Fokker S.14 Machtrainer
I've
built this Fokker S.14 as a catapul model. So, with some fantasy, it still is a
rubber driven model. There is an official class for these models in America: FAC Jet Catapult Scale.
The rules are rather simple, only the size of the catapult is restricted. The
dimensions of the model are completely free. My Fokker has a span of 20 cm,
which is rather small. The more succesfull models have spans of 30 to 40 cm. The
benefit of a smaller model is that the
drawing (free download) fits on a single sheet of A4 paper. Because I didn't
have any pictures of the S.14 I have based the drawing on a few black and white
photographs.
Construction
The fuse is constructed of a core of 1 mm balsa with a vertical grain orientation. This is also the fin. The core is laminated betwen two 1.5 mm sides which have a horizontal grain. The core of the nose isn't balsa but basswood, which extends a bit under the fuse to make a catapult hook. This fuse construction is very strong, which is a must for this type of model. The wings are from 1.5 mm balsa, the stabilizer is from 1 mm balsa. The faiing between the wings and fuse is cut from very light balsa block.
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Finish
The model is spray painted with a spray can of silver tire rim paint. The day-glo panels are first sprayed white, then orange. The markings are printed on regular paper and glued on the model.
The total weight is 9 gram, not a light weight but it does help to gain a good height.
Flying
The model flies well but it is tricky to launch the model without looping. To reduce this loopin tendency I used a Gurney flap on the stab. This is a simple piece of 1,5 x 1,5 mm balsa strip with a length of about 1/3 of the stabilizer span. As a result of adding this strip I had to remove some nose weight. It now is possible to launch the model in a straight line. The model usually recovers and glides well, but sometimes it dives straight down. The best timed flights are between 20 and 30 seconds on a thin catapult, which makes me very happy
