I just test ran the PAW 19 in my OTS Ringmaster, the Aerodyne fuel is great. It took all of ten second to get it to fire then another 30 to get the needle open enough to run, one choke one flip going (very lucky I know). After warm-up backed off compression 1/2 turn and leaned to peak. I am a happy flyer. Now I can go to the field and see how we do in the air.

Question is because it will lean through the flight do you go off a hair on the rich side?

One other thing, the 90% Iso alcohol and a touch of detergent works great for clean-up. The Aerodyne fuel seems to burn very clean with very low odor.

Where do you get Aerodyne fuel and how much is it?

Hi Stuntguy

I would go a touch rich on take-off as the engine will unload once moving (pickup rev's) and this will prevent over heating.

Ployd

Chevy, Aerodyne standard diesel is available via mail order in pints ($6.95), quarts ($10.95) and gallons ($33.95) (Current prices shown on web page). Their email: [email protected] (Allen), they except credit cards, Paypal and money orders. Their web site is: http://www.freeflightmodels.com/index.html.

Weekend was the first chance I had to fly, day was great and things went pretty well. One problem that cropped up was binding between the drive washer and the case. I have two PAW 19's and one drive washer ( I need to order one from Eric C) on the engine I put in the ship the drive washer fit with almost no end play. I thought this would be a good thing cause I wanted to use the starter. Well truth is you need some end play on the plain bushing engines. I think that as the started pushed onto the spinner it just move the drive washer in and caused the binding. I did get one flight in before I noticed the bind but the engine was low on RPM at only about 8400 on a 10x4. Lap time was 5.4 on 60 ft a little slow would like 5.1. Knowing about the bind I changed to the other engine tha has a little end play and expect this will work better an get a little more RPM.

Some pics attached.

Finally got into the air on Saturday and had a couple great flights. Used a Top Flite 10 X6 Power Point (raked tip) on the PAW 19DS with standard Aerodyne diesel fuel, 1 1/2oz wedge uniflow tank. The engine had be test run on the ground to get the rough settings which were about 1 3/4 turns open on the needle and the compression were it was when I got the engine from eBay.

First start was by hand flipping, two chokes, hard flip engines started and was overcompressed, quickly backed out compression screw till it lost a little rpm then leaned the needle till misfire, opened needle 1/4 turn and adjusted compression for max rpm then backed off 1/8 turn.

On the flight line for the first flight I cheated and used the starter at the run compression setting but opened the needle 1/8 turn. One choke and applied the starter, in very short order it fired off and slowly came up to smooth run. Just as I was leaving for the handle it started to misfire so I opened the needle another 1/8 turn. I don't think it was all the way warmed up cause the launch was a little slow but once we cleared the grass it picked up speed and after about 4 laps it really came on. Since I wasn't sure about how long it would run I flew the Old Time stunt pattern maneuvers one after the other to see how it would do. It did really good. Seemed to bog a bit at the top to the vertical 8's and overheads. At the end of the tank the engine simply misfired about four times and quit nice and clean. Looking at the oil and with the bogging when the load came on it seems like it was a tad overcompressed.

Next flight I backed out the compression 1/8 turn, one choke, a couple flips to make sure is was hydr locked then applied the starter, off it went. This flight I felt there was enough fuel for the complete pattern, again took a few laps to come in but for OTS the first couple maneuvers are the climb and dive so not much power needed by then the motor was in and the wing over was no problem. This was only the fifth diesel flight I have flown ( one with an under compressed Drone, one with a OK Cub 074 and one with a ST 15D on a Jr Flite Streak and at the time almost had it right) I was very happy with the way it performed. Since changing to the PAW 19DS reduce the weight to about 25 oz the Ringmaster flys much smoother, it takes a bit to get use to the very lite pull. After the flight looking at the oil its now dark honey brown so I think its just about there. If all goes well over the next couple week I will use this set-up at the Fall contest in Starky, FL.

How good does it get? The Ringmaster brings back memories
of my youth and the PAW .19 is one of my all time favorite
engines. You sure built a nice looking model there.congratulations.
Ralph

You didn't mention if these PAWs are new or have been broken-in. If they are new and you only have a few minutes on them, I would suggest further break-in on the ground.

For the one in the plane, just run it at peak for a minute or so while holding the plane, then pull the fuel line to shut it off and let it cool for five minutes or so to heat cycle. Do this about 10 times. That will condition the piston/cylinder for maximum life/performance. Most iron/steel diesels do not heat up fully until they are run for a minute or so anyway. This will allow you to make adjustments to the compression and fuel so that you can get your best settings for when you launch.

As the engine is heating up, I like to back off compression and increase it to smooth running. You may have to adjust needle and compression several times during warm up.

Here is a diesel combat site that has great info on the care and feeding of diesels, especially PAW:

http://www3.bc.sympatico.ca/dieselcombat/index.htm

Good luck with your Ringmaster and PAW.

George

Thanks to all on this site my learning curve has been greatly shortened. The information here and on the combat site really helped me zero in quickly to get a very flyable setup.

The PAW is a used engine that I purchase on eBay and appears to be broken in but has very good compression seal and no wear on the shaft bearing, no rod slope either. The second one is also from eBay but needed some parts (drive washer, NVA) that I borrowed from the first one which proved to be a little to much taper in the drive washer and once the prop was tighten down caused a slight rub so I changed engines and will send the one in need of parts to Eric C to be setup and will have him add a tube muffler which requires some machining of the fins that he has a fixture for.

The next project is the PAW 35 that I again purchased off eBay. It is NIB and I will follow the break-in advice provided here and on the combat site. I'd like to get this into a PAMPA stunter soon, just need to pick which ship I will replace the four stroker in.

Some lessons learned about the PAW 19 in the Ringmaster: It can be started quit easily with a starter at the run settings from dead cold. It takes about a minute to fully warm and come in, so you need to start it and take your time, in the OTS pattern just about when you finish the climb and dive it will come to full power. If you increase compression to hand start you need to make sure to back out enough. On control line ships you need to go off between 1/8 and 1/4 turn rich from were it starts to miss, when it is warming up is may still miss even at this setting, need to get the feel for this, it will lean as the fuel load burns down an if to lean will start to miss at the end of the pattern. On control line ships narrow long tanks are better than short wide ones to reduce the fuel head change due to centrifical force acting on the fuel.

So far this is what has work well for me, again thanks to all the input and information from this site.

If you go to a uniflow tank you will not have the leaning out problem. Sounds like you are doing very well on the learning curve.

HELP - Not as far up the learning curve as I thought. Today had a bad few flights with low rpm and rough running. Started from last run settings, engine fired from cold on hand flip. After start it missed a bit then ran continuous but at only 7300 rpm, 10x6 TF power point prop, Aerodyne fuel. I tried to lean until miss than backed off 1/8 turn. Since it started cold from the last run setting I backed out the compression 1/8 turn but noticed power drop, figured it was still warming so off I went. In the air it never got better, lots of vibration - so much that the lines looked like plucked guitar strings. After flight I looked at the oil and it was a darkish brown, just about were I though it should be. On the second flight I switched to an APC 9x7 thinking maybe it was happy and just need more pitch to pick up the lap time - WRONG! Things were going down hill. Oil still looked great. On the third flight I went back to the 10x6, I thought it was a little lose on the first flight being wood and this prop worked well last week. Start was great, I went in on the compression just a hair, it was still running rough but better. Off I go and about 2 laps in it came on and smoothed out, I though I had it but as soon as I pulled the nose up for the climb it went rough and stayed for the rest of the flight. The soccer kids arrived at the field we use and we were done for the day.

OK, what did I miss? I thought that if it fired on a hand flip that once started you would need to back-out the compression to get the right run conditions. I also thought that you had it right if the oil came out dark honey brown not black.


Thanks..

Sounds like its undercompressed or lean- undercompressed needs a richer needle to maintain a smooth run. I find upping the compression and leaning the needle till the revs max and hold then back off the compression-just ie 1/8th turn then open the needle a little generally gives more consistant runs , keep opening the needle till it flys your pattern.
Stewart
Oh my exhaust tends to run blackish due to the higher power settings

I find, with St G20-15's, the best runs are when the exhaust is clear. A little honey-colored is OK. Also as an engine is run more, I find that the compression needs to be very gradually backed off, exhaust clears, and performance improves. If you are running dark brown to black, I think you are overcompressed. Also, I think you are running more prop than your engine likes. I would try a 9 x 6. Diesels are, I think, more idiosyncratic than glows, and what is true of one may not be true of another.

I agree with Jim about the prop, a 9x6 is about right on a PAW19.
Jim I tend to run my diesels nere max but not overcompressed , i have noted different exhaust colour depending on the fuel used - kero based fuel runs clearer than fuel made with Jet A , ether content also effects the colour of the exhaust.
I have just tested fuel useing modded olive oil as lube and even when maxed out the exhaust was clear, Im very happy with the results useing olive oil.
Dont forget a motor will unload in the air causing it to run cooler than on the ground giveing an effective compression drop, so unless its pretty rich an undercompressed motor will sag in the air.
Stewart

I think you missed the part about not launching your plane until the engine had FULLY warmed up and you had made final adjustments.

Try holding on to it and adjust compression and needle until it has run for two to three minutes. As a final adjustment, lower compression, then increase until it runs smooth. Make a final adjustment to the needle. You can get off a couple of clicks rich and still have most of your power. If it is too lean it will just quit.

From that flight, you can try a little more or less compression and needle for better running. Remember your running compression setting when you need to change compression for starting. My limited experience with Aerodyne is similar to Jim's...exhaust clear to straw.

Don't be so impatient about launching that plane before you have it running right. Remember, your running setting will vary a bit with different props.

George

That's a good reason to never use an electric starter on a plain bearing PAW. Don't tell Dr. Diesel what you did.

I need to point out that the problem with the drive washer was not caused by the starter, the washer started to bind when I tightened the prop nut. When I changed to the other engine were there was some end play all was fine no matter how tight the prop nut and it did not change when using the starter. The starter works great!

One needs to make sure that there is no hydro lock before appling it. I have had very good success by filling the tank then one - two chokes, then start. You don't jam the starter on, you position the prop to the down side of the compression stroke then apply the starter to the spinner then apply the starter switch.

I am again a happy diesel guy. I did some testing with the PAW 19DS, seems like it likes the Master Airscrew 9.5 x 6 prop best. I started with the Top Flite power point 10x6 that kinda worked before and it was not happy at all, the vibration was so bad I could hardly hold the compression screw to make adjustment, finally it quit. I then changed to the MAS 9.5x6 and it was like a totally different engine, smooth and powerful low vibration just were I wanted it to be. Any ideas as to what could cause this kind of drastic change? (the prop was slightly off balance but this should not have been enough to cause it to shake this much)

Flying control line with glow engines always made me conscious of how small the fuel tank was and made me hurry.

With Diesels, you have a little extra time anyway, especially if you are using a fuel tank sized for glow. <G>

I'd love to find some folks in the Chattanooga, TN area that are flying control line. I miss the old routine. Control line was a lot of fun. Adding Diesel engines to it will make it all the more enjoyable.

Ed Cregger

Had a very good day yesterday with the PAW 19. I still have no idea what caused the sever vibration two weeks ago but on the Mater Airscrew 9.5x6 it was the best flight I have had and it was up to competition level of performance.

I have not disassembled the engine to see if there was anything inside that was suspect, the puzzling thing is all I did was change the prop and the problem vanished!!! There was no binding but does seem like it was something physical, any throughts?

It looks like your MA props are plastic and the TF is wood. I think difference in rotating mass could cause this. The speed of the crankshaft is not constant. It slows under compression and accelerates after ignition. How that interacts with the flywheel action of the props could cause a problem like this. It should be noticeable as torsional vibration. Another possibility is that although the prop was statically balanced on a balancer, dynamic balance was out. This shouldn't be a huge problem because props are short in the axial direction. One last idea is that one blade has significantly more pitch than the other.

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Any two-stroke engine, whether gas/diesel/glow requires LESS fuel when under less of a load (unloading) than when under more of a load. We run them a bit rich at takeoff to compensate for the fuel tank draining during flight and providing less "pressure head" to the carburetor.

YS engines do not require this richening at the beginning of the flight because their pressure/regulation system compensates for the fuel burn-off during flight.


Ed Cregger

I have now had several good weekends with the PAW 19 using the MAS 9.5x6 and Aerodyne fuel. Looking back it seems that the vibration problem was a combination of undercompressed and very rich mixture. It may have been just on the verge of hydro lock with the extra liquid giving the needed compression to keep it running. Anyway all has been fine and I now want to try to low the lap time for 4.8 sec (60 ft lines) to 5.0 sec. I will try an cut down a MAS 10x4 to 9.75 and repitch (heat gun) to 4.5 to start. The engine is turning at 10.4K rpm on the 9.5x6 so I think I could load it to reduce the rpm to 10K even and still have a smooth run.

You might try a 9 x 4 or 9 x 5. Let the engine turn up a little more but with less pich.