During our stay in Znojmo for the EXFC, we took the advantage to go and meet the people behind Mejzlik, as well as finding out a bit more about their products.
On our arrival, we met with Ales, who very kindly showed us their catalogue of propellors, giving us an overview of their most recent developments as well as showing us their amazing stock in all sizes of propellors.
Shortly after this we met with Tomas Mejzlik who was nice enough to dedicate his morning to going over the production, design and development of their products with us.
Mejzlik must be most well known for their propellors, so we thought that this was a good place to start. The company currently offer just over 100 different sized carbon propellors designed for sport-aerobatic use, plus an extra 60 “speciality” carbon propellors, normally only produced on demand.
A very interesting detail from the production of Mejzlik”s carbon production line is that they use an Epoxy that was specially designed for them, which as well as being stronger than usual, also contains a much higher elasticity than regular epoxy, which allows you to do this to their products without damaging them!
The same is used in all their products, such as their spinners:
As far as the design of the propellors, everyone knows that this is a much more complex procedure than it looks in order to get a workable propellor. Nevertheless, Tomas explained some of the fundamentals to us, showing that he really does know his stuff, in many cases having to repeat himself due to us not being able to keep up!
For example, everyone knows that the more pitch a propellor has, as long as it can run at the same RPM, it will have more thrust than the same diameter with less pitch. But seemingly you must also take into account the speed of the model, as a very flat pitched propellor could be dangerous if the model reached a high forward speed, due to the impact force caused by the speed on the “flat” part of the propellor. So low pitch is best designed for slower models, with less forward speed.
Mejzlik as well as the standard diameters, also have variations of one same size, such as the Evo, L, S and N. Each with a different meaning and different shape. For example, the Evo has a different leading edge, with an almost straight trailing edge, which was designed to try and reduce some noise levels, while still keeping the prop diameter and power.
The L, have less carbon layers for the outer shell of the prop, however with a clever internal structure are more rigid while still being lighter than the usual versions. Meaning less force is needed to spin the prop at the same speed as the non L version, which leads to a faster spin up.
We asked Tomas why the centre of the prop was so large (the first half of each blade), and if it would be possible to make it smaller in order to not loose RPM”s. Very interestingly, they have performed tests, and the first 2/3rds of the propellor do not make much to any difference in how the propellor works, it”s speed or it”storque. The “working” part of the propellor being only the last 1/3rd (the tips)
Since the recent fever of round cowled models, such as the Sukhoi”s, Yaks… pilots have encountered a new obstacle, which is the cowl “hiding” much of the propellor. Fortunately, as mentioned above, the centre part of the propellor doesnt make much difference, so there is not much loss. This is why moving the engine (or more to the point the propellor) forward, leaving a little more gap between the engine and the cowl works so well, because the 1/3rd of the propellor that generates the power is then still in full working order with clean air flow.
Tomas also explained how single blade props are the most efficient. As due to there being only one blade, by the time it does 360º it has clean air again, so uses 100% of its capabilities (approx.) They can”t be used however on large scale aerobatic models for example due to the size of the weight needed to counterbalance the single blade.
To calculate what size 3 blade prop we require, they explained that it is simply a case of multiply the diameter x 0,9, and reccomendably increase the pitch by 1-2″. Example:
32*10 2 Blade
32 x 0,9 = 28,8. So 29″ Diameter.
29*10 – 29*11 or 29*12 for 3 blade
As well as their propellors, Mejzlik”s slightly less known spinners are of the same quaity, amazingly light weight and with the same perfect carbon finish. Tomas explained how they have a new method of making their spinners, which makes them just as strong, but lighter by forming the spinner both from inside and out. Not only this, but their new series spinners also have aircraft grade aluminium backplates, meaning that they are stronger, allowing more metal to be milled away, making them even lighter.
As a reminder, Mejzlik also make other high quality carbon parts such as undercarriages and spats
Another interesting part that cought our eye was their electric motor supports, designed to stand all the torque of the motor, assuring a correct and safe mounting
Thomas also explained that the new Quad and Octo copters (helicopters with 4 or 8 rotors) have caused a great boom in the market, and they have had to design an entire new line of carbon propellors for these helis. Users have commented on more silent and smooth running, as well as an increase in flight times
It was also interesting to find out that Mejzlik have been approached on different occations by companies looking to have special parts made in carbon, and wanting the best possible finish are going to Mejzlik. Just one example could be this part, a specially moulded air intake for the Porsche 911 Carrera!
Due to Mejzlik constantly improving their products, they are interested in feedback about their products, along with ideas for improvement or development, as well as constructive criticism, so please feel free to send your comments either to them directly, or email me at PickeringRC@hotmail.com and I will be happy to forward your comments on anonymously.
In the mean time, Mejzlik have such high quality products, and many of them are often overlooked, why not take a look at their new webshop at: