Lil Plank (oz8777)

About this Plan

Lil Plank. Free flight power flying wing model.

Quote: "This is number 8 in a series of planks and embodies the best features of the previous seven. Designed to be as small as possible and still be safe on an Allbon Dart at full revs, it is cheap and easy to build, takes up little space and is simple to fly without being too finicky over the structure and trimming details.

Build the wing first so that the fuselage can be made to suit it. All dimensions are given on the plan overleaf which is half-size. Cut out all the ribs, and spars for the wing centre section and cement the two dihedral break ribs to leading and trailing edges and to the two lower 1/4 x 1/16 in members. Cement the rest of the ribs into position together with the 1/16 in sheet main spar webs and finish off with the upper 1/4 x 1/16 in main spar members and 1/16 x 1/8 in front spar.

Build up each wing tip in a similar way by packing up the centre section to the correct angle and butt jointing the wing tip to it. In order to avoid tip stalling on the glide, about 1/16 in washout can be built into each wing tip. Cement a small piece of reinforcing linen on all the dihedral joints.

Make two 1/16 in fuselage sheet sides with cutout to suit the wing, allowing for the 1/16 in sheet bottom covering on the wing seating. Durofix hardwood engine bearers to one of the sides and assemble fuselage as far as the front bulkhead. Fuel proof inside of tank compartment and place several coils of fuel tube in position before finally sheeting the top. The tube should be enough for 20 seconds run plus starting. Durofix wedges on to the engine bearers to allow for side thrust and drill bearers to suit engine. Cement nose cowling and fins in position. Cover whole model with lightweight Modelspan and apply three coats of dope and one of fuel proofer.

Trimming. Since a 'plank' is rather tricky to test glide, I usually guess the CG initially and start with low powered flights. Before attempting any flights make sure wings are balanced and true to one another, also the CG should be slightly in front of that shown on the plan as it is easy to move this back when test flying. If test glides are attempted make sure they are over long grass as the gliding speed is rather critical.

Initial flights should be made on low power to check the glide. If the climb is to the left, open up the power using a little right rudder to keep the tail down. Lil' Plank should climb in a tight left spiral as this is the only way to control a large amount of power. A straight trim will give lovely snap loops and a right trim is likely to make a hole in the ground since there is no tail to counteract the gyroscopic action of the propeller! The whisker type undercarriage gives good take-offs providing you aim carefully into wind. Lil' Plank takes a fair distance to 'unstick', but rockets off the ground when full speed is reached. It might be a good idea to use one of these planes to clear a take-off area at contests!"

Note this plan shows wing layout at 50% scale whilst all other sections are at 100%.

Direct submission to Outerzone.

Supplementary file notes

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