Originally Posted by the Wasp (Post 12340692)

I'm not trying to fight with you !! I understand that a Drag Race is different, I used-to street race back when a Muscle Car was a Muscle car not a Race Car, I was just making a statement to show a relative to over revving in the air,

as for your statement about over revving in flight at 10,500 and 11,000 "THAT is over revving",, (note that there is a 2,200 RPM difference between the number I used "8,800" and 11,000 that you pointed out for Over Revving),, to me, I don't find 11,000 overly excessive in flight (that is if the reports are truly accurate), look what Saito themselves says in the link, their 180b engine will turn an APC 16X8 at 9300, well you have 3 choices for that number,
1) Peak Static Number for that Prop
2) Tuned for Flight Number, for that Prop
3) an Over Revving Number in Flight for that Prop

So, is Saito suggesting that you tune your Engine with an APC 16X8 to turn 7100 for Flight on the ground so it will unload to a peak of 9,300 in the air, I don't think so. even if Saito is suggesting that 9,300 is a Peak RPM and you should tune around 8,800 for Flight, again it will unload around 10,500 or 11,000 as you say people have reported,, in the link below Saito suggests for a Peak RPM up to 10,000 and I think that is a Peak Static Number,, so we know that 9,300 with an APC 16X8 is a Peak Static Number for that Prop and we should tune a bit below that for flight,

to add, if you think 11,000 is Over Revving in the air, why is Saito saying you can turn a Prop as small as an APC 15X8, I'm betting an APC 15X8 will turn up around 10,000 Static, tuned at 9,600 for flight will git you over revved to 11,800

https://www.horizonhobby.com/product/storefronts/airplane-engines-15042--1/saito-engines/180b-%28new-case%29-aac-w-muffler%3A-bk-saie180b

don't hate me because I'm beautiful, hate me for my opinion

Jim

Originally Posted by airraptor (Post 12340693)

I think its funny a guy that estimates his in flight rpm and tells another guy that has telemetry showing real in flight numbers that is over revving the engine.
To Brian the OP start with the 18x6 get some flights on the plane and then try some other props and see what you like. Sometimes a big low pitch prop doesn't climb the fastest. What I mean by that is if you have a normal big plane like say cub a prop in the 6-7 inch pitch range may climb better than a prop with a 4-5 inch pitch. The plane will fly faster on the large pitch and climb better as it climbs on the wing. Look at the weight lift competition planes built by colleges and most are in the 5-7 inch pitch range on direct drive engines. One other thing to look at here is your flying style is different from everyone in here so find the best prop for your plane and your style and enjoy.

Talking about your mustang and how to shift it from 3rd to 4th, how does that help the OP?

Originally Posted by blw (Post 12340708)

Telemaster- the math works against what you are saying, plus I think your gravity concept errs too since it is only pushing down on the bullet and not opposing travel.

The prop efficiency formula, which leads to prop performance, contains velocity and Velocity. One is what we call static thrust, so you can see that static thrust is only half the story. The other velocity is all the air being rammed through the prop disc area by forward airspeed. The hovering example is valid and is only static thrust. Plus, you have some rotary wing aerodynamics robbing the prop of thrust. The main thing is tip vortices and the other is ground effect when close to the grass.

Originally Posted by the Wasp (Post 12340985)

gee, if an APC 18x8 unload's and over revs in the air by 1000 RPM, and Saito recommends a prop as small as a 15x8, I have to wonder how much a 15x8 would over rev in the air

Jim

Originally Posted by airraptor (Post 12341016)

. I have run many of my saito engines over 11,000 on the ground with no issues in the air and I have run them on 55% nitro too.
.

Originally Posted by the Wasp (Post 12342801)

I don't know,,, could be,,,, although Saito's Home Page also suggest the same prop size

http://www.saito-mfg.com/single-file...80foreign.html




no-p, not to me, as I said a few people have reported that their Saito 180 pulled 8,800 to 9,100, I'm sure a 15X8 would rev up higher, I'm betting closer to 9,600,, 9,800, ,, again, I'm just wondering how much a 15X8 would unload in the air

Jim

Originally Posted by blw (Post 12343288)

And there you have it, Jim. You're left wondering. If it's a good engine I would start with using 1500 RPM as a buffer and see how it does in the air. You should be able to hear what sounds like 1000 or 1500 RPM.

Originally Posted by the Wasp (Post 12343419)

Lol

Originally Posted by the Wasp (Post 12343960)

the OP received suggestions on 5 or 6 props, and he got Static RPM numbers his engine should produce for those props, and he received even more related information about props,
I feel he was informed well

Jim