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        Discussion What's the Difference between an Aerobatic Version and 3D version of a kit?

#1 fooyukvoon May 14, 2010 09:20 PM

What's the Difference between an Aerobatic Version and 3D version of a kit?
 
Hello everyone,

I've got the HK Edge 540G2 36" Kit, and I am suspecting it may be designed for aerobatics and not really suited for 3D. How can we tell if a plane is suited for 3D or not?

Are there certain things to look for when buying a 3D capable plane besides what the seller claims it can do?

Or is there settings that will convert a normal Aerobatic plane into a 3D capable plane.

I hover/prop hang mostly (with my other foamie/EPP planes) and this being my 1st balsa/ply 3D plane, I find it to be very unstable getting it into the upright/vertical position.

Any suggestions will be greatly appreciated.

Thanks

Nd4spd

#2 kc-foamie May 14, 2010 10:46 PM

Quote:

Originally Posted by fooyukvoon (Post 15090397)
Hello everyone,

Are there certain things to look for when buying a 3D capable plane besides what the seller claims it can do?

I hover/prop hang mostly (with my other foamie/EPP planes) and this being my 1st balsa/ply 3D plane, I find it to be very unstable getting it into the upright/vertical position.

I think two requirements to make a "3D" plane is the ability to climb vertically (greater than 1:1 thrust ratio) and the ability to get the CG far enough back to allow reliable hovering. I'm sure exceptionally skilled pilots could hover a lot of planes, but it's far easier when the CG is back a bit from the most stable configuration.

The combination of those two things (power and weight distribution) could mean the difference between "aerobatic" and "3d".

#3 theKM May 14, 2010 11:35 PM

err, close. 3d aerobatics are aerobatics and maneuvering post-stall. Because there's no lift (the plane is stalled), you typically need a boat load of power to compensate. The post above is right in that regard. Not unusual to have 2:1 thrust to weight, won't have much fun unless you get at least 1.5:1 or more.

The other key aspect of crontrolling beyond the stall is very large control surfaces and control throws... the air isn't moving much, so you need more control. extra throws and surfaces also means you can push the plane into 3d maneuvers which requires pushing through stalls, etc.


"getting the cofg far enough back to hover" isn't really correct... hovering is a skill that takes practice, and if you know the input you can hover a nose heavy plane if it's designed well. If you set up the plane to be tail too heavy you simply create a mess of a plane to fly in other maneuvers and you're simply making life hard for yourself. "neutral" is about as far back as you ever want the CofG (neutral is rolling inverted and needing no down elevator to maintain height).

#4 fooyukvoon May 15, 2010 12:22 AM

In the manual, the CoG was recommended at 7cm from LE, at that setting, the plane appeared tail heavy when the throttle is below 60% and drops/sink rate is quite fast but flat. It does not glide very well off throttle.

Does this indicate a CoG that is too far aft?

Have tried moving the CoG as far as 1.5cm forward. At this setting, the plane glides and it appears to fly just like a normal plane should. Would this be a good setting for 3D? Being a balsa/ply plane, I am being very careful as it is not as crash resistant as an EPP plane :D

Thanks.

Nd4spd

#5 theKM May 15, 2010 10:55 AM

Quote:

Originally Posted by fooyukvoon (Post 15091319)
In the manual, the CoG was recommended at 7cm from LE, at that setting, the plane appeared tail heavy when the throttle is below 60% and drops/sink rate is quite fast but flat. It does not glide very well off throttle.

Does this indicate a CoG that is too far aft?

Have tried moving the CoG as far as 1.5cm forward. At this setting, the plane glides and it appears to fly just like a normal plane should. Would this be a good setting for 3D? Being a balsa/ply plane, I am being very careful as it is not as crash resistant as an EPP plane :D

Thanks.

Nd4spd

some planes do this with a neutral cofg, and some 3d planes aren't easy to land for this reason. will have to do the roll inverted test to find out... trim for level flight at half throttle, and then roll inverted and see what happens.

#6 Dennis C May 15, 2010 12:45 PM

Assumint that the airfoil is symetrical then you need to trim the airplane to fly straight and leval with nearly full throttle, roll inverted and you should need nearlyno down stick to fly leval.

UP/down thrust can effect climb and glide power on and power off.

trimed for leval flight at full power (CG located where you want it) cut the power, the plane should start a very gentle dive, power back up and it shoul leval back out.

If the model dives too much then you need to add down thrust. If it baloons then you need add up thrust.

another key to goood 3D performance is a light wing loading. Many good sport aerobatic models are too heavy for good 3D performance.

Dennis

#7 fooyukvoon May 15, 2010 06:45 PM

1 Attachment(s)
This is the model I am talking about. It's by Top Model (China) Everyone at my field commented that it was quite heavy. :(


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