Tench745
Master member
*This is a reposting of the build I began to cover in the Cafe Racer Mk II thread, but I have decided to move it to it's own. All further building and testing of the new Mk III design will be covered here.*
Even with the improvements of the MK.II I find myself wishing I had gotten a little closer to the concept art the plane was based on.
I've been curious about using paperless DTFB and Keith Sparks' foam building methods to construct a lighter, and much more finished looking aircraft. As such, I've begun re-drawing my Cafe Racer for building in raw foam, possibly to be glassed. When I first started obsessing over this fictional airplane I took the time to draw a top and side view from the original artwork, focusing strongly on the relative sizes, shapes, and dimensions of each part.
It was this 2-view drawing I began by taking measurements off of. Happily, the original artwork has a figure. Assuming a figure height of 6 feet I estimated that the chord at the wing root was about 4 feet. On my sketches the wing root was 2". Thus, my sketch was 1/24 of the fictional full-scale prototype.
Interestingly, this means the full-scale would have an 18 foot wingspan, almost identical to that of Art Chester's Goon.
Now that I had a scale of the drawings I had to decide on a scale for the model. Since the wings are the most important thing on an airplane I used the same root-chord as a start for scaling the new model. MK.II had a 9" root chord. For ease of maths I chose an 8" root chord for the new one, making it a 1/6 model of the full scale and allowing me to simply quadruple any measurement I took off my drawings.
All of this gave me the following:
Wingspan: 36"
Length: 36"
Wing area: 185 square inches
Satisfied that this would be flyable if kept to the same weight as the MK.II version I proceeded with drawing the basic shapes in CAD. In order to experiment with the building techniques and get an idea of the final size I decided to start with the focal point of the whole shebang, the exposed engine.
Below is the prototype engine. I have yet to attach the cylinders and construct the cooling fins, but so far I'm pretty happy with it.
White gorilla glue is super easy to work with and the DTFB cuts, sands, and glues well once the paper is removed.
I was happy to see the crankcase is large enough to contain a motor, esc, and possibly even the battery.
Got looking at my crankcase yesterday, decided it was too wide, so a few minutes and a long razor blade later I had this. Neat to see the framing from the inside like this. Good too, since the case was almost sanded through in the front on top.
I cut 1/8" off each side to slim the whole thing down. It looks a lot better now but the camshaft/lifter area needs to be reworked still.
I'm testing using foam plates for the cooling fin/cylinder arrangement. They work pretty well and can be sanded to shape. I'm not sure how durable they might be. We'll see.
Side project, I decided to try and duplicate the little toolbox on the wing. Something innocuous, but so much detail nonetheless. Since the wrenches on the wing are too big to fit into the drawers I made the assumption that there must be a tray in the top of the box as well. I think it turned out pretty good. It's much more distressed than the one in the artwork, but it IS a mechanic's toolbox, is it not?
Just a pair of pictures showing all 6 cylinder blanks glued up and drying.
Also, this is the narrowed case. I've moved one of the pushrod locations from the front to the rear of the engine so I can offset the cylinders from one side to the other.
Even with the improvements of the MK.II I find myself wishing I had gotten a little closer to the concept art the plane was based on.
I've been curious about using paperless DTFB and Keith Sparks' foam building methods to construct a lighter, and much more finished looking aircraft. As such, I've begun re-drawing my Cafe Racer for building in raw foam, possibly to be glassed. When I first started obsessing over this fictional airplane I took the time to draw a top and side view from the original artwork, focusing strongly on the relative sizes, shapes, and dimensions of each part.
It was this 2-view drawing I began by taking measurements off of. Happily, the original artwork has a figure. Assuming a figure height of 6 feet I estimated that the chord at the wing root was about 4 feet. On my sketches the wing root was 2". Thus, my sketch was 1/24 of the fictional full-scale prototype.
Interestingly, this means the full-scale would have an 18 foot wingspan, almost identical to that of Art Chester's Goon.
Now that I had a scale of the drawings I had to decide on a scale for the model. Since the wings are the most important thing on an airplane I used the same root-chord as a start for scaling the new model. MK.II had a 9" root chord. For ease of maths I chose an 8" root chord for the new one, making it a 1/6 model of the full scale and allowing me to simply quadruple any measurement I took off my drawings.
All of this gave me the following:
Wingspan: 36"
Length: 36"
Wing area: 185 square inches
Satisfied that this would be flyable if kept to the same weight as the MK.II version I proceeded with drawing the basic shapes in CAD. In order to experiment with the building techniques and get an idea of the final size I decided to start with the focal point of the whole shebang, the exposed engine.
Below is the prototype engine. I have yet to attach the cylinders and construct the cooling fins, but so far I'm pretty happy with it.
White gorilla glue is super easy to work with and the DTFB cuts, sands, and glues well once the paper is removed.
I was happy to see the crankcase is large enough to contain a motor, esc, and possibly even the battery.
Got looking at my crankcase yesterday, decided it was too wide, so a few minutes and a long razor blade later I had this. Neat to see the framing from the inside like this. Good too, since the case was almost sanded through in the front on top.
I cut 1/8" off each side to slim the whole thing down. It looks a lot better now but the camshaft/lifter area needs to be reworked still.
I'm testing using foam plates for the cooling fin/cylinder arrangement. They work pretty well and can be sanded to shape. I'm not sure how durable they might be. We'll see.
Side project, I decided to try and duplicate the little toolbox on the wing. Something innocuous, but so much detail nonetheless. Since the wrenches on the wing are too big to fit into the drawers I made the assumption that there must be a tray in the top of the box as well. I think it turned out pretty good. It's much more distressed than the one in the artwork, but it IS a mechanic's toolbox, is it not?
Just a pair of pictures showing all 6 cylinder blanks glued up and drying.
Also, this is the narrowed case. I've moved one of the pushrod locations from the front to the rear of the engine so I can offset the cylinders from one side to the other.
