In general 3-blade props are used to reduce the noise footprint, but at a slight cost in performance. They do look cool.

In my experience you loose at least 20% performance going to a 3 blade. When you have a pipe setup you might break even. I had to use them for noise last season and I am going to back to canisters to use 2 blades. In IMAC 3 Blades have a definite place, but they are liabilities in 3D due to spool up and smaller disc area.

Good info, thanks. I have no experience with 3-blades, so I guess the question is, will a 25x12S 3 blade Mejzlik deliver more power than a 2 blade 24x10 Laminated Xoar spinning at the same RPMs? I measured Frank's DA60 with the Xoar pulling 40.37 pounds, so that's impressive considering he only has 14 flights on it so far with the RE-2.

Anyone know about this? I do know the 24x10TH 2-blade Mejzlik spinning the same RPMs as the Laminated Xoar (6420 to 6500) only pulls about 33 pounds on my scale. The 24x12 PJN Xoar (electric) will do 37 pounds at 6350.

only if you were grossly under propped, when you go to a 3 blade prop you generally need to go down at least one size. as for what pulls more the three blade equal to the 2 blade will show a performace loss only for the really high performance group(mostly 3ders)

Jim,
I think you have to compare apples to apples.

Xoar and Mej 24x10 prop but on the same motor (in this case Franks DA60 and pipe) to get any real confidence.

It has been shown before that electrics tend to make their most torque down low and peak out near the top of the rpm's where as gas motors it the reverse. As the rpm climbs so does the torque they can achieve.

I would be interested in the Xoar versus Mej 24x10TH comparison myself.

Many flyers prefer the Mej or Vess Stealth over the Xoar wood equvalent and I thought it was related to thrust from the carbon props.

Sure the Xoar will probably spool faster due to its lighter mass, but I am surprised to think it also generates more thrust.

Also,
on Franks rpm, I am surprised it is so low.
I thought many have also reported getting 6800-6900 rpm out of the DA60-RE2 pipe combo. Is it possible to get higher as the motor breaks in further and gets leaned out a bit further?

Originally Posted by furballll

only if you were grossly under propped, when you go to a 3 blade prop you generally need to go down at least one size. as for what pulls more the three blade equal to the 2 blade will show a performace loss only for the really high performance group(mostly 3ders)

Right, but the comparison here is between a DA60 swinging a 24x10 2-blade, and a DA70 swinging a 25x12 3-blade to the same RPMs.

The real question, I guess, is will the DA70 have any application for the 91 EXP's? I'm not sure a 26 2-blade will safely clear the runway so one alternative would be a 25 3-blade, but not if it does not mean a direct increase in power from the 24x10 pulling 40 pounds on the DA60. Then there's no sense for the added investment and weight, unless it is just incredibly smooth.

sorry i missed that last post on the previous page. have we been told what the BHP of the da70 will be yet and if so how much of an increase over the 60 is it?

if its able to swing a 26 inch prop than a 25 should be ok in a 3 blade but you may have to go to a 24x12 or 24x10

Originally Posted by bigroger

Jim,
I think you have to compare apples to apples.

Also,
on Franks rpm, I am surprised it is so low.
I thought many have also reported getting 6800-6900 rpm out of the DA60-RE2 pipe combo. Is it possible to get higher as the motor breaks in further and gets leaned out a bit further?

Yeah, I think my point was overlooked on the previous page... the comparison here is between the DA60 turning a 24x10 Lamimnated Xoar, and the DA70, which, from worthy sources, is supposed to be able to turn a 25x12 3-blade to virtually the same PRMs.

The reason for the question is to find out if there is an application for the DA70 in the 91 Extra or Yak. I don't think a 26 2-blade will clear on the plane, but it seems a 25 should. If so, is a 25x12 2-blade going to deliver more thrust than a 25x12 3-blade?

And, yes, I suspect Frank's RPMs will increase a bit, but the Laminated Xoar is a heavy prop in comparison to the Vess or even other Xoar props.

The comparison between the 24x10TH Mej and the 24x10 Laminated Xoar at equal RPMs is a sound comparison, regardless of the power source used to bring them to the same RPM. They were both mounted in a plane and the same scale was used to measure them.

[QUOTE=Aeroplayin;24108491]Yeah, I think my point was overlooked on the previous page... the comparison here is between the DA60 turning a 24x10 Lamimnated Xoar, and the DA70, which, from worthy sources, is supposed to be able to turn a 25x12 3-blade to virtually the same PRMs.

yes no doubt about it then. your swinging way more prop at the same rpm it has to push more are ie. thrust

No worries Jim,
quit interesting that the Xoar has more thrust than the 24x10TH?

But I did a bit of research on FG today and seems the laminated Xoar is renowned to pull more and spin lower rpm the equivalent Mej or Vess carbon props. So my statement/questions above have sort of been answered to a degree.

I wonder how the Vess Stealth would run on Franks plane and what Tom would rate it by comparison?

For the DA70, would you need to go up to 25x12-3 blade or would 25x10-3blade be enough load to slow the rpms down and give more thrust on the twin 70?

I hear ya on the DA but cost is a factor the DA 60 will cost about $400 more with pipe. than a EME60. I have been watching the EME thread very closely. So far reports are very good.

I am still holding out on the motor purchase for that reason though. I wan to give it as much time as possible to hear some of the bad issues.

400.00 more but the DA-60 will probably be the last 60cc engine you will ever buy - unless you want a 2nd or 3rd 60CC sized airplane.

MLT

Originally Posted by bigmoebbq

I hear ya on the DA but cost is a factor the DA 60 will cost about $400 more with pipe. than a EME60. I have been watching the EME thread very closely. So far reports are very good.

I am still holding out on the motor purchase for that reason though. I wan to give it as much time as possible to hear some of the bad issues.

+1... I'm wanting the DA60, but I'll probably go with the EME. The DA60 is a bit out of my budget...

Originally Posted by bigroger

No worries Jim,
quit interesting that the Xoar has more thrust than the 24x10TH?

But I did a bit of research on FG today and seems the laminated Xoar is renowned to pull more and spin lower rpm the equivalent Mej or Vess carbon props. So my statement/questions above have sort of been answered to a degree.

I wonder how the Vess Stealth would run on Franks plane and what Tom would rate it by comparison?

For the DA70, would you need to go up to 25x12-3 blade or would 25x10-3blade be enough load to slow the rpms down and give more thrust on the twin 70?

Thanks for doing the leg work, Roger... I know that Daniel has tried different props and is waiting for the 24x10TH Mej from DA now, and Frank's should arrive today or tomorrow, so the comparison should come soon, The only issue with Vess is that they are a bit loud, and there are only certain events we go to where noise is not an issue. It is at our field. The vid of Tom flying over the camera with the 24x10TH on the Hacker is all prop noise, and it's great.... sounds like a throaty turbo, so prop noise to 6800 RPMs should not be an issue at the same RPM, but the pull will be less. The real test would be to get both props pulling the same thrust numbers, and then take a dB reading.

As for the EME, Taildragger seems to be hands-on, straight-up company and the early reports are good. I still wish I had gone with DA the first time around with a gas engine, because, like MLT said, it actually would have saved me money, and a ton of aggravation. You can load a DA up until you bring the RPMs down, and it will pull like a mule. The other engines I've had need to be propped down, and spun up, like a 2-stoke glow, or they would quit in the air no matter much you fatten them up. And, of course, there's that ring thing. The firs time I took my DLE apart, the ring fell off the piston in three pieces. Guys were talking to me like I should have known that.

In this hobby, it's live, learn, or pay a higher tuition. But the guys at Taildragger seem to be hands-on, stand-up guys, so I hope the experience is better, for those going that way.

Granted there is not much to these 2 stroke engines and if your even slightly mechanically inclined and have a few key tools, you can tear them down to replace rings, bearing etc. However, if you want a "plug and play" type engine that will consistently give you same reliable performance EVERY single flight and is backed by the best Customer Service you will ever see - Get a DA.

If the only think keeping you from enjoying an awesome Extreme Flight Giant Scale plane is the extra $$$ - then go with DLE or EME.

MLT