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Re: REFLECTOR: elevator cuffs





Jack,

I know this can be very confusing.  So, I will tell you what I have learned.
Per Duane/Scott, Danny originally put the cuffs on to calm the pitch-buck so new
velocity pilots would not get into a big pitch-buck during landing flare-out.
What the cuffs do is provide a pitch-buck that will cause the nose of the plane
to rise and fall in a total distance top to bottom of 1-1.5 feet with very
smooth motion.  They also cause the stall speed to increase as less air
separates around and thru the elevator surfaces and this speed is proportionally
increased with an increase in canard load factor (front seat passengers).  On my
airplane a std fg, I initially had a pilot stall speed of 70 knots. And with the
canard loaded with two max weight front seat occupants the plane never would
pitch-buck but rather just float in a very mild descent.   After discussions
with Duane and Scott, I removed 6" of the inboard part of the cuff and saw 62
knots.  With the target at 58 knots, I removed 6" more and got it to 60.  I then
removed 6" more and saw very little decrease.  I ended up removing all the cuff
and now see 59 knots and a top to bottom swing of 1.5-3 feet.

The stall speed is directly proportional to the liftoff speed and distance and
when loading up the canard with additional front seat passengers I found the
liftoff speed to exceed 85 knots prior to the cuff removal.  This limited the
length of runway I could use to something greater than 3500'.  After the cuff
removal the liftoff speed is down below 70 knots at max front seat weights.  And
the end result is that the elevator is much more effective at these slow speeds
allowing more maneuverability while landing.  Prior to cuff removal, if the
plane got too slow (even below picth-buck speed with nose down attitude) you
would have no elevator to correct for wind especially vertical control and the
plane could drop down hard on the runway with the pilot having no way to correct
it.

In summary, the cuff while it prevents violent pitch-bucks in my opinion is not
worth the tradeoff of higher speed takeoffs and landings as well as less
effective elevator control during landing.  And depending on which Velocity you
are building, the cuffs are not even put on on some models now.

Any comments/corrections/suggestions?

Greg Otto
N150GH
Base Airort: McKinney, TX (TKI)





"Reeder Graphics, Inc." <design@reedergraphics.com> on 08/02/99 09:30:12 AM

Please respond to reflector@awpi.com; Please respond to "Reeder Graphics, Inc."
      <design@reedergraphics.com>

To:   reflector@awpi.com, Christopher Martin <christophercmartin@earthlink.net>
cc:    (bcc: Greg Otto/CONTRACTOR/DALLAS/CYRIX)
Subject:  Re: REFLECTOR: elevator cuffs




O.K.
I just recently notified the Velocity factory that the cuffs were
missing from my kit--and from the fast build from Alan Shaw.

Now it seems many of you prefer no cuffs.

Could more of you elaborate for and against the canard cuffs?
Actual vs. expected performance?

Thanks,
Jack Reeder
Std RG Elite
N220VE


Christopher Martin wrote:
>
> I had the same experience. After installing the cuffs and priming the canard,
> Mark stopped by my hanger and on inspection told me, "Why did you install the
> cuffs?". I then spent the next week grinding off all of the cuffs and
> repainting.
>
> Chris Martin
>
> Schweitzer, Bill wrote:
>
> > I had a chance to talk with Duane and Mark Machado at Oshkosh.  They told me
> > they are flying with shorter length elevator cuffs (or none).  The cuffs
> > smooth out the canard stall and reduce the tendency for pitch-buck at stall
> > speed.  However, they also make it difficult to get any elevator effect at
> > landing speed.
> >
> > Mark suggested making the cuff 18" shorter, removing the outboard end of it.
> > Since I had just spent a couple days installing them I was pleased as punch
> > :-) to get to take my grinder to them.  Anyone else thought about this?
> >
> > ---
> > Another note: awhile back the factory sent me a refill order for fine bid.
> > The material they got from their supplier was a heavier weight, "satin"
> > weave that was very difficult to wet-out.  After using it for awhile I asked
> > them about it.  They sent me a replacement of the original material.  If you
> > got this stuff from them you may consider requesting the original.
> >
> > Bill Schweitzer
> > std RGE
> > San Jose, Ca

--


Reeder Graphics, Inc.
http://www.reedergraphics.com