Well, rain broke today so I hopped down to the field, and put the 12x4 on my new ax, and leaned out the lowend. Plane no longer feels funny What a differance a prop can make. I just love the 12x4 on my trainer. Imho the perfect prop for the plane. Slows it down nice, and really good pull. Very nice. Unfortuantly I am now short a 12x4 prop 2 good flights, then I went to take off, and my nose gear slipped. Got pretty crooked on the runway, and idled back to abort. Unfortantly to much airspeed already and I went airborn, then didn't think fast enough to do what I should have done, powered back up and gone, and driffed it down into some weeds. No damage but a broken prop. Unfortuantly my only 12x4. Looks like I got a trip to the hobby shop topmorow morning before the field.
-John

I agree about the right prop for the plane/engine. I acquired a plane that was a scratch build of a Fly Baby. It had a 62" wingspan, and weighed about 7#'s, so I figured it would require a .60 to .65, right? That is what went in it with a 13x6. I had to fly it into the ground at idle to get it to land. I then tried a 14x3w APC prop. It is a low pitch "W"ide blade to keep a load on the engine. What a difference it made! I could actually land the plane at idle...
I came to find out a year after I got the plane that it was made for a .46 2stroke. (I liked the extra power, 60 degree clims was cool, but not realistic).

I have heard of other people having problems landing on mains only, can't seem to 3-point a landing.

Here is the key:

Stall speed = X
Prop pull must be less than X at idle.

Here is a link to a simple spreadsheet in Excel that I created.
It'll help in several aspects off your engine/prop/weight problems:
http://dutchessrc.com/tools/tool1.xls

I hope this helps....

Sorry, it was a 14x4w, not a 14x3w

striderjg, So what prop did you have on before you switched to the 12-4? I use a 12-5 APC for the 46Ax and think it works pretty well. [8D]

I tried to find APC 12 x 5's a while back and was unsuccessful. Maybe they are making them now. I'll look again.

Money to try some different props is money well spent. Don't throw the poor ones away. They may be just what you need on another engine or airplane.

Was spinning a 11x6. It's what I started with on my fx, then I switched to a 12x4, then the fx died and I started my new ax off with the 11x6 to break it in. I'm just amazed at how differantly it flys. It's like a differant plane with the 12x4. I mean everything feels differant about it. Not just landings but turns everything. Really is amazing
-John

Sorry, I meant an 11-5 prop. An APC 12-5 would be too much for a 46. I will try on of those 12-4 props just to see what the fuss is about. [8D]

G'day Mate, a 12x5 APC is not too much for an 46AX, we run APC 12x6 on a Skyraider Mk 1 & it flies beautifully, plenty of power.

i found this out over the week end i think as I've just purchased a used cessna 172 trainer fitted with a sc 46 with a Ram 11x7 prop. it takes a while to get it into the air and my first crash was caused by a stalled turn while trying to get some height yet the throttle was wide open i know it was my first flight but i didn't think it would all end so quickly it did seem as if the plane was under powered after reading this article am i correct in thinking it was over propped after I've repaired the damage would the two props mentioned be OK IE the 12x4 or 11x6 prop Thanks for ya help Ady

alan0899, exactly which model do you have and how much does it weigh? I would guess that your Skyraider is one of the smaller light models. If not, I may have to do some more testing. From taking tach readings and watching performance I found with a 11" prop on a 46 size engine, the prop better be turning at least 12,000 rpm or you will be lucky to get off our grass run way. This is with planes that are rated for 40\46 size engines. Do you know what rpm your are getting with your combo?? [8D]

well i got all the bits to repair it now i got both props to try the 11x5 and 12x4 see what happens on my next trip to the field think ill go when theres some one there to see how well it flys instead of hitting hard objects again

All,

Glad I found this discussion - my experience is only one-year and have flown only the OS 46AX engine. On my trainer and now on my US 40, I have always used a 11x6 prop. Just for testing, I threw a 12x4 apc on my US 40 last week and I love it. I have a Tower muffler on the ax and I tached 14,800, I then richened five clicks for flying. My concern - the engine is running hotter with the 12x4 than the 11x6. Is the 12x4 really too much prop or should I richen it more for cooling? Appreciate any advice! BTW - I have a WM Mach II with a OS 46ax and 11x6 prop and it hauls ... I'm frequently asked what kind of engine I have.

Its nice to see some real world numbers taken from a tach. The statement made by a lot of flyers about their engine when they say "it screams!" doesn't really mean anything.

Yup, real world numbers are great. Any time I'm looking for numbers for an engine, I visit this forum: http://www.rcuniverse.com/forum/forumid_173/tt.htm . There is a remarkable amount of information out there. I'd encourage anyone who has done some comparative runs to post their results.