentially the same. For those who choose to cover only the outside, just stop when you've completed your portion of the task.

As I mentioned before, the mixture used this time is just the resin and hardener without the flour. The mixing procedure is the same. We will first focus on the outer seams where the different pieces of plywood join each other. Before adding the hardener, take out your fiber glass cloth and cut it into 2" strips lengthwise. Place the cut strips onto the boat along the seams to get an idea of the position and quantity of cloth you will need. Once you are done with that, add the hardener to the resin and mix thoroughly. Remembering where you put the fiberglass cloth, take the cloth off of the boat for now. Apply a layer of resin along the seams where the cloth used to be. Then put the fiberglass cloth back onto the boat and press it into the resin with a brush. Now apply another layer of resin on top of the fiberglass cloth. Keep adding resin until the cloth turns to the same color as the resin. This is when you know you've added enough. Do this with all the outer seams, effectively joining the pieces of plywood with the fiberglass cloth. 

Now mix and paint the resin all over the boat so that no part of the wood is exposed. Wait until it dries and sand the boat to get a smooth surface. Paint it again. You'll want a total of two to three layers of resin, sanding between each application. Once again, if you choose to only cover the outside of the boat, then stop when appropriate. 

Please wear a gas mask, goggles, a long sleeve shirt, paints, and shoes when sanding the fiberglass. You don't want glass in your lungs. I forgot to wear long pants and a long sleeve shirt for my project, and glass dust got into my skin. They are so small that you can't wash them out. My arms and legs were hurting for days after. 

I think this step is pretty self explanatory. Cut some of the wooden planks you bought to the right length and install them to the boat as the seat and a few extra spines. If you choose the resin encapsulation method, then you must coat each of these pieces separately with resin before screwing them to the boat so that water will not get into them. You don't have to do this if you decide to coat only the outside. 

Sand the surface of the boat again so that everything is even but roughed up a bit. You see, resin is a very good adhesive, but dries with a waxy finish that makes painting on it a chore. By roughing up the surface, you are helping the exterior grade paint stick to the resin. Brush off the dust with a wet cloth when you are done. Let dry. 

At this point, you really can do whatever you want. Be aware, however, that resin is afraid of sun light, so you'll need to cover it with something. I covered my boat with a layer of opaque ultra white exterior grade deck paint. It resists mildew and has a glossy glass like finish. I chose it because it was cheap and would probably last a while. To be honest, a layer of opaque paint is the best protection against UV radiation, but some people choose instead to cover their plywood boats with 6+ layers of varnish. This seems to work. Others use opaque water/weatherproofing deck paint. For those lucky enough to find a oil based polyurethane paint, your'll discover that it is the best compromise between protection and price. You can also just go to a marine boat store and ask what kind of paint they have. Their offers will be expensive, but will give the best protection.

I decided to go minimal with my boat. I liked the white, but wanted a dash of color to spice it up. I chose green because it was not as obvious as blue on white. Just a stripe of deep green will give life to your boat. 

This is optional in the sense that you can buy a pair of paddles from Walmart for $20. If you want to make one, then stick around.

I decided to make a simple paddle using a PVC pipe I had lying around, a few zip ties, two 10" garden nails, and a couple of 1gal milk jugs. If you don't have these things lying around, you can make paddles with just about anything--a stick, a flat surface, you'll be fine. If you really need help, this website has a few good paddle Instructables. I just wanted to test the waters before buying a trolling motor, so my paddles were not the best looking set you will see, but they work.

Cut out the four sides of your milk jug, so you'll end up with four plastic panels. The more panels the merrier, so if you have three milk jugs contributing to a total of 12 panels, all the better! Take a single hole punch and make holes along the outside edges of the plastic panels. Also, punch three pairs of holes near the center of the panels as shown in the picture. Make sure the holes all line up once you stack the panels together. You can do this by laying a finished panel on top of an unfinished one and marking where the holes are.

Next, drill a hole slightly smaller than the diameter of your nails clean through the PVC, one near the end of the PVC, the other a couple of inches above. Make sure that the two pairs of holes are close enough together so that you can lay your milk jug panels over both of them. Jam the nails through them, stopping when the PVC is at the center of each nail.

Lay half of your total panels on the bottom of the PVC and the other half on top. All the holes you punched should line up. Use zip ties to attach the panels to each other and to the nail and PVC. This setup should provide a rigid structure. 

I hope you enjoyed this Instructable. It is my first, so please don't hesitate to give pointers; I am always willing to learn. I wish you the best on the open waters.

So I went out to test this boat this weekend and found a few issues. As this was my first boat, I was unaware of how it was going to perform, and the results have been a little disappointing.

The major issue I discovered was the lack of stability. It was almost impossible to stay upright in this boat, as it had a tendency to wobble and had tipped over several times. Now, to be fair, it could just be my lack of experience on a boat like this, but I kind of had the hopes that even a small boat would be stable to sit in. You canoeists out there can chip in about how your experiences are. The issue is that the bottom of the boat was too narrow, the top was too wide, and the sides were too tall, so the boat had a tendency to roll.

So I tried a couple of things to solve this issue. After the boat took on lake water, I decided to sit in the "bathtub" for a bit and see what will happen. As I expected, the addition of putrid water actually made the boat very stable. Now, for obvious reasons, this option is not ideal, so I made a few small sandbags and laid them on the bottom of the boat between the spines. This seemed to help a lot and the result was even better than with the water. The problem with this was that now I had to carry 20-30 lbs worth of sand bags every time I wanted to go sailing.

Another fix is to attach a pontoon made from a thick PVC pipe with its ends sealed up to the side of the boat. The pontoon will need to be 5-6 feet away from the actual boat. This will definitely solve the stability issue, but, once again, you will have to take another piece of equipment with you.

The third option is to make another boat exactly like this one and use that as a pontoon. This way, you and one other family member or friend can go sailing together. This is probably the most impractical solution.

So if I were you, I would not make this boat yet. Or you can if you don't find one of the solutions I have come up with too tedious. I now think the best way to treat this guide is as a cross between entertainment and a cautionary tale.

I am not giving up on boat construction though. I have more designs that I want to test, many of them cheaper, more sturdy, and easier to build than this one. I now realized that I probably should have worked out all the bugs before posting this Instructable. You can chuck it up to inexperience of a beginner, I guess. But I'll definitely learn from this one and make the next one better.

Anyway, thank you for reading this.