My question on KE

[NX-687]

I have a foamy that wont even look at KE , no way
What sort of steps do I take to rectify this ,
Change the rudder shape? , have tried this , but as yet unflown
If that does not work add or subtract fuse area fore and aft ?
If that does not work just buy a kit that flies KE ???
Its a very tricky one , getting it to hover was easy compared to this KE trimming I suspect :confused:

[Ollie]

What do mean "KE"? I never heard of KE. Please spell it out.

[NX-687]

It was Knife Edge flight,

[Ollie]

You need a profile fuselage side area (1) and vertical tail (fin and rudder) area (2) which gives lift. Use height of fuselage and vertical tail height. Keep the area (1 plus 2) larger. Keep the plane light weight. Keep the the airspeed larger with more power.

Flying KE you keep the angle of attack larger (nose up and tail down).

[ghoti]

like Ollie sez, and KE, to me, means kinetic energy. Assume nothing!

[BMatthews]

Perhaps you can post up a pic of your model?

Basically you need to have a fuselage with lots of side area. Profile is nice but it can also be a full fuselage. About 25 % of the side area (fuselage and fin/rudder included) has to be ahead of the balance point and the rest behind. If you've got enough rudder throw to hover with good quick authourity then you'll have enough to knife edge easily.

[NX-687]

Only 25% of the fuse area in front of the CG . oh, thats why it was hopeless when I put on a big fat nose , I will cut down nose area and increase aft area , thats easy on a profile foamy just cut and glue here and there


Will,report progress , backwards,,, eerrrr , forwards :confused:

I can fly KE , its just that my model cant

Also the fuse shape symmetrically relative to the wing CL must have some bearing too
Also batt position under or over the wing plays a part , depending on batt weight reletive to model weight

[BMatthews]

Definetly. For it to fly nice in knife edge you want to have somewhat equal area below and above the CG location and to some extent semi equal rudder area beloa and above. It's not hyper critical but it shouldn't be highly biased one way or the other.

If you had a huge deep nose on it I'm guessing that it wanted to overly nose up and try to reverse direction? Or if it wasn't centered it may have tried to roll too much?

My own first try at a profile foamie does quite nice KE loops with just a hair of aileron and elevator. Problem is I'm still working on finding out how thick the hair needs to be.... :D

[RCAV8R13]

Build my Mini Vertigo Pro. KE is perfect. KE loops are effortless. 2,447 downs can't be all wrong. Many have said it is the best KEing plane ever.
http://www.rcgroups.com/forums/showpost.php?p=1935112&postcount=20
RCA

[Bill Mixon]

One of the easiest solutions is to add side force generators if you really want to fly knife edge.
Wings fly great, long skiny fuselages don't even though it may have a lot of area. And that's what you're doing in knife edge flight is flying on the fuselage.

If you know just a little about aircraft design you can see that a fuselage alone is a very poor lifting surface. Lots of surface area behind the CG, very low aspect ratio, high loading, asymmetric, etc. You don't see any asymmetric wings with a 6" span and 36" chord for good reason.
When you look at your fuselage as a flying surface you can see why it flys so poorly.

The solution is to make the fuselage really tall, to add area. Depending on the model this may not be practical or may not look desirable. It also adds stability on the roll axis so your roll rate will be reduced by some amount.

Side force generators "SFG's" are one solution, as they are VERY effective wings to fly on when in knife edge.

One of my indoor aerobatic biplanes had near 50% of it's total upper/lower wing area in SFG's (struts) plus the fuselage for lift.
This results in very strong knife edge flight capabilities. Take a look at some of the models in the F3P indoor forum and notice the designs they are flying. Most of them are using some sort of vertical addition (SFG) and/or tall fuselages with a low flying weight.

Keep in mind that as you modify a plane for extreme KE performance you will sacrifice lateral stability, and increase sensitivity.

[NX-687]

Thats just great info , can run with that