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<DIV><FONT size=4>Keith</FONT></DIV>
<DIV><FONT size=4></FONT> </DIV>
<DIV><FONT size=4>The biggest problem is with the rudder where you'll likely be
using a pull-pull setup. I resorted to the big Sullivan horns on my Smaragd to
get the pivot point right on the hingeline. If you don't with a pull-pull
setup, you'll have differential throw from one side to the other which will show
up as one cable getting tighter (on the pulling side) while the other cable goes
slack. One way around that is to offset the attachment on the servo horn exactly
the same distance that the pivot point is offset from the hingeline. For
example, if the pivot point on your rudder horns is 3/32 rearward of the
hingline, you would offset the attachment points on the servo horn, rearward, by
3/32. This really does work, but requires a round servo horn since you won't
have any material left going 3/32 rearward on the arm-type servo horns.
Even with the round type, the constant radius of the round horn means
that your new attachment points are going to be closer to the middle of the
wheel than at their normal point meaning less throw. I've done this with
Futaba's and was able to get enough throw using their extra-large wheel that
comes with the servo. JR's largest wheel is a bit smaller and I couldn't get
enough throw out of it with the offset.</FONT></DIV>
<DIV><FONT size=4></FONT> </DIV>
<DIV><FONT size=4>The other solution is to double bevel the hingeline at the
rudder post. You bevel the rudder LE as always but only half as much which
effectively gets your rudder horn closer to the hingeline. You also bevel the
tailpost on your fin the same amount. You'll end up with all the throw you'd
want and then some while moving the hingeline rearward to help accommodate the
"not long enough" horns. This is what I'm going to do on my next Smaragd so I
can use those pretty anodized horns I got from Lamar! Having said all this, I
wish we had hardware available that eliminated the need for all this. I don't
worry about this on the ailerons and elevator since offsetting the servo horn is
a simple matter of rotating the horn until the geometry creates equal throw. I
let my radio take care of any tweaking once I get the geometry within a half
degree or so. I usually end up changing it in the trimming process anyway. Hope
this helps.</FONT></DIV>
<DIV><FONT size=4></FONT> </DIV>
<DIV><FONT size=4>Verne</FONT></DIV>
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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=tkeithb@comcast.net href="mailto:tkeithb@comcast.net">Keith Black</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> Tuesday, September 02, 2003 9:57
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Control horns, is it just me
or... ?</DIV>
<DIV><BR></DIV>
<DIV><FONT face=Arial size=2>When it comes to control horns for pattern planes
it seems to me that some of the most commonly used choices have a major
flaw.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>On my last plane I used the MK Aluminum
Horns on all surfaces except for the rudder where I used the IM pull-pull
horns. Both of these are nice horns except they have a major flaw when using a
pull-pull setup. The flaw is that the little black plastic arm that screws
onto the horn and connects to the clevis is so short that it doesn't extend
out over the hinge line. I know that with pull-pull systems it isn't
*absolutely* necessary for the connection to be exactly above the hinge, but
the further back it is the more slack there will be in the cable that is not
pulling. In my opinion with these horns the connection point is too far
away from the hinge unless the horn is virtually mounted on the control
surface bevel (especially when it comes to rudder). This can easily be seen in
these "instructions" for installing the MK horns <A
href="http://www.centralhobbies.com/buildingtips/mkhorns/mkhornsinst.html">http://www.centralhobbies.com/buildingtips/mkhorns/mkhornsinst.html</A>.
Notice that in this picture there surface isn't beveled yet and the horn is
almost on the edge.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>On my new plane I wanted to avoid this problem so
I did some searching to find a better solution. To begin with I looked for a
longer arm to connect to the MK horn, one that would extend out to the hinge
line. I found two options from Sullivan but both require too big of a horn
thread (6-32 and 8-32). My search then led me to two other choices that seem
to be good alternatives. The first is the ZNLine aluminum control horns, but
these are apparently only distributed by ZNLine (<A
href="http://www.znline.com/produits.php?langue=english&cle_menus=1025879382&cle_data=1025901639">http://www.znline.com/produits.php?langue=english&cle_menus=1025879382&cle_data=1025901639</A>)
which means an international order. The other solution I've found is by
</FONT><FONT face=Arial size=2><FONT face="Times New Roman" size=3><FONT
face=Arial size=2>RC Model Enterprises</FONT> <FONT face=Arial
size=2>(</FONT></FONT><A
href="http://home.att.net/~rc-enterprises/rcme_014.htm">http://home.att.net/~rc-enterprises/rcme_014.htm</A>)
but these control horns seem very pricey!</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>If anyone could point me to a longer 3mm
connecting arm that will fit on the MK and IM horns I'd be happy (BTW, I've
used the MK BB connectors on the MK horn and they still aren't really long
enough).</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Is it just me, or have others experienced this
dilemma as well?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Thanks,</FONT></DIV>
<DIV><FONT face=Arial size=2>Keith Black</FONT></DIV>
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