Vertical stab rib stitch?

[DHinesCB1]

I've read this thread twice, and seem to remember reading it on the old forum too. I still dont think I can fully picture this. I built my verical stabalizer to plans, and since I have not yet started covering, I am trying to decide if I need to add something before hand. It is my understanding that the fabric is supposed to drape from the bottom rib on the verticle, to the top longeron. Am I missing something, or is this not optimal? I believe a couple thousand words would really clear this up for me, does anyone have a picture or two?

[alvinsager]

Hi Dave,
As Lyman said, there are lots of Hatz that have the fabric draped from the top rib down to the upper longeron with the fabric finding its own shape. Mark plotted the curve the fabric would find at the lower rib and made a balsa rib to that shape so that he can rib stitch without pulling the fabric down to the channel rib because that is what he wants it to look like (we have lots of choices).
Since the channel ribs in the vertical stab and the rudder are in line on my Hatz, I decided to do what Mark did with an aluminum rib riveted to the channel rib. That way, the ribs will be in line. Not nearly as easy, had to make a form block etc.
I have uploaded a picture of what I did. I found the old newsletter where it was said that attaching the fabric tight to the bottom of the vertical stab on a Tcraft was good for 5 mph. The author did that to his Hatz and claimed the same improvement, but that took a false rib probably following the line of the turtledeck. It was also claimed that the free shape of the fabric diminished the effect of the fin offset.
I don't think I made it to 1000, but this pretty much covers (pun intended) the subject. Bottom line, you have to please yourself.
Al

[mmcgrew]

Stitched and very happy with the results

Michael
N838MM

[mtaylor]

Well, I think what you're asking is about the trailing edge of the vert stab being the same width as the leading edge of the rudder? If so, yes. The rib I made begins flush with the leading edge, and ends flush with the trailing edge of the vert stab. The point was to create a rib that doesn't change the geometry of the fabric when it's stretched on the fuselage. It just gives you something to rib stitch the fabric to. I wanted some support of that fabric to prevent ballooning of the fabric during knife edge flight...! Don't laugh, I'll probably be trying that at some point.

Mark T



P.S. I also have a Lauzon frame.

[mmcgrew]

i stitched - and I am very happy with the results

Michael
N838MM

[DHinesCB1]

AH...makes perfect sense now. Thanks Al ! Great to see someone else at about the same stage as me, and also working in a garage. At first glance it looked like one of my pictures! This gives me something to think about now. I'd love to see after stich pics, of both ways of doing it...anyone?

[alvinsager]

Hi Dave,
We wont have to wait too long. I just finished up all of the wiring and the fabric is next.
Al

[mmcgrew]

Actually - Rib stitching changed the lay of the fabric very little. Before stitching the fabric ranged from 1/2" to 3/4" off of the lower tapered horz rib. Of course now it is tight to the rib. The break of the slope change is some what more pronunced and not as gradual. I hope pic helps.

Michael
N838MM

[DHinesCB1]

wow Michael...that curve is darn sexy! (yeah, my wife thinks I'm kinda twisted...takes a builder to relate). I had almost dismissed the idea, but am now reconsidering.