F-915 outboard seat ribs and F-904 bulkheads.

Anyone care to provide some input as to the installation of the F-915 outboard seat ribs? Manual says they get match drilled later on but I haven't been able to find when. At what point are they riveted in. Also, what has been the process for fluting the curve in them to match the curve of the holes in the bottom skin?

Regarding the F-904 bulkheads: On the bottom flanges of the fore and aft bulkheads that attach to the bottoms skins, there are four holes that are machine countersunk through the center section skin (F-976) and into the flanges that also attach the forward section floor stiffeners. Am I correct in assuming that the rest of the bottom flange holes on the bulkheads will be machine countersunk in the normal fashion and the skins dimpled? Still scratchin' my head!


Rick Schwandt
Fuse (Center Section)

this is same part as on -7 so I can take a stab...

anyways, making the curve is where the artistic touch comes in. just flute the rib until it takes up the required shape. takes a bit to get it right, but it's really not a big deal... it's just a bit time consuming to fit it after each iteration etc. Rougly mark where the holes will come and then flute inbetween those marks. You can rivet it just about any time, but I think I did it after match drilling with side skins (easier to debur the rib etc..)

I just countersunk forward bottom skin (it's thick enough for that) so I didn't do anything on 704 flanges or center bottom skin. Less kludgy, IMHO

Oh yeah, the 5/8" hole they have you make (by enlarging the tooling hole) doesn't match up wtih side skin hole meant for that... so if you haven't done that yet, then wait till you cleco on side skins...

Hey Guys,
Still looking for some additional input here! Thanks Radomir for yours.

Rick Schwandt

rjsflyer said:

Anyone care to provide some input as to the installation of the F-915 outboard seat ribs?

Click to expand...

I remember waiting and waiting for the instructions to mention riveting those ribs. I kept them clecoed for a long time. I think I finally riveted them before attaching the side skins. I don't remember any particular reason why they couldn't be done earlier.

Ditto about Radomir's comment on the wiring/pitot tube holes. They don't line up.

Also, what has been the process for fluting the curve in them to match the curve of the holes in the bottom skin?

Click to expand...

Draw a centerline on the flange, mark the locations of the holes, and flute between the holes until the centerline lines up in the skin holes.

Am I correct in assuming that the rest of the bottom flange holes on the bulkheads will be machine countersunk in the normal fashion and the skins dimpled?

Click to expand...

The standard rules apply. Dimple < .040, countersink > .040, builder's preference for .040. I dimpled the skin and spar flange. If I remember right, the flange is .040, so you could dimple the skin and countersink the flange. For tricycle gear, the instructions mention something about countersinking underneath the gear mounts, but I found there was plenty of clearance under the mount.

Hope that helps,
Dave

Thanks for your input, Dave. I decided to machine countersink the bottom flanges of the center bulkheads and dimple the skins. I think I'll also take a deburring tool and remove a little bit more material in the dimpled holes in the center skin so that the forward skin will sit a little farther into the dimple.
I also checked out your website, looks pretty good. I wish my better half would help me with the project, but no interest at all.

Rick Schwandt
Fuse (center section)
www.rjsflyer.com

No better half help here either.

I can identify with the lack of better half not helping. She doesn't complain at all about all the time I spend of the project so I'll give her that. But she doesn't have the confidence to buck a rivet. If she goes into it with that attitude then sure as shootin' she'll bruise one badly. If the confidence is not there then we're both better off with her staying away from it.