This section was pretty cool. The fuse starts getting its shape. However, this must be the section where they really start slacking on the plans. There are a number of gotchas in this one, and they can really screw you up later on so pay attention!
You start by creating some nice thick pieces that will be used to attach seat belts too. Important stuff. Then the big ribs start going on the spars and bulkheads you put together last chapter.
Here is the next bulkhead aft and the ribs you attach to it.
Then the thing gets big real fast and you need to stand it up on end. I did make sure to measure this beast and make sure I can get it out to the garage. The end is in sight for my time building downstairs in peace, quiet and warmth during the winter.
Here's the whole beast with the two bottom skins on.
**GOTCHA SECTION**
When putting on the skins I realized something. For some of the outboard ribs it tells you to cleco them to the bottom skin and flute to match the curve. For others it just says "flute the flanges...". In these cases you need to make sure you put it against the bottom skin and flute to match, even though it doesn't say so. Here I'm pointing to the ones I'm talking about, the F-1018-L/R outboard ribs.
On 26-3 Step 7, it says to dimple the screw holes in the inboard side of the intercostals that correspond to the flush nutplates. There are 3 screw holes here, and each of them get a different type of nutplate. The top one is a K1000-08. This kind does not have the "divot" to accept a dimple. I of course dimpled all 3 and the top one doesn't sit right.
What you need to do here is dimple the #40 holes for that top nutplate, but don't dimple that top screw hole. The piece that goes over it is the F-1015C-L/R Mid Cabin Deck. Its hole that corresponds to the top screw hole of the intercostal is machine countersunk. There's also an inspection panel that slides in between those two pieces, so you don't want that countersunk or it'll be very hard to get in/out during annual.
Dimpled with the nutplate sitting wonky:
The piece that fits over this hole:
And the big gotcha's. I'll just shamelessly copy from Mike J's blog because I can't say it better than him:
In summary, here's what I believe really should happen during Section 26-5, somewhere between steps 1-6:
- For the F-1015A-L/R ribs, dimple all of the #40 holes in the web of the piece, excluding the forward-most row that tucks behind the F-1004D bulkhead. Leave the #30 holes alone (careful, they crisscross!)
- Dimple the flanges of the F-1015B-L/R Intercostals to match the dimples you made in the previous step.
- When completing Step 6 on 26-5, the dimple callouts for the #40 holes in the F-1018-L/R are correct; however you should *also* dimple the three aft-most #30 holes that can be seen on the right side of the photo above. Are those holes not there yet? You'll want to fetch the fuse side skins and cleco this rib into place, and match-drill those #30 holes, then deburr and dimple the rib. Trust me, way easier to do now than when everything's all riveted together. As a final clarification on the #30 holes, none should be dimpled EXCEPT for these three. Refer to callouts on Page 29-15 Figure 1.
One thing I saw online but luckily did it correctly myself was putting the slightly bent forward flange of the F-1018 ribs inboard of the F-1005C vertical support channels. Also applies to the F-1015A ribs whose forward flange goes on the inboard side. I saw cases were people accidentally riveted it in with that flange on the outboard side and it was a mess to clean up. Remember you need to create a flat face which the side skins will mount to.
Don't get scared when you see some extra parts that you primed laying there once riveting is complete. At the beginning you cut apart the spacers to make F-1015E and F-1015F spacers. You only use the "15E" ones in this chapter. The "15F" ones go on the otherside of the intercostals but not until chapter 29 (Fuse Side Skins).
Yet ANOTHER gotcha. This is the stuff that frustrates you. On 26-6, step 9 has you dimple 2 holes on the Fuse BulkHead Assembly (F-1034A) that are shared with Rear Seat Rib Assemblies. Problem is, those ribs have already been riveted on by step 6. Total lazyness in planmaking. To fix this, just do step 9 after step 5. I'm just going to countersink them for a dimple. They are unique from the others in that row because the rest get covered by a hinge:
So eventually you start dimpling and riveting this monster. There are 978 holes in those bottom skins. Woof!
The last two steps of this chapter are confusing too. Which bottom holes in the bulkheads do you countersink, and which do you dimple? The plans are clear on the big forward-most bulkhead (you couldn't dimple that monster after all). But the rear two it never mentions anything about countersinking, but says to not dimple holes that correspond to rib tabs.
After putting it together via plans you are forced into one solution - countersink the Rear Spar Bulkhead and Fuse Bulkhead holes that have a rib tab under them, and dimple everything else.
If I had to do it again, I could have dimpled everything (except the Aft Center Section Bulkhead). You would just need to dimple all the rib bottoms and the Rear Spar/Fuse Bulkhead bottom holes before riveting them on. Stated more simply, everything that gets riveted to the bottom skin gets dimpled unless its the Aft Center Section Bulkhead or touches the Aft Center Section Bulkhead.
When you dimple the bottom stiffeners, one end is squared off and one is cut back at an angle. The angled side goes on the Aft Center Section Bulkhead, so don't dimple that hole. Dimple the rest though. Don't forget to dimple the upper flanges of these stiffeners too (#30 holes). I forgot even though the plans were clear and had to buy a new squeezer to fix it. DUMB.
Finally you finish. Yeesh this chapter is kind of a doosey!
