Tail Cone - Troubles with the fit

Last night I was able to rivet the two aft most bulkheads to the bottom tail cone skin.  This wasn't an easy task, but I started with the inner most rivets on the aft most bulkhead, then started mounting the tail spring and working around it.   Its difficult riveting under the spring because you are working at some acute angles in there with bucking bars while trying to keep those rivets straight, but it went OK.

I ran into troubles when I went to assemble everything, it seems the longer (lower) J channels interfered with the tail spring and caused the aft most bulkhead to skew in a weird way.   I am really hoping it was the J channel because not sure what else it could have been.   So I took it apart (again) and trimmed the J Channel, and put it back together.  This time I put the tail cone on without the side skins, and will add them later.  I think this is the best way to get a smooth fit, use an extra saw horse and don't put the side skins on until you get the J channels in the proper locations for all Bulkheads.   You will understand what I am talking about when you get there.

Anyway, looking at the set up now, there doesn't seem to be any twist in the last bulkhead.  It fits pretty nicely at this point and I hope adding the skin wont change this fit at all.   So tonight we will find out.

Tail cone final assembly

This is where it all comes together and it either fits or it doesn't.   I am worried about the tail spring fitting in assembly, but for now I just need to keep pushing forward.  Last night I started the first few rivets on the tail cone.  On other sites I have seen some trial and error and learning from them, I think that it is best to start by riveting 710 and 711 to the lower skin first, then fit into assembly.  When riveting these bulkheads to the lower skin, I think starting with the inner most rivets on 711 is the way to go, then you can fit the spring over those rivets and all other rivets are reachable with the spring in place.  Well, that is my theory, we will see how it goes.

Also, here you can see the shim I had to make to get the rear of the tail spring to fit with 711.  Quite the work of art when you look at it. 

Tailcone ready for final assembly

Today I was able to finish priming the entire structure of the tail cone.  Next step is riveting it all together which is always the best part.   I am a little nervous about the fit of the tail spring rod into the receiver when all is said and done, but I am sure with enough grease and pressure I can get it to fit in fine after assembly.  The risk is the receiver gets riveted into the tail cone never to come out again long before you get a chance to test the final fit.  I am pretty sure I will be OK though.  For now I have primed and painted both the rod and receiver, so I am sure it will give a long useful life even though I didn't powder coat it.

Tail Cone Parts dimpling and deburring

No Pics this time because nothing much has changed except I took the whole tail cone apart and deburred, then dimpleled the skins.  This took forever, but is now complete.   I have the skins all preped and ready for priming.  Plan is to prime tomorrow then start working on completing the tail cone.

I also, decided to prime the steel tail spring assebly and then paint it.  First I was going to Powdercoat it, but I am frustrated with the quality of material on the tail spring.  I had to really work the rod to be able to get it into the receiver and it still doesn't go in smooth, plus the receiver is not welded straight...   I have made shims to account for this, but am thinking that I may have to work on these parts again, do don't want to go through the cost of powdercoating them.   Its about 100 bucks, and I could spend that money on a new tail wheel caster, which would be a good trade off..  We'll see.

Pitch Autopilot Servo Mount - Saved by Dynon

I thought it would be a good time ( with F-706 accessible in the aft fuse ) to build out the servo mount for the Autopilot.  So I ran over to Dynon at lunch and picked up the kit for their pitch servo.   Pretty simple kit, easy to install right  ?   Well it should be but I made a bonehead move due to my haste (and the heat this week in Seattle)..  If you lose focus for one second, it can have bad effects; sometimes devastating.   Luckily here, only the autopilot bracket was ruined..  Rather than F706 or worse yet, the bottom skin of the tail cone ! !   (Pics to come)

Anyway, for some reason I didn't have the clecos in all the way and as I clamped the bracket down, it pushed the bottom skin away from 706 when I drilled.   Needless to say, the holes didn't line up on the test fit.. and I put things away for the  night to cool down..

Silver Lining..   I emailed Dynon today and told them I couldn't be the only one to do a bonehead move like this...    They responded:

"Sorry Sir, but you are the only one to do this boneheaded move. :)  Come on in and I will get you another bracket or I can mail it to you."

So on my way back to Dynon tomorrow for the replacement and I should have a servo mount in by the weekend.

Thanks Dynon!   Now get back to work on that Arinc 429 module...   ;-)

J Stiffeners and Drilled Rear Fuse

Today it was about 100 degrees in Seattle and no A/C in the shop.  Wow, lost about 10 pounds in water weight..  But was able to make huge progress on the rear fuselage.   I finished with the J stiffeners and drilled them all along with the entire rear fuse.  Excited about how it turned out but was much more work than I thought.  

Also before I drilled, I made sure via many ways that there was no twist in the Fuse.   A few pics of plumb bobs showing how straight it is.  ;-) 

The rear tail cone skin was a bugger, but I went one cleco at a time and used drill bits and punches to pull the skin together along with a clamp to try and make the tail cone skin the right shape.  Once I got a cleco in, then the next, it went pretty well and I don't think I enlarged any holes to much.   Many builders here end up with some lopsided holes and then decide to go with the larger rivets.   I hope not to have to do that but we will see when it all comes back apart.

Tail Spring and J Stiffeners

Today was a big day in the shop, but not as much to show for it as I had hoped.

First I started on the tail cone skin, opening up the hole in the bottom for socket access later when installing the tail wheel spring.  I also used the template from the plans and traced and cut out the slot where the tail spring exits the tail cone.  This took quite a bit of time filing and sanding, test fitting, to get it the way I wanted it.  Turned out pretty good.

Then onto the tail spring assembly and fitting it between bulkheads 710 and 711.  You start by using the bottom holes in 710 that were left open from when the bars were riveted on as a guide and center the end of the tail spring assembly on the bottom of the bulkhead.  I drilled it with the #30 first, then opened it up to 1/4 for the AN4 bolts.  Turned out well, until I tried to put on 711.  Turns out that my tail spring assembly was welded crooked.

VANS AIRCRAFT NEEDS TO HIRE BETTER WELDERS..

The directions say to shim any gaps, but it is pretty hard to shim something as twisted as this was.   I did my best and think it will turn out just fine, but it so easily could have been welded correct to begin with..  Oh well.  Once the shim was fitted, I drilled for the retaining rivets that hold the rear of the spring until the vert stabilizer is mounted permanently securing the rear of the spring.

Next I started the J-Channels and ended up cutting each of them 2 or 3 times to get the fit right.  This was quite challenging for me and very time consuming.  Actually it took me all day because you have to put the entire aft body together then take it apart, then put it together again a few times before everything is over.  cutting the angles on the stiffeners was challenging to say the least, especially since you are working with 8 foot lengths of aluminum..   ( I am not looking forward to the 15 foot longerons.  )

Once all said and done, The aft body came together well, and I was able to verify it was plumb by using the plumb bobs hung from the tooling holes..

Bulkheads Complete

Over the weekend I put a lot of work into the bulkheads, finishing up F705 and the rest of them to the point where I can move forward.   I didn't prime everything yet as I am planning on drilling the tail cone first, then deburring/dimpling, and finally fully priming the bulkheads.  I did prime all areas of metal where the rear bulkhead halves came together.  With the rear bulkheads in particular they must be riveted together before you can start drilling the tail cone skins, making it is necessary to prime them first.

I also worked on the seatbelt mounts that need to be trimmed back to make room for the seat ribs.  I trimmed these with a cutoff wheel in a die grinder, then buffed with the scotchbrite wheel.  Turned out pretty nice, and I think I can bolt them on now and leave them.

Next steps are the Longerons and/or drilling the rear fuse and its J-stringers..  Things get pretty big from here on out.  ;-)

F-710 and F-711

Moving right along with the bulkheads. I pushed through a majority of the work on 710 and 711..  These bulkheads are basically two pieces each riveted together back to back.  Together each one becomes pretty strong which is important in this area since they support the tailwheel assembly, empennage, and the rear of the plane.  I still have to cut out the web on 710 but other than that and the general prep and priming I am about done.  Stuck them into the cone for looks and am excited how it turned out.

I also got the parts I was waiting for to complete 705 so I should be able to get that done over this weekend.  Also, I noticed on 706 that since I am going to be adding an autopilot, I should have left a few rivets open on the lengthwise rib which I will now have to drill out.  The servo mount assembly leveraged existing holes from where the angle is now riveted on..  Oh well,  I will wait until just before I rivet the bulkhead into the assembly.

F-707, 708, 709 etc..

So I am getting a bit ahead of myself with the bulkheads as I am still waiting on a couple F705 parts.   But the F-706 is done and I fluted and clecoed F-707 and 08.   Since I had all the skins in my way laying on the shop floor, I decided to do a quick cleco together of the tail cone to get an idea of what I was up against.   This will all have to come apart to prime the bulkheads, but for now it looks good.  Sort of like the back end of a fuselage in my garage ! !   ;-)

This week I am going to go back and tackle some of the things that I need to catch up on.  Finish F-705, continue to work on the other bulkheads and get them primed.  It will be lots of odds and ends for the next week or so, before I get to start drilling and working on this big structure.

One thing I noticed about the rear bulkheads is you need to widen the slots for the longerons, also, drill out pitot static mounting holes on the top of F-708, and drill pitot static pass throughs on 07 and 08.  Also, don't forget the 5/8 inch holes for the rudder cables and additional for electrical.  Still lots of attention to the seemingly easy bulkheads.

F-706

While I am waiting for a few more F-705 parts its time to start F-706.  The bulkheads get simpler and use thinner material as you go further back into the Fuse..  That is until you get to the tail wheel section..

Here are all the parts (I think) for F-706 that I have rounded up.  Some of this metal is pretty thin.. Will take some work to get it to lay flat and look good.

Couple days later, I went ahead and moved forward without the camera.  Basically I fabricated and match drilled and primed all the parts.   There are some angles that needed to be created, and of course you need to make the 5/8 inch unibit holes fro the electrical and the rudder cables a a few areas that get dimpled for flush rivets..   So far I am happy with how this turned out.   Next steps involve riveting, but note that there is a specific order, and you don't set all the rivets now, some go in at a later date.

NOTE:  If you are building and at this point, consider if you are going to have an autopilot before you rivet the angle to the lengthwise rib at the base of F-706.  There are some rivet holes you can leave open at this point for the servo mount that will help you avoid drilling them out later.  ;-)