Negative pitch naturally stronger than positive?

[kronium]

Originally Posted by apper001

Same here, negative stronger than positive also in simulators like accurc

The Phoenix model I use seems equal as well which throws me off when I try to translate that into actual flight.

[RC/DC_5000]

I also found this diagram from Art of the Helicopter (picture #1). Another free read on Google. It shows how the velocity of air is greater beneath the rotor. This picture says it all. The fuselage blocks the important air one way... and it doesn't block the air the other way.

Take the surface area of the disk, and subtract the surface area of the fuselage. You are degrading that much accelerated air. Hence the difference in sound with the movement of air... hence the difference in feel on the collective. The fuselage takes up a considerable surface area of the disc. (picture #2) I'd very generally guesstimate that you lose about 1/3 of the surface area of the disc to the fuselage.

When its inverted- you're getting the most bang for your rotational buck out of the disc. This same concept we are talking about is why "speed fuselages" help so much. They make the down wash air more aerodynamic over the fuselage. (and they also help with wind speed).

[jgiannakas]

The down wash pattern is like the pic below:

Hence the role of the fuse is much less than you think. Especially in a pod and boom heli where the boom barely takes up any space

Speed fuselages are used to make the heli aerodynamic in forward flight.

[kronium]

Originally Posted by jgiannakas

The down wash pattern is like the pic below:

Hence the role of the fuse is much less than you think. Especially in a pod and boom heli where the boom barely takes up any space

Speed fuselages are used to make the heli aerodynamic in forward flight.

Still probably enough to see a difference though. And aren't most pro 3D flyers using speed fuselages now? It smooths air flow around the boom and canopy in all directions.

[James Recard]

Horizontal stabilizers often have me scratching my head..... they are usually in the highest pressure zone.

[jgiannakas]

Originally Posted by K-rash

Horizontal stabilizers often have me scratching my head..... they are usually in the highest pressure zone.

They are cosmetic - the fin is too small to actually have an impact (if I look at my 450L). Also the goblin doesn't even have one

If they did have an impact it would seriously confuse the head holding ability of the flybarless unit to hold an FF attitude.

[RC/DC_5000]

Yea for sure. The speed fuselage is not just for frontal aerodynamics. In FFF, frontal aerodynamics intermix with the downwash. The nose is down, disc intakes air and blows it at more a 45 degree angle back over the fuselage. This is how it flies forward. By blowing air backwards. That should make good common sense.

jgiannakas, you're only looking at the downwash from one perspective, head on.... an impossible frozen moment in time. Take your diagram and place the helicopter fuselage from left to right, broad side. It is the exact same thing.

You do realize the blades in your diagram are spinning right? So if you look at the helicopter from the fuselage length side- its hitting it all kinds of crazy.

Perhaps you have a little confirmation bias... but for not seeing that, I'll have to retire from this thread.

[Russell Harding]

Originally Posted by jgiannakas

They are cosmetic - the fin is too small to actually have an impact (if I look at my 450L). Also the goblin doesn't even have one

If they did have an impact it would seriously confuse the head holding ability of the flybarless unit to hold an FF attitude.

They were needed on some flybarred models back in the day... Look at old Hirobos, there is a reason they have big, solid H and V stabs on them... They also didn't fly 3D like we do today.

And personally I wouldn't say 'all the pros' are flying full fuse... but the Goblin style has really caught on overall... I think it is more aesthetics than anything. Modern helis are so overpowered we can afford to have a touch extra weight around. The drag from full fuse and/or goblin tails is piro performance can be uneven at high speed (think kyle dahl's piro funnels - performed on non-enclosed tail machines)

[fastblackbird1]

Originally Posted by frankiexp2

im sure gravity has something to do with it

I'm agree with

[kronium]

Originally Posted by fastblackbird1

I'm agree with

Why?

[RC/DC_5000]

I have a fuselage 630 and a boom and pod 600. Both helis have the same collective pitch range of 13 degrees. The boom and pod 600 has a monster power setup with a clear 1000 watt advantage in the CC logs over the 630 fuselage and a 2500 HS vs 2160 on the Goblin. But the fuselage helicopter is MUCH faster and the speed is effortless. It hauls the mail just barely off center stick collective. Whereas the greatly overpowered 600 is digging hard into the collective pitch range to go that fast.

Its hardly cosmetic. If you had them both, you'd think otherwise. Here's a basic picture of what the windspeed does over the fuselage in FFF and my helis. One is very aerodynamic- the other is not.

Contrary to intuition- a small round pipe is not aerodynamic. Thats about as aerodynamic as a bus. The wind wraps around it and hits itself, slowing down. Like as a kid whips a branch through the air- it makes a very loud noise. Though he likes this noise, that's called drag. (The branch is the boom pipe). Aerodynamic is something that breaks the wind (giggle) and directs the wind back the same direction it was going. Like a very smooth and well shaped fuselage. Instead of three little pipes and a bare frame.

If you're interested in more about aerodynamics, you should read about the Notar tail system from the McDonnell Douglas. It will blow your mind how sensitive aerodynamics are. That helicopter blows a little bit of air under the tail boom- and turns the downwash air into counter torque thrust. Just from the airs tendency to follow the path of aerodynamics. If a real helicopter can channel downwash aerodynamics (using the tail boom) to create counter torque thrust to help it fly without a tail rotor- what can it do for your helicopter?

That question also applies to what that downwash air can do when nothing is in its way to slow it down. Like when its inverted. The downwash air makes it hover, ascend or FFF at 120 mph by pushing air faster than the air is coming in. The aerodynamics in the downwash air is critical.