Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml
Date: Thu, 25 Sep 2003 23:11:29 -0400
Message-ID: <redirect-2604245@logan.com>
From: "Eric M. Jones" <emjones@charter.net>
References: <list-2604046@logan.com>
Subject: Re: [LML] Re: Gain a couple of knots
MIME-Version: 1.0
Content-Type: text/plain;
	charset="iso-8859-1"
Content-Transfer-Encoding: 7bit

Larry,

> When I was building I was told by some compuserve Avsig guys that they
> ran out of forward stick at higher speeds.

That would be consistent with having too much "anti-lift" I think.

> My intent would perhaps be a little more conservative than yours in that
> my tank would be empty for takeoff and landing.

I'm with you. But keep it simple.

> I think I'm sitting with a touch of forward stick or
> down elevator in fast flight.
>I look at the tail to see 1/8" up on the elevator weights.

 .......if I understand you; the elevator is trying to negate the
"anti-lift" by forcing the tail up and the nose down.

> I surmised that adding weight aft may increase speed.
> However, I think it would also increase drag through more forward stick
> of a drooping elevator.  Thence, this may permit no actual speed
> benefit.

...again if I understand what's happening; when the airspeed increases, the
(negative airfoil) horizontal stab increasingly tries to pull the tail down
(anti-lift). This forces the pilot to apply forward stick to get the tail
back up, thus raising the elevator counterweights (and inducing drag). By
adding weight to the tail (however you want to do it) or even changing the
stab angle (like the MD-80), the tail has all the downward force it needs
with neutral stab/elevator aerodynamics. Remember the only purpose of the
horizontal stab is to control the pitch of the main wing. You could control
the pitch with a big sliding weight if you had enough power. And the stab it
is a negative airfoil is so that it rotates the nose down when it stalls.
Until about 1930 (maybe?) the stab stalled and pitched the nose UP in many
aircraft. Then bad things happened too fast for casual comprehension.

None of this should surprise anyone. But I wonder if the renowned reflexive
wing in the Lancair is just a way to prevent too much tail drag. (Don't
email me on this!)

Best regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
Phone (508) 764-2072
Email: emjones@charter.net