Eureka (oz2158)

About this Plan

Eureka. Open power model. 12 oz for 2.5cc. October 1958 Aeromodeller.

Quote: "In response to universal request - we bring you the fastest climbing of all open Power designs.Only 12 ounces for 2.5 cc By Norman Marcus

POWER MODELLING is now divided 80 per cent Open and 20 percent FAI. if the 1958 entry figures in British contests are any measure, and the demand for fast climbing lightweights is on the upswing. Here we have the 'hottest' of them all. Norman Marcus has been out of the contest sphere for a season or so (explained by his marriage on August 9th) but his Eureka design has been making its mark in the hands of John O'Donnell, winner of Power at the Nats.

The design was evolved to improve upon the Jaded Maid (oz869) which although successful had some drawbacks. It was too fragile, being rather on the large side for its original 12 oz weight which made windy weather flying rather a problem. With Eureka it was decided to keep the weight down to about 12 oz and to reduce the general size of the model to make a sturdier job. The wing span was determined by the size of Norman's model box!

The thrust line was moved upwards and the fuselage was shaped so that the side areas (and side view of the wing) would roughly balance about the thrust line-to equalise the moments of the side forces about the CG. Propeller tip position determined the height of the pylon as wing was required to be clear of propeller slipstream, and the tailplane was moved more into the prop blast. The fin was placed behind the tail for convenience with the pop-up tailplane DT and also to give extra moment to the fin area. (Fins in front of the tailplane had proved rather disastrous with some of Norman's earlier models.) This rear fin set a fashion which is now a characteristic of many British power designs.

The thought of letting the motor run at full power on such a small, lightweight design was rather frightening; but after a few seconds motor runs Norman chanced his arm and let it go flat out. Much to his amazement and joy Eureka climbed almost vertically, slowly turning in right-hand spirals-and that was how it flew contest after contest. Unfortunately, the glide proved to be rather inconsistent, with the model falling out of the sky on occasions. Reason for this was that when the motor cut, and the model speed reduced suddenly, the laminar flow over the wing broke away at the first spar and did not re-attach itself properly. A sheeted leading edge version of the model showed considerable improvement in the glide.

Now for the construction of the model. The wing and tailplane are straightforward in their original form, but if it is decided to use geodetic construction, as in the John O'Donnell modification, care should be taken to build in the slight warps into the wing (see trimming notes). The tail is flat and quite simple. The fuselage was built in 'mid-air'. First the 1/8-in sheet sides of the body and the 3/8-in hardwood motor mount should be cut to shape. The mount is glued to the left-hand side of the fuselage and is left to dry. Make the fuel tank from .005-in tin sheet and cement it in position..."

Update 05/08/2016: article pages, text & pics added, thanks to RFJ.

Supplementary file notes

Article pages, text & pics.

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