meglin

Thank you for your comments. It is customary for us to separate the service life and the resource. The service life is usually measured in years according to the calendar. And the resource is measured in operating hours. Perhaps you use a different word? I was trying to describe the operation of the blade. The blade is subjected to external loads for bending, stretching, torsion, abrasive wear. During static tests of our old blades, we brought them to break, the forces were 9-12 tons. Now these efforts are even greater.

The pictures show: 1) a saber-shaped blade with a diameter of 1600 mm for Rotax-503/2, 58. It works perfectly on both 582 and 912-100. 2) a straight classical blade on a Czech aircraft with a Rotax-912-100, diameter 1880 mm. Huge thrust on takeoff. 3) elliptical blade. I don't have exact data from the operators. They say it's no worse than a saber-shaped one.

Three forms of blades are enough for us: classic paddle, saber-shaped and elliptical. The saber-shaped one prevails, it is quite logical for the existing circumferential speeds. Noise is reduced, its tonality changes, and efficiency increases. There are different opinions: Hungarian pilots measured an increase in thrust of 25 kg, American pilots-by 10%. It is difficult to accurately measure yourself. The important thing is that there is a clear increase. But the blade does not only create traction. It also fights abrasive wear, it bends and tends to break in conditions of changing temperature, humidity and ultraviolet light. To do this, we cover the blade with a solid gelcoat, protect it with stainless steel, and a powerful spar is required inside the blade. For a propeller, the resource, strength and rigidity are important. Today we have removed the resource restrictions. Each operator, after the development of the assigned resource, has the right to independently extend the resource for the next 100 hours. The elliptical blade has so far few admirers. But its form is the most correct. I hope that the comparative tests will explain a lot to us: https://www.stolspeed.com/nid/46

I agree with you. We have successfully used wooden propellers with a diameter of up to 68" on non-high-speed aircraft. We have also developed and use especially strong carbon fiber blades, the propeller diameter is 1620 mm = 63.8". They have been in operation for more than five years. Unfortunately, none of the engines that work with us has worked out the assigned resource.

https://www.stolspeed.com/nid/46 I hope that the test results will be interesting for everyone.

It is also worth comparing the strength and stiffness of the blades due to the fact that most aircraft with pulling propellers have critical clearance indicators, and the propeller, even with careful operation, always gets grass, sand, and stones.

It would be very interesting to compare the performance of our propeller with the propeller of the same size discussed here. Starting characteristics, climb characteristics, cruising, maximum, noise, vibration. We solved the problems of using a propeller on Jabiru already 5 years ago, having developed and launched the production of especially strong blades made of pure carbon fiber.

I'm sorry that I reminded you about this side of an absolutely beautiful production. I adore it myself - it is closest to art. But fewer and fewer people want to do this. The modest money that can be earned on this is given by hard work. I am very glad that we gave someone joy.

In our entire history, we have never encountered a rupture of a wooden propeller. This is physically impossible, because the margin of safety is huge. There may be a longitudinal stratification due to poor-quality gluing of layers, such cases can be 1 out of 1000. But transverse destruction - never. Perhaps the propeller was intended for scenery, like these?

This is a very difficult production. Dust, noise, toxic fumes. Hard wood varieties are very difficult to process. We usually use beech, oak, ash. Oak forms small needles that dig into the skin. At the finish, we must paste over fiberglass to exclude the influence of humidity. The blade edge is necessarily protected by a stainless steel strip. The quality depends on the hands of the master, on the wood, on the temperature in the room and the humidity of the wood, on the quality of the adhesives. We use only epoxy glue with maximum strength. All this increases the cost of the final product, but allows you not to worry in harsh operating conditions at temperatures from -50 to +50 degrees Celsius. For Jabiru engines, we have produced many samples of propellers with a diameter from 49 to 59". And we have achieved good performance indicators. But there is a factor that completely cuts off this business. At the request of the EU, our post office has limited the dimensions of parcels to 41'. Only very expensive courier services remain. For remote countries, there is only one way out - the use of composite propellers with especially strong carbon blades. The saber-shaped shape of the blades significantly reduces noise and allows the use of propellers with a diameter of 63.8". The thrust increases, vibrations decrease, there are no deformations of the blades from temperature and humidity changes. They are placed in a small box and can be delivered for a reasonable fee by regular air mail.

A great decorative propeller! working with solid wood is a little more difficult. We use only epoxy glue. Additionally, we paste over fiberglass and glue the steel protection. A lot depends on the correctness of the design and the hands of the master.