Demdike (oz12819)

About this Plan

Demdike. Radio control slope soarer model.

Quote: "R/C Slope Soaring. J Riley and E Lord provide some useful information on the art of R/C slope soaring.

...probably the most valuable information we can pass on is which type of model and construction we have found to be most suitable. The model should be heavy by normal standards, with a wing loading between 8 and 20 ounces per 100 sq in of wing area. Size should be from about 450 sq in upwards. Bigger models fly better, but against this must be considered the economy, ease of transport and durability of a small model.

Low drag is a necessary factor to combine penetration with a low sinking speed, but streamlining must definitely take second place to the requirements for maximum strength. Given a reasonable soaring site, efficiency is of little importance, a strong practical model being the main requirement.

Specifications we have found suitable, given as a rough guide, are as follows: Aspect ratio 8 to 10, tail 35 per cent wing area. With this tail a larger wing can be fitted on the same fuselage for flying in light winds. Fuselage length about Rths wingspan and dihedral around 1 in tip rise per foot span. A rudder 25 per cent of the fin area using very small (about 5°) angular movement gives satisfactory control. Construction must be decided with the necessary fast flying speed in view, and for the fuselage, must be in terms of 1/8 ply, 1/2 in hardwood formers and spruce longerons, fibreglass, etc. The wing must be correspondingly strong.

The model 'Demdike' features a detachable pan of 1/8 ply and hardwood formers, etc which carries all the batteries and is located by a Newey Snap Fasteners and shear pins and held on by rubber bands. On one flight (first flight Elfin 1.49 assisted) this fuselage parted company with the wings at 300 ft and model and receiver were undamaged despite having penetrated 6 in into hard ground. Tie rods with nuts and washers hold the fuselage sides together and glass fibre reinforcement is used. The fuselage is covered with a light grade of fibre-glass tissue with heavy weight model span over this. Parachute nylon also makes excellent covering material and the wing, constructed mainly of spruce, is covered with this. It is recommended that the wing should be mounted on top of the fuselage, as with any shoulder wing arrangement, the wings cannot knock off so easily."

Direct submission to Outerzone.

Quote: "Hi Steve & Mary, I hope you are well, and staying safe in these trying times... I recently found a handfull of RCM&E magazines that I had stored away and forgotten about. They are in the A5 format from the early 1960s, so I scanned this slope soarer at 1200 DPI and cleaned it up a bit, seems to have come up OK. An interesting view of the early days of R/C Sloping, they built them tough in those days, (still do I suppose, but not with wood). Unusual stabilizer airfoil."

Note this is not a full size plan. If anyone out there can submit a scan of the full size plan, that would, of course, be great.

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