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rgmwa

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Everything posted by rgmwa

  1. rgmwa
    That definitely helps!
  2. rgmwa
    Just out of interest, these are the various wind speed regions for Australia: If you're in coastal Northern Qld, you'll be in Region C (cyclonic). The number after the letters (eg A0-A5) denotes different wind speeds coming from different directions for each region, and can be used to fine tune a design. The typical basic design wind speeds in each region are: A 45m/sec (162 km/hr) B 57m/sec (205 km/hr) C 66m/sec (238 km/hr) D 80m/sec (288 km/hr)
  3. rgmwa
    Maybe, but then they would more likely have said travel speed, not wind speed. Here's the reference: Abstract An extensive census and sampling program conducted in semiarid north-west New South Wales, Australia, has provided quantitative information on willy-willy (dust devils) characteristics and their environmental range. The observation of 557 willy-willies, made over a 20 day census period in summer, indicates that willy-willy frequency varies according to local meteorological conditions. An air temperature lapse rate, measured between 12 and 252 cm of the surface, of 0.9 °C m−1 was required for the initiation of the willy-willies, with their frequency increasing with lapse rate away from the surface. Willy-willies were also found to be restricted to wind speeds between 1.5 and 7.5 m s−1. Analysis of the spatial distribution of willy-willy initiation sites with respect to vegetation cover in the 35 km2 study area showed that willy–willy frequency increases with decreasing surface cover. The increased frequency of willy-willies with decreasing vegetation, could, over time, make willy-willies a potent mechanism in the evolution of the Australian landscape.
  4. rgmwa
    Correct. That's why engineering firms carry Professional Indemnity Insurance. A study of willy-willies in NSW (557 willy willies sampled over 20 days) found they had wind speeds between 1.5m/sec and 7.5m/sec or (5km/hr to 27 km/hr). Seems a bit low to me, but that's what they said.
  5. rgmwa
    No they can't, unless you bought a kit designed for Victoria or Tasmania and decided to put in on your block in Port Hedland.
  6. rgmwa
    They do have some tension rod diagonal bracing in the roof and may also have it in the end bay side walls. They have also braced the unsupported rafter and column flanges back to the purlins and girts to resist buckling. I don't like the look of the portal connections much, but they may be OK. Other cold-formed structures I've seen used back to back C-sections bolted together with central gusset plates and spacers, and used bolts instead of Tek screws, but there are many ways to skin a cat. Cold formed structure design is pretty specialised and the design calculations can become very complex because the components are so thin and secondary effects such as small eccentricities in the structure become very important. It's pretty tedious and long-winded to do it by hand and you really need computer software written by experts, but then of course, it can be a case of garbage in, garbage out.
  7. rgmwa
    Yes, it does have a gap and that helps to relieve some of the pressure. Basically, if the area of the opening/s allowing the wind in is greater than the sum of the areas of all the openings letting the wind out, the pressure will build up. If it's the other way around, you get a net suction effect. The effect of openings in the roof and walls in a building is taken into account in the design, for whichever direction the wind is blowing.
  8. rgmwa
    I'm not aware of any failing. Our firm has been involved in a few and it's definitely something we consider and make sure there's enough weight in them, or some other form of anchorage to make sure the containers stay where they are, even if the fabric potentially gives way first. As I suggested before, lots of poorly built or under-strength structures never fail because they never experience their full design loads. The basic design wind speed for a normal building in Cue, for example, is 162 km/hr. Various factors based on the building's shape, the surrounding terrain, the part of the building being designed etc are then applied to convert that wind speed to a design wind pressure. In a cyclonic area such as Karratha, the pressure of the wind on a steel framed building can be roughly equivalent to the weight (acting upwards on the roof) of about 200mm of concrete and the same on the walls trying pushing the building over.
  9. rgmwa
    Unless the container setup has been designed to have one end enclosed, you might find it will not stand up to strong winds. The air gets trapped in one direction and the positive pressure significantly increases the total uplift on the roof. When the wind blows in the opposite or sideways directions, the internal pressure drops increasing the negative pressure wanting to pull it down, although that's usually less of a problem than the uplift. Portal rafters can buckle under wind uplift whether they are made of trusses, I-beams or pressed metal lipped sections unless the bottom flanges or chords are braced back to the purlins at certain locations. Same with the columns. These sheds should also have wall and roof bracing and not rely on the sheeting to do the work. While Increasing the truss span from 4.8m to 8m doesn't seem like a lot, it can increase the stresses in the trusses and columns by a factor of about 2.5 to 3 for the same loading, all things being equal. On the other hand most structures rarely if ever experience their full design loads. I have a hangar made from second hand materials that has stood up quite happily for more than 20 years that I probably couldn't prove would stand up under the wind loads loads it should be designed for. So far, so good.
  10. rgmwa
    Impressive! How fast could you spin it?
  11. rgmwa
    Head of Flight Operations.
  12. rgmwa
    How's your training going?
  13. rgmwa
    I saw that once. I was the lucky passenger sitting in the copilot's seat on a King Air flying back to Perth from Shark Bay on a stormy day after last light. Green lightning dancing around the cockpit windows. It was fascinating to see.
  14. rgmwa

    Aviation Terms

    rgmwa commented on Admin's resource in Reference Items

    Wasn't it originally DED for `deduced' reckoning? I suppose you could end up DEAD if you got it wrong, so maybe there's some sense in that too.
  15. rgmwa
    There could be a commercial aspect to carrying cargo that wouldn’t be allowed as a private pilot (saving freight costs for the recipient, for example). I don’t think there would be an issue ferrying the plane as long as there was no payment or other form of recompense involved. It’s not a class 2 issue. It’s a pilot license issue.
  16. rgmwa
    That’s the big test. The rest is just paperwork.
  17. rgmwa
    As Red said, the clamp is not necessary on the Rotax but does no harm. I've never used one. I mark mine with a bit of torque seal and it's never moved.
  18. rgmwa
    I flew from Warrnambool to Melbourne in one in the mid 1960's. Ansett, I think. It was an experience walking uphill to my seat and being able to see right into the cockpit and watch the pilots at work. Lots of noise.
  19. rgmwa
    Sounds like a good choice for engineering support judging by her website.
  20. rgmwa
    Where do you live? Just want to make sure I don’t take a wrong turn by mistake.
  21. rgmwa
    Wrong again Skippy. No prior expectations and no bias reinforcement. I knew he was on his way back from Rottnest because he was talking to ATC and asking for traffic info around Fremantle which I was approaching in a 172, I saw his lights in the far distance and assumed they were attached to his aircraft which was much less easy to see until he got a fair bit closer. Anyway, have it your way. I'm getting a bit tired of this pot-stirring back and forth and I suspect others are too. People can make up their own mind about lights. I happen to think they can be useful at times. Even without that little episode, I would have put them on my plane anyway just because I like them. The extra switches on the panel look nice too.
  22. rgmwa
    Skippy i think anyone reading this thread will understand perfectly well that lights may help in certain circumstances but they are not required for day VFR, and should not be relied on to keep you safe. The example I gave was a one-off case where lights made a difference to visibility. That’s all. As you have already pointed out good radio communication and a good lookout are a lot more important.
  23. rgmwa
    Please yourself about your position. My rationale works for me. You seem to want to fit lights mainly because they look nice. I suppose that’s a good reason. To answer your question, we were both VFR. Last light about 6:30. Some cloud around to the west.
  24. rgmwa
    Sure, I agree. I knew roughly where to look, but how many times do you hear pilots say ‘looking for traffic’ when ATC or another pilot tells them where to look. Looking and seeing are two different things. I saw him because he had his wingtip strobes on and he was against a fairly dark land/sea background at around 5:00 pm. I have no doubt I would have seen him sooner or later without the strobes but he would have been a lot closer. He was also approaching more or less at right angles so not much relative movement against the background that would have made him easier to spot. It showed me the value of lights in certain circumstances. Good enough for me.
  25. rgmwa
    I was flying back to Jandakot south along the coast in the late afternoon some years ago and knew from his radio calls that a Mooney was approaching from my right at the same height on his was back from Rottnest Island. I saw his strobes much more quickly than I would have been able to see him otherwise at that time of day with the sun getting lower in the sky. I was easily able to avoid him but decided then that if I ever built a plane, I was going to have lights on it. I agree that most of the time you don't need them but if it prevents an accident or a near miss just once in your flying career, I'd say it's money well spent.
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