Introduction: Make a Hobie 18 Trampoline From Truck Tarp

About: Tim Anderson is the author of the "Heirloom Technology" column in Make Magazine. He is co-founder of, manufacturers of "3D Printer" output devices. His detailed drawings of traditional Pacific I…

Last week I re-tramped my Hobie 16 with sunbrella cloth. Here's a similar method for my Hobie 18 using heavy PVC/Polyester truck tarp material.

These old catamarans are in good shape after years in the sun, but those trampolines just go to pieces.
Here's the tramp before and after some attention from the tool-using ape.

Step 1: Set Up Your Workspace

It takes a few hours to do this, so you might as well be comfortable. I set up a big umbrella for shade. I set it in the centerboard slot. It wobbled around a little, so I wrapped the shaft with bicycle innertube.

Step 2: Take Pictures of How It Was

Once again, take a bunch of pictures of the original configuration.
If your boat has no tramp at all, you can refer to these.

Step 3: Remove the Old Tramp

Unlace your old tramp and slide it out of the slots in the extrusions.
To save time you could cut the lacings.
I re-used mine, but your tramp will look a whole lot better with new rope.

Step 4: Lacing Strip

Hobie calls the narrowest piece of cloth the "lacing strip".
This one is cracked and weak so I'm going to wrap it with cloth.
I keep it inside the new cloth so I can lace through the grommets.
Not having to buy and set new grommets is what makes this method so cheap and fast.

I'm fortunate to have a heavy sewing machine handy. As long as I don't hit any grommets with the needle the sewing goes well. When I'm done sewing I slide it back into the extrusion and cut slots through the grommet holes.

It's strong but it looks like crap because it's scrap cloth with crazy sewing and cut threads all over it. Don't worry about that.
As soon as the lacing is on there, the human eye will be mesmerized by the lacing and the cloth will be a blue blur. Have you ever wondered why corsets are so popular? To look at anyway?
Kinky psychology!

Step 5: Trace the Tramp Half

You want your new tramp half to be SMALLER than the original one. It spent years getting stretched out. So don't copy the old tramp exactly, push the edges in a little bit when you're tracing it.

I've got a million pounds of scavenged truck tarp material, so I decided to use that.
PVC manufacturing is evil, don't buy any new stuff, but the planet loves you for scavenging.
This fabric is the same stuff we used to make the new skin for the Cozy Boat
It's heavy PVC laminated onto polyester cloth. It's a "gym floor cover" from MIT. They used it to protect their basketball court from spilled wine and high heels during wine-and-cheese events.
It's the same stuff trucks use to cover their loads of dirt, rocks, earthmoving equipment, etc.

Lay the tramp half upside down on the cloth. Trace it. Cut a few inches outside the lines as shown. Cut all the way to the tramp corners as shown.

Step 6: The Pocket

There's a big pocket toward the front of each tramp half to stow ropes, waterbottles, etc.
I thought I'd sew it on first. That was a mistake. It should go on last so you can sew the flaps on the underside of the ttramp down without sewing the pocket closed.

Step 7: Hatch Marks

Draw some hatch marks onto the old tramp and the new cloth so you can make sure they aren't sliding around relative to each other. This is an alternative to pinning them together.

The two surfaces of the tarp are different. One side has more texture from the internal fabric. The other side has a thicker, smoother coating. Figure out which surface you want up. I opted for the thick surface up for longevity.

Step 8: Sew Around the Edges

Sew the edges of the old tramp to the new cloth. See that folded-over flap at the bottom? That was a mistake. The stiff cloth and hidden hatch marks meant I couldn't keep the cloth from sliding around. I had to cut that stitching and do it over.

Step 9: Cut Off the Rotten Cloth

Cut away the rotten old cloth from the middle of the tramp. You only want the edges.

Step 10: Sew Down the Flaps

Fold the edges of the new cloth over and sew them down. Notice that I just sewed over the pocket. That was a mistake. The pocket shouldn't have gone on til after this.

Step 11: Foot Strap

The footstraps on the old tramp were shot, so I used a piece of seatbelt. There are reinforcing patches of cloth on the underside of the tramp to keep the stitching from pulling through when gripped in wipeouts.

Step 12: Finished Tramp Half

Here it is!
This is the second one, so I didn't stitch over the pocket and it's just generally better. But this is just supposed to get the boat on the water, not impress obsessives with displays of compulsive craftsmanship.

Step 13: Installation!

The edges of the new tramp are a lot thicker than the old one. Spray everything with soapy water to lube it up. Grip the edge with a clamp so you can pull hard. The tramp is oriented upside down as shown. Slide it into the slot at the front of the front beam.

Step 14: Side Track

Fold the tramp half under the front beam and feed it through the dolphin striker strut.
Spray soapy water on everything and slide it into the extrusion on the hull.

Step 15: Slots

Stab through all the grommets to make way for the lacings

Step 16: Lacing

Use needlenose pliers to pull the cord through the grommets.
Lace up your tramp.

Step 17: Go Sailing!

Lace it tight, and

Go Sailing!

For comparison, here's the Hobie 16 trampoline I re-did with Sunbrella fabric.