REFLECTOR: Vortex Generators

[john at velocityaircraft.com]

VG's can go on the main wing only, canard and main wing but not the canard only unless specified by the factory.  You dont want do as Larry said an stall the main wing first.  If you are landing at 97kts then you have something else wrong with the plane though.  First check pitot static and make sure they are correct.  After that, make sure you have correct throws for the controls.  26-28 degrees trailing edge of elevator down and 22 up.  If you are getting over 28 degrees down you are stalling the canard.  If you are only getting 15 degrees trailing edge down then you aren't getting the full effect of the elevator.  

Unless your plane is very nose heavy empty (100 plus pounds) then you should be seeing between 80-85kts down final.  At 97 your float and landing roll must be fairly long not to mention brake fade and tire wear.  If you are getting the correct throws then check incidences on the wings and canard.

As for the vortilons.  The plane is NOT unsafe without them as testament to hundreds flying without them.  You will notice the plane handling to increase a little at slow speeds due to them reducing span wise flow under the wings.  We don't put them on ours so I don't have to clean around them and people hit them at shows (same as the VG's).  If you feel like the plane is squirrely then you can try putting them on and seeing if that helps a bit.  The same is with the winglet bottoms, they do a similar thing to help prevent the air from dumping over the tip which also helps the plane fly straighter when slow.   

John


-----Original Message-----
From: "Lawrence Epstein" <ljepstein at hotmail.com>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Date: 05/19/14 07:01
Subject: Re: REFLECTOR: Vortex Generators

I would not put VG's on the Canard without also putting them on the main wing. (without some real engineering input). 
If you do put them on the canard, be very careful about your flight testing. 


A main feature/requirement of a canard aircraft is that the canard ALWAYS stalls before the main wing. If you enhance the lift of the canard, the main wing might stall first, leaving you in a deep (unrecoverable) stall.


Larry Epstein
173 FGE
N58LV
 
 

On Sun, May 18, 2014 at 11:42 PM, Brian Michalk <michalk at awpi.com> wrote:
After doing my foreward CG tests, I find that my biggest concern is running out of elevator authority when flaring to land.  Flying in my buddies V, and also the trainer, I don't recall speeds as high as I am maintaining on final.  At 110mph (96 kts) final, by the time I land, I suppose I'm down to 100mph, and at forward CG of ... well, I can't find my spreadsheet at the moment, but it's probably close to 115 inches.

My question is I am wondering if VG's on the canard will give me some better elevator authority.  I like not having to worry about breaking them off now, so if the bother is worth it, I'll try them.
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