General control line discussion > Open Forum

My P40 Maiden Flight

(1/7) > >>

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:

--- Quote from: Dave_Trible on May 04, 2024, 10:19:44 AM ---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

--- End quote ---

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.

Navigation

[0] Message Index

[#] Next page