How to make fitted sheets for boat mattresses

OK, so this is definitely the most random post ever on this blog. If you don't own a boat or if you already know how to do this, just skip this post. But maybe there are some of you boat owners out there who is wondering how to make fitted sheets for the irregular shapes that boat mattresses/squabs are. And it's actually really easy and it also makes it much easier getting into the storage underneath the bunks if the sheet fits nicely as opposed to a loose sheet just wrapped around a mattress. I'll do my best to explain how to do it even if you don't have much sewing experience, but a bit of knowledge definitely helps.

Sophia's quarter berth which is a cosy long double. The squabs are split in two, making it easier to get into the storage below. The front squab features a complicated corner, more about that at the bottom of this post

It's easiest to do if you have the squabs with you where you're sewing and a nice flat area on which to lay it down, which pretty much excludes being on a boat unless you have a LOT of floor space. Originally I did ours back in Christchurch when we were house sitting and were storing the squabs there anyway as I was painting everything inside Sophia. I did two for the two saloon bunks (with lee cloths where we normally sleep while underway) and two for the quarter bunk where we also slept on the first long trip up to Tonga, but since then it's mostly just storage, as it's the least airy (and therefore stuffy) bunk on the boat. A shame, cause it's really cosy. I did three for our v-berth as that's where we sleep when at anchor, and therefore the far majority of the time. But they had gotten quite yucky from our dirty sweat (no showers and hot climate!) and while in Denmark visiting my family I made three new ones, obviously without the squabs, but just with measurements.

If your sheet fabric is new, always wash it first (and tumble try if you think it will be tumble dried later on) to pre-shrink the fabric. I have used a mix of new sheets, second-hand sheets and cheap fabric to make mine. I have made a drawing below that shows how to cut the fabric (red) around the squab (white). Put down the fabric, and put the squab on top with the top side facing the sheet. If your sheet fabric has a right and wrong side, place the right side facing down (the side you'll sleep on). Basically you just extend the lines from the sides and cut out the corners, the picture below does a much better job of explaining that than I do!

How much to cut away? It depends on the thickness of your squab and how much fabric you have, but you want at least the thickness of you squabs and ideally some more. Roughly 30 cm, try and make it even all around the squab, especially the corners.

Most squabs most aren't symmetrical, for example if one end is wider than the other. One symmetric example is our v-berth. If the squab you're doing is not symmetrical, then you need to pin the corners so you know which side is. If you don't know what I'm talking about, just pin it anyway, better safe than sorry. Basically try to imagine which side of the sheet is right and wrong (or inside and outside) and then you pin the wrong side (where the seams are). Again, the photo below explain much better than I do. For your information, our squab covers are red with a (cheaper) grey backing. You only need to pin one corner to show you which side of the sheet to do the sewing on.

pinning the corners together so you know which side is right and wrong. It's enough to do this on just one corner of your sheet

Now you're ready to start sewing. If this sounds complicated look at the picture below which pretty much explains all the steps in one photo.

1. zig zag: most fabrics unravel, so first you need to zig zag all your edges. Zoom zoom is the sound of your machine sewing all these straight edges.
2. sew corners: next you sew the corners together, those cut-outs you did when it was laying flat, also see photo above.
3. fold: then you make a fold where the elastic is going to be (and therefore the width of the safety pin you'll use to insert said elastic)m, approx 2.5 cm. If you're the super pedantic type who cares about how the back side of your sheets look, then make two folds, but it's harder and you need a bit more fabric. Obviously I don't care. Remember to leave a small hole where you're going to insert the elastic. A good trick is to start by a corner and fold all the corner seams the same way, which will then be the way you insert the elastic, the safety pin will run much smoother that way.
4. insert elastic: I insert the elastic after the sewing using a safety pin (see pic), but others may want to insert the elastic while sewing, I just find I can't sew as fast then and then the time difference evens out anyway. Tighten the elastic until it seems right and either tie a know or just sew the ends together. For the sheet in the picture below I made a relative small hole and didn't even bother to sew up that seem after I had inserted the elastic. It makes it easier if I later need to tighten the elastic or change it for a new elastic (lesson learned: don't used old elastic from old sheets, they dont' last as long).

First you zig zag edges (the bottom right hand edge was the existing finish from the new sheet I was using, so I just kept that edge). Then you sew up corners seams and finally make the elastic pocket/fold. The safety pin is about to be inserted the same way/direction as the corner seams are folded down.

If you have complicated squabs like the one in the first photo, it does, well, complicate things. For that one I ended up inserting extra fabric, but I can't really explain it in words, it's easier in real life to just fiddle around and find a solution that works for you. Maybe you can tell from the photo below how I did, although you need a bit of imagination. Basically I inserted some extra fabric. The second photo shows what a squab with fitted sheets looks like underneath and also the complicated corner with extra fabric.

Phil holding up the sheet with the complicated corner, before elastic was inserted. Also note the Q I had sewn onto it, indicating it was for the quarter berth. I did S and P for the two saloon bunks' sheets, even in green and red thread :-)

What a fitted sheet looks like from behind. This also shows the complicated corner with extra fabric

Making new v-berth sheets on my parents's floor with just measurements. I cut all three layer fabrics in one go, as I knew exactly what I was doing and was certain it was correct, but I wouldn't recommend it the first time you try making a fitted sheet. Our v-berth is a king size at the widest point, so I just bought IKEA king sized flat sheets. The left hand corner at the bottom wasn't quite wide enough, but I still managed OK.