SonexBuilders.net

Hi,
I'm a bit confused as to assembling the rear tunnel Z. Mainly the top of it, and getting the seat in. Per SNX-F11 the 3 outer rivets will be solid rivets, correct? Also I will need to countersink them from the inside of the tunnel? If that's the case, how am I going to pound them in? I just don't see how that's going to work. There is nothing to hold a bucking bar against the bottom for leverage. Will I have to suspend the fuse on a bar of some sort and use that as the weight?

Also, I'm trying to get the seat in. I see that the front line of rivets holding down the piano hinge are just standard rivets, not countersunk, is this also correct?

Lastly, my understanding is that the rear Z is not riveted at this point, that's apparently so incase I need to make the ever so slightest adjustment when mounting the wings, is this also correct? And is that rear top line of rivets on the rear Z countersunk? I didn't see that as being the case. So, other that the 6 rivets, that I have no idea how to buck in place, that line of rivets in between are just pulled from the top at some point? Being when?

I don't see how I can mount the seat without any support from the rear Z, looks lie it may bow the front if I sit in it to mount the tank before everything is buttoned up.

Scratch building, if it makes any difference in the process.
Thanks
Alex-

Alex,
There are a bunch of folks who are further along than I, so they may be able to answer your questions more completely and better. But, I am just a little behind you.

So on the 3 flush solid rivets per side, I see two ways to do this. The flush part is inside the tunnel. The plans seem to suggest smashing the rivet into the countersink, which will work. On the C140 I was restoring there are a bunch of double flush rivets in the doorpost where the strut attaches. One side started out as flush and the other side filled up the other counterbore. After I had to shave, sand, or file it all the way flush. What I will probably do is back rivet those. Flush head goes underneath, held up by a heavy bucking bar, and the rivet gun forms the shop head directly. I have a special back rivet set though that is not required. It is a two man job.

As for the seat, I was able to sit in my seat pan with the aft tunnel Z clecoed in place to support some of the weight. Most of your weight appears to be actually supported by the lower aft cabin (I forget the name of the crossbeam).

The aft tunnel Z is riveted on final fuselage box assembly, after wing rigging is complete. The 6 flush rivets are intended to have the rounded head on the top and the shop head squished into the countersink. I asked Sonex if there were alternatives to this and this is their response:

"We have no substitute for them. They are used there to get the required flush fit in the spar tunnel, to prevent interference with the spars, and we want the round head in the cockpit to prevent a sharp rivet tail from cutting the occupants."

I used the rivets called out in the plans. My wife held the bucking bar on the dome head of each rivet and I pounded the tail into the countersink from underneath (before I riveted the bottom fuselage skin) using the bolt method Sonex recommends for the spars. After procrastinating this task for months, it was done in 10 minutes.

Sonex1542 wrote:Also, I'm trying to get the seat in. I see that the front line of rivets holding down the piano hinge are just standard rivets, not countersunk, is this also correct?

Hi Alex
Yes just standard rivets as per plans. There are no interference issues with the spars and those seat rivets

Sonex1542 wrote:Lastly, my understanding is that the rear Z is not riveted at this point, that's apparently so incase I need to make the ever so slightest adjustment when mounting the wings, is this also correct?

It's not for slight adjustment. Prior to rigging the wings will need to have the rear tunnel zee and associated parts completed. Do not rivet these parts until rigging is completed. You need to be able to remove all parts associated with the rear tunnel zee, for the initial step in final drilling of the main spar attach blocks to the fuselage attach angles.

Sonex1542 wrote:I don't see how I can mount the seat without any support from the rear Z, looks lie it may bow the front if I sit in it to mount the tank before everything is buttoned up.

Scratch building, if it makes any difference in the process.

Try to resist the temptation to sit in it. Scratch or kit, it makes no difference

Steve
Sonex 892

Hi Alex,

Just to chuck in another twist, I raised the hinge fixed the tunnel Z using a .040" spacer. This is because the front row of seat hinge rivet tails drag on the spar tunnel.

Also I used countersunk solid rivets at the ends of the spar tunnel, inserted from below. Just rounded off the shop end after they were set. From memory the seat pan covers 2 of the three rivet tails.. cuts from tiny rivet tails would be the least of my worries..

The seat pan will bend when you sit in it. I was vary careful with measurements when making it but still had a slight bow with no weight on it.

The danger of sitting in the seat is that you will spend more time dreaming and making airplane noises than building..

Cheers
Tony

I waited to read the replies to make sure that front row of rivets is what I saw in the plans. But dropping the seat in NOW! I'll keep in mind that they can drag on the wing member, but honestly, will deal with it if it happens on rigging.

Back to the 3 rivets on each side... Am I right in thinking (I did rivet the bottom in) they are gonna be a bitch to get a bucking bar on them? And since Sonex wants them countersunk from the inside, I'll have to deal with them like the rest of the countersunk pulled rivets... Dimple the sheet, and countersink the top aluminum angle?

I imagine I'll have to use some type of metal stand through that tunnel to put enough weight on the bar as I smash for the top!

Thanks all!

No. Riveting those 6 rivets in flush took my friend Tony and I like 15 minutes. (Ok. Mostly Tony. I watched).

It is not as difficult as you think.

Robbie Culver
Sonex 1517
Chicagoland
Tails and Wings complete - finishing fuselage.
N1517S reserved

Also those rivets are a size smaller than the wing spar rivets, should be much easier to drive.

I am having difficulty figuring out how to rivet the 3 end rivets on top of the spar tunnel as well. The bottom skin is already installed so I cannot use a bolt or anything else on the shop head from the bottom. I did already countersink the angle, and notice that a CCP-42 looks like it will have proper grip length. A CCP-42 has a grip length of .062 - .125. The particular part is a .125 angle with a .032 skin for a total of .157. If the countersink is at least .032, then the grip length will be correct. This is the same technique as described in the plans to use a countersink in the wing attach angle doublers on the aft spar tunnel web to allow for CCC-44s to be used in lieu of CCC-46s. Does anyone see a problem with using CCP-42s on the 3 end rivets on top of the spar tunnel?