The strongback is simply the temporary jig used to hold the forms and stems in place while you build your hull. There are many different ways to accomplish the function of a strongback. You need a strongback to build a 14’ canoe or a 30’ sailboat. Even though they perform the same function, they will obviously be built differently as they have different requirements.
Builders will have differing opinions even on a strongback for a canoe or kayak and when all is said and done, as long as the strongback allows for the building of the hull and performs the function of holding the forms in place then it will probably work fine. The strongback described here is simple, versatile, and inexpensive and has been used to build hundreds if not thousands of boats around the world. This strongback is a simple box sitting on top of a couple of small tables on wheels. The strongback can be made from dimensional lumber or from ripped pieces of plywood, however it is very important that your strongback is straight and square so if you can’t find straight dimensional lumber then ripped plywood is the way to go.
The dimensions of a strongback for a canoe or kayak is fairly straightforward. It should be a few inches shorter than the boat to be built and wide enough to support the forms. That simply means if you are building a 16’ canoe then you will want your final strongback to be about 6” or so shorter than that so that the stem forms will overhang the strongback on either side. Having this overhang will allow you to strip near the sheer without your strips bumping into the deck of the strongback.
You will also note that this particular strongback is built in three sections. I have a couple of reasons for that. First because finding extra long lengths of wood to build it in one piece is unnecessarily difficult and second and more important to me is this design is able to expand and contract in size as needed. So if the percentages are high that you will be building another boat that will vary in length, this is the design for you.
As you can see from the picture, once each side is built to the right size, you simply slip the connector piece between the two and set six screws in each side to hold them together. Be careful with the length of the screws so that you don’t get caught on them if you have to work under the strongback.
The tricky part to this operation is holding everything in line and at the same level in order to put them together. The rolling table design used here makes this a simple matter. If it is your intention to use
some other method to support your strongback then you will likely have to find a long straight section of bench or a flat floor to get this done. It is very important that when all of the pieces are together, they form a long straight box. It will make leveling and aligning the forms much easier to accomplish.
Once the box is complete, it is a simple matter of putting a deck on the strongback. I choose to make my decks hang over the box about an inch on either side in case I want to use them to hold temporary bungee chords strapped over the hull during stripping. Setting a screw just under the overhang makes a great place to hook your straps. If you are using dimensional lumber, use extra screws along the edges to make sure that the board will stay in place and not succumb to cupping or warping during the building process.
We will talk about using a chalk line to make a centerline on your strongback deck, however if you have a table saw then you may want to consider putting the deck on the table saw and using a thin kerf blade, make a cut down the center of the deck no deeper than 1/8”. This works well and quickly gives you a centerline to work with, however be sure that if you are using a two-piece deck that the lines meet up and are straight from one end to the other. This is easily accomplished by pulling a string from one end to the other while attaching the second half of the deck.
If like most people you are working in limited space and there is a good chance that you are sharing that space with the rest of the family you will find the roll around strongback supports to be invaluable. There are two very good reasons to go the extra mile and build these. First your space is limited and you will need to roll the boat out of the way to do another task or perhaps you only have room to work on one side of the boat so you will need to move it back and forth. Second and more common is you have limited time to build the boat, however the space you are building in is used for other things.
In either case, it is a handy feature to be able to roll the boat into a corner out of the way when you need to. Building these supports is easy, and quick. All it requires is a 2’ X 4’ piece of ¾” plywood (the cheap stuff will do here) and a couple of 2” X 4” ‘s. The most expensive part will be the wheels. You won’t be supporting much weight so there is no need to get very large heavy weight wheels. No one is more sympathetic than I when it comes to the trials and tribulations of trying to rip a large piece of plywood when there is not a second pair of hands to help. That is the reason for the dimensions shown here. Most stores will sell “handy panels” already cut for you. At the very least they will cut in store to your desired dimensions. This also makes getting them home easier if you don’t own a pickup truck.
During the video you will probably notice that the strongback is flanked on either side by a 2” X 4”. This is done so that when you move the boat around it will move as one unit. Once the strongback is sitting on your two supports, simply cut short pieces and screw them in on both sides of the strongback. This will also avoid the unlikely but possible catastrophe of the strongback sliding, or pivoting off the supports during the building process.