Bruce Tuncks

These days, parts are laser-cut directly from computer files. Apparently Caterpillar make their heavy machines to order this way.

I read that the ships of yesterday used plywood templates made in the loft to cut the heavy steel bits. Due to dimension changes from humidity etc, they often had 50mm gaps to bodge up in the steep bits. This was especially bad if the steel was really thick like in a battleship. So onetrack's advice is good.

What do you reckon is the minimum strip length for a Jab, blueadventures? At the farm here, I made a 550 meter long strip which I landed on a few times, but I have been spoiled by the much longer strips at Gawler. My experiments showed that 300 m was long enough , but that allows nothing much for errors, and so I was scared of the 550m. I know of a strip which is 250 m, and I guess that this would do provided there was nothing higher than a farm fence at each end, and it was into the wind.

Correction... it is not that cheap at the moment to make methanol from hydrogen and CO2 but there are research places trying catalysts etc and hopefully this will change.

I reckon the future might have synthetic liquid fuels. For example, methanol ( CH3OH ) is what model planes used to use before being ousted by Li-Po batteries. If you have hydrogen, I think it relatively easy to make methane (CH4) and then methanol. I dunno if I agree with you kgwilson. Electric battery planes are cost-effective right now for some applications like training and gliders. A tenfold improvement would see battery power good for most of us who fly for an hour or two most of the time. And they sure displaced methanol model plane engines just on convenience grounds, with no incentives at all. I changed because the model plane stays clean and oil-free, and going model flying is much simpler. I do have several methanol models which are unused these days.

I thought Einstein was impressed by the fact that inertia and gravity cannot be separated out. Thus was born the idea of space-time and that gravity was the effect of warping space-time. If this were not so, you could imagine an instrument which was a perfect artificial horizon. BUT what about the Higgs boson, I wonder... " the particle which bestows mass". In my poor understanding, this runs counter to the space time stuff.

My opinion is that OME is wrong about the kilograms but right about the spirit level angle of attack thing. If you are travelling at constant speed at a constant height, then of course the spirit level will tell you the angle of the chord line if it is properly mounted. This angle will increase as you gently slow down. Until you stall. Whether or not this is a useful instrument in the real world is another matter. On my Jabiru, the stall warning horn thingy is an amazingly long way towards the underside of the leading edge, and the whole plane is correspondingly very nose up at the stall. I have never heard it sound on landing, and indeed the tail skid/fin would prevent the stall angle of attack unless the mains were about a metre above the ground. On a normal landing, the mains are closer to the ground but I don't feel the tail hit first. Should I? Anyway, I enjoy reading the stuff OME comes up with and I hope he continues.

best wishes James . I reckon you will have a lot of fun. At least to start, try for calm days for flying. Yes I know NZ is a windy place.

Back in the olden days when I used to teach this stuff for a living, the kg was a block of platinum held in a vault in Paris. The unit of force was the newton, which would accelerate a kg mass by 1 metre per second per second. The unit " kilogram weight" was frowned upon because it involved knowing just what the gravitational acceleration is. If you take this as 9.81 m/sec2. then AT THAT PLACE a kg-weight is 9.81 Newtons. There is an instrument called a gravimeter which measures this 9.81 variation very accurately and for example will help you find buried minerals. A geophysics mate of mine mapped out some ancient buried rivers in the outback using a gravimeter. ( deviations from the 9.81 are called " anomalies". Well its better than the old english system, where the unit of mass was the slug. One pound-force would accelerate a slug at one foot per sec2. All our engineering loads were in kips, that is kilo-pounds. What a mixture of metric and olde world the kip was huh. OME, you are sure right about the definition of the kg mass being incomprehensible to simple folk these days.

60 degrees is some bank angle for sure. Once I watched 2 awestruck at 2 big open-class gliders climbing in a narrow thermal core at about 60 degrees of bank. The wings were noticeably curved from the g loading. They were climbing well. 45 degrees seems very steep when you actually do it too. The diagonal instrument screws are parallel with the horizon. The g forces are noticeable too. I reckon few power pilots have ever done much of this. In a lightly-loaded 15m glider you need to do 45 degrees at 45 knots accurately and this is an impossible goal, but like a perfect golf shot, you need to just keep trying.

There is a lot of nonsense in the wine industry, and the one about quality is proportional to price is the biggest bit of nonsense ever written. Price is determined by how much you can get for it. There is a niche for real expensive stuff, bought by people who are trying to impress others. Here's the truth... wine made from good grapes with no stuff-ups by the winemaker will be good. In Australia, it is hard to buy local wine in bottles which is poor quality. The bottling etc is just too expensive to waste on bad wine, and also the winemaker will have his reputation to think of. Wine is just fermented grape juice after all. If you don't believe me, try doing a tasting where the drinkers only know a number and not the price.

At 90 degrees, the fuselage provides the lift. At 45 degrees, the wings would provide most of the lift but the fuse would be providing some. When you see a model flying in this mode, you sure see a high angle of attack for the fuse/wing. I am talking about a hesitation roll.

I like that story thruster. The wooden Jabiru prop is so simple and light that I would need some good figures to change for a CSU. For example, I would want about 5 knots more top speed. AND what if the extra loading by the prop caused less engine reliability? I have actually been worrying about this after changing from a 40" to a 44" prop on my Jabiru, I think it cruises a few knots faster and I don't notice any change on the take-off.

On my old Jabiru, the fuel gauge consists of a scale stuck to the outside of the translucent fuel tank. Accurate and reliable... BUT at low fuel, it is very hard to read. I have been thinking of arranging for a raised U tube ... one side connected to a tube which went from the top of the tank to the bottom. the other side to the top of the tank. To read it, you would use a squeeze bulb which pumped air into the long tank tube, until the U tube stabilized on account of blowing bubbles from the tank bottom. The stable reading would show exactly the level of fuel above the bottom of the long tube. This U tube could be anywhere you liked. I would love to hear any comments/criticisms. it is not often that I want to know the fuel left in the tank, but gosh sometimes you REALLY want to know. The other possibility is a sender stuck onto the outside of the tank which reads the prescence of liguid on the other side. You could have one at say 10 liters and another at 5 for example.

As well as the cost, my problem would be with the weight of the prop plus mechanism. But surely there would be an increase in the max speed, in comparison to a fixed pitch prop.

Hi Ian, 2 things: 1. I have no objection to getting your emails, so please add me to the list. 2. I have sold my Libelle, so please take the ad off. I don't know how to do this myself. I did find the "completed " button but it didn't seem to do much. Cheers, and thanks for the site. Bruce Tuncks

Yep, it is not that hard to make a duplicator yourself. There are some good examples on utube. That would be a good place to start I reckon. And while I agree that the prop makers are not really ripping me off, I am just a hopeless diy guy.

I have used what Jabiru have provided but I can't see why it is so hard to do one for yourself. Here's what I would like to see... A plan showing the laminations bandsawed and glued. Then you would send this off to a computer routing place, with the coordinate file. On getting it back , there would be sanding and finishing and balancing. What am i missing here? why no kit props?

Yeah! Thanks Jab 7252. I see that now, I never noticed it before. That sheepskin cover on the parachute is due for a visit to the washing machine I reckon.

I think the Blanik has lower wing loading than the libelle Nev. I dunno about the Kooka as they were before my time. There was a short and long winged Kooka, and the short wing one didn't thermal well, I have been told. I have read that the Me109 later versions had too high a wing loading and even with slats and flaps they were dangerous to land.

Completely correct Jab 7252. But I still understand what they mean by " low inertia" and "low kinetic" planes. I like the term "low wing loading " too. My Jabiru has the same wing loading as my Libelle, as they both have the same empty weight and very similar wing areas. It is actually a low wing loading for a glider these days which it why it outclimbs everything except for even lower wing-loading planes like the Pilatus. Gosh this maybe the last day I will be able to say " my Libelle" as the glider is for sale. It was the best-looking thing I have ever owned. And as for turning at low IAS, how about 45 degrees and 45 knots? You increase bank until diagonal instrument screws are parallel with the horizon then try and maintain 45 knots steady. Now this is more of an aim than what actually happens, just like a golf-shot where you are trying for a hole in one.

I don't know of a single plane left out in the sun here. A shed is not much more expensive than a refinish job I reckon. Maybe there are nasty regulations over there which make hangars so expensive that people go without?

Glass sure is a lot tougher than metal. But a glass plane really does need a hangar. Personally, I reckon metal aircraft need hangars too but I agree they fare better in the sun than glass does.

Wow pmc, your grandson is going to be a success in life I bet. I always wanted to be able to weld but never made it.

Here's what OME was getting at... If a 3kg mass is weighed where g=10m/sec2, there is 30 N. But Newtons are not for ordinary folk so the fish-scale you buy assumes 10N=1 kg weight-force and so it reads 3kg. Now you foolishly take your spring scale to the moon ( g=1.6m/sec2) and the 3kg mass now is 480 grams according to the scale. Therefore 3kg has become 480 grams. Of course it has not, the error was in the assumption built into the fish scales.