REFLECTOR: VG Lineup question

Thu Oct 2 21:05:33 CDT 2014

Having the VGs too high just increases the drag.  Don’t know how much, but they are draggy so smaller is better.  I believe the same goes for length - a longer VG makes a bigger hole in the air.  Who knows what is optimal - no one I am sure, but the formulas I give are certainly best practice.

David Ullman
541-760-2338
ullman at davidullman.com
www.davidullman.com

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Today's Topics:

   1. Re:  VG Line-up Question (John Dibble via Reflector)
   2.  Stupid pilot tricks/Nose wheel lock
      (Ron N VelocityXLFG via Reflector)

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Message: 1
Date: Thu, 02 Oct 2014 07:30:05 -0500
From: John Dibble via Reflector <reflector at tvbf.org>
To: Bob Jackson <bobj at computer.org>, Velocity Aircraft Owners and
	Builders list <reflector at tvbf.org>
Subject: Re: REFLECTOR: VG Line-up Question
Message-ID: <542D454D.3090508 at bluefrog.com>
Content-Type: text/plain; charset="utf-8"; Format="flowed"

Is it counter productive to have the VG height and length greater than what the calculations call for?

John

On 10/1/2014 11:21 PM, Bob Jackson via Reflector wrote:
>
> Thanks for the response, David -- and of course I don't mind you 
> posting my offline question and your response!
>
> It will be a few months before I've got my plane back up and flying 
> again to try any more experiments myself with the inlet VGs and 
> cooling.  It's also been an area of experimentation for me over the 
> past three or four years, but less focused on inlet VG's -- which 
> based on your results is looking like at least some misplaced energy.
>
> When I do my own experiments, I plan to also test the idea that the 
> top of the windshield is really the proper point to consider as the 
> front of the fuselage airfoil, rather than the aircraft nose -- due to 
> the discontinuity presented by the much steeper slope of the 
> windshield.  The windshield 'break' is about 6' ahead of the NACAs 
> (rather than 11' from the nose).  Working the 6' length through the 
> Reynolds number equation you provided results in an approximate 
> boundary layer depth at the NACAs of ~1.3" (rather than ~2.2").
>
> Velocity_GearUp_PlanView.jpg
>
> And using the alternative 1.3" boundary layer thickness and the design 
> rules you included in your write-up produces the following new layout
> dimensions:
>
> ·1.2" VG height
>
> ·3" VG length
>
> ·3.25" counter rotating VG spacing
>
> ·13" VG pair spacing
>
> Given these new numbers, my first try would be with three sets of 1.2" 
> x 3" counter rotating VG pairs, in a line about 20" in front of the 
> NACA inlets, which should place the outer pairs just outside of the 
> centerlines of the NACAs.  I would compare that with two sets (instead 
> of three) with each set exactly centered on the NACA inlets, or with 
> your suggested layout if I didn't get the big CHT lowering we're all 
> looking for!  I'm not sure I have the patience and time to construct 
> and conduct the full (really cool!) manometer experiment that you did!
>
> Thanks for your contribution to improved engine cooling!
>
> Bob Jackson
>
> N2XF XL/RG/XC
>
>

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Message: 2
Date: Thu, 02 Oct 2014 09:28:34 -0500
From: Ron N VelocityXLFG via Reflector <reflector at tvbf.org>
To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
Subject: REFLECTOR: Stupid pilot tricks/Nose wheel lock
Message-ID: <542D6112.6050001 at fastmail.fm>
Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"

I never have had any Aggressive shimmy . I have had a mild shimmy that seemed to be because of Unbalanced front wheel. After I balanced the front wheel I have had no Shimmy at all. Maybe it helped maybe just a coincidence .

  I never ran with more than 14 lbs of pull on the front wheel.

Now With shimmy dampener 4 lbs pull
Balanced front wheel  and wheel pants.

I like the shimmy dampener ...... I hate that I can not get full 360 rotation of front wheel!!
Real pain pushing the plane out of the hanger when the front wheel can not rotate 180 deg.

PS love being able to drive right into the hanger ....Love my Pusher  :)

Ron

On 10/1/2014 9:36 PM, Zach Krachinski (zachk at comcast.net) wrote:
> View/reply online 
> <http://VOBA.clubexpress.com/content.aspx?page_id=2161&club_id=495146&item_id=473695&message_id=1160891>       Reply 
> to forum at forum at velocityowners.com 
> <mailto:forum at velocityowners.com?subject=re:Stupid%20pilot%20tricks/Nose%20wheel%20lock%20%3C%3C$116089127017$%3E%3E>       Reply 
> directly to Zach Krachinski at zachk at comcast.net 
> <mailto:zachk at comcast.net?subject=re:Stupid%20pilot%20tricks/Nose%20wh
> eel%20lock>
>
> This is kind of ironic, but if any of you guys (or ladies) are on COPA  
> they just brought up the same nose wheel shimmy problem its in the 
> general discussion for free members, quite a lot of replies there 
> also.  They are saying the two main culprets are tension, and the 
> other is worn tires or low tire pressure.  I dont think i saw anyone
> mention that it could go back to the tires here?   Just thought Id let 
> you all know in case you wanted to see their discussion too.
>
> You have received this message as a member of: Velocity Owners and 
> Builders Association Change preferences (including opt-out): Online 
> Profile 
> <https://VOBA.clubexpress.com/content.aspx?page_id=13&club_id=495146>

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