Factory Ribs

[geraldmorrissey]

Getting close to final assembly of my Patrol wings and have a question regarding the factory center ribs. When placing a full size (uncut) rib on the mylar it is difficult to get a best fit. If I place the aft end of the rib on the aft spar C/L, the forward edge of the rib is .150 aft of the fwd spar C/L. At this location the fit is pretty good. If I slide the rib fwd, .100 the fit is still pretty good. Trying to check a bent sheet metal rib to a mylar is an exercise in futility. The center ribs have to be accurately located fore and aft to maintain the airfoil shape and I don't want to rely on a couple of pieces of sheet metal clamped to the spar web flanges and the rib flange to locate the ribs position. If I had a measurement from the center of the fwd tooling hole to the aft face of the main spar web I could zero it in. Mark G could you get that measurement from the factory? Anyone else out there confident in the placement of their factory ribs got a measurement?
Thanks
Gerry
Patrol #30 wings

[Mark Goldberg]

I will call the factory tomorrow and see if they can give you some advice. My general feeling is that if the ribs are placed all in the same position - it will be fine. That is assuming the spar web flanges flow nicely into the ribs on both upper and lower surfaces. I would be trial fitting the ribs with your spars/spar webs. Not the mylar. If I am understanding your comments. Mark

[mswain]

I'm not sure what the cap strip thickness schedule is on the Patrol, but the 4 place factory ribs were .125 short front & back from a full size center rib. This made for no trimming on the aft end and no trimming on the front where the cap strip was .125. Out towards the tip where the cap strip ends, there was a gap of .125 and where the cap strip was .25 I had to trim ~.125.

To Marks point, as long as you are consistent....I don't think it is going to matter. I used the simulated skin method when lining the rib up on the rear spar. There is not much movement on the main spar since it sits between the flanges. The fit-up of the factory ribs was real nice.

I think it's more critical to get the spars perfectly spaced, parallel to each other and level, it will ensure the skins go on without a hitch. I used a thin stainless wire stretched tight over my jig as a reference. I made sure the spar web of the main & rear were exact measurements to the wire along the entire length.

[Mark Goldberg]

OK Gerry. I had a conversation with the guys who locate our ribs while assembling the wing skeleton. The have a routine which is probably not useful for you. For the two inboard root ribs for example - they trim .200 from the front side & .200 from the aft side of the main rib.. This changes of course as they move outboard. They do have a piece of plywood that you could call the female part that a forming block is cut out of. They place it on the top of the main & rear spar flanges, and put each main rib up against the wood (shaped like the upper wing skin) when they first clamp the ribs in place.

I think my first post from yesterday is more or less correct. I doubt honestly that you could get the ribs so out of whack that it would be noticeable on the upper wing skin. But if you want to take a measurement from a tooling hole or lightening hole to the main spar web - that kind of consistent placement would certainly result in ribs that were well placed. Good luck. I hope I have said something useful for you. Mark

[geraldmorrissey]

Thanks to all that responded. I guess all this is not an exact science as much as I'd like it to be. Mark, I really like the idea of a female upper surface check template to locate the ribs. I'll try to build one off my master rib template. Any router wizards out there with a good idea of how to do this, please check in. I've got a pretty standard MDF master template of the whole rib profile.
Thanks
Gerry
Patrol #30

[Mark Goldberg]

I think tracing the upper skin using your form block on MDF or plywood and then cutting it out with a jig saw would give you what you want. For me - no need for a router wizard. MG