lml@lancaironline.net Mailing List Archive

Colyn,

I have not experienced the nauseating wig wag in or out of turbulence. I would be interested in how many IV-P pilots have "nauseating wig-wag" that needs to be addressed.

I do know many IV-P vertical stabs are not straight. After building my IV-P by the book, I found that the vertical was canted 3.5" to the starboard side. It was then rebuilt so the tail was straight. I know other builders that also found and corrected this deficiency. Is this playing a role? I don't know.

I am certainly interested in what others have experienced.

Craig

To: lml@lancaironline.net
Date: Thu, 30 Jun 2011 15:06:20 -0400
From: colyncase@earthlink.net
Subject: [LML] Re: Ventral Strakes, do they reduce performance?

Craig,

I may end up in the same place. There are certain turbulence conditions where you get kind of a nauseating periodic wig-wag. It would be nice if the yaw damper would help with that.

Colyn

On Jun 30, 2011, at 7:51 AM, Craig Gainza wrote:

Ron and Colyn,

After almost 800 hours on our piston IV-P (many with back seat passengers) my bigger concern would be the added weight in back. My opinion is that strakes and yaw dampers add unneeded aft weight. Ron, I think you will feel comfortable with the yaw stability after a few more lessons.

I have not had any complaints from back seat.

After similar yaw damper issues as Colyn, Tim Ong suggested I remove my yaw damper. I removed it after year one and never missed it.

Craig Gainza

To: lml@lancaironline.net
Date: Wed, 29 Jun 2011 07:34:46 -0400
From: colyncase@earthlink.net
Subject: [LML] Re: Ventral Strakes, do they reduce performance?

Ronald,

I had the Mike Custard ventrals and I have to say the plane was quite stable in yaw. e.g. better than a Mooney Rocket.
However, I also flew N409L in training which is a straight IV and didn't notice any big problem with yaw stability.
That said, I road in another IVP back seat on a bumpy (thermals ) day and didn't like the ride at all. Not sure if it was the pilot
or the airplane.

I am unable to say if the Mike Custard ventrals add a lot more drag as I never flew my plane without them. You might want to get some aerodynamic analysis if you go that route. Mike's fins were definitely designed to solve a real problem with the turbines so if an argument could be made that ventrals have any use on a piston it could probably also be made that those big dual fins are overkill.

I think I agree with Bob that you don't need a ventral fin for cruise comfort.
My interest in them was somewhat speculative and in relation to stalls. The thought was that the vstab is largely blanketed by the wing at high angles of attack so that a ventral fin might be more effective for avoiding a yaw departure. I will probably never know the answer to that but I will note that the Columbia 400 has a ventral fin.

As far as the yaw damper goes. I have a Sorcerer with the yaw damper. So far i haven't got it do anything useful in turbulence. I'm still working with Tru-Trak on that.

Colyn

On Jun 27, 2011, at 7:34 AM, RONALD STEVENS wrote:

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)