Author Topic: 2 Blade Prop to 3... (Read 6021 times)

Joe Yau · « **on:** May 09, 2008, 12:50:06 PM »

Just wondering if there is a chart or something to convert the size of a 2 blade to a 3 blade. For example: If I'm running a 13X7 2B prop. What is the equivalent size to run in a 3 blade like from Eather etc. and also the performance differences..

Thanks in advance

Randy Powell · « **Reply #1 on:** May 09, 2008, 01:39:48 PM »

As a very general (very general) rule, a three blade should be about an inch less diameter. So in your case, a 12x7 three blade. Remember, a lot has to do with the torque of the engine, rpm and other such concerns.

Alan Resinger · « **Reply #2 on:** May 09, 2008, 04:26:23 PM »

Joe,
If the weather is decent on Sunday, I'll be at the field. I've got a bunch of Eather and my own CF 3 blades that you can try.
Alan

Joe Yau · « **Reply #3 on:** May 10, 2008, 09:58:21 AM »

Hi Alan,

Much appreciate the offer! The weather forecast doesn't look too good for flying though.. with 25km wind. and the plane is not quite at that stage yet. hopefully soon.

Joe Yau · « **Reply #4 on:** August 04, 2008, 08:02:48 PM »

I just ordered a MAS 11"x7" 3 blade to try out for the Stalker .61 powered Magnum Plus. (I've been using a 12x6 APC) hopefully it'll give me an idea the difference are (flying characteristic) before I invest in a $$$ CF type prop.

Mark Scarborough · « **Reply #5 on:** August 04, 2008, 08:29:11 PM »

I dont know if I would take the results with the master airscrew three blade as being much of an indication as to a true performance. they tend perform as a much lower pitch prop and are not very efficient in my experience. Just my experience, yours may vary

Garf · « **Reply #6 on:** August 04, 2008, 09:57:35 PM »

I used to run the Tornado 3 blade props when they were available. They worked great.

Joe Yau · « **Reply #7 on:** August 05, 2008, 08:01:07 AM »

Quote from: Mark Scarborough on August 04, 2008, 08:29:11 PM

they tend perform as a much lower pitch prop and are not very efficient in my experience. Just my experience, yours may vary

Should I be getting a 11x8 instead of a 11x7 ?

Mark Scarborough · « **Reply #8 on:** August 05, 2008, 10:51:11 AM »

You could try a 8 pitch, I just dont know how much actual correlation there will be to the current crop of CFG three blades out there as they tend to be much much more efficient. but its a starting place anyway

Steve Helmick · « **Reply #9 on:** August 09, 2008, 02:03:33 PM »

I'd like somebody to explain any benefits of a 3 blade prop, other than increased ground clearance. They're a PITA to balance, start (without electric finger!), more likely to be damaged, more expensive, more weight. Reduced diameter might make a small difference on the turning radius, but I can't help thinking that it's something that can be trimmed around....reduced diameter with wider blades (2ea), for instance.

Otherwise, the Magnum Plus is a great flying design...should be built more often. Is this Ex-Varley, by chance? I don't think I ever saw Keith with one, but there are rumors...er, rumours...going 'round.

Steve

Joe Yau · « **Reply #10 on:** August 11, 2008, 10:57:37 AM »

Quote from: Steve Helmick on August 09, 2008, 02:03:33 PM

Otherwise, the Magnum Plus is a great flying design...should be built more often. Is this Ex-Varley, by chance? I don't think I ever saw Keith with one, but there are rumors...er, rumours...going 'round. Steve

didn't know this post was still active..

I do have to agree that the Magnum Plus is definitely a great flying plane. (based on the one I have) Rumors are correct though, that it is Keith Varley's old 2003 Magnum Plus Derivitive plane (see pics below). He gave it to me last October (still havn't quite got over the generosity from Keith) , and I competed in my very first stunt event with it last month. if I didn't get so damn nervous and forget manoeuvers I could of done better.

Keith Varley at Rice Mill Field in 2003.

Joe Yau · « **Reply #11 on:** August 13, 2008, 11:44:07 AM »

I have heard from quite a few people saying about the 3 blade props softens the corners.. but when I see them fly, their corners are as tight or maybe even tighter then planes with 2 blade props, but they do corners and coming out smoother as it seems. not sure if that is just the gyroscopic diff.

Andrew Borgogna · « **Reply #12 on:** August 13, 2008, 01:56:22 PM »

Joe
Forgetting a manoeuver in your first ever contest is a time honored tradition in this hobby. Welcome to the club.

Andy "What's the next manoeuver?" Borgogna

Alan Hahn · « **Reply #13 on:** August 13, 2008, 02:43:08 PM »

Quote from: Steve Helmick on August 09, 2008, 02:03:33 PM

I'd like somebody to explain any benefits of a 3 blade prop, other than increased ground clearance.......<snip>
Steve

"Bingo". I think ground clearance is about the only real reason. For my electrics I want a big a prop load (leaving some details out --but you can see my prop calculation link in the electric section to see what I am thinking about). So far I have a 12-6 on my TF Nobler Arf, but had to put on longer gear and larger wheels to get the ground clearance.

I think this has always been the reasons---just look at the WW2 fighters and bombers. They needed something to translate engine power to thrust and still be able to put the gear away after takeoff!

About corners---I don't think so. The angular momentum that one fights (aka gyroscopic effect) scales as
1)the square of the diameter
2) linearly with the number of blades
3) linearly with rpm

So dropping from 12 to 11 but going to 3 blades gives (3*11^2/)/(2*12^2)=3*121/2*144=1.26 more gyro effect for a 3 blade 11" prop over a 2 blade 12" prop (assuming same rpm and blade mass distribution).

Joe Yau · « **Reply #14 on:** August 22, 2008, 01:45:02 PM »

Quote from: Mark Scarborough on August 04, 2008, 08:29:11 PM

I dont know if I would take the results with the master airscrew three blade as being much of an indication as to a true performance. they tend perform as a much lower pitch prop and are not very efficient in my experience. Just my experience, yours may vary

The 11x7 MA finally arrived early this week and it looks to be very flat in the pitch (as you have mention). most of the high part of the pitch is too close to the center, and I'm pretty sure a 2" spinner will block part of it. so I might get a 12x8 and cut it down to 11" maybe.

Busby · « **Reply #15 on:** August 22, 2008, 02:26:00 PM »

Just as an aside ,I have found that the engine runs on both a Aero Tiger 36 And a PA40 piped Shrike were helped
considerably with three blade props .
The 36 with an 11 x 4 Narrow Bolly and the PA 40 with an 11- 3/8 x 4.1.
Both of these smoothed the engine run as well as giving more drive thru and out of the corners.
Both run in a 4-2 break.
Busby

Joe Yau · « **Reply #16 on:** September 25, 2008, 06:52:00 PM »

Well, after putting in a total of 6 flights with a 3 blade prop.. I have concluded that the biggest improvement is the climb, and the cornering. Also its quieter then the 2 blades. I'm also quite impressed with the Stalker .61..

Steve Helmick · « **Reply #17 on:** September 25, 2008, 07:12:26 PM »

Quote from: Joe Yau on August 11, 2008, 10:57:37 AM

didn't know this post was still active..

I do have to agree that the Magnum Plus is definitely a great flying plane. (based on the one I have) Rumors are correct though, that it is Keith Varley's old 2003 Magnum Plus Derivitive plane (see pics below). He gave it to me last October (still havn't quite got over the generosity from Keith) , and I competed in my very first stunt event with it last month. if I didn't get so damn nervous and forget manoeuvers I could of done better.

Keith Varley at Rice Mill Field in 2003.

Huh! I think I may have seen The Varley with that particular plane. Never realized its relation to this one, tho, which I believe to be a fairly standard Magnum Plus out of the Danny Dirt stable.

Pete Peterson told me that the 3 blade will soften the corner. I might prefer moving the CG forward? If it's not the same, maybe someone will 'splain? I tend to like the CG forward enough to give good wind penetration in the glide, and less funny stuff on takeoff. Could be wrong, tho. All (three) of the stunters I had in the late '60's/early '70's were tailheavy. But I was almost young, and not long removed from the combat circle.

Steve

Randy Powell · « **Reply #18 on:** September 26, 2008, 09:26:59 AM »

Just as a note on 3 blade props: They tend to allow somewhat less sharp corners (sometimes, depending on the plane an conditions). This is generally outweighed by the increase drive above 45°. Apart from ground clearence issues (I guess), they provide better tracking in poor conditions. Sometimes you don't need that and the plane has plenty of power in high "G" maneuvers and in wind and so, the need for additional thrust is reduced. Or you have a plane that is resisitent to sharp corners (for whatever reason) and the 2 blade gives a bit better corner.

All this is to say that it depends on the plane. I use both with my current plane, depending on conditions. In high wind or turbulence, I tend to go with the three blade for the additional drive through the maneuvers and ability to cut through the wind (it's a pretty draggy plane). When it's calm or light winds and reduced turbulence, I usually go with the 2 blade for the additional corner. It also tracks slightly better with the 2 blade. It's all a matter of adating to conditions.

Joe Yau · « **Reply #19 on:** September 26, 2008, 02:08:26 PM »

Quote from: Steve Helmick on September 25, 2008, 07:12:26 PM

Huh! I think I may have seen The Varley with that particular plane. Never realized its relation to this one, tho, which I believe to be a fairly standard Magnum Plus out of the Danny Dirt stable.

yeah, I really liked what Keith has done with it. It sort of looks like a SV-11 or the Trivial Pursuit etc.

Steve Helmick · « **Reply #20 on:** September 26, 2008, 08:42:44 PM »

Joe...try the Thunder Tiger Cyclone 12.5 x 5.5 and see if you don't like the Cyclones a whole bunch!

Steve

Randy Powell · « **Reply #21 on:** September 27, 2008, 01:01:16 PM »

Steve is right. Great prop for a 50-65 engine.

Scott Hartford · « **Reply #22 on:** September 27, 2008, 06:48:43 PM »

Really good on a Saito 56 too.......

Bootlegger · « **Reply #23 on:** September 30, 2008, 05:58:30 AM »

Where do you get the cyclone props

john e. holliday · « **Reply #24 on:** October 01, 2008, 08:04:46 AM »

Try, www dot thundertiger4u dot com slash cyclone-props . Or google cyclone props. DOC Holliday

Joe Yau · « **Reply #25 on:** October 02, 2008, 10:13:25 AM »

Quote from: Steve Helmick on September 26, 2008, 08:42:44 PM

Joe...try the Thunder Tiger Cyclone 12.5 x 5.5 and see if you don't like the Cyclones a whole bunch! Steve

Steve,

What do these prop looks like? I don't seems to be able to find any pic of the Cyclone prop.

Steve Helmick · « **Reply #26 on:** October 02, 2008, 08:48:17 PM »

Joe...here's a pic of a 12.5 x 5.5 Cyclone. I also have 11 x 4.5 and 10 x 5.5...and they all look the same....pretty much like a Grish Tornado nylon, but a bit narrower blades, and grey. Don't let that bother you, they work real well, they're relatively thin, well balanced, etc. It should be easy to dye them black, should that appeal to your sense of aesthetics. I'm ok with grey, 'cause it matches my hair, maybe.

Steve

Joe Yau · « **Reply #27 on:** October 04, 2008, 11:33:19 AM »

Thanks for the pic.

Looks a bit like the Stalker CF props also. Are they available in 3 blades?

Steve Helmick · « **Reply #28 on:** October 04, 2008, 02:39:35 PM »

Joe...it seems that TT doesn't make 3 blade props, but maybe they will, eventually. I don't find them on the website, anyway.

Are the Modusa/Stalker props available again? If so, where?

Steve

Joe Yau · « **Reply #29 on:** October 04, 2008, 11:58:56 PM »

Quote from: Steve Helmick on October 04, 2008, 02:39:35 PM

Are the Modusa/Stalker props available again? If so, where? Steve

I think Keith gets them from Kaz Minato (MNT Int'l) in Japan.

Author Topic: 2 Blade Prop to 3... (Read 6021 times)

Alan Hahn