Does the increase thrust of a 3 bladed make up for the decrease in rpm?
07-08-2015, 09:57 AM
#26
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I broke in an OS 32SX using a 10x6 2 bladed prop. After about 12 flights it would turn 19K on the ground. I then switched it to a 10x4 3 bladed prop and got the same RPM. IIRC pitch contributes more to thrust than diameter, or the number of blades. In reality, one-bladed props are the most effiecient and provide higher thrust with a high pitch than a 4 bladed prop of the same diamater iwth a low pitch,
07-08-2015, 02:05 PM
#29
That is not possible. An 8-6 yes. even an 8-8, maybe. I have a .36 TT that turns an 8-8 at 18,000-19,000 on a quarter wave pipe.
You would not get a .40-.46 to turn a 10-6 at those RPMs.
I raced and flew CL and RC combat for over 20 years. Very immersed engine events. and I call BS on that one. Sorry
07-14-2015, 05:23 AM
#32
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This is just an update. I'm not trying to argue with you guys. I just felt like telling you what is currently going on.
Due to CG balance issues, and Taxi Tests, my Dad feels that we should stay with 14x7 three bladed propeller.
I ordered some different propellers to try. 2 of them should arrive tomorrow. When I get all of the propellers, I will have 14x7 three bladed, 13x8 three bladed, 14x6 two bladed, and 13x8 two bladed. I already have both the 14x7 and 13x8 three bladed. What I noticed is, the plane balances with the 14x7 three bladed, but is giving me fits to balance it with 13x8 three bladed. Since most people (online) seems to be telling me that I should fly the corsair 60 with a 2 bladed propeller. My recent goal has been to balance the model for the two bladed. The biggest reason why my Dad feels we should stick with the 14x7 three bladed is because even before I reach 1/3 rd throttle the tale starts to come off the ground and the plane seems to be getting light. It skips across the grass runway and acts like it's getting ready to fly! Master Airscrew says on towerhobbies that the 3 bladed "creates a greater thrust at a lower RPM". When I originally posted this thread, I didn't know that they made that statement.
Bax says "Start with a 12 x7 or 8 or 13 x 6 or 7" Of course since this is going to be my first flight I don't want to try anything stupid.
Links:
I started a CG Balancing Thread:
http://www.rcuniverse.com/forum/ques...ggestions.html
Link to my Question to Bax:
http://www.rcuniverse.com/forum/o-s-...eller-rpm.html
Links to the propellers:
http://www3.towerhobbies.com/cgi-bin...&I=LXAA40&P=ML
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXAA39
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXZ980
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXZ981
* In case your wondering why I bought the 13x8 three bladed, my local hobby shop suggested it. Then He said, if I still have doubts then go to the 2 bladed.
Due to CG balance issues, and Taxi Tests, my Dad feels that we should stay with 14x7 three bladed propeller.
I ordered some different propellers to try. 2 of them should arrive tomorrow. When I get all of the propellers, I will have 14x7 three bladed, 13x8 three bladed, 14x6 two bladed, and 13x8 two bladed. I already have both the 14x7 and 13x8 three bladed. What I noticed is, the plane balances with the 14x7 three bladed, but is giving me fits to balance it with 13x8 three bladed. Since most people (online) seems to be telling me that I should fly the corsair 60 with a 2 bladed propeller. My recent goal has been to balance the model for the two bladed. The biggest reason why my Dad feels we should stick with the 14x7 three bladed is because even before I reach 1/3 rd throttle the tale starts to come off the ground and the plane seems to be getting light. It skips across the grass runway and acts like it's getting ready to fly! Master Airscrew says on towerhobbies that the 3 bladed "creates a greater thrust at a lower RPM". When I originally posted this thread, I didn't know that they made that statement.
Bax says "Start with a 12 x7 or 8 or 13 x 6 or 7" Of course since this is going to be my first flight I don't want to try anything stupid.
Links:
I started a CG Balancing Thread:
http://www.rcuniverse.com/forum/ques...ggestions.html
Link to my Question to Bax:
http://www.rcuniverse.com/forum/o-s-...eller-rpm.html
Links to the propellers:
http://www3.towerhobbies.com/cgi-bin...&I=LXAA40&P=ML
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXAA39
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXZ980
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXZ981
* In case your wondering why I bought the 13x8 three bladed, my local hobby shop suggested it. Then He said, if I still have doubts then go to the 2 bladed.
07-15-2015, 08:10 AM
#33
If you notice, the primary issue Bax brought up is loading the engine PROPERLY. Getting the engine in the power band is the main objective. Regardless of the number of blades. Usually this is a narrow range. Maybe 2 different props at most.
I am going to cause an uproar here for sure, but I would avoid Master airscrew props. They flex and "unpitch" at RPM. You would be better off with APC for sure. I know this from years of competition flying and lots of prop testing. In particular in Pylon racing and combat. You may be lucky and be able to find a good wood design. This gets you back to the issue that there are just not many good 3 blade designs available. Then if you break one once in a while, you will need to have a good source for replacing them.
I am going to cause an uproar here for sure, but I would avoid Master airscrew props. They flex and "unpitch" at RPM. You would be better off with APC for sure. I know this from years of competition flying and lots of prop testing. In particular in Pylon racing and combat. You may be lucky and be able to find a good wood design. This gets you back to the issue that there are just not many good 3 blade designs available. Then if you break one once in a while, you will need to have a good source for replacing them.
07-15-2015, 11:42 AM
#34
APC (Landing Products) props are pretty much the industry standard, and most everything is compared to them. I have found that for a few applications there are some Master Airscrew (Windsor Propeller Co.) props that work great. I have to agree with V.G. that the larger props can "flex" and flatten out at higher RPM's. But who's to say that they don't work like an aeromatic prop, and regain their pitch at cruise speed? For this model, I would probably look at Master Airscrews last, unless I was determined to fly it with a three blade.
07-15-2015, 12:06 PM
#35
On the larger props, I prefer wood, Beech to be exact and my preference here is Xoar. They retain their pitch. But for props that are 14" and under, the APC are the standard. And yes, I agree that MAS props have some good applications. Like when you do not want a prop to break. They are durable that way, and also some sizes were great in RC combat. But overall, if given other choices, The MAS prop is at the bottom of my list. Problem is, they are one of the companies offering a better selection of 3 bladers.
