O.S. LA 46 engines

[Dudley Lang]

I am just returning to control line flying.  I have not flown since the 60's.  My question may have already been addressed, but I don't know.  I have read that some pilots are using the LA engines in stock form and that they are running 4 inch pitch to slow them down and also not leaning them out on the ground.   I grew up with the Fox 35 and the 4-2-4 cycle.  I have seem advertisers that modify  and stunt tune the LA  to run the traditional 4-2-4.
 What is the most popular option and why.  It would be cheaper not to pay for the modifications if the lower pitch works OK for stunt flying.

[Randy Powell]

I run a 46LA that is bone stock (except for an extra head gasket and bit smaller venturi than stock) in a 4-2-4 run and it goes great.

[Greg L Bahrman]

Dudley,
If you do a search here for the L.A. 46 you will find a lot of good info. The L.A. 46 can be run however you like your run. I was using an APC 11 1/2 x 4 prop and it worked good. Then Mark Scarborough suggested I try an APC 12 1/4 x 3 3/4 and for me it works even better. My motor does not do the traditional 2-4 break like a Fox 35 but it definitly has a break. Mine runs mostly in the 4 stroke mode with easy breaks in the verticals. Others like their run without the break and I have seen some excellent flights that way. I don't have any experience with modified L.A. 46's but most of the people here on the forum and myself included run the LA 46 basicly stock. I did add one head gasket a different venturi and a ST needle.

[Balsa Butcher]

And if you are looking for possible kits to build consider any of the Brodak kits primarily as they have excellent illustrated assembly instructions in booklet form. Many are suitable for the LA 46 engine. The Vector 40 comes to mind as a particularly good choice.

[john e. holliday]

Don't also for get that Eric at RSM Dist. has some great kits for this size engine.  I am running mine stock in P-39.  Runs great when I remember to clean the filter.  HAVE A HAPPY NEW YEAR

[ray copeland]

Anyone know if the Tower .46 metal backplate for $3.99 fits the LA .46?

[Paul Taylor]

Ray,
I think it does. There was also a guy making them for all the LA engines. Can't remember who, so a quick search might find him.

[Ed Keller]

Back plates are made by Curtis Shipp, here in Dixie(Birmingham, Ala.)  Ed

[Mark Scarborough]

As stated by Greg, ( thanks by the way)
The LA 46 runs Great with a 12.25 x 3.75 APC, .275 venturi, ST needle assembly, GMA 10 % 22% fuel. Launch about 9800 rpm. I have flown this on everything from a Vector,a scratch built Oriental,  to a Profile Brodak P-40 that ended up a portly, obese 58 oz, and its been great.
One thing that we found, ( Pat Johnston and I) Is that if you dont load the engine with enough prop, it really gets sensitive to needle setting. It will greatly vary the fuel burn with minor tweaks of the needle. IOW, it can go fro to rich to to lean with very small adjustments. I have had minute and a half overuns, run out of fuel in the clover or sooner, and everything in between. The only variations in these runs would be a needle setting of a hundred rpm. This was with 11x4, 11x5, 11.5 x 4 props. It just wants to have the load on it for some reason. WQhen we went to the 12.25 APC or a wooden clone of the same size , blade thickness, and area, This sensitivity went totally away. Dont understand it but I know it is true in MY experiences.

[Dave Gardner]

For starters, the Tower 46 backplate is NOT the same as the LA 46.  It's more like the larger case OS engines, but I can't verify that.  If you can find them, the Tower 40 backplate is a correct fit, same as an FP 35-40 backplate.

The ones that Curtis Shipp makes are real gems, but make sure your backplate gasket is in good shape.  I think you can still get the LA 40-46 gasket sets from Tower.

That information from Mark Scarborough (and Pat Johnston) is very good.  The larger prop with a relatively small venturi seems to give a steady engine run and LOTS of pulling power!  I have an LA 46 in my Nakke, and the bigger prop really gives this 54 oz plane some flying authority!

Dave G.

[Bob Kruger]

As stated by Greg, ( thanks by the way)
The LA 46 runs Great with a 12.25 x 3.75 APC, .275 venturi, ST needle assembly, GMA 10 % 22% fuel. Launch about 9800 rpm. I have flown this on everything from a Vector,a scratch built Oriental,  to a Profile Brodak P-40 that ended up a portly, obese 58 oz, and its been great.
One thing that we found, ( Pat Johnston and I) Is that if you dont load the engine with enough prop, it really gets sensitive to needle setting. It will greatly vary the fuel burn with minor tweaks of the needle. IOW, it can go fro to rich to to lean with very small adjustments. I have had minute and a half overuns, run out of fuel in the clover or sooner, and everything in between. The only variations in these runs would be a needle setting of a hundred rpm. This was with 11x4, 11x5, 11.5 x 4 props. It just wants to have the load on it for some reason. WQhen we went to the 12.25 APC or a wooden clone of the same size , blade thickness, and area, This sensitivity went totally away. Dont understand it but I know it is true in MY experiences.

Mark;

Just to verify, by you (and Pat J.) are using the 12.25 X 3.75 APC two blade at full length, not trimmed back a little.  Is this correct?

Just curious, but what is the "wooden clone" of the 12.25 X 3.75 APC?

V/r

Bob Kruger

[Mark Scarborough]

Yes we use the box xstock 12.25 x 3.75 prop.

Pat and I both love wood props. He has corrupted me BADLY, I wont tell you how many boxes of wooden props I have on my  bench, there are lots. All of which,( except the XOAR props) are "kits" from which we massage and rework them. TO replicalte, or clone, the 12.25 x 3.75, Pat and I have carved a wood prop to match the APC . The wood prop is significantly lighter than the APC and still performs the same. I start with something like the zinger pro 14x5, first I bolt the APC onto the wood prop. Then I match the blade outline shape. seperate the two. AFter that I match the back of the blades pitch angles using a Prather pitch gauge. AFter that its a matter of reworking the airfoil portion of the blade, ( the top side) This generally involves a great deal of sanding to remove LOTS of wood, thinning the blade to the same thickness as the APC. In my experience, blade thckness and insuring the high point of the airfoil is in the right place is critical. As is the sharp leading and trailing edge.
I flew with a wood clone of the APC on my Oriental, because the APC was causing my all kinds of wiggley tail syndromes. ( what do you expect witha .46 and a 12 inch prop on an 45 oz Oriental right!)
the wood clone gave me the same traction as the APC without all the wiggle giggles in corners.

[Bob Kruger]

Yes we use the box xstock 12.25 x 3.75 prop.

Pat and I both love wood props. He has corrupted me BADLY, I wont tell you how many boxes of wooden props I have on my  bench, there are lots. All of which,( except the XOAR props) are "kits" from which we massage and rework them. TO replicalte, or clone, the 12.25 x 3.75, Pat and I have carved a wood prop to match the APC . The wood prop is significantly lighter than the APC and still performs the same. I start with something like the zinger pro 14x5, first I bolt the APC onto the wood prop. Then I match the blade outline shape. seperate the two. AFter that I match the back of the blades pitch angles using a Prather pitch gauge. AFter that its a matter of reworking the airfoil portion of the blade, ( the top side) This generally involves a great deal of sanding to remove LOTS of wood, thinning the blade to the same thickness as the APC. In my experience, blade thckness and insuring the high point of the airfoil is in the right place is critical. As is the sharp leading and trailing edge.
I flew with a wood clone of the APC on my Oriental, because the APC was causing my all kinds of wiggley tail syndromes. ( what do you expect witha .46 and a 12 inch prop on an 45 oz Oriental right!)
the wood clone gave me the same traction as the APC without all the wiggle giggles in corners.

Mark;

Many thanks for the detailed explanation. 

V/r

Bob Kruger

[Geoff Goodworth]

If Curtis can't supply for any reason, Thunder Tiger 4 U can supply the GP 40 backplate and gaskets.

Cheers, Geoff

[Bootlegger]

  Randy Powell what size venturi are you running in your os 46 and what needle assy.
 Mine came with the os 282 venturi ans I am runnin the st needle set up, with T/bolt plug three head gaskets and Power master fuel 5-22 w/extra castor, turning a Thunder Tigre 11x4.5 prop.
  Need a little less power and mote fuel economy..
  Thanks a lot, Gil