Tuesday, October 20, 2026

Woodworking Tip of the Day: Tape, Pins and Cleats: Holding Scarfs and Planks Without a Forest of Clamps

This is catching the MOAM's attention today….. the scarf that slid. You butter up a beautiful 8:1 scarf, set it down, crank on a couple of clamps, and the top panel skates right off the bevel like a skiff off a greasy launching ramp. Then you're out of clamps, out of open time, and out of patience. Here's the thing nobody tells you when you start building with epoxy: it doesn't need the muscle. WEST SYSTEM says to clamp only hard enough to squeeze a small amount of epoxy out of the joint, about the force of a firm hand grip. That means a roll of tape, a box of brads, a staple gun and a few cleats will hold most scarfs and plank laps just fine. It's the kind of holding I'm up against on the Chamberlain Marblehead gunning dory: long planks to scarf, laps to keep shut, and never enough clamps in a New England shop.

Why it matters: Glue-ups with yellow glue want real pressure. Epoxy doesn't. Epoxyworks puts it plainly: there's no need for the excessive clamping force you'd use with yellow glue, and too much pressure can squeeze out so much epoxy that you're left with a glue-starved joint. WEST's own troubleshooting list has "too much clamping pressure squeezed epoxy out of the joint" as a cause of failed bonds. What epoxy does need is for nothing to move while it cures. A scarf's slanted faces want to slide apart under pressure; Small Boats Monthly's Passagemaker review notes the scarfed plank pieces "slid against one another when pressure was applied by weights or clamps" (that's why CLC went to puzzle joints). So the job isn't squeezing. It's pinning, then pressing lightly and evenly. That's what tape, pins and cleats do best.

Materials

  • Epoxy resin and hardener, plus a thickener for the bonding mix (colloidal silica or microfibers; WEST recommends wetting out with neat epoxy first, then a thickened mix on one face)
  • Polyethylene sheet (3-mil works; one builder uses 12" strips under and over each scarf) or wax paper, so nothing gets glued to the bench or the caul
  • Clear, shiny packaging tape for wrapping cauls and spacer strips (Epoxyworks) and nylon-reinforced packaging tape (strapping tape) to use as a clamp
  • Small brads or finish nails: 20-gauge wire brads 7/8" long (Epoxyworks), or 1" finish nails for 3/8" plywood
  • Drywall screws and washers, with wax on the screws so they back out after cure (Epoxyworks)
  • Straight, flat cauls (a 1x4 or 1x8 a little longer than the panel is wide) and some scrap for spacer strips
  • Bronze or other non-corroding fasteners for anything you plan to leave in (WEST)

Tools

  • A long straightedge and a pencil for the centerline
  • Staple gun or brad nailer
  • Cordless driver and a pilot bit
  • Hammer, end nippers or tile nippers for pulling pins
  • A few one-handed clamps, pads covered with duct tape or plastic (WEST)
  • Plastic spreader or notched spreader, and a sharpened mixing stick for cleaning up squeeze-out
  • Optional: a soldering iron with a flat tip, for backing out a stuck screw

Steps: the scarf

  1. Lay out on a flat, covered bench. Strike a centerline down the table and a matching line on both panels. Lay plastic or wax paper under the scarf. Set the first panel feather edge down, line it up, and pin its far end to the table with a small brad so pressure on the bevel can't push it away (Small Trimaran Design). Plywood scarfs run at least 8 to 1 (WEST), so 3/8" plywood gives you a 3" bevel and 1/4" gives you 2".
  2. Wet out, then butter. Brush neat epoxy on both scarf faces. End grain drinks it, so go back and give the thirsty spots more. Then thicken a batch and spread it on one face, enough that a little squeezes out when you press the joint with about a firm hand grip (WEST).
  3. Drop the top panel and pin the scarf. Lay the second panel feather edge up on the first, line it up on your marks, and press it down. Now the trick: drive a brad straight through the scarf near each edge. One drift boat builder puts a 1" finish nail about 2" in from each edge, right through the middle of the scarf, and then screws each panel to the table so nothing creeps (Fly Fishing Traditions). Those two pins are what keep the bevel from skating when the pressure goes on.
  4. Press it with a cleat, not a clamp rack. Plastic over the joint, then a straight caul across it. Weight the caul (buckets of sand, paint cans, a car battery, whatever you've got) or screw it down. Epoxyworks' version: drill pilot holes through the clamping strip and the scarf into what's underneath, drive waxed screws with washers, and cover the strip with poly sheet or shiny packaging tape so it lets go later. Snug, not cranked. You want a bead of squeeze-out, not a dry joint.
  5. Clean it up while it's soft. Scrape off the squeeze-out and fill any little voids with it, then leave it alone until cure. Ten minutes of cleanup now saves an hour with the sander.

Steps: planks, laps and everything else

  1. Staple through a spacer. Brad nailers and staplers don't have much drawing power, and the fastener won't pull the plank in by itself. Hold the part in position, then drive the staple or brad through a wooden or plastic spacer strip so it seats against the strip and pulls out easily later (Epoxyworks). Wrap the strip in packaging tape and it won't get glued on.
  2. Use screws where you need pull. For heavier parts or a lap that won't close, drywall screws through a pad. WoodenBoat's glued-lapstrake article says it straight: temporary screws through the laps typically hold the planks while the glue cures, then come out and the holes get filled. Driving them at a slight angle on strip planks nests one plank against the last (Epoxyworks).
  3. Tape is a clamp too. WEST lists nylon-reinforced packaging tape right alongside C-clamps and bar clamps. Stretch it across a small part, a glued-up cleat, or a fillet joint, and it pulls with surprising force. Clear packing tape also makes a release surface on any caul, block, or spacer that touches wet epoxy.
  4. No holes allowed? Wedge clamps. For a bright-finished interior, WoodenBoat showed slot-and-wedge plank clamps: U-shaped pieces of 1/2" plywood with 7/8" slots that reach around the plank, wedges cut about 1 in 15, and 1/4" polyurethane tubing set in a groove at the tips so they grip. Make a pile of them, space them close, tap the wedges home.
  5. Pull the hardware. Back out screws and pull pins once the epoxy has cured. If the epoxy has grabbed a screw, one builder (Ross Lillistone, DIY Boat Plans) heats the head with a flat-tipped soldering iron for about 45 seconds before backing it out, so it doesn't snap off in the plank. Fill the holes with thickened epoxy, sand flush, and carry on. Anything you leave in should be bronze or another non-corroding alloy (WEST).

MOAM's shop note: The most common mistake I see is treating epoxy like yellow glue: six bar clamps on a scarf, every one cranked till the jaws groan. Two things happen. The bevel slides, because a slanted joint under pressure wants to move. And you squeeze the joint dry. Pin first, press second, and stop when you see a small, even bead. If you don't get squeeze-out, take it apart and add more thickened epoxy. And the pro trick? Wrap every caul and spacer in clear packing tape before you mix the first squirt. Once the clock's running, you won't have time to go find the roll.

Numbers here come from WEST SYSTEM / Epoxyworks, WoodenBoat and Small Boats Monthly; where a figure is one builder's practice, I've said whose.

Sources: WEST SYSTEM, Bonding and Clamping and Epoxy Problem Solver; WEST SYSTEM Wooden Boat Restoration & Repair manual (8:1 scarf); Epoxyworks, Clamping Basics and Holding Strip Planks in Place; WoodenBoat, Glued Lapstrake Plywood Plank Clamps; Small Boats Monthly, CLC Passagemaker Dinghy; Small Trimaran Design, Bonding Scarfed Plywood; Fly Fishing Traditions, Gluing the Scarf Joints; DIY Boat Plans, Removing Temporary Screws.

MOAM Out.

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