I've read a bunch of posts by folks that had it come out less than straight and I really really really didn't want to do that. Very happy with how it came out.
The normal sequence of events (this applies to pretty much the entire airplane) is fabricate any required parts, cleco them all together, do all the match drilling, then take everything apart, deburr any remaining rough edges and all drilled holes, then machine countersink and dimple appropriately. Once you've done all that, then you put it back together and rivet.
First you rivet the nose ribs and hinge brackets together. There are two nose ribs back to back, with two hinge brackets and a thick spacer in between. All 5 pieces get riveted together as a unit, then are riveted to the spar.
Nose rib/flap bracket assembly.
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| From Ailerons and Flaps |
Once all the nose ribs/brackets are put together, they get riveted to the flap spar.
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| From Ailerons and Flaps |
Once the nose ribs and bracket assemblies were in place you rivet on the FL-905 flap ribs.
The thick plate on the end is FL-906B plate. The flap actuator mechanism connects to this plate to move the flaps. The area is reinforced with the FL-906A angle and the rib, spar and nose ribs are riveted together. If you look at the ribs you'll notice none of the holes are dimpled. I somehow missed that when I was going through my checklist prior to riveting.
Of course I noticed this *after* I'd riveted the nose rib/hinge assembly and the main ribs into place. So I had about a 6 foot long structure with some very tight holes, all of which had to be dimpled.
Thank goodness for the tight spot dimple tool I got from Cleaveland Tools. I hung this dude way off the table corner at a 45 degree angle and was able to work it in to all the tight spots and get the dimples in place. Whew.
Tight spot dimple tool is below. Basically the socket on the end is where the dimple ends up - you use the other side of a dimple die on top with the sheet metal sandwiched in between.
Once everything was dimpled it was time to attach the FL-901A and FL-901B nose skins. These are a very tight fit. The best way I found to do it was weight the flap as suggested by Van (used about 50# of sand in large freezer bags) and then use duct tape to hold the skin while I progressively tightened it. After two or three rounds of working it tighter I could get a cleco in one end. After that I just worked progressively along until the whole thing was clecoed in place.
The inboard ribs are inaccessible and have to be riveted with MK-319BS flush pulled rivets. The only ribs that can use AN426 rivets are the most outboard.
This is what the center section looks like where FL-901A and FL-901B inboard and outboard nose skins meet in the middle.
Riveting the FL-901C top skin to the nose skins and the FL-903 flap spar.
Working along the spar riveting the FL-901C top skin to the nose skins and FL-903 spar. The FL-905 ribs (vertical row of rivets) are not riveted until later.
Top skin is fully riveted and has also been riveted to the FL-905 ribs. I forgot to take a picture of the bottom skin being riveted in place. Basically the bottom skin is put in place, the whole thing is weighted to the table and you reach inside and flush rivet the bottom skin to the nose skins and spar. Tight quarters. Once that is done the AEX trailing edge wedge is put in place and everything is clecoed together.
Other side of the same assembly. At this point the rib holes are drilled oversize to accept the MK-319BS pulled rivets since there is no way to reach inside and flush rivet the bottom skin to the ribs.
Flap assembly after flipping upside down, drilling the rib rivet holes oversize, then riveting everything in place. Next step is to put rivets in the trailing edge, weight it all down, then back rivet the trailing edge into place.
I didn't take a picture during the back riveting. I'll try to remember to do that when I do the other flap. Finished right flap below.
Thankfully the trailing edge came out nice and straight.
Next - on to the left flap....
