HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Mar 09, 2012, 01:35 PM
Registered User
Worcestershire, England
Joined Nov 2007
481 Posts
Discussion
Wooden props or nylon/plastic props.

Hi folks.
I'm after a few opinions on an issue i currently have regarding propellers.
All of my planes are either electric or glow. Until now that is.
I've now got a DLE 20 fitted in a Flair Swallow.
Most people are telling me to use a wooden prop as apposed to the usual nylon/plastic types. I've bowed to the knowledge of my fellow club members and have a few wooden props for my DLE 20.
Yet i'm puzzled with the explanation i get for using wooden props on a petrol/gas engine. I'm told that using a wooden prop saves the crank being damaged in the event that the prop strikes the ground. I understand this, but surely if crank damage was such a risk then surely "we" would use wooden props on our glow motors to. Which in my club is very rare??
Whats the difference?
Opinions appreciated
Jam1e is offline Find More Posts by Jam1e
Reply With Quote
Sign up now
to remove ads between posts
Old Mar 09, 2012, 01:49 PM
Fueled by Arabica Beans
ChillPhatCat's Avatar
United States, NY, Syracuse
Joined Oct 2008
3,826 Posts
The only thing I can see is if for some reason gas engine manufacturers use lower grade steel for the crankshaft. (does anyone know?) I've seen a lot of nylon/glass and carbon fiber props on gas engines though... I don't think there's much more of a threat if any to the crankshaft compared to glow engines.
ChillPhatCat is offline Find More Posts by ChillPhatCat
Reply With Quote
Old Mar 09, 2012, 02:19 PM
Registered User
United States, TX, Leander
Joined Sep 2003
2,385 Posts
Chillphatcat hit the nail on the head. In my opinion, thats why I use wood on gas engines. I've worked on enough to see that the cranks are not as robust as those on a glow engine. I'll run MA and APC on my glows. I've bent more than a few gas cranks over the years, only one glow crank.
Edwin
edwin1 is online now Find More Posts by edwin1
Reply With Quote
Old Mar 09, 2012, 02:23 PM
Who Dat!
GeetarJoe's Avatar
United States, LA, New Orleans
Joined Sep 2011
650 Posts
2 reasons:
1) wood props are lighter. especially when you get to the bigger sizes, 18" and up, composite props are downright HEAVY.

2) larger engines (15cc+) spin bigger props with more energy behind them. long and heavy composite blades spinning really fast can exert more than enough leverage on the crankshaft to bend it. on bigger airplanes a wood prop can act as a sacrificial fail point. in the event of a prop strike from a bad landing, or in my case this weekend a lost landing gear wheel, a wood prop will break when it hits the ground; usually this saves the airframe and/or engine crankshaft from damage.
GeetarJoe is offline Find More Posts by GeetarJoe
Reply With Quote
Old Mar 09, 2012, 02:39 PM
Registered User
Worcestershire, England
Joined Nov 2007
481 Posts
Quote:
Originally Posted by GeetarJoe View Post
2 reasons:
1) wood props are lighter. especially when you get to the bigger sizes, 18" and up, composite props are downright HEAVY.

2) larger engines (15cc+) spin bigger props with more energy behind them. long and heavy composite blades spinning really fast can exert more than enough leverage on the crankshaft to bend it. on bigger airplanes a wood prop can act as a sacrificial fail point. in the event of a prop strike from a bad landing, or in my case this weekend a lost landing gear wheel, a wood prop will break when it hits the ground; usually this saves the airframe and/or engine crankshaft from damage.
Thanks Joe.
So in basic terms, a petrol engine will run larger props so have more leverage to bend a crank?
Jam1e is offline Find More Posts by Jam1e
Reply With Quote
Old Mar 09, 2012, 02:44 PM
Who Dat!
GeetarJoe's Avatar
United States, LA, New Orleans
Joined Sep 2011
650 Posts
Quote:
Originally Posted by Jam1e View Post
Thanks Joe.
So in basic terms, a petrol engine will run larger props so have more leverage to bend a crank?
yes. think of the blade on the prop acting as a lever when it hits the ground. the longer the lever is, the more leverage is applied. when you add speed and mass the force on the fulcrum point, in this case the crankshaft, multiplies. with longer props you can easily apply enough leverage to bend a crankshaft.
GeetarJoe is offline Find More Posts by GeetarJoe
Reply With Quote
Old Mar 09, 2012, 02:57 PM
Registered User
Toysrme's Avatar
Birmingham, Alabama
Joined Jun 2002
2,969 Posts
had a ton of engines in the 20-30cc range over the years. i've broken exactly 0 crankshafts in my 18 years of flying in that range, and i only have ONE plane i run wood props on in 20-30cc (a xoar). they cost too much & break easy, but expensive props > new more expensive engine. otherwise it's all APC's (narrow or wide profiles) or MAS classics. and MAS-C's are easily the toughest props worth anything.

if people are breaking crankshafts, they should quit buying chinese engines with who know's what crappy cheap alloy they decide to make the cranks out of.
or learn to land & quit breaking them in the first place. (yes, that means YOU Mr. always high-alpha landing. why not try landing for real & stop breaking them? durrr) ya, you can break a crank if you... shear off most of the prop... for the typical "ooops" landing where you just knick off an 1/8" it'd have to be chinese to break. (which is where the composite props are better. you knick a wood prop theyll split & it's a throw away. you knick a composite prop and you may riffle up a MAS-C, or knock off 1/8-1/4" from an apc-s)


it's that simple. the problem isn't the props. it's the morons busting things trying to pass off props as the problem instead of the inferior *everything* in their popular, cheap chinese engines.
Toysrme is offline Find More Posts by Toysrme
Last edited by Toysrme; Mar 09, 2012 at 03:02 PM.
Reply With Quote
Old Mar 09, 2012, 03:24 PM
Registered User
United States, TX, Leander
Joined Sep 2003
2,385 Posts
I dont think its as much breaking a crank as bending one. It will happen from time to time in a crash. The only glow crank I bent was a verticle impact into pavement. I've bent two gasser cranks (being stupid too low) on hard dry ground. I'm just a sport flyer, but like the occasional screamin low pass.
Edwin
edwin1 is online now Find More Posts by edwin1
Reply With Quote
Old Mar 09, 2012, 04:00 PM
Who Dat!
GeetarJoe's Avatar
United States, LA, New Orleans
Joined Sep 2011
650 Posts
Geez Toys.. why don't you tell us all how you really feel. lol
GeetarJoe is offline Find More Posts by GeetarJoe
Reply With Quote
Old Mar 09, 2012, 04:24 PM
Registered User
earlwb's Avatar
USA, TX, Grapevine
Joined Dec 2008
12,335 Posts
I think the most likely reason to use a wood prop is that the wood prop might possibly break before it cuts off your arm, leg or head. The plastic prop being less fragile is likely to do some serious damage to you if you both come into contact with each other.
But if you are careful then it is a non-issue, I suppose. The problem is a big gasser has a pretty stout prop on it, and it isn't going to break easily anyway. So it will probably cut off a appendage anyway.
earlwb is offline Find More Posts by earlwb
RCG Plus Member
Latest blog entry: My Low Wing plane
Reply With Quote
Old Mar 09, 2012, 07:02 PM
Registered User
Toysrme's Avatar
Birmingham, Alabama
Joined Jun 2002
2,969 Posts
that's fine on small engines, but im with you. i think it's silly for people to imagine 20cc+ engines actually running won't chew up anything they come into contact with. let's face it. for the vast majority of all hand+prop incidents are nothing. you were reaching for the glow or needle valve & brushed a knuckle into the trailing edge of a prop. i've done it. everybody's done it.

RC Plane Accident - Why you shouldn't stay near the propeller ! (1 min 43 sec)
Toysrme is offline Find More Posts by Toysrme
Reply With Quote
Old Mar 09, 2012, 08:32 PM
Fueled by Arabica Beans
ChillPhatCat's Avatar
United States, NY, Syracuse
Joined Oct 2008
3,826 Posts
I've never touched a spinning prop in 20 years.





Well... not entirely. I've hit myself with my small helis on several occasions.
ChillPhatCat is offline Find More Posts by ChillPhatCat
Reply With Quote
Old Mar 10, 2012, 02:24 AM
Registered User
Worcestershire, England
Joined Nov 2007
481 Posts
Quote:
Originally Posted by Toysrme View Post
had a ton of engines in the 20-30cc range over the years. i've broken exactly 0 crankshafts in my 18 years of flying in that range, and i only have ONE plane i run wood props on in 20-30cc (a xoar). they cost too much & break easy, but expensive props > new more expensive engine. otherwise it's all APC's (narrow or wide profiles) or MAS classics. and MAS-C's are easily the toughest props worth anything.

if people are breaking crankshafts, they should quit buying chinese engines with who know's what crappy cheap alloy they decide to make the cranks out of.
or learn to land & quit breaking them in the first place. (yes, that means YOU Mr. always high-alpha landing. why not try landing for real & stop breaking them? durrr) ya, you can break a crank if you... shear off most of the prop... for the typical "ooops" landing where you just knick off an 1/8" it'd have to be chinese to break. (which is where the composite props are better. you knick a wood prop theyll split & it's a throw away. you knick a composite prop and you may riffle up a MAS-C, or knock off 1/8-1/4" from an apc-s)


it's that simple. the problem isn't the props. it's the morons busting things trying to pass off props as the problem instead of the inferior *everything* in their popular, cheap chinese engines.
Why do you write such an aggressive post??
Very unnecessary.
Jam1e is offline Find More Posts by Jam1e
Reply With Quote
Old Mar 10, 2012, 02:47 AM
Registered User
Worcestershire, England
Joined Nov 2007
481 Posts
Quote:
Originally Posted by Toysrme View Post
that's fine on small engines, but im with you. i think it's silly for people to imagine 20cc+ engines actually running won't chew up anything they come into contact with. let's face it. for the vast majority of all hand+prop incidents are nothing. you were reaching for the glow or needle valve & brushed a knuckle into the trailing edge of a prop. i've done it. everybody's done it.

http://www.youtube.com/watch?v=tzXyYX7hZvw
Ouch!!!!
That is some severe injury!!
Two years ago I stupidly pulled my hand through a prop when retrieving my glow stick.
Split my thumb in two and cut right through my index finger, bone and all!!
I had surgery and 4 days in hospital to sort it out.
And i thought that was bad enough, but that video had me clutching my hands together!!
Jam1e is offline Find More Posts by Jam1e
Reply With Quote
Old Mar 10, 2012, 07:46 AM
Registered User
earlwb's Avatar
USA, TX, Grapevine
Joined Dec 2008
12,335 Posts
Yeah when you see things like that, you tend to get pretty paranoid about it. It does give one pause to think and plan their safety issues more.
earlwb is offline Find More Posts by earlwb
RCG Plus Member
Latest blog entry: My Low Wing plane
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Help! I need help to find black nylon/plastic threaded 3mm spacers. T.Rex.450 Multirotor Talk 6 Nov 17, 2011 03:35 PM
Discussion Wooden blades...plastic blades....carbon blades...huh? makenzie71 Electric Heli Talk 10 Sep 23, 2011 06:40 AM
Wanted 8 -32 plastic or nylon bolts with hex head or allen heads BrianSmith Aircraft - General - Miscellaneous (FS/W) 3 Mar 28, 2009 06:28 AM
Question Plastic or Nylon Staple ideas... Lavawing Slope 8 Aug 26, 2006 07:33 PM