hyper701

hi, im just wondering what prop to put on my os la 40, its in a trainer and i have never flown b4.
one of the guys at the club here is going to take it up for me this weekend, i hope all goes well CHEERS

fadi

Start by a 10x6

Dr1Driver

A 10 x 6 is too much prop, use a 10 x 4 to limit top speed and create more pull.

Dr.1

Fastsky

I would use a 10-5 Master Airscrew. [8D]

Jim Thomerson

11 x 4 is about right. There is an APC 10 1/2 x 4 1/2 that a lot of CL fliers like.

RCVFR

My Feedback: (7)

I used an APC 11X5 on my 40LA powering a WM Mach I trainer, and it is a terrific combination. Good acceleration, moderate speed and all around good handling. I think you will like that prop.

hogflyer

10 X 5 or 10 X 6 is fine. You don't want too much prop on it or it won't wind up as well. 10 X 6 is pretty much the standard for most .40 size engines.

Hogflyer

fadi

Exactly was I suggested the standard... and then you move from there.
Cheers

piper_chuck

My Feedback: (12)

Staying in the 5 inch pitch range is good for a trainer. As said a couple times, it will allow for slower flight and better acceleration. Given the choice between a 10 or 11 inch diameter, I'd go with 11 to help overcome the drag of the airframe. My choice would be an 11x5, which is within the OS recommendations for this engine. In fact, it's their recommended break-in prop. Once you've soloed and are comfortable flying, you can move to a faster prop, such as the 10x6.

jaka

Hi!
If you fly at sea-level an 11x5 or 11x6 APC is the best prop. 10x6 will work to but not as good , anything smaller than that is no good on a high winged .40 trainer powered by an OS LA .40.
Avoid MA props if you want performance.

Regards!
Jan K

Dr1Driver

fadi,

The "standard" is variable for different engines. The .40 LA is a lower-power engine than, let's say, the late FX or current AX, and won't adequately turn the same props they will. In my experience, a 10 x 6 prop is NOT the prop to use on a .40LA in a trainer.

Use a lower pitch to limit top speed (you don't want a fast trainer), and a larger diameter to create more pull against the weight and drag of most trainers.

As per previously mentioned suggestions:
10 x 4 (might not be enough prop)
11 x 4
11 x 5

Dr.1

britbrat

A reasonable selection of props for a "trainer" & the 40LA would likely include 10-5, 10-6, 10-7, 11-4, & 11-5. However, the question "what prop?", immediately raises the question "what plane"?

Props & engines are a highly variable mix -- it really matters what plane it will be on -- & the term "trainer" is only moderately helpfull. There are big slow draggy trainers & smaller, cleaner, faster trainers -- the best-fit training prop for that 40 LA will be different for each application.

What is the actual airframe it will be wearing?

BobFE

FYI, the reccomended brake in prop for the OS 40LA is the 10x6 prop. I did this at sea level and had no problems. Good power, but not too much.

flyingJ

HELLO ALL, having used this engine for the past 3 years,on a trainer{H9 solosport} and having the book in front of me, "Suggested size is 11x5 (40LA), 11x6 (46LA)." The plane's instruction sheet said for a .40 size engine use a 10x6 or 10x8 prop. With the wheels that came with the plane, if I'd used an 11" prop, I'd of only had 3/4" ground clearance. This is ok on pavement, but not on grass. I used the 10x6 prop changed the wheels to 2 3/4" diameter and had no problems.

piper_chuck

My Feedback: (12)

Not according to page 13 of the current manual for the engine: http://osengines.com/manuals/40-46-65la-manual.pdf

hyper701

the plane i am using is the pheonix model classic, cheers

BobFE

Piper Chuck, I stand corrected, thank you.

B.L.E.

Mild, low rpm engines like the 40 LA can turn the same or even larger props than the high powered engines can. The reason is the exponential nature of props and rpm. Double the rpm that you turn a prop and it takes four times the torque and eight times the horsepower to turn it. An ultra high performance .40 used in pylon racing may turn a prop thats only seven or eight inches in diameter....at speeds up to 28,000 rpm. These engines are not lacking in "torque", it just takes more torque to turn an eight inch prop at this rpm than it does to turn a 11x6 at 11,000 rpm. Take the racing prop off of a Nelson .40 and put it on a small electric motor used on indoor foamies and it will turn about 7000 rpm or so while drawing about 100 to 150 watts of power from the battery, while making enough thrust to fly a 12 ounce foamy. RPM makes a huge difference in the power needed to turn a prop. Take a look at the huge props used for rubber band powered planes. Twisted rubber bands aren't very powerful but it doesn't take much power to turn a huge prop slowly.

stallspeed

[:-] Put an APC 11-5 on it and you will be loving it. It will give decent top speed, yet it will allow your plane to slow down for an easy landing- the "5" pitch will act as a break to slow the aircraft down when you throttle down the engine. Any high wing 40 size plane should be fine. I recommend the Sig LT-25, its actually the size of most 40 planes but very light lazer cut kit top notch flyer! Nuff said.

hyper701

ok, i think i will go the 11x5, cheers

checkmate91

Good choice

B.L.E.

I used mostly APC 11x5 props on the older OS .40 FP, the inexpensive bushing bearing engine that preceded the .40LA. Excellent climb, reasonable top speed, and the engines never overheated.

hillbillyexpress

take it from a fellow rookie with lots of sticktime now. 10x6

hyper701

dam it................. all they had was a 11x6, so i got it anyway

fadi

11x6 is probably too much. Just try it and let us know what you think