You may have heard that when it comes to building a boat, you can never have too many clamps. While that’s true, a large collection of clamps can be expensive and take up a lot of room in the shop. Fortunately, there are shop-made spring clamps that cost only pennies and are small enough for dozens to fit in a gallon bucket.
These spring clamps are cut from Schedule 40 PVC (polyvinyl chloride) pipe, which is made in white for plumbing and gray for electrical conduit. (The black Schedule 40 ABS pipe used for drains doesn’t have the spring-like quality of PVC and isn’t suitable for use as clamps.) I have more than 100 clamps made from 1 1⁄2″ and 2″ PVC pipe.
I cut the 1 1⁄2″ pipe in 5⁄8″ widths and the 2″ pipe in 1″ widths. The PVC cuts easily with power tools, but the pipe’s slick cylindrical shape requires care to keep it in place during the cut. A chop saw makes the cuts quickly, and I can hold the pipe in place against the table and fence. When using a table saw, I employ a sled. I have also used a bandsaw but a block with a groove to cradle the pipe is required to keep the saw teeth from catching the pipe at the beginning of the cut and rotating it. Whichever power tool I am using, I stop cutting while I still have enough pipe to hold it securely in place. If you don’t have access to a suitable power tool, you can use a hacksaw to cut the pipe; it just takes time. Once you have cut your rings of pipe, the last step is to cut through each one so it can open. I do that on the bandsaw. Again, you can use a hacksaw.
PVC spring clamps can be applied by hand if they’re not too hard to open. The clamps I cut from the 1 1⁄2″ pipe take 5.5 lbs of force to open them 1⁄2″ and 16 lbs to get to 2″. The clamps cut from 2″ pipe take 7 lbs to open them 1⁄2″ and 18.75 lbs to open them 2″. These numbers are also measures of the clamping force of the pipe clamps. As a comparison, a Pony Jorgensen 2″ spring clamp applies roughly twice the amount of pressure at the ends of its jaws. Iron C-clamps can apply even more pressure, but that’s not necessary for working with epoxy when glued joints need only to be pressed just tight enough for the excess epoxy to be squeezed out, while leaving a thin film in the joint—excessive pressure starves the joint of epoxy and weakens the bond. I’ve used PVC clamps for countless epoxy glue-ups and have never had a joint clamped with them fail, so they’re evidently not squeezing too tightly.
However, applying the clamps can be a chore once my gloves become slippery with glue, and if I have a thick stack of pieces to be glued, it’s hard to open the clamps wide enough to apply them. Opening them by hand to 2″ is too much of an effort for me, especially when I need to work fast and finish before the epoxy kicks off.
I have seen some pipe clamps equipped with handles—either nails or machine screws—that open the clamp when squeezed together. They may work on wide pieces of pipe, but when I drilled holes in my spring-pipe sections, I significantly weakened the clamp. And, installing handles in every clamp adds time, expense, and bulk.
Instead, I came up with a pair of DIY reverse-action pliers. The business ends of the pliers spread apart when the handles are squeezed together, and not only does the geometry provide a mechanical advantage, but the tool also takes advantage of my grip strength, which is more powerful than using two hands to pull something apart. Because the handles don’t cross each other, which would require a complicated pivot point, reverse-action pliers are easy to make.
I used 3⁄4″-thick white oak for the plier handles, 12-gauge (0.08″) aluminum for the side plates (4mm marine plywood would work as well), five 16D sinker nails, and rubber bands to make the pliers self-closing. I used a 5⁄32″ bit to drill all the holes for the nails. Three of the nails are used as rivets to hold the aluminum plates in place. After hammering, the ends of the two nails on the straight handle are cut by either hacksaw or bolt cutter approximately 1⁄16″ proud of the plate and are then hammered to flare them until the plates are tight against the wood. Before applying the third nail, which fixes the plate to the angled handle and holds the two handles together, a thin metal shim—a piece cut from a soft-drink can works well—is inserted between the plate and the wood. The nail is then flared as before, but when the metal shim is removed there is enough open space between the plate and the handle for the handle to move freely. The finishing touch is to stretch a couple of rubber bands over the pliers’ handles in front of the plates to make the pliers self-closing.
The two nails at the business end of the pliers will be glued in place, so sand or file the vinyl coating off each one and roughen the underlying steel. I’m right-handed, so I inserted the nails on the left side of the pliers so I can grip the tool with my right hand and apply the clamps to it with my left hand. The nailheads should stand 1 1⁄16″ above the wood to provide enough space for PVC spring clamps cut in 1″ widths. Once the nails are in position, drops of CA glue—the thin stuff that will pull itself into the perimeter of the hole—will lock them in place. When a clamp is opened by the pliers, the nailheads prevent it from flying off. An opened clamp stores a lot of potential energy, so the shop rule—wear eye protection—applies here, too.
In the decades since I started building boats, I’ve acquired a multitude of clamps, but there are some jobs that are best done with PVC spring clamps. They’re much quicker to apply than other clamps, they weigh next to nothing, they don’t stick to epoxy or get jammed by cured glue, and you can make as many as you like without breaking the bank or crowding the shop.
Christopher Cunningham is editor-at-large of Small Boats.
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