Jump to content

Old Koreelah

Moderators
 View Profile  See their activity

  • Posts

    6,237

  • Joined

  • Last visited

  • Days Won

    55

 Content Type 

Everything posted by Old Koreelah

  1. Old Koreelah
    Lots of crashed Jabs have been repaired and are back flying. Metal aircraft may cope better than composites with being parked outside, but a prag is often curtains for them. I was shown a small section of a Savanna, the only bit that wasn’t bent by a simple prang.
  2. Old Koreelah
    Some recommend warming up a Jab at 1000rpm. Nev do you know at what minimum revs a Jab oil pump works properly?
  3. Old Koreelah
    Skip I used Vinyl Ester (Derakane) for several heat-affected jobs after consulting a chemical engineer retained by my material supplier, FibreGlass International. Can’t remember the figures, but he assured me it was very tolerant of heat, as well as fuels and ethanol. Might be worth asking your supplier.
  4. Old Koreelah
    With ASI, the slip ball is the most important gauge; my 15 year old daughter made my hi-tech version and it’s likely to last decades. My panel is plywood stained to match the wooden handles (cut from an ancient rosewood log by my dad in the 60s). It may not be the neatest, but I find it ergonomic. Last week I climbed into my cockpit to do an installation job and it was so familiar and comfortable I almost went to sleep.
  5. Old Koreelah
    Skip has anyone mentioned heat tolerance of resin type? Most common epoxies go soft above 60C and after shutdown the cowl above a hot engine cops lots of heat. After a dozen years of regular “cooking”, my cowl still seems very strong. Maybe the epoxy has become “heat treated”. Maybe it survived because Inadding a couple of layers with Vinyl Ester resin, which can tolerate much higher temperatures that other resins.
  6. Old Koreelah
    The three common reinforcing fibres have quite different properties. Glass fibres are easy to wet out, making it ideal for hand laminating. Glass will stretch a little, giving useful flexiblity. Kevlar is a bugger to cut and wet out, has lots of give when stressed, but will return to original shape, making it ideal for crash-prone components. The strongest is Carbon, but it’s plurry hard to properly saturate (unless you use vacuum bagging). Carbon is very stiff, but when it breaks, you are left with dangerous micrfibres. Jabiru are wise to stick with glass fibre; it suits the job and it easy to repair.
  7. Old Koreelah
    Working solo it’s easy to overlook minor blemishes. The quality of my current laminating job is better than some past ones; this time my wife has played a blinder with the roller.
  8. Old Koreelah
    When materials and machines are made to standard, it’s in the nature of some people to push the limits, in the belief that there is a large “fudge factor” to protect you.
  9. Old Koreelah
    That’s why I mounted my water tank in the lowest place available, after discovering it would syphon, even thru the tiny spray orifice. One of club members is from your part of the continent and he tells me the combustion chambers of his Ford were shiny after a few hundred thousand km with a manifold-mounted “steam injection” system.
  10. Old Koreelah
    Good point Bruce. The first version delivered a water/fuel ratio of about 1:5 and didn’t cool the heads as much as I’d like. Anticipating very hot weather, I set the second one to a ratio of about 1:2 and it does an excellent job, but I hadn’t considered the shock cooling risk. As outlined in my previous post, I plan to relocate the nozzle to downstream of the carby and come up with some way of gradually “ramping up” the water rate with revs, in order to reduce shock cooling. I’d also like to find a better position for the water tank, so it doesn’t reduce legroom. Making these modifications was pretty easy when my plane lived on it’s carrier in my shed but now it means a trip to the airport and lots of standing on my head to reach under the panel.
  11. Old Koreelah
    Turb’s reservations got me thinking. I’ve spent lots of time installing cowl flaps to avoid shock cooling, but hadn’t considered the sudden cooling by water. Worse, my new water injector sprays almost four times as much water as the old one; after a few seconds on full throttle the CHTs all drop quickly. Adjusting that rate is a tedious job. As I mentioned earlier, I have a disused oil injector in the rubber coupling downstream of the carby, so I could relocate my water injector to that location. That would make it safer and more accessible for fine adjustments. It occurs to me that the ideal spray rate starts small and increases with revs; Maybe link the throttle lever to a reostat to vary the power of the pump. Or link the throttle to a constrictor valve Why not have it controlled by the intake vacuum… That means a second carby! Not gonna happen.
  12. Old Koreelah
    Yep. Half the people I meet are either already on the road, or planning to be. Suffering from a tight budget, we postponed roaming till Boomers started giving up their campers. Covid torpedoed that, so I’m building one. Looking forward to test runs in a couple of months. Not looking forward to packed campgrounds.
  13. Old Koreelah
    Hope you are right, Nev. I always gradually advance the throttle lever over about five seconds. All my approaches are glides at idle and I make a habit of closing cowl flaps to about 1/4 when backing off in the circuit. Despite this, by the time I cross the keys the heads are down around 100C. That’s exactly where it goes Nev; remember that earlier in this discussion you suggested that. Since the water only pumps at full throttle, it should go straight thru to the combustuon chamber. I’ve mounted the reservior below the level of the spray nossle to prevent syphoning when the pump is not running.
  14. Old Koreelah
    Hope you are right, Nev. I always gradually advance the throttle lever over about five seconds. All my approaches are glides at idle and I make a habit of closing cowl flaps to about 1/4 when backing off in the circuit. Despite this, by the time I cross the keys the heads are down around 100C.
  15. Old Koreelah
    Hours flown during 2020= 6.4 Hours flown during 2021= 20.5 Trips away = nil for two years Local area is becoming quite familiar.
  16. Old Koreelah
    And a good thing too; I only carry enough water for 6 minutes at full power-enough for three 1000’ climbs.
  17. Old Koreelah
    That has my attention. There is a time lag of about ten seconds between hitting full power and the CHTs starting to climb. I presume that’s how long it takes for the heat to travel from a few mm from the combustion chamber to the probes Perhaps the ideal is to gradually ramp up cooling water and taper it off after backing of the power. How to do that without over complicating the setup? I mucked up my maths; the current water rate of 200ml/minute is about 50% of the amount of fuel it burns at WOT.
  18. Old Koreelah
    During the week I installed a more powerful water injector system (a windscreen washer kit- thanks Cosmicray) and this morning I tried it out, first with the plane tethered to a post- in case the extra water puts out the fire. With the output set to 200ml per minute, it’s spraying at least as much water into the engine as fuel- a 50/50 mix. Previous test flights with c.80ml/min only cooled the CHTs a few degrees; this time the air intake temp probe (which cops the water spray) dropped almost ten degrees and the CHTs quickly cooled to an average of 130C! The pump only operates at full throttle, so as soon as I back off the power, the heads heat up considerably.
  19. Old Koreelah
    Skip you have a wonderful opportunity to use the exhaust to enhance cooling. Many Cessnas, etc. have the pipes in the middle of the cooling air exit, intoducing some exhaust augmentor effect. I’m sure this works, because their huge engines are effectively cooled with a tiny exit no larger than the one my little 2.2 litre engine uses.
  20. Old Koreelah
    Skip I’m not much use, but it would depend on the geometry of your engine mounts; the closer they are together, the more you’d expect the engine to move on it’s rubber mounts. My 4 cyl Jab moves most on startup and shutdown, but I cannot see any wear marks on the cowl, which is a pretty tight fit (I covered the engine in glad wrap then used klegecell to build up the cowl over that). A good fit helps with controlling airflow but I wish I’d allowed a bit more space for bits I added later.
  21. Old Koreelah
    …and with taildraggers, the aircraft at flying attitude.
  22. Old Koreelah
    …which means most of us will never get to use 5G phones.
  23. Old Koreelah
    To get a more accurate reading, I articulated my pitot. A flexible tube had a small A-frame empenage to keep it pointing into the airflow during side slips and at high AoA. Worked okey, but the flimsy wood eventually broke and was removed.
  24. Old Koreelah
    We all have an opinion, but will those in power take any notice? Yes, I’d like a SkyEcho and would pay the full price if I knew it would keep the regulators happy.
  25. Old Koreelah
    Good point, but some of us have a very tight budget. Agreed, but who will invest precious $ and installation time without a cast-iron guarantee that our new gear won’t be made obsolete next year?
×
×
  • Create New...