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Geoff_H

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Everything posted by Geoff_H

  1. Geoff_H
    There is no such thing as a dumb question, only dumb answers! With that I will prove my stupidity. A long exhaust will have more internal and external drag! The internal will reduce HP except where it is done to tune an exhaust to increase cylinder clearing rates. Most noise comes from the propeller so I would expect only slight decrease in noise with a weighty, loss producing system. I actually liked the Vxx engines with each exhaust port just ducted individually outside the cabin. The guy that designed the Cozy IV (taken from a LongEze by Rutan) recommends that you only add to an aircraft anything that when you throw it in the air it stays up. Bit extreme maybe. Saying that my little two strokes are getting tuned exhausts, but for power reasons.
  2. Geoff_H
    Any reply on blade material and cooling method? This is what affects the efficiency the most. When at Siemens we paid for the blade technologies to Pratt and Whitney, it involved exotic materials and very fine cooling holed that delivered uncompusted air to the leading edge of the blades so that the sir formed a blanket between the cooled combusted air. OK we were after 45% efficiency, but lower quality blades can only take a lower temperature and it is this temperature that controls blade life and efficiency. I am truly interested and would like you to succeed.
  3. Geoff_H
    A 25% efficiency is what the numbers suggest. Low for a modern gas turbine. Having been involved in the design of gas turbines for Siemens in Florida I can see that a low efficiency GT is possible with basic tools. The TIT for such efficiency is quite low, what are you expecting and what materials and cooling are you using for your Turbine Inlet blades? The blades and combusted are the expensive bits. I hope that you can get the price so low, but that is not my experience but am hoping that you can!
  4. Geoff_H
    The gas turbine and the piston Engines have a lot in common. The compression ratio, one from displacement the GT from how good the compressor is. A high efficiency GT will generate 250psi at the combustion chamber. The high efficiency GT has a compression ratio of around 15 to 1. As with a piston Engine the GT be less effective at altitude by the same ratio as a piston Engine. So a high efficiency GT will use a lot less fuel at altitude.
  5. Geoff_H
    Gas turbines are great. Providing that the compressor gives a high pressure and the cooling of the blades allows a high inlet temperature. Otherwise the weight of the turbine is low but the fuel load for any travel distance is huge.The Cri Cri has had several models built with model jet engines ( a Turbine with fewer turbine blades, well almost) had elementary low pressure compressors, and are extremely inefficient, limiting flights to not much more than flight minimum reserves.
  6. Geoff_H
    A person once told me that the two most exciting days in the ownership of an aircraft was the day you bought it and the day that you sold it.
  7. Geoff_H
    Having been in the business of Commissioning Manager on large sites for many years I was responsible for site safety procedures and enforcing them. I found that it was impossible without accountability and trace ability. Persons that transgressed the safety rules were sent for retraining, several transgressions resulted in banning from site. Documentation was essential. Everybody had to complete check sheets, these sheets were not tick a box, all too easily done and not traceable, a value whether it be a number or a quality were required at all times. These values were subject to frequent spot checks. The end result was commissioning without any errors, seems impossible but true, the cost of documentation was large but the overall cost was cheaper than previous methods. For safety we should be looking at the management of safety, not the Hi Vis jackets etc.
  8. Geoff_H
    I needed an ASIC Sea Port Clearance, you can use your aircraft one as the ID and security check provided that the Port expiry date will coincide with the aircraft ASIC. Hence no security or identy cost. The Port one offered was only around$60 cheaper! So how much does it cost to make an ASIC card? We are told that they are just covering costs...Does that mean that they are so inept at making the final document or are they just making a profit that they are not telling us about. CASA should justify their costs and expenses, a little transp
  9. Geoff_H
    Many documents on aircraft fibreglass finishing for aircraft talk about Featherfill as a final filler. It is nearly $300 per US gallon. I can't find any data on its weight compared with the general automotive style spraying putty. Is Featherfill lighter than spraying putty? Does it have any other properties that make it better to use? Has anyone had any experience with Featherfill? Any one used spraying putty?
  10. Geoff_H
    I have been trying to read the CAO's that apply to RA. What a convoluted set of documents. I don't think that I will ever understand them.
  11. Geoff_H
    I tend to agree with the 3% chance of finding those 3 items. I am quite prepared to accept a project that is well on its way or an aircraft needing an engine change, I am building a composite but its going to take several years, I have spent nearly 2 years on the design, made my first tail, far far too strong on failure testing so redesign and remaking. I really want some thing to fly until the composite is completed.
  12. Geoff_H
    Budget is around the $30k mark. I used to pay$5k per year for hangaring. Now that I am retired I was hoping for an aircraft that I could trailer home, if not a smaller aircraft that would cost less to hangar. Single seat would be OK, a project nearly complete or just needing some work would be good. Not sure that timber is my bag but either metal or composite would be suitable. I would prefer something that cruised over 100 knots. The sonex and Onex looked good, the Onex probably would cost a lot less to run.
  13. Geoff_H
    What operational and maintenance differences are there between a 19- and a factory made aircraft?
  14. Geoff_H
    Thanks, that answered my questions in another thread about the types of RA requirements and aircraft. Does it mean that a CTA is definitely out of bounds under all circumstances except emergencies?
  15. Geoff_H
    I am still a GA pilot, but now retired and my beloved Mooney sold I am looking for a smaller simpler VFR aircraft. Something that costs less but still gives that joy of flying. My wife hates flying so long distance is no longer a requirement. RA flying looks to suit me, however I am having trouble understanding the various aircraft tail number designations. What's the difference between 28 and 19? Why was the Morgan numbers changed. I want to limit my spending, which aircraft type should I buy?
  16. Geoff_H
    Any noise cancelling is what I would buy. I have two Bose, overpriced but good. And two cheapest type, virtually useless, give to passengers I have a grudge with lol
  17. Geoff_H
    One of the reasons for experimenting with nylon is its great engineering properties. One is its low coefficient of friction, that makes it good for low speed gears and similar. Having a lower interlaminar strength, similar to glass/epoxy structures. Hence design features such as shear stress needs to be taken into account, with metals the shear stress is so high that it's not usually needed to be calculated. Nylon is great for low speed gears where the laminations are at the vertical plane to the axis. The dimensions maybe not great in low cost printers but I have read that you can machine nylon parts, I have not tried to do this yet. I will make a part in the new year and put it in the lathe and see the results, stay tuned. But don't forget that you could make a composite aluminium/steel and nylon part using the advantages of both, Nylon can be cemented or welded to other nylon parts to make a part much larger than the bed size. I believe that this is one of the most exciting technologies to come to home aircraft building.
  18. Geoff_H
    This is a picture of the test part for the feasibility of a nylon printed flap. Notice the curve of the leading and trailing edge this could be remedied by a themally constant environment, or a heated box around the printer. It is light but not strong enough.
  19. Geoff_H
    This is a picture of the test part for the feasibility of a nylon printed flap. Notice the curve of the leading and trailing edge this could be remedied by a themally constant environment, or a heated box around the printer. It is light but not strong enough.
  20. Geoff_H
    I tried to print a flap. Each segment to be made so a thin section aluminium tube could hold together each 200mm length of flap. To get it light I had thin walls of the flap. Printed one in nylon. It did not work, the youngs modulus of nylon is low compared to aluminum. With equivalent weight the nylon part was not Ridgid enough and flexed significantly.... Maybe a different material for printing will help some day.
  21. Geoff_H
    At present it is 200 x 200. I use hairspray on glass for nylon and a variety of fiber based plates for other materials. For PLA I use masking tape.
  22. Geoff_H
    I have a modified Aldi Cocoon.
  23. Geoff_H
    Never tried the auto adjust features. I always watch the first layer very carefully and adjust as required to get best bed adhesion. I manually adjust temperatures during the print, I should put the changes in the GCode. I must do this one day. I spend heaps of time watching the print.
  24. Geoff_H
    Yes. The temperature is destroying my Teflon guides, but I have a metallic hot end on the way. One of my big problems was curling and separation of the part from the bed. I did some bed temperature measurement and found that the bed temperature was between 20 & 30 deg C below the measured temperature. Getting much better results now. Only nylon has the temperature strength and chemical resistance required. Early parts split along laminations when hit with a hammer on the vyce. To get better built quality I am building a thermal box for the printer
  25. Geoff_H
    I noticed in another thread that a discussion on 3D printing came up. I have been experimenting with printing various parts for my project. I have found that the weakest part of a printed part is the layer bonds, hence I would not use it for undercarriage parts, but for throttle quadrant rudder pedals and the like it seems to be OK. Weight is significantly lighter than aluminum parts owing to the lower density and 'honeycomb' style centre. The minimum material that could be used is nylon. Printing nylon is not for the faint hearted with much experimenting to get an acceptable product, dimension and surface finish often lead much to be desired. However my products are getting better as I solve each problem. I have had to modify my printer several times to improve the part quality. I designed each left using 3d AutoCAD then transfer the design to an appropriate language for the printing, quite cumbersome. With time I expect to be making parts that can be service sensitive in requiring strength and endurance. Maybe undercarriage parts one day.
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