Bruce Tuncks

Is it possible to change the sealant in an old Jabiru tank? I imagine removing and drying the tank, then sloshing it with the new sealant. Is this enough? What if some rubber bits in the old Jab fuel system and carby are attacked by ethanol?

The pprune guy was a bit sad. Nev has it right. We have more fun than they do and so what else matters? I am reminded of the story of this top-gun guy who bought a glider and entered the US nationals. On signing in, he asked what handicap he would have to carry , since he was clearly a better pilot than the rest. After some days, he dropped out, never to be heard of again. He was running last at the time. Now I thought this a sad story, he was probably a good pilot in jets. Seafarers don't seem to make this mistake, you don't hear of a liner captain thinking he would win a surfing competition.

Yep, that,s why I wondered about the DV111. In the Blue Max film, the end was where he crashed in the very latest fighter and it looked like a DV111

I think I read that the Fokker DV111 was the best WW1 plane. Was this so?

I reckon they have a better govt regulation setup there... maybe our lot have too much money and power.

Yenn,I reckon it is impossible to fault-find an intermittent while things are working. You are trying to find a fault where none exists. Jbiru had problems I know with the tacho sender. Mine triggers off a low-tension pulse, and it works but when I tried it on another plane, it would not go to 3000 rpm, Can you borrow another meter to try out?

Onetrack, do you mean to say that the article in the latest online kitplanes email mag was actually from years ago? And they let me think it was just written?

We shouldn't condemn her for being a woman with no aviation experience, but alas the omens are not good that she will understand that safety does not have to mean nasty prohibitions.

yep, the great thing about maintenance, as opposed to flying, is that you are not pressed for time and you can ponder and seek advice all day.

The only lame I actually know is quite slow. I'm sure that there are smart ones out there, and I have met some of these, but all their experience was Lycomings or Continentals, put into standard GA planes like Cessnas. They were out of their depths on some non-standard ( by Cessna standards ) parts of the son's Lancair. ( The retract hydraulics are marine stuff on the Lancair) I have never even heard of a lame who gets to the bottom of things like rfguy and facthunter. These guys are quite professional . The lames also suffer from the " get it out the door" urgency which you probably need to make money these days, and so they do not have the time to think things through so well. I don't want to be seen as denigrating lames, in another life I could have been one.

I reckon you should have more clearance( with no oil in the lifters) . I understand Nev's point about the pushrod coming loose, but I would think that you should be able to use at least 1mm of movement before this happened. If you don't do this, you are effectively saying that you think the hydraulic lifters are too unreliable to cope with.

RF guy, don't you need to shorten the pushrods by 1.5mm so as to put them halfway through the 3mm adjustment of the hydraulic lifters?

Interesting, but the main thing I have got is to be grateful for the old solid lifters in my engine. Sure they need checking, but the need for an adjustment tells you stuff. Can you chuck out the hydraulic ones? My guess is that other things were changed to suit the hydraulic lifters and this would be a risky thing to do.

Gosh it’s harder than I thought. I think jab props were made out of hoop pine. it makes sense to me that wood is easier on the rest of the engine , and so a small loss of efficiency is a small price to pay for more reliability. If you cover a wood prop with glass, surely this adds to the strength?

Very interesting RF that not all older jabs do the tight turnover thing when hot. Around here they all seem to do it, and it was very noticeable that the gen 4 didn't. I really liked how the gen 4 felt bouncy even when hot. The thought that it could be just one piston has never occurred to me, thanks for the idea. How could I test that out?

In Spacy's defence , I noticed that Russian trainers used wooden props because they protected the crankshaft in the event of a prop strike. But maybe those Russians just had a relaxed attitude about trainees dying.

The existing Jabiru prop is made from a type of pine ( not radiata) with quite a thick fibreglass covering. In fact. the fiberglass covering is so thick that it may have been done in a mould. Does anybody know just how these props are ( were) made? I like the idea of the Tasmanian mountain ash, especially if it is lighter. About being too thin... the loads are quite calculable and so the prop should be able to be tested by proofloading I reckon. Has anybody done this? Apart from spacy, but I have to say that markdun seems more right about a deliberate prop-strike not being the best idea. I have in mind clamping the prop hub in a vice and pulling forward on a prop tip with a spring balance.

Sorry old k, I tried but don't think it will work properly. I am a subscriber and that is why I get the stuff. So here's a brief summary... the topics were: oil cooling; CHT's and their tweaking for lowering and evening, taildraggers and dipstick adjustment;bing carby's , cylinder heads; better exhaust systems. Most of the stuff has been discussed here, although not the use of the sonerai exhaust setup. The only problem with the article was that it was specific to the older engines, those with the machined heads like mine and not like the gen 4.

Making Peace with the Jabiru Engine

Not off topic, but a change... I really liked the Jabiru engine article in the latest online Kitplanes.The article did not seek to hide issues but dealt with them well I thought

The Jabiru gauge is just screwed onto the engine block, and it suffers from vibration as a result. But it is not going to cause the engine to die from a burst or leaking hose. And if the engine is running well and the other gauges ( especially oil temp ) are normal, then the gauge is faulty and you continue flying. I understand why Jabiru decided to do it this way, just as I understand why the pressure gauge manufacturer wanting a bit of rubber hose between the block and the sender.

A very interesting discussion rf and facthunter. Thanks. Here's my guesses... My old 700 hour engine runs fine but the stiffening up is so marked when you hand-turn it hot that I think this cannot be happening when running or the engine would seize. Could it be that some internal heat-soaking is taking place after the engine stops? When taxying to the hangar after a flight, the cylinder head temps are all about 130C. I understand that an aluminium piston in a steel cylinder would tighten up on heating, actually your calculations rf show this to be less than I thought. But that heating pic of the piston shows a big amount of post-shutdown heat movement from the piston top will happen.

Quite often, we get stuff about how the airship will have a resurgence but it doesn't seem to happen.

I have read that the hydrogen gas has been given an unfair amount of the blame and that it was the nitrate-doped linen which was the worst culprit. Nitro-cellulose is an explosive, and nitrate-doped linen is pretty close to this.

Quite right Nev. As a kid, I had 240 volt shocks but never a bad one. For example, if you are touching the active wire (240 times root2 max volts ) but your hand is dry and you have sneakers on ( rubber soles) then you have a very high resistance path for the volts and while you will feel the jolt, it will not hurt you. On the other hand, if you were touching a ground with the other hand and your hands were wet, at least a thousand times more current will flow through you. Our 240 volt system is in my opinion better than the american 110 volts as our losses are less. But yes it can be more lethal. Play with an ohm-meter and you will see what I mean. The skin, if dry, is the major point of resistance. Inside, we are exactly as saline as the ocean from whence our ancestors came, and this is very little resistance.