Size question

[AndyIoW]

Being new to the world of RC Helis, thought I might ask a series of questions.

Whilst reading various magazines and artcles on here, I noticed that there are sometimes references to various heli sizes such as 30, 60, 90. Now me being new got to thinking at how would anyone new to the sport understand these terms.

I believe that it might refer to the engine size on the fuel powered helis, so how do these then relate to the electric vesions.

Summing up the questions:

1, What are the references of 30, 60 and 90 mean.
2, How does that relate to electric helis
3, Is there a simple way of determining it, such as physical size.

Thanks in advance and sorry for putting what may seem a mundane question.

[Aztek1701]

Hi Andy,

Welcome to the forums.

To try to answer your questions...

1. You are right, the "30,60,90" refers to the engine size of the heli in cubic inches. So a 30 size heli has a 0.30 cu in engine. Its a good rule of thumb as to the overall size of the model. 30 = smaller 90 = bigger

2. It doesnt really relate to electric helis as they are generally smaller. EG. A T-Rex 450x is much smaller (about half the physical size) of a 30 size nitro heli. (There are of course exceptions to this rule)

3. There isnt really a simple way of telling how big a heli will be by its engine size, I know this because My sceadu 30 is roughly the same size as a Raptor 50, in fact the pyhsical size of them doesnt really change that much until you hit the 90 size then they are ususally quite a bit bigger.

Really the only way good way to tell how big a heli is independant of whether its electric or nitro is to look at the blade size, this tends to give a better idea eg..

T-Rex 450x running 325 mm blades = a heli about 750-800mm long (2x 325 + a bit for the tail)
Sceadu 30 running 600mm blades = a heli about 1.5m long

Joker 2 Electric (or 90size nitro) running 770mm blades = a heli about 1.8m long

Hope this sorts out the technobabble lol

Take care.. Azzy

[raven_darkcloud]

OK, electrics tend to have classes. Mid, mini, micro, and sub-micro aside. They have a 30 class elec thats about the same as a nitro. After that you have (not including all the fixed pitchers) a 600 class (~600mm blades), An unclassed area of 380mm to 450mm blade size, a 400 class (this has to do with motor size not rotor) this is your T-rex, shogun/zoom, x400 and such. Then you have the 370 class as in blade cp, hunnybee, hornet,humming bird, and so on. And you have a big mess in betwien. THe best way to do this is by rotor dia. thats basicly rotor dia + 10% (give or take) for nose to tail, or (r-dia - 10%)/2 to get an aprox blade size. That 10% is about the size of the rotor head. r-dia + head width is normaly close to overall leanth.
Now that your head is spinning I'll let that sink in and it might help. Just remember that math just puts you in the ball park not dead on.