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Need help with RV-10 empennage page 10-8 step 1

AndyWAUS

Member
Hi all,

I'm having a bit of trouble figuring out the relative position of a few parts. The parts in question are:

- F-1073-R and F-1073-L Side Skins
- F-1078 Forward Bottom Skin
- F-1079 Aft Bottom Skin
- F-1011 Bulkhead
- F-1047E-L and F-1047E-R Stiffeners

The plans first had me match-drill the stiffeners and have them clecoed to the side skins. Next, page 10-8, step 1 instructs to cleco the F-1011 Bulkhead and F-1079 Aft Bottom Skin to the F-1078 Forward Bottom Skin and the F-1073-R Right Side Skin. What I am unclear about is the position of the F-1047E-R stiffener in these parts. The plans seem to imply that the stiffener stays where it is, right next to the F-1073-R side skin. Then Figure 1 on the page depicts the F-1079 Aft Bottom Skin clecoed to the inner side of the the F-1078 Forward Bottom Skin and the F-1073-R Side Skin. Finally, the F-1011 Bulkhead is clecoed to the inner side of the F-1079 Aft Bottom Skin. So the sandwich would be (outer-to-inner): F-1073-R, F-1047E-R, F-1079, F-1011.

However, the way the flange is cut out for this particular hole in the F-1011 Bulkhead is the same as the holes for the other two stiffeners - F-1047C-R and F-1047D-R. In these two other places, the stiffeners directly contact the bulkhead flange, and the configuration of the flange makes sense. But where there is F-1079 skin in the middle, the flange of F-1011 is not sitting flush with the skin.

Perhaps, the intended configuration is different: F-1073-R, F-1079, F-1047E-R, F-1011. In that case, the two skins are contacting each other, the stiffener goes over both skins and sits flush with the flange of the F-1011 bulkhead. But in that case, the F-1047E-R stiffener isn't sitting flush with the skins! The place where the stiffener transitions from one skin (F-1073-R) to two skins (F-1073-R + F-1079) makes a little bit of gap and it doesn't look right.

I would expect the plans to be specific about this, but they aren't. Another thing that confuses me is the order of assembly. The plans have you do the right side first, without the F-1079/F-1011 in place. Presumably, this includes drilling the aftmost hole of the F-1047E-R stiffener. You drill it through JUST the F-1073-R skin. Then you cleco the F-1079/F-1011 and do the left side. So when drilling the aftmost hole of the left 1047E-L stiffener, you drill through the F-1073-L skin, the F-1079 skin, and the flange of the F-1011 bulkhead. So it's not exactly symmetrical.

Sorry about the long description, but I wanted to be as specific as possible. Thank you in advance for your help.
 
Skin to skin. Don't worry about the slight skin to stiffener gap at those last two holes. The stiffeners are flexible enough before riveting that it won't distort the skins and the structure will be plenty stiff after riveting (that aft bottom skin F-1079 is really stout, as you discover when you are final bending it to fit). After the skins, then the stiffeners, then the bulkhead tabs. The other confusion that some people have is the order of the three-skin joint where, inside to out, it should be F-1079, F-1078, and F-1073. Figures 3 and 5 show the stiffener in your question, though the buikhead is made transparent. In those, you can see that the stiffener is inside both skins.

As for the order of assembly, when you cleco the 1079 in place, it will be sandwiched by the 1073 and stiffener, so adding the other side will be symmetrical after all. Adding the 1079 won't affect the geometry that much, though you will want to be careful match drilling that hole so as not to enlarge the original hole in the skin. Best to cleco everything together and match drill that hole last with the rest of the structure holding everything in alignment. Also, when you get to the riveting stage, use levels to ensure that there is no twist in the structure, because even with match-drilled holes, there is enough tolerance that the clecoed structure can twist. Once riveted, it is pretty much locked in place.
 
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Perhaps, the intended configuration is different: F-1073-R, F-1079, F-1047E-R, F-1011. In that case, the two skins are contacting each other, the stiffener goes over both skins and sits flush with the flange of the F-1011 bulkhead. But in that case, the F-1047E-R stiffener isn't sitting flush with the skins! The place where the stiffener transitions from one skin (F-1073-R) to two skins (F-1073-R + F-1079) makes a little bit of gap and it doesn't look right.

If I remember correctly, the description you mention above is how it is intended. This was confusing to me too while building. I also remember, nothing would "fit right" until I got the right order. Here's the only pic I could find of my build of this piece. It's from the outside, but F-1073 skin, fits directly to F-1079 piece. Look real closely to figure 3 on same page. It shows the order your describing.
 

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Thanks so much Patrick and Randy! I re-clecoed the pieces and they look better now. Will make sure to keep it aligned and level while riveting - that is after I finish deburring and dimpling these two thousand holes. :)
 
I’m pretty sure that was the piece that, for me, really reinforced that if something doesn’t go together relatively easily, I likely did something wrong with the stack up.
 
Will make sure to keep it aligned and level while riveting - that is after I finish deburring and dimpling these two thousand holes. :)

Actually, you got me looking back through the pictures I took while building and I found my 'trick' to keeping it untwisted. Some people like to back-rivet but I couldn't do that on the bottom skin due to the A/C louvers so I just riveted conventionally. Once the bulkheads were riveted to the bottom, I clecoed the rest together and inverted it on a couple of leveled sawhorses. In the photo you can see the rolling stool for the bucker inside the shell. Once riveted up to the top longeron, the structure is pretty well 'locked in'.
 

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F-1011 and F-1012 Flange gap

I'm at the same stage in my build right now and found myself asking the same questions. I did mange to get the order of parts correct, but the gap between the flanges of the F-1011 and F-1079 skin seems excessive. I see this is similar for the F-1012 flanges as well.

I get that these can only be so tight given the flange is a flat side being fit into something rounded. When I compare this though to the flanges of the other bulkheads and frames that fit in the curve of the side skin, it looks like those sit much tighter. How tightly should these flanges fit? Won't this be problematic when riveting or does the fact that these will be dimpled help eliminate this gap?
 
F-1011 and F-1012 Flange gap

I'm seeing those gaps as well, and I haven't dimpled yet. Did dimpling resolve it and if not, please share how you remedied the gaps?

Thanks!
 
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