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Adding RV-8 gussets to the firewall weldments

Ian

Member
Could anyone help me figuring out how it should go with those RV-8 gussets ?

Do we need both upper AND lower gussets ?....though which RV-8 parts to be ordered ?...

are we talking about those :

F-854PP-L UPPER LONGERON GUSSET
F-854PP-R UPPER LONGERON GUSSET
F-855PP-L LOWER LONGERON GUSSET
F-855PP-R LOWER LONGERON GUSSET

..and which one is going where ?...

Thanks !
 
Do we need both upper AND lower gussets ?
You don't need any - just an option someone has suggested as a good idea.

We copied Randy's idea - see Link
Firewall weldment gussets
Both the RV-4 and RV-8 have gussets extending from the lower firewall weldment up onto the vertical angle in the vertical plane, and at the top weldments in the horizontal plane, whereas the RV-3 does not ? I remembered this having built an RV-8. Turns out you can use the RV-8 gussets, p/n F-855PP-R and F-855PP-L, which fit with only a very minor modification. This mod is not approved by Van's, and you always need to be careful when you shift load from one place to another, but this made sense to me. The parts are about $2.50 each from Van's.
Andy
 
Roger that....Thanks !

understood it is NO mandatory mod, but can understand also it is a good idea that may serve rigidity.

...according to Randy's depiction and comments, it seems F-855PP-R & L are for lower weldments...as I have no drawing nor image of both those RV-8 parts, my question actually was : would F-855PP-R & L do the job for upper weldments as well or might need to use the F-854PP-R & L for that specific location ?
 
I fit the upper gussets horizontally. I think the only pic of them is on the Electrical page...

DSC_0618.jpg
 
RV3 firewall gussets

At least half of the -3's out there were built with a fuselage fuel tank (incl. mine) - the tank goes right up into the corners where those gussets in the photos are located. No one has had a problem with side loads, to my knowledge, with or without gussets. I imagine that the top & bottom skins carry the side loads adequately on the fwd fuselage.

If you want to strengthen that area, I suggest adding more material to the four triangular plates that rivet to the corners of the firewall. If you operate the plane regularly on unimproved strips, those welded plates have been known to develop cracks under the engine mount bolts, both in the -3 and -4. I've never seen it myself, but if the urge to make the airplane better is irresistable (can't blame ya!), that might be worth investigating.

- Steven
700 -3 hrs
(two more yesterday!)
 
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