Yak-18PM (oz6291)

About this Plan

Yak-18PM (18P / 18PM). Scale model for RC. Originally published in MAN 1968, later kitted by SIG.

Quote: "The differences between the P and PM are distinctive but the plans can be used to build either variant. The 18P, a special acrobatic and sport craft, came from a long line of YAK 18 trainers. It was used as the Russian team aircraft in the 1964 World Aerobatic Championships in Bilbao, Spain. While a spectacular performer, it did not win the individual championship and further modifications to increase the acrobatic characteristics were undertaken. The result was christened the 18PM. At the Moscow 1966 World Acrobatic meet, it really took the laurels, winning the first four places in both the men's and women's individual championships and the team trophy as well. The modifications made on the 18P to produce the 18PM were as follows: Dihedral reduced from 7 degrees to 2 degrees to improve inverted stability; Cockpit moved to the rear to move back the CG and increase maneuverability; Oil cooler on starboard wing enlarged; Flap replaced by a much smaller air brake on the former flap hinge line.

You can see these features on the working plans and elsewhere in this issue on the three view by Capt Halls of the 18PM. Builders of the 18P should also get a copy of the January, 1967 issue of Flying Review so that the differences are apparent to scale judges.

I selected the 18P because the forward cockpit was better located for inclusion of complete cockpit detail and still have the servos in the proper place. This decision was made before the appearance on the modelling scene of Ny-rod and its derivatives. Now it would be easy to mount the servos ahead of the cockpit hi a PM and route the controls along the walls and still have space for a complete cockpit and pilot. I also thought the larger dihedral of the 18P was a better choice for my flying skills and finally I liked the looks of the forward cockpit.

The scale of the model is just over 2in to the foot. Purists complain about uneven scales, but I maintain that a model of say 2.046in to the foot is just as much to scale as a 2in to the foot. In this case, the reasons for the size were compelling. At 2in the engine stuck through the cowling, whereas a small increase got it inside. The new rules for RC Scale require that if you use an unusual scale the judges must be provided with some way of relating the model to the 3-view provided. Take the Halls 3-view to a photo-copy place and have it enlarged so that the wing span on the three view is an exact multiple of the wing span of the model. Present this to the judge with a notation of the multiple to the model size. This will fulfill the rules and please the judge as well..."

Direct submission to Outerzone.

Update 29/11/2016: added article, thanks to RFJ.

Supplementary file notes

Article.

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