Dave Higham
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Radius dishes are fairly expensive to buy and very messy to make if you make them, as most do, from MDF using a router or sander and dedicated jigs. Here is another method of making a dish which is cheap, clean and easy and you don’t even need a router so you don’t need to make jigs. The only disadvantage I can think of is that it involves a little math, although if you have a CAD programme you can even avoid that. I should mention that this is not my idea. I saw something similar a long time ago on another forum but I can’t remember where or who posted it, otherwise I’d give him credit.
What this method involves is forcing a thin sheet of MDF into a spherical dish by screwing it down to a heavier rigid base with a series of spacers between the two. Here’s a drawing of a section through the dish showing what I mean.
Using the formulae you can decide how many spacers you think you need and at what radii (r) and calculate the thickness they need to be using the second formula. If you have some strips of wood that are close to the required thicknesses, you can use the first formula to calculate at what radius to place them.
If you have a CAD programme you just draw it out and the programme will tell you how thick to make the spacers or where to place them.
So having done the math, I prepared the materials and this is what they looked like.
A piece of 1¼” particle board (offcut from a kitchen worktop). 16” diameter seems to me to be big enough for any size of ukulele.
A piece of ¼” MDF
Strips of wood for spacers
Woodscrews
I taped the strips together and marked them at 1” intervals, then drilled clearance holes for the screws in the centre of each section.
I then sawed the strips down the middle (the brass rod was to line them up, I didn’t saw through that!).
What this method involves is forcing a thin sheet of MDF into a spherical dish by screwing it down to a heavier rigid base with a series of spacers between the two. Here’s a drawing of a section through the dish showing what I mean.
Using the formulae you can decide how many spacers you think you need and at what radii (r) and calculate the thickness they need to be using the second formula. If you have some strips of wood that are close to the required thicknesses, you can use the first formula to calculate at what radius to place them.
If you have a CAD programme you just draw it out and the programme will tell you how thick to make the spacers or where to place them.
So having done the math, I prepared the materials and this is what they looked like.
A piece of 1¼” particle board (offcut from a kitchen worktop). 16” diameter seems to me to be big enough for any size of ukulele.
A piece of ¼” MDF
Strips of wood for spacers
Woodscrews
I taped the strips together and marked them at 1” intervals, then drilled clearance holes for the screws in the centre of each section.
I then sawed the strips down the middle (the brass rod was to line them up, I didn’t saw through that!).