Dave and everyone interested,

First I have to say that I have no experience what so ever with the IVO,
(but other props.)

I got this info from a builder in US on the IVO

3 blade, 66" dia prop, electric adjustable pitch from 45" to 105"
Max blade width: 5.25"
At 25" radius: 0.7" thickness, 4.75" width.

Analyze:

The blade thickness of almost 15% at the 0,75 radius is maybe one reason for
the reported result of the IVO to be less then others tested.

"Normal" or often used on wood props is 13% thickness; normal range is from
11% to 14% for wood props.

Metal props from 8,5% to 10%

Max blade width of 16% of the radius (33") is normal (15%-16.7%)

The blade width of 14,4% at the 0,75% radii is a bit wider then normal
(12-13%)

The adjustable pitch range from 45" to 105" (16deg to 34deg at 0,75% radii)
is good.

But it is only the outer parts of the blade that is changed in pitch not the
inner. What the pitch is here I don't know.

What effect does this have?

If we think of an adjustable prop (70" dia) that have CONSTANT PITCH along
the blade when the .75% radii is sat to 15deg. = 44" pitch

At the .45% radii the angle is 24deg.

(At the tip it is 11.3deg)

IF we now increase the angle of the whole blade 15deg to 30deg at the .75%
radii we get 95" pitch.

At the .45% radii =39deg = 80" pitch

(At the tip 26,3deg = 108,7")

This means that the inner parts of the propeller blade will not increase as
much as the outer parts in pitch, but this is not all bad, by a number of
reasons.

But if as in the case of IVO the inner part is not changed in pitch, it will
be far from optimum in some stage of the speed range. Especially if the
speed range is large as in high performance aircraft.

If the inner part is coarse pitch and fixed it will stall during take off
and climb.

If the inner part is fine pitched and fixed it will make negative thrust at
high speed.

So, The thicker and wider outer 25% of the blade aren't very effective, the
inner fixed pitch isn't good at all speeds!

A propeller that have blades that is thicker and wider then normal needs to
compensate this by reducing something else, like diameter and or blade area
to handle the same power, the pitch should be sat so the blade work at its
best L/D for efficiency, so if we reduce the pitch (angle of attack) to
compensate for an propeller that have to much drag it is not so good, it is
better to reduce the diameter in that case.

A thinner propeller is better (obvious) that will give us a larger diameter
that moves more air, or if the diameter is limited by tip-speed or
structural reasons, more blade area (more blades)



For now,

Jan Carlsson

www.jcpropellerdesign.com




"Dave S" skrev i meddelandet
hlink.net...
Ok.. question for those out there with some hands on experience with the
IVO Magnum series electric inflight-adjustable props.

What has been your experience with this product.. Any pro's or cons
based on your experience...

Has the product met your expectations...

Where I am coming from: working with a builder making a Mazda powered
Velocity. We have kicked around the idea of a controllable
pitch/quasi-constant speed propeller.

I have corresponded with Tracy Crook (www.rotaryaviation.com) who has a
flying RV-4 with a Mazda rotary. His experience was that he had a loss
of top end speed with the IVO product compared to a fixed pitch prop...
It was enough of a difference that he has chosen not to research using
the product any further in his later applications. I am not sure if this
is because the blades are unable to "twist" enough or what.

This is somewhat disheartening, because the IVO seemed like a cost
effective possibility. The electric MT is out of my price range, and I
cant seem to find any other electric actuated in-flight adjustable props
that can handle 200-250 hp.

I am curious if others have experienced similar outcomes using this
propeller in applications running in the 170-200 kt/200-250 hp range

Dave