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<DIV>Thanks. Very interesting. </DIV>
<DIV> </DIV>
<DIV>David</DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=DaveL322@comcast.net href="mailto:DaveL322@comcast.net">David
Lockhart</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 8:18 PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Webra 1.45 Prop</DIV>
<DIV><BR></DIV>
<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>
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<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>
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<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></BLOCKQUOTE></FONT></BODY></HTML>