Best way to get the droop in the rotor blades?

Hi loach Driver . As it turns out , I have done something similar to what you have said . I glued my rotors to the hub of my kitbashed HH-3F Pelican , I then borrowed a dinner plate out of the kitchen cupboard , placed the rotors upside down , put a metal bolt in the middle of the hub and clamped the rotor tips to the outer edges of the plate . However I put my rotors outside in the sun everyday for about 4 days , [Its summer here in Sydney , so it's nice warm weather]. It worked out okay .  Kind regards John

I'm currently working on a 1/72 Alouette III. To put some droop into the rotor system, I did the following;

 1. Researched the real helicopter thoroughly. The Alouette III has some droop but not a huge amount as the blades are relatively short. As someone said earlier, there is nothing worse than a good model with too much blade-droop. Each helicopter is different in this respect so check out photos of it first.

 2. I glued the blades to the rotor head and put them aside for a few days.

 3. I inverted the blades and placed them on a saucer. The blade tips rested on the rim of the saucer while the rotor head was able to flex down below the level of the blade tips. I supported the rotor head from underneath to prevent too much droop. I then placed a small weight on the centre of the top of the rotor head to hold it down onto the support underneath.

 4. I then heated my oven to a relatively low temperature (not sure what it was but I'd say it wasn't anymore that 50' C). The saucer and blades were placed in the oven for about 15 to 20 minutes before being removed and placed in the fridge to cool!

 5. The blades came out with a nice even droop all-round. I had to repeat this sequence to get the droop exactly as I wanted it.

The beauty of this method is that the blades are heated to exactly the same temerature and I'd say the blades could even be straightened out and worked on again if clamped to a straight surface and heated, if things don't work out the first time. This is the first time I have used this method and it has worked well for me. The only problem I can see with this method is that the heat might cause the droop to start at the arms of the rotor head on some types of helicopter and not on the blades themselves.

I tried to straighten the blades on the Italeri OH-13 Sioux with boiling water before but I only ended up with two unuseable, shrivelled-up blades so I think the low-temperature oven is the way to go. Hope this is of use to some.

OK, How in the world do I post a pic on this forum????

Bryan

Denver

Best way to get the droop in the rotor blades?

Show 'em a picture of Hillary Clinton. 

I'll dig them up and post them, probably this weekend.

 Bryan

        That is the best way( by hand ) David. You are also correct on different drup for different helis.The tie down effect is another great piece of advice. I have noticed Russian blades seem to drup more then all others.  I also like the heavy load look as in slow take off.

                                                       Great read ,the best  Davey 5

    ps  like the build the way you like attitude!!!!!!!!!!!!!!!

fraighttrain30 wrote:

"...The Apache blades are incredibly strong.  I have a shot of one that was blown over during a sand storm in Kuwait.  It's sitting on it's left gear, the tail wheel, and two of the blades..." Bryan Denver

I would LOVE to see that pic if it's not too much trouble Bryan ? :-)

regards,

Tread.

You have to be careful "drooping" blades.  Some hardly droop at all.  One interesting note is the blades on the 53 hub actually "lag" at rest.  

The Apache blades are incredibly strong.  I have a shot of one that was blown over during a sand storm in Kuwait.  It's sitting on it's left gear, the tail wheel, and two of the blades.  They look like they didn't flexed at all.

Bryan

Denver

Once you start, you just can't stop!

 Anigrand Craftwork has some really unusual and fun test machines. If you like resin and unusual subjects they have a lot of stuff.

David

a former neighbor/'53 CC used to build..at least 6  1/48 revell 53's a year and would build the rotor head first, take a clean metal trash can lid and invert it, invert the rotor head and place into center of lid, add a weight to bottom of rotor hub/swashplate assy then let the heat inside his garage plus the time to finish the build to do it's thing to the blades, always came out with realistic looking droop after a week or so.

if your building your models in a garage in NJ. this time of year a neaby space heater might help- my neighbor(Dan Hammer) had Tustin,ca. heat helping him.

brian  

Howdy wing_nut,

 Good member Patlabor made a very good point about researching the actual particulars of the ship your building, the number of blades, what they are made of, etc, etc.

 As to 'drooping' methods.  I have used a couple of methods with alternating success.  The best method I have found believe it or not is; assemble the rotor hub assembly with blades attached, set on top of a small block of wood with a small divit in the center of the block, set the rotor hub/blade assembly so that it balances on the block, set the whole thing to spinning and slowly and gently apply a flow of hot air from a heat gun {available at Home Depot for $20.00} and slowly apply this heat while actually watching your blades begin to sag...one of the advantages of this method is; not only can you evenly apply the heat {and therefore the resultant blade 'sag'}, but the flow of air coming from the heat gun keeps the blades turning so that you do not have to physically touch them to keep them moving.

The only warning, or caveat with this method is; be careful not to over apply the heat.  And, if you feel like an actual heat gun would be 'too much', you can accomplish the same thing with a standard hair dryer.....just takes a bit longer ;-)

 hth pard'

regards,

Tread.

Wingnut

 first, study your subject in side view photos carefully.  I have seen SO SO many over-drooped blades that look like a banana split on a hot day, due to way overbending.  Modern composite blades bend differently than all metal blades of years past, and differently than wood blades.

Determine from your side view photos (assuming the blades aren't tied down) where to begin bending and then work your way down the blade bending slowly and carefully with your fingers. some thick blades, or older plastic, may need some gentle heat to help.

A two bladed machine with the aft blade tied down will have a totally different droop in the aft blade than the front.  Same for a three bladed machine that has the forward two blades tied to the skids, or the aft two to the skids. I tend to tie my blades , it REALLY cuts down on people trying to "spin" my rotors at shows

HTH

David

Thanks Smokin' Great idea.  

Hope see to more of you back here. 

Marc Make a jig out of a peace of wood and some dowel bend the rotor to the sag you want mark the wood and drillholes for the dowels  to get the amount of sag you want thrn boil some water and submerg the rotor fo a 5 seconds and place in jug until cool . if they have tomuch sag sit them out in the sun for 8 hours as they would siton the chopper