PROP CHARTS

Starting propeller sizes are mid range pitch props that should fly just about any plane designed for that size engine. Use these first as in most cases they will be close to being the correct size. Then use trial and error to try and fine tune the maximum performance from your plane by trying the alternate props. If none work better then stick with the recommended starting prop. Remember not to overload (too big/coarse prop) the engine while running in.

 

2-Stroke

 

Engine Size 2-Stroke	Starting Prop	Alternate Props
.049	6x3	5.25x4, 5.5x4, 6x3.5, 6x4, 7x3,
.09	7x4	7x3, 7x4, 7x5,
.15	8x4	8x5, 8x6, 9x4,
.20	9x4	8x5, 8x6, 9x5,
.25	9x6	9x5, 9x6, 9x7, 9.5x6, 10x5,
.35	9x7	9x7, 10x5, 11x4,
.40	10x6	9x8, 11x5,
.46	11x6	10x6, 11x5, 11x6, 11x7, 12x4,
.50	12x6	10x8, 11x7, 12x4, 12x5, 12x6, 12x7,
.61	12x7	11x7.5, 11x7.75, 11x8, 12x6,
.70	13x8	11x8, 12x8, 13x6, 13x7, 13x8, 14x4,
.80	14x6	12x8, 14x4, 14x5,
.91	14x7	13x8, 15x6, 16x5,
1.08	16x6	15x8, 18x5,
1.20	16x8	16x10, 18x5, 18x6,
1.50	18x6	18x8, 20x6,
1.80	18x8	18x10, 20x6, 20x8, 22x6,
2.00	20x8	18x10, 20x6, 20x10, 22x6,

 

4-Stroke

 

Engine Size 4-Stroke	Starting Prop	Alternate Props
.20	9x6	9x5, 10x5,
.40	10x5	10x6, 10x7, 11x4, 11x5, 11x6, 11x7, 12x4,12x5,
.52	12x6	10x6, 10x7, 10x8, 11x7, 11x7.5, 12x4, 12x5, 12x6,
.65	12x7	11x7.5, x11x7.75, 11x8, 12x8, 13x5, 13x6, 14x5, 14x6,
.80	13x6	12x8, 13x8, 14x4, 14x6,
.91	14x6	13x6, 14x8, 15x6, 16x6,
1.20	16x6	14x8, 15x6, 15x8, 16x8, 17x6, 18x5, 18x6,
1.60	18x6	15x6,15x8, 16x8, 18x6, 18x8, 20x6,
2.40	18x10	18x12, 20x8, 20x10,
2.70	20x8	18x10, 18x12, 20x10,
3.00	20x10	18x12, 20x10,

 

Elementary Prop Safety

• Install the prop with the curved side of the blade facing forward and tighten the prop nut or bolt with the proper size wrench.

• Re-check the tightness of the nut or bolt often, especially on wood props which tend to compress and loosen more often.

• When starting the engine, keep spectators at least 20 feet clear of the model and out of the path of the propeller should it shed a blade.

• Keep hands away from the prop as much as possible. Use a chicken stick or electric starter.

• Keep face and body out of prop arc as engine is started and run.

• Make all the adjustments from behind the prop except on pusher prop installations.

• Never throw anything into the prop to stop the engine. Use a kill switch or pinch off the engines fuel supply.

• Never use metal props

• Discard any prop with nicks, scratches, splits, cracks or any other sign of damage. Never attempt to repair, alter or bend a prop.

• Don't run an engine in areas of loose gravel or sand for the prop can throw such material into your face and eyes. It's not a bad idea to wear protection.

• Keep loose clothing, shirt sleeves, and other such items away from the prop and avoid carrying objects that can fall into the prop such as pens, screwdrivers, etc.

• Be sure to keep the glow driver wire and starter motor wire out of the prop path.

• If a spinner is used, be certain that it's edges are not in contact with the propeller blades.

 

It's easy to take the humble propeller for granted, but a faulty or damaged prop can seriously hurt your beloved plane and/or engine, not to mention yourself. An unbalanced prop will knock out the bearings in your motor, an expensive repair for the sake of replacing a prop which may just cost a few pounds. A prop that destructs mid air will probably rip the engine from it's mounting or at least shake your plane to bits before you can get it on the ground, if it were to destruct on the ground then it can be extremely dangerous, shed blades have been known to travel long distances. Be warned.
 

Always balance your new props... you will be surprised at how far out they can be off the shelf, don't take it for granted that every prop you buy is perfectly balanced, most are not.... an unbalanced prop is noisy and as said before can damage an engine. A prop balancing tool will cost between £4 - £22+, it doesn't take too much effort to improve the prop's balance, and your motor will run smoother and produce more power!
 

Never remove material from the front (leading edge) of the prop. If the balance is quite a way out then take a little at a time from the rear (trailing edge) using a modelling knife or a fine file, fine wet and dry is also good as it doesn't score the blade. If the balance is not far out then add some varnish to the lighter blade or widen the painted stripe on the tip. If you are using a moulded prop (most smaller "plastic" type props are) remember to remove any excess "flash" left over from the manufacturing process.