VESS prop

[JVDO]

Hi

I won a vess prop with my video in the fgvc...
But my question is what's the best prop for my 3W80 with tuned pipe?
(The engine from the video...)

please help me...

[Dennis C]

Im going to try a 26-c this weekend.i'll let you know how it works.

[SleepyC]

Give Robert a call, or he may even answer here, but from what I've been explained, you have to take n account the weight of the plane, and what motor you intend to use to get the best Vess prop for your project.

Any of the 26" props would probably work great, but there will definatly be one that will work better.
If you could post the weight of your plane, and your intentions (3D, IMAC) for the plane, I'm sure Mr. Vess could tell you the best combo!

[Jaybird]

Didn't know the 26" props were available. I would like to give one a try.

[SleepyC]

The TEST versions of the 26" props were out in August... I was trying to be smooth and snake one at the USRA giant scale races... but it didn't happen But Robert showed me one....... I'm sure they are out by now!

[RobertV]

Hello JVDO,

First of all, congratulations on your third place in the video competition. You did some great flying and great video editing. I enjoyed it, as did everyone else.

There are a few of considerations when selecting a Vess prop for your application. First, you have already mentioned that you are using a 3W80cc engine with a tuned pipe. Does that pipe add alot of power on that engine or is it mostly a muffler? What prop are you flying on it right now? Are there strict noise regulations in your area? I don't recall from your video but I think you were flying an Extra. What does it weigh?

First, you want to choose the diameter that suits your displacement. Generally, you would choose a 25-26" diameter prop for an 80cc engine. I actually do not have these diameters to the market quite yet. We have been testing and refining those sizes but have not committed to manufacture yet. However, I do have some pre-production test props and will be bringing those sizes out toward the beginning of the new year. But I still may have what you need in my test prop collection right now.

Let's say you would choose a 26 inch version for an 80cc engine. Then you have to look at how powerful that particular engine is with the exhaust system it has, etc. If the pipes add additional power (as they usually do), then you may consider that you need a little more prop "load" to absorb it at a reasonable RPM. The pitch of my props are quite non-linear by design. So I cannot call them 10" pitch or whatever since that would be misleading and not comparable to linear pitched props. So my pitch ranges are designated by the letters "A-B-C". "B" is a baseline or normal pitch for a typical diameter series. "A" has a little less load (pitch) and "C" has a little more. This provides you with the ability to fine tune to your particular application.

So now let's say that you start by considering a 26B. If you have a light Extra-type airplane (lower drag shape) that has a bunch of power with the tuned pipe, that prop might unload a little too much in the air and thus not put the engine in its' best power band while also being a noisy operating point. So you would then consider using a 26C. On the other hand, if you mostly fly 3D and seldom do high power passes (ie. know how to use the throttle carefully), you may like the higher revving 26B for improved throttle response. Or if your airplane is heavier than average and/or you fly at a high field elevation you may even require a 26A that would rev even more and give better pull out of a hover.

If you find that a 26 inch prop does not suit your application and give you want you want, then you can move into other diameters that suit your needs (like 25" or 27"). I have people around the country flying 27A's on 85cc motors and loving them! And I have others who are flying both 25" and 26" versions of the test props on various 80cc notors and they each love them in their applications. So, feel free to give me as much info as you can about your combination, the normal weather conditons and field elevation in your are, what noise considerations you have, etc. I try to provide you with a prop that will offer you the best compromise and the performance you are after! And what we post here might help others with their selections in the future.

Best Regards,

Robert Vess
Vess Propellers

[JVDO]

Thanks for the comments ... but if I understand right you don't have the 26 inch yet???

some more info...

weight 10.8kg
3W80CC
about sea level
the engine more then enough power for the plane :-) but offcourse it's always nice to have some more...
I fly Imac and 3D ....
I have to look at the noise they are verry strick about that right here...

[DesertHucker]

Hi Robert,
Would you be able to help me out?
I have been looking at your props for some time.
Now Ian from DA has then in Australia.
I have a new 3w106cs currently turning 6700rpm on a mejzlik 28x10 on the ground,
I fly a comp-arf 2.6m yak 12.7kg mostly IMAC and some 3d noise at this stage is no problem.
Local conditions are 360m altitude dry and hot 35-40dec
I would like to get this engine down to 6100rpm just above its power band.
I thought a 27c would be to light and a 30a maybe too much what do you recommend?

[RobertV]

	Quote:
	weight 10.8kg 3W80CC about sea level the engine more then enough power for the plane :-) but offcourse it's always nice to have some more... I fly Imac and 3D .... I have to look at the noise they are verry strick about that right here...

JVDO - You have a light (10.8 kg = 23.8 lb), low drag (Extra) plane with an 80cc motor and tuned pipe that offers plenty of power. And you fly near sea level so the density altitude is low. Finally, on BIG requirement is to keep the noise lower. So, for your slightly overpowered plane at sea level, I'd pick the Vess 26C. And fortunately, this prop has the most "load" of the series and thus will not unload excessively in level flight at high power. So it will be the quietest of the 26 inch props, too. And the best news is that, although the 26 inch props are not on the market yet, I have a 26C that I will provide to you as a "GSVC" winner!

[3w_flyer]

Robert,

I don't think a 26 inch prop is big enough for the 3W 80.

a KS tuned pipe adds around 30 % more power than any canister.

Most people over here fly this engine and KS pipe with a mezlik 28x10 prop and still get more than 6000 rpm out of it.

If I'm not mistaken, Jens is currently running a 3 blade 25x12.

Peter

[RobertV]

	Quote:
	I have a new 3w106cs currently turning 6700rpm on a mejzlik 28x10 on the ground, I fly a comp-arf 2.6m yak 12.7kg mostly IMAC and some 3d noise at this stage is no problem. Local conditions are 360m altitude dry and hot 35-40dec I would like to get this engine down to 6100rpm just above its power band. I thought a 27c would be to light and a 30a maybe too much what do you recommend?

DesertHucker,

Wow, your 3W106 is powerful to turn a 28x10 mejzlik at 6700 on the ground, especially for the hot days (35-40 C = 95-100 deg F) at that field elevation (360m = 1181 feet). So your density altitude is surely significant and thus performance should be degraded with respect to lower/cooler flying sites. But let's see what prop might help you. The first thing I can say is that we do not have the 28 inch diameter props on the market yet, either. But that's OK because I don't think you'll need one.

Your 102" (2.6m) span CA Yak is about 28lb (12.7 kg). That's comparable in size, shape, and weight to my Quique Yak (which may actually be closer to 27 pounds). I use a DA100 with MTW cannisters and mine was measured with an onboard data system to turn a 27A at about 6200 rpm at around 70 deg F the other day. And it gives this airplane unlimited vertical performance! If I was at your density altitude, my engine would probably turn 200-300 rpm less (down to say 5900-6000). So let's assume that your 3W106 turns this same prop at 300-400 more rpm than my DA100, which would now put you at 6200-6300 rpm with this prop. If you go up to a 27C that would bring you down close to 200 less rpm and put you near your goal of 6100 rpm on the ground.

But my philosophy is to judge prop performance in the air. You need to decide what you want from your prop and then test to see if it does what you want. On the ground, some of the blade can be stalled and the flowfield is not the same as in the air. Also, the prop will unload in the air, which is part of the design consideration. So what I like to have people do is fly their existing prop, land, change to a Vess Prop that suits their application, and refly. The two things that I commonly hear are, "this turns less RPM on my tach" and "wow it really pulls". I usually ask them to sustain a vertical line with both props and do rolls after they think the airspeed is gone. This shows if you have thrust and airspeed. If you want something to act differenctly, change to a different load prop and refly until it suits your needs.

If you want it to be quieter, add more load and/or reduce the diameter. If you want more rpm, reduce the load and/or diameter.

So, based on all that we know here, I'd say you should try a 27C. My intuition says that a 27B will be good, too, since you have a big round cowl behind the prop. I use a 27A now on my Yak for that reason and I like it alot (the 27B was good too but I like the extra rpm of the "A"). But I have to be careful not to hold in too much throttle with the nose low to keep the noise down (a considerate thing to do for sure) with this lower load prop.

I hope this helps you!

[RobertV]

	Quote:
	Robert, I don't think a 26 inch prop is big enough for the 3W 80. a KS tuned pipe adds around 30 % more power than any canister. Most people over here fly this engine and KS pipe with a mezlik 28x10 prop and still get more than 6000 rpm out of it. If I'm not mistaken, Jens is currently running a 3 blade 25x12.

WOW! If he's presently turning a 25x12 3-blade comfortably, then I'd agree that his 3W80 is quite powerful with the full-length KS pipe. In that case I'd recommend a "27B" or even a "C" instead of a "26C". You're making power like a good 100cc if you can turn a 28x10 at 6000+! I realize the importance of tuned exhausts on a two-stoke engine, they have been less popular in the US than they apparently are over there (now with bigger noise concerns and groundbreaking rules at events like the Don Lowe Masters, this will change). So I obviously have less experience with such applications and am quite intrigued by the possibilites!

It's also going to be hard to match the low noise that you can get out of a 25 inch diameter 3-blade with a 27 inch two-blade wood prop. But the performance increase should show for sure and with careful throttle application, the noise is manageable.

Thanks for the insight!

[3w_flyer]

Over here you see more and more an increase in pitch instaed of diameter. As You already mentioned, increase of diameter results in more tip speed and therefore more noise.
As you see the new modern planes have more drag build in, you don't nessecairly need low pitch, OK it is still nice for torque but for flying you see more often now people switch back to 12 or even 14 pitch.

My friend had a seyer 2 blade 32x14 on his DA 150 and it is a killer prop to fly. this on a 20kg extra, no problems to fly away from a torque.

Any plans of Vess props making 3 blade props ??

Peter

[RustyTumbles]

Robert,

I am looking at putting a vess on my new extra which is powered by a DA50 and MTW75 canister, weighs 17.5lbs. I have a 22B on my ultimate which works very well for that plane. My question is will the 22B suit the extra as well? or can I step it up to a 23B for more downline braking and an some extra punch in the verticles?

[RobertV]

3W - I think you guys are ahead in the quiet airplane arena and we are learning to do the same...maybe more slowly. My props have more average pitch than the usual constant pitch props in use. This comes directly from the design process. You'll see when you look at whatever prop Jens gets. Also, there WILL be Vess three-blade props in the future.

Rusty - Your DA50 will certainly turn the 23 inch props fine. So the question is if you want the "A" or the "B". If climb out of the hover and downline braking are your main goals, I'd use the 23A. Tip noise isn't really a problem for these diameters so use what will give you what you're after.
Send me some good pics of your planes with Vess Props to use on my website!