Extruded* polystyrene foam is available most places in the world as rigid insulation sheets but not always easy to find in thicknesses greater than 2"/5cm or so. Foam billets can be found as flotation if you live near the water but they are not as easy to find elsewhere.
So...how to use rigid foam panels to make a Rutan-style wing moldless composite wing? Just piling up foam sheets to create a billet can be done but the glue lines can pose problems for hot-wiring.
Presumably you could use a router/hot wire/band saw to cut continuous foam leading and trailing edges, one or two spars, and ribs, and then assemble it all with foam skins. The parts count would be high, however, and I'd be worried that a thin foam skin wouldn't provide enough rigidity and a thick one would be a pain to work with.
You could also recreate a hot-wired core as a stack of routed ribs (really slices of core) which would take time but it's not hard with a flush cut router bit and a solid template. A 12' wing panel for a single seater would require 72 stacked 2" ribs plus the spar extensions if needed. A flat-bottom airfoil might be helpful it getting everything lined up.
The foam availability and/or desire to avoid hot wiring could make this appealing for some people. Is there an easier way? Examples of good designs like this?
Cheers,
Matthew
*EDIT: I typed "expanded" by mistake.
So...how to use rigid foam panels to make a Rutan-style wing moldless composite wing? Just piling up foam sheets to create a billet can be done but the glue lines can pose problems for hot-wiring.
Presumably you could use a router/hot wire/band saw to cut continuous foam leading and trailing edges, one or two spars, and ribs, and then assemble it all with foam skins. The parts count would be high, however, and I'd be worried that a thin foam skin wouldn't provide enough rigidity and a thick one would be a pain to work with.
You could also recreate a hot-wired core as a stack of routed ribs (really slices of core) which would take time but it's not hard with a flush cut router bit and a solid template. A 12' wing panel for a single seater would require 72 stacked 2" ribs plus the spar extensions if needed. A flat-bottom airfoil might be helpful it getting everything lined up.
The foam availability and/or desire to avoid hot wiring could make this appealing for some people. Is there an easier way? Examples of good designs like this?
Cheers,
Matthew
*EDIT: I typed "expanded" by mistake.
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