What is the difference between wood and non wood props?
 

I was wondering, is there a preformance difference between wood and other props. A few of the guys at my field say get APC props istead of wood, I understand the wood is more prone to breaking . Is there any other differences, do wood props flex more?

Thanks

Jon

RE: What is the difference between wood and non wood props?
 

The most important detail is whether or not a specific prop suits the engine on your airplane and pulls that airplane the way you want it.

Some composite props flex the least of any type props (that're legal). Some nylon ones flexed like rubber. The filled nylon ones (plastic by definition) don't flex much. You can answer the question yourself easily by dropping by a hobby shop. Make sure nobody is watching and flex 'em all. See which bends the most. If you can twist them with your hand, they're going to twist under flight loads.

In actual use flex doesn't mean much at all. The prop pulls through the manuevers you want or it doesn't.

Differences based on composition also don't hold up. Master Airscrew and APC are both filled plastic. But the APC tips are paper thin and can be twisted easily. The MA tips are usually still airfoiled and thick. Is it the plastic or the cross section that matters. So just the composition isn't the point.

The point of decision most often mentioned is that wood props don't stand up as well to landing bounces. So beginners are often told to get a plastic prop and "it'll last longer". It probably will.

BTW, back in the old days when Goodyear racers were homebuilt midget airplanes, one of them had a "home made" wooden prop. This is full scale, not models. And the airplane was a rocket (for the time). Seems the blade twisted under load and bent into more pitch on the straights and less in the turns. So twisting and flexing ain't automatically bad.

RE: What is the difference between wood and non wood props?
 

you'll find that wood props tend to loosen more due to humidty causing the wood to swell and shrink. I use APC only,. never have had a prop issue

RE: What is the difference between wood and non wood props?
 

APC props seem to be more efficient and have less flex than MAS props. The MAS props are more durable than APC, and are a good choice for trainers and belly-landed planes and any other plane that might have prop strikes. Both APC and MAS props are more durable than wood props.

RE: What is the difference between wood and non wood props?
 

The wood props I have seen are very stiff so I doubt that they flex very much. Wood props are typically lighter than APC or other composite props. An engine should rev up quicker with a lighter prop. Some engines idle better with heavy props, so that can be a consideration. Every brand claims their blade design and tip shape is the best.

There’s no definitive answer on prop selection. You really have to try different ones to find what you like. Just because I thing the ‘whiz bang XYZ’ is the only prop worth having doesn’t mean you’ll like it at all.

I mostly use Master Airscrew K series props. They're probably some of the most flexible on the market. They survive most of my landings (some might call them 'on the runway' crashes) and pull my plane around very well. Many will tell you that my props are ony good for stirring paint or cleaning your shoe soles but they work well for me.

RE: What is the difference between wood and non wood props?
 

wood props are also lighter. Some 3D guys only fly wood because of the weight.

RE: What is the difference between wood and non wood props?
 

Thanks, I think ;)

I guess that my question comes from wanting to buy different prop sizes to find which works "best" on my OS 60, I switched to a 11X6 or 12X6 (I don't remeber) and likes the response, I have some 11X8 wood props that I bought before much research and trying to figure out what I might expect from the difference.

Thanks

Jon

RE: What is the difference between wood and non wood props?
 

Jon-

Hard to say that you will notice a whole lot of difference between wood and composite. For a newcomer, durability is really the key. I wouldn't recommend using wood on a sport plane. I've been flying for a while and still have a tendency to occasionally ding my props on the pavement when landing. With a wood prop, it would instantly be toast.

RE: What is the difference between wood and non wood props?
 

The Master Airscrews bend VERY easily.

I have one on a O.S. 91 right now. At idle the prop looks like an out of alignment heli rotor. As it speeds up the prop "bends" back into plane and the engine flies OK.

When I put on an APC however things change dramatically for the better.

The thin TIPS of the APC may bend a bit, but the larger cross sectional areas are VERY sturdy and the props never suffer this problem.

Things being equal the APC's are still much firmer than the Master Airscrew props. e.g. if the cross section is the same, the APC will bend far LESS than the Master Airscrew, probably because of their imbedded carbon fibers.

They also hold up far better in the event of a nose over or MINOR strike.

If an APC's tip hits the ground, the damage tends to be very minor. I just sand those razor knife tips to a nice rounded edge with no appreciable loss of performance since so little material is actually removed and affected.

If a MA hits the ground, it tends to damage it greatly or crack it.

If a wood prop hits the ground, it's time to replace it.

RE: What is the difference between wood and non wood props?
 

My advice is buy a bunch of different props around the size you need and try them all. You'll find that your results will vary and a particular prop, or maybe a couple, will fly your airplane to suit you. Stash the others away, because they probably include the best props for future airplane/engine combinations.

RE: What is the difference between wood and non wood props?
 

my midwest aerobat with a TT 42 and an 10x4 APC prop could barely get off the ground at the end of the 600' runway. I changed the prop to a 9x4 and it went from 11800 rpm to 15500 rpm. its faster but a smaller prop so will it have the same thrust? does anyone know if this is the best prop for a TT 42 or anything else I can improve to get a shorter takeoff? I have not flown it yet with a new prop because it needed repairs after the last take off i think it tip stalled.

RE: What is the difference between wood and non wood props?
 

The numbers in the prop selection mean something. I will use the 10-4 prop mentioned in the previous post as an example.

10 (diameter) means the diameter of the prop... the length from tip to tip of the prop.

4 (pitch) means the amount of theoricical air that the prop will pass through in one complete revolution. So, for each revolution, the prop will pass throug or pass (if standing still) 4 inches of air.

That still counts for the diameter... meaning that it will still only pass 4 inches of air per revolutino, even at 15000 RPM, but because of the more RPM, more will pass through.

The diameter of the prop comes into the equation because the longer the prop is, of course, it will pass through more air per RPM.

Think of changing the pitch as though you were changing gears in your car or truck. In first gear, the car or truck won't go very fast, but it will pull very hard. Second gear, less pull but more speed. Third gear.. more speed, less pulling power and so on. So, for a given prop diameter, changing the pitch will cause that prop to pull more but do so at a slower rate of speed. So, you will accelerate much more quickly with a smaller pitch prop than with one with a larger pitch.

Then the flex comes into the picture. Props that flex during pulling will tend to not pull as hard, will slip, so to speak as it trys to gain thrust or pulling (pushing) power. Carbon composite props are considered the most efficient props because they do not flex, but the expense is also quite a bit more.

The APC props are generally considered good because they are pretty much consistent in weight and usually are in balance when you get them off of the shelf. That does not mean that you should not check the balance, but you are less likely to find one that is badly out of balance when new, usually acceptable enough off the shelf to use right away. And, they are pretty stiff and good for just about most of our sport flying.

They do not tend to break as easy as wood props do. That could be good and that could be bad. Getting your finger in the way of any rotating prop will ruin your whole day no matter the composition, by the way.

So, Mr Maggot, you may want to leave the diameter alone and go to a different pitch. But, also consider that your motor may not be enough to power that midwest aerobat. I had one and used an OS 46 for power and a 10-8 prop which worked out just fine.

DS.

RE: What is the difference between wood and non wood props?
 

i like the Wood props, they are cheap, and when i do break a prop it is normally wore out anyways (nicks, dings, scratches) so i'm not so disapointed, and also like the looks of wood, even on a sport plane:D

RE: What is the difference between wood and non wood props?
 

Jon,
Lot's of props that aren't the first ones suggested are really winners, depending on your engine and airplane.

I'm running a 13x6 Top Flite wooden Power Point on my OS61FX powered Skybolt. The Skybolt is the ARF that is only a shade over 7lbs. The prop worked better than the APCs and Master Airscrews I tried. All are good props, this one just was better. I've been trying different props since completing the airplane last year. Can't count how many have been on the sucker. And the 2nd best prop has been a 3blade 12x6 Master Airscrew. Darned if everyone always bleats about "efficiency", but the OS/Skybolt hasn't listened.

When it comes to props, most of the sound bytes are good conversation starters, but lousy advice to follow. I've been told by more than I can remember that both those props are wrong for the engine and/or airplane..... Was told that before those guys saw the airplane fly. I been messing with these little engines and airplanes since the 50s and all the stuff about props is just stuff. All the brands work like gangbusters. There is really little reason to believe one has any real advantage over another. If you restrict your testing to just one brand, you're going to miss a lot.

RE: What is the difference between wood and non wood props?
 

Thanks again. I am the type of person that tries to understand how and why things work. I have been reading about different prop pitches and how the "work" but have not seen the difference between wood and others, I figured that carbon is the best, and no one has titanium props yet :)

Jon

RE: What is the difference between wood and non wood props?
 

I don't know if I would be enthusiastic about carbon.
Yes carbon fiber has very strong tensil strength but it is brittle and any contact would likely snap the blade.
I have never had carbon props but I have used carbon blades on my helis, it about made me cry when I snapped my new $40 blades on my T-Rex on the first flight. (it was a minor strike that my wooden blades would have survived)
As for props I have recently started using Graupner props on my 4 strokes and so far am really happy with them.

RE: What is the difference between wood and non wood props?
 

Actually, modelers had metal props back in the day. That was before they were banned due to safety reasons of course. There's nothing like having your own moving table saw with no blade guard! [:@]

RE: What is the difference between wood and non wood props?
 

I did not think of that, but I am not sure if a hand would be able to tell the difference between a wood prop or a metal prop, I think they would both cut pretty quick. but I have not found out yet, and I don't plan too, knock on wood.

Jon