ORIGINAL: 1705493-AndyW
ORIGINAL: colingw
ORIGINAL: 1705493-AndyW
Colin,
Ether may go the way of the Dodo if the runs on my own PAW are any indication. We may not even need ether in the prime. But you're right, throttling can be an issue on pure kero. More to come.
Andy,
What was the fuel mix, and what was the starting like? Any special starter mixture, or an electric starter?
OK, this has me fired up to try a fuel with say 25% castor, 1% redex, 1% DII and the rest automotive diesel fuel. Maybe make some priming fluid with john deere starter, or even just acetone. (This will just be bench running, I don't have a plane for the PAW yet, having just re-started control-line after a 20 year absence. I'm building my first planes in 20 years at present, but using glows, a Cox .049 in a 1/2A 'Stunt Chimp' and an OS MAX-III .15 in a Brodak JR Flite Streak respectively.)
I have a feeling the PAW 19 may run and start better on this than the MARZ 2.5s and the PAW 80 (.049). (My MARZes and the little PAW aren't broken in yet - the 19 is relatively high hours and was always a two flick starter even on 10% ether).
One additional data point: my flying buddy in the old days ran a PAW 249DS. I seem to remember it was a bit cranky starting on the 10% fuel I made up, but he tended to run a small prop at high revs where I had a 9x6 or even a 9.5x6 on my .19.
By the way - I'm so glad I found this forum (pointed out to me by someone on
www.clstunt.com ). Great to find plenty of other 'oily hands' out there.
Colin,
By now, all the PAW videos are posted and should fill you in.
Acetone, as Kelly has informed, was going in the wrong direction. I was looking at it as a highly volatile fluid but its cetane rating stinks. It's actually an octane booster used sometimes to smooth out glow power runs. Cetane and octane are like yin and yang.
Can we assume that Redex and D11 are cetane boosters? These are down under products? If so, as my preceding post indicates, you may have good luck at 5 or even 10% concentrations.
You're right mostly, that the bigger the engine, the less fussy they are but for the small ones, it's just a matter of getting the mixtures right at all throttle settings.
But wait, your buddy ran "small" props on his .19? And you ran "big" props? A 9 X 6 is common for a glow .19. I'm remiss in not mentioning that, typically, to push the diesel concept, I run .06's like the PAW and Norvels on 8 X 4 props. And they like that a lot. Are you running diesel WAY too fast? My .15 was tested with a 10 X 4 and sounded so good, that it WILL be the prop I'll use on my small Pitts.
Hi again Andy,
Redex is a (no longer available?) upper cylinder lubricant which was traditionally used as a fuel additive. I seem to get a smoother run and far less carbon build up when I use it, so I'm assuming it has some detergent action. It is fantastic for freeing up gummed up engines.
DII is an acronym for Diesel Ignition Improver, when I say that I mean Amyl Nitrate, Isopropyl Nitrate or whatever else is available.
For the plain bearing .19, PAW recommend 7x6 to 10x6. I was typically running at the upper end of that range with 9x6 or 9.5x6, sometimes 10x6 - all Master Airscrew. I'm thinking about a 10x4 or 10x5 APC may be ideal.
My mate had a 2.5cc 249DS, and definitely under-propped his, usually running an 8x4 or 8x6 tornado. It screamed! I reckon he should have been using at least a 9x4. He not only used smaller props than I did, he also used lighter ones which were somewhat flexible and would de-pitch at high revs. I definitely got far more out of my .19 on the bigger, heavier and more rigid master airscrews - first plane I had it in was rated for engines .19-.35, and was typically flown with something like a Fox or McCoy .35 - but my PAW 19 flew it with authority, no loss of line tension when overhead.
From memory my mate really used to wind the compression down and had to wind back to start, whereas my 19 would give a 2nd flick re-start on the running compression with the plane still right way up (engine inverted). Just fuel, choke and go. Again, his setup would never restart with the engine inverted, so he used to do this dodgy thing with holding the plane upside down on his lap, then flipping it with the engine running! I hated seeing him do that.
PAW say a 9x5 is the max for their .15, and and 8x4 for the .06. My small PAW is the original .049 80DS R/C, although I'll probably change it to a C/L venturi unless it ends up in a 3-line model.
Does anyone know what an Aussie equivalent of AMSOIL Cetane Booster would be, or can we get that here? The Aussie importer
http://www.a1oils.com.au/ doesn't list their Cetane booster.
Possibly something like this would do the trick:
http://www.redlineoil.com.au/product...#fueladditives
"85 Plus—Diesel Fuel Enhancer promote better fuel combustion and fuel system lubrication. Contains Cetane booster! Significantly reduces the effects of low sulphur and poor quality diesel including winter fuels, lengthening injector and pump life. Provides faster ignition, reduces engine knock, detonation, smoke & emissions, and improve engine efficiency. Extremely powerful high-temperature detergents clean injectors. Diesel fuel additives are EPA registered."
And do you think hand starting is going to be feasible? I have an electric starter, but am somewhat leery of using it on diesels (probably just an old wives tale).
--Col