Hi Jack

Thanks for the explanations, I have the Tru-Trak sorcerer installed in my plane and was planning the Yaw damper as it is said that the 4p changes yaw with every speed change, so I am assuming the yaw damper together with the auto trim would correct this issue, right?

== Ronald

From: J H Webb <airmale4@yahoo.com>
Reply-To: Lancair Mailing List <lml@lancaironline.net>
Date: Thu, 30 Jun 2011 15:06:20 -0400
To: <lml@lancaironline.net>
Subject: [LML] Re: Ventral Strakes, do they reduce performance?

Ron,

    Sorry it has taken so long but I have been busy. You have asked several questions, and on the question of Ventral fins, I have had installed Ventral fins on several LIV's. The need is much greater for the LIV-PT but there is an improvement in both piston and turbine models. The little dual fins are not as effective as one larger single fin. Plus the drag seems to be lower. I have designed a single fin shape that works well, no noticeable impact on cruise speed.

I did notice a slight speed reduction with the twin Ventral fin taht are used on several LIV-PT's.

  Clark Still's aircraft is a good example of a PT with the single fin Ventral fin, on that airplane we made a very significant improvement in directional stability.

     On the question about yaw dampers, the yaw damper is very helpful when it is a high frequency unit with no feedback in the rudders. Unfortunately hte yaw dampers available currently are on limited value plus the current units that connect directly to the rudder increase the rudder friction band significantly making the airplane more difficult to master yaw control. The ideal installation would a unit operating a separate control surface such as the trailing edge of the ventral fin.

Jack Webb
L360, LIV

AeroSpace Engineer BSAE
FAA Designated Check airman for C421, C404 & C310
ATP, CFI Airplanes & Instruments, Multi, & Sea
Numerous Jet Type Ratings
Experienced Experimental Test Pilot both multi and single engine aircraft
Former Chief Engineering Test Pilot for a Major Manufacturer

Corporate Chief Pilot for Construction company
Ohio

Flying is the perfect vocation for a man who wants to feel like a boy, but not for one who still is.

---

From: RONALD STEVENS <ronald@sdc.com>
To: lml@lancaironline.net
Sent: Monday, June 27, 2011 7:34 AM
Subject: [LML] Ventral Strakes, do they reduce performance?

Hello guys

Me again, I just had my first lesson with the Lancair 4p (with JC) and when I took off the plane was wiggling its tail like a happy dog LOL Nothing scary, but this I can imagine could be annoying for passengers.

Now I was looking on the internet and found that Ventral Strakes  were used to fight against those 'yaw' effects.

It suppose to help with turbulence, go-arrounds, full power take offs as well.

My very near future plane (we are almost closing ;) is a newer one, so the tail section was already updated to the latest. 

But looking at my passengers (I fly with my Son and Girlfriend a lot) this could be disturbing for them and I was already thinking of installing the Yaw damper (I have the tru-trak sorcerer) and perhaps also installing those Ventral strakes.

Does anybody have experience (before and after) with those? And would you recommend those? 

Thanks — Ronald Stevens (Cirrus 1100 hours, Velocity 250 hours, Lancair 4p student now with 1 hour LOL)