Center bulhead vertical bars

I've been poking around the various sites and so far only a Steve Hurlbut posting on the Matronics site sounds similar. It's the rivet size (AD 4-14) for the two vertical spacer bars at the ends of the aft bulkhead on the center section. They're even shorter, by the way, if you end up drilling at a slight angle (not too difficult with a hand drill when you're going trhough so much material. Note to self: Use the (**&#(*& drillpress, stupid!).

Anyway, I have very little shophead on these two rivets on each bar. Now I see by the planes that the two bolts here bolt into the nutplate on the wing spar. So Unless i'm missing something, there's no seirous structure purpose for these two rivets since the 13A bolts also serve to hold the vertical bars in place.

I also must be missing something. In looking at my favorite Web sites for RV construction. A lot of folks seem to have driven these rivets using a c-frame tool. I just used the flush head swivel set in a gun and a bucking bar. What am I missing here?

Anyway, I sent a message off to Van's asking them about these rivets, but haven't heard anything yet.

Oh, one rant. UPS should STOP using the term "2nd Day Air." It takes 5 flippin' days (waiting on an Avery shipment).

I just cleaned up the little tube spacers to be used in the centersection bulkhead, and then -- according to instructions -- made two 1 7/16" long spacers out of particleboard and drilled a 1/4" hole through it to allow a bolt to slip through.

The instructions then say to bolt the two sections together "around the spacers". Around the spacers?

Do they want all of the bolts in the two sections test fit here? I assume they want the bolts slipped THROUGH the spacers too (on the ISO, it looks like the bolt thru the aluminum spacer on the hole on the doubler just above the web stiffener, but there's a rivet there so I assume it's actually pointing to the hole just inboard of that location at the top.

And where do these wooden spacers go? ON the bottom somewhere? And why are there spacers at the top but not at the bottom?

I'm not exactly sure if I understand your questions, but I'll give it a shot.

Bob Collins said:

The instructions then say to bolt the two sections together "around the spacers". Around the spacers?

Click to expand...

I think they want you to bolt together the two parts of the center section with the wood blocks in the middle. Like this:

Do they want all of the bolts in the two sections test fit here? I assume they want the bolts slipped THROUGH the spacers too (on the ISO, it looks like the bolt thru the aluminum spacer on the hole on the doubler just above the web stiffener, but there's a rivet there so I assume it's actually pointing to the hole just inboard of that location at the top.

Click to expand...

I didn't put in every bolt. I think I used one big and one small on the top and bottom on each side. About half of the bolts. I can't remember if I messed with the tube spacers at this point.

Hope that helps.

Dave

Ok, I get it now. Geez, what an idiot I am. You know, why didn't they just say, the blocks are to simulate the main wing spar? They just said build two spacer blocks 1 7/16" thick. So I did. And 2" wide. I'm a flippin' idiot.

Don't flog yourself too much. I remember that part being confusing. I consulted the instruction addendum (rvproject.com) and it was more clear.

You don't need super big blocks. I was thinking I was going to use them at some point to support the fuselage, but it's easier to just use a saw horse. Not sure 2" is big enough, though.

I also just realized that I hadn't inserted the spar bolts in the picture above, but you get the idea.

Davepar said:

Don't flog yourself too much. I remember that part being confusing.

Click to expand...

I don't think you understand the depth of my stupidity, Dave. After reading those instructions, THIS is what I made.



Hahahahaahaha! Can you believe that? Now, granted, I had just finished making the little aluminum tube spacers so I was thinking small, but it just goes to show you...

There are days I think I'm too stupid to build an airplane. This is obviously one of them.

Center section spacer blocks revisited

Bob, Dave, or anyone else who wants to chime in?

I had the exact questions you had Bob after reading the instructions, looking at the plans, scratching my head, getting mad at Van's for the (lack of) instructions, and did a search and found this thread.

1. So, if Dave's spacer was bigger than it needed to be and Bob's were too small, can anyone give me a suggested size to make the 1 7/16" thick wood spacer blocks? Length and height? Is it one big spacer block across the entire center section or just 2 smaller blocks at each end of the center section?

2. I'm also not clear on the above thread: do the 1 7/16" tubing spacers go through the wood spacer blocks too or are they located in an entirely different location that where you'd be putting the wood spacer blocks?

If anyone can give me guidance here, I'd appreciate it. My brother has a thickness planer that he can use to give me a board exactly 1 7/16" thick and then bring it to me at Christmas, but I need to be able to tell him what size the spacer(s) needs to be.

Thanks in advance.

Steve,

1) length = 10-13 inches. Mine are 13 1/4 and may be a bit too long, but they're not really in the way. They're "hand-downs" from RV builders who are lucky to be flying now so I can't complain - they work great. Height = whatever the height of the wing spar.

PS. As a note, I know one builder who built his fuse w/o using any wood spacers... and wings fit like a glove..


2) No...


These spaces will go in 5-6 inches (or so) into the fuselage, and they can't go any deeper as there are bolts etc in the way, so definitely it's two pieces sticking out the sides.. not one long piece going full length.


You don't need to worry about the AL spacer now.. just make it same width as wing spar.. no need to put it in, especially if you're building a tri-gear RV (gear weldments are attached with those bolts as well). As a matter of fact, I'd wait with that hole in the aft section that they instruct you to enlarge to 1/4" until after fuselage is in one piece... only then would I drill it to full size, so it lines up properly with the forward part of center section.

HTH

Don't Bother

Guys,

The spacer blocks are totally pointless. the gap between bulkheads is established by the prepunched center section skin/bulkhead rivets along the lower flanges, and the prepunched side plates (704H, I think) running up the sides. The tube spacers just maintain the gap at top center when the seat floors are off. Make them to print length; adjust slightly if necessary to mate the floors to the flange mounted nutplates.

John Siebold

spacer blocks

This step allows you to verify the position of the closely machined bolt holes while the parts are on the bench. A better check would be to use the actual wing spar. I made 4 nylon blocks measuring 1 7/16" x 2" x 4". I drilled 2 holes 1/2" diameter in eack block for the bolts. Ho Depot and Loews don't stock cheapo 7/16" x 4" bolts so I borrowed some SHCS from my tool room at work for the fitup.
Steve

I agree with John that the spacers don't seem necessary, but I don't know anybody that skipped them. The center section is held in place by the side skins, the side doublers, and the bottoms skins (fwd and center). It doesn't seem possible to get the gap for the wing spar incorrect.

Dave

Thanks a lot for the help. They're not something I need to lose a lot of sleep about apparently, which is just as well!

Davepar said:

I agree with John that the spacers don't seem necessary, but I don't know anybody that skipped them. The center section is held in place by the side skins, the side doublers, and the bottoms skins (fwd and center). It doesn't seem possible to get the gap for the wing spar incorrect.

Dave

Click to expand...

I got a little nervous when I put the aluminum spacers in when I put the landing gear mounts on. I thought I had them EXACTLY as specified in the plans but I still had to file them a bit to get them to fit. Otherwise, I'd have gouged the spar when installing them. So, we'll see.

It took me forever to get the wood spacers to the perfect width. I tried all sorts of things and came up 3/16 short. I was sitting in the workshop one night contemplating this when I looked over at my case of beer and said "I wonder how thick that case is."

Dumped out the beer, cut up the case, sandwiched between some MBF and other material....perfect.

I'm confused. The beer in Minnesota is packaged in aluminum cases? We just get cardboard here.

Nope. Cardboard here too. It worked perfectly.

Gotcha. Van's should add that to the catalog as .187" sheet structural paper product, specify Bud, Miller, or Coors.

I made four wood blocks (two each side, one top and one bottom) by sawing 4 blocks at the required 1-7/16? length off a piece of wall stud pine (about 2.7? x 1.75? dressed). The blocks may seem small, however the cuts are made across the grain so they will not crush when you lightly clamp them up between the spars. Before I cut them in my drop saw I made sure it was cutting at 90 degrees (both ways). I then clamped a stop block at 1-7/16? from the blade so cutting the 4 blocks the same was simply a matter of pushing a length of wood up against the stop block and cutting. The beauty of this method is that you only waste 1-7/16? of wood each time you stuff-up. Just keep cutting/adjusting till you get 4 blocks you are happy with.

Finley Atherton
9A Fuse
Australia

Obsessing on thickness

I built four blocks as described above. I machined some old maple I had lying around but took about .006 more off than 1 7/16th. I have scratching my head about just how exact this needs to be. I would hate to try to insert my wing spars and find out they won't fit. Not having seen that step before, I don;t really know how tight the fit/tolerance is. On the other hand, if they are not really crucial, then I am definitely obessing. Can anyone who had been down that path guide me?

Regards,

Michael Wynn
RV 8 (Pre-punch) Fuselage
San Ramon, CA

Bob Collins Join Date: Jan 2005
Location: St. Paul
Posts: 976


Center bulhead vertical bars

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I've been poking around the various sites and so far only a Steve Hurlbut posting on the Matronics site sounds similar. It's the rivet size (AD 4-14) for the two vertical spacer bars at the ends of the aft bulkhead on the center section. They're even shorter, by the way, if you end up drilling at a slight angle (not too difficult with a hand drill when you're going trhough so much material. Note to self: Use the (**&#(*& drillpress, stupid!).

Anyway, I have very little shophead on these two rivets on each bar. Now I see by the planes that the two bolts here bolt into the nutplate on the wing spar. So Unless i'm missing something, there's no seirous structure purpose for these two rivets since the 13A bolts also serve to hold the vertical bars in place.

Bob,

I had the same problem as you. Drilled w/hand drill through the vertical spacer bars. Crooked of course. We gain experiance as we go along. Had to redrill slightly displaced from original hole & drilled new holes in the web. with the drill press. Also, the AD4-14 rivets were too short for me also. Van's had some longer AD4-18 I think, I ordered and cut them to about AD4-15. Worked fine.

Carl Nank
RV7-A Installing brakes & rudder pedals.