Introduction: Sewing Your Own Boat Cockpit Cushions

Picture of Sewing Your Own Boat Cockpit Cushions

When we bought our sailboat, it had yellow on white (or white on yellow, depending on how you look at it) striped cockpit cushions. While the Mrs. loved the bright colors and cheerfulness it added to the cockpit area, the guy who had to constantly clean them (me) due to the high traffic area was less enthusiastic.

Since we were going to doing other canvas projects on the boat, we decided to tie them all in together with a matching color scheme. We decided that Forest Green would be a classic looking color that would stand up to the traffic and not look dingy after only a few days of use.

As with so many other things that I've had to learn to do, I searched on YouTube for a tutorial. Sailors know that Sailrite is a great company that produces excellent videos on how to do all kinds of great projects with their products, and I made the sail for our little wooden sailboat project from one of their kits. Their boat/box cushion video was the inspiration for my project and this Instructable.

I'm entering this Instructable into the "Sew Cool" contest, so please vote for me above!

EDIT: Our boat was hit by two hurricanes in two weeks, Irma & Maria, in Puerto Rico. It looks as though our boat has survived, so hopefully our new cockpit cushions will really jazz up the boat. Wish us luck!

Step 1: Making Templates

Picture of Making Templates

Before I could figure out how much material to order, I had to make templates, to give me the measurements I needed to plug into Sailrite's fabric calculator.

This was the easiest part of the process. I just bought some thin plastic painter's tarp and taped it down into the area I needed to be covered by the cushion. I made notes like Port/Starboard as needed and which side the zipper was supposed to be installed so it's hidden on the final product.

Using a regular Sharpie marker, I roughly traced out the cushion shape. I sweetened up the lines later with a straight edge as needed. Then I cut out the template, staying well outside the lines. Using a 48" straight edge, I optimized the straight lines and carefully hand drew the rounded corners. If needed, I could have also traced circular objects around the house that had the right radius.

Two of my cushions ended up roughly 64" x 18" and the third was 60" x 18". I plugged that into Sailrite's fabric calculator as shown above, where I selected Cushions -> Box Cushions.

The calculator needed to know a few things to work. First were the dimensions of our cushion, but also how thick of foam I'd be using. I went with 2" thick. Also, the width of the fabric off the spool, which I got from the fabric's product description. In this case, it was 54" (60" is also common). For the matched set of cushions port and starboard, I put in quantity 2 since they're the same size and here are screen shots of what it spit out. It even showed me how to nest the pieces to optimize the use of my fabric!

Then I just added it to my shopping cart...

Step 2: Gathering Materials & Tools

Picture of Gathering Materials & Tools

I started out by watching the Sailrite video a couple of times to familiarize myself with the process. Then I watched it again, pausing where I needed to to generate a shopping list. I already had a Brother CS-6000i that I had purchased previously to make the sail for my son's boat, so that was already taken care of.

Here's the shopping list:

and any various seam rippers, pins, tape measures, erasable fabric pencils, pencil sharpeners, scissors or piping foot you may need for the project. For a couple of hundred dollars, I was able to get all the materials I needed to make a thousand dollars' worth of cushions.

Now I just had to wait for the goodies to arrive...

Step 3: Cutting Top & Bottom Plates

Picture of Cutting Top & Bottom Plates

Sailrite's video has a great table of contents that will take you to the beginning of each step. It was time to cut the plate(s) for the box cushion(s). I was faced with a dilemma here. If I made the top and bottom out of the green fabric, I could flip the cushions over, but that would trap moisture inside. If I made the tops out of the fabric and the bottoms out of mesh, they wouldn't be flippable, but they would breathe and dry out much easier/faster. I went with the mesh option. Regardless, the top and bottom plates are exactly the same size, but NOTE:they're not the same size as your template!

I needed to make my plates 1/4" larger in all directions than my template. That way, when I used a 3/8" seam allowance, my cover would fit nice and snug over the foam.

I traced the enlarged outline around my template on the top plate (fabric), cut it out, then I used that to create an exact copy for my bottom plate (mesh).

I oriented my cuts according to the diagram from the fabric calculator. I was also aware of keeping the right side out if my fabric had a good side and a bad side. The fabric I'm used didn't have a good side, so it was a little bit easier to manage.

For my port/starboard matched set of cushions, there was just a slight difference between the two templates, but since they were made out of clear plastic, I was able to lay one on top of the other and trace out the optimized average of the two. I then used that one template to make both cushions.

The UV resistant fabric is subject to fraying if you just cut it with scissors, so I needed to use a hot knife or soldering tip to cut/melt the fabric. To keep this from ruining my work surface, I placed one metal ruler beneath the cut line and used the second metal ruler on top as a straight edge. I made sure to place the top ruler inside the cut line, so that if the blade slips, it goes out into the spare fabric and not into my top plate area. I discovered that cutting about 1" per minute to make sure the cut is clean without doing any additional melting.

The bottom plate mesh material could be cut with scissors, so I just laid the top plate on the mesh material, traced it out with a fabric pencil and cut it out. The mesh material also does not have a good side. I now had matching top and bottom plates.

Step 4: Making Your Piping/Welting

Picture of Making Your Piping/Welting

To determine the width of fabric I needed for my piping, I multiplied the diameter of the piping I bought, times Pi, then added a generous seam allowance. My piping was 5/32", so 5/32" x 3.14 = 1/2" + 5/8 x 2 = 1-3/4". I then "cut" (using my hot knife) really long strips at that width.

I measured the perimeter of the template. This is the minimum of piping I'd need to wrap around the top seam. I added about 10% for safety. For example, my cushion was about 150" around, so I made up about 165" of piping. Some cushion designs have piping around the top plate and bottom plate (usually cushions you can flip). Since my cushions weren't flippable, I only used piping on the top plate.

With the hot knife, I cut a 1-3/4" wide strip the length I calculated above (or the length of the edge of the fabric I purchased). I would most likely need to splice in a filler strip, so I will cover that later.

Now for some actual sewing in this sewing project... I installed the cording foot on my sewing machine according to the directions. I loaded a bobbin with my color-matched UV resistant thread and threaded my machine. I put my sewing machine on 2.5/5 stitch length. Then, I folded my strip in half, length-wise

If my strip of piping was longer than the perimeter of my cushion template, then I would've started in the center of the back of the cushion. If not, then I still wanted to start in the back, but probably off-center so the splices would still be on the back of the cushion.

I laid the "cut" edge of my piping parallel with the "cut" edge of my top plate, then I stitched them together, "cut" edges out. At this point, I was making a "good" side, so since I was making a matched set of cushions, I made sure they were mirror images of each other at this point. I didn't want to make two "starboard" cushions. Also, the direction I would be feeding the two pieces through the sewing machine might be a factor, so I pinned the pieces together to mock it up and see how it went.

I left about 3" of piping loose to use later for the splice and start stitching. Then, I just followed along the edge and around corners as needed. When I got to a corner, I left the needle buried in the fabric 1/2" from the edge, raised the foot and rotated the cloth as needed (some of my corners were more than 90°), then I lowered the foot and resumed sewing.

To splice the piping, I cut the end of the next piece flat (so the fabric and piping cord were even). Then I cut the original end of the piping so the cord was 2" short of the fabric. I folded the fabric over to form a "taco", then laid the next piece into the "taco" with the cord ends butted up against each other. I sewed across the folded "taco" and continued down the edge of the top plate.

Step 5: Making the Boxing & Zipper Plaque

Picture of Making the Boxing & Zipper Plaque

Next, I needed to make the sides of the cushion (aka the boxing). Assuming this was a four-sided cushion, I'd need to create 3 strips of fabric that would be wide enough for the foam thickness I'd be using and the same length as the corresponding sides of the top plate sides. For the 4th side, which has the zipper installed, the additional stitching in the zipper would tend to shrink the length of the strip a bit along the direction of the stitching. To compensate for this, I measured the zipper side of the newly assembled top plate (the edge with the piping splice) and multiplied by 1.0125 to get the length. In my example, the back of the cushion measured 60.5 x 1.0125 = 61.25". That's how long of a strip I needed to make the zipper plaque.

The other three sides were 16.6", 17" and 55.5" long (my cushions weren't simple rectangles).

NOTE: The above is the technically correct way to do this. I actually made all of my boxing strips 4" too long. This allowed me to cut and stitch the corners perfectly, in situ, while I was stitching the boxing to the top plate.

Now let's talk about how wide to make the strips. For 2" foam, I made boxing for three sides of the cushion by cutting 2.5" strips (thickness of foam plus 1/4" on each side). With the seam allowances of 3/8", this would wrap the fabric tightly around the foam to eliminate wrinkles in the final product.

For the zipper plaque boxing, I measured the width of the zipper I selected (in my case 1.5"), then added 1/4" on each side, then added the width of the zipper. So in my case 2" + 1/2" + 1.5" = 4".

Now with my hot knife, I cut out three strips of boxing of 2.5" x top plate length and set them aside. Then I cut out my zipper plaque boxing at 4" x 61.25".

I folded my zipper plaque boxing in half down its length. I could have even ironed the folded fabric flat to make it behave better. I took my zipper width measurement (1.5") and divided it by 2 to get 0.75". I made a mark 0.75" from the folded side and made a tack stitch (set sewing machine stitch length to 5/5). MAKE SURE TO SET IT BACK TO 2.5/5 WHEN YOU'RE DONE!!!

If I had an edge/seam guide for my sewing machine, now would have been a good time to install it and set it to the 0.75", but the one I bought didn't end up working. No biggie. I made sure I didn't do any reversing/reinforcing of this tack stitch as I'd be removing it later. Now using sharp scissors, I cut along the folded edge, right down the center of the zipper plaque boxing strip.

I opened the flaps so I could just cut and fold them back flat onto the long sides. I could also iron this flat to help it behave. With my sewing machine back at 2.5/5 stitch length, I sewed the short flaps down flat onto the long sides, making sure to reverse/reinforce at the start of my stitches. I established where along the length of my zipper plaque I wanted the actual zipper to start (no need to have the zipper go all the way to the corners of the cushion), so a good 6" - 12" would work to stuff the foam in later. I sewed along the outside edge of the zipper facing to allow the zipper and flaps enough room for the zipper body to slide back and forth. I could cut the zipper to the appropriate length and feed the teeth back into the slider as needed to re-zip the zipper. I made sure to do some reversing/reinforcing when my stitch meets the zipper facing.

I cut off both ends of my zipper facing because they had large stops on them that would interfere with the sewing and also complicate which way the zipper body should be sewn in place. I could always pull the teeth apart and feed the teeth back into the body to fix the zipper later.

When I got ready to add the zipper to the plaque, if I had done my calculations correctly, the zipper should be almost exactly the saw width as the two flaps. This also meant that the center of the teeth should be down the center where my tack stitch was. As I started to stitch over the zipper facing, I needed to lift the foot and slide the zipper facing underneath, then lower the foot. I made sure to do some reversing/reinforcing at the start and end of the zipper. I tried to keep my stitches perfectly parallel along the entire length of the zipper as this will show on the outside of the seat cushion. I kept checking my folds to make sure I had not accidentally stitched across areas I didn't want. Ripping out stitches is a tedious and frustrating process.

I sewed all the way to the end of the zipper, then did some reversing, then continued sewing to the end of the plaque and did some more reversing.

Next I repeated the entire process by flipping the zipper plaque around and sewed down the other edge of the zipper in the same fashion.

Next I installed the zipper sliderby pulling a couple of inches of the teeth apart and inserted them into the grooves on each side. I kept in mind I wanted the zipper pull toward the outside of the finished panel. I zipped the slider all the way down to the other end of the zipper, but made sure to stop short of unzipping the far end otherwise I'd have to reinstall the slider all over again.

Next I made two strips to reinforce the ends of the plaque where there's no zipper. My strips were the same width as the zipper (1.5"). I sewed those from the good side, over the previous stitching, to lock them in place.

I was afraid of sewing over the zipper teeth as stated in the instructions, but that has the side effect of allowing your zipper slide to slide out. I fixed that later. I didn't forget to sew across the zipper plaque too to reinforce the patch. I did this by leaving the needle buried, lifted the foot, rotated the plaque 90°, lowered the foot, then reversed and moved forward to give a lot of strength at the end of the zipper. I repeated this for the other end of the zipper plaque.

Now for the payoff! With the seam ripper, I cut all those tack stitches along the good/front side of the zipper (between the cross stitching) to liberate the zipper and the cover flaps. Afterwards, I removed all those pesky cut thread ends to see my nice zipper placket (then I cleaned up with a DustBuster). This was why I set the sewing machine to 5/5 stitch length.

NOTE: I was very careful, to NOT SLICE the flaps/placket or all my work on the zipper plaque boxing would be ruined and I'd have to spend an hour removing the zipper to make another one.

Before proceeding, I hand stitched over the ends of the zipper teeth on both ends to lock the slider in. This way I wouldn't damage the needle in the sewing machine.

Step 6: Sewing the Boxing to the Top Plate

Picture of Sewing the Boxing to the Top Plate

Next, I stitched my zipper plaque and one side of the regular boxing together on one end, about 1/4" from the ends by placing the "good" sides together. I reversed back over it to make it nice and strong. NOTE: This immediately created interior/exterior sides of the boxing strips. I kept this orientation consistent. Please note that from here on out, the zipper plaque boxing will be treated the same as the other strips and should be about the same width after the previous step is complete, so will be referred to as just "boxing".

Technically, the instructions say to stitch all the boxing together to form the perimeter of the cushion. To reduce/eliminate the problems with the corners lining up several feet worth of stitching later, I tried stitching the boxing strips together only when I had stitched the previous boxing section to the top plate. This caused a bit more fiddling with awkward parts while I was cutting and stitching the corners because the top plate was already attached and in the way, but my corners landed exactly where I wanted them to.

I kept in mind that when stitching the boxing to the top plate, I could start from any given corner and go either direction. However, only one direction would probably fit easily through my sewing machine.

As I sewed the boxing to the top plate, I made sure a wrinkle from the top plate didn't accidentally get sucked into my stitches, requiring me to rip out a bunch of stitches.

So I could either sew all the boxing together, then sew that sub-assembly to the top plate or I could use my method where you sew on a boxing panel, then see where you land on the corner, cross-stitch another boxing panel to the end of the previous one in the correct location to land on the corner and proceed. If you choose to use the latter method, make sure to stop your stitches a few inches from the end to give yourself enough room to cross-stitch the corner.

If you have to sew the other direction around the top plate, it's a simple matter of turning the assembly over. For example, I had the top plate on the bottom and put the boxing on top to stitch one panel in the direction easy to fit in the sewing machine. Then from that original corner, I stitched the opposite direction, but I flipped the fabric so the boxing was on the bottom and the top plate was on top. It's easy with the cording foot to slide it along the piping so I only had to worry about the seam allowance on the boxing.

Some corners were pretty difficult to get through the sewing machine, so I just stopped short and hand-stitched the corners.

Step 7: Attaching the Bottom Plate

Picture of Attaching the Bottom Plate

We're in the home stretch with the sewing part. This step was very similar to attaching the boxing to the top plate. I just had to make sure I:

  1. Started sewing the bottom plate in the correct orientation so that the good sides were together and in my case the cushion wasn't symmetrical, so I had to make sure the correct faces were sandwiched.
  2. Oriented the sub-assembly so that I could run it through the sewing machine easily.

Once again, I hand-stitched the corners as needed. I started with matching up my corner of choice and went to town.

Note, there was no piping to act as an edge guide for the sewing machine foot, so I had to keep my 3/8" seam allowance under control manually.

My cording foot was 3/8" wide, so that helped as an edge guide. I made sure the bobbin was fully loaded before sewing the bottom plate to the boxing.

Also, there were more layers for a wrinkle to get caught up in the seam so I had to be careful to manage the spare fabric.

A helpful hint may be to make one entire cushion first, then learn from your mistakes (instead of making them all at the same time). My second cushion turned out MUCH better.

If you can, make sure the end of your bottom plate/boxing seam ends up on a back corner, just in case.

Now for the BIG PAYOFF!!! I turned the whole thing right-side-out!!! I had to unzip the zipper to do this.

Step 8: Stuff It! With Foam

Picture of Stuff It!  With Foam

I now had a very nice looking, if a little hollow-looking, cushion. I made sure I didn't accidentally stitch some areas that I didn't mean to, etc.

I was really tired of sewing at this point, which was good, since I was done. Next, I focused on the foam insert. There are a few different types of foam: DryFast, closed-cell and polyurethane. Everybody will tell you that the poly foam is just a sponge (and they're right), but it's also less than a third the price. Since I went with a mesh bottom plate, I decided to see if I could get away with using poly foam. If it doesn't work out, I can always just replace it with the good stuff and I'm not out much money and very little effort. Our boat is in the Caribbean, so it gets rained on every day, but it's also very warm, so I'm hoping they'll if not dry out, not mold like crazy.

Regardless of what kind of foam you go with, you'll still have to do the following steps based on the dimensions that the foam comes in. My foam came in 24" square pieces, so I used the spray adhesive on the edges to make up one large foam blank large enough for one cushion (sorry no pics, my hands were covered in adhesive).

Once that cured, I took my original template and added 1% to each length (but not less than 1/2"). For example, my long side was 60.5", so 1% of that is 60.5" x 0.01 = 0.6", which is larger than 0.5" so I was fine. I made sure I didn't add this to both sides as it really twists the cushion once you put the cover on (don't ask me how I know this).

I laid my template out on the foam blank and added the 0.6" to one side and the top of the template (so I didn't double up). Then using a Sharpie marker, I traced out the profile of my cushion.

Using my electric kitchen knife (bought specifically for this project), keeping the blades vertical and square to the face of the foam blank, I cut out the profile along the Sharpie marker outline. Once I was happy with the cutout and the edges were nice, smooth and square, I stuffed it all into my newly made cover. This was a bit tricky and probably the most stress my stitches will ever encounter. I've heard that if you spray the foam with silicone, it will slide in easier but I didn't bother with that. The first thing I did was grab the far corners and shove them into place, then finesse the rest of the foam to fit. I made sure to try and align the top corner of the foam to the piping for a nice clean look.

Once I was done wrestling with it for a few minutes, I got the edges and corners all lined up, I zipped her up and voila!

We're going to have to wait for Puerto Rico to recover from the hurricanes enough so I can fly down with the cushions and a bunch of other stuff we need to get our boat set back to rights. You can totally make your own boat cushions, whether its a trailer sailor or an ocean cruiser. Best of luck with your boat cushion project!

Midnight Maker out...


DIY Hacks and How Tos (author)2017-10-02

Nice. That is probably the only way to get a cushion that fits properly.

About This Instructable




More by Midnight-Maker:Sewing Your Own Boat Cockpit CushionsHeirloom Quality Quartersawn White Oak Limbert Table #240 w/ Authentic Ammonia Fumed FinishFlat-Pack Picnic Table From 1 Sheet of Plywood
Add instructable to: