Pop-Up Tugboat

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This article is from Issue 63 of Woodcraft Magazine.

Get under way with this bandsaw-built telescoping toy.

When deciding on a toy to make for my grandson, I found myself considering the kind of “pop-up” construction used to manufacture spiral-cut Shaker baskets and the collapsible camping cup I had as a Boy Scout. The technique allows tapered telescoping pieces to lock in place when spread apart, and it worked well for making this toy boat. (Although the project won’t telescope after it’s assembled, the tapered cuts are a quick and easy way to create a boat with curved parts that automatically fit into each other.)

Building procedures and patterns are provided here for this specific design, but once you understand the approach, you can take the helm and get inventive. The trick to making any caricature like this is to observe and distill the characteristics that define the subject. For this project, I studied various boats to identify the elements that said “tug,” and then exaggerated the forms and curves to arrive at this design.

Creating the engine is particularly fun. Use a cartoonist’s eye when looking through your miscellaneous parts boxes or the small parts drawers at the hardware store. Bits of tubing, odd washers, and doohickeys of uncertain provenance can suddenly become intake manifolds, newkular fusion condensers, and carbuncle pumps! (This supercharged three-banger engine sports carburetors of brass tubing.)

After adding any of your own refinements, such as capstans, winches, bumpers, ventilators, ladders, or perhaps a figurehead, it’s time to release your tug from dry dock. 

However, note that this is a DL-class (Dry Land) tugboat. She’ll float beautifully on hardwood harbors where a keel would just get in the way. In water, she’ll capsize. Add a weighted keel and some marine varnish if you want a bathtub-worthy version.

Blades, Test Blocks, And Pop-Up Construction

“Pop-up” construction works because tapered telescoping parts lock up when slid apart a certain distance. That distance is determined by both the amount of saw table tilt and the blade kerf width. Therefore, it’s wise to make test blocks with your chosen blade, especially if you’re experimenting with various designs.

For this boat, I used a 1⁄4" 4-TPI blade that cuts a .050"-wide kerf. (A narrower blade will cut a smaller radius, but it won’t sweep curves as smoothly.) Before starting on the project, I used the blade to make two telescoping blocks, as shown in the photo at right. These showed me the amount of projection I could expect using different saw table angles and revealed the smallest radius the blade would cut. Whatever blade you choose, make sure it’s very sharp, and take some test cuts in scrap to check the results before committing to your project.

Trace the curve of Pattern A onto the side of the block, marking the Length Overall (LOA) and Superstructure (SS) locations.

Prepare the patterns and block

1 Enlarge and copy the patterns on page 41, use spray adhesive to adhere them to manila folder stock, and then carefully knife them out. 

(The patterns are also available at WoodcraftMagazine.com. Click on “Patterns.”)

2 Cut a block of wood to 3 × 31⁄2 × 61⁄2". I used poplar, but soft maple, clear pine, basswood, or other mild-grained wood that’s not too dense will work well.

3 Place Pattern A on a 3" side of your block, aligning the straight sides of the pattern flush with the top and end of the block. Now carefully trace along the gunwale curve while holding the pattern securely. Mark the Length Overall (LOA) and Superstructure (SS) locations (Photo A), and then use a square to extend the marks fully across the edge of the block.

4 With the bandsaw table set square to the blade, carefully cut the curve. This is cut #1 in the sequence shown in Figure 2, and it will create the Hull and Superstructure blanks. Put the Superstructure block aside for now.

Trace the Hull on both sides of the centerline. Use the Deck Pattern D to check that the pinned Hull Pattern isn’t distorted.
Saw to the outermost Hull line with the bandsaw table tilted at 4°.
Aim to leave just the pencil line on the outer perimeter.

Make the Hull

Note: From this point forward, all angled cuts should be made with the table tilting downward at its outer edge and the part being cut on the lower side of the table.

1 Scribe a centerline on the curved surface of the Hull block. Carry the LOA and SS locations across the curve.

2 Pin Pattern B to the Hull blank so that it abuts the centerline and fits between the LOA lines. Trace the inner and outer Hull lines, and then flip the pattern over and trace the opposite half of the Hull (Photo B).

3 Extend the outer Hull curve to the right-hand edge of the block, where shown in Figure 2 to create a lead-in cutline. Now, tilt your bandsaw table to 4°, and make the outer Hull cut (#2), as shown in (Photo C). Then sand away any fuzz on the bottom surface.

Saw as smoothly as possible to the innermost Hull line, leaving just the pencil line on the Hull piece. Don’t back up to correct an errant cut.
Make sure the open end of the centered engine room pattern (C), is aligned with the upper SS line, and carefully trace the shape.

4 Leaving the table at 4°, make the inner Hull cut (#3), as shown in Photo D. Since a good fit between the Hull and Deck depends on a kerf of consistent width, don’t back up to try to correct. At the end of the cut, carefully hold both parts in place while you turn off the saw, and then maneuver the blade free of the kerf.

5 Press the Deck piece downward so that its bottom surface projects about 3⁄8" from the Hull’s bottom edge. The Hull should squeeze the Deck in place when the kerf at the bow is pinched closed. If the kerf doesn’t quite close, sand a wee bit off the Deck perimeter (being careful to maintain the cut angle), or plan on gluing in a sliver later to fill the gap. Any offset at the closed kerf can be sanded off after glue-up.

Align the blunt tip of Pattern E with the upper SS line on the Superstructure block, and trace along the Engine Room curve.
Make the short, straight cut of the Engine Room curve first, and then begin the long curve from the other side of the block.

After making the innermost cut to free the Bridge, saw the outer line to shape the Engine Room. In both cases, enter at the side shown.

Make the Superstructure

1 Scribe a centerline along the convex surface of the Superstructure block where shown in Figure 2. Then square the SS lines across the block to create intersecting lines for locating the horseshoe-shaped Engine Room Top Profile Pattern C. Align the pattern with the centerline and SS lines, pin it in place, and then carefully trace around the pattern, using your fingers as additional hold-downs, as shown in Photo E.

2 Place Pattern E on the side of the Superstructure block, and trace along the aft curve, as shown in Photo F. Set the saw table square to the blade, and make the cuts (Photo G), beginning with cut #4, and then following up with cut #5, where shown in Figure 2.

3 Set the saw table to 3°, and make the two U-shaped cuts that will free the Bridge and Engine Room (Photo H). Start the cuts (#6 and #7) where indicated in Figure 2, with the cutouts on the lower side of the table to ensure correct telescoping.

Tape over your saw throat opening to prevent the freed Bridge Roof from falling into it.
Mark the profile of the Engine Room onto the Bridge, mark a cutline 1⁄4" from the bottom end of the Bridge, and mark the Wheelhouse notch on the top end. 

Make the Bridge

1 To make the Bridge Roof, slice about 1⁄8" off the top of the Bridge section, with the saw table remaining at a 3° angle. Feed the piece, as shown in Photo I, to ensure a Roof of consistent thickness.

2 Raise the Bridge until it’s snug within the Engine Room section. Clamp the two pieces in a handscrew, as shown in Photo J, and then mark the curved profile of the Engine Room onto the rear wall of the bridge, offsetting the line about 1⁄8". Also mark a cutline about 1⁄4" up from the bottom edge of the Bridge to make room for the Engine below. Finally, lay out a 1⁄4"-deep notch for the Wheelhouse, marking its lower end about 1⁄4" up from the top end of the Engine Room section.

3 Use a handsaw to rough out the cuts, and then sand a slight crown on the aft face of the Bridge.

Trace the shape of the Roof onto the end-grain section of the L-shaped Wheelhouse block. 
Use a handscrew to support the Engine Room section so its bottom is square to the table for drilling the portholes one at a time.

Make the Wheelhouse

1 Make the L-shaped Wheelhouse block. The dimensions shown in Figure 2 are approximate, so amend them as necessary to match the measurements of your particular Bridge. Use the Roof piece you sliced off the Bridge to mark the shape on the end-grain leg of the Wheelhouse (Photo K). Then belt-sand the curved face of the Wheelhouse to inset it a bit from the Bridge and Roof, as shown on the boat in Figure 1 and the lead photo on page 36.

2 Use a 3⁄8" brad-point bit in the drill press to bore the portholes in the Engine Room (Photo L). Clamp the piece, keeping its centerline horizontal if you use a drill press. Using the same bit, drill a 1⁄4"-deep hole for the Towing Bollard about 1⁄4" in from the aft end of the Deck.

3 Cut a 3⁄8"-diameter dowel to length to make the Towing Bollard. When inserted in its Deck hole, it should project about 1⁄4" above the gunwale (the upper edges of the Hull). Chuck it in the drill press, and sand a shallow dome on the top end. Then use a small file to turn a groove for the hawser string.

Sand and assemble the parts

1 Lightly sand the Deck, taking care not to completely remove the SS lines, as you’ll need them to locate the Superstructure. (If necessary, use the pattern to reestablish them.) Slide the Hull section up, and mark along its lower edge to demarcate the gluing area on the sides of the Deck section. Apply glue to the section, and clamp the Hull to the Deck with one clamp extending bow to stern, and another clamp perpendicular to the first, pulling the sides in. After the glue cures, sand the top edge and outside of the Hull, easing any corners in the process.

2 Sand the outside of the Engine Room section, and ease any sharp edges on it and the Bridge. Mark the gluing area on the Bridge, apply glue, and slide the Bridge upward into position. If necessary, clamp sideways across the Engine Room to pinch the Bridge in place until the glue dries.

3 Glue the Towing Bollard into its hole in the Deck.

4 Apply glue to the unsanded bottom edge of the Engine Room, and press it onto the Hull between the SS lines. Let the glue cure.

Bore the holes for the brass tubing with the Engine Block dowel and its waste wedge placed on a support block and clamped in a drill press vise.
Clamp the brass tubing within a slotted hole to hold it while you use a cutoff wheel in a rotary tool to slice the end at an angle.

Make the Engine

1 To make the Engine Block, begin with a 5⁄8"-diameter dowel about 6" long for safe handling. Referring to the Figure 1 Exploded View, saw off a 3⁄4"-long wedge that approximates the curve of the Deck. Use Pattern A as a rough guide, and then sand and test-fit. Crosscut the dowel to 11⁄4" long to create the Engine Block.

2 Outfit your drill press with a 1⁄4" Forstner or brad-point bit. Mount the Engine Block and support pieces in a drill press vise (or handscrew), as shown in Photo M, and drill 1⁄4"-deep holes for the brass tubing.

3 Cut the end of a length of 1⁄4"-diameter brass tubing at 45°, as shown in Photo N. Then crosscut the piece so it protrudes 3⁄8" from the Engine Block. Repeat to make two more lengths. Finish up with a light sanding to chamfer the sharp edges, and then epoxy the pieces into the Engine Block.

4 Chuck a 1⁄2" thumbtack in the drill press, and sand it with 220-grit paper to produce a brushed finish. Then drill a hole in the aft end of the Engine Block, and epoxy the tack in place. Finally, apply glue to the underside of the Engine Block, press it in place, and let the glue cure.

5 Tie one end of a stout string to the Bollard, tie a loop in the other end, and get underway. Something needs towing. Just watch out for giant lobsters! 

About Our Author

Ric Hanisch is a designer who enjoys being part of the process, from idea to finished project. He resides at Last Resort in Bucks County, Pennsylvania, where he is an active partner in Art Farm, a collaborative community.


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