Author: "geomagruder" <marsavn@...> Time: Thu May 19, 2005 6:32 pm PDT Link
I fly an RV-4 in the hot desert west of Las Vegas (8 yrs). Found cracks
in Sterba prop last two annuals in a row. Cracks are along grain in aft
laminate from bushing hole to edge of prop about 1 and a half inches
long. Ed fixes them and says it's common in the dry heat, but this last
prop was only a year old. Am conscientious about torquing, but wonder
about any secret techniques for original mounting and also opinions on
dynamic balancing.
Thanks in advance. Rich Reitan, retired Taco
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Author: "Rob Ray" <smokyray@...> Time: Fri May 20, 2005 1:19 pm PDT Link
Hi Rich,
As a veteran of 4 wood or wood/composite props I think I can add
something useful to your plight. I ran a Sterba prop for 4 years with
great service and sold it to Chuck out in CA who still flies it. I
removed it in lieu of a Catto composite which is much better built for
the long haul and stronger than the exposed wood especially when you
fly in the humidity of the southeast and out west every summer. My
Sterba required tightening every 25 hours and refinishing with spar
varnish every year, something I accepted as standard. I switched to the
Catto prop as it incorporates an aluminum back plate which helps the
bolts stay tight longer and it is a much more durable prop. The
cracking you speak of happened to a friend of mine with a Sterba prop
airborne in his RV4 over Las Cruces and he lost 40% of one blade. He
got the 4 on deck safely after alot of "bad vibrations" so severe he
feared the engine would break loose at any time. He bought a Sensy
metal after that and quoted to me that "trees don't spin" I like heavy
metal".
Ed does make a great prop for the price however comma, composite props
hold up better in all climates. The Catto Prop as well as several
others (Gary Hertzler, Prince P-tip, MT, Hoffman)incorporate composites
over wood, the best of both worlds, strength, load dampening and very
smooth. Craig Catto's website is www.cattoprops.com and Gary Hertzler
is in Mesa, AZ in the book. Hope this helps...
My 2 cents...good luck!
Smokey
--- In RV-4@yahoogroups.com, "geomagruder" <marsavn@t...> wrote:
> I fly an RV-4 in the hot desert west of Las Vegas (8 yrs). Found
cracks
> in Sterba prop last two annuals in a row. Cracks are along grain in
aft
> laminate from bushing hole to edge of prop about 1 and a half inches
> long. Ed fixes them and says it's common in the dry heat, but this
last
> prop was only a year old. Am conscientious about torquing, but wonder
> about any secret techniques for original mounting and also opinions
on
> dynamic balancing.
> Thanks in advance. Rich Reitan, retired Taco
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Author: "John Walsh" <john_rv4@...> Time: Sat May 21, 2005 2:04 pm PDT Link
I'll offer another angle on this. My 4 has been hangared it's whole
life (and still is). It has spent most of it's life living in the
Northeast. It currently has a Sensy wood that has ~500 hrs on it.
It is like new. It has never been refinished. Unfortunately, it
wasn't pitched correctly and I can overspeed the engine at any
altitude.
With that in mind, I just ordered a new prop from Ed Sterba. There
are so many prop choices it's maddening. But given the good service
from the Sensy and Ed's 1985 prices :-), it was hard to ignore him.
The downside of the Northeast is wild wx swings. I have seen
humidity at 100% for days on end, followed by several days at 50%.
I've seen as low as 35%. When I re-torque, I always check the torque
first by setting the wrench to about 80% value(16ft-lbs or so). I
then walk around the nuts expecting: click,click,click. After the
check, I then loosen everything and torque normally. Last time I
torqued my prop, two of the nuts moved slightly before the
wrench "clicked". I will be checking more frequently........
John
P.S. I really want a $2500 Hartzell that weighs 28lbs.:-)
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