Laying out rib stitching (top verses bottom of wing)

[LSaupe]

Getting ready to rib stitch and see that I just cant lay out the same distances on the top vice the bottom (as I had hoped), due to the significant differences in arc length. How do you guys typically hadle this? At first pass I am thinking about laying out the bottom and them thansferring the top holes by putting a pointer through the bottom holes with a device to keep the pointer normal to the bottom surface.

How is this typically accomplished?

[Av8r3400]

My method: from the butt rib face mark your top surface (important one) use a vertical level (wing flat) or horizontal level (wing vertical) and mark bottom surface. Then measure bottom surface marks from trailing edge and transfer to tip end of wing. Snap chalk lines. Done.

Learned this from a Poly Fiber seminar.

[TahoeTim]

good tip.

I am wondering if it matters whether the lacing goes vertically through the wing. Would an angled lacing hurt anything?

[neville]

see pages 33 and 34 of the Poly-Fiber manual " how to cover an aircraft".
In essence you make a cardboard pattern of the shape of the wing, lay out
the stitches on the bottom, and transfer them to the top perpendicular to the cord, and use the pattern to mark top and bottom on each end of wing, then snap chalk lines. Kitfox sells the manuals at a very competitive price.

[ken nougaret]

Like Neville said, make cardboard template of rib, mark your parellel vertical lines on it, transfer marks to each end of wing, snap chalk line.

[jiott]

My method: Essentially the same as Av8tr3400 but I transferred the marks from the butt rib to two (for top & bottom) 1" wide strips of flexible fiberglass trimmed from the wingtips, flush with the trailing edge. Then transferred the marks from these strips to each rib-eliminated the need to snap chalk lines. One caution-when you first lay out the spacing marks you must check that your stitching will miss all internal structure, cross bracing, etc. It takes some fudging and adjusting of the spacing, but it is possible to find a layout that works for all ribs.

[LSaupe]

Perfect. Many thanks guys.

[kitfoxnick]

I use a piece of elastic that you get from a fabric store. Cut it to the bottom cord then stretch it for the top.

[BobRS]

Make a cardboard template and draw vertical lines at the recommended front to back spacing. If you cut out the spar holes you just need one and place it on each end of the wing and make pencil marks (top and bottom). Use a chalk line across the wing top and bottom.
http://www.teamkitfox.com/Forums/attachment.php?attachmentid=8544&stc=1&d=1425628077

http://www.teamkitfox.com/Forums/attachment.php?attachmentid=8545&stc=1&d=1425628077


This is what the rib stitching will look like when you're done. Buy the poly fiber movie if you haven't, and run it in slow motion to see how to stitch. It's really fun after the 1st 20 or so knots, but your fingers get cut with the waxed nylon when tightening the twine.

BobRS, Albuquerque NM
SS7, Rotax 914, almost done!

[HighWing]

Just curious, There is a recommended riblace spacing depending on typical airspeeds and whether or not the fabric is in the prop wash. My understanding is that the tendency to lift off the rib is greater on top where the higher speed air creates the lift. I wonder why the beginning spacing is done on the bottom which would increase the spacing a tad bit on the top. Wouldn't it be preferable to do the layout spacing on top and then make the adjustment on the bottom spacing?

[BobRS]

I just checked my builder's log. We used a 2.5" pitch between stitch lines, adjusted slightly for clearance around spars and other internal obstructions. We also stitched all ribs with the exception of the root, end and the portion of the wing containing the fuel tanks. We have a Rotax 914, so the 2.5" spacing between parallel vertical lines was the selected for higher airspeeds. I think our PolyFiber book is out at the hanger, so I can't double check, but that's what I recall. Frankly, the more important aspect is to achieve the nearly vertical alignment of the twine rather than using the top or bottom surfaces as your reference for deteremining which you use for the pitch distance. Note that, yes the top is a curved surface, but the 'chord' between the 2 fabric puncture points is the obviously the same top and bottom using template method shown in my previous post. If you stitch every available rib with this (2.5") distance you should be fine. Two other factors....our EAA Tech advisor has looked at this (he's a pretty detail oriented guy) and was satisfied. We also know the local FAA FSDO rep and he happened by the hanger a few weeks ago while the wing tips were off, and pretty much looked over the bird and was pretty impressed with how we've built it. It's still your call as the builder, but this was our process.

BobRS & Kitfox Kath
N104Y, SS7, Rotax 914
Alb, NM

[rosslr]

We laid out 2.5" on the bottom, levelled the wing horizontally through the centre of the front and rear spars and then used a vertical level to hold against the bottom mark and transfer top the top of the wing. slight adjustments needed to negotiate the spars but works out pretty well.

cheers

[Jch]

I used a 1" wide piece of the fiberglass wing tip that I had trimmed off and marked the spacing for rib stitches on that, then with the wing on a jig in the vertical, I placed the "wing shaped" fiberglass piece over each rib and punched my holes on each side of the rib, then went to the next rib and so on. The fiberglass piece was in one piece,closed on the leading edge and open on the trailing edge so it fit neatly over the front spare.