Geoff_H

The Americans call it the English system. When I worked in Texas we had an engineer that would always convert English/imperial system to metric system, do all calculations in metric then convert results to English/ imperial system. Claimed it was easier.

Should be calcs not cakes

Vertical loads that are supported on the ground had no trouble whatsoever to even a small slab full stop the problem arises when you lose support underneath the slab and it becomes a cantilevered beam. If this happens you can easily crack the slab this is what usually cracks slabs. I find it when I go to a structural engineer and force him to show me his cakes so he's not over designing it that I save a lot of money in steel

Sorry my advice is consult an engineer. The edge support or restraint will determine what shear needs to be resisted at edges. I am a mechanical engineer and I always consult a civil/ geotechnical engineer on design. The thing that will trash the job in a few years are the assumptions that are made. An engineer with experience will guard against making an assumption that this slab is just like one seen on the other side of Australia. Best to find an engineer that works on structures near where your hangar will be built. Don't put pads under the slab unless specifically designed and built correctly. They can actually make the slab weaker

Sorry my advice is consult an engineer. The edge support or restraint will determine what shear needs to be resisted at edges. I am a mechanical engineer and I always consult a civil/ geotechnical engineer on design. The thing that will trash the job in a few years are the assumptions that are made. An engineer with experience will guard against making an assumption that this slab is just like one seen on the other side of Australia. Best to find an engineer that works on structures near where your hangar will be built.

Maximum weight is 7ton. Pressure on concrete would be the tyre pressure. Only problem is bending moment from ground under the concrete not fully supporting the concrete. Tale the 7 tonne point loading ( actually less when shared between wheels) to a civil engineer or geotechnical engineer. He/she will probably tell you off the top of his head if he knows where the hangar is to be built ( they have charts about ground support capabilities).

Great!

I also think that you would be better with "time away". I know that it has helped me enormously. Solved problems, got enthused again. Don't burn your self out. Nothing to do with perseverance. Just as your body needs rest so does your mind.

Why not sell a share of the aircraft? The new shareholder gives money, maybe supplies the engine or similar, and finishes the aircraft, then you both own it. I may be wrong. I think that with a mentor you may have a much better experience. You need moral help. I have been there and would have given up except for moral assistance of other builders

I recently had 3 problems in my project. I got very disappointed. I left it alone for 3 months and did "honey do's". Two solutions have come to me and I am back building. Danny when you get a problem why don't you publish it here. Maybe with pics and manual extracts. I am sure that we would all be here for you. And I expect that the problem could be solved. Maybe you need to get assistance on techniques or methods of manufacture. I am sure that you will get the job done and be so proud of yourself. Don't sell, you will probably loose money and self esteem. Keep going. Show us all pictures of your progress.

Why not sell a share of the aircraft? The new shareholder gives money, maybe supplies the engine or similar, and finishes the aircraft, then you both own it. I am guessing that the problem that you are having is with engine and avionics. I may be wrong. I think that with a mentor you may have a much better experience. You need moral help. I have been there and would have given up except for moral assistance of other builders

Danny, Where have you got the project to. Related to the 3-week build?

Danny what is giving you the most problems? Is there anything that we can do remotely?

https://www.gap.aero/pdf/bushcat/3week-Bushcat.pdf So how many weeks have taken Danny? Is this a real estimate?

I am about halfway through my own design, aerodynamically it is very similar to an existing design. Before I began I built many test pieces and tested them to destruction. As it is a composite design I have difficulties getting design values for calculations. So it is a little heavy. At one stage some years ago I considered doinfya masters in composite design criteria. One big problem that I had is what would the shear stress of the main spars. Assumed that the max shear stress was the max epoxy stress. The cloth may add extra strength but I went on the side of safety, it now seems a little heavy. It is ok to use the load test to make sure that things are ok...but... What if your dynamic loads are different to the static loads. Throughout my career I found that it's not the calculations that bite you in the backside. 99%of the time, it is the incorrect assumptions. The math will make the aircraft lighter. I was taught that anyone can build anything, but an engineer should be able to do it for far less cost, math can help. If you are designing your own design please get someone to do maths on the critical parts. Even a strut can buckle in compression but be super strong in tension. Negative G's may buckle a strut. Fibreglass structures are notoriously weak in shear. Using mathematics can also stop making 6 parts before the final is made, I have done the math and still had to make the part 6 times before the final that works. However experiment experiment experiment. I have been using carbon infused nylon and 3d printing. I have used it in some parts ..I still have reservations, but they are light. Fantastic for cheaper materials and jigs and alignment tools.

Efficiency often depends upon the design. Our turbine had moving pitch blades that made compression variable. That changed efficiency. But not sure of aircraft GTs air flow control.

Sorry second time is edited a little better. Voice to text is something that I still have to master.

For those who don't know how a gas turbine is limited. Stiometric combustion of the fuel produces a temperature higher than any gas turbine blade known at the moment can withstand. To bring the temperature of the gas entering the first stage turbine the mixture is over aired. Airr acts as a cooling agent. The higher your blade can withstand the less air you have to pump in the compressor so the higher the temperature, the higher the efficiency. Also affecting efficiency is the pressure at which the compressor generates, the GT worked on had a compressor discharge pressure of 250 psi. The pressure is just like the compression ratio of a piston engine the higher the pressure the more efficient. Out of a typical gas turbine the oxygen in the exhaust gas will be around 16%. As this oxygen just gets taken in and heated and exhausted at quite high temperature, a lot of energy that could be going to the output shaft is just wasted. The material of blades the get around 30 to 40% efficiency is exotic the manufacturer is also exotic Pratt & Whitney have a duct up the centre of the blade with small holes radiating out to the leading-edge so that a small layer of cool air runs along the leading edge of the blade. These materials are exotic the burner I found more expensive than the actual blading. For a 60 megawatt gas turbine used for electrical generation the rehabilitated cost of burners for the machine was $5000000 the cost of blades for the same machine was around $5000000. The control system of a gas turbine or run with as much fuel as you can get in before you reach the turbine inlet temperature Max for blade life. All expensive stuff.

For those who don't know how a gas turbine is limited. Stoica metric combustion of the fuel produces a temperature higher than any gas turbine blade known at the moment can withstand. To ring the temperature of the gas entering the first stage turbine the mixture is over Ed air acts as a cooling agent. The higher your blade can withstand the less air you have to pump in the compressor so the higher the temperature the higher the efficiency. Also affecting efficiency is the pressure at which the compressor generates the ones I worked on we had a pressure of 250 psi full stop this is just like the compression ratio of a piston engine the higher the pressure the more efficient. Out of a typical gas turbine the oxygen in the exhaust gas will be around 16%. The material of blades the get around 30 to 40% efficiency is exotic the manufacturer is also exotic Pratt & Whitney have a duct up the centre of the blade with small holes radiating out to the leading-edge so that a small layer of cool air runs along the leading edge of the blade. These materials are exotic the burner I found more expensive than the actual blading. For a 60 megawatt gas turbine used for electrical generation the rehabilitated cost of burners for the machine was $5000000 the cost of blades for the same machine was around $5000000. The control system of a gas turbine or run with as much fuel as you can get in before you reach the turbine inlet temperature Max for blade life. All expensive stuff.

Search Micro Turbine. They are available, reliable, and can do 200hp. They are industrial so have a bit of conversation. I couldn't afford them. https://en.wikipedia.org/wiki/Microturbine

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.alstom.com/press-releases-news/2012/6/the-new-alstom-gt-24-gas-turbine-shipped-to-mexicos-el-sauz-combined-cycle-power-plant&ved=2ahUKEwicgKvnmrTyAhVb63MBHeRSC20QFnoECAYQAQ&usg=AOvVaw31Xwr2oa8X01zyEdA972BS A subsequent burner, industrial size. I think that GE also have one.

I must admit that Microturbines are proven. A friend was involved with them. I got the price....$$$ compared to piston. Maybe one day I will design, but not build ( far too old lol) a dual burner turbine. I maybe wrong but for the addition of a burner over conventional turbine they might just have less weight for the same power.

Turbaero have you guys looked into using two stages of burners. One before the first stage turbine and the other before the second stage turbine. All blades in both stages would have to be of material and construction that is what you would make them now. But this would allow a theoretically double the amount of fuel to be burner for the same compressed air flow. In fact it would be significantly less than double butuch higher than single. I don't know much, one day I may get enthused and make a stab at calculating how much. Efficiency gains are obvious with so much less power needed for the compressor. Not my idea. In the later 90's ABB designed a very large GT using this theoretical design. An enthusiastic salesman sold a power station full! They didn't work as well as expected. The liquidated damages nearly sent ABB broke. I have always thought that this might be a simpler design than using turbine exhaust to heat turbine inlet air. Might be cheaper, but I doubt that. Blades and burners are not cheap.

Maybe you could help me. The slower that a turbine goes the more power it gives out. Why does the PT6 have a gearbox rather than just run the turbine slower? I have quessed it is for efficiency reasons. One day I will sit down for a day or two and try and calculate it. Any thoughts?

Class is a function of tit. Most commercial turbines in Australia are class C. GE have a class H. The turbine that I worked on was 180MW, and had blade leading edge cooling. I believe that you are using heat recovery, a great idea. Best of opportunity. Great to see you succeed.