Velocity West comment on IVOProp

["Tim Crawford" <crawford@atdd.noaa.gov>]

The following was received form Mark Machado of Velocity West in reply to
my IVOProp post.  Mark, you should be an active contributor to the
reflector.  We need people like you to add realism, jack up post quality,
and help us fly safe!  

Thanks for the comment, I am putting the tapes back on.  I guess one
grounds the aircraft if they fail?

Further, it is great that IVO is trying to improve the hub design as it is
obviously the week part of a great idea and Prop.  I love the short
takeoff roll it allows.  Myself, I would like to see IVO introduce a 3/4"
x 7" 2024 Al hub with NINE 1/2" bolts.  The current 1/2" x 6" ??? Al
flanges are really NOT adequate!  Flexing of the 1/2" flange alone may be
causing tape & blade failure.  The additional bolts should be placed
between blade splits and on a bigger bolt circle.  Not only would the
Velocity spinner fit but IVO would increase the bite on their blades by
both more flang area and more clamp force.  Then, lets fix those toy
brushes!!  But I already did that.  I guess I need to machine a safe
flange system too?

Tim
+++++++++++++++++++++++++++++++++++++++++++++++++++++++

>Foil tapes -- The foil tapes suggested to see if the blades are moving are
>a nice thought but I believe a waist of time.  The glue is going to slip
>or the tape streach before there is a indication of a problem.  I now
>check the gap with a feeler gague.
>

Tim:

I only read the reflector about once a week due to time constraints, but
came across this first thing this morning.

Your comments about oil, interference, torque, etc. are very good. 
Totally
agree.

Your comments about the stainless steel tapes are, in my opinion, based on
my experiences with Lycomings, not safe.

I have about 80 hours on Lycomings (4 cyc) with IVO's.  I have broken at
least 12 tapes.  I have never been able to notice any gap change with a
feeler gage.

The tape breakage always occurs on a straight line directly between the
blade gaps.  From talking to now many people with Franklins, apparently
this rarely occurs, if ever.  With Lycomings, totally different story.
That's why IVO's with Lycomings are currently not advised.

The tape, quite obviously, is failing because of relative movement from
one
blade to the next.  The stainless steel tapes work hardens quickly due to
the movement and fails in what appears as a shear mode, directly in the
middle of the gap.

This relative movement will not necessarily show up as an increase in the
gap between the blades.  You can see evidence of such movement though the
deterioration of the gel coat covering the blade area at the crush area.  

Two areas can be examined.  Check for a gel coat "dust" on the back side
of
the blades, right adjacent the crush plates.  In addition, if you
dissemble
the blades, look for a "transfer" of the gel coat material from the blades
to the knurled crush plates.  Both are signs of gel coat deterioration and
relative movement of the prop blades.

My own experience has shown tapes breaking anywhere from 1 hour of service
to 10 hours of service with a strong 4 cylinder Lyc.  The best technique
we
have found to secure the tapes to the blades is a quick wipe of the gel
coat surface with a degreaser, then applying the tape with a round object
(like the shank of a screwdriver) to ensure good/strong contact with the
blade surface.

This has been my experience with 4 cylinder Lycomings.  From what I hear,
this tape breakage situation is not so common with Franklins.  I do know
that with limited experience on a 6 cylinder Lycoming and a 8 cyclinder
Chevy (driving a prop through a reducer), tapes aren't failing either. 
The
4 cylinder Lycoming is an entirely different story!

Just for let you know, Ivo is working on a hub that is molded with an
aluminim insert.  I should see a prototype set of blades in this office is
about a week.  No idea if it will work or not.  As Ivo puts it "could end
up in my "Museum of Bad Ideas".  Time will tell.  I'll be reporting on it
with the next edition of the Velocity Views.

Take Care
Mark Machado
Velocity West

P.S.  Your welcome to "reprint" any of this on the reflector.  Think my
reply will only go to you.



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      >-}     Tim        {-<
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 Long EZ N3R           Velocity N6Q