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<DIV>Re-post from myself, some time ago.</DIV>
<DIV> </DIV>
<DIV>Regards,</DIV>
<DIV><BR>Dave</DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV>--------<BR><BR>I've been repitching APCs for years - and in general not
had a problem with<BR>springback/memory - but I have found that the technique is
critical. Using<BR>the Prather pitch gauge, I feel comfortable saying I
can repeatedly measure<BR>prop pitches within 1/8" pitch - which I feel is
pretty much the pushing the<BR>precision of the gauge. I would say that
10-20% of the blades I twist do<BR>have some amount of springback (1/8 to 1/2")
in the first 24 hrs - but I've<BR>not seen them springback anymore after that,
and it is rare that I have one<BR>springback as much as 1/2".<BR><BR>I mark
every prop front/back of the blade where I am going to heat with the<BR>heatgun
and where I am going to apply the twist. I use a good heat gun, a<BR>thick
cotton towel or sock, and a large set of channel lock pliers.<BR>Basically, I
slowly heat the prop blade near the hub with the heat gun<BR>(alternating
front/back, concentrating on the thicker areas of the blade),<BR>and when the
blade is hot enough, it will twist without too much pressure.<BR>For the APC
15.75-13 3 blade, I heat at Station 5 (of the Pitch gauge, which<BR>is 2.5" from
prop center) and then wrap the sock around the blade and hold<BR>the prop at
station 7 (3.5" from prop center) to apply the twist - I put the<BR>other 2
blades on my leg and do the twisting bit in my lap. (For 2 bladers,<BR>I
use 2 pair of pliers). The sock is too keep the teeth of the pliers
from<BR>scarring the prop. When the desired pitch is achieved, you can
either cool<BR>the prop in cold running water (and move onto the next blade) or
let it cool<BR>overnight (don't mess with the prop while it is
cooling).<BR><BR>The basics are pretty simple - but it does take some practice
to get good at<BR>using the Pitch Gauge and being able to get consistent
readings from the<BR>Pitch Gauge. Heating the prop slowly (I spend 4-5
minutes before twisting<BR>on the 15.75-11) is better than heating it fast -
think slow cooked prime<BR>rib, not "black and blue". You want the prop
warm on the surface and at the<BR>core - then it will twist easier and have less
memory. If the prop is not<BR>evenly heated, the pitch will tend to wander
as it cools - not good. It<BR>usually takes me 1 heating cycle, about 1
major twist, and a couple minor<BR>"tweaks" during the first couple minutes of
cooling to get the pitch change<BR>I want. On occasion, I do need to
reheat a blade and tweak the pitch a bit.<BR>Some of the props I twist get a
little bit of whitish discoloration when<BR>heated, some develop the whitish
coloration after I twist them, and some<BR>don't show any change at all.
Near as I can tell, the prop is at about 200<BR>degrees when I twist (using an
InfraRed temperature gun).<BR><BR>I used to quench the prop in cold running
water (very important to cool both<BR>sides equally) and repitch each blade
consecutively in one session. At this<BR>time, I'm having better luck
letting the prop air cool - the pitch seems to<BR>wander less. I then let
the prop sit overnight and check again the next day<BR>and make minor pitch
adjustments if needed. I've got a couple 13.5-11.5N<BR>prototypes I made
back in 1992 that were the result of twisting/reshaping<BR>and they are still at
11.5" pitch, after 12 years, and hundreds of flights.<BR>And I've got some
prototype 17-13Ns that are 5 years old with hundred of<BR>flights and still
ok.<BR><BR>Regards,<BR><BR>Dave Lockhart<BR><A
href="mailto:DaveL322@comcast.net">DaveL322@comcast.net</A></DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=dflynt@verizon.net href="mailto:dflynt@verizon.net">David Flynt</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=discussion@nsrca.org
href="mailto:discussion@nsrca.org">discussion@nsrca.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Sunday, July 10, 2005 3:06 PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Webra 1.45 Prop</DIV>
<DIV><BR></DIV>
<DIV>Curious -- how does one repitch a prop? Is it machined?</DIV>
<DIV> </DIV>
<DIV>Thanks,</DIV>
<DIV> </DIV>
<DIV>David</DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=RUDDERCABL@aol.com
href="mailto:RUDDERCABL@aol.com">RUDDERCABL@aol.com</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=discussion@nsrca.org
href="mailto:discussion@nsrca.org">discussion@nsrca.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Sunday, July 10, 2005 12:03
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Webra 1.45 Prop</DIV>
<DIV><BR></DIV><FONT id=role_document face=Arial color=#000000 size=2>
<DIV>
<DIV>In a message dated 7/10/2005 2:22:10 PM Eastern Standard Time, <A
href="mailto:rcaerobob@cox.net">rcaerobob@cox.net</A> writes:</DIV>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px solid"><FONT
style="BACKGROUND-COLOR: transparent" face=Arial color=#000000 size=2>The
choices are pretty subtle, and not real obvious unless you're willing to
try "weird stuff"....like the Master Airscrew 16 x 10. Proving to be
a great choice. So is the "GRS" (looks like a Mejzlik) 16 x 11, and
the Mejlik itself. Then, of course, the APC's, but Fred refuses to
retool and reduce the 13 pitch three blade (Completely understable
considering the "fickleness" of US). Lockharts' repitching works
VERY well, and I've had the 10, 11, and 12 pitch. All work very well
on the OS 1.60 piped.</FONT></BLOCKQUOTE></DIV>
<DIV></DIV>
<DIV>Bob</DIV>
<DIV> </DIV>
<DIV>Perhaps the APC 15x13w would work . It worked well on my 1.40RX. I also
have one that Dave Lockhart repitched to 10 that I will be trying soon on an
1.40L.</DIV>
<DIV> </DIV>
<DIV>Robert Gainey</DIV></BLOCKQUOTE></BLOCKQUOTE></FONT></BODY></HTML>