S.I. or S.L. Re/Fuel Tank Spar Mod

I've looked - but no joy on Van's S.I. or S.L. regarding modifying early -3, -4 & -6 forward fuel tank attachment to allow a clean breakaway of the tank (and wing) in case of an accident. I know it is out there somewhere - I just wasn't having any luck finding it.

Thx in advance.

HFS


Addendum: I found what I was looking for in the 1st issue of the 1998 RVator - Fuselage/Fuel Tank Bracket. The modification is listed as a "recommendation", and is not mandatory. However, the drawings for aircraft built after this date had their drawings changed to reflect this change.

I.E. - My original drawing #5, drawn by Van on January 10, 1984 does not show the change. The revised drawing, dated July 15, 1998 lists the change as a build requirement.

I thought I had a copy of it, but no joy. Mod is very simple, though. The attach brackets are more or less parabolic curve mirror images of each other, with the tips overlapped. There's a hole through each, filled by a single bolt. Remove the bolt (and the tank... ). Convert one bracket thusly: Extend the hole so that it becomes a horizontal slot the same width as the hole diameter, open all the way to the apex of the parabola. Reassemble everything.

Now the bolt will prevent vertical movement of the leading edge relative to the fuselage, but if the wing is pushed back in a wreck, The slot will allow the brackets to slide apart horizontally without tearing the tank side bracket out of the tank.

Charlie

Interesting variations exist.

The RV-6 plans show the slot in the tank bracket, while the RV-7 plans show the slot in the fuselage bracket.

If you do it like the -7 then the tank probably will not have to be removed. The fuselage bracket bolts on and can be removed for slot cutting on the bench.

With some fiddling and approriate swear words I bet you could attach the MK-1000 nutplate to the the tank bracket while it is still in place.

Here is the original Vans note hidden in the Rvator - shown for a -4

https://books.google.com/books?id=4...=onepage&q=vans rv tank bracket slots&f=false

Page 111 if the link above isn't direct

RV-3B Drawing 5

Here's the RV-3B version. It's on drawing 5:



Dave