Case Study: Minijets Stinger with DS-51-AXI HDS and HET 700-68-1125kV

In order to avoid a disappointment due to unexpected flight behaviour or insufficient performance of the planned model, we would like to take the opportunity to present some substantiated criteria enabling the realisation of the favoured characteristics for the model.
A simple calculator is sufficient for all the indicated formulas. The required data are easily definable with the manufacturer information or by means of a scale (weight).

An important point when choosing the right fan unit for the model is the power/weight ratio. In contrast to the thrust/weight ratio this also considers exhaust speed (all calculations refer to max. battery voltage).

After mathematically ensuring the performance of the jet the next step should be to control the stall speed in order to avoid surprises at the take off and landing phase.
A usual criterion for estimating smooth and trouble-free handling of the model on normal airfields is the well-established method of measuring the wing loading. This is applicable when two similar models are compared and should not be applied with a strongly different airfoil, a very different aspect ratio or a divergent proportion of wing and fuselage.
Besides, the airfoil depth has an impact on stall speed. In order to consider all of these parameters at least to some extent, we provide you with the following formula.

Based on logged measurements with our very early DS-51-FAN 3-ph during the flight and theoretical background as well as wind tunnel measurements on our DS-51-DIA 3-ph we now would like to describe an approach for the configuration of intake and outlet ducts.

The most outstanding characteristic when designing the ducting is a reasonable distribution of the cross-sectional area. The other parameters such as duct length and cross-sectional shape tend to be given by the original.

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