RV-3 Baggage Compartment Ribs

Ironflight · #1 01-08-2010, 09:16 AM

After getting the aft fuselage skins drilled and clecoed in place, I was looking for things to keep me busy so we didn?t have to look at (and deal with) some of the tougher areas forward of that point. My eyes settled on the baggage compartment ribs, which I had decided to hold off on until the skins were in place because I had figured out that they were simply too short as delivered in the kit. Well, after the skin was installed, they were still too short (by about 5/8?, not having grown any (dang stable aluminum!) while sitting in the corner. But at least I had come to be at peace about the problem, and cutting off the aft flanges to make a new set didn?t sound all that bad anymore, so I decided to tackle the job, and get these things mounted.

Of course, the first thing I did was consult the drawings, only to discover that the design has the ribs off-set from center to accommodate the big honkin? battery box. One rib is four inches from centerline, the other only three. Well, heck, I seriously doubt that I am going to put a big honkin? battery in the plane, so why create a nightmarishly unsymmetrical structure? Sure, Louise and I will be the only ones that know what lies under the baggage floor, and I doubt anyone will crawl under the belly with a ruler to see where the two rivet lines lay, but still! A quick note to Van?s confirmed that I was at liberty to center the ribs if I wished (but it was pointed out with a wink that it would still not be symmetrical, as both ribs have their flanges pointing the same direction to make the trapezoidal parts identical?so would I put the rivet lines or the webs on center?), so I measured off an even 3.5 inches to either side of center, and drilled two lines of holes. Marking centerlines on the rib flanges, I held it up from below as Louise drilled a couple of keeper clecos right through the lines, and I finished them up from there.

Next was the flange transplant. I had plenty of material from the trim bundle, and it was nothing to make a couple of flange extensions, cut off the existing flanges, and mate it all up together under the fuselage. I marked a quick rivet pattern (overkill for sure, but I hadn?t driven a rivet in weeks ? it felt good!), and before I knew it they were done.

A few pictures:

Factory rib and new flange

Flange cut off of "too-short" rib

New flange clecoed in place

Fits like a glove!

So?.two things for future RV-3 builders come out of today?s exercise:

1) You can center the ribs if you want to make things symmetrical.
2) Expect to need to lengthen the ribs (I heard from two other guys that their ribs were too short as well).

For those not building -3's - enjoy the pre-punched, "fits like a glove right out of the box", parts!

Paul

F1Boss · #2 01-08-2010, 11:05 AM

Well, I didn't notice that these ribs are supposed to be different L/R, so we put 'em in like you decided to, right from the start! We did not have the length issue either -- maybe I'd better check that too?

We did have an issue with the lower aft longeron stacking up on the 305 bulkhead, so we used a different method there (tri-angular attach doubler) to reduce the big ol' bump factor.

Geez, these -3 kits are way more work than anything else I've built -- even the Exxon Tiger was easier! Of course, there were no plans for that one, so everything went together with a TLAR attitude....and it worked!

This ship is getting a bit of that treatment too.

Carry on!
Mark

Ironflight · #3 01-08-2010, 12:13 PM

Quote:

Originally Posted by F1Boss

We did have an issue with the lower aft longeron stacking up on the 305 bulkhead, so we used a different method there (tri-angular attach doubler) to reduce the big ol' bump factor.

Mark, you just solved the problem I have been puzzling over for a week with that little statement - thanks! (that silly bump has been driving me crazy, and now you've given me "the vision"....)

This is building the way it was intended to be - right?

Paul

F1Boss · #4 01-09-2010, 07:24 AM

Yep, but I will add this sort of process is not for 1st timers, unless they have adult supervision.

Our doubler is about 6-7" front to back, and about 3" high. We tied the aft longeron into the center longeron....

This particular part took me more than a week to come up with. Once we got the the skin stage, something had to give. Necessity IS the mother of invention!

I'm wondering about using a more RV4 style flap/fuselage intersection too. I might need to eyball a -3 to see if such would work.

Carry on!
Mark

Tony Spicer · #5 01-09-2010, 01:50 PM

Quote:

Originally Posted by F1Boss

I'm wondering about using a more RV4 style flap/fuselage intersection too. I might need to eyball a -3 to see if such would work.

I followed Randy Lervold's lead and used RV-8 flap fairings. Went on with no major refitting.

Tony

F1Boss · #6 01-09-2010, 02:42 PM

Quote:

Originally Posted by Tony Spicer

I followed Randy Lervold's lead and used RV-8 flap fairings. Went on with no major refitting.

Tony

Yep -- we have those here, ready to go, but those are for the upper side, if I understand their application correctly. I was looking at the bottom side...any tips there? Would the RV4 style fairing that fairs the fwd fuse sq corner into the rolled aft skin contour make life easier when fitting the flaps to the fuse profile? I'm not there yet, so consider me blissfully ignorant!

Carry on!
Mark

Tony Spicer · #7 01-09-2010, 04:15 PM

Quote:

Originally Posted by F1Boss

Yep -- we have those here, ready to go, but those are for the upper side, if I understand their application correctly. I was looking at the bottom side...any tips there?

Here's what worked for me:

http://picasaweb.google.com/tonyboyt...40199274333330

http://picasaweb.google.com/tonyboyt...40130554856562

http://picasaweb.google.com/tonyboyt...40164914594946

http://picasaweb.google.com/tonyboyt...13590717957570

Tony

randylervold · #8 01-11-2010, 09:45 PM

You guys are bringing back memories for me! I remember discovering that the ribs were not symmetrical early on and did something to make them symmetrical... check out the pic below, you can just see the ribs coming out from under the battery...

Michael White · #9 01-12-2010, 04:57 AM

Quote:

Originally Posted by randylervold

You guys are bringing back memories for me! I remember discovering that the ribs were not symmetrical early on and did something to make them symmetrical... check out the pic below, you can just see the ribs coming out from under the battery...

Randy,
Is the blue fitting on the left the one for the auxiliary (portable) fuel tank you installed? I always thought that was one of the cooler touches you added to your 3.

Something you might want to think about, Paul...

Best,

randylervold · #10 01-12-2010, 07:05 PM

Quote:

Originally Posted by Michael White

Randy,
Is the blue fitting on the left the one for the auxiliary (portable) fuel tank you installed? I always thought that was one of the cooler touches you added to your 3.

Something you might want to think about, Paul...

Best,

Yep. I never put the tank in and tried it though. I even had a custom Andair fuel valve with an AUX position.

With balanced fuel injectors, LOP operation, and low power settings I was able to stretch the 29.7 gallon existing capacity to pretty amazing limits. I flew one leg of 833 sm and had 4.5 gallons left. My mpg figures always beat all the other RVs I flew with... combination of that small slippery airframe and an efficient engine (balanced injectors, electronic ignition).