|Oct 26, 2007, 09:49 AM|
1950's FROG Speedy
This model is constructed of 2mm foam salvaged from a sheet of sturdy board that was headed for the trash. I was just about to fold it up and stuff it into a trash bag when I looked at the thin layer of foam sandwiched between 2 paper layers, so I peeled a corner back to test how cleanly it would come off, and to my surprise it came off cleanly without leaving any residue or paper behind.
This foam has a porous surface and is stiff along one axis, flexible in the other. it feels like a lower density than depron and can be creased without snapping, too. regular CA melts it, but foam safe works fine, as does polyurethane glue which expands into the porous skin and holds on tight.
It sat in my foam box for a few months till I needed a light thin foam for a small build, it was the perfect choice for a scaled-up old time sheet model, the Frog junior series featured sheet balsa construction and were designed to be stable and easy for a junior flyer to trim even at a scant 11" wingspan.
I scaled up the plans to 18.5" span and made a kit of parts, and before the night was through I had framed up the fuselage and hinged the tail feathers.
Another night to make the wings and install radio gear, and most of a Saturday afternoon pleasantly spent painting and detailing produced what you see here.
Full up flying weight is 76g including a 300mah 2 cell lipo.
It is motivated by a hobbycity.com 10g brushless motor and 6g esc spinning a GWS HD6030 prop, and manipulated by a cirrus micro joule 4 ch receiver, 1 micro joule servo for ailerons, and 1 2.4g blue arrow servo for elevator.
I planned to use only micro joule servos but one of them centers very poorly and is sometimes jumpy.
The paint scheme was freehanded with a ruler and pencil on a spare set of plans and then reproduced in frisket film used to mask it for airbrushing the red portions, and the black pinstriping hides the rough line between the red and white that resulted from the porous foam surface.
The landing gear are a departure from the original plan, and use left over wheels and axles from a hobby lobby pitts 3D that I never built. The profile pants are 3mm construction foam from bphobbies and 3mm CF tubes with a music wire joiner providing the correct angle and spacing.
The bracing wires are functional and made from some very old braided silk fishing line. The wings do not have any CF bracing, and so the bracing wires are tightly rigged through hardpoints in the wings made from 1/64" plywood plates top and bottom, then meet in the fuselage through a 3mm CF tube. I tested the wing flexure before and after rigging, what a difference.
The canopy is made from drafting mylar, same as the hinge material. I made a paper pattern freehand, and when I was satisfied with the fit I reproduced it on mylar. I first colored the mylar with a light blue chartpak ad marker to give it a blue tint, then drew the canopy frames with a black sharpie.
The top half of the fuselage forward of the turtledeck is a removeable hatch retained by magnets, and gives full access to the radio gear. The battery is located in a pocket between the top of the wings and the bottom of the radio deck, and is removeable by popping off the chin cowling and sliding it out toward the propeller. The chin cowl directs cooling air over the ESC and battery, allows an outlet for the motor cooling, and conceals the battery wire and connector.
I was conflicted about leaving the micro joule aileron servo visible on the bottom, but it is so small and unobtrusive I decided to leave it exposed. These servos can get pretty hot during heavy use as I discovered while trying to fix the defective one. The cooling airflow should prevent overheating and damage.
I have yet to add the FROG logo to the vertical stabilizer; that will happen this weekend.
|Oct 31, 2007, 02:57 PM|
Nice job. I'm going to use that motor in a 60g(approximate) J-3 Kitten, 24" WS. Yours weighs more so I'll assume that I'm good on my model. Again, your model looks very nice.
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