Stability is a function of the tail volume (area of the tail X the moment
arm), so you can increase this by strecheing the fuselage or by
increasing the area of the horizontal tail.
JIm
On Tue, 19 Apr 2005 13:17:17 -0400 "Golden, Kevin"
<kevin.gol...@churchdwight.com> writes:
> So........If I were to build a KR1, the airfoil would be easy enough
> to do,
> but what about the horizontal stab? Should the KR1 also have a
> wider
> horizontal surface and larger vertical surface? I personally like
> the
> fuselage to remain stock length, though I realize lengthening would
> help
> too.
>
> Kevin.
>
>
>
>
> -----Original Message-----
> From: Mark Langford [mailto:n5...@hiwaay.net]
> Sent: Tuesday, April 19, 2005 10:58 AM
> To: KRnet
> Subject: Re: KR> Stability
>
> Ray Fuenzalida wrote:
>
> >I need a clarification on the new airfoil. Are stability issues
> limited to
>
> >the KR and not the slightly larger KR2S? If I have the Diehl wing
> skins
> >and use those, what should I expect in the future? Slight
> instability?
> >Major instability? Please throw out some guidance.
>
> I think a large part of the stability improvement that both Bill
> Clapp and
> Mark Jones are experiencing is due to the fact that they are flying
> the KR2S
>
> with longer fuselage and larger horizontal (and vertical)
> stabilizer (per
> plans). I forget how long Mark's h/s is, but Bill Clapp's is a
> little
> longer than even the stock plans call for, maybe 3" per side. If
> Marks's is
>
> 6" longer per side like mine, that would definitely make a
> difference. And
> the fact that the horizontal stabilizer is a "real" airfoil has to
> make it
> more effective than the thing shown in the plans, somewhat
> equivalent to
> making it larger. That horizontal stab airfoil is one that I'll
> take credit
>
> for, since I sized it to fit my airplane, and created the drawings
> that are
> now on the net for it. The vertical stab is definitely my creation,
> as it's
>
> a one-of-kind 5.5% airfoil based on a known airfoil formula,
> designed to fit
>
> the "stock" vertical stab spars.
>
> Another part of the stability improvement may be attributed to the
> improvement in decalage, lining the wings up with the fuselage so
> the two
> are not "fighting" each other for priority. That's total conjecture
> on my
> part however, and may be total hogwash, but I'm groping for an
> explanation.
> Troy does report a real improvement to his airplane though, and all
> that
> changed was his main wing and it's incidence to the fuselage. His
> tail size
>
> is unchanged, I think, but the tail's control surfaces were actually
> made
> smaller. Hard to say which one caused his improvement. If he did
> lengthen
> his h/s, that would certainly account for some of his improvement.
>
> Larry Flesner says his 24" longer KR2 has great stability too, and
> so does
> Jeff Scott (both have stock size tails, I think) so I still think
> it's safe
> to say that the extra length between wing and horizontal stabilizer
> makes a
> big difference. And you can't discount that most of us are far more
> aware
> of aft CG than our predecessors, so we're probably keeping it
> forward rather
>
> than aft, which helps there. But apparently there is also some real
>
> contribution from either the airfoils or the relationship between
> them that
> make the new wing "somewhat more stable" as Troy's experience would
> point
> out.
>
> It's hard to say for sure, but one thing that is for sure is that
> new
> airfoils have significantly less drag than the RAF48, and the
> AS5048/45
> gives a lot more room for fuel and aileron cables in the wings, not
> to
> mention stronger spar (due to the fact that it's taller), and there
> are
> other trade offs. So I can see no reason to build a new plane using
> the
> RAF48 other than you have a set of Diehl wing skins in hand already,
> or
> don't think you can spend the time to build the wings. Bill Clapp
> told me
> the other day at SNF that he built his wings in three weeks, but
> your
> mileage will almost certainly vary. I know mine did, but I also
> built
> different ailerons, controls, and flaps into mine. I really think
> the old
> line that the new wing hasn't proven itself doesn't fly anymore
> though.
>
> But to answer your question Ray, there is no shame in using the
> Diehl wing
> skins, and that's a great reason to stick with the RAF48, and finish
> your
> plane quicker. I think if you are building a KR2S, you will be
> quite happy
> with the stability, whether it has the new airfoil system or not...
>
> Mark Langford, Huntsville, Alabama
> see KR2S project N56ML at http://home.hiwaay.net/~langford
> email to N56ML "at" hiwaay.net
>
>
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