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Permalink Reply by LUCAS SILVA on February 4, 2023 at 11:30am

No matter I have the stick full back

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Permalink Reply by Matt Pope on February 4, 2023 at 2:35pm

A few thoughts… Do you have vortex generators under the elevator? Those could help. I think there is a lot written about that in the 701 forum. Fences at the ends of the horizontal stabilizer and a fairing between the horizontal stabilizer and the fuselage can also help to direct the airflow over the elevator and make it more effective. Also using power to increase airflow over the tail surfaces could help. A forward center of gravity might contribute to the problem, or if you have larger tires on the main gear compared to the nose gear and haven’t extended the nose gear strut then the wing’s angle of attack could become negative as the nose wheel nears the ground, forcing it down. 

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Permalink Reply by Jim and Amelia Isaacs on February 5, 2023 at 8:28am

Until you sort this out keep your speed up at touchdown, runway length permitting, or carry some power all the way to nose wheel touchdown.  Don’t want a prop strike.  You have to fast forward through some of the off topic stuff but there’s a wealth of information here https://www.homebuiltairplanes.com/forums/threads/what-i-learned-ab... that will help.  

As Matt said the vortex generators on the elevator will help, also if you have a flat cabin roof replacing that with a curved roof (the “beanie mod” in the link above) helps significantly as well, also level the aircraft with a string per the drawing and check that the Horizontal Tail (HT) is at a minimum also level with the aircraft. A degree or two down at the HT leading edge is OK and will help, but any amount of “up” at the HT leading edge as compared to the aircraft fuselage will degrade your ability to keep the nose trimmed up, especially with flaps down.  Speaking of flaps, check your flap down deflections are per the deflections drawing.  What flap setup do you have? Older 701s have a barn door full down flap setting I think it’s about 40 degrees but Zenith changed to 15 degrees full down for several reasons including your situation. Also confirm you’re getting a full 35 degrees up on your elevator you need every bit of it. 

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Permalink Reply by John Austin on February 8, 2023 at 8:58am

If the "flat roof" is stalling and blanking-out the tail (easily checked with some tuft testing), it's much easier to install (at least it was on my Ed 1 STOL 750) delta VG's than to do a beanie mod (especially if you don't need additional headroom). Phil Smith came up with the original idea and implemented it on his 701: Beanie Mod - Not.

As to effectiveness, my installation was corrupted by the fact that I had already highly modified the tail with fences, elevator tip extensions and HT-fuselage fairings.  Although repeated tuft-testing demonstrated the delta VG's were effective, I really couldn't see significant performance improvement since my previous mods had worked so well (it's like adding "power steering" to the tail!), but I left them installed since I figured that anything that reduces turbulence/drag is good and besides that, they look cool! LOL!  However, Phil did report improvement with the delta VG mod alone on his 701.

John

N750

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