AMAzer (oz7447)

About this Plan

AMAzer. Rubber competition model.

Quote: "Dear Outerzone, Please add the following plan of the AMAzer by W. S. 'Woody' Blanchard, Jr. to your inventory. From MAN, 1953. Contemporary of his FAIson F1C, sharing many aspects. Check out his AMA HOF bio at modelaircraft.org Amazing guy ...Many thanks and keep up the good work."

Direct submission to Outerzone.

Update 24/10/2019: Added article, thanks to RFJ.

Quote: "The new 'Limited 200' rules call for 200 sq in total area. This 1953 design does an honest 3-1/2 to 4 minutes. AMAzer, by WS Blanchard.

The 1953 AMA rules introduce a new and interesting rubber-powered model - the Limited 200. The limitations consist simply of a minimum required weight of 5 oz and a maximum projected wing-plus-horizontal-tail-area of 200 sq in.

The AMAzer 200 is so named for a purpose - its performance is amazing: in dead air, this ship does an honest 3-1/2 to 4 minutes. Construction is simple and fast, so if you want a lot of flying in return for a little building time and very little expense, let's start.

The most important single component of a high-perform-ance rubber-powered model is the prop. Select the softest block available for blades. Cut block diagonally as shown in drawings, and carve blades with straight-grained edges for the leading edges. Note particularly that the blades are much thicker in section than the conventional rubber prop and have less undercamber. They incorporate, in fact, a good low-Reynolds-number wing section - the same section as that used in the wing (prop operates at almost exactly the same Reynolds number as the wing, and at about the same section lift coefficient, so why not?). Results indicate that this prop delivers more thrust per unit of motor torque at given rpm, in addition to requiring less motor torque. An indication of this is the fact that, with only 12 strands of 1/4 flat T-56, the 16-1/4 in diameter, 22 in pitch prop affords a very fast climb.

The type of prop hub shown is very durable, and affords lower drag with blades folded than the conventional prop. Bend the 1/16 wire hinges, and mount in 1/16 holes drilled in the 1/4 aluminum tubing hub. Retain with flat washers soldered in place, then insert hinges

into blade hubs, and bind with thread. Next bend blade stops of 1/32 wire, and bind to prop hubs with thread. Adjust stops so that air-loads on blades will not deflect blades forward of the plane of rotation. You will find that a little judicious bending with needle-nose pliers will remove any tendency of the prop to wobble, and small changes in- blade pitch by bending hinges will yield control over power flow. Install a conventional shaft of 1/16 wire, mount assembly in the nose-block, provide a stop for the shaft, cover blades with Jap tissue, and prop assembly is complete. If you are unable to obtain soft, light wood for the blades, however, carve lightening holes in blades prior to covering. However, it is inadvisable to thin the blades in order to remove weight.

The fuselage is conventional in structure, and requires no explanation. The 1/16 sheet wing-rests are installed after entire top of fuselage is tissue covered, in order to preserve torsional rigidity. Note that the fuselage has no diagonals—they are not needed provided fuselage is well covered and doped (at least three coats, preferably four).

The wing employs 'sliced' ribs. Make one rib template of plywood, metal or hard balsa and, using this template as a guide, slice upper ribs from 3/32 medium sheet balsa. Cut ribs 1/16 deep. Repeat this operation for lower ribs. Next, taper the 3/32 x 3/8 trailing edge stock from 3/8 wide at the root to 1/4 wide at the tip. Use a straight-edge for this operation, and remove wood from thick edge of stock, thereby reducing thickness of trailing edge toward tip. Taper spars to dimensions shown in drawing, then pin down leading and trailing edges. Next, fit lower ribs in place, flush with drawing, by trimming off excess length at trailing edge. Now, cement spars to lower ribs, then cement upper ribs to leading edge, both spars, and trailing edge. Make the false ribs (top only) using the forward portion of rib template as a guide. Assemble wing with 1-3/8 in dihedral at each inboard break, and 3-3/4 in at each tip. Add all gussets, butt plates and tips and wing is complete.

The horizontal tail is of the same type construction as the wing, except that lower ribs are 1/16 square stock. The upper and false ribs arc of 1/16 sheet. The vertical tail is assembled on the fuselage. Note that leading edge of rudder extends through fuselage to form leading edge of sub-rudder..."

Supplementary file notes

Article.

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