Author Topic: Questions for people who have used 3 bladed props. (Read 3270 times)

frank mccune · « **on:** June 26, 2014, 06:21:21 AM »

Hi All:

I was thinking of using three blade props so I went to the MAS home page and this is what I read.

When selecting a three blade prop, the suggestion is to select a prop that has one inch less diameter and two inches more pitch. I guess that in lieu of an 10X6, two blade prop I need a 9X8 three blade prop. Likewise it will be 8X6 three blade prop in place of the 9X4 two blade prop for the .25 size engines.

Has anybody used props with 3 blades that had 2" more pitch and one inch less diameter? If so how did it work?

Tia,

Frank

Gene O'Keefe · « **Reply #1 on:** June 26, 2014, 07:53:23 AM »

My 3 blades have 3.5" to 4.5" pitch - anymore and the speed is to fast for me.

Dave_Trible · « **Reply #2 on:** June 26, 2014, 08:12:08 AM »

I'd probably agree with using a knotch less diameter to keep the load down on the engine. Not sure about the pitch difference, at least to that degree. Might speak to the quality of the prop. In my application I can use pretty much the same pitch whether 2, 3, or 4 blades with only the same slight variations I find from like props which I have manhandled the prop pitch. I'd at least try to start with the same pitch and go from there. If you can't reset the pitch (mostly just carbon) then you may be limited simply by what is available off the shelf.

Dave

Brett Buck · « **Reply #3 on:** June 26, 2014, 01:22:15 PM »

Quote from: frank mccune on June 26, 2014, 06:21:21 AM

Hi All:

I was thinking of using three blade props so I went to the MAS home page and this is what I read.

When selecting a three blade prop, the suggestion is to select a prop that has one inch less diameter and two inches more pitch. I guess that in lieu of an 10X6, two blade prop I need a 9X8 three blade prop. Likewise it will be 8X6 three blade prop in place of the 9X4 two blade prop for the .25 size engines.

Has anybody used props with 3 blades that had 2" more pitch and one inch less diameter? If so how did it work?

What is "MAS"? 2" more pitch sounds ridiculous for a CL stunt application. We use the same pitch on 2 or 3 (or 4) blade props. You never know for sure without trying but a 9-8 prop is not going to be much of a stunt prop. And you certainly don't want an 8-6 three-blade where you were using a 9-4 before. People have run, successfully (for a few flights, at least) a 10-4 3-blade where they should be running a 9-4 2-blade.

The quickest answer on the diameter is, try it and see. If I was going to use a 2-blade in place of my current 12.5-3.75 3-blade, I would probably start with a 12.5-3.75. That's because neither prop comes close to maxing out the engine and the loss of 1/3 of the blade area might be compensated by the slightly increased efficiency.

Brett

bob whitney · « **Reply #4 on:** June 26, 2014, 04:33:19 PM »

what Brett says . on my E formula -S,i was using an E,LH 12/6 two lbade and it was lugging a bit. i took a 12/5.5 three blade ,cut it to 10.5 and re-shaped it the same as the full blade and it works great all props are carbon

Eric Viglione · « **Reply #5 on:** June 26, 2014, 07:52:07 PM »

Quote from: Brett Buck on June 26, 2014, 01:22:15 PM

What is "MAS"? <SNIP>
Brett

He can correct me if I'm wrong Brett, but I believe he was referring to Master Air Screw as MAS. And if that is the case, it adds a whole new aspect to his question... maybe their somewhat flimsy black plastic 3B props need a couple extra inches of pitch for when they flatten out, heh heh.

My short answer would have been:

"No MAS!"

(That was just for Howard)

EricV

frank mccune · « **Reply #6 on:** June 27, 2014, 05:12:44 AM »

Hello to all:

Yes, Eric, I was speaking about Masterairscrew by Windsor Propeller Co. This was my source of information concerning props with three blades.

I think that it will be no mas for me concerning these props. I still perfer to use wooden props despite the fact that they are quite fragile on bad landings. I was also looking to gain a bit of ground Clarence with a prop of less diameter. How much difference could there be between a 10X6 and an 11X5 prop? Perhaps a 9X6 would be a better choice than a three blade prop. Allow that thing to run in a wet 2 cycle!

I do have a silver coloured three blade prop, 10X6 that will look very cool on my profile Zero.

Stay well.

Frank

EddyR · « **Reply #7 on:** June 27, 2014, 06:46:36 AM »

For many years I have run a 11/5 two blade on my ST/46's. I recently put a 46 in a plane with a short gear. The 11/5 would not clear unless I did a full up takeoff. I put a 9/6 three blade on it and was perfect. I just didn't think that prop would fly the plane the same as the 11/5.It flew better. The motor loves the three blade 9/6 .

Ed

Brett Buck · « **Reply #8 on:** June 27, 2014, 09:12:22 AM »

Quote from: EddyR on June 27, 2014, 06:46:36 AM

For many years I have run a 11/5 two blade on my ST/46's. I recently put a 46 in a plane with a short gear. The 11/5 would not clear unless I did a full up takeoff. I put a 9/6 three blade on it and was perfect. I just didn't think that prop would fly the plane the same as the 11/5.It flew better. The motor loves the three blade 9/6 .
Ed

In that case it doesn't surprise me too much (after endless hours in the hot sun testing box after box of ST46 props) - an 11-5 not enough prop to take full advantage of the engine in many cases. Thats definitely in the tradeoff area between the "airplane turns better but no vertical performance". A 13-5 might work better with a *stock* engine as long as you are willing to throw the coals to it. A 9-6 puts it further down on the curve so the engine is not running out of poop. On a very small airplane that could be pretty good.

But, ultimately, your implied advice is right - you can make educated guesses about what props might work or not, but ultimately, you just have to try things and see. Paul Walker flew his Bad News with a 45FSR on a 9-4 Rev-up in Reno for a few flights. You have to be willing to try things like that, and evaluate the results objectively.

Brett

FLOYD CARTER · « **Reply #9 on:** June 27, 2014, 10:50:18 AM »

I've saved myself many hours of prop testing by simply analyzing what others have successfully used on a particular engine and particular plane. Perhaps I'm not into looking for ultimate performance, but the "average" prop for a given combo seems to work pretty good.

Floyd

Steve Helmick · « **Reply #10 on:** June 28, 2014, 09:51:11 PM »

Not much comparison from one brand of prop to another. I'm willing to try all the props I can get my hands on, in any size that seems remotely practical. I can generally tell if the prop is too much load, but I am often wondering if a prop is not enough load. I'd like to know how to tell, if anybody can 'splain.

I have had a couple of good experiences with 3 blade props, but I am often puzzled by the attraction. "Looking cool" doesn't rate high for me, I guess. I am fixin' to put a 3 blade on my current PA plane, but if I can't make it work better than my recarved 12.25 x 3.75 APC, it'll be back to the tea kettle again and again, if not off for good.
Hey, can we run a heat gun off the 120v AC line at Scobee Field? Boy, that would be sweet!

Steve

Dane Martin · « **Reply #11 on:** June 30, 2014, 11:13:13 PM »

the MAS Website lists those "measurements" as it pertains to RC, or models with a throttle. you know, it's that old school RC mentality where "trainers or scale planes need lots of pitch!" i heard that a lot from the fellas around our site. anyway, it's crazy for CL , like Brett said. most guys stick with a prop based on the fact that it worked on an earlier model

Lauri Malila · « **Reply #12 on:** July 01, 2014, 12:21:21 PM »

Hi.

I have found that with same launch rpm, my bigger 14,2" 3-blader needs about 1/8" less pitch for same laptime, than my 13,4" props. Well, I rarely measure the laptimes, I do what feels good. Also, bigger prop allows slower level flight because of better acceleration/static thrust. But the biggest benefit is the way how they brake in downhill.
But it's all about finding the golden middle, big dia. is really nice in perfect weather but smaller is nicer in wind. Also, the gyroscopical action of prop is clearly bigger with bigger diameter prop, sometimes it gets a bit annoying. At the moment I am working with something in between, new 13,75" props.
Now our props have a flat back airfoil but I think I must study carefully what Igor has written about undercamber blades.

Lauri

RandySmith · « **Reply #13 on:** July 01, 2014, 02:34:18 PM »

Quote from: Lauri Malila on July 01, 2014, 12:21:21 PM

Hi.

I have found that with same launch rpm, my bigger 14,2" 3-blader needs about 1/8" less pitch for same laptime, than my 13,4" props. Well, I rarely measure the laptimes, I do what feels good. Also, bigger prop allows slower level flight because of better acceleration/static thrust. But the biggest benefit is the way how they brake in downhill.
But it's all about finding the golden middle, big dia. is really nice in perfect weather but smaller is nicer in wind. Also, the gyroscopical action of prop is clearly bigger with bigger diameter prop, sometimes it gets a bit annoying. At the moment I am working with something in between, new 13,75" props.
Now our props have a flat back airfoil but I think I must study carefully what Igor has written about undercamber blades.

Lauri

3 , 4 and 5 blade props also give nice braking and even speed, without as much G/P , you may want to look at them and give extra time to working with them

Randy

Lauri Malila · « **Reply #14 on:** July 01, 2014, 03:25:27 PM »

Yes why not, I'll give it a try after Poland. At least power shouldn't be a problem. But maybe I will need to make a new, huge 3oz. fuel tank

M Spencer · « **Reply #15 on:** July 03, 2014, 07:04:17 AM »

" I do have a silver coloured three blade prop, 10X6 that will look very cool on my profile Zero. "

spay with amourall & keep it damp in a plastic bag for a week , if tornado / Grish .
these were ' the ' ST 46 prop ,

OS 35 likes the 10 x 4 , the 9 x 6 works but dosnt ' lock in ' like the 10 x 4 . ' they ' used to say the 10 x 6 was 5 in pitch , ANYWAY .

Olde Drivle said subtract an inch going two to three , on the diameter .

Full Size heronautical works on Blade Area to Absorb HORSEPOWER , the 5 blade rotated the Seafurys less than the prototypes four blade ,
full wellie off the deck .
Important not to chew up the deck , ' arriveing ' on carriers too .

Author Topic: Questions for people who have used 3 bladed props. (Read 3270 times)

frank mccune

Questions for people who have used 3 bladed props.

Gene O'Keefe

Re: Questions for people who have used 3 bladed props.

Dave_Trible

Re: Questions for people who have used 3 bladed props.

Brett Buck

Re: Questions for people who have used 3 bladed props.

bob whitney

Re: Questions for people who have used 3 bladed props.

Eric Viglione

Re: Questions for people who have used 3 bladed props.

frank mccune

Re: Questions for people who have used 3 bladed props.

EddyR

Re: Questions for people who have used 3 bladed props.

Brett Buck

Re: Questions for people who have used 3 bladed props.

FLOYD CARTER

Re: Questions for people who have used 3 bladed props.

Steve Helmick

Re: Questions for people who have used 3 bladed props.

Dane Martin

Re: Questions for people who have used 3 bladed props.

Lauri Malila

Re: Questions for people who have used 3 bladed props.

RandySmith

Re: Questions for people who have used 3 bladed props.

Lauri Malila

Re: Questions for people who have used 3 bladed props.

M Spencer

Re: Questions for people who have used 3 bladed props.