Well I just finished converting a 20cc weed eater brand weed wacker to r/c and am wondering what prop will work best? I am looking for a prop that will be good for sport flying and give good climbing power. This is my first gas r/c airplane engine so all suggestions are welcome.

Hi, We need to know what plane you have it on and the weight. Tte type air foil ( lifting or symetrical) and wing area would be nice also. A 15x8,15x10 or 16x6 or maybe a 16x8, but for best results the prop should be matched to the plane and engine.

Dave

Don't have a plane yet bu I am gonna make a big pink foam plane that looks like a high wing trainer. How big should the WS be and how much wing area should it have? I don't know. It will have a flat bottom constant chord wing with horner wing tips. It will sorta be like a STOL so should it have a reduction unit on it. I can make one but what should the ratio be. I want to keep the air speed down and have a lot of static thrust for taking off on short bumpy runways. Is 8 to 10 lbs a close guess to the AUW ( this is the first giant scale plane Ive built).

Hi Joe,
With a clark Y flat bottom airfoil and a wing around 24oz. per square foot it should do what you want. Around 80" span and 65" long. This will give around 11 to 1200 square inches area and about seven square feet area. Eleven pounds would give a 24oz. to the square wing loading. The Horizontal stab assembly and elevator need to be about 25% of effective wing area. Ailerons need to be generious, about 2 1/2". Use large wheels (4-5") and a shallow angle of attack on the ground. The engine with a reduction unit would weight as much as a 33cc Homelite chain saw engine and produce much much less power. STOL air craft are usually over powered. The stock Weedy might spin a 18x6 or 20x6 on a reducer at 1.5 to 1. Flaparons are good for this if your radio supports it. This plane would fly ok without the reducer on a grass field. The idea is to keep the wing loading fairly low. Balsa USA makes a very popular WW1 monoplane Eindecker with a 80" wing that has been very sucessful with the 20 to 25cc conversions. Plans are available sepparatly. Good Luck.

Dave

A master airscrew 15x8 fly's my sig fourstar perfect. A 25CC weed eater engine

I would say a 14 x 8 APC prop would be the best for that engine, but it pays to experiment.

AV8TOR

I would agree with AV8TOR , I have an electric cub that has a belt drive reduction set up, evryone in my club said try this and that size, It amazed everyone that It flys great and goes off the ground, loops and almost hovers with an 11x10 ,yes awsome pitch 10

will a 14x8 master airscrew prop too small for a 25cc homelite? or its just in the range? i have a 15x13 2 blade apc and a 15x12 4blade apc and the motor doesnt sound right, like it cant really handle the prop size and pitch. will this 14x8 be able to make this motor run more effecient? this will be for an airboat
thanks!

your 15s have too much pitch ,these engines are happy with a 16x8 or 15x8

yes too much pitch is my problem. but its too hard to find props here. i did found this 14x8 and i already bought it. just worried if i might underprop my engine. will this size work?

I say try the prop because its for your [will be for an airboat ] you wont loose it like an airplane, It may run with a little more RPM but it wont hurt it, just remember to fine balance the Prop so you wont get a noise sounding like a improper runing engine. If you want to order a good prop go to tower hobbies, you can rush the order if you want, try thes links for a good cheaper prop. LXE655 Dynathrust 16x8 4-Stroke Propeller
7.69 or this one LXZ988 Master Airscrew 16x8 K 4-Stroke Propeller
9.19 an last,LXZ998 Master Airscrew 15x10 4-Stroke Propeller
8.19 [http://www2.towerhobbies.com/cgi-bin...&I=LXE655&P=K]

My little weedie with gutted stock muffler will spin a Zinger 18-8 @ 6600, zinger 16-8@ 7200, master airscrew scimtar 16-6 @ 7900.
I get best performance from the MA 16-6 on a giant ultra stick. It will spin an apc 14-6 and MA SC 14-6 at 9000+ but that sounds to me to be a little fast for this type of engine. Any opinions on this? I'd love to be able to get some more prop clearance, plus for some wierd reason the price of props almost doubles from 14" compared to 16".

Yes I use a 15X8 prop and 15X10 and I have the motor on a super stick 60 by hanger 9, it works very well and the props are x cheap through Tower Hobbies[ http://www.towerhobbies.com/ ]
EXAMPLES . LXE653 Dynathrust 15x8 4-Stroke Propeller
6.69 === LXZ983 Master Airscrew 15x8 K 4-Stroke Propeller
8.19 ====LXZ998 Master Airscrew 15x10 4-Stroke Propeller
8.19 ===LXHY40 Top Flite 15x8 Power Point Propeller
Qty Discount Available
7.49 ===