3D/acro props for 46AX
 

I may be putting a 46AX on a Extra for which 46 is the minimum size engine. I saw a suggestion that a APC 12.25x3.75 would be a good prop for that combination. The low pitch surprised me especially as OS recommends 12x6-7 for the 46AX at the bigger end.

I'm not thinking the guy is "wrong" necessarily, but maybe he is just better at running such an engine at extremes because he can better hear if there's a problem.

So I'm wondering is it safe for me (who does not have a great ear for engines) to use something like a APC 12.25x3.75 on a 46AX? AND if it's alright to go with that size, could I even go a little more extreme and try something like 13x4 even? Or is that going too far with a 46AX?

But at the least, if APC 12.25x3.75 on 46AX sounds alright for a slightly engine-challenged person to play with, then I'll include them in my soon upcoming order (can't find that size any where else). I'm a little clumsy with tuning...

Thanks

edit: Oops, I hope using this section was ok. But relates to an unusual prop size specifically for 3D/acro so...

RE: 3D/acro props for 46AX
 

Yes, the 12.25x3.75 would be just right for that engine. The 13x4 would be too big but is a good one for the 55AX engine.

RE: 3D/acro props for 46AX
 

IMHO, it depends on whether the os 46 ax is new or run in very well. when new, my 46ax would not transition very well with the 12.25 prop. After running in it was ok. It also depends on the nitro that you use and the head shims that you use. I found it just easier to use a 12 X 4 prop which was ok, but I also like an 11 X 5 on this engine. For me, the 11 X 5 spins up very quickly and generates enough thrust. It also revs a little high, but I've never had any problems with it.

RE: 3D/acro props for 46AX
 

Ok thanks guys. So I'll order the 12.25 and 12x4 I guess as well. Try both.

The 46AX is new, but I'll be running it on another plane with probably a 11x6 for about a month or so (initial break-in will be with 10x5 I guess). Only after that I'll put it on the GP Extra.

With the GP Extra I'll be more interested in climb and maneuverability than speed, so I'll experiment with the larger diameter props.

Thanks, clears that up. I can now focus on the remaining decisions related to the order.

Cheers

edit: It will have a 4 stroke on it later, but I'll make do with the 46AX for a while first.

RE: 3D/acro props for 46AX
 

The APC 12.25x3.75 is a very wide and heavy prop. Much different than the 12x4. I found that it spools up very slowly when you throttle up. I found this to be true (at least not to my liking) on a well broken in motor unlike what isaacslaw said. I gave them all away. The APC 12x4 is my favorite 3d prop for this motor but have run 11x4's as well. On non-3d stuff, I prefer the 11x5.

Mike

RE: 3D/acro props for 46AX
 

I have an OS46FXi and an older OS50FSR. Have tried both engines in different planes, both with the APC 12.25x3.75 and with a Xoar 12x4 wood. Both engines would spin the props within about 500 rpm, with the 12x4 wood getting the edge. The 50 is slightly stronger on both props. However, I really noticed the weight of the APC, as both engines were slow to spool with the APC, and much snappier with the wood prop. If you're looking for quick throttle response, stick with the wood on these engines. However, I must say, I'm using the APC on the 46 in a Phoenix Models Super Decathlon now, and it works great for that place in general sport aerobatics.

RE: 3D/acro props for 46AX
 

Thanks for inputs.

Was planning on going with APC on this, but not if it cuts the responsiveness. I've never actually used APC before except on electric. I'll still get the APC 12.25x3.75 to try it and one APC 12x4 in case the responsiveness is good enough for my use.

But now that this came up I think, I'll get a stock of woods in the big order. Was thinking of not only 12x4 but also 12x5.

I know it's not a sport prop, but what do you guys think of those "pre-balanced" Zingers for a 3D class plane? With wood props I always feel like I'm on the verge of weakening it trying to get the friggin thing balanced (another task I'm clumsy with). And the "pre-balanced" Zingers are really close if not balanced to start with... they claim they balance them twice before shipping them out.

Wood props just look nice too :)

Cheers

RE: 3D/acro props for 46AX
 

I have used the 12.25 prop for 5 years with a 46FX, tower muffler and wildcat 20/20, NEVER deadstick, awesome power and very nice transitions with this muffler, Highly recomended!

RE: 3D/acro props for 46AX
 

That plane tracks very well, I would not recommend putting a 3D prop on it. Go with a 11x5 and do some nice slow rolls down the runway.

Edit: that plane is a little heavy and will benifit from a little extra speed

RE: 3D/acro props for 46AX
 

Well I did order a stock of 12x4 props (APC, Zinger, Zinger Pro) a couple days ago. Don't recall if I have a 11x5 in my prop box, but I have some unused 11x6's. So I'll try those too.

I figured this extra would not fly slow as well as other 3D planes, but as long as it's reasonable. So with the 12x4, I would have a pretty high minimum throttle. I could live with that if there is still at least some head room left in the hi end of the throttle range. Are you saying that I would be just under max just to fly normally? I have a 12x5 prop as well. I think 46AX specs say you can use up to 12x7 on the 46AX.

Thanks for the input

RE: 3D/acro props for 46AX
 

Don't really know what OS was thinking when they recommended a 12x5. I think the 11x6 will work well. 12x4 should fly it but it will be a little uncomfortable.

RE: 3D/acro props for 46AX
 

I'll try 11x6 first and then try 12x4 later (also the apc 12.25x3.75). Hopefully the overall handling is ok with those, because the 12" diameters should be much better for stuff like harriers.

RE: 3D/acro props for 46AX
 

I've been flying pattern with a 12x5 on a 46AX.