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Bruce Tuncks

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Everything posted by Bruce Tuncks

  1. Bruce Tuncks
    When you look at an ME 109 through the eyes of a Jabiru pilot, you see a frightening thing. High wing loading, narrow u/c, nose blocking forward view at high angles of attack are just the obvious ones. I'm not surprised at that comment cooperplace.
  2. Bruce Tuncks
    Yep, I have always had that beige build-up, what with 18 years of avgas running. It has flaked off and so not continued to increase , and it has not badly effected the leakdown results. But right now, I am trying an experiment running on mogas. So far, I can detect no difference in the way the engine runs, but I am hoping it will clean itself up inside. Thanks Glen for the info about how different cleaners worked. What do you think about just hoping that mogas will do the job? And thanks Ken for the info about that gen 4 engine on mogas at Gawler.
  3. Bruce Tuncks
    I reckon birds and fish have a faster reaction time than we do... and the message has less distance to go. I sure agree it looks like they have one mind though. The one thing I am sure of is that this could not be proof of ESP or suchlike. A few years ago, Dick Smith put up a big cash prize for any psychic act. No takers! The terrible thing is that Dick was criticized by "believers".
  4. Bruce Tuncks
    Looking at Bunnings and the big W, it is hard to find anything NOT made in china.
  5. Bruce Tuncks
    Are there chinese clone rotaxes? tell us more please.
  6. Bruce Tuncks
    A prop that flexed so as to run finer for take-off and coarser for cruise would be great. As long as it was strong enough. Alas I am not clever enough to design one. But single-bladed props have been used on rubber-powered models. They did not have a mechanism to prevent ibob's shaking, and I still don't understand how you could do that. A 2 bladed prop also had an unbalance except when the inflow air is exactly perpendicular to the prop disc.
  7. Bruce Tuncks
    The answer to skippy's question has to be in the testing. As we know from postings here, that is a difficult thing to do. But if you do it properly, you will sure find out the best prop for you. Personally, I think it strange that we don't make our own props more. I would like to buy plans for the laminations and the data to give to a computer-router lot. Then I would buy the wood and cut out the laminations, glue them together and send them off to the router company. When they came back, I would sand and paint and balance the new prop. This should we way cheaper than buying and fun too. And you could try out different ideas like aspect ratio... ie fat or thin chord.
  8. Bruce Tuncks
    I would have called training or any other accident as KIA too so the rellies would be happy. I read that most aircrew killed north of Australia actually got lost first, and the Japanese had nothing to do with their deaths. It is easy to imagine doing a detour around a thunderstorm and then getting lost. They should have delayed the war till they all had a gps.
  9. Bruce Tuncks
    Some things bend more than others tho... apparently modern big-span gliders could not be made without carbon wings, because glass wings would twist and ruin the spanwise angle of attack and thus remove the big span advantage.
  10. Bruce Tuncks
    Yep, ice would be bad and sun is too. I reckon its a downside of fiberglass, that and the poor crushing strength. Not to mention the sanding dust killing you. A Jab shouldn't be kept outside, says me. It's bad enough at fly-ins, but that is not for too many days a year.
  11. Bruce Tuncks
    That poor little jabby! I dunno how fiberglass reacts to that cos I've never seen it before, but I sure would prefer to see it in a hangar.
  12. Bruce Tuncks
    During the war, they graduated 1,247 pilots and killed 45 students in accidents. They were flying tiger moths over flat country with generally good weather. Why so many fatalities? The odds of a student being killed were 28 to one. Contrast this to the Adelaide Soaring Club which has operated more than 50 years with zero fatalities , well zero at Gawler. Were those military instructors bad pilots or what?
  13. Bruce Tuncks
    Something I've wondered about gyros... What is the reason they seem to have a lot of accidents? They are advertised as being real safe. This is only for interest's sake... they are not the sort of "go places" flying I like, but their ability to land anywhere sure is impressive. There are none around here, so I don't know much about them.
  14. Bruce Tuncks
    I agree kgwilson. I knew this woman who worked for a drug rehabilitation lot and she said about half the clients thought you were stupid to pay for all that license stuff.
  15. Bruce Tuncks
    Aluminium alloy is such a good conductor of heat that there cannot be much of a temperature gradient through it. But Rf is right in that the inside will be hotter than the outside. And, radiant heat is small in comparison. You can calculate it quite accurately and see that a perfect black surface will radiate about one kilowatt per square meter at the sort of temperature reached. Nev said that radiation was not much and he was right.
  16. Bruce Tuncks
    I've run on avgas for 19 years. 100LL because that is what was in the bowser. It is only since the gen4 engines had problems with lead clogging that I thought to experiment. Maybe they have changed the avgas chemistry like Nev suspects. Yes my engine had deposits but they seemed to flake off and not increase over time. I would prefer it clean though. So far, it has about 4 hours on mogas and it runs just the same.
  17. Bruce Tuncks
    Thanks Kensla for the update. That's great news about the gen 4 leakdowns on mogas.
  18. Bruce Tuncks
    I would have thought that detonation was a problem more for high compression engines, by which I mean 10 to one. The Jabiru is 8.3 to one. I also reckon that hot spots could cause pre-ignition, which Mike Busch says is worse than detonation. SO... running an engine which is internally clean and is not overheating should be fine on high-octane mogas . Your car engine ( admittedly liquid cooled ) is higher compression and runs on lower octane, surely there is some margin there for the hotter air-cooled engine .
  19. Bruce Tuncks
    Sorry Rf guy, I have been at the farm since well before Xmas and I don't know much about the new gen 4 engine but I am happy with Kensla's report that it is running clean. My old engine ( 700 hours 2200A of 1998 vintage ) has just run a few hours on mogas and I hope it will look cleaner inside. Yenn is trying mogas too for the same reason. My engine has always had ok leakdown results, but not as good as jab 7252's which all went about 78/80 to my amazement.
  20. Bruce Tuncks
    Nev, you have just shown that Mike Busch was correct in saying that hours are not a good indicator of engine health. I was sufficiently worried about lead deposits that I have changed to 98 octane mogas too. It is too early but soon I will have a good look with an endoscope to see if the engine is cleaner. There used to be a coating ( about 1mm thick) of whitish lead looking stuff mixed up with carbon, and this coating flaked off and I guess went out the exhaust. On re-reading the Limbach cooling report, it stated that getting the cooling improved was urgent for mogas operations. The implication was that a mogas engine ran hotter, but I have seen no difference. Further, I don't see any reason why a mogas engine should run hotter. But those Limbach guys would know more than me I bet. Kensla, is the new gen 4 on 98 doing well?
  21. Bruce Tuncks
    The farm strip is at S 37 07 07 E 141 19 06
  22. Bruce Tuncks
    The 500m strip was really big enough for the Jabiru. Before landing on it, I measured the performance at Gawler and found that the Jabiru could clear a 50 ft obstacle in 350m. The trouble was really me. I had mainly flown from Gawler with an old WW2 bomber strip and cross-strip, and I was spoiled. The other problem was that the strip at the farm came in over the shearing shed. One day I thought the Jabiru wheels were missing the shearing shed by 2m and my daughter took a photo which showed that I was more like 40m higher. Even so, the Jabiru stopped well short of the upwind fence. The next thing was that the son got himself a Lancair. I told him he could fly the family Jab for nothing, but he said it was too little and too slow...So we built a hangar at the town strip and it just happened to be big enough for the Jabiru too. You can see the farm strip on google earth and the Edenhope town strip too.
  23. Bruce Tuncks
    I like Nev's point about the square cylinder fin-ends. It takes a fair bit of work with a fine dremel bit to improve them, so it is not something you could expect to be done at the factory. I only did a few fins on the hottest cylinder and it helped. Also, it does not increase complexity at all like a fan does.
  24. Bruce Tuncks
    Onetrack, I remember the old Volkswagen. I loved the sound of that fan. But I think it took quite a lot of power to run it. Mind you, applied to a Jab, it would only need to run at low speed.
  25. Bruce Tuncks
    Thanks kg, that was an interesting paper. More detailed than the Limbach one for sure. I was especially interested in the inlet losses through to the upper cowl being up to 50 % of dynamic pressure. Limbach say to streamline this entrance but do not have a figure. But the NASA article ( I reckon it was NACA when written ) still refers to plenum chambers which are different from the ram-air ducts that Jabirus use. A particular difference is that there can be cross-flow in a plenum chamber, so there can be no real difference left or right. This is not what I actually measured on my Jabiru.
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