ORIGINAL: asmund
If your plane is about 2.3-2.5 kilos (or even some more too) then your engine should have no problems climbing of of a hover with the 12.25-3.75 prop, and most every other prop to. Is your engine tuned properly? what rpm`s are you getting?? A healthy 50 size engine should manage to pull 4-4.5 kilos and will be more than enough to pull out of hover.
What?
Your average .46-.50 will really struggle to pull a 3Kg model out of a hover with any real authority and I've yet to see one that will even hover a 4-4.5Kg plane at all.
My TT46Pro engines will spin an APC 12x4 at a shade under 14K (with 5% nitro fuel, a Tower/GMS muffler and and 12% hi-performance oil) which provides *good* pull-out on anything that weighs 5lbs (2.25Kgs) or less. An ASP52 (one of the most powerful engines in this class) will still struggle to give decent pull-out on any airframe that weighs more than about 5.5lbs (2.5Kgs)
My own favourite synthetic prop for 3-D is the APC 12-4, or I use wooden 12-4 and 13-4`s on my 50 size 3-D engines
Yep, the APC 12x4 is (IMHO) the best 3D prop if you want plastic but I fly nothing but *good-quality* wood props now. They rev-up quicker, provide more thrust, are cheaper and just as tough as those frail APC 12x4s.
Anyone who's trying to do 3D with a .46-.52 on an airframe that weighs much more than 5lbs really needs to buy themselves a profile that weighs in at 4.5lbs all-up and discover what *real* 3D flying is all about. The "fun" factor will go up by a factor of ten or more.
Good grief, my Mojo60 profile weighs 5.5lbs (2.5Kgs) and has a Saito 100 up front, spinning a 15x6 prop at 9.800 RPMs. Now *that's* good power and vertical :-)