LA 46 on P40 Prop Size & Ground Clearance?

[Kafin Noe’man]

I’m currently finishing my Brodak P40 ARF. It will be a box stock built.

I will put an OS LA-46 and on a 60 ft lines. Fuel is 5% Nitro.
What would be the safe starting prop size?

The other thing, after doing some research here, it seems that APC 12.25x3.75 is the perfect combination, however since I’m building it box stock, will it have enough ground clearance?
Because the grass on my flying field isn’t mowed regularly so I often have to deal with tall grass.

Thus, what’s the safe diameter size in order to have safe ground clearance?

The other sizes that often get mentioned are APC 12x4, APC 11.5x4 and Thunder Tiger 11x4.5

And what is your opinion on APC 11x4 or 11x5?

The props that I could find in my place are:
APC 12.25x3.75
APC 12x4
APC 11x5
JXF 11x5
APC 11x4

Looking forward to hearing more from you


Best,
Kafin

[Carl Cisneros]

on my P40, I am using a XOAR 12-4
Has good clearance.
Another one is the APC 11-5/12-4 or the 12.25-3.75 prop.
Running either 5 or 10% nitro depending on the time of year. (cooler/warm/hot temps outside)

Carl

[Leonard Bourel]

Hi Kafine I have had good success with the 11-5 props on the LA 46 with a 4-2-4 run characteristic If you want more of a pipe type run go to a 12 inch with a flatter pitch maybe 3.75 or 4 pitch I also like the thunder tiger 11-4.5 prop for the LA 46. I hope that P 40 works well for you It is a great profile LEN

[jerry v]

Kafin,
My P-40 originally was flying on OS.40 FP with 10x6 prop. The stock landing gear was good enough for ground clearance. Stock ( or kit box) hardware landing gear wire is 3 mm diameter and was the weakest link to bend during tail heavy landings. I prefer to bend wire back to shape compare to fix the ripped off landing gear blocks. FP-40 and LA-46 have the same footprint and mounting hole locations. I just swapped the engines. I used APC 12x4 pop and this was too big for ground clearance. For test flights I replaced stock wheels with Du-Bro vintage wheels. Wheels are 3 3/4 diameter, looking funny, but work on the rough field. By advertising those wheels are 1/8 scale vintage wheels, supposed to be 3 1/2 inch diameter. Real size is 3.7 inches or 94 mm diameter. I added uniflow tube to the original Brodak 4 oz deep vee tank for testing. It feels like 4 oz is not enough fuel for LA-.46. The ARF fuselage is bent into the circle, I need to put more washers under the engine legs. Flown on 60 ft and 62 ft lines.

Jerry

[Colin McRae]

I'm running a MAS 11-4 on an Evolution 36NT engine which is as powerful as an OS 46LA. One thing to note is that I use aluminum profile-mounted landing gear (not the kit wing-mounted gear) because our flying field is grass/dirt and somewhat bumpy and not friendly to wing-mounted gear unless they are reinforced.

If it were me, I would keep the pitch at 4, and experiment with different diameters. Also, use whatever prop/engine-tune combination flies best. If a ground clearance is an issue, use larger diameter wheels. I would not use an inferior size prop just to clear the ground. Use whatever prop allows the model to fly how you want it to fly.

[Ken Culbertson]

You are going to be cramped at 4oz.  I competed with the LA46 for a couple of years, and you are likely to need 4 1/2 at times.  I used a 6oz Clunk and measured the fuel with a syringe.  There were days when it took 5oz to give me enough extra laps for go-arounds and landing setup.  I was never a fan of the high RPM low pitch props setup.  I used 11x5.5 or 11x6 on a much larger/heavier plane running a fast 4-2-4 where the 2 was really a very fast four similar to what you would get with a pipe.  Rich uses more fuel.  Lean you *might* make it on 4oz using a lower pitch.  Additionally, as long as we are talking fuel consumption, get out your MonoKote iron and smooth out your LE.  That alone is probably a 1/4oz or more of wasted fuel.

As to clearance, there is always the old standby - bigger wheels.  I rarely fly on grass but when I build a plane, I always bend two sets to landing gear wire for both surfaces.

Ken

by the way, posting your picture upside down does not count as level inverted flight. 

[Dan McEntee]

    Try them all in a flight test! What is good and works for Peter might not work for Paul! The best way to tell how a prop will work is to fly it. in YOUR airplane at YOUR location.
  Type at you later,
   Dan McEntee

[jerry v]