Rib Lacing in the Prop Wash

[Birdseyeview]

I have a series 6 wing which I believe is the same as the series 5 and 7 (non-STI) wings. I laid out a good pattern on my wing top that misses all the internal structure. Starting at 4" from the trailing edge and working forward my spacing on the top is 3.5". The spacing on the bottom, starting at the same 4" forward of the trailing edge is 3 3/8". I'm not sure what the distance across the wing length is starting at the butt rib that accounts for the "prop wash" area. I'll cut the rib lacing spacing in half within that area. So, which cap ribs should be laced at half these spacing lengths within the "prop wash"? Looking for some enlightenment.

[efwd]

I would not consider Rib #3 to be within the prop wash. However, Rib 2 is and if your tugging on fabric at 2 then IMO you must consider #3 as well. Cosmetically you won't even notice the closer stitch. And, Lacing is fun.;)

[Birdseyeview]

Eddie, Thanks for the info

[efwd]

Before you act on what I suggest, certainly there are other opinions. I used Oratex so I used the closer spacing at Rib #2 but I didn't use any lacing on Rib #3 at all and I only put lacing on #2 behind the Tank where others put it on the under side of the tank all the way to the leading edge. One inch wide Rib Caps allow one to consider no lacing at all anyplace on the wing but it remains recommended by Poly Fiber and I believe most people lace in spite of it being OK to skip them if the fabric is attached well to the 1" wide cap strip. I don't recall ever seeing a KF without lacing. It just seems prudent to lace.

[Birdseyeview]

Eddie, Thanks for the additional good data. I'm getting the hang of gluing and shrinking the fabric. The Stewarts System I'm using is very simple, forgiving and it doesn't stink up my heated basement which keeps the wife happy. I've done lacing at Airventure a few times in the practice building but the moment I left I couldn't remember all the steps. I plan to study a few You Tube videos and practice on a sample before I lace the real thing. I'm looking forward to it. It's all been fun so far.

[Sink Rate]

Apologies if this has been answered elsewhere, but I was wondering if I should lace rib #1 & #3. Based on pictures, I don't see anyone stitching the butt rib (#1). #3 would require small holes to be drilled in the Hysol between the tank and the rib. I am using Oratex and I have glued the fabric to the top of the tank. (Model 7 SS)

[Dave S]

SR,

For Rib #1, considering that the fabric is shrunk, wrapped around and glued down to the inside edge of the rib, it is not going anywhere without rib lacing anyway - at least with polyfiber - can't speak to other covering systems which I have never used. It was no big deal to drill the hysol on #3 and lace that rib so that is what I did. # 2 rib was only laced behind the rear spar on our plane but securely poly tacked to the bottom rib forward of that.

After many years all is well with this in spite of my flying:o

[Sink Rate]

Thank you very much for the info, Dave. I'll proceed with lacing #3 as you mention.

[jrevens]

I agree with Dave. Also, the Oratex glue is supposedly stronger in peel, etc. than others.

[Sink Rate]

Thanks, John! I should have paid more attention when I looked at your plane a while back :o

[Sink Rate]

Apologies for the little digression! I saw on the forum that some used the poly fiber reinforcement tape under the rib-lacing on an Oratex covered wing. I still have that tape that came with the kit and I am curious if it's OK to go that route (mixing covering systems?!...). Alternatively, I could make tapes from left-over Oratex 6000 and Oratex hotmelt.

[bumsteer]

In the Tips & Tricks booklet from Better Aircraft Fabric, they say the Poly-Fiber reinforcing tapes are the most suitable for using with Oratex.

Rick

[Sink Rate]

Wow! OK. That answers it! Thank you very much, Rick!

I wish I had that Tips & Tricks booklet. Lars just sent it to me :p

[efwd]

Editing here, Crap, for some reason I went straight to the thread and only realized it now. I will leave the rest up so people have that little tidbit about the wax thread.

Lars and I had a lengthy discussion about the waxed, flat thread from Poly Fiber. He did not recommend it then and encouraged me to use the round stuff supplied by better aircraft fabric (him). He said if I wanted to use the flat waxed thread (it isn't available without wax)I had to get the wax out. Carl did that and he will likely advise how that was done. I did recommend that people strip the wax and use the flat thread because mine are quite apparent beneath the tape. The tape is prone to lift up off the surface if it has to encase the round thread so you have to use plenty of the glue to make "ramps" up and over the threads. Mine are all good but I bet Carls looks a lot better. If the wax is not stripped, the wax will melt and spread out from beneath the tape and onto the wing fabric. I guess this makes it look like you have dirty spots at every thread.

[Denalifox]

Editing here, Crap, for some reason I went straight to the thread and only realized it now. I will leave the rest up so people have that little tidbit about the wax thread.

Lars and I had a lengthy discussion about the waxed, flat thread from Poly Fiber. He did not recommend it then and encouraged me to use the round stuff supplied by better aircraft fabric (him). He said if I wanted to use the flat waxed thread (it isn't available without wax)I had to get the wax out. Carl did that and he will likely advise how that was done. I did recommend that people strip the wax and use the flat thread because mine are quite apparent beneath the tape. The tape is prone to lift up off the surface if it has to encase the round thread so you have to use plenty of the glue to make "ramps" up and over the threads. Mine are all good but I bet Carls looks a lot better. If the wax is not stripped, the wax will melt and spread out from beneath the tape and onto the wing fabric. I guess this makes it look like you have dirty spots at every thread.

I just finished my STi wing rib stitched with Oratex. I use the supplied reinforcing tapes and stripped the wax off of the stitching. Before applying 2" finishing tape I encapsulated each stitch with 2 coats of glue. It turned out fantastic! There was just enough wax residue to allow the knots to slide below the surface.

[tracstarr]

I've also use Oratex but did so without the rib lacing. I had a lengthy discussion with both Lars and an engineering person/team from the factory and with the 1" capstrip it was agreed that it was not required - as long as it was done right. Additionally I have the LLE adding to the total glued surface area in addition to the tanks. In my testing the fabric separates from itself catastrophically before any properly glued area lets go - and it took a lot to make that happen. I know that's not providing any proof of anything directly, but it does add to my confidence in the system. That said, there is no flight time as of yet - inspection is upcoming. Depending on where you live that might play a determining factor. Here in Canada if the manual says it's required (rib stitching) then you must have it unless the factory provides a letter otherwise. I built a 6, and there's no requirement in the manual for rib stitching with poly. I did have to get an exemption from the factory to decrease my seam size as per suggestions in the Tips & Tricks from Lars as it deviates from manufactures install manual for Oratex.