Author Topic: Modern diesels (Read 2228 times)

Steven Kientz · « **on:** April 07, 2008, 04:35:20 PM »

Was wondering why diesels weren't more common in stunt. It seems the "modern" ones should be more than up to the task. More torque( larger prop) and more fuel efficient. From what I've heard they run at constant RPM, no 4-2-4 break required. Just curious, not trying to start any major arguments or conflicts.

Thanks

Steve

Jim Thomerson · « **Reply #1 on:** April 07, 2008, 08:17:57 PM »

And you get a 5 point bonus added to your score in Old Time Stunt.

To be a little more helpful; you are unlikely to see a diesel for sale in your local hobby shop, nor fuel for same. This means you have to order either a conversion head from Davis Products, or a PAW from Eric Clutton or Carlson. Fuel from Davis, Clutton, Aerodyne, etc. Running a diesel means you have to forget a good bit you learned about glowplug engines. Most people have never seen a diesel fly, and even fewer have seen one run well. So getting help or advice at the flying field is an iffy proposition. Never the less, diesels are great fun, and an easy way to be peculiar.

Steven Kientz · « **Reply #2 on:** April 08, 2008, 02:20:53 PM »

I've been told that peculiar is in my nature,ask my wife she'll tell ya. Looks like there will be a diesel in my future. Especially since my father had one many years ago( early 50s) and never got it to run,although he said it did like to bust his knuckles.

Steve

rustler · « **Reply #3 on:** April 08, 2008, 02:53:53 PM »

Enya is doing some interesting C/L diesels at the moment.

Mike Spiess · « **Reply #4 on:** April 08, 2008, 03:23:21 PM »

I flew with diesels till I wore them out. Paw's from Carlson Engine Imports. I loved them but your right Jim getting fuel is kinda dicey. So I got so I mixed my own and only as much as I needed for one or two times flying. It does lose it's pop very quickly. I had many things I did to keep it fresh such as store it in a cooler with ice and only take enought out of the container for a single flight. But the worst was no matter what you did when it got to 90 deg with hight humidity they would never start.

You may not know it but alot of the summer here in MN is like that. But they start great in the winter. even have frost on the exaust somtimes.

raglafart · « **Reply #5 on:** April 09, 2008, 05:11:19 AM »

"they start great in the winter. even have frost on the exaust somtimes. "
Wherever you live, I never ever want to live there!!!!!!!!!
Cheers JG

Mike Spiess · « **Reply #6 on:** April 09, 2008, 07:34:09 AM »

Quote from: raglafart on April 09, 2008, 05:11:19 AM

"they start great in the winter. even have frost on the exaust somtimes. "
Wherever you live, I never ever want to live there!!!!!!!!!
Cheers JG

Yea you find out what cold is by getting alcohol on your fingers at any thing bellow zero

phil c · « **Reply #7 on:** April 10, 2008, 09:00:17 AM »

Steve, probably the biggest reason you don't see more diesels is the stinky fuel. It get into everything and you really have to wash your clothes after every flying session or before you stop at a restaurant.

The compression adjustment throws a lot of people off too. Diesels do get better fuel mileage. 4strokeing vs 2 stroking can get confusing too. A diesel can 4 stroke either from too low compression(that blat-blat sound), being too cold, or from being too rich just like a glow engine.

Diesels don't produce more torque per se'. The compression adjustment allows you to set compression and get a good run on a larger prop, but a glow engine that has been tuned the same way will also turn a larger prop. Henry Nelson did some tests on his engines a loooong time ago. The diesel and glow versions of the 15 ran within a couple hundred rpm when tuned for the same size prop.

Steven Kientz · « **Reply #8 on:** April 11, 2008, 01:45:22 PM »

Well, I guess the only diesels I'll own will be hangar queens. Between smelly and oily to hard starting in hi humidity, I'll have to stick to glow. I'm pretty sure alot of people know about Indiana's heat and humidity(NATS IN JULY) issues. No one in our club( Plainfield Screaming Eagles) runs a diesel, as far as I know.

Thanks

Steve

Jim Thomerson · « **Reply #9 on:** April 11, 2008, 02:26:59 PM »

Humidity has no effect on how diesels start. So far as smell goes, I've gone through maybe 20 gallons of diesel fuel; and I'll admit, I used to think it had a smell.

. The oiliest of diesel mixes is around 33% oil; not much more than recommended for Fox 35, etc. Modern ABC conversions can run on less oily mixes.

Al Burczycki · « **Reply #10 on:** April 12, 2008, 06:43:29 PM »

Steve,

Al Burczycki · « **Reply #11 on:** April 12, 2008, 07:18:50 PM »

Steve, Sorry for the short message, sometimes my fat fingers take control. In any case, I too am attracted to the Diesel and have been flying a PAW 19 for two summers. It get quite humid here in Michigan also but I've not noticed any starting problems. The problem I have had is figuring out the correct venturi size for a Diesel. As received (new) the venturi area was .0175 sq. ins. Starting was not a problem, but getting a good needle was. I couldn't get it rich enough. My fix was to install a restricter down to .013 sq. ins., much better. I believe it can still be lowered some more and actually run better. I also have a PAW 29, and had the same problems. The venturi area on it is .021. Both of these area's are in Glo engine territory. I have just picked up a PAW 35 with a throttle and it has an area of only .005 sq. ins., so I think I'm on the right track. It would be nice to hear from someone with Diesel experience on venturi sizing for stunt work. I also have a Davis diesel head on a Super Tigre C35 and it works quite well. I fact, after starting the first time for the day, I seldom have to change the compression as I do on the PAW's . Perhaps it's just newness, as the PAW seems to start and run better each time I use it. The PAW 19 is on a Sterling Yak 9 on 54 ft. .015 lines and flies quite well. I take only enough fuel for the day with me to the flying field, and keep the remainder in the original container tightly sealed, and have not had a problem with the fuel deteriorating. You should give it a try, it's kind of nice to just walk your plane out to the circle and carry only a rag as starting accessory.

Cheers, Al B.

john e. holliday · « **Reply #12 on:** April 13, 2008, 07:27:43 AM »

Yes diesels are a rare breed. When I was trying to learn to compete in F2C we were running Super Tigre .15's with a Tee Dee venturi and needle valve assembly until KKK came along with their needle valve assemblies. We finally got Rossi's and the last engine was a Nelson. The Nelson was the scary one with only 10% oil. The kerosine is where the power is at. Pump kerosine at the local station was good and oily so it meant less castor. When we tried the high grade kerosine lamp oil then we discovered you had to add more oil. We also found we could purchase different aromas. Could also buy motor grade ether in 5 gallon tins at that time. Now I have to buy the cans of motor starting fluid in the spray cans. Each can gives about 9 ounces of ether or what ever it is. It does work as the old Enya .29 I sold started on just about a dozen flips. When learning to start diesels you need a heavy duty glove(construction glove). Get a heavy prop. We used a big 13-6 cut down to 7 inch diameter for initial starts. Biggest problem is people over compressing the little critters. That is when they start biting. If over compressed the engine will spit out black goop, under compressed it will stutter/not run smooth. The needle sets the amount of fuel so it will tell you also if too lean as it will seem undercompressed. As with any engine it takes practice. As stated earlier when the compression is close you usually don't have to mess with it unless you are going for that last bit of rpm out of it. You will in time notice that in level flight the diesel will tell you if it is running hard or not. If running hard/hot just start leading the plane(whipping) and see if it comes around. In F2C if it didn't come around you shut off and reset. But, when all else fails contact Jim Thomerson as I have watched him put in flight after flight with a diesel at VSC. Lou Crane is another one. They both post on here. Have fun, DOC Holliday

L0U CRANE · « **Reply #13 on:** April 13, 2008, 01:42:47 PM »

Thanks for the cue, Doc...

Probably the best way to get a sure, quick, adjusted start with a diesel for stunt in a contest is to signal the judges to wait for your definite start signal, then turn away from them so you don't confuse them.

Start the engine, and let it run up to full heat. If you'd started it just before going on the circle, that's one or two flips and about 10 seconds. When you're sure it is on-setting, point the model's nose down to uncover the fuel pickup, and block the vent air inlet. About 2 seconds to complete stop.

NOW, signal the judges for the start... If it takes 2 flips or 1, it will be back on-setting just about as soon as the noise starts. No twiddling fuel or compression...

BTW, I've found campstove kerosene is quite low odor from the git-go - who would want to sleep in a tent that smells like the bilge of a rust-bucket coastal oil-freighter??? Any ether odor is gone when it burns, too. The exhaust smells more like the steam from an old downtown hand-laundry - anyone else remember those?

But, yes, you do get a light to medium coat of very detergent-resistant lube on your skin and clothing... Part of the joy of the thing...

Steven Kientz · « **Reply #14 on:** April 13, 2008, 01:59:06 PM »

I thought a diesel would be different( I'm the only "true" C/L member of our club). Of course that being said, I guess I'm different enough. I have convinced an ex- pattern flyer(R/C) to build an enlarged version of the Flite Streak(Pat Kings plans). He said he would show me how to "bag" the fuselage(built of several pieces of 1/4 balsa and 1/64 ply). Hope to post the build as we go.

Steve

Chris Gilbert IRL-1638 · « **Reply #15 on:** April 16, 2008, 04:20:58 PM »

Diesels are fun, but are definitely SMELLY (but that's not a bad thing).

When the compression is right the oily residue (which will envelop your model) should be honey coloured.

In this part of the world humidity is never far off 70% (though the temperature never goes above 90, or much below 20), and when the starting technique has been mastered a few flicks should get any diesel going in any conditions.

I always start off with a large diameter heavy prop with a new engine, just to find the approximate settings, then progress to a more usable diameter.

Larry Renger · « **Reply #16 on:** April 18, 2008, 09:50:01 AM »

The problem I had with diesels in stunt was the variability of the run. Not the power, that was always great. It was the run time. At the final contest I flew with a diesel, I ran out of fuel on the first flight at the overhead 8 and overran on the second flight with the identical amount of fuel. I sold the engine, plane, lines and remaining fuel right then and there.

I still enjoy flying diesels for sport, though.

My favorite ddiesel engines are the PAW 55 (.035), OS 25 DDD, PAW .061, and the C*X Conquest .15 DDD. I flew the OS .25 DDD for some years, and put at least 3 gallons of fuel through it, less than 2 ounces a flight. After I sold it, I heard the new owner put another gallon through the engine and it was still in great shape.

My wife HATES it when I run diesels (not wild about glow fuel smell either, she likes slope soaring!)

Dave Hull · « **Reply #17 on:** May 23, 2008, 02:32:56 PM »

I found someone's earlier comment on air temperatures interesting. We haven't found it any more difficult to start a cowled racing diesel on hot days, but on cooler days we have had some problems getting it started the first time and getting it warm enough to restart well. We have found that the humidity in the air will affect run time, if the engine is set to maximum power. (You need some kind of benchmark.) It seems the H2O displaces some of the O2, so you have to retune compression and mixture. At our local field, we have seen up to a 28% increase in laps on damp days. There is a similar effect with the density altitude. With a Nelson .15, we were only getting 22 laps in LA, but for a contest in Tucson with density altitude of about 5,000 feet, after a compression and needle change, we could get around 30. So for a stunt sized tank, that could translate into a LOT of extra laps! I'm sure the same tuning things happen to a stunt engine, but it is probably less noticeable.

Dave "McSlow" Hull

FLOYD CARTER · « **Reply #18 on:** May 29, 2008, 12:55:00 PM »

I have se veral diesel engines. The cutest is a little Russian replica of the elfin 1.8cc but this one is reduced to .020 cu in size. Motors this small are not very useful for C/L stunt.

Floyd

dankar · « **Reply #19 on:** May 29, 2008, 02:26:02 PM »

My Diesel's go into FF ships. For UC no way unless just for fun.
Dan