Stove-top Dehydrator

This is just a quick instructable on how to make a wooden dehydrator that sits on a slow-combustion heater (I’ll probably adapt it to solar heating next summer).

The basic design uses rectangular frames for the trays and base (which simply has aluminum legs too). The initial lid was made from pine planks that were biscuit-joined, but that was complicated to build and shrunk as it dried so I’ve gone for a 12mm plywood lid instead.

With a wooden contraption on a fireplace, you will need to keep an eye on it, don’t leave it unattended!

For this really simple design, all you’re going to need is:

Fly-wire

Staple gun and staples or equivalent

Hammer

18x40mm or similar planks

20x1.25mm nails

Sandpaper

Wood glue

Plywood

Latches (and screws to mount)

Handle

Saw (of some sort, I used a drop-saw)

Something to make the ‘Jig’ out of eg. scrap ply and some MDF or chipboard

Super simple, all you need to decide is the depth and width of your dehydrator - I went with a square 320x320mm design but a 280x350mm rectangle would have fitted my stove better. You don’t need to decide on the height of the dehydrator as you can make as many or as few trays as you like!

As can be seen, you can fit quite a bit of apple in a dehydrator this size, around two large apples a tray.

If like me you have a slow combustion with a raised chimney take-off, you may need to adjust your dehydrator’s leg’s height to allow it to clear the raised mount. (legs are not pictured)

Because this project calls for multiple identical frames for the trays and base, it made sense to make a ‘Jig’ – a piece of scrap chipboard that I then screwed some ply to. This jig allows you to get the frames almost perfectly square, ensure that any discrepancies are uniform, and provide something to hold it while you whack it with a hammer.

Find a piece of scrap at least 100mm bigger length/width than the frame size you’ve decided on, mark the outer dimensions of your frame onto it, then attach the strips of ply down each side, along the line.

Ta-da! Basic jig made!

Now that we have the jig made we can start pumping out frames, to do this, simply cut your sides (mine were all 320mm long) and using a drop-saw or some (preferably powered) tool, cut the ends on a 45 degree angle. Need I say be safe around tools?

Once you have the angles cut, you’ll need to test fit the pieces in your jig – depending on the accuracy of the angles, they should fit pretty well. If the frame is a little too big for the jig, sand the angles on one or two sides until it fits well. If the Jig is too big, shrink it by moving the ply pieces inwards, making sure it stays square.

If the jig is considerably too small or big, consider reconsidering your method of cutting the angles for the frame’s sides.

Once you’ve got it working well, and the sides all fit, place glue on both angles of two of the sides, fit them back into the jig, and start fixing the corners with fine nails. I used two nails on each corner, one from each side, perpendicular to each other – this prevents the corners from coming apart as if you pull in the direction of one nail, the other is perpendicular and won’t pull out.

Now that all the corners are secured, you can remove the frame and make another! You don’t need to keep in in the jig to let the glue dry as the nails will hold it.

For this step I opted for the use of a staple-gun to avoid the fiddly job of using tiny U-nails.

I got some extra help to hold the mesh on the tray while I marked it with chalk. (Black markers on black aren’t super visible, white chalk on the other hand…) Once marked, I simply cut the square out making sure it was at least a few millimeters smaller than the tray so it wouldn’t extend past the tray when stretched tight and secured.

To secure the mesh I again got some extra hands to hold it tight while I carefully stapled all the way down each side. I found that 5 staples a side, with an extra one bridging each corner was strong and looked neat.

Repeat for all the trays!

The aim was to make a dehydrator that could be carried by a handle on the lid - to do this the trays, base and lid were attached together with some lightweight latches. I used an alternating latching method to give my slightly-larger-than-ideal latches space to be attached. (I couldn’t quite fit both the top and bottom parts on one side of the tray)

The trays also attach onto the lid and base with the same method so you can add trays, or simply use one - just make sure that your latches are perfectly centered on their respective sides!

I mentioned in the intro, I initially made the lid from pine planks that were biscuit-joined to the required width, but that was complicated to build and shrunk as it dried so I’ve gone for a 12mm plywood lid instead.

With both lids, they were pretty rough & raw so the first step was to sand them back so I could mark them without destroying the pencil!

The lid needs lots of holes to allow air flow up through the racks, which dries the contents. To ensure I got the hole’s layout symmetrical I used what I had on hand, the disk from an orbital sander. This gave me eight 9mm holes to I used six groups of eight.

Once the holes were drilled, I used a counter-sink bit to remove burs then gave both sides another quick once-over with the sander.

My particular handle attached with two M3 bolts through from the underside, depending on what handle you use this will vary but the idea is similar, just make sure you centre the handle!

For the base I took one of the frames that could also be a tray, and drilled four 10mm holes in the ‘bottom’, in a pattern that allowed me to fit the oversized dehydrator onto the slow-combustion.

Into the holes I stuck lengths of 10mm aluminum tubing, left over from another project. They conduct heat poorly enough that with a 150mm length the top of the legs is not too hot, and the radiant heat is such that neither is the wooden base.

With a wooden contraption on a fireplace, you will need to keep an eye on it, don’t leave it unattended!