[NSRCA-discussion] Fwd: RE: Design Question

Tue Nov 10 19:07:46 AKST 2009

When it comes to Design + Engineering, there's no such thing as 
"overthinking". VBG

John Pavlick
http://www.idseng.com

----- Original Message ----- 
From: "Matthew Frederick" <mjfrederick at cox.net>
To: "General pattern discussion" <nsrca-discussion at lists.nsrca.org>
Sent: Tuesday, November 10, 2009 7:04 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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