My P40 Maiden Flight

[Kafin Noe’man]

Finally, my P40 has made its maiden flight.
Good flying airplane in general (very authoritative and stable in the air), though I still have to find the perfect prop and engine setup combination.

I currently put
OS LA-46
TT 11x4.5
Nitro 5%
60ft lines eyelet to eyelet

I did experimenting several launch RPM:
9500ish — gives me 5.6 sec lap times with just okay power
9750ish — gives me 5.0 sec lap times with good power, but sags at some point.

I’m still not happy with how the engine runs as it shows very dark/black fuel residue which can also be an indicator that the engine is on too lean side.

I’m going to try other prop sizes.
Will try putting APC 11.5x4 first, then 11x4, and lastly 11x5.

What do you guys think? Which prop size should be the first try?

[Ken Culbertson]

I ran an OS46LA on my profiles a few years back.  Slightly larger plane (620 Squares,58oz) MAS 11x6 at 9500 on 62' lines. I ran a fast 4 on 5 or 10% and had no power problems.  I am not familiar with your weather so you should rely on others for the fuel mix.  My experience with the LA46 is that it likes to be loaded.  I had very bad results running higher RPM lower pitch props.  The 11x5 should work but you might try the 11x6.  Pix is just to show you the size plane it is pulling next to a much smaller Nobler ARF.

Ken

[Dave_Trible]

I’d go with the APC 11-4 or 11-5 if you need more speed.  However the black residue is corrosion in the engine and says it’s about done.  Common in humid climates or near indoor humidifiers very long.  Ask me how I know….

Dave

[EricV]

I’d go with the APC 11-4 or 11-5 if you need more speed.  However the black residue is corrosion in the engine and says it’s about done.  Common in humid climates or near indoor humidifiers very long.  Ask me how I know….

Dave

Dave is probably right, but being the eternal optimist, you might check that big muffler and make sure you have the interface smooth and flat and there isn't a vibration/ loose rub going there that is making the black metal.

EricV

[Colin McRae]

Kafin

I run an Evolution 36 on my P40 ARF w/ MAS 11-4 prop. The EVO 36 has roughly the same power as an OS 46LA. And I am running 60' 018 lines. And I typically run 10% nitro and 20% oil on my more modern engines. My ground rpm is around 11,500 on the MAS 11-4. (BTW, some have said the MAS props generally perform as if they had less pitch. In other words, a MAS 11-4 probably performs more like a typical 11-3 as an example. Not sure but maybe they flex under load relaxing the static pitch.)

I can't speak to the black oily residue or the health of your particular 46LA engine. But my description below assumes a 'good running' LA engine.

You also have an 'after-market' venturi and NVA. That setup, not being OS stock, might be contributing to some engine run issues, but not sure. If the venturi is too large for instance, that could contribute to an engine run or performance issue.

When I have a new model/engine combination, I don't start with a particular ground rpm. It is actually the last thing I just document for reference after I get the engine/model setup running how I like.

I have run all the various size OS LA engines. They all have worked great for me totally stock. I use the stock tube muffler with the internal baffle installed. And I run muffler pressure on the LA's.

I always start with a 4-pitch prop on a new model, usually an APC sport prop. And I start with a prop diameter that suits the model size. In the case of the Brodak P40 ARF with 46LA, I would start with a 11-4.

The LA engines like to run fast for best performance. I personally don't set the needle to try to get a 4-2-4 break on the LA's. Just like the OS owner's manual says, I find peak rpm on the ground (i.e.: if I go any leaner the speed starts to fall off). Then, just as the owner's manual says, I open (richen) maybe 30 deg or so just when I notice the rpm to just start to decrease a little. OS calls this the 'optimum' engine speed. Then I fly the model.

If the model is flying too fast for my liking, I might try a 3-pitch prop. If too slow, a 5-pitch, etc. Totally trial and error. I even try different manufacturers props. MAS, BYO, etc. until I find the prop that flies the model best. In the case of my P40, I ended up liking the MAS 11-4 best.

Then to adjust lap speed, I might play with the line length. (I might also tweak the rpm just a bit, but not more than maybe 200 rpm either way. I still like a relatively fast 2-cycle on the LA's where they seem to perform best based on my experience.

When trying different props, I still set the needle again to 30 deg or so off of peak rpm on the LA's. The ground rpm will be different for each prop I try.

Once I finalize the engine/prop combination I finally document the ground rpm so next time I fly I know were to set the needle.

There are always some tweaks on the above, but this is the basic procedure I have used on any new model/engine combination. It has worked well for me to date.

Also BTW, I run a 46LA on my heavy Vector 40 (62 oz). After numerous prop tries, I ended up with a wood BYO 12-3 which seems to pull the model best. The BYO design is a very wide prop. And I fly the model on 64' lines. My ground rpm is right at 10,000.

[Paul Taylor]

You are lucky to have a TT 11x4.5. That was the prop for a LA 46 and should work fine on the P40.
You could launch around 9800 just as it starts to crackle.
If you have not run the engine with wrong mix or screaming lean you might just have some lose screws on the motor or muffler. If you did scorch the motor don’t discard it. Just look for a P&L drop it in a go.

Check all your screws first.

[Brent Williams]

I ran that Thunder Tiger 11x4.5 on my LA46 and it was a magical prop!  We launched it around 10,200 RPM and it would settle into a fast 4 cycle in the air.  Very consistent and reliable setup.  Regular OS needle valve with a bit of fuel tubing to seal the needle, and the smaller OS .257/6.5mm venturi.  10/11-11 fuel. 63ft lines total (c-c).  Lap times were around 5.25 if I recall correctly.  Loved that setup.  Burned up many gallons of fuel with that combo. 

[kevin king]

Kafin, What kind of fuel are you running? How much castor oil is in your fuel? Some off the shelf fuels only contain 16%. Maybe that's the cause of your black exhaust residue. 

[Peter in Fairfax, VA]

Kafin,

How broken in is the engine?

thanks,

Peter

[Steve Dwyer]

I’d go with the APC 11-4 or 11-5 if you need more speed.  However the black residue is corrosion in the engine and says it’s about done.  Common in humid climates or near indoor humidifiers very long.  Ask me how I know….

Dave

Dave,

I have often wondered about the black residue but never considered internal corrosion the cause.  I run OS FPs and LAs and don't see the black residue but I do see it with my OS Max-S 35s. I have used both 5% nitro with 28% castor and 10% nitro with a 23% 50/50 synthetic/castor blend and see the darkening exhaust using each fuel. I also see it at different NVA settings, different plugs and with low and higher pitch props. Having inspected these Max -S engines, none have "internal corrosion". They show minimal wear and appear to have good compression. I wonder if the blackened residue is a characteristic of the style engine porting and "cooking of the oil" or blow by once the engine heats up?  I'm very curious if someone here can recall using new engines back in the day and if they all created this condition early on. This would be key and might define the cause being engine wear even thou not visible but beyond acceptable tolerances. Perhaps a new sleave and piston would help resolve the mystery, if I could find these items.

Steve
 

[Colin McRae]

Dave,

I have often wondered about the black residue but never considered internal corrosion the cause.  I run OS FPs and LAs and don't see the black residue but I do see it with my OS Max-S 35s. I have used both 5% nitro with 28% castor and 10% nitro with a 23% 50/50 synthetic/castor blend and see the darkening exhaust using each fuel. I also see it at different NVA settings, different plugs and with low and higher pitch props. Having inspected these Max -S engines, none have "internal corrosion". They show minimal wear and appear to have good compression. I wonder if the blackened residue is a characteristic of the style engine porting and "cooking of the oil" or blow by once the engine heats up?  I'm very curious if someone here can recall using new engines back in the day and if they all created this condition early on. This would be key and might define the cause being engine wear even thou not visible but beyond acceptable tolerances. Perhaps a new sleave and piston would help resolve the mystery, if I could find these items.

Steve

Steve

I see some of the same black residue on my OS Max-s 30. But not on any of my OS LA's

I have been running 10% nitro / 28% (50/50) oil on the Max-s so the engine should be getting plenty of lube. Engine continues to be strong w/ good compression. BTW, I'm going to lower the oil to 25% per the OS owner's manual.

I also would be interested in what others say is the primary reason for the dark oily residue.

[Dave_Trible]

Dave,

I have often wondered about the black residue but never considered internal corrosion the cause.  I run OS FPs and LAs and don't see the black residue but I do see it with my OS Max-S 35s. I have used both 5% nitro with 28% castor and 10% nitro with a 23% 50/50 synthetic/castor blend and see the darkening exhaust using each fuel. I also see it at different NVA settings, different plugs and with low and higher pitch props. Having inspected these Max -S engines, none have "internal corrosion". They show minimal wear and appear to have good compression. I wonder if the blackened residue is a characteristic of the style engine porting and "cooking of the oil" or blow by once the engine heats up?  I'm very curious if someone here can recall using new engines back in the day and if they all created this condition early on. This would be key and might define the cause being engine wear even thou not visible but beyond acceptable tolerances. Perhaps a new sleave and piston would help resolve the mystery, if I could find these items.

Steve

Some engines are more prone to it than others which I believe is the metallurgy involved.  Fox engines can be especially bad about it,  and McCoys seem impervious.  OS's and Enya fall somewhere in between.   The engine I used this year at VSC,  an OS 35S began purging black just before I made the trip.  I have other engines but had no time or weather to work it out so I just hoped it would get me through.  Well it did get me through Day 1 but got hard to start and hard to set on Day 2.  I have pulled it now and have another 35S in the plane.  I think the corrosion begins either on the shaft or bronze shaft bushing and in the piston wrist pin holes mostly and the residue is gritty.  This then becomes a slurry of grit that wrecks the engine very quickly.  It wouldn't take very much.    I have had a few cases where an engine has cleared itself of the black crud in a few runs then kept going without any real problems but usually it works the other way.  In no way do I believe you are burning the oil-it doesn't get that hot and especially when you run them oil rich , slow and cool as I do.  I also had most of my engine collection (before I moved) in the same room with a large humidifier over the winter.  As I started packing engines to move and going through them one by one I found quite a few froze up and when I got some of them loosened and test run I discovered a good number ruined due to corrosion.  My suggestion in general is OFTEN oil up and flip through any engines you aren't using for a while to keep them in good shape.  I trashed maybe 12 -15 engines that beat me to the punch.

[kevin king]

Kafin, are you using an electric starter on the engine?

[Motorman]

Black oil is usually from the con rod rubbing the back plate or bushings gone south. Make sure you have the steel washer behind the drive washer. Also, on some high mileage LA46 the sleeve plating can be worn through to the brass in places.

You'll be hard pressed to find a better 2 blade plastic prop than the TT 11x4.5.

MM

[Steve Dwyer]

I have noticed wear on the back plates of the Max-S engines. I always make sure the front bearing washer is in place. Has anyone ever tried adding additional backplate gaskets? There's an extensive amount of discussion on the Max-S engines here from back in the day, I'm curious, however, why this topic hasn't been covered more.  Why would a Thunder Tiger prop make any difference other than it has a thinner profile?

Steve

[Al Ferraro]

  Looks like you are running the stock OS muffler which is very restrictive. I would run a 5/16 drill all the way through the exhaust to let engine breathe better or get a Dinger muffler. As far as props go, I would use the APC 11.5X4. I tried the TT 11x4.5 on my LA 46 powered Vector and on a calm day it works ok, but when the wind starts blowing the APC is the clear winner.
Al

[Paul Taylor]

I have noticed wear on the back plates of the Max-S engines. I always make sure the front bearing washer is in place. Has anyone ever tried adding additional backplate gaskets? There's an extensive amount of discussion on the Max-S engines here from back in the day, I'm curious, however, why this topic hasn't been covered more.  Why would a Thunder Tiger prop make any difference other than it has a thinner profile?

Steve

The TT prop for the LA 46 was the magic prop. I never question magic. 🤣

Sort of like the old Rev Ups were the prop to swing. 👍🏼

[Steve Dwyer]

  Looks like you are running the stock OS muffler which is very restrictive. I would run a 5/16 drill all the way through the exhaust to let engine breathe better or get a Dinger muffler. As far as props go, I would use the APC 11.5X4. I tried the TT 11x4.5 on my LA 46 powered Vector and on a calm day it works ok, but when the wind starts blowing the APC is the clear winner.
Al

Al,

All the mufflers I have on my Max S engines are the strap around the head style with a approx. a 5/16" diameter outlet. Can you better describe where exactly you are recommending a 5/16 hole be drilled. I do believe I read somewhere here some mufflers had a much larger outlet and the engine ran better.

Steve

Steve

[Dave_Trible]

Al,

All the mufflers I have on my Max S engines are the strap around the head style with a approx. a 5/16" diameter outlet. Can you better describe where exactly you are recommending a 5/16 hole be drilled. I do believe I read somewhere here some mufflers had a much larger outlet and the engine ran better.

Steve

Steve

May be some confusion.  Al was talking about the LA .46 I believe.   We have always used the stock muffler on the FP and LA .40-.46 without issue.  Could be other factors involved .   

Dave

[Steve Dwyer]

OK thanks

[Jake Moon]

Hi Kafin,
I run an LA-46 on a tongue muffler (all holes open) in my Vector 40 with 5% nitro, 20% oil mix and a 12.5 X 4 APC prop. I have tried a couple other fuels (5% nitro/18% oil, 10% nitro/18% oil, and 10% nitro/20% oil) and had either power issues or overheating. I've found that with the heat and extreme humidity in our climates that even seemingly small fuel changes can throw the motor run off.

Before takeoff I set the needle to where the motor is in 2 cycle and just cracking into a 4 cycle every couple seconds. The lap time is around 5.1-5.2.

[Perry Rose]

Any time I've had a dark residue in the exhaust there has been something loose, muffler, engine hold down bolts. I mix my own fuel for the dozen .46's I run half and half oil and 2 % nitro from 1000' msl to sea level year round. APC 11.5 x 4 launch at 9000 rpm 60 to 63 foot lines. Stock venturi and whatever muffler will fit or needed for balance from stock or fox 35 or tongue.

[Al Ferraro]

Al,

All the mufflers I have on my Max S engines are the strap around the head style with a approx. a 5/16" diameter outlet. Can you better describe where exactly you are recommending a 5/16 hole be drilled. I do believe I read somewhere here some mufflers had a much larger outlet and the engine ran better.

Steve

Steve

  The LA 46 muffler has a .270 exhaust pipe outlet hole. What i recommend is to drill out the muffler exhaust outlet pipe all through the pipe with a 5/16 drill to enlarge opening of the pipe to .320.
Al

[Colin McRae]

Any time I've had a dark residue in the exhaust there has been something loose, muffler, engine hold down bolts. I mix my own fuel for the dozen .46's I run half and half oil and 2 % nitro from 1000' msl to sea level year round. APC 11.5 x 4 launch at 9000 rpm 60 to 63 foot lines. Stock venturi and whatever muffler will fit or needed for balance from stock or fox 35 or tongue.

I run muffler pressure on all of my LA's. And I typically re-check the muffler bolts for tightness every few flights.

If running muffler pressure, it is very important to ensure that there are no exhaust leaks (muffler not loose, fuel tank not leaking air, etc.). The needle will be set a bit more closed with pressure compared to no pressure for the same ground rpm. If the muffler becomes loose in the air, or a fuel tank air leak develops, pressure will be reduced or lost, and the engine will go lean.

[Kafin Noe’man]

Dave is probably right, but being the eternal optimist, you might check that big muffler and make sure you have the interface smooth and flat and there isn't a vibration/ loose rub going there that is making the black metal.

EricV

Thanks Eric.
It turned out my muffler being loose.
After I tightened it up, the problem went away.

I really hope that’s the culprit, not the internal parts that are worn out

[Kafin Noe’man]

Just like the OS owner's manual says, I find peak rpm on the ground (i.e.: if I go any leaner the speed starts to fall off). Then, just as the owner's manual says, I open (richen) maybe 30 deg or so just when I notice the rpm to just start to decrease a little. OS calls this the 'optimum' engine speed. Then I fly the model.

Thanks for mentioning this, Colin.
I was trapped to match the suggested ground RPM number for that specific prop on LA46 without finding what will work on my flying location.

[Kafin Noe’man]

You are lucky to have a TT 11x4.5. That was the prop for a LA 46 and should work fine on the P40.
You could launch around 9800 just as it starts to crackle.
If you have not run the engine with wrong mix or screaming lean you might just have some lose screws on the motor or muffler. If you did scorch the motor don’t discard it. Just look for a P&L drop it in a go.

Check all your screws first.

There’s loose screws on the muffler. I was also thinking of putting a gasket in between the motor & muffler, good idea?
I will definitely have to go over to see if there’s any lose screws on the motor as well and try to fly it with 10% nitro fuel.

[Kafin Noe’man]

Kafin, What kind of fuel are you running? How much castor oil is in your fuel? Some off the shelf fuels only contain 16%. Maybe that's the cause of your black exhaust residue.

It’s a local brand fuel with 5% nitro 20% oil (which I suspect this is full synthetic oil).
I might have to try switching to VP Powermaster 10% Nitro 22 oil (50:50)

[Kafin Noe’man]

Kafin,

How broken in is the engine?

thanks,

Peter

Hi Peter,

It’s a secondhand engine I bought  from Bob Brooks.
Not sure how the engine is broken in fully or not.

[Kafin Noe’man]

Hi Kafin,
I run an LA-46 on a tongue muffler (all holes open) in my Vector 40 with 5% nitro, 20% oil mix and a 12.5 X 4 APC prop. I have tried a couple other fuels (5% nitro/18% oil, 10% nitro/18% oil, and 10% nitro/20% oil) and had either power issues or overheating. I've found that with the heat and extreme humidity in our climates that even seemingly small fuel changes can throw the motor run off.

Before takeoff I set the needle to where the motor is in 2 cycle and just cracking into a 4 cycle every couple seconds. The lap time is around 5.1-5.2.

Hi Jake,

Thanks for sharing your thoughts.
Why did you decide to use 5% nitro fuel instead of using the 10%? I thought with the heat we have here it will be better to use 10% nitro.
I’ve been using 5% nitro for the past year but I was thinking to switch to 10% nitro.

[Ken Culbertson]

It’s a local brand fuel with 5% nitro 20% oil (which I suspect this is full synthetic oil).
I might have to try switching to VP Powermaster 10% Nitro 22 oil (50:50)

That is what I ran mine on.  Good fuel.

Ken

[Paul Taylor]

There’s loose screws on the muffler. I was also thinking of putting a gasket in between the motor & muffler, good idea?
I will definitely have to go over to see if there’s any lose screws on the motor as well and try to fly it with 10% nitro fuel.

No gasket should be required. I know the stock muffler comes with Phillips Screws. Don’t remember the size but if you can find hexhead cap screws to replace them they won’t come lose as often.

You should get in a habit of checking all screws and nuts from time to time. Just like real aircraft they require maintenance and inspections. You have a vibrating flying machine. Things vibrating lose is a bad thing. 😉