Thinking about making the switch to FAR.

[capi3101]

Quick question - is there any case in which I'd want to set the control surfaces to higher than 0.5 strength?

Last night I had a flight which prompted this question - I had a new tail-less delta/no canard plane design that I went ahead and ski-jumped off the Runway, and when I went to begin climbing my elevators would explode every time. Q was around 24 kPa at that point. Ultimately I got the plane to fly by throttling back to 2/3 before attempting to pitch up, then throttling back up after I pitched up. I think the design would benefit greatly from canards; wound up lighting the rockets at 19,500 because it was getting close to not being able to climb any further and I was getting temperature warnings in the yellow - made orbit with fuel to spare as it turned out, though. I worry about what will happen when it comes time to bring that plane back down, though...might be nose heavy (i.e. a lawn dart) with the way I set things up.

[Wanderfound]

I normally set my control surface mass tweakables to be the same as the wing they're mounted on.

[capi3101]

I generally do the same; I've been setting the main wing/elevators/flaps/spoilers/ailerons to 0.5, canards to 0.4 (when I use them) and the fin/rudder to 0.3. Are those good values for general purposes? Under what circumstances would they need to be stronger or weaker?

[capi3101]

Alright - so I downloaded Froude this morning and will get it installed when I get an opportunity. Meantime, can someone give me a lowdown of what's changed with it? For example, I saw on the main FAR thread someone with the wave drag up and there was a blue curvy line - what exactly is that used for? Is that even in the Froude build?

Haven't had much to ask you guys about lately - which may or may not be a good thing...

[SAI Peregrinus]

From the FAR changelog (it's in the OP...):

0.15.3V "Froude"------------------------------------

Update to MM 2.6.5 for greater nyan nyan

Allow display of pressure coefficient (under assumption of axisymmetric flow) over the vehicle

Tweak subsonic drag to be lower for slender shapes

Fixed voxelization breaking due to combined memory leak + hard memory limit for voxelization after many editor -> flight cycles

Fixed some race conditions in voxelization that could break aero properties

Fixed deadlock in threadpool if many voxelization events triggered simultaneously

Fixed possibility of deadlock if voxelization settings were updated

Fixed voxelization errors for some cargo bays and other parts

Fixed voxelization errors for pWings; includes support for any parts making use of mirrorAxis

Fixed some longstanding wing interaction issues, including permanent stalled wings

Fixed a newer issue with wing shielding on symmetry counterparts

Some main axis determination improvements

Fixed an where certain user atmospheric settings would not take

The blue wave drag line is the pressure coefficient line.

[capi3101]

The blue wave drag line is the pressure coefficient line.

Okay, and what's the significance of that line? What do I want that line to look like when it comes to my designs?

[SAI Peregrinus]

Basically it gives you (some of) the information you'd get out of putting the craft in a wind tunnel and analyzing flow. You can use it to determine info about lift, drag, etc.

[capi3101]

Alright. thanks.

So basically the blue curve is just showing me how the pressure differential is distributed over the length of my craft, i.e. which part of my horizontal surfaces are going to generate the most lift. Is it meant to replace the CoL indicator (or perhaps explain why it shows up where it does)?

Edited June 19, 2015 by capi3101

[SAI Peregrinus]

Not exactly replace. It lets you visualize what the pressure field around the craft will be, which determines not just the center of lift but also the center of drag (and some other things). The center of lift is where the lift would be if you had a point mass with the same parameters (just like the center of mass is for inertia). So it's more informative than the CoL marker, but also more advanced, and thus if you could build planes that worked before it's probably easiest to just test a few and see how performance varies with different coefficient of pressure curves to get an intuitive understanding. A bit like the "Make the yellow line as straight/smooth as you can" rule of thumb works.