RV-8A slow Build Fuselage - Firewall / Forward Floor Panel

Hi folks,

scratching my head here (RV 8A slow build fuselage). The instructions say to countersink the 9 central holes in the bottom of the lower angle on the firewall assembly and dimple the corrseponding holes in the foreward floor panel. So far so good, but the the outer holes of the 9 holes are also shared with the F-893 floor ribs. The material of the floor ribs is too thick for dimpleing, but requires countersinking. So what's the story here - countersink the two holes in the floor ribs and leave the corresponding holes in forward floor panel and lower angle alone (i.e. not countersunk or dimpled)?

Also, if the cooling air ramp is later on installed, wouldn't there some shiming required for the 7 holes in the middle, since the cooling air ramp sits on the flanges of the floor ribs as well?

Kinda lost here - appreciate your help.

Thanks

Thilo

Thos outer holes

Are all covered up with the double floor, you will be using round head rivets on those. You dimple and countersink the center 9 cause they are exposed by the cooling air ramp. I am looking at drawing 61A. And a quick cruise to the garage confirms thats what I did. Good luck, build on

Randy
8A finishing, FWF

Hi Randy,

thanks. Could you please check the most outermost holes of the 9 center holes - they should go through the cooling air ramp, the forward floor rib, the forward floor panel, and finally through the lower angle on the firewall. Those are the two, that made me scratch my head. For those two holes, do I just countersink the forward floor ribs and dimple the cooling air ramp? And how is the cooling air ramp sitting flush on the forward floor panel, if it also sits on the flanges of the two forward floor ribs? I guess, I'm a bit confused. Any help is highly appreciated.

Thanks

Thilo

It Won't!

thilokind said:

Hi Randy,

thanks. Could you please check the most outermost holes of the 9 center holes - they should go through the cooling air ramp, the forward floor rib, the forward floor panel, and finally through the lower angle on the firewall. Those are the two, that made me scratch my head. For those two holes, do I just countersink the forward floor ribs and dimple the cooling air ramp? And how is the cooling air ramp sitting flush on the forward floor panel, if it also sits on the flanges of the two forward floor ribs? I guess, I'm a bit confused. Any help is highly appreciated.

Thanks

Thilo

Click to expand...

Thilo,
I fabricated a shim (same thickness as the inboard ribs) to go between those skins on my 8A. I can supply photos off list if desired. The photos mentions can be found below. See

http://www.vansairforce.com/community/showpost.php?p=319660&postcount=14

To view the entire thread see

http://www.vansairforce.com/community/showthread.php?t=29475

Charlie Kuss

what Charlie said

Fab a shim to go inbetween the ribs, dimple the ramp, and countersink the shim and the 2 holes, rib ends, that are common with the cooling air ramp.

Randy

And while you're at it beef up the ramp. It vibrates like **** (exhaust pulses ?) and is subject to cracking. I recommend connecting the stiffener in the center of the ramp to the angles on each side. Mine cracked out at the end rivet holes of the stiffener within 50 hrs. It would have been much easier to beef it up while building.

I Bet

jamiller said:

And while you're at it beef up the ramp. It vibrates like **** (exhaust pulses ?) and is subject to cracking. I recommend connecting the stiffener in the center of the ramp to the angles on each side. Mine cracked out at the end rivet holes of the stiffener within 50 hrs. It would have been much easier to beef it up while building.

Click to expand...

It was probably from landing on the tundra

The ramp needs more support to avoid cracking

jamiller said:

And while you're at it beef up the ramp. It vibrates like **** (exhaust pulses ?) and is subject to cracking. I recommend connecting the stiffener in the center of the ramp to the angles on each side. Mine cracked out at the end rivet holes of the stiffener within 50 hrs. It would have been much easier to beef it up while building.

Click to expand...

John is giving you great advice here. I recommend doing away with the hinge in the rear and re-enforcing the ramp. Vans originally intended to make this ramp movable (to reduce in cowl drag), but dropped the idea. The design was kept, however. I can supply photos off list to how I did this on my 8A. Contact me via email.
Charlie Kuss