Geoff_H

Far too general a statement. Quality gas turbines can get to 40% efficiency with expensive Blade material and multiple compressor stages. Higher than all but the most sophisticated piston engines. Cheap turbines do have poor fuel efficiency.

I thought about the comments about the dreaded thirst of gas turbines. I looked at the power increase required to increase the speed of a Mooney 201. Let's look at increasing the speed by 50%, to 300mph. Drag increases by the square of the velocity, horsepower is proportional to the product of the speed and the force. Hence to power a 50% increase in speed I must increase the power of the engine by 1.5 raised to the power of 3, around 3.3 times. The Mooney would need to increase its power from 200hp to 660hp. Plus whatever drag would increase by owing to increasing main spar strength and up isconsequent weight. So apart from finding a 660hp piston engine we would probably need to go to a gas turbine. If it has the same thermal efficiency as the piston engine we are going to burn 3.3 times as much fuel. For the same range we are going to require increased weight for the extra fuel which will incur more drag etc etc. The exercise looks something like a TBM 800, a Mooney designed aircraft. Speed alone I creases required horse power by dramatic amounts, probably why turbines seem to be very thirsty.

Actually the aircraft turbine derivatives that I have worked on were more like 93,000hp. The largest non derivative I worked on the desighn was approx 250,000 hp. Stationary turbines are also much more efficient using water injection and evaporative cooling of inlet air.

I got a quote 10 years ago for refurbished blades for a 60MW GT of $6M. Cheap blades will not take high temperatures hence low efficiencies high fuel consumption.

They are bigger and power big aircraft demanding large power. Low temperature inlet turbines will have significantly less efficiency. We know of no material that can take the temperature of stoichiometric combustion. They would simply melt. So we must cool the gas out of the stoichiometric burners with air that bypasses the burners. A GT compressor must compress much more air that doesn't contribute to power, just cooling. This means that the efficiency drops with lower allowed turbine inlet temperature. High temperature blading is expensive, single crystal, and usually with small holes to the leading edge of the blade to provide a cooling blanket to the blade. Expensive.

A quality GT will have a compressor discharge pressure circa 250psi. That is 16:1.

A high quality turbine is more efficient than an aircraft piston engine. I think that the turbines usually develop so much more power and capable of higher speeds that have an exponential power demand. The Rolls Royce Trent engine that was powering a generator was around 40% efficiency. GTs are very dependants upon air density so they somewhat in efficiency, from day to day.

I think that the dipping in the paint is a great idea. Just be careful that your favourite colour may fail because the paint carrier that disappears on drying is conductive. I would not expect so but I am not really certain what is in the carrier.

Yes a good quality Meyer with a very high input resistance would probably indicate a conductive paint. A Fluke or equivalent meter, not a cheap Chinese one. First measure the substrate, without any paint, push the probes as hard as possible into substrate. The resistance should be infinite. Then paint the surface, at dry remeasure in the same spot, if the resistance is less than infinite do not use that paint. I have made a resistor by mixing black carbon ochre with epoxy. When set I could measure resistance across the part. Another was is to download an RF Meter on Apple/android and see the effect of putting the phone in a painted box. Geoff

Recupetators weigh! Stationary engines of larger size don't use them because of pressure losses in exhaust gas, pressure loses affect turbine output.

I worked in Florida on the design of 185MW gas turbine. The efficiency of a gas turbine depends heavily on the maximum turbine first row of blade temperature. To get high temperatures you need very exotic blade materials, as a rule of thumb the more you pay the better the efficiency. These people are getting better efficiency by using heat from the exhaust to increase the volume of compressed air so not so much fuel is used to get to maximum temperature. It is used by a company called micro turbines, small medium efficiency turbine manufacturer. I hope the guys are a great success.

Carbon black paints are offer used as RF absorbers. Other forms of colouring may have been used on your GPS antennas. I would find out what pigments are used in any coloured paint and check the conductivity of the pigment before applying them else you create a Faraday cage.

Aircraft are expensive and Beavers are very more expensive. Must be higher maintenance costs.

When Garmin upgraded the GNS430 to WAAS they had to build a totally new processor board to make a GNS430W. It is a lot more hardware than additional transmitters to cancell out the noise in the receiver, it is apparently a whole new performance of processing hardware. I found this out after forming out $10k to have the processor board upgraded.

Black pigment is often carbon, I expect that would attenuate significantly. White is titanium dioxide, I think that as it is an insulator and non conductive why every GPS receiver that I have ever seen is white

The Garmin have don't paint on their body. I think that some paints can attenuate radio frequencies.

The Dynan uses WAAS. Speed of operation is critical and I think that we use waas devices for speed of operation and other technical reasons I upgraded a GARMIN 430 to 430W for technical Operations reasons. Hence I have bits left over

Hi Skip, well I was interested in augmenting my project withe a possible repair project, but a place to put the repair job plus a hostile minister of war has made me put my project on hold as she wants the house without any faults before I go on. I expect to only have an RAA licence by then hence my changingind engines to a single. I am not expecting to use many things including heaps of stuff for a quarter built cozy IV. I have given away a significant amount of stuff that I will never use, if I don't the other half will trash it all if I die first, she thinks that will make me angry, how could it I will be dead lol. Just a point that I expect that any GPS receiver will connect to your GPS if it uses the naval code ( and I think that most do). However if you get a non dynan make sure that it is WAAS. Geoff

Hi Skippy I didn't realise your craft was composite . I also have a garmin one like the picture above ( but with plug fittings ) again hanging around. I think that it is waas. Let me know if you are interested. Geoff

A comant CI 2480-201. Don't know if it would be comparable. But it is hanging around doing nothing for me. Let me know if you are interested. Geoff

My project is composite. No need for it

It is sitting in my workshop. Very cheap to buy

Don't forget that that CofG must fall within the triangle formed by all three wheels (or skid). As well the distance between the Cof G and the main wheels axle can affect ground handling The spitfire and one of their German counterparts have been reported that theain wheels were as too close to each other and increased difficulty of ground handling.

At the end of the day the location of the CofG to the Aerodynamic lift centre has to be the same either configuration. There maybe some different moments on the aircraft owing to nose wheel drag, just make sure that at landing speeds these are easily compensated by available tail moment

Hi Skippy I have a dual VHF/GPS antenna. I bought it but it did not get into the air. I upgraded to WAAS. This is not a waas antenna. Let me know if you are interested. Geoff