[NSRCA-discussion] Fwd: RE: Design Question

[shinden1 at cox.net]

> From: "J N Hiller" <jnhiller at earthlink.net>
> To: <shinden1 at cox.net>
> Subject: RE: [NSRCA-discussion] Design Question
> Date: Tue, 10 Nov 2009 09:51:44 -0800
> 
> Bryan, I find it hard to believe that vertical wing placement doesn't affect pitch trim. The wing especially a thick one contributes significantly to total drag and any offset between the center of drag and center of thrust would create a rotational moment that would need to be balanced with H-stab / elevator trim. Maybe it's insignificant compared to other factors. This is what I'm trying to understand.
> Yes CG is a significant contributor. I've been able to change vertical pitch by changing the CG and wing incidence, forcing a H-stab / elevator trim change. CG placement is a whole different issue as is weight in the extremities such as wing tips, nose and tail.
> Thanks.
> I'm really interested in this aspect of pattern, good thing, winters are long here.
> Jim
> 
> -----Original Message-----
> From: shinden1 at cox.net [mailto:shinden1 at cox.net]
> Sent: Monday, November 09, 2009 7:14 PM
> To: General pattern discussion
> Cc: J N Hiller
> Subject: Re: [NSRCA-discussion] Design Question
> 
> Hi Jim
> The vertical wing placement has no effect on pitch trim,,NONE !
> what does is,the incidence and C/g. Don`t even worry about it.
> However it will effect  Dihedra you will need to move the wing after the test flights. or rebuild a new one with the right dihedral or, Mix it out.
> Rudder angles ,sweep, or position ,has a tiny effect ,so little it`s not worth worrying about .draw something that looks good.
> Just build your airplane and adjust to what it does not do well.
> your not going to hit it on the first try,but the effort will be worth the Learning and enjoyment, in a self designed model.
> There are so many dynamics involved in designing your first airplane
> you cant possibly think of them all on the first attempt.
> just  have fun and build a light pretty model.
> Bryan
> ---- J N Hiller <jnhiller at earthlink.net> wrote:
> > Thanks Lance. I don't want to stray too far from proven relationships but
> > understand there are many variables rendering each design different.
> > I presently have the wing located 1/2" below a centerline through the H-stab
> > and engine centerline. The stab is about 1/2" above the tail tube centerline
> > and positioned about 1/4 the height of the V-stab.
> > Both the wing and stab will be adjustable and previsions are included for
> > changing thrust angles. Tweaking these angles should effectively change the
> > flying height of the tail but the wing offset remains about the same.
> > Other than changing the vertical center of drag what are the pros and cons
> > associated with positioning the wing higher or lower. I'm thinking the
> > vertical center of drag relative to the thrust line can contribute
> > significantly to pitch trim. Is it a major influence?
> > Before beginning to cut parts it occurred to me that the design /
> > construction detail offers considerable leeway in vertical wing placement,
> > maybe as much as an inch higher or lower from the -1/2 presently planned and
> > changing the wing location later will require major surgery.
> > I guess what I'm really looking for is more understanding of the effect
> > vertical wing placement has on pitch trim. I guess I asked the wrong
> > question. Any thoughts on this will be helpful.
> > Thanks
> > Jim
> >
> > -----Original Message-----
> > From: nsrca-discussion-bounces at lists.nsrca.org
> > [mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of
> > patterndude at tx.rr.com
> > Sent: Monday, November 09, 2009 2:38 PM
> > To: General pattern discussion
> > Subject: Re: [NSRCA-discussion] Design Question
> >
> > That's all?  There a number of design issues we face in pattern where
> > there's little documentation readily available. This is one, KE flight is
> > another, wing incidence and engine thrustline effects in 4 axis flight is
> > another. The more I think about it the more I think of.
> >   There's no one answer and anything between the chordline and thrustline
> > can be made to work by changing rudder shape and incidence. I settled on a
> > quarter inch above the chordline and then adjusted the rudder to allow a
> > trim incidence near zero so inverted flight is more effortless.
> >
> > Lance
> > AeroSlave
> > Sent via BlackBerry by AT&T
> >
> > -----Original Message-----
> > From: "J N Hiller" <jnhiller at earthlink.net>
> > Date: Mon, 9 Nov 2009 09:36:13
> > To: NSRCA Mailing List<nsrca-discussion at lists.nsrca.org>
> > Subject: [NSRCA-discussion] Design Question
> >
> > Hello all.
> > Here's a topic for discussion that I'm personally very interested in and may
> > be of interest to others.
> > I'm working up a new pattern design and would appreciate comments regarding
> > the vertical placement of the wing and thrust line relative to the stab
> > centerline.
> > I not only would like to know what the vertical offset is on modern pattern
> > designs but how the vertical location affects flight trim, and why?
> > Thanks all.
> > Jim Hiller
> >
> >
> >
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