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Geoff_H

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Everything posted by Geoff_H

  1. Geoff_H
    Please take not that the cooling air will be blanketed from the wing flow. This technique is used in high performance gas turbines where a layer of air is run over the first row of blades to blanket them from hot combustion gas. Is
  2. Geoff_H
    I was not very good at fluid mechanics, but one principle has stuck with me, the flow velocity of a fluid over a surface is zero at that surface. With respect the problem at putting a heat exchanger in the wing leading edge is the velocity at the leading edge will be zero hence: "Turbulent flow, due to the agitation factor, develops no insulating blanket and heat is transferred very rapidly. Turbulent flow occurs when the velocity in a given water channel is high. ... Laminar flow develops an insulating blanket around the channel wall and restricts heat transfer." Best regards Geoff
  3. Geoff_H
    Would the talk about seat belts etc before take off and emergency outfield landing constitute passenger carrying? Can't think of anything else I did. Did my licence in 1980. Did a lot of FullSAR, SARTime and landing at international airports. Very different flying then.
  4. Geoff_H
    All this passenger thing is a crock of...... It is somewhat intuitive, more important is cockpit management in case of emergency, I have used it once and should have on possibly my worst landing ever in front of a control tower. More important is landing without an ASI, I have had to do it twice. I was not prepared the first time on a relatively short runway, second time on a long runway. No GPS on first but GPS on second.
  5. Geoff_H
    I did not get any passenger in my PPL when I did it in the early 80's. It came intuitively. I had a few times that I had to exercise it. I took a first ever flight passenger. I was worried what his reaction would be, worked out a way to get immediate clearance to land without him being worried by the request. He loved the flight, even the 60deg steep turn I did. I do however remember when learning outfield emergencies that it was an outfield landing, not a crash landing in my passenger brief. Maybe that constitutes passenger management.
  6. Geoff_H
    In explosive atmospheres the explosive gas can and will travel up the wire into a safe area ( not so safe then). For safe installations there are sealing kits that use systems to stop the gas, only a few inches long but stop wire transfers.
  7. Geoff_H
    Soldering can be done properly, but the joint has to be restrained, that's extra weight in the aircraft. It has to be done properly, a crimp tool takes almost all of the chance of error out. Space craft don't vibrate after the trip to orbit, long term fatigue cracks would not have time to occur, atmosphere almost certainly not corrosive.
  8. Geoff_H
    I should point out that when comparing HV cable connection it was with respect to corrosion in the joint, not electrical conductivity. HV cables come with a steel cable for strength with conductors ( often anodised aluminium) wrapped around the outside. At these voltages electrons repel each other and crowd the outside skin. At these voltages you don't get electrocuted you get burner as the electrons run down the outside skin of the body. As another aside the aluminium conductors are often coloured to fit in with the surroundings, that makes them hard to see from the air as well. Makes low level flying really dangerous.
  9. Geoff_H
    I definitely believe so. Same technology just very different sized crimp machines. The high voltage cable swayed came with petrol driven hydraulic pumps and piston driven swage dies. My crimper is mechanical advantage crimp that is getting harder to use as old age sets in 😒
  10. Geoff_H
    A properly crimped joint is a galvanic bond and will only corrode around the edges. High voltage (330/500kv)I we are crimped, often near salt water, they are not known to collapse from corrosion of the joints.
  11. Geoff_H
    A properly done crimp does.
  12. Geoff_H
    Yesterday I had my latest encounter with soldered joints failing. A classic mini that had an upgrade to a solid state fuel pump, one we often see in aircraft. The short leads from the pump had an extension soldered to extend their length to a plug. Sitting near the rear suspension the pump even has its own vibration isolation mount. The joints (positive and negative) had heatshrink around them. Finally failed several years after installation. Unfortunately 200km from home. I am just glad it was not an aircraft. A motor mechanic soldered a new pump in, he did not realise what the failure really was. The owner and I have a date to replace the soldered joints with crimped ones. With a professional crimp tool!
  13. Geoff_H
    Surely everyone knows that space aliens actually gave them antigravity stuff to build the pyramids. 😳
  14. Geoff_H
    I think seals will be a problem. The surface velocity looks like it will be high, this will contribute to wear. Air cooling claim was suspicious, and we only saw the engine with apparently no load. However the concept fascinated me. I have an unusual curiosity, just ask the wife.😏
  15. Geoff_H
    Not defending it but there is video at the end of the clip that shows something like this running. I don't think that the wear at the max speed would be acceptable. I just found it an interesting concept.
  16. Geoff_H
    https://thekneeslider.com/omega-1-internal-combustion-engine-is-light-powerful-efficient-and-clean/ This engine is very interesting.
  17. Geoff_H
    I did heaps of calculations on which is lighter an epoxy/ cloth design or aluminium. Strangely aluminium was the lightest, for a very unusual reason. The shear stress of aluminium is around 60%of the UTS. With any epoxy/cloth the maximum shear is the shear stress of the epoxy, after all that is in shear between the layers without cloth holding it together. When I designed the main spars they were heavier than aluminium by a significant amount, just to ensure that the spar would not fail in shear. A lighter spar could have been made using a carbon/Kevlar intertwined cloth. Still a little heavier than aluminium. The monocoque shell needed a foam core to get a good Euler's buckling force. Boeing don't use epoxy, a much high strength "glue". I am however a proponent of FRP.
  18. Geoff_H
    To convert to RSS what are any additional costs to flying instructions?
  19. Geoff_H
    Skippy You are after a high performance cooling system, one which cools the engine continually but presents the least drag on the aircraft. In my 50 years as an engineer I have not seen a totally new design be got right on the first design. What I think that you will need is to make a cowling then instrument it and data log the data probably including spaces inside the cowling when miscellaneous equipment such as fuel lines may lurk. Amongst the temperatures that would need to be monitored is all cht, inlet air temperature exit, air temperatures air flow measurements etc. I worked on the design of the fluidised boiler at Redbank Power Station, the first of its kind in the world, we changed that design many times over a year or more before we got it as good as it could be without tearing it down. But I do wish you the best of luck with what you choose. Geoff
  20. Geoff_H
    My cri cri similar project just puts the cylinder fins in the airflow, hopefully enough flow at idle. Much simpler, more drag, as said earlier it's all a compromise.
  21. Geoff_H
    "That's all fine but the math doesnt lie." That is if you have the right maths. After years of calculations and observations of actual air flow in ducts believe me it is far more complex than simple maths. Everything from zero wall velocity to air viscosity etcetera. Best idea is to observe what works on a similar installation and copy it
  22. Geoff_H
    Personally I think it is but I am not writing from any point of knowledge. It definitely has more strength at temperature. 95% of what I use is epoxy.
  23. Geoff_H
    Many years ago the epoxy landing gear on the Cost IV often sagged with time. The cure was to 'cure' the epoxy by constraining the legs and heating them for several hours without any load on them. The suggestion was to stop them in black plastic and put them out in the summer sun. It was claimed that there was no sag on undercarriage legs so treated. I don't have details not numbers. It does make a little sense when you look at prepeg fibreglass with uncured fibreglass is placed in a mould then heated to cure it.
  24. Geoff_H
    It is a polyurethane foam with glass/ epoxy skins. Attachment to the glass epoxy using a glass balls/epoxy mix, that never failed. The foam failed in shear at the centre. I have searched for data on composite strengths, the best advice I got was that data was very expensive to get and guarded very much. Some years ago I had organised to do a Master's in Aeronautical, my project would be to determine a calculation system for composites. I got a contract just as I was about to start, never got back to it. Too old now.
  25. Geoff_H
    Thanks, great information. I am only aware of people making composite aircraft using a skin of epoxy glass or foam with a fibreglass double skin. With the exception of the very advanced aircraft construction similar to the Boeing aircraft. I have been building using a foam covered with glass/epoxy. I have been unable to determine the strength of the combination by calculation. I quess a combination, construct it and then test to destruction and use the values found in the test as the value for design. I think that finite element analysis maybe the way to go. All my tests have failed by shear stress at the centre of the foam. The layers of glass/epoxy remained intact in the testing, but it was deformed. But will the structure take significant cycling? Will it fatigue? Maybe I should make a test rig.
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