Since the question of which prop is best seems to pop up on just about every thread, I thought I would start one that is dedicated to which prop is used on which engine on which plane... AND SO ON

Ok, here is what I have used so far.

I have a brillelli 40cc on a Wild Hare 73" Edge 540. I have only tried two props so far. The third is on order.

1. Top Flite 20X8 "Power Series" WASTE OF MONEY
2. Zinger 20X8. This prop is alot better than the Top Flite. I would say that for the average flyer, this prop is fine for the most part.
3. ON ORDER.. I ordered an Xoar 20X8 and with any luck I will get to fly it this weekend and post results.

The thing about the props I have listed above is that they are all around $21. Equal in cost but NOT performance.

I feel that info of this nature will be a huge help to those that are not sure what prop they should get or those that do not believe that one prop is any better than the other.

Travis

There is one more prop I'd consider in that price range. I've seen many people recommend it for the EVO26 along with the same company's Carbon Fiber tuned pipe. It's Ed Skorepa at escomposites.com. His wooden props are supposed to pull very hard. It'd be great to see it up against the Xoar, so tnorris, since I've got a Brillelli 40 coming, I'll get both the Xoar and the Escomposites prop for it and if I can figure out how to test the pull, I'll let you know. About the only testing I can do is to use my fish scale, unless there's a better way to use what I already have.

Any 20" diameter prop with 8" of pitch becomes horribly inefficient very quickly as forward speed increases. Propeller blades must be as thin and stiff as possible for best efficiency at these low blade angles. That is why there is such a large difference between thick wood props and thin composite props. If we were able to make use of 20"x14"s the differences between blade styles and materials are far less. A move in that direction will lower 3D performance and make our planes much quieter, and nobody wants that.

Tnorris,

I just installed my 40GT engine on my Giles-202. I have a APC 20x8 sport prop and with only 160z of fuel run the the engine I am getting 7020RPM. That sould be in the neighborhood of 18lbs of thrust. THustHP says 23lbs, but we know how wrong that is. Here is a pic.

Sorry the pic did,nt take. Here is is again

as for Zinger, I will never buy another one because I can buy a 3W for only $2 more, "that's money well spent !!",,,

the Zingers I have bought have been way way off on balance while the 3W was just about balanced right out of the bag, plus the 3W is stiffer at the tips and have a much better finish !! (both props are 20x8 with the same tip profile),,

the Zinger will look cool on the wall..

Jim

waterboy,

That would be cool if you can give numbers on that Ed Skorepa prop. I have never heard of that one. Your fish scale method is about as good as anything I would think.

jstanton,

I knew that the APC would spin faster, but according to what Scott said, the Xoar spun slower but had more pull, but 18lbs of thrust on a 12lb airplane is not too bad at all.

kweasel,

Yeah, the low pitch props are definently for slow flying. If I knew that it would work I would switch to something like a 22X6 or X8, just so that I could more airflow over the control surface and super slow speeds. I just do not think that the 40cc could handle a 22" prop.

the wasp,

I have never really been a fan of the Zinger props. Well not in my smaller glow anyway. It seems to fly my plane pretty good so far though, well compaired the the Top Flite anyway I will have a real prop in a few days with any luck.

As soon as my Xoar get here, I will run each prop and see what the thrust is and post images of what the scales show for each one. That will get some real work numbers out there for those like me who cannot make a final decision without real data. Must be all these years woking around engineers!!

Thanks for all the input guys.

The fish scale method of measuring thrust works very well. Just be extremely sure that the scale and connections will hold the plane at full power. A 50 pound scale should be enough. A good idea would be to have a few guys over to be ready at the wing tips in the event it started to get away for you. Do all your measurments and calculations from behind the plane and have a good clear overrun area in the event something goes wrong.

RPM by itself means nothing. High thrust at rpm levels that max below the manufacturers operating range are destructive and cause early engine failures. Look for max thrust levels in an rpm range that is favorable to the engine. Something interesting will be to check thrust levels at relatively low rpm. You'll find you will be operating in that range more often than you think and the most efficient prop will be a blend between a strong high and low.

The fish scale on the tail method is very close to accurate. I tested a Xoar 22x8 on my ball bearing slide test stand on our 60. It pulled 28lbs 8oz. When we mounted the same 60 on a 1/3 scale Christen Eagle I tested it again with the same scale. It read 26lbs 4oz. It was also about 10 - 15 deg hotter than when I tested it on the stand so that accounts for some of the drop, plus all the frontal area of the biplane took some up as well. All and all I think the scale on the tail is FAR more accurate than that Thrust HP program. It is so far off it is usless. It is because of that program people think they need a 2:1 thrust ratio for good 3D. I think tnorris's plane is good for 3D and it is not close to a 2:1 ratio. On my stand that engine pulled 15lbs 8oz with a Mejzlik 20x8 prop.

edit,,, I was asking where to buy the Xoar props, but I found them at Chief..


Jim

Yeah I'm thinking that even if the "official" total thrust is not exactly the same as what everyone is getting, all else being equal, I'm looking for the difference in thrust between props. That'll tell me which is better. There will be slight differences between airframes and motors, but for a given prop size we'll know the difference.

Be careful in the whch prop is better based upon total thrust decision. Eventually you're going to find that two different props that are very similar in total thrust output can have extremely different flight characteristics. Both may pull at the top of the rpm range like crazy but one will provide a lot better mid range pull. One may provide better airflow than the other over the surfaces. One may have a whole bunch better pull at very low flight speeds. All from two props that are the same at max throttle.

That's why so many have stated that the way the prop performs on any given airframe should be the final qualifier for what's best for a given plane/engine/weight/flight style combination. The numbers by themselves do not provide all the data needed to make the final decision, and still requires some experimentation after a few prop choices have been selected that might fit the need.

Tnorris,

I test run the 40GT engine agian this morning and with a APC 20x8 prop spinning at 7100 RPM I am getting 17lbs 10 oz to 18lbs of thrust using the digital fish scale I have. The RPM went from 7020 to 7100 with just another 16oz of fuel run thew the engine. ABellRC insured me my Xoar props will be shipped this week. I will test them once I get them here