Diamond (oz9344)

About this Plan

Diamond. Radio control aerobatic model for .40 engines and 4 function RC.

Quote: "For fast, smooth thrills build this 52in span fun aerobatic 'compact'. Diamond, by Tony Wright.

GIVEN a few basic criteria, I have always felt that a model which looks right, flies right. The criteria in this case were that it must have a wing to support the weight, a tail to hold the wing at the right angle, and something to join them together. After that it was merely a case of making a working drawing to test the 'design'. The original performed to my satisfaction, so the design was not changed except for a few minor construction points.

Only slightly contrary to what I said earlier (!), points to which I paid particular attention are as follows:

1. Large tank bay - I used the 10oz Powermax slant-front tank. This tank gives about 71 minutes but I use an OS 40FSR with an ED pipe, a combination not guaranteed to improve fuel economy. However, a large tank is rarely a disadvantage, and the space is there.

2. Large ailerons - this allows you to set the feel as you wish. With the maximum movement shown on the plan the model rolls fast, but can easily be toned down. It is not so easy to increase a roll rate, so plenty was designed in.

3. Large fuselage side area - this, together with the large rudder, really helps with manoeuvres like the four-point and slow roll, but do make sure you get as much rudder throw as possible. I always use a closed-loop linkage for the rudder and details can be seen in the pictures. The large rudder also helps with stall turns; in the figure M it is useful to have your model go the same way as you moved the stick!

Diamond was designed with schedule practice in mind, and it does this very well (with reduced surface throws to make it softer). The other point I would stress is to make sure that the wing has a slight positive incidence when sitting on its wheels. This will ensure a smooth lift-off, but watch your speed on landing or it will bounce for sure. It can be slowed down very well for landing though, and main-wheels landings are easier than you might think. If you fly off grass you may prefer to lengthen the undercarriage slightly, and increase the main legs to 8g, but for tarmac the design is fine as shown on the plan.

Finally, do make full use of the centre and reference lines as detailed on the plan. A little work with a fine line felt tip pen (not a ballpoint) will pay off when you fly it.

Construction. I like building, but I prefer flying..."

Diamond, Radio Modeller, March 1979.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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