Rotors

[illusionist]

I believe my rotors are flat. And i am actually over weight slightly, so there is no room to add anything. I may just scrap this model and restart. But to avoid the same problem on my next model, i have a few general questions. Should i keep the rotors at opposite ends or move them both to the top, and how long should my motor stick be aprox. ? How much weight do you allow for the average motor stick? How do you go about making sure the pitch of each blade is exactly the same as the others? Would it be adviseable to "V" the blades up slightly? I appreciate the help.

I can answer a few of your questions. For the motor stick I would allow anywhere from 1.5 - 2 grams. Average length would be about 11 inches (if it's too short, the motor will bunch up). Wether you keep both rotors at the top or at opposite ends will require testing. I'm building a model with both close to the top (all my others were at opposite ends) to test both ways, so no answer for sure.
To ensure that you have the same pitch, I have gone about it using a small protractor. Align the bottom edge with your spar(that connects both blades) and measure the angle of the blades. Another method would be to build something like this: http://www.faimodelsupply.com/fai-science.html Check out the pitch gage at the very bottom.

[illusionist]

Okay, not sure if this is the right thread so post it anywhere if needed.
This is rotor hanger that I made with music wire, it has a pigtail-like end. I'm pretty sure there is a link to this on the soinc.org website, but I've posted a picture in the helicopter Image Gallery. Should be titled Helicopter Rotor Hangar.

[blue cobra]

Did you just use regular needle-nose/round-nose pliers to make that? The curves are marvelous.

3252|68/IMG_2666.jpg

[illusionist]

Yes, just one normal plier, and one standard flat plier. The circle is formed by wrapping the wire around the prop shaft wire (or something with the same thickness of the prop shaft), and the pig tail is also formed by loosely wrapping the wire around the prop shaft wire.

[lllazar]

What exactly is the purpose of the rotor hanger - is it just the piece of wire that is attached to the rubber motor and free rotor? If not, what is it, and what purpose does it serve?

[illusionist]

Instead of using something like a Harlan Penny Plane hangar, or an Ikara prop hanger, this is just another method of attaching the free rotor to the motorstick.

[lllazar]

O i see, so the prop shaft wire would fit through the pig tail loop and the circular loop up top. The prop shaft wire would join the propeller at the top circle, and at the pig tail it would curve to hook onto the rubber? Very nice, is it lighter than commercial prop hangers? If not, for what reasons would it be preferable to make our own?

[illusionist]

That's exactly what it is. To be honest, I don't know what the benefits are... It definitely weighs under 0.1 gram(my scale is 500 x 0.1 capacity), compared to another cheap commercial hangar I have that weighs 0.6 grams. I made it just to see if I could and how it would work out. Plus, it's a lot cheaper than the commercial hangars. A couple feet of music wire only costs about $0.98.

[lllazar]

So i've become quite proficient at stripping balsa wood and grouping the sticks according to siffness/density and i was wondering, for the rotors, should i just use as light balsa as i can sort? Of course it wouldn't be so light that it crumbles in my hand, but you get my meaning. Also, i strip the sticks from sheets, i initially considered 1/16 squared but i made a rotor yesterday with 3/64 x 1/16, i was wondering what everyone else has been using?

I ask this because i want to be as close to the 4g total as possible without going over, and i don't want the rotors to total more than a gram, thanks!

[lonestar]

Stripping from a 1/16" sheet, I've managed separate blades below .5g each with 1/16×1/16 sticks. Speaking of balsa sizes, I'm also trying to see how 1/16×1/4 holds up for a motor stick.