SECTION 25: MID FUSE BULKHEADS
Build Instruction Updates
- 01/07/21 25_10.pdf
Check for more recent updates here
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Later in the build process (Section 28, page 28-12, Figure 2) you will need to have 7x double-flush rivets on each side of the forward main spar. That requires you to machine countersink the top/inside of the bottom flange for those 14 holes. The outermost holes on each side are very hard to properly countersink after you have attached the F-01004C center section bulkheads.
So, while you are on this step, I recommend machine countersinking on the top side of the bottom flange (you'll CSK all of the holes in the bottom flange later as part of the normal instructions but they'll be deeper than normal due to the thickness of the bottom skin). I countersunk the top holes approximately the same size as I would do for a normal countersunk rivet factory head. See the image on this page for what it will look like when you are done with Section 28.
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F-1004C-L and F1004C-R
Conduit Summary
The holes in the bulkheads are only big enough to have cables run directly through them using snap bushings (vs. in a conduit). Also, there are only two holes on each side and depending on your needs, you need more.
You do need conduits for sure but only to tunnel underneath the baggage compartment. You can go back to snap bushings forward of the baggage compartment if you like. Some people though like to just run at least some of the conduits all the way from the tailcone to the front. Now that is where the diameter needs to increase from .75 to at least .77 for Van's Nylon conduits. It is a pain to enlarge those holes afterwards since they are tucked in underneath horizontally-running structures. Adding more holes can be done later but is also a bit easer if the bulkheads aren't in the plane yet.
If you run conduits all the way from the back to the front, it will be easy to route the static pitot tube, the pitch and yaw servo cabling, the pitch trim servo cable, the battery cables etc. Also makes cabling for later add-ons easy.
Hints
Step 8 details the assembly of the bulkheads to the center section prior to deburring and priming these parts. Now is a very good time to consider whether you will need additional pass-through holes in the bulkheads for items like conduit, pitot, static, and AoA sensor tubing, air conditioning lines, and other electrical circuits. Many builders find that the two holes referenced here and on #PAGE 25-4 are insufficient for all of the required lines and circuits for an RV-10, especially if it is going to have a full glass panel and backup/redundant electrical systems.
Do yourself a favor and read forward in the plans to Sections 29 and OP-37 (even if you do not use the Van's provided wiring harness, OP-37 is very useful in understanding the options for routing electrical circuits).
Later in the build, especially after the side skins are installed, it is quite difficult and awkward to cut new holes for conduit or other pass-throughs. Installing caterpillar or snap bushings can be awkward later, too. You will save considerable time later by thinking ahead at this point.
See also Section 26 where the F-1017 under-seat ribs can be much more easily modified before installation to allow conduit and antenna installation, which might not be done until Section 35 or later.
ENSURE that any additional holes you cut in the bulkheads are properly spaced and, if needed, reinforced per the guidelines in AC43.13.
See also this FB thread on the subject.
See also this FB thread on the subject.
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- Step 6
Step 6 requires you to 'Rivet the Mid Seat Rail Support Subassemblies, F-1004C-L and -R Center Section Bulkheads and F-1004N Stiffener Angles to the F-1004A Center Section Bulkhead per the callouts in Figure 2.' Figure 2 in the plans (Rev 1 Date 1/7/21) omits the quantity and rivets to be used. The older plans (Rev 0 Date 7/24/14) shows the rivets and places. - Step 7
Don't insert the snap bushings instead widen the two holes to a bit larger than .75 inches (.77) so they can pass through Van's conduit later. Also drill a third / forth hole with same diameter underneath the two holes for a more conduits if desired.
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- Step 7: Check that F-1004J has the correct length and is not pushing the spar caps out of their proper position where the wing attach bolt holes no longer line up through all layers. See also this FB Post 2/2024.
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- Step 4
Don't insert the snap bushings instead widen the two holes to a bit larger than .75 inches (.77) so they can pass through Van's conduit later. Also drill a third and forth hole with same diameter underneath the two holes for more conduits.
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- Enlarge the two holes at the lower corners of F-1005A to a bit larger than .75 inches (.77) so they can pass through Van's conduit later
- Step 3: In section 29, page 29-14, step 9, you will be instructed to machine countersink the outboard #40 holes on the flanges of the F-1005C-L and F-1005C-R Bulkhead Side Channels. If your kit is newer and has final-sized holes, you will not need to final-drill these holes between now and then. Consider countersinking these #40 holes now as it is somewhat easier than doing it after it has been riveted to the fuselage. They should be flush on the outside and should accommodate an AN3 rivet with a 0.032 skin. Section 29-18 shows these five countersunk locations (on the inside of the F-1005C-L and -R parts) to be riveted double flush, just as the seven locations (per side) were done as shown above for Section 25-3.
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I am still unable to interpret Figure 1 -- is the part shown concave or convex? I'm not sure. But F-1034D-L and F-1034D-R are definitely different. I thought I had it right, I riveted on this page, and I didn't notice I had them backwards until the end of Section 26. I found that my F-1034C-L and F-1034C-R were angled outboard and they should be more or less perpendicular to F-1034A. I don't see a downside to leaving these cleco'd and riveting in section 26.
- Enlarge the two holes at the lower corners of F-1034A to a bit larger than .75 inches (.77) so they can pass through Van's conduit later