Cooling factor ??
 

Ok guys your thoughts or opinion on this one, a couple of years ago when flying my apache ll which at the time had my irvine 40 diesel in it. (this is Florida)
and this rain squall hit in minutes when the plane was quite a ways out. It of course cooled down in a hurry developed the diesel miss but kept running
and we got her back and landed under power, of course as soon as went below half throttle it quit. I wonder if a glow engine would have kept running
under those conditions ?? martin

may be a dumb question since engine in boats are usually water cooled anyhow

RE: Cooling factor ??
 

Ihave seen ice placed on the head of a glow engine before and that had no effect on how it ran but that was in a test mount, it melted it rapidly whereas the Diesel did not do so as fast - but bothe kept on running .
So I am wondering here was it just the 'coolng effect' of the weather or water being ingested into the engine that actually caused the missing?

As I am struggling to see how a shower could cause a miss in the engine if nothing else came into play.

But honestly I am just summizing here.

RE: Cooling factor ??
 

Recyled Flyer... Interesting on the ice cube thing, I was conservative on the term shower, it was a downpour it is likely the miss was due to water ingestion
certainly the carb would have sucked some in, think you called this one thx . My glow time is limited to 4 strk I do have some Saitos, ASP/magnums and an OS 4strk
but almost all my flying is with diesel much easier no plug or battery issues

With the limited use of the the 4 strokes after a run I put a small amount of davis fuel in them and run for a very short time ( with the glow plug attached)
this rinses out any trace of nitro or alcohol. the castor and kero does a great job. I have never lost a bearing or had a corrosion or rust issue. In the factory
sheet that came with my OS10 they state rinse the engine with kero if storing for any length of time interesting martin

RE: Cooling factor ??
 

The condition you experienced was over cooling. Boats are water cooled but they aren't over cooled. Generally they need to reduced water flow in very cold conditions to get the engine up to normal operating temperatures. Diving through several hundred feet at idle with a diesel can over cool it and it might miss for while until it warms up after opening the throttle. I've experienced it before. I think glow would have kept running as long as you didn't take off lean.

RE: Cooling factor ??
 

I have flown control line glow plug engines in mild rain (no lightening) with out any problems.

RE: Cooling factor ??
 

I suppose that the conditions could be replicated in a test stand, simply mount up the engine, protect the intake and lightly hose down the running engine.

Do the same again but add a misting spray of water towards the intake (if you dare!)

My bet is that it is the water on the interior rather than the exterior that has the greatest effect here as it would expand rapidly into steam and effect the firing long before any cooling effect from the outside would be felt.

My opinion would be that a diesel would suffer before a glow if water droplets were added the fuel mix but I ain't about to try and find out!

Cheers.

RE: Cooling factor ??
 

Recycled Flyer... Think you nailed it s small amount of water would mix with glow fuel (methanol) the stuff is quite hydroscopic so is ethanol, adsorbs
water. Kero does not it ,follows that the water from the rain would still stay as a mist not mix with the diesel fuel hence the miss and yes we are not putting the theory to the water spray either martin

RE: Cooling factor ??
 

I'm going flying next time it rains.

RE: Cooling factor ??
 

Hi again AMB,
I was loathe to mention the hydrophilic nature of methanol before as I know that some full size engines use a methanol/water mixture to boost octane ratings and thus power but what I don't know here is whether your engine ingested a homogenous fine 'mixture' or simply small and seperate drops of water that exploded into steam.

Isuspect the latter.

But there are also rare occurances of full sized diesel engines using water injection in the inlet manifold, but here it is done through the medium of an injector and thus is a fine mist as it is very easy to over hydrate a diesel. So my best guess is you got the combustion process interferred with by undispersed droplets that did not mix with the fuel and thats what caused the misfiring.

And Jim, what would you do if the rain storm you were flying in turned into a lightening storm? Ditch the model? (Have fun wrestling over that one!)

RE: Cooling factor ??
 

Recycled Flyer : Moral here, keep a weather eye, our little diesels are hydrophobic, and I don't want to play Reddy Kilowatt with lightning possibilities
in an open field with that nice little lightning rod on my transmitter either martin

RE: Cooling factor ??
 

In days of old engines were designed to do their best work on a 60 degree standard day, many older vehicles would feel like thay had 25 more hp on a 60 degree humid day.

RE: Cooling factor ??
 

Hi Hobbsy Interesting point The cooler the air the more dense thus more oxygen that would give better combustion
maybe a little humid even denser ?? bigger charge in cylinder makes sense think Boyles gas law come into play here martin

RE: Cooling factor ??
 

I believe the humidity turns into steam during the combustion process, if your little diesel would do that to rain drops you'd have a real powerhouse. I am not familiar with Boyles gas law but interested if that's not too far from our discussion here. Thanks

RE: Cooling factor ??
 

Hobbsy The basic principle of Boyles Gas law is any gas (even air) expands as the temp increases less dense and the converse of course as it gets colder, gas can be compressed to a point where they become a liquid, CO2, freon, allowing a temendous amount to be stored and as released becomes a gas again. and cools this of course
follow an equation for temp and pressure martin

RE: Cooling factor ??
 

[quote]ORIGINAL: AMB

Hobbsy The basic principle of Boyles Gas law is any gas (even air) expands as the temp increases less dense and the converse of course as it gets colder, gas can be compressed to a point where they become a liquid, CO2, freon, allowing a temendous amount to be stored and as released becomes a gas again. and cools this of course
follow an equation for temp and pressure for a more detailed and precise explanation go on wikipedia an look up Boyles law easy to understand martin

RE: Cooling factor ??
 

Humid air is less dense than dry air. Water molecules are lighter than the rest of the molecules in air, O2, N2, CO2, etc. I think, if warm enough, air can contain as much as 4% water. Yes, with lightening, I quit flying, immediately.

RE: Cooling factor ??
 

Martin, to yours of June 10th...

Talk about an antenna in your hands? Jim T and I fly primarily control-line. That's about a 60' antenna waving around. YES, we watch for lightning!!!

RE: Cooling factor ??
 

And when you include both the positive(+) down line as well as the negative(-) up line you may as well say its 120' antenna doing a hemispherical radar sweep of area looking for the nearest short circuit!

Iguess that I too would ditch a control line model in a lightning storm but the mental wrestling involved in deliberately wrecking a model would give me pause to consider "How long till the fuel runs out?"

RE: Cooling factor ??
 

Trust me. You will make the decision to dump it real quick.
I did in the first few laps of an official flight and I just got a
fairly mild jolt,but a lot stronger than the average static buzz.
Ralph

RE: Cooling factor ??
 

You were lucky, lightning sometimes sends out little "feelers" before the main bolt to find the easiest path to ground martin

RE: Cooling factor ??
 

Funnily enough the field where I used to fly control line has high tension power lines running behind it and every time your eye caught then in the background you would involuntarily take a step back from them even though they were at least 300m away!

But yeah, your right I would have to simply run the prop into the ground - but hopefully in the inverted position to minimise the damage caused.