Merbaby (oz2899)

About this Plan

Merbaby. Rubber powered floatplane.

Quote: "Merbaby, by Vic Smeed. A 20-inch puddle jumper for beginner or expert.

ONE EVENING'S WORK, four lengths of 1/8 sq, half-a-sheet 1/32 x 3 in, 18 inches of wire, a scrap of tissue, an inch of tube and a propeller - that's the complete list for snappy little Merbaby which will return you fun far in excess of the outlay.

It's a good many years since a stick model was featured in the Aeromodeller; older fans will remember that in the '30s such models were the basic trainers of the day and were regularly featured in the model press, especially in the old American Flying Aces. We have retained most of the simple features of these early models, but one or two improvements such as a built-up stick and rubber-held wing have been incorporated.

Pick medium hard 'springy' 1/8 sq, and lay out the fuselage frame. The rear rubber hook should go into the lower longeron before pinning this down. When the frame is dry remove the pins, cement the frame and lay the entire sheet of 1/32 in place, weighting down to dry. When the cement is set remove the unit from the plan and trim to shape; repeat on the other side. The fuselage is finished by cementing two pieces of 1/8 sq beneath the nose and binding a stub of 20 gauge aluminium tube in place; note the correct downthrust, obtained by trimming the 1/8 sq. Coat over the tube and patch with cement.

The tailplane is a simple flat plate, as is the fin. The trim tab can be of very thin aluminium foil or celluloid, or even notepaper.

The wing is built one half at a time flat on the plan, omitting the centre 'ribs'. When the second half is dry crack the spars to dihedral and pin the wing down on edge, cementing in the two short sq. braces. Now add the two centre ribs. The wing pylon is a II sq. frame; the lower member can be pre-curved in the fingers before assembly. Cover the sides with 1/32 sheet as with the fuselage, and when dry clean up and round fore and aft before adding the side plates and stub pegs, which can be pared from a matchstick. The flying surfaces are covered on one side only, with lightweight hard tissue, without even rounding the edges. A coat of very thin banana oil is all that is required, but make sure that there are no warps. Cement the wing to the wing-mount and the fin and tail-plane in place when the banana oil is thoroughly dry.

The airscrew on our original was a stock 8 in KK propeller which we merely sanded lightly and checked for balance; the 7-1/2 in KK plastic prop should prove quite as suitable. Bend the rubber hook, slide the shaft through the nose bearing, fit on a cup washer and the propeller (which is best bushed with tubing) and bend the front loop. The freewheel pawl is fitted through an unbushed hole and should swivel freely; check that the operation is satisfactory.

Nothing further need be done for landplane flying, although a tail skid and wheel undercarriage makes operation much more fun. Use 3/4 in light-weight wheels.

The float gear is built by cutting six identical 1/32 sheet sides and cementing these upright on 1 in wide strips of 1/32, cross grained. When the initial cement is dry the sheet can be bent round the float; the top is covered in the same way. Bear-claw floats of this size need no internal structure. The mounting wires are bent into a diamond at their extremities and cemented against the floats with two or three coats of cement. We used 24 g wire and found it necessary to attach cotton braces, but if 22 g wire is used with a x cross brace between the floats no other bracing is necessary.

One 13 inch loop of 1/4 x 24 rubber brought our finished weight to just 3/4 oz, including two thorough coats of banana oil on the floats. If you expect to fly over a large area of water where the model may alight back on water, it is advisable to banana oil the fuselage as well.

We found the best trim was slight right rudder with a little wash-in (leading edge 1/8 in high) on the port wing. Slide the wing forward or back until the model balances approximately at mid-chord, take up the slack in the rubber with a few turns, and check for glide. When the right position for the wing is found, mark it clearly. On maximum turns (450 or so) you should hit a consistent 30 secs. plus - the neater and lighter your construction the higher your flight average will be."

Direct submission to Outerzone.

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