Slats vs VGs - beating a dead horse ?

by Michael Barrie

Jun 15

Hi all,

I've got my wings built to the point where I'm about to drill/cleco the leading edge skins. I'm getting cold feet about the slat vs VG debate. 

I have the brackets already built and clecoed on to the nose ribs as per the build manual. I have read the STOL Speed article on the slat/vg comparison and I am now hesitant to put my slats on and just leave my nose skins untouched.ive also read rockydogs build and others who've built thr slatted wing only to remove them after the fact.  Here are my thoughts so far:

Pros:

Part of the original design

They look really cool and sort of define the sky jeep

The aircraft WILL perform as advertised with them

Lots of data on flight Characteristics

Cons:

Extra weight

Extra build time

Decreased cruise performance 

May not provide any noticeable STOL characteristics compared to a vg.

Is there any other considerations I've not thought of here ? 

Thanks,

Mike.

  • up

    John Austin

    I've got hundreds of hours on my STOL 750 (you didn't mention what model you are building)  both with and without VG's and with and without slats.  Every point you made is spot-on.  On the STOL 750, my slats were 14 lbs total (painted) and if removed, that goes directly to increase useful load.  I gained about 6-8 kts cruise speed.  And, you are correct that the STOL performance is still quite good without the slats.

    The big difference is that the angle of descent/ascent is more shallow without slats, so slats do let you get into "tighter" strips although there's not that huge of a difference in landing or takeoff rolls.  So, if you're in to extreme STOL, you definitely want the slats.  My STOL 750 stalls very conventionally with slats off, and with slats on, you really can't define a definite stall - the descent rate simply picks up but it's still controllable.  The VG's lower the stall speed about 5 kts and help with controllability deeper into the stall.  As far as cruise speed, the old joke is that if you're looking for speed with a STOL, you've got the wrong airplane! LOL!  I saw no noticeable effect from the VG's on cruise.

    I do admit, the plane lost some of its cool "funkiness" with slats off.  I shaved my brackets back to 20 mm height so I would still have sufficient edge distance to remount the slats and made "intermediate" brackets to restore the slats to there original position when bolted back on.

    I've now got them back on with bigger tires and am playing more with the STOL again and having a ball!

    John

    N750A

    1

    Jun 15

    • up

      Bob Simmons

      It's fairly easy to switch between the two, so try both and use what you like most.

      Jun 15

      • up

        John Burns

        It is easy to take the slats off.  They do add to the fun factor and make those over tree landings easy.  https://youtu.be/X2Kkygbo-Tk

        1

        Jun 17