[NSRCA-discussion] Surface alignment?

Wed Jan 10 10:01:20 AKST 2007

Surface alignment checks:

I remember pictures of Hanno Prettner's Super Sicroly II  which had
alignment indicators on every surface (music wire)... Of course that was
back in the less precise days of control system design etc.  I assume he
checked these on pre-flight/post-flight to reveal any changes between
flights.  Assuming one could keep the indicators from being damaged the
technique might reveal some interesting trim anomalies.  I don't know if
Hanno kept this up on subsequent airplanes, but haven't seen anybody do
that since....  I'd be interested if only for the sake of history to
know more of the story of that practice if someone wanted to elaborate.

Chris

________________________________

From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Jay
Marshall
Sent: Wednesday, January 10, 2007 11:49 AM
To: 'NSRCA Mailing List'
Subject: Re: [NSRCA-discussion] Pull-Pull

Keith, have you tested nylon coated SS cable? Do cables continue to
stretch or just initially?

-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Keith
Black
Sent: Wednesday, January 10, 2007 12:11 PM
To: NSRCA Mailing List
Subject: Re: [NSRCA-discussion] Pull-Pull

Good summary Wayne. 

This topic is like religion or politics. I know several top level FAI
pilots that swear the DEPS (or similar) system is the most accurate for
exact elevator matching and they'd not use anything else. I also know
some FAI pilots that have made the finals of NATS (even won) with dual
elevator servos (of course, these guys could probably kick butt with
only one elevator half).

I don't recall many, if any, top guys in the NATS FAI finals flying with
pull-pull recently.

My observation is that my rudder pull-pull tension varies over time and
I think the same would occur with the elevator. If it did then it seems
like an opportunity for the two halves to get out of unison. 

There's also the constant debate about what the best cable is based on
weight and how much each stretches. Some will tell you that fishing
leader doesn't stretch, others say Kevlar doesn't stretch, and on and
on.

Well I've tested multiple types and sizes of cables, fishing leader and
Kevlar, under controlled tests with weight hanging on them for a day or
so and they all stretch. Maybe the stress we put on them isn't enough to
cause stretch, but I think it is. 

I personally prefer either dual elevator servos or DEPS, that's my
religion ;-).

Keith

	----- Original Message ----- 

	From: wgalligan <mailto:wgalligan at goodsonacura.com>  

	To: NSRCA Mailing List <mailto:nsrca-discussion at lists.nsrca.org>

	Sent: Wednesday, January 10, 2007 10:17 AM

	Subject: Re: [NSRCA-discussion] Pull-Pull

	I have tried all these methods of elevator setup.   Pushrod with
Y at the end, pushrod to MK bellcrank, dual servo's,  pull/pull steel
line and Kevlar, and DEPS(dual pushrods.

	FWIW...    All these setups work good and are personal
preference based on your building abilities and the type of airframe
your using.  One thing I have found is its paramount to have a fuse that
does not flex or twist under load.  If it does have any movement I would
think the dual servo's or DEPS may have an advantage over the pull/pull.
But I have been wrong before.

	1. Pushrod with Y...   worked good only if it had a bearing at
the front and tail to support pushrod.

	2. Pushrod to MK bellcrank... was very solid with nary any blow
back.  But a little heavier then some setups. Pushrod needs support in
middle of rod with foam to prevent oscillation of the rod.  Has to many
points of possible failure and requires more hardware, although I put
over 800 flights on one setup.

	3. Dual servo's...  Very redundant and with the right
transmitter can be setup precisely.  Slightly heavier then pushrod setup
with servo's and wire leads.

	4.Pull/pull...  Very light and most adjustable of the setups,
Requires more time to set up properly and is a little less ahhh...
aesthetic with all the lines protruding from fuse.  Wire lines require
good crimps and straight exit holes in line with servo and control
surface.  Kevlar(my choice) requires Teflon or nylon exits to prevent
chafing of the line but does not have to be a perfect line to the
control surface when using this type of exit.   I went gun shy on
pull/pull my setup(wire) broke on the down elevator on the 10th flight
causing a mishap.   One other plane with Kevlar had hundreds of flights
before a radio failure retired it and it was still in good condition on
inspection after the crash.  BTW  I have found a spool of Kevlar control
line works good and will last for many setups and cost about 8 bucks.

	5. DEPs ... dual elevator rods (.07 c.fiber with Teflon sleeves)
has been in the last two planes I have built.   Requires a little time
setting up in a straight line through exit to assure smooth operation.
Very light and positive control to elevator halves.  When exited below
stab looks cleaner.

	Wayne Galligan

		----- Original Message ----- 

		From: Bob Richards <mailto:bob at toprudder.com>  

		To: NSRCA Mailing List
<mailto:nsrca-discussion at lists.nsrca.org>  

		Sent: Wednesday, January 10, 2007 7:38 AM

		Subject: Re: [NSRCA-discussion] Pull-Pull

		Not all planes have push-pull elevators. I've had planes
with all pull-pull tail surfaces.

		But, there are a few reasons why elevators would be
setup with push-pull. Seperate servos (much smaller ones) can easily be
mounted in the tail. Having seperate servos allows easy travel
adjustment (travel matching) through the radio programming, and also
allows redundancy on this critical control.

		The rudder requires more torque -- heavier servo -- and
it might be a design consideration (balance) to keep the weight of the
heavier servo closer to the CG.

		Personally, I like pull-pull and would prefer it in my
models.

		JMHO.

		Bob R.

		Jay Marshall <lightfoot at sc.rr.com> wrote:

			Why are rudder controls pull-pull and elevator
controls push-pull?

			Jay Marshall

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