How do you get realistic rotor droop ?

I do not have much expecience building helicopters but my technique would be warming the rotor blade (warm water or a hair dryer) then bending it in the desired curve.

The technique I've seen is to assemble the rotors on the hub, don't attach the mast if you can, then put them upside down on a plate and place weights in the middle.  That then pushes the middle downward and when left for long enough the rotor blades bend to look like the sag you're after.

And example can be seen in Helo 53's HH-3E build on page 2 post #28, here - s362974870.onlinehome.us/.../index.php

Just an afterthought, I'm guessing that if you've assembled the main rotor including rotor mast, but haven't attached it to the main body (or it simply lifts out anyway) you could do the reverse of what Helo 53 did -

Put the rotor the right way up but on top of an open jar or cup or mug or something to accommodate the rotor mast and place a plate on top.

Although the blades might snap doing it that way due to the sudden increase in weight, I'd do it very very carefully, but it might work.

Find a large-size cooking spoon with a curve that matches your desired blade droop. Spoons are ideal for this, since one part of the "bowl" is usually a sharper curve, that tapers off to a more gentle or almost straight contour toward the handle--you can easily choose where your droop goes. A few good sturdy rubber bands, and you're ready to go.

From my recent 1/144 Sea King:

Bring a pot of water to a boil and take it off the heat, dip the spoon with rotors in for a slow 30-count (approx. 30 sec.), then run the spoon under cold water for about half that time, and they're done. It gives you a uniform curve on all the blades, and it's fast.

The way I do it is to CAREFULLY  mold the droop into the blades by forming them between my fingers. I basically put a slight bending moment on the blades abd then pull them out of my fingers to form the curv. Thus does take some time as I only do a little bit at a time not to over stress the plastic.

I also mace a template to make sure they all have the same droop to them.

Remember that blades usually droop or bend more in the first 1/3 and tend to become a little straigther or droop less towards the tip as the weight of the blades become less.

I attatch a pic ov my 1/72 MiL 35's blades to see how straight molded blades can be bent with fingers.

Thanks Guys- some good tips there !

I gently pull the blades over the edge of a table.

I'm currently working on the Revell 1/48 Apache.  I recently had a thought on this topic and was wondering if this would work.  Since it is now summer I thought maybe use the inside of a car as sort of an oven.  I could stick the rotors inside the hot car (out of direct sunlight of course) with the blades weighted to the desired droop, then essentially 'bake' them for a certain time period.  It seems to me it could work.  The only question would be is how long to let them sit inside the hot car.

Great tips, gonna try one of these techniques when I get on to my Hobby Boss Helix..Thanks!!