[NSRCA-discussion] Fwd: RE: Design Question
Nat Penton
natpenton at centurytel.net
Tue Nov 10 16:17:02 AKST 2009
I am not going to contribute to this discussion, as much as I enjoy the
subject, for one reason - I DON'T TYPE - and widespread lack of knowledge
can make the subject interminable <G>.
As to stab placement relative to wing ( forgive me Don Lowe ) it is not
critical, within limits. Theory says the downwash is a tube of air the
diameter of which is equal to the wingspan. It is evident a T- tail, though,
would present rear end rolling drag and rear CG problems.
We know from past experience that low and mid wing airplanes can both be
well trimmed. Look at Dick Hanson's designs.
Think about this. Most designs have the wing at 0.5 positive to the T/L.
This means that upright we fly with about 0.2 downthrust and inverted with
about 0.8 deg upthrust. IMO this creates minor ( subtle ) problems in the
half roll, also power on / power off.
Nat
----- Original Message -----
From: "Matthew Frederick" <mjfrederick at cox.net>
To: "General pattern discussion" <nsrca-discussion at lists.nsrca.org>
Sent: Tuesday, November 10, 2009 6:04 PM
Subject: Re: [NSRCA-discussion] Fwd: RE: Design Question
>I overheard Nat at a recent contest stating he felt the horizontal stab
>placement relative to the wing chord is fairly irrelevant as long as it's
>no further than 1.5 inches from the line, and anything beyond that will
>cause undesirable results. I'm not saying I agree or disagree with that
>assessment, just take it for what it's worth. I feel he over-thinks things
>at times, but the true test is in the trimming and flying anyway.
>
> Matt
> ----- Original Message -----
> From: "Koenig, Tom" <Tom.Koenig at actewagl.com.au>
> To: "'General pattern discussion'" <nsrca-discussion at lists.nsrca.org>
> Sent: Tuesday, November 10, 2009 3:13 PM
> Subject: Re: [NSRCA-discussion] Fwd: RE: Design Question
>
>
>> Hi Jim and all,
>>
>> Jim.....enjoy those long winters, have a hot cup of coffee....and realy,
>> I mean really, think about what Bryan tells you. It is a brain twister
>> and can be confusing. But...he is right in everything he tells you. I
>> realise there are people out there who do not agree with Bryan, and that
>> is fine, but my advice is to have a read of his article-if only for
>> interest.
>>
>> If I had the time, and my ability to express myself were better-I would
>> try to explain some of my design ideas. But I simply suck at that-hence
>> my initial response, just go for it.
>>
>> Another genius to ask(besides Bryan) would be Nat Penton...he will also
>> make your head spin! A very learn'ed man indeed.
>>
>> Draw a line on a sheet of paper as your Datum, mark out 2 meters and go
>> for it. Better still, use some CAD package.
>>
>> PS. Make it pretty-or you wont want to fly it!! Also-keep us informed how
>> you are going. I certainly am interested in your project, maybe others
>> are too.
>>
>> Tom
>>
>>
>>
>>
>> -----Original Message-----
>> From: nsrca-discussion-bounces at lists.nsrca.org
>> [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of
>> shinden1 at cox.net
>> Sent: Wednesday, 11 November 2009 7:48 AM
>> To: General pattern discussion
>> Subject: Re: [NSRCA-discussion] Fwd: RE: Design Question
>>
>> Ok
>> Bryan
>> ---- shinden1 at cox.net wrote:
>>>
>>> > 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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>>>
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