3 blade prop for 120ax
10-17-2010, 06:01 PM
#1
Senior Member
Thread Starter
My Feedback: (1)
Join Date: Apr 2008
Location: Auckland, NEW ZEALAND
Posts: 377
Likes: 0
Received 0 Likes
on
0 Posts
3 blade prop for 120ax
Simple question really. Been using a 16x8 2blade and feel it has too much 'pull' so was thinking of dulling it down to a 17x6 2 blade for more torque. What would be a good 3 blade to achieve this purpose? Its going on a goldberg ultimate so its for looks.
Want to order a prop soon from tower so feedback appreciated! They are WAY too expensive in NZ ($44 each!!!) so want to get it right and the 3" 3 blade spinner too.
Thanks!
Want to order a prop soon from tower so feedback appreciated! They are WAY too expensive in NZ ($44 each!!!) so want to get it right and the 3" 3 blade spinner too.
Thanks!
10-17-2010, 06:36 PM
#2
My Feedback: (5)
Join Date: Oct 2002
Location: Indian Trail,
NC
Posts: 2,939
Likes: 0
Received 0 Likes
on
0 Posts
RE: 3 blade prop for 120ax
I really like Graupner but they are pricey and they are on back order with Hobby Lobby. I'd try this one on your 120AX
http://www.hobby-lobby.com/15x8_prop...e_402_prd1.htm
http://www.hobby-lobby.com/15x8_prop...e_402_prd1.htm
10-17-2010, 07:16 PM
#3
Join Date: Jul 2004
Location: Middleboro, MA
Posts: 3,275
Likes: 0
Received 0 Likes
on
0 Posts
RE: 3 blade prop for 120ax
You are really going the right way with your two blade choice, you want more thrust than speed. I would try to find a two blade that does what you want first then try to size the three blade according to how that works out for you given that it going to be a big expense for you to get the right three blade.
It really isn't that simple, except that to go to 3 blade from a two blade the general rule is that you want to DECREASE propeller diameter by 1-2â€, and INCREASE by 1-2†the propeller pitch. How an engine peaks out has a real big effect to how well a three blade works for you and it varies between two 1.20 sitting side by side. The limited sizes are going to be the big heartache for you as far as going with a three blade. Your case may be the smaller diameter and lower pitch three blade is the best answer like a master aircrew 15X7 or 16X8 ???? I know this sounds too close to your original size but the way a three blade performs on engine is pretty subjective, they may not be as efficient but they look cool.
You may want to look at theses guys they are next door to you, shipping wouldn't be that bad and they have great products.
Something they have may work for you bit pricey but very nice performance.
http://www.bolly.com.au/
http://www.bolly.com.au/models/glassthree.html
http://www.bolly.com.au/models/index.html
It really isn't that simple, except that to go to 3 blade from a two blade the general rule is that you want to DECREASE propeller diameter by 1-2â€, and INCREASE by 1-2†the propeller pitch. How an engine peaks out has a real big effect to how well a three blade works for you and it varies between two 1.20 sitting side by side. The limited sizes are going to be the big heartache for you as far as going with a three blade. Your case may be the smaller diameter and lower pitch three blade is the best answer like a master aircrew 15X7 or 16X8 ???? I know this sounds too close to your original size but the way a three blade performs on engine is pretty subjective, they may not be as efficient but they look cool.
You may want to look at theses guys they are next door to you, shipping wouldn't be that bad and they have great products.
Something they have may work for you bit pricey but very nice performance.
http://www.bolly.com.au/
http://www.bolly.com.au/models/glassthree.html
http://www.bolly.com.au/models/index.html
10-17-2010, 07:17 PM
#4
Join Date: Jul 2004
Location: Middleboro, MA
Posts: 3,275
Likes: 0
Received 0 Likes
on
0 Posts
RE: 3 blade prop for 120ax
ORIGINAL: AmishWarlord
I really like Graupner but they are pricey and they are on back order with Hobby Lobby. I'd try this one on your 120AX
http://www.hobby-lobby.com/15x8_prop...e_402_prd1.htm
I really like Graupner but they are pricey and they are on back order with Hobby Lobby. I'd try this one on your 120AX
http://www.hobby-lobby.com/15x8_prop...e_402_prd1.htm
Good luck!
10-18-2010, 09:45 AM
#5
Senior Member
Join Date: Jan 2002
Location: Arcen, , NETHERLANDS
Posts: 6,571
Likes: 0
Received 2 Likes
on
2 Posts
RE: 3 blade prop for 120ax
ORIGINAL: iron eagel
You are really going the right way with your two blade choice, you want more thrust than speed. I would try to find a two blade that does what you want first then try to size the three blade according to how that works out for you given that it going to be a big expense for you to get the right three blade.
It really isn't that simple, except that to go to 3 blade from a two blade the general rule is that you want to DECREASE propeller diameter by 1-2”, and INCREASE by 1-2” the propeller pitch. How an engine peaks out has a real big effect to how well a three blade works for you and it varies between two 1.20 sitting side by side. The limited sizes are going to be the big heartache for you as far as going with a three blade. Your case may be the smaller diameter and lower pitch three blade is the best answer like a master aircrew 15X7 or 16X8 ???? I know this sounds too close to your original size but the way a three blade performs on engine is pretty subjective, they may not be as efficient but they look cool.
You may want to look at theses guys they are next door to you, shipping wouldn't be that bad and they have great products.
Something they have may work for you bit pricey but very nice performance.
http://www.bolly.com.au/
http://www.bolly.com.au/models/glassthree.html
http://www.bolly.com.au/models/index.html
You are really going the right way with your two blade choice, you want more thrust than speed. I would try to find a two blade that does what you want first then try to size the three blade according to how that works out for you given that it going to be a big expense for you to get the right three blade.
It really isn't that simple, except that to go to 3 blade from a two blade the general rule is that you want to DECREASE propeller diameter by 1-2”, and INCREASE by 1-2” the propeller pitch. How an engine peaks out has a real big effect to how well a three blade works for you and it varies between two 1.20 sitting side by side. The limited sizes are going to be the big heartache for you as far as going with a three blade. Your case may be the smaller diameter and lower pitch three blade is the best answer like a master aircrew 15X7 or 16X8 ???? I know this sounds too close to your original size but the way a three blade performs on engine is pretty subjective, they may not be as efficient but they look cool.
You may want to look at theses guys they are next door to you, shipping wouldn't be that bad and they have great products.
Something they have may work for you bit pricey but very nice performance.
http://www.bolly.com.au/
http://www.bolly.com.au/models/glassthree.html
http://www.bolly.com.au/models/index.html
The general rule that works for ALL sizes is:
decrease diameter by 10%, increase pitch by 10%. This rule will keep the load on the engine the same. It will seldom yield available props, but at leat you will have a benchmark.
10-18-2010, 02:06 PM
#7
Senior Member
Thread Starter
My Feedback: (1)
Join Date: Apr 2008
Location: Auckland, NEW ZEALAND
Posts: 377
Likes: 0
Received 0 Likes
on
0 Posts
RE: 3 blade prop for 120ax
Yeah Dave! I realised there is more than an 'Airplanes' forum hehe
Seems counterintuitive to me to currently be running a 16x8 two blade then to go to a 16x8 three blade....but I guess they are totally different animals in terms of performance, air distrubance from blades and so on. I wonder if for the sake of scale something like a 15x9 would be good too?
Seems counterintuitive to me to currently be running a 16x8 two blade then to go to a 16x8 three blade....but I guess they are totally different animals in terms of performance, air distrubance from blades and so on. I wonder if for the sake of scale something like a 15x9 would be good too?
10-18-2010, 02:57 PM
#8
RE: 3 blade prop for 120ax
You are right about why the performance falls off. Having three blades make a lot of dirty air. Also realize your 16x8 two blade is not ideal. If it was you would not be looking for something else. I run the APC 17x6 on mine and it's really good. So looking at it from my side the 16x8 three blade is a good choice.
David
David
10-18-2010, 05:48 PM
#9
My Feedback: (102)
Join Date: Dec 2001
Location: Colonial Beach, VA
Posts: 20,370
Likes: 0
Received 25 Likes
on
25 Posts
RE: 3 blade prop for 120ax
Dave, that "dirty air theory" went out the window a long time ago, you can't forget that the prop is constantly moving forward into new air. no hole in the air from the previous blade. Well, at 20,000 rpm maybe, he's shooting for 9,000.
10-18-2010, 09:07 PM
#10
Senior Member
Thread Starter
My Feedback: (1)
Join Date: Apr 2008
Location: Auckland, NEW ZEALAND
Posts: 377
Likes: 0
Received 0 Likes
on
0 Posts
RE: 3 blade prop for 120ax
ORIGINAL: Hobbsy
Dave, that ''dirty air theory'' went out the window a long time ago, you can't forget that the prop is constantly moving forward into new air. no hole in the air from the previous blade. Well, at 20,000 rpm maybe, he's shooting for 9,000.
Dave, that ''dirty air theory'' went out the window a long time ago, you can't forget that the prop is constantly moving forward into new air. no hole in the air from the previous blade. Well, at 20,000 rpm maybe, he's shooting for 9,000.
to replace my ultrasport 60
10-19-2010, 07:58 AM
#11
My Feedback: (102)
Join Date: Dec 2001
Location: Colonial Beach, VA
Posts: 20,370
Likes: 0
Received 25 Likes
on
25 Posts
RE: 3 blade prop for 120ax
I'd recommend the three blade since that is what I fly mostly, I got hooked on them when flying Diesels because its so easy to replace a 12x8 two blade with a 12x8 three blade for a 50% load increase. The 15x7 Master Airscrew 3 blader would be perfect as would the Graupner 14x7 three blade with its wider blades. A lot to soak in, I know.
10-23-2010, 10:45 AM
#12
Join Date: Aug 2010
Location: Lynn,
MA
Posts: 451
Likes: 0
Received 0 Likes
on
0 Posts
RE: 3 blade prop for 120ax
How are ya? quick question, seing how I need reverse rotation props,Do they make them or do I use a pusher prop on a reverse rotating forward facing motor?
