The Hovercraft by James Bull

So, I was looking for a foam core material, suitable for easy cutting and shaping, with good strength, light construction and compatibility with fibreglass resins. I first tried casting expanding builders foam, the idea being it would expand to fill a mould. However this did not give an even consistency, full of large air bubbles and was weak. Common polystyrene foam was next – the sort you’d get in packing and insulation but this was prone to cracking and deformation, and was not suitable for sanding.

Then I came across a model aircraft site which mentioned a new material called ‘craftfoam’ apparently this model enthusiast had used it to manufacture model aircraft wings using a hot wire. And so I found panel systems site, read a little more about the foam – and decided to give it a try. I ordered probably twice as much as I needed so that I could have a play with it and learn what it was capable of first. I made myself a simple hot wire cutter using a guitar string, chipboard and softwood frame and an old variable ac/dc transformer. The foam cuts really well with the hot wire, and with a little care you can cut dead straight sections precisely. With a little improvisation more complex cuts can also be made e.g. the lift-fan duct.

So, I was looking for a foam core material, suitable for easy cutting and shaping, with good strength, light construction and compatibility with fibreglass resins. I first tried casting expanding builders foam, the idea being it would expand to fill a mould. However this did not give an even consistency, full of large air bubbles and was weak. Common polystyrene foam was next – the sort you’d get in packing and insulation but this was prone to cracking and deformation, and was not suitable for sanding.

Then I came across a model aircraft site which mentioned a new material called ‘craftfoam’ apparently this model enthusiast had used it to manufacture model aircraft wings using a hot wire. And so I found panel systems site, read a little more about the foam – and decided to give it a try. I ordered probably twice as much as I needed so that I could have a play with it and learn what it was capable of first. I made myself a simple hot wire cutter using a guitar string, chipboard and softwood frame and an old variable ac/dc transformer. The foam cuts really well with the hot wire, and with a little care you can cut dead straight sections precisely. With a little improvisation more complex cuts can also be made e.g. the lift-fan duct.

I set about drawing up a rough design for the model – and then began chopping foam! As you can see from the pictures this project is still work-in-progress. I have made the basic hull structure, propulsion mount and lift motor duct. A lot of sanding and shaping is required, for which I took hints from a surf board website, as I want a sleeker and more aerodynamic look. So far I have used a sharp craft knife, hot wire, metal files and sandpaper to shape the parts. And used an extra strong pritt stick to attach parts together ( trust me - if applied to both parts, and pushed together hard then left to dry this is very strong).

The next steps will involve removing unwanted foam from the hull to reduce weight even more, adding a R/C gear compartment the basis of which you can see in the images then adding fibreglass or possibly carbon fibre (if I can get hold of some) to the base of the craft and anywhere that might need extra strength. Then a paint job and a skirt and I’ll be off to the lake for a test drive!