REFLECTOR: Vortilions and/or VG's?

Scott Derrick scott at tnstaafl.net
Tue Jul 19 22:17:00 CDT 2005


jim,

I'm confused and a bit concerned about your statement  " I have since 
taken them off the main wing (left them on the canard)".  The intent and 
ABSOLUTE requirement for VG placement to reduce stall speed is to reduce 
the stall speed the same amount on the canard and the main wing, so you 
don't move the lift relationship between the main wing and the canard  
into a deep stall area.

We always want the canard to stall first.    Always, its kind of a prime 
rule in canard planes. What the difference is in speed I don't know, but 
I would think its one of those, the more the merrier kind of rules.

By putting VG's on your canard you have lowered its stall speed. By 
omiting VG's on your main wing, your main wing now has the original 
stall speed to be a match with your un-VG'd canard.  But since you have 
VG's on the canard, you have now reduced the stall speed separation 
between the canard and the main wing.  Possibly in some flight attitudes 
your main wing may stall first?

I think this is a very dangerous thing to do.

Scott

Jim Sower wrote:

> My 173 with vortilons and lower winglets wallows a lot below about 85 
> kts.  I carried 80 kts on final until I installed VGs.  Went to 75 kts 
> final, 70 over the fence and 65 or less touchdown with what seemed 
> like about the same roll authority.  I have since taken them off the 
> main wing (left them on the canard) and one of these days will put 
> them back on and do a more detailed before-after test.  I also sealed 
> my aileron hinge gaps when I put on the VGs, and that has have a lot 
> to do with the improved in low speed roll authority.
> It'll take some time to get decent test data for VGs and gap seals ... 
> Jim S.
>
>
> Ron Brown wrote:
>
>> I do have the lower winglets.
>>
>> I have the same wings as Jack so I think I will try flying without 
>> the VG's and Vortilions and see how it compares with VG's.  My 173 
>> handled well with the VG's on short final.  I do lead with rudders 
>> when it is gusty or turbulent around the trees near the runway.
>>
>> I'll let you know my opinion in a week or two.
>>
>> Ronnie
>>
>>
>> ----- Original Message ----- From: "Jim Sower" 
>> <canarder at frontiernet.net>
>> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>> Sent: Tuesday, July 19, 2005 5:28 PM
>> Subject: Re: REFLECTOR: Vortilions and/or VG's?
>>
>>
>>> Oooops - I misread your message as NOT having lower winglets.  Mea 
>>> culpa
>>>
>>> Jack Sheehan wrote:
>>>
>>>> Maybe since I do have the lower winglets the vortilons would not 
>>>> have effect. I really don't have much experience in other 
>>>> Velocities but Scott Baker has flown mine and H e didn't think I 
>>>> was missing much or if he did he never said anything. The airplane 
>>>> takes a little rudder in the turns at about 90kts and lands fine at 
>>>> 80kts.
>>>
>>>
>>>
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