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-   -   F-303 Center Section Notes (https://vansairforce.net/community/showthread.php?t=50711)

Ironflight 11-19-2009 11:18 AM

F-303 Center Section Notes
 
If the RV has a structural heart, I believe that it is the Center Section bulkhead. In the RV-8, it is the 804, in the RV-3, the 303. This bulkhead ties the wings and fuselage together, transmitting the load of the engine, fuselage, and tail into the wing spar and creating a single flying entity. As a previous "quickbuilder", I never had to address the critical nature of creating the structural heart, but on the -3 project, we had to start with a few flat and flanged bits and pieces to produce a three-dimensional sculpture that fits the existing spar stubs of our quick build wings. Since a couple of these parts are match-drilled to the wing spars, the thought of ruining them makes the project a bit more daunting because of its criticality.

While Louise has been building up other bulkheads for the fuselage, I squirreled away the pieces of the F-303 and headed to my own bench to build it up. I was pleasantly surprised that the side pieces were pre-punched to fit the bottom center section pieces that had been matched to our QB wings - clecoing it all together didn't take long, and careful measurements at the "top" of the "U" showed that it was right on. This made the overall assembly go a lot quicker, as much of the potential for misalignment was taken out of the equation. It didn't take long to rivet the forward and aft bulkhead components into sub-assemblies. In order to join the front and back, I needed a spar simulator exactly 1.0625" thick (that's an inch and a sixteenth). That's the measurement called out in the plans, and I also measured the spars to confirm it - I could think of nothing worse than getting the fuselage all fab'ed up and then the spars not fitting in to the box.....

I wandered around Lowes for about an hour trying to find an easy way to build up a wooden blank just that thickness, and eventually bought a nice piece of ½" finish plywood there, and a piece of 1/16th thick plywood at a local Hobby shop. I sandwiched the model plywood in between two pieces of half inch and let the glue dry with considerable clamping force to keep the dimensions tight. Presto - a perfect thickness! I cut the laminated piece in to two 6"x18" pieces, plus two little blocks to set the spacing at the top of the bulkhead "U". I used the tooling holes at the top of the bulkhead, plus a couple of AN3 bolts, to establish perfect alignment between the front and back pieces of the spar. I then slid the false spars in between the bottom portion and marked the locations of the wing spar bolts. Pulling them back out, I drilled the holes slightly oversized, so that the bolts I used to join the two halves during assembly would not actually be bearing in the wood. Much to my delight, temporary bolts went in perfectly from front to back, proving both accurate drilling by Van's (Phlogiston I bet) and good assembly alignment. From there, it was not hard to match drill the side and bottom pieces to create the center section "box". I elected to install the -4 rivets that hold the sides and bottom on now, and will pre-drill for all the skin rivets before we start skinning the fuselage. If I discover later that I have a hole that needs to be open, I can always drill a rivet out.

The proof of the pudding came when I took the false spars out and slid the center section on to the real wing spars - and everything fit, with no play! Now THAT'S a great feeling!

I decided to go ahead and pre-drill the F-303G pieces (the channels that closeout out the forward and aft sections in the cockpit) now, rather than wait to drill them once the fuselage is completed - having done it later in the construction of the -8, I remembered how awkward it was getting the drill to certain spots. Having the pieces clecoed in place will also make the assembly that much more rigid when building the fuselage around it. At least, that's my theory for now!

Here's the "finished" product, ready to go into the fuselage jig along with all the other bulkheads Louise is building. (Note the orange bolt heads - any time I use "hardware store" bolts in the shop, I give them a spritz of primer and fluorescent orange paint, just to make sure they don't hang around during final assembly. I don't allow "orange" in any finished part of my airplanes!)



Additional pictures at: http://picasaweb.google.com/Ironflig...CenterSection#

James R WilliamsA&P/pilot 11-19-2009 10:32 PM

Thanks for your notes! I'am not to far behind you so I just wanted to let you know your post are very helpful to me and just had to say thanks and keep posting.Jim Williams

LifeofReiley 11-19-2009 10:45 PM

I don't
 
know if you're at the firewall/longeron setup yet, but beware the steel supports for the engine Van's has been sending out are not 87 degrees per the plans and cause a big problem. They seem to be fabricated at 90.

pierre smith 11-20-2009 05:49 AM

I just visited my buddy, Brooker...
 
...in Sandersville, Ga. yesterday. He's building his 4th RV and is in the middle of flap construction. You won't believe that the RV-3 plans show 3 different length dimensions!!! It really takes some head scratching.

All of you -7/-9/-10 builders can't really appreciate all of the pre-punched stuff until you plans-build, like the -3.

Best,

Ironflight 11-20-2009 10:27 AM

When it comes to the RV-3 drawings and instructions, it is "MIS-trust, and verify EVERYTHING!" ;)

Paul

Ironflight 12-15-2009 11:11 AM

Quote:

Originally Posted by LifeofReiley (Post 378792)
know if you're at the firewall/longeron setup yet, but beware the steel supports for the engine Van's has been sending out are not 87 degrees per the plans and cause a big problem. They seem to be fabricated at 90.

I think they must have gotten the bad ones out of the system Darell - mine seemed to fit far better than I expected from all the things I've read. Since we have a second-hand kit, it's hard to know know where our parts are in the chronology though, so I still consider everything (on the -3) suspect until it proves itself to be correct.

Paul

WingsOnWheels 12-15-2009 01:19 PM

Quote:

Originally Posted by pierre smith (Post 378843)
...in Sandersville, Ga. yesterday. He's building his 4th RV and is in the middle of flap construction. You won't believe that the RV-3 plans show 3 different length dimensions!!! It really takes some head scratching.

All of you -7/-9/-10 builders can't really appreciate all of the pre-punched stuff until you plans-build, like the -3.

Best,

It's not much different with my old -6 kit. It can be quite confusing when on the same plans page there are two different part numbers for the same bit...

The builders manual is pretty funny also. They might as well just put a single line "build per plans" for all the detail they have for certain areas. Real men don't read instructions anyways...right?

JonJay 12-15-2009 02:05 PM

Missing the 303 parts!!
 
Evidently, at times there are "paper work" problems with the 3's associated with the QB wings and fuselage pick lists. It makes it difficult to catch until you are ready to start construction on the center section as the parts do not show up on any packing list, so you wont catch it in an inventory.
There is a matched drilled center section set that fits the kit I sold floating around Phlogiston, Van's, who knows where. They are being very helpful, but it is looking like the raw parts will have to be substituted and the holes manually drilled to match. Not the end of the world, but makes for a lot more work.
If you have a 3 kit with QB wings, double check to make sure you have the
F303 parts in your kit! Dont trust the paper work as being complete.

Ironflight 12-15-2009 03:26 PM

JonJay,

OK, you are the THIRD person I know of that has been missing some center section parts – me, Andy Hill, and now you – and it seems to be a consistent problem. I talked to Joe Blank a few weeks ago, and ended up having to buy the replacements, but I had little to complain about, as I bought a second hand kit, and there is no way I’d hold Van’s responsible for stuff that isn’t there. But there was enough of a mystery that I suspected there might be an inventory control problem. Maybe if enough of us figure it out, we can get them to make that part of the kit inventory a little more robust! All I got was the lower portion of the bulkhead (I think thats the C and D), and I was missing everything else. When I got the replacements (to the tune of about $170), they were all bundled together, almost like a subkit.....

Again, I don't hold Van's responsible for a second-hand kit, but I am fascinated that others are missing the same bits.

mannanj 12-15-2009 06:01 PM

Build
 
Quote:

Originally Posted by pierre smith (Post 378843)
...i

All of you -7/-9/-10 builders can't really appreciate all of the pre-punched stuff until you plans-build, like the -3.

Best,

Or a Pitts Special. Circa 1976, there were about 10 sheets of 11X17 prints with a bill of materials list on the bottom right of each sheet.:eek:

Somehow managed to forage a typewritten sheet of the "sequence of build" from an old time builder.:D

Sorry for the thread drift.


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