Actual progress, using real tools

This weekend marked a great occasion; I started real work on the hovercraft!

I picked up some foam to use for practice cutting and to verify that I can cut with the precision I want to be able to make the hovercraft.  The main foam I have is 2" thick "rigid insulation" according to Home Depot.  I was able to pick up some small squares of 1" foam which fit in my car more easily.

I turned one of them into a scale model of what I'm thinking of building for the hovercraft. You can see the two model layers at 1/6th scale.

Scaled layouts for the glue-lam foam layers

The main vehicle will be 3 layers like this.  And I'm planning to stick to the very easy to build size of 6'x12' which means that I just need to split a few sheets of foam in one cut.

Upcoming will be to determine a good way to cut the through hole for the lift fan.  Also I will need to experiment with gluing the foam and plywood.  I also picked up some small pieces of plywood for testing, as well as aluminum angle iron.

In doing the above I started exploring cutting techniques.  I've got lots of pictures below with descriptions.


Here's some of the cutting techniques I explored.  

I read online that sharpening a putty knife works well.  I ran into this Flush Cut Pull Saw which has the same properties of being a flat piece of metal and not tapered which is better for cutting deep into the foam.  However you can see below that the blade made a mess of cutting.  The teeth all dug in and created lots of

Messy cutting with a pull blade saw. 

Lots of detritous

Next I broke out the box cutter.

Cutting with a dull box cutter

As can be seen in the photo the dull box cutter did even worse.  But as anyone who's worked with box cutters/exactos on foam core knows being sharp is critical, and does not last.  So I changed the blade.

Cutting with a sharp razor.

Cutting with the sharp razor was much more effective. I was able to get good clean cuts and with a little practice I was able to get quite clean edges.

Early attempts at cutting with the razor.  

A good clean cut with using a razor. 

So it looks like I'll plan to use the razor/box cutter approach.  These pieces are 1" thick not 2" thick.  I think if I am good about cutting from both sides vertically it will work pretty well.  And I'll look at getting some slightly longer blades too.

I chose to avoid the hot wire/hot knives as they tend to produce a lot of fumes etc, and I expect they actually take longer than a good blade.

Of course if I was going to be doing a lot of this.  There's a really good product from Bullet Tool the Magnum Rigid Foam Cutter