Lomcevak

CriticalMach

CriticalMach

New member
Hi -

Still new to this forum (post count testifies), but curious if any of you had good luck in performing more "wrung out" aerobatics? I'm practicing for a routine with the Sbach 342 (35%) and find that unlike actual aircraft, RF's planes do not have the rudder authority and/or too much yaw stability around their C.G. to permit high alpha sideslips.
While trying to perform a Lomcevak, I can get the plane to rotate once head over heels but the control surfaces just seem to loose some authority. Any recommendations on editing the config or tweaking?

Thanks!

- Colin
 
flyingcolin said:
Hi -

I'm practicing for a routine with the Sbach 342 (35%) and find that unlike actual aircraft, RF's planes do not have the rudder authority and/or too much yaw stability around their C.G. to permit high alpha sideslips.

While trying to perform a Lomcevak, I can get the plane to rotate once head over heels but the control surfaces just seem to loose some authority. Any recommendations on editing the config or tweaking?

- Colin
Click to expand...

Yup there's a LOT you can do in the editor to adjust a plane to your liking.

Remember that what you may find as "not enough authority" is probably what the designer had dialed into their own planes.... and in this case the Sbach model is based upon the full size plane owned by Knifeedge's president. BTW: His has the ORIGINAL Red/Black/White Thunderbolt scheme EVERYONE has on their RC Sbachs.

You can increase the wing lift for the rudder which gives it more authority (aka "lift" ) or tweak it's weighted factors, increase it's size, increase the throws, etc. etc. etc.

You can also decrease the fuselage "lift", change the airfoil ( sides ), weighted factors, center of pressure, etc. to give you what you want.

Your best bet is to play with each parameter one at a time on a copy of the plane's physics until you understand what each parameter does.

Then try modifying only one parameter to give you what you are trying to achieve.
 
Ask yourself, what you would do if your "real" airplane acted in the same manner. Shift weight around, add weight, remove weight. Change throws... I think that will be the best guide. If it were me, I would assume the physics choices were correct by the designers, so changing lift values etc would be lower on my spectrum of changes. You may have a different aeronautic background and knowledge. It would be easy to change the size of the rudder to give it more authority...

A basic question... you are flying with high rates? Channel 5 with switch away from your body is high rates (standard setting unless you have changed it). There is also a nice flight lesson by Frank Knoll demonstrating the Lamcevak built into the simulator.
 
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flyingcolin said:
Thanks all for your input. I will watch the video and play with a copied config for the Sbach, as well as some other aircraft.

If any of you can take the default aerobatic planes and do this with them, I'll be impressed: http://www.youtube.com/watch?v=skfprThzUq4

Thanks again, I'll report if I make any progress!

- Colin
Click to expand...

BTW: a large scale CAP 232 ( which you do see in the videos too ) is better suited to this manouver.

Part of the move is also dependant upon enough inertia too, while still having control surface authority ( thanks to prop wash over the surfaces ) at high alpha.

So wing "post stall" values, plane weight, and control surface authority all come into play.
 
Well I could not do it stock... but two mods and I got it. There may be some disagreement over what is really the Lomcevak maneuver.. Is flipping end over end the maneuver? Some would disagree.
 
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All I did was increase the elevator throw and move the CG forward... I think the Sbach does a nice Lomcevak... but the flipping end over end requires more throw and moving the CG... maybe someone else would do it another way. The guys at the field are flying a 30cc Sbach and having pitch control problems. They managed to surgically remove the gear a second time yesterday.. I love the way the plane flies in the sim.. don't know if the plane is really meant to tumble quite this way... I would experiment with moving the cg around as this makes those types of unstable maneuvers possible.
 
Thanks all, I'm tweaking the elevator throws and moving the C.G. in hopes that may do the trick. It looks like the Zlin has no problem doing Lomcevak's almost as well as the CAP.

Yes...a Lomcevak is essentially "head over heels", so when you see a plan roll (flip) around it's lateral axis, that's a Lomcevak.


Thanks!

- Colin
 
No that is not a Lomcevak... just pitching head over heels... read the wikipedia definition and see the flight video presented in the training section of real flight. It gets cloudy sometimes, but I think the wikipedia is pretty close.

flyingcolin said:
Thanks all, I'm tweaking the elevator throws and moving the C.G. in hopes that may do the trick. It looks like the Zlin has no problem doing Lomcevak's almost as well as the CAP.

Yes...a Lomcevak is essentially "head over heels", so when you see a plan roll (flip) around it's lateral axis, that's a Lomcevak.


Thanks!

- Colin
Click to expand...
 
I know what a Lomcevak is, I'm not asking you what it is. I've done them many, many times with R/C aircraft. What concerns me (and why I posted here) is how to edit and properly configure the RF aircraft since regardless of how hard I try, I cannot get any of the stock, default RF to properly tumble.
 
You most likely won't get the stock aircraft to fly hard 3d-type stuff, because they are build for what a real model would call a "standard" build; to get more 3d maneuvers you need to edit the planes as if you'd have built them for the "extreme" builds, as called for in many 3d-capable planes. This involves, like posters above have said, increasing the throws (in this case mainly rudder authority) and changing the CG; in my opinion I would move the CG actually BACK in this case as I find that leads to much easier sideslip-type maneuvers and more instability in general.

Doing these changes isn't unrealistic at all because these things are what you'd have to do in real life; don't feel like you're "cheating" by increasing throws, etc.
 
thpppttt said:
don't feel like you're "cheating" by increasing throws, etc.
Click to expand...

Most of us here consider moving the CG as a 'cheat' unless you do it by reassigning weights, adding weights, etc. Simply sliding the CG is a cheat, according to most of us. (Not that it never needs to be done. Sometimes it's the only option.)
 
How is adding a lump of lead somewhere cheating? It is nice that RF allows you to just move the CG point, rather artificial I agree, but how much work is it to really move the weight... not that much more. Generally moving CG (weight) aft makes for a more unstable airplane... that is why they frown on stuffing small planes full of baggage. I tried moving it forward and it seemed to work, so I did not experiment moving it back. A nose heavy plane will fly, not well, but a tail heavy plane will not fly.
 
Here's the bone-stock PAU Edge 540 doing some stuff. There are lots of side-slip-type maneuvers in this but there is a lomcevak similar to the vid you linked immediately following the 8-point loop. If this is what you were talking about, here's a bone stock RF plane pulling it off! :D

(no throw edits, no weight changes, etc., seriously as stock as it gets)
 

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