RFguy

10lph average sounds a bit low for a ol tecnam. well what do we have, TO roll, climb to 1000' in favourable condix , total 90 seconds at 27 lph. = 675mL probably low cruise 65% for 120 second at 15lph = 0.5L base, final average 30% for 150 seconds maybe 8 lph =333mL total time 360 seconds, total fuel 1.508L. equates to 15.08lph well that's my guess, anyway .

as expected, slab cost turnkey, with >6" of coarse fill + buildup, 6" slab n piers, thick at edges etc etc etc etc $120/sqM finished.

so its mostly descending.....

Indeed. suck limit is -4.5psi IIRC.

I dont think we can compare rich and lean mixtures because power output is different for different mixtures - we really need to compare apples for apples- IE 100% or 75% power. theroretical thermal efficiency : 7:1 (O-200) : 54.1% 8.0 (Jabiru most -depends on head recession ) 56.4 8.5 (Beech 23 with Lyco) 57.5 rotax 912ULS 61.4% real life differences will be about half to three-fifths of that so Bob, your original statement of lower fuel costs with the rotax are probably true.

ahh Bob I have found the difference in the O200 and the rotax in the thermal efficiency numbers see above.... so it is likely the rotax really is better, even if the gain is only half that just on thermal efficiency gain of 13% due to higher compression ratio.

What is the compression ratio of that particular O-320 Thruster ? cant really compare 100% on rotax (full rich) to 65% on beech (Not full rich)

For the ideal otto cycle engine , thermal efficiency = 1-( 1 / (c^(1.4 -1) )). for 7:1 = 54.1% for 10.8:1 = 61.4% IE 1.13x better ! so in theory, maybe 22 litres>>19.37., Hmmm not far from the rotax numbers ! But in practice, real outcomes are less. engines have different cooling, oiling etc shaft input costs, temperatures the CC runs at, RPM, friction etc. https://www.primescholars.com/articles/influence-of-compression-ratio-on-the-performance-characteristics-of-a-sparkignition-engine.pdf

now, nit picking : While the O-200 can go lean of peak, the Rotax 912ULS runs at 10.8:1 compression- higher efficiency . The O200 at 7:1 compression. Yes, taking into account the higher compression ratio, MUCH higher, indeed the rotax shoudl do MUCH better than the O-200. But not all things are equal, losses, friction, heat etc all very different engines....

specific fuel consumption kg/kW/h is going to be the same, I would think.

Not sure about the fuel saving calcs. fuel is fuel. I would think because the O200 is a bit happier at lean of peak, the O200 might be lower fuel cost, apples for apples ULP. weight advantage would depend on the aircraft.

Bob, I read through that thread, I would agree a problem for Rotax is the lack of suitably familiar mechanics. and parts are priced to deter rebuilds IMO. They are a little fussy and complex compared to an O200 but that's what you get for the advantages of - weighing 30% less and not ever having to worry about engine temps, and not have a bulk strip if you have a prop strike....and most will go to TBO with just a gearbox overhaul to 1k hours. (ULP) I think Mark's rotax throttle linkage solves the multi throttle cable problem with a nice hammer..

I am seeing around $300/cuM for 32MPa in country NSW.

How much is price in your neck of the woods for 32 MPa concrete /cuM with a batching plant local ?

The concrete on site pour and tilt up is competitive with the steel- (after the steel prices went up). I think there is 15 tons of steel in my steel hangar build proposal . plus roller doors, PA doors, insulation blankets, door hardware. The concrete wins on the labour on big sheds where the steel assembly labour is significant. The concrete is nice for insulation- to a point- hangars are not well sealed as they spend a bit of time with the doors open. The concrete walls , will go to the mean daily temp , most likely. This the concrete actually needs a insulation layer on the outside - that's the best construction for thermal control- just like dumb Brick veneer homes away from the coast - they have the bricks on the wrong side of the wall for thermal control- needs bricks on the inside..... where as the steel building the temp will go up and down like a yoyo, well not so much the slab does a fairly good job of limiting the peak to peak. so add more thermal mass in the form of concrete walls the peak to peak narrows . so at cowra, the tilt up concrete probably goes to about june-july-august about 9 deg C , and peak summer probably a comfortable 24C . The steel though can have a few windows easily popped in for the mezzanine n etc and other areas as things change. certainly they can be poured with the gaps in the tilt up, more complex though.

The rotax is pretty forgiving of misalignment of ... everything... at cruise and WOT settings. It does not however, like idle settings. the inlet manifold is suboptimal, the gearbox doesnt like it. However, that's hardly an operational disadvantage to all the other fine attributes of the engine. I'd suggest warm up oil cooler bypass and water cooler bypass, to limit the warm up idle time where the engine is unhappy. Or a sheet of cardboard..... On warm up, I idle the club rotax at the top end of the rotax permitted warmup RPM , and use a sheet of cardboard on both coolers.

Is the Bristell a CS / IFA prop ?

Unfortunately the council didnt plan the blocks for T hangars , either. ANyway, now can consider the merits of concrete tilt up versus steel.

No, we probably wont read about it and that is the downside of the RA framework. There's plenty of upsides, just depends on how you rate them. I would think, for a rotax, there would be very few combinations that would be problematic, it has a high range of acceptance of MMOI. The prop is well isolated from the torque pulses . However, props in RA are a bit of wild west - not perceived as a significant modification by many . Certainly in any direct drive engine like the Jabiru, that's very much a symbiotic relationship between prop, engine and flywheel. So I am putting this down to a maintenance issue , overspeed , or material failure. (ha! ) . ALthough I dont even know if it lost prop on landing nor before?

I am 2nd on the new 'taxiway'.. club is next door, Trevor is on my right .

At Cowra, there are several hangars new hangars being built , one large one being built right now (I know because I see the DAs , as an adjacent land owner) . there might be a bit of room shortly.

alright you two. stop it.

SKippy what you nned to be concerned with the exit cowl air , is the exit air exiting TOO SLOW. Energy will be required to accelerate cowling exit air up to the flying airspeed, and with the Vsquared parameter in there, it will hurt. So, ensure your cowling exits are not TOO broad/large than optimal . Too large and the velocity (for a given airflow) will be too slow, and that will be drag because the slow cowling exit air needs to be accelerated. Too small - that will reduce airflow/ limit pressure difference between frontal pressure and inside cowl (which is required for cooling to work ) , but may also provide some thrust. So the name of the game is not too large, not too small..

I just dont buy that the prop just fell apart on a rotax UNLESS there was a maintenance issue.

Hi Ian 18x24m, 5.5m to gutter. There is a 25m block width (50m deep). this leaves 25-18 = 7m only for outriggers for doors Preferred option is on site poured and tilt up concrete, but I cant seem to get the proposed contractors mind on the job, the has too many late running jobs right now due to wet and boggy condix. they can do four tracks. short listed shed kit supplier only does two row doors. I have specified that I only need 14.5m open to one side at any one time, so the two track solution is 3.4m outriggers, and 6 x 3m doors . three doors on each track so three are pushed over on two tracks to one side and I get a 15m opening one side. push doors over the other side, I get a 15m opening the other side. Up the middle, that's only 12m opening. But the intention is only two active planes one in each side of the front part of the hangar. airplane projects can go down the back. workshop+mezzanine in the rear half. This is not a 'club hangar', so is purpose built. Ideally, Cowra would have T access hangars. commercial details by PM Glen.