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Permalink Reply by John Austin on June 15, 2024 at 2:17pm

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

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Permalink Reply by Michael Barrie on June 15, 2024 at 7:40pm

Hi John, I really appreciate your input. You make an interesting point with descent rates/angles. I think when we consider STOL , at least for myself I'm always thinking of how fast it gets off as opposed to ability to get into tighter spots landing. 

For clarifications sake I am building a 701. My main intention is to use it for back country access, gravel bars, fishing, hunting, camping etc. When I bought the kit it seemed the closest thing to my ATV that I could fly. 

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Permalink Reply by Bob Simmons on June 15, 2024 at 7:58pm

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

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Permalink Reply by John Burns on June 17, 2024 at 8:41pm

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

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Permalink Reply by Michael Barrie on June 17, 2024 at 9:22pm

Thanks for the video John. Great looking 750!

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Permalink Reply by Michael Barrie on June 28, 2024 at 9:36pm

I just figured i would update this discussion. I unwrapped my nose skins after finishing up the work on the lower skins/trailing edge skins and see that the good people at zenith have already made CNC cuts in the nose skins to accommodate the slat bracket protruding through. So, with that work already done i believe i will leave the brackets in place and run the slats as per the original design. 

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Permalink Reply by Jim and Amelia Isaacs on June 29, 2024 at 11:28am

Good call given your intended mission. It’s not a cross county airplane design anyway. With slats I routinely operate my 701 out of my 1,000 ft. home field with mature trees at both ends. Once you are comfortable with the airplane, with slats you can use quite steep stabilized approach angles. Also, not that it matters now but add to the list of Cons of removing the slats “a reduced c.g. range” and for Pros “slipping with slats will drop you like a stone” 

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