Gee Mac (oz5394)

 

Gee Mac (oz5394) by BM Evans 1950 - plan thumbnail

About this Plan

Gee Mac. Control line class B Team racer by B.M. Evans. From Model Aircraft Oct 1950.

Quote: "AT the SE C/L Championships at Brighton, 'Gee Mac' gained second place in the team race despite a blockage in the feed tube (found afterwards) which cut the speed and laps by 20 percent due to 'richening' in flight, coupled with a dizzy pilot (no comment please!)

Construction. Fuselage: This is the heart of the model and centres around the motor plate of close-grained 1/4 in beech. This is fret-sawn to shape and the engine bolts inserted, the heads being soldered to strips of tin. Check these joints well before gluing to the base of the fuselage.

The crankcase beds up against the cross-piece to cut bearer whip to a minimum. The undercarriage of 12 swg piano wire is bent to shape and the undercarriage plate of 16 swg dural is bent to fit as shown. The top of the plate is then fuel-proofed and the undercarriage screwed tightly into place.

The bottom of the fuselage is sawn and carved to the elliptical section shown. Hollowing is done with a gouge, keeping the nose at bearer thickness to ensure a good joint. Slots are cut for the motor plate, wing spar and elevator movement (+/- 30°).

Wing: This is quite straightforward. The hard-wood spar is first tapered, then ribs, leading and trailing edges, bellcrank and leadouts, tips, and finally, spanwisc A, in. sheeting are added in that order. The trailing edge must be tapered in both directions before assembly and, although a lead weight was used in the original, the handling characteristics have shown this to be unnecessary.

Tail: This is cut to outline from hard fin. sheet and the hardwood spar added. The control horn is screwed in place after a trial lit in the fuselage and the broad hinges added. The underfin is cemented to the fuselage and the skid, which may be looped to form a 'stooge,' is cemented in place.

Fuselage (cont): Wing, tail, motor plate and firewall are glued into position. Use Durofix not balsa cement, and be patient and leave overnight to dry thoroughly.

The upper formers are lightly cemented on to the fuel-proofed lower half and sheeted or planked. The fin is cemented in place and rudder inset lir in. cabin windows are cut out and the top removed whereupon the 3/16 sq strengtheners are inserted. The whole interior is now fuel-proofed.

Note: The removable portion is optional and was incorporated for access to bellcrank and fitting of a motor cut-out for later contests.

Cowl: The cowl is cut from 1/32 aluminium sheet. The front and rear are fanned as shown. The cowl entrance block is cut from hard balsa, the walls being about 1/4 in thick. The finished inlet is 'Durofixed' into place after sanding fuel proofer from motor plate at that point.

The metal cowl is essential as, with the original wooden cowl (pre Brighton), the motor consistently overheated and burned gaskets resulted.

Tank: The shape shown was found most satis-factory, producing virtually no ground flight fuel variation and draining the last drop of fuel. Check the capacity before soldering on the hack; and check for leaks after adding the tin mounting strap.

Finish: The whole model is sanded smooth, given two coats of clear dope, and rag tissue is then doped on. The colour dope is thinned-down then applied, preferably by spray, and three coats of fuel proofer are put on top, sanding between each. Don't try to spray fuel proofer as this produces a white cobweb effect upon which a contours judge would frown.

FlyingL Standard 32.5 ft light 'Laystrate' is used for lines. Leave the motor slightly rich for the first flights to reduce speed, laps, and line-pull until you are used to the landing technique. Gee Mac takes off in about 1/4 of a lap and will hold the lines at any altitude; but the higher you fly the dizzier you get (oh bitter experience).

In the glide don't lose speed. The long nose moment induces a stall at quite a high speed for stunt fliers, so fly it right down to the ground, flattening out just as the wheels touch down and keeping full up from then on. If the line-pull is too great, increase the rudder inset a little, but this does not pay in really windy conditions."

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Gee Mac (oz5394) by BM Evans 1950 - model pic

Datafile:
  • (oz5394)
    Gee Mac
    by BM Evans
    from Model Aircraft
    October 1950 
    28in span
    IC C/L
    clean :)
    all formers complete :)
    got article :)
  • Submitted: 10/03/2014
    Filesize: 1031KB
    Format: • PDFbitmap
    Credit*: stormin
    Downloads: 1608

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