Aeroworks 35% Edge 540 ARF-QB

[flatspinjim]

Hot diggity!!
Those BME's are starting to impress me, might have to put one on my Extra. Mark's 58 ran really nice the other day, just needs to get the cooling dailed in.
Maiden on saturday??

[almmendes]

	Quote: Originally Posted by flatspinjim
	Hot diggity!! Those BME's are starting to impress me, might have to put one on my Extra. Mark's 58 ran really nice the other day, just needs to get the cooling dailed in. Maiden on saturday??

Saturday??? Come on... he has the engine.... he will have the maiden tomorrow 7am...

Just kidding. Looking really good Jim. Maiden Sunday?

[flatspinjim]

I thought the plan was for Cory, me, and Antonio to maiden it saturday? I want to see a tail touch!!

[BTerry]

	Quote: Originally Posted by MikeC3D
	That problem isnt necessarily the ailerons....more likely the prop choice and maybe weight(somewhat). On my 40% yak with 170, I use a mejzlik32x10 prop and my plane weighs 36lbs, it is next to impossible to hold it from TR, and these ailerons are huge, but I tried my buddies 30x12 and it doesnt TR bad at all. No other changes except prop. It also cured a couple other problems too, I think i may even try the 30x13 next.

This stands to reason. The "work" accomplished by a propeller is a related to the sum of kinetic energy related to the air it moves. Using the following assumptions:

• Kinetic energy is related to the MASS and the VELOCITY of said air.
  
• The air in our case is not compressible, it acts as a fluid, and the "MASS" of the air is related to the volume of the air. (Not entirely true, there are compressibility effects near the tips of the prop, but on the whole the fluid mass can be viewed as incompressible).
  
• The KINETIC ENERGY required to cause an airplane to hover is equal to the mass of the plane plus losses.
  
• The VOLUME of the air is obviously related directly to the DIAMETER of the prop.
  
• The VELOCITY of the air is related directly to the PITCH of the prop.
  
• There are two ways to increase the KINETIC ENERGY generated by the prop, either increase the VOLUME of the moving air, or increase its velocity. Conversely if we decrease the diameter of the prop (reducing the VOLUME) but increase the pitch (increasing VELOCITY), we can theoretically generate the same total thrust at the same engine power output setting, while benefitting from the increased air mass velocity.

Now, when we look at the aileron we notice the roll force generated by the aileron also depends upon the kinetic energy of the air moving over it, the deflection angle, and the length (chordwise) of the aileron.

• If we hold the length of the aileron constant, then the VOLUME of air interacting with the aileron remains constant.
  
• If the length of the aileron is constant but we increase the VELOCITY of the air over the aileron, we can generate the same rolling force using a smaller deflection angle, or generate a larger rolling force with the same deflection angle.

Now take all this info into one whole. If we decrease the diameter of the prop and increase the pitch of the prop we can see an equivalent THRUST at an equivalent crankshaft power output level due to the higher VELOCITY of the air mass. The aileron will see an equivalent volume of air move across it, but the higher VELOCITY of the air mass will in turn generate a greater rolling force at the same deflection angle.

The other benefit I see is the smaller diameter props will spool up faster (and are lighter) than the larger diameter props.

That said, my favorite prop for my 80cc is a 26x12. Tons of thrust but at a higher velocity than the 27x10 Mejz. The plane is faster of course, but is actually much quieter in the air for IMAC stuff. Hovering, etc, occurs at a lower throttle setting and the control surfaces are more lively at slow speeds.

Sorry to butt in here I just had a clarifying moment and wanted to write it down so I don't forget it later. Does this make sense to anybody?

Edit: I neglected to mention that the smaller diameter prop will generate less torque on the airframe. So using the smaller diameter, higher pitch prop leads to less torque on the airframe AND greater aileron effectiveness...

[BTerry]

P.S. I love those BME's, and think the new Aeroworks planes look fabulous!

[flatspinjim]

Brett, your posts are always welcome and contain good info. We were discussing this at the field the other day. Would a 26/12 work better on a 100 than a 27/10? There were a lot of differing opinions. Props always depend on flying style But some well known pilots swear by it.

[BTerry]

I remember Reza reallly liked the 26x12 on his QQ 101" Yak with the DA-85 and the RE3 pipe.

Of course it will depend on the plane. Generally speaking a draggier plane (like a biplane) will do better with a larger diameter/flatter pitch prop. The problem arises when the prop is so large in diameter that it pushes the engine below the torque curve, or if the pitch of the prop doesn't generate enough velocity to keep the plane flying.

Again it depends on the engine, prop, and pilot's preference. It is a balancing act to keep all these factors in line! Sometimes it is counterintuitive, as MikeC3D found out going from the 32x10 to the 30x12 prop.

p.s. my brother has an OLD SCHOOL Aeroworks 106" Edge (maybe 8-9 years old). It is "heavy" by todays standards but it just flies perfectly. It does rolling harriers on autopilot. I know this new one (with an additional 9 years of engineering tweaks) will be fabulous.

[Hammbone]

I agree, you're not butting in at all. These forums should be a place for us to exchange information and ideas.

Thanks for your input,

Jim

[Hammbone]

O.K., I've got my spacer block made up.

I don't like standoffs. I would much rather have the engine mount supported all the way around. I think this makes for a more secure installation, and I think it reduces vibration. It also helps to keep from compressing the firewall in 4 small areas (like you would with standoffs).

This is what I like to do:

Jim

[ben_beyer]

What did your wife think of an airplane hanging in your house Jim?

[Hammbone]

I weighed my spacer block and compared it to the amount of aluminum spacers (that came with the plane) that it would take to get the same spacing. You can see the results below.

Jim

[Hammbone]

So, it cost me 1/10 of an ounce to have a sturdier engine mount that will reduce vibration. I'll take that any time.

Jim

[Hammbone]

	Quote: Originally Posted by ben_beyer
	What did your wife think of an airplane hanging in your house Jim?

Hi Ben.
The wife's at work, so she doesn't know what's going on.

She's seen it all before though. She's used to it by now.
She's a good sport and supports me being involved in this hobby.

Jim

[ben_beyer]

	Quote: Originally Posted by Hammbone
	Hi Ben. The wife's at work, so she doesn't know what's going on. She's seen it all before though. She's used to it by now. She's a good sport and supports me being involved in this hobby. Jim

[flatspinjim]

Spacer looks nice Jim. What length did it end up being?