Scott Speirer wrote:

I've got two different propellers I'm looking at and I'm trying to

figure out which

one to buy.  I'm soliciting your educated opinions as to which would be

better ..

which would provide more thrust in the airspeed range 30 mph to 90 mph.

1.) 68" Warp Drive 5 or 6-blade ground adjustable propeller.

Approximately 2" chord

for each blade.  (Originally designed for the ultralight/microlight

market.)  About

$800.

2.) 68" Sensenich 2-blade composite ground adjustable propeller.

Approximately 8"

chord for each blade. (Designed for the airboat market.)    Manufacturer

reports it

is most efficient between 2500 rpm and 3000 rpm.  About $1500.

Remember my aircraft is different than most of yours ... it's a two-seat

tandem

gyroplane, not an airplane.  Think "slow flight".  This thing is only

going to fly

between 30 mph and 90 mph.  I have a '91 Mazda 13B turbo, and a 2.85:1

gear reduction

drive.  Gyroplanes need more thrust to fly than do airplanes of

comparable weight.  I

need at least 600 lbs of static thrust.  800 lbs would be better.  I

cannot go bigger

than a 68" diameter, otherwise I would be sawing into my vertical fins

on either side

of the prop.

Snip

   Scott,

      I know the Ivo "Magnum" is controversial in the group and I don't want to
start a war but Dave McBride used a 3 blade ground adjust version with reported
success on his purpose-built 13B powered Gyro/trainer in the early 90s in the
Phoenix,AZ area. Dave was using the Ross 2.85 redrive. There was an extensive
article in one of the early "Contact" magazines on this machine detailing what
it took to make this early 13B powered a/c sucessful in the Az heat low and slow
slow at 7000+ rpm. If memory serves me Dave started flying with a "Warp Drive"
but had better performance with the "Ivo" and put hundreds of hours on it and
the 13B training Gyro pilots.

     Kelly Troyer

I think there is a consensus on the low and slow applications of either of these props.
There is nothing really wrong with the IVO for these applications as long as it
is not used on a big four cylinder aircraft engine. They work but they may not
be the best. If you don't already own one however I would take a look at the
Powerfin blade as most agree it is a better design than either of these two.
A drawback to the IVO in these applications is it is not really adjustable
pitch. It is adjustable twist and that is not what you want in this application
or any other for that matter.

Paul Lamar
 
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