Stainless Screw on the tanks

RVG8tor · #1 10-31-2008, 10:26 AM

I purchased some stainless screws to use on the interior consoles and I am thinking of using some stainless screws on my tanks. The QB tanks look OK but some of the screw do not sit as flush as I would like. Has anyone done this, are there any draw backs. I picked up my other screws from

Micro Fasteners

I really like the button screw I will use on the interior panels, the button head is slightly smaller than the -8 screws that come with the kit.

With all the screws that hold on the tank I can't see how non aviation screws would effect the strength much. I may be missing some drawback. Anyone else consider this.

Cheers

RV7Guy · #2 10-31-2008, 10:35 AM

I used stainless screws on my tanks and wing tips. They work fine and look great.

Ted RV8 · #3 10-31-2008, 11:13 AM

The screws mounting the tanks to the wing are structural. I wouldn't use commercial stainless screws here.

Van's calls the screws out as AN509-8R8 which is MS24694-S5 screws. Use AN-509C-8R8 or MS24694C5 Screws. These are the stainless steel version of the screw with the same structural strength and specification. The MS seems to be the new spec callout for the AN screws. These can be purchased from Aircraft Spruce or Wicks.

I wouldn't second guess the engineering of Van's in this area regardless of the amount of srews used.

Ted

DGlaeser · #4 10-31-2008, 11:54 AM

The strength has been discussed and it is a non-issue, they are plenty strong. I've got the Micro Fastener screws in my tanks.
I've read in a couple places that Van's replaces most of their screws with SS as well...

rvbuilder2002 · #5 10-31-2008, 05:28 PM

Quote:

Originally Posted by DGlaeser

The strength has been discussed and it is a non-issue, they are plenty strong. I've got the Micro Fastener screws in my tanks.
I've read in a couple places that Van's replaces most of their screws with SS as well...

"Most" would be an accurate statement...since the only screws
that they don't replace with stainless are the AN509's attaching the tanks to the wings

N200PF · #6 10-31-2008, 05:35 PM

I bought the same screws from M.F. to use all over my plane a month ago and liked the way they sat down in the #8 dimples as well. I called Van's and asked them about the stainless vs. the AN509-8R8's in the tanks and they said absolutely not!

The reason is the two fold. First, stainless is much more brittle and will not flex. If loaded it just breaks. Second, the tensile strength of a stainless screw is about 1/4 that of a structural screw.

That was enough for me to put in the AN509-8R8's and fly'em like Van's intended. I don't want to be thinking about my tank screws at the bottom of a loop.

- Peter

rocketbob · #7 10-31-2008, 05:43 PM

The skin will tear to the trailing edge of the tank long before the screws will fail. SS is fine, mine's been flying with SS screws for 8+ years, and I've pulled a lot of G's.

N200PF · #8 10-31-2008, 05:53 PM

Bob -

The RV-6 tanks are attached differently than the -7's if I recall. The only other piece of structure on the -7's supporting the tanks are the Z-brackets which are basically spacers. There is only one row of screws on the -7 and two rows (zig zag) on the -6.

...just my opinion but it's not worth the risk for the benefit.

- Peter

mannanj · #9 10-31-2008, 06:53 PM

Quote:

Originally Posted by rocketbob

The skin will tear to the trailing edge of the tank long before the screws will fail. SS is fine, mine's been flying with SS screws for 8+ years, and I've pulled a lot of G's.

I've been flying with the Micro Fastener SS screws in my -8 from day one. 240 hrs plus and I have no reservations. I've been hammered with turbulence that I was afraid to look out to check whether the wings were still on or not!

It would be interesting for someone with the proper test equipment to do a pull test with countersunk #8 SS screws in .032 2024-T3 skin into the equivalent of the wing spar to see where the failure point would be. I'm with Rocket Bob on this one.

SvingenB · #10 11-01-2008, 03:29 AM

I find it a bit odd that when Van's say "absolutely not", some still want to persuade the opposite. For me, living by the sea, SS and aluminum will cause the aluminum to corrode instead of the fasteners. Meaning in case of corrosion I will have to change skins and spars instead of a couple of screws.