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New holes through main spar web RV-6

JordanGrant

Well Known Member
I want to move my fire extinguisher to be securely mounted to the front of the main spar on the pilot side (easily accessible in flight). The easiest way for me to mount it would be to drill some new holes through the main spar webs for long AN3 bolts. I would need to be very careful to avoid touching the main heavy parts of the main spar (the heavy aluminum bar at the bottom at top), but there is plenty of area in the middle that is just the thin web that presumably is not carrying any load for the wing.

Before I go drilling on the spar, though - any gotchas I'm not thinking of? Any reason I shouldn't do it that way?

Thanks for your thoughts!
 
is just the thin web that presumably is not carrying any load for the wing.
Thanks for your thoughts!

That ?thin web? carries the shear load which, by connecting the upper and lower spar caps (think ?I beam?) makes the assembly much harder to bend. My rule is to contact Vans before drilling any non-plan holes in any part of the spar assembly.
 
I want to move my fire extinguisher to be securely mounted to the front of the main spar on the pilot side (easily accessible in flight). The easiest way for me to mount it would be to drill some new holes through the main spar webs for long AN3 bolts. I would need to be very careful to avoid touching the main heavy parts of the main spar (the heavy aluminum bar at the bottom at top), but there is plenty of area in the middle that is just the thin web that presumably is not carrying any load for the wing.

Before I go drilling on the spar, though - any gotchas I'm not thinking of? Any reason I shouldn't do it that way?

Thanks for your thoughts!

Why not use some longer bolts through the existing holes? I'd be really leery about drilling the spar.

Ed Holyoke
 
...and

"...but there is plenty of area in the middle that is just the thin web that presumably is not carrying any load for the wing..."


TLAR engineering is not advised here...call Van's; as has been posted, that is a shear web and it is there for a reason...
 
Actually, that spar web is carrying some , if not most, of the load. You may see large holes in the outboard sections of the web in some RV types, but these are in lower stressed areas. Contact Vans before modifying this critical part of the design.
 
Thanks for the thoughtful comments. I agree with the collective wisdom - time to consult the pros before drilling holes in that location. I have the question in with Van's to see what they say.

Cheers!
 
Some comments from a loooong time ago about drilling holes in the spar web:

This may have come from this forum or the matronics list server many years ago, but here goes...

The RV-6 has one factory provided hole in the left wing spar web to allow the manual pitch trim cable to pass through. It was desired by builders to drill an additional hole to allow wiring to pass from the front side to the aft side of the spar. After some years of "deliberation" I believer Van allowed a mirror image of the existing hole that was provided in the left wing spar web to be implemented in the right wing spar web.

As others have stated above, it is best to call Van's support.
 
Some comments from a loooong time ago about drilling holes in the spar web:

This may have come from this forum or the matronics list server many years ago, but here goes...

The RV-6 has one factory provided hole in the left wing spar web to allow the manual pitch trim cable to pass through. It was desired by builders to drill an additional hole to allow wiring to pass from the front side to the aft side of the spar. After some years of "deliberation" I believer Van allowed a mirror image of the existing hole that was provided in the left wing spar web to be implemented in the right wing spar web.

As others have stated above, it is best to call Van's support.

I recall Van's adamantly stating that additional holes cannot be drilled in that piece, especially not in the middle of it. They were reluctant to allow another 5/8" hole at the extreme end of it. I feel pretty confidant they will not endorse any hole drilled in the middle of it.

Larry
 
I recall Van's adamantly stating that additional holes cannot be drilled in that piece, especially not in the middle of it. They were reluctant to allow another 5/8" hole at the extreme end of it. I feel pretty confidant they will not endorse any hole drilled in the middle of it.

Larry

rvbuilder2002 says -

Since it hasn't been mentioned....
It is acceptable to make a second hole in the right side spar stub, mirror image of the one on the left side originally intended for the manual pitch trim cable.
 
Just attach the extinguisher to the front spar covers over the fuel lines using the screw holes going into the z brackets. (Assuming the 6 has those like the 7 and 9 do... apologies in advance if this is a misassumption.) That’s where mine is. Going into the spar itself seems like overkill to me.
 
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Mounting tabs on close tolerance bolts

As suggested above for using spar doubler thru bolts, just replace existing washers with bent plates or tabs to accommodate the extinguisher. No change to existing structure to debate.
 
Just attach the extinguisher to the front spar covers over the fuel lines using the screw holes going into the z brackets. (Assuming the 6 has those like the 7 and 9 do... apologies in advance if this is a misassumption.) That?s where mine is. Going into the spar itself seems like overkill to me.

The RV6 doesn't have that cover or any of those brackets.
 
Floor attach?

What about attaching the extinguisher to the floor, beside the spar/seat edge?
 
Pilot armrest

I have my small extinguisher mounted on the armrest. With a towel on it; kinda comfy and easier to reach than on the front of the spar.
 
PAX Seat Back Brace (F-638)

My Halon extinguisher bracket is mount on the passenger seat back brace (F-638) and is very easy to reach with or without a PAX. I did use some velcro to help hold it in place but it is very easy to pull away if it is ever needed.

Note: This was not my idea. I first saw it in Bill Flaherty's RV-6 twenty (20) some years ago. I thought it was a great idea and used it without permission.
 
That ‘thin web’ carries the shear load which, by connecting the upper and lower spar caps (think “I beam”) makes the assembly much harder to bend. My rule is to contact Vans before drilling any non-plan holes in any part of the spar assembly.

Actually guys, the vertical shear load is taken out very near to the side of the fuselage by the attachment bolts closest to the side, which go into the parts that make up the bulkhead; F-604, F-804, etc.

Once inboard of that point, there is NO shear in the spar, it is pure bending moment -- constant bending moment. (shear is the gradient of the bending moment).

So as much as we all are reluctant to cut holes 'willy-nilly' in the shear web in the center section area, it really is not doing much but keeping everything where it is supposed to be.
 
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