Hello All,

I realize I am jumping in late to this thread.  I apologize if I reiterate any concepts already thoroughly discussed.


IMO and supported by the attached video and bsg:


There are three aspects of the in game props discussed here.  The visual 3D model or picture of the props, the way the props act regarding the aerodynamic aspects of a prop and the way they act regarding the angle of attack of the prop.  A fourth issue that I will discuss last is an anomaly of self powering props.


First the way they look to the eye.  They are either right handed or left handed (clockwise or counterclockwise) props.  The pictures previously shown in the above posts make this clear.  There is some confusion and discussion, it appears clear to me which way the current in game prop should act if it is turning one direction vs another direction.  The tip of the blade is indeed flat but the root of the blade is not, just like real propellers (although real ones don't get so flat at the tip).  I don't really know why we are discussing this aspect so much, it's very clear from RL experience how it should work.  

A prop gets most of it's forward force from the overall angle of attack of the blade in it's design.  The root has quite a bit of angle but does not have much airspeed and the tip has very little angle but a lot more airspeed.  There is a bit of force from the cross section of the blade at each point along it's length but it does not apply to our discussion, the prop either provides force one way or the other in relation to the direction of rotation and the way it pushes is related to it's design the the design is obvious to the naked eye.

In Besiege the force generated by regular rotation (without increased or decreased angle of attack through feathering) is opposite the picture or model of the prop. 

However the force generated by changes in the angle of attack (feathering) is also backwards.  Even if the image of the prop were correct for the forces generated by rotation it would still be reacting incorrectly for changes in overall angle of attack.  No matter which kind of prop you have, right or left, clockwise or counterclockwise, the angle of attack works the same as it does for a flat surface, like the in game rudders or wings.  The angle of attack works correctly in game for rudders and wings but it is backwards for props, without regard to the picture of the prop.  Angle of attack is not dependent on the angle of the root of the prop but is dependent on the tips.

In Besiege the force generated by angle of attack on propellers is backwards but is correct for other airfoils. 

Sorry this is dragging out, I hate it when posts get all confused with replies because of misunderstandings between poster and reader.

Here is my last point.  When you have a rotating prop in Besiege and you change the angle of attack slightly the prop becomes self powering (as long as there was already sufficient rotation speed to prime the process).  I have called this the Butterfly effect for lack of seeing any other terms addressing the issue.  It is an extremely powerful effect because it feeds itself, it is the opposite of how things work in real life.  If you have a rotating prop and give it just a bit of angle of attack (it will look like the wrong angle because of the above mentioned problems in the game) it will power its own rotation with great force.  If you look at my builds in the War Machines section you will see this used often.  

Here is a video and a bsg demonstrating all the above points.  You can see when the Butterfly effect takes over when the flat base propeller which is used to give the powering wheel something neutral to push against suddenly begins to rotate in the direction of the powering wheel.  It's because the prop itself is generating so much rotational power it is transmitting back through the wheel to the flat base prop.

SO, to the devs, thanks for a fantastic game.  The prop picture or model should represent how the prop acts in the game.  It's backwards right now.  The angle of attack for props is backwards without regard to the prop visual model or physics model.  I suspect that fixing that angle of attack issue might kill the Butterfly effect but I cannot put my reasoning into words and I don't know how the actual math works below the surface in the coding.  Again I suspect there is an issue where some code is signed incorrectly, a plus should be a minus or vice versa.  This is just gut instinct from my own coding errors and what I see happening in the in game results.

Let the flames begin.  Watch the below video, try to see the lift reactions vs the input to the props.  Towards the middle/end keep your eye on the lower dampening props rotation, it's the Butterfly indicator as well as the sudden tremendous increase in lift even the power has been removed.

The propellers react correctly when pitched. You can't really say they are acting in the wrong way when not feathered because as I showed before, they shouldn't produce any thrust at all on any direction. There's no forwards or backwards on those props, no matter which way you spin them, the force should cancel itself out with the flatness of both the root and the tip, which produce more drag than airflow redirection.

About the other stuff you mention, you are correct, but they are not (I believe) the topic of this thread.

I'll make a video showing my concerns later.

I look forward to your video

Here is a video you posted earlier:


a.pomf.se/dikmpb.webm

Replace the flat wing panels with props.  Change the pitch in the same direction.  Opposite results than with the the wing panels.

A very detailed analysis of whats going on, I like it beege It does explain quite well as to what the issue is, although what might be handy is just a couple sentences to summarise what you've written, for those with less time (a TL:DR in some respects)

The bold statements in my above post explain the problems and the weird auto powering aspect is best seen by downloading the bsg and showing yourself that you can fly without any motor or power.

New props are symmetrical both in appearance and performance, they mount at an automatic slight angle of attack.  If you rotate it 180 degrees it acts the same.

The performance is quite different, not good or bad, just different.  It might just be that some of the quirks have been straightened out.

The self powering aspect is still there, if you decrease the built in mounted angle of attack slightly the blade will power itself, perhaps at a different rate than the prior prop, I cannot tell since the prior props are gone.

Initially it seems the symmetry and reverse performance has been addressed.