Consistant trailing edges on rotor blades

[3D-Don]

I saw something on TV a few nights ago on Discovery Wings, on the show
"A Chopper Is Born". For those not familiar with the show, a guy from
England is building an Exec helo and the build process is filmed and
played back in half hour segments. Any who...

This particular episode focused on the installation of the aluminum
rotor blades. Before the actual installation, the guy went through a
process that I have never seen or heard of before. Using a custom
carriage looking device with a dial indicator mounted in it, he
proceeded to measure the entire length of the trailing edge between
the rivets, every 4-5 inches or so. He took all of those readings,
averaged them out and used that number as a target. He then went back
down the trailing edge and hand bent it up or down until the dial
indicator read the target average.

The reason for all of this hand labor was to eliminate/reduce the
possibility of vibration. How come I've never seen anyone do this
sort of thing on a gyro? With the installation and removal of the
rotor blades after the trailer ride, I would imagine the gyro rotor
blades would have all kinds of dings, dents, and bends in the trailing
edge.

Comments.....

Don

[Ken Sandyeggo]

(3D-Don) wrote in message >...
> I saw something on TV a few nights ago on Discovery Wings, on the show
> "A Chopper Is Born". For those not familiar with the show, a guy from
> England is building an Exec helo and the build process is filmed and
> played back in half hour segments. Any who...
>
> This particular episode focused on the installation of the aluminum
> rotor blades. Before the actual installation, the guy went through a
> process that I have never seen or heard of before. Using a custom
> carriage looking device with a dial indicator mounted in it, he
> proceeded to measure the entire length of the trailing edge between
> the rivets, every 4-5 inches or so. He took all of those readings,
> averaged them out and used that number as a target. He then went back
> down the trailing edge and hand bent it up or down until the dial
> indicator read the target average.
>
> The reason for all of this hand labor was to eliminate/reduce the
> possibility of vibration. How come I've never seen anyone do this
> sort of thing on a gyro? With the installation and removal of the
> rotor blades after the trailer ride, I would imagine the gyro rotor
> blades would have all kinds of dings, dents, and bends in the trailing
> edge.
>
> Comments.....
>
> Don


Don, I don't ever trailer my gyro, but the guys that do, I know they
take extreme care in removing and replacing them and usually carry
them in the original shipping crate with plenty of bubble-wrap or
foam. I've never heard of any gyro-head banging up his (or her)
blades in transport, although I'm sure some have done it. Doesn't
seem to be a general concern.

Not quite sure on bending the trailing edge, but some are made of
glass. I now have aluminum Sportcopter blades on mine, and they fly
extremely smooth right out of the box. I don't recall any postings on
the Rotorcraft Forum (about 99% gyros) over the years regarding
bending the trailing edge of blades for any reason. Out of balance
(lateral or vertical vibes) gyro blades are usually adjusted for
smoothness by mainly adjusting the hub-bar between the towers,
adjusting the blade pitch and adding or removing weights from the
tips. Sometimes transverse weight bars are used, but from personal
experience, once you take this step, your blades are hopeless as far
as ever getting a smooth ride. You usually have a set of poorly
designed and made blades. Don't have to do any of that stuff on
Sportcopter blades. My glass RAF blades were hopeless.

Ken J. - Sandy A. Geaux