A recent thread on low-cost CNC routers for cutting panels got me thinking about the the potential these have to make building a composite plane faster and with more accuracy. The machines now can be built for less than $500, and can handle sheet sizes up to 4' x 8'. They are fairly accurate (to within 1/64" to 1/16" = .4mm to 1.2mm). Watching the machine make parts for furniture from a sheet of plywood, it seems it could be used to make composite airplane parts:
- Flat parts (fuselage formers, bulkheads, wing ribs, flat panels): The builder could make large (up to 4'x8") sandwich panels (epoxy, FG or CF, both sides laid up and then put on the CNC machine). These could be vacuum bagged against a flat surface (one side) to reduce filling/sanding and improve strength/weight. It would be quick work, since the edges could be left raw, and one big panel could be used to make a lot of parts.
- Simple (2D) curved parts (wing skins, fuselage panels, etc): The builder would glass just one side of the panel. Then, the CNC router would kerf the back side of each part to allow it to be curved to the required radius without crushing the foam, etc). The panels would be turned over, on the CNC "bed" glass-side up, and the router would cut out the parts. The builder would then bend them over the over the already-made flat formers (ribs, bulkheads, etc) and glass the back side of each to lock in the shape (like the "fold-a-plane" method).
Yes, the edges and corners would still require glassing after the parts are put together.
I'm sure this approach has already been considered, but I'm just ignorant of it. It would seem possible to significantly speed up the construction of a homebuilt composite aircraft design by reducing the number of layups needed, it could dramatically reduce the time needed to cut out parts, and improve the accuracy of the sizing and shaping of these parts (virtually self-jigging with tab-in-slot construction and other means to register parts against each other) which would the reduce trial-and-error fitting of each part. And, at least in my own case, the ability to easily and precisely shape and locate components would make me less reluctant to try blind-fitting of parts (e.g. rib and sandwich skin wing construction rather than the solid-core Rutan-style wing).
Also, if a builder doesn't want to do the layups or even the CNC cutting, a very small manufacturer could do the cutting of these parts with minimal investment compared to other methods. And, shipping moderately-sized flat parts to the builder would be relatively cheap.
So, my questions:
1) Is there already a plane design doing things this way?
2) Can a router with carbide bits cut out parts from fully-cured panels in this way without delaminating the edges? If not, could it be done at the "green" stage?
3) Would it be possible to make compound (3D) curved panels(for cowlings, wingtips, wheel pants, etc) as described above, but by kerfing the back side of the foam in two or more directions (leaving hexagons of various sizes, depending on the radius of curve needed). Would the glassed (outside) allow the panel to be bent in two directions?
4) Is this dumb?
- Flat parts (fuselage formers, bulkheads, wing ribs, flat panels): The builder could make large (up to 4'x8") sandwich panels (epoxy, FG or CF, both sides laid up and then put on the CNC machine). These could be vacuum bagged against a flat surface (one side) to reduce filling/sanding and improve strength/weight. It would be quick work, since the edges could be left raw, and one big panel could be used to make a lot of parts.
- Simple (2D) curved parts (wing skins, fuselage panels, etc): The builder would glass just one side of the panel. Then, the CNC router would kerf the back side of each part to allow it to be curved to the required radius without crushing the foam, etc). The panels would be turned over, on the CNC "bed" glass-side up, and the router would cut out the parts. The builder would then bend them over the over the already-made flat formers (ribs, bulkheads, etc) and glass the back side of each to lock in the shape (like the "fold-a-plane" method).
Yes, the edges and corners would still require glassing after the parts are put together.
I'm sure this approach has already been considered, but I'm just ignorant of it. It would seem possible to significantly speed up the construction of a homebuilt composite aircraft design by reducing the number of layups needed, it could dramatically reduce the time needed to cut out parts, and improve the accuracy of the sizing and shaping of these parts (virtually self-jigging with tab-in-slot construction and other means to register parts against each other) which would the reduce trial-and-error fitting of each part. And, at least in my own case, the ability to easily and precisely shape and locate components would make me less reluctant to try blind-fitting of parts (e.g. rib and sandwich skin wing construction rather than the solid-core Rutan-style wing).
Also, if a builder doesn't want to do the layups or even the CNC cutting, a very small manufacturer could do the cutting of these parts with minimal investment compared to other methods. And, shipping moderately-sized flat parts to the builder would be relatively cheap.
So, my questions:
1) Is there already a plane design doing things this way?
2) Can a router with carbide bits cut out parts from fully-cured panels in this way without delaminating the edges? If not, could it be done at the "green" stage?
3) Would it be possible to make compound (3D) curved panels(for cowlings, wingtips, wheel pants, etc) as described above, but by kerfing the back side of the foam in two or more directions (leaving hexagons of various sizes, depending on the radius of curve needed). Would the glassed (outside) allow the panel to be bent in two directions?
4) Is this dumb?
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