Effect of Temperatures on the Rotor Blades.

[DennisFetters]

You should find this educational;

https://www.berkeleyscience.com/airplane.htm

Heres a snip;

The Motion of a Rigid Object
Think of a baseball thrown by a pitcher: as it travels toward the catcher, the ball 'as a whole' is moving in a more or less straight line, but, the ball is also spinning, so that at any instant each point in the ball is travelling at a different speed and a different direction than all the others! Fortunately, it is possible to decompose the motion of a rigid body into two parts, the motion of one point, the center of mass, and the rotation of the object about its center of mass. Thus, we can accurately describe the motion of the ball by specifying at each instant the location of the center of mass and the rotation of the ball about its center of mass.

To specify a rotation in 3-dimensional space it is necessary to specify an axis of rotation as well as the amount of rotation. The axis of rotation can change from moment to moment, and it is a tricky business to keep track of it. However, if we restrict the motion of our airplane to two dimensions, x (forward/backward) and y (up/down), then the axis of rotation will be fixed (the z axis), and we can specify the motion of the plane by specifying the motion of the center of mass and the rotation about the center of mass expressed as an angle.

If a force acts on a rigid body, and the direction of the force is along the line throught the point of application thru the object's center of mass, then it will cause the object to accelerate according to Newton's Second Law of Motion, and that's it. However, if the force is not directed through the center of mass it will also cause the object to rotate. Suppose the center of mass of the object shown to the left is at point p, and a force f is applied to the object. This force will cause the entire object, including point p, to accelerate according to Newton's Second Law of Motion. The force f also produces a torque at point p and an angular acceleration about p according to Newton's Second Law for rotation, which is
a'' = T / I
where a'' is angular acceleration, I is the object's moment of inertia about its center of mass, and T is the applied torque. If there are no other forces acting on the object it will tumble, as shown below.

An object's moment of inertial depends on how the object's mass is distributed about the center of mass. We will assume that the plane's center of mass is located 1/3 of the way back from the nose, and that the plane's moment of inertia about this point is given by 1/20 * m*L2 where m is the mass of the airplane and L is the plane's length (for a discussion of moments of inertia see Common Moments of Inertia)

 

[C. Beaty]

The only situation where the gravitational field may not be uniform is with lopsided interplanetary objects. Then it is possible for C of G and C of M to be located at different points.

We’re discussing celestial objects?

 

[Rotor Rooter]

If it looks like a pissing contest, and it sounds like a pissing contest, and it smells like a pissing contest, then it is a .............​

 

[DennisFetters]

The only situation where the gravitational field may not be uniform is with lopsided interplanetary objects. Then it is possible for C of G and C of M to be located at different points.

We’re discussing celestial objects?

No.
Because in an aircraft you can achieve attitudes where gravity is not effecting the aircraft, therefore (depending on the empennage not interfering) all motion rotates around the Center of Mass, and that, you moron, is the bases of your CLT gyroplane.

Thrust is a part of the aircraft, gravity is not. The aircraft reacts to where the thrust line intersects the CM of the aircraft, and can do so with or without gravity.

Chuck, you need more hands-on experience, I can see that now.

 

[DennisFetters]

If it looks like a pissing contest, and it sounds like a pissing contest, and it smells like a pissing contest, then it is a .............​

Hi Dave.
This is some pretty basic stuff that looks like it needs to be presented.

I was asked to explain, so I did. But Chuck can't let being wrong go, so I have to keep explaining it. I know, Chuck and his groupies will never change, but I believe there are a few people here that are seeing the right and wrong of it. After so many years of being taught the wrong way, there is always some resistance and caution, even if it's now the right way. I know you can understand that.

 

[Mike Schallmann]

This may help clear up th CG/COM question

https://hyperphysics.phy-astr.gsu.edu/Hbase/cm.html

 

[C. Beaty]

But Mike, that’s for a uniform gravitational field. Someplace in the cosmos, the gravity field may not be uniform.

Physicists prefer center of mass; others use the term center of gravity interchangeably.

 

[Mike Schallmann]

Is that kinda like wind gradients here on planet earth????????lol

 

[Fl90]

Let's keep the sh!t on track, the COM and COG issue was on another thread, and associated with FAA terminology for weight and balance....who cares.

Back to the light and heavy blades. Normally I read this for entertainment, but I am in a position to use some of this information, NOW.

I've flown heavy blades with a descent airfoil, and light blades with a roughness average of popcorn ceiling finish. I've also flown light blades with an efficeint airfoil. I'm presently working with/on a set of light blades with a descent airfoil, so I'm now in a position to contemplate the use of tip weights. I don't have a problem flying light blades and learning their personality before getting agressive. But, I'm kind of thinking about some tip weights to give a little float, instead of the drop you can get from the light blades.

So, back to the momentum and pitch athority "discussions". Thanks.

Phil

 

[C. Beaty]

Tip weighted blades fall through with a simple pop flare. They must be accelerated with a gradually increasing load. Landed out of a tight 180º turn where the G load has built RPM, they will hold off for a long time.

 

[Mike Schallmann]

F190--this is a General discussion thread --so the way I look at it I can generally discuss anything !!

 

[barnstorm2]

Tim, is there an echo in here?

Yes, I must have double clicked the edit button.

Yes, I must have double clicked the edit button.

.

 

[birdy]

vertical point
Dennis, a point is a point, it dont have angles, lines, horisons, sizes, dimentions or anythn else to follow, its a point.

nor is gravity a factor when figuring the CM, nor does gravity affect where the CM is, nor does the CM have to be exposed to gravity to be the CM.
Thats odd, i wunder wots pulln the machine down wen im don a hang test, or a double hang to determin where the COM is if it aint gravity????

 

[C. Beaty]

My discussions with Dennis may seem personal but they’re not. I take on snake oil and charlatanism wherever I find it when connected with rotorcraft.

In relation to moment of inertia, I’ve never said anything that differed from: I = mr²/3 for a uniform mass distribution or I = mr² for a point mass. The mistake I made was the assumption that Dennis could understand these simple algebraic expressions. I was wrong.

A statement such as; “tip weight is 3 times as effective at increasing moment of inertia as uniformly distributed weight” comes directly from the above expressions but leads Dennis to think he’s landed a “gotcha” simply because he doesn’t understand basic algebra.

A good many people see through Dennis’ snake oil and bluster but don’t take him on simply because they don’t want to subject themselves to his invective. Look at the venomous responses he’s directed against individuals who disagreed with him in a perfectly civil manner.

Dennis posts many “artists concept” illustrations and a photo or two of RC models gussied up with foam and putty to look like his artists concepts, implying he’s dealing with the DOD (Department of Defense) or some government agency or contractor for helicopter RPVs.

Having dealt with the DOD for many years, I can attest that they’re not all a pack of drooling idiots just waiting to pass our bags of money to con artists.

The US Army maintains rotorcraft research facilities and has a good many competent people, both military and civilian who know something of helicopters. Any company wishing to do business with the Army must pass their due diligence surveys which include résumés of engineering staff, financial status and no doubt, an internet search.

Any technical proposal submitted to the DOD, solicited or not, gets a great deal of scrutiny by people who know what they’re looking at, if there’s serious money involved.

I’ve seen some of Dennis’ résumés. In the first one, his alleged expertise came from having been a machinist. In a later one, he claimed to have learned the engineering trade from having served in the US Army Corp of Engineers; most likely moving dirt from one pile to another.

It’s entirely possible Dennis has done business with a major aerospace firm for machined parts or the like. But not for a serious helicopter.

Dennis does not have the ability to calculate the necessary strength for the rafters of a chicken house. If he was building one, he’d look at his neighbor’s chicken house and if it used 2 x 6s and hadn’t fallen in, that’s what he’d use. He’d be lost without a pattern.

Knowing all this, how could anyone trust Dennis’ “engineering” to hold his or her butt 1,000 in the air? Lots of gullible people did and are now 6 feet underground.

The late BJ Schramm’s statement: “look at the designer, not the design” is the ultimate truth when it comes to homebuilt rotorcraft.

 

[Rotor Rooter]

What to do on a Saterday nite.

What to do on a Saterday nite.

This discussion has got to see closure so that Dennis and Chuck can pick on Leishman. Therefore it will be brought to a close; by the process of deconstruction and then reconstruction.

Deconstruction:

Center of Gravity = Center of Mass

Center = Center
and
of = of
therefore
Gravity = Mass
However, we know that
Gravity works on Mass

In addition, we know that anybody who works on themselves is kinky.
We also know that science has a lot of twists and turns.
Therefore, science is kinky.

So much for the deconstruction.


Now for the reconstruction:

The center of Mass is important.
Therefore we will mark it's center with a 'X'
and call that point Xmass.

To oppose Xmas we need anti-matter.
We will assign it a point in space
and call it a Black Hole.

We all know the result when Matter meets Black Hole.

We must therefore thank Chuck and Dennis for taking Xmas down an apparently never-ending black hole.

:rip:
​

I've got to get a meaningful job.

 

[C. Beaty]

Now be nice, Dave, and I’ll use my influence with Dennis to get him to explain ‘U” joints to you. You’ll learn all about the Coriolis effect.

 

[M. Pearce]

C. Beaty,

Well I gotta say Chuck, do you feel like your wasting your time yet?

I took just enough engineering to know what's right when I see it.

And you go by the numbers that have been backed up by a whole lotta great minds.

Dennis will be here whatever his goal and you will be a lot better off not letting him fluff your feathers.

I left here a while back because I felt I wasn't learning anything new.

This forum is not what it used to be and that is definately a shame.



Mark.......

 

[birdy]

But Mark, ol CB's greatest downfall is that i assume he gives a sh1t.
Otherwise, i dout he would even be here.
If you give a sh1t, you tend to feel the need to correct missconceptions and falsehoods, specialy wen that false information could cost sumone their lives.

 

[Rotor Rooter]

Chuck,

You're supposed to be picking on Leishman, not me.

I've heard about Coriolis's effect. Apparently, she kept coming in and out of her ex-husband's life so much that he nicknamed her Cyclical Coriolis.

Dave

 

[Fl90]

Mike, you and I were typing at the same time....look at the times posted.

You do get offended easily. It's surprising, since you are often offensive. I'm guessing that from your career, you have had to purge empathy.


Chuck, thanks for the input on tip the weighted set needing a longer loading for effectiveness. How about the handling. I like light blades, as they don't feel as sluggish in response. Do light tip weighted blades share the sluggishness with a set of heavy unweighted blades, assuming all the blades are chordwise balanced?

Dennis, from your experience flying diferent types of blades, do you prefer light blades to have tip weights when used on a gyro?

Thanks all, Phil.