aerobatics design theory

Current

Adrian wrote: Canilisers! thats what those things that are a bit reminiscent of F1 from a few years back are called!

thanks Jon, that's exactly what I was after

so....

in terms of profile,

if we take a line from the motor shaft down through the wing centre line then tail should be in line too. keep as much area as possible in front of the CG.

Pretty much, yes

does the position vertically of the area affect roll coupling? eg if more than 50% of the area was above the motor/wing/tail line would it give roll coupling?
what about fin/rudder area should that be kept as close to centre line as possible too?

Truth is everything has an effect in some way, because of the lower tail the fin area above will always be greater than below the tail. The good news is that roll couple can easily be removed with a mixer

plan form:

Straight leading edge should give least yaw to roll coupling?

No straight or swept leading edge has little affect on roll couple, height of wing above or below centre line and dihedral angle are the main issues

looking at those pictures F3A really hasnt changed that much other than gaining some side area.

all have straight trailing edges, lowish wings, motors appear to be on the tail line.

I like that they arent scale.

don't get me wrong, scale has its place in the sport but for aerobatic models they have a job to fill and by making them scaleish that compromises the design and handling of the model.

scale should be scale and making the model fly nicely with the compromised handling that a scale plan form brings is part of the skill.

it bugs me that a lot of the 3d stuff is based upon their full size counterparts.

anyway, i digress...

what about beyond the stall? harriers and the like, my mx2 has a pretty knarly flick when doing rolling harriers that makes it hard to keep the roll rate nice and constant. Is that purely wing section related?

Adrian wrote: looking at those pictures F3A really hasnt changed that much other than gaining some side area.

all have straight trailing edges, lowish wings, motors appear to be on the tail line.

I like that they arent scale.

don't get me wrong, scale has its place in the sport but for aerobatic models they have a job to fill and by making them scaleish that compromises the design and handling of the model.

scale should be scale and making the model fly nicely with the compromised handling that a scale plan form brings is part of the skill.

it bugs me that a lot of the 3d stuff is based upon their full size counterparts.

anyway, i digress...

what about beyond the stall? harriers and the like, my mx2 has a pretty knarly flick when doing rolling harriers that makes it hard to keep the roll rate nice and constant. Is that purely wing section related?

Interesting point about scale 3d, there was a period around early 2000 when there were a few 'freestyle 3d' models developed from f3a like the Majestic, but they seemed to disappear? Maybe scale based stuff sells better?

Harriers is one area where a straight leading edge does help, this is why the Edge 540 designs do well at 3d, it seems to delay the tip stall. Your foamy MX2 is more likely a bit flicky as it is relatively small so the wing loading will be higher, the bigger models are definately more forgiving.