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Bruce Tuncks

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Bruce Tuncks last won the day on October 9 2019

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About Bruce Tuncks

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    Well-known member
  • Birthday 08/08/1945

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  • Aircraft
    jabiru sk
  • Location
    Gawler, South Australia
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  1. I would be happy to pay $100 a year for the site to continue as is. Compared with other costs of flying, that would be really good value for money. But would I have ever started out here if there were an up-front fee? For myself, a honeymoon first year might have done the trick. Advertising is fine too as long as it doesn't consist of intrusive pop-up things. Good luck Ian.
  2. I agree skippy. The more powerful you make a program then the more commands it has to have and the harder it is to make it work. If they would only make a stripped-down simple version then I would opt for it. Unfortunately, the programming people live with the thing and forget about how things have got hard to operate. There is a phone company who advertises a mobile phone with no bells and whistles, all it does is be a phone... a good idea, says me.
  3. Was there still a full load of water on board? If so, that would exacerbate the gust loadings which may have come close to or exceeded the design loadings. I can imagine some dreadful sharp-edged upgusts what with the mountains plus the wind plus the fires. Such a sad end to a wonderful endeavor, what with the aircraft and organizations and crew.
  4. I like your attitude NT, but personally I don't feel guilty about the Jabiru. It uses about the same petrol per mile as a car and there are a great many useless miles driven in cars every day. Some commuters go over 100km. Now I am retired, I would move so that somebody else could commute less but there are serious financial disincentives stopping this happening. They could be fixed by the government. My responsibility is to vote for the proper policies and this would be more effective than doing my own thing. There is a lot the government could and should be doing, such as the commuting business and taxing carbon and subsidizing non-carbon energy. As regards gliding, well when I bought my Jabiru kit, it was cheaper than the SALES TAX on the glider I had been thinking of. Yes, the government had it wrong but you can't fight against the government except on election day.
  5. what diameter of blast tube jetjr? and rigid or flexible? Coming from the existing duct or from another opening? I don't have any blast tubes at all, but I have put in shields to intercept radiant heat from getting to the coils.
  6. Thanks guys, I should have checked more 30 years ago, but better late than never I guess. I reckon those engines like the Merlin were over 1000 hp, so that Caterpillar engine at 225 hp would have been a bit small maybe. But it is a bit surprising that diesels were not used for tanks, you would think that they were a better option than petrol, especially with the extra risk of petrol with respect to refuelling fires.
  7. Good point Old K. Yep, I have used LHS as if looking from the front. I should have used port and starboard. What I have called the LHS is actually the starboard side. Sorry if I confused anybody. Actually, this cooling business is confusing enough without any help from me.
  8. There was a big Steiger tractor where I used to work and it had ( so I was told ) the same engine as the main 1960's American battle-tank. In the tractor, the engine was rated at 225 hp and had a TBO of 10,000 hours. Caterpillar manufacture I think. In the tank, there was an emergency over-ride and the rated power was nearly 1000 hp with a rated life of 10 minutes. I never saw any documentation on this, but I repeated the story because I liked the moral of treating machinery gently if you wanted it to last. Maybe somebody here knows more.
  9. A few days ago I ruined a good LiFePO4 battery. This battery was about 3 years old and originally bought as one of a pair to start the Jabiru. Well the Jabiru only needed one battery, so this one was a spare and was used for the glider radio and an electric chainsaw. It was in good condition until... I had just used the chainsaw and decided to give the battery a quick recharge before going to the club to fly the glider. I used the wrong setting on the charger ( the Nicad setting ) and overcharged the battery badly ( 20 volts instead of 14.4) . The cells puffed up and burst out of the plastic cover. Bugger, those batteries have increased in price since 3 years ago, this has cost me about $150.
  10. Yesterday ( ambient 27 degrees ) the temperatures were more equal than ever before, much to my surprise. All I did was to remove the tape which had been sealing off the inch-sized hole in the LHS duct ( the higher-pressure one ) and the subsequent flight showed temperatures amazingly even. T1=143, T2=141, T3=143, T4=140. This reinforced the idea that air-cooling is indeed a black art. I have no good ideas as to why this happened or if it will repeat itself, but of course I hope it will stay like this. I was, as usual, climbing carefully at 80 knots and could have got higher temperatures by trying. Looking into the intake of the LHS, you can see the vacuum cleaner hose which goes to the RHS, and adjacent to the vacuum cleaner hose is the hole which is now uncovered. You can also see the small deflector which partially shields no 1 cylinder from cooling air.
  11. That's not my experience with my early Jabiru engine. 1998 model, but I have replaced the 2 rear heads on account of how the old ones didn't have enough cooling fins. The front heads are original. Never had a problem in the air and about 700 hours now. That would be about 100 trips to Alice Springs from here. Once I asked the factory why my engine was left out of the AD's and was told that it was because they had no problems with engines like mine. It has all the small bolts they have upsized . Maybe the small carby ( 32mm ) protects things? Maybe the epoxy which prevents any prop hammering? Maybe the frequent ( 25 hour ) oil changes? Maybe taking care with the max temps? In about 200 hours, I intend to swap it for a new gen4 engine.
  12. You are right to complain Marty. What I would do though is to run a tap through them and then use a bit of weak loctite on the bolts. The only purpose of the system is to stop vibration-loosening and this will not happen without an off-torque and even if an off-torque was present, the loctite would stop any loosening. That tapered metal-interference tightening idea predated loctite I reckon, and it is geometrically so tricky that your problem is not hard to imagine.
  13. Jaba-who, do you have the option of NOT insuring ? Some risks are so unlikely that I reckon you should carry the risk yourself. For example, why insure against being abducted by aliens? There are 2 categories where is makes little sense to insure: Firstly, where you can afford to carry the risk yourself, and secondly, where the event is so unlikely that it has never happened except in the imaginings of insecure people.
  14. All wings ( and a propeller is a rotating wing) are laminar flow at the start. The so-called laminar flow airfoils are designed to have more laminar flow than the others. As Facthunter alludes to, laminar flow has the bad characteristic of separating from the surface and making the drag worse than ever. So some airfoils work with turbulators which deliberately trip the laminar flow into turbulent flow. If you put on the turbulator too far forward, you give away a bit of low-drag area and if you put it too far back, into the separated flow part, then it does nothing. You can refer to experts and get conflicting opinions, or you can do a lot of expensive testing. Once, when I was young and silly, I tried to find if turbulators could improve a Mosquito flapped glider. The test-rig consisted of an under-wing set of pitots sited at the trailing edge and connected to an ASI via a plenum chamber. The theory is that the lower the airspeed measured by this "wake rake" then the higher the drag. Then each flight, you can try a new turbulator stuck on in front of the wake rake. I never found any worthwhile improvement and most of the time the turbulator made things worse. Now that I'm old and silly, I am wondering about turbulating a Libelle.
  15. The boundary layer at the leading edge is very thin and a tiny protrusion can trip the laminar flow into turbulent flow. The turbulent flow spreads and it makes those tracks. There is quite an effect on performance, since turbulent flow is about ten times the drag of laminar flow.
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