RVG8tor

RVG8tor

Well Known Member
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
 
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Works fine

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

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
 
SS Screws are OK

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...
 
DGlaeser said:
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...
Click to expand...
"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
 
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
 
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. :D
 
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
 
SS Screws

rocketbob said:
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. :D
Click to expand...

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.
 
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.
 
Closest to figuring it out.

SvingenB said:
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.
Click to expand...

Mr Svingen is the closest to figuring it out.

The stainless screws will corrode the aluminum faster than a Cadmium Plated fastener. Moisture will accelerate this. Contamination of minerals will further accelerate any corrosive effects.

The stainless screw may look prettier but will affect the structure sooner. A clean Cad plated Structural (125 ksi tensile strength) fastener that has not been installed and removed too many times will be a better fastener for the strength and structure of the aircraft. If your steel screws are crummy looking and bleeding rust at all, REPLACE THEM with new ones.

http://www.gen-aircraft-hardware.com/images/pdf/ms24694.pdf

In many places the non structural stainless screws can very functionally replace the non structural cad plated screws and be quite acceptable.

I would consider these that would have taken an AN507 / MS24693 screw and held fiberglass/plastic fairings on where the screw head rested on the fiberglass/plastic.

http://www.gen-aircraft-hardware.com/images/pdf/ms24693.pdf

For protruding head Cad Plated structral screws I like the AN525 or the MS27039

http://www.gen-aircraft-hardware.com/template.asp?pagename=an525

http://www.gen-aircraft-hardware.com/images/pdf/ms27039.pdf

For protruding head Cad Plated NONstructral screws I like the AN515, 520 or the MS35206, 35207

http://www.gen-aircraft-hardware.com/template.asp?pagename=ms35206_7

Many times there may be a large area countersunk washer under the countersunk screw. Do not allow this be placed right against the bare aluminum, it may create the same problems.



If you are at a stage where you really want Shiny and it is in a structurally acceptable location, paint the structure with NO screws in it. When it is all cured put the shiny Stainless washers over the cure paint and then your Stainless screws. The paint will be the buffer here keeping the fastener from actually touching the aluminum structure.

If you only fly in unpolluted air and fresh soft showers and you also are hangered the affects of all this molecular level corrosion may not show up for a very........ long time.

If you live close to the coast or are un-hangered you better be careful and diligent. I painted some flight school plains that were always parked outside. washed once a month and needed weeks worth of corrosion clean up/repair before we could even prime them. Where did it usually start, UNDER THE STAINLESS screws.

Do whatever you want, it is experimental you know!
But consider the costs in the long run. ;)
 
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Every Day Is An Education!!

Well I guess I will be changing out my tank screws.

I've been sold those MS24694C(stainless steel) screws with the claim they are the same strength as the the steel ones. After reading the last post by GAHco I did some research. Should have done the research first rather than just taking what I was being told as true.

The corrosion resistant screws(stainless steel) under this specification are in fact less strength. As soon as I found the mil-specification and saw they were 300 series stainless I new they weren't going to be 125,000 psi minimum strength.

As I said everyday is an education. Thanks GAHco.

Ted
 
Ted RV8 said:
Well I guess I will be changing out my tank screws.

I've been sold those MS24694C(stainless steel) screws with the claim they are the same strength as the the steel ones. After reading the last post by GAHco I did some research. Should have done the research first rather than just taking what I was being told as true.

The corrosion resistant screws(stainless steel) under this specification are in fact less strength. As soon as I found the mil-specification and saw they were 300 series stainless I new they weren't going to be 125,000 psi minimum strength.

As I said everyday is an education. Thanks GAHco.

Ted
Click to expand...

Your welcome!

And you will be potentially decreasing the possibility of skin corrosion by sticking with the original design.

As an additional tidbit of info, for the same basic design of the AN509 / MS24694(S) series, but a little more strength (not that its necessary for the basic RV) you may consider the NAS517 series. Cad II plated Alloy steel with 160 ksi minimum tensile strength.

The noticeable difference is that with a good # 2 bit it is hard to wreck the Phillips recess.

To get an awesome replacement for the soft AN507 /MS24693 fully threaded countersunk screws, the NAS514 are tough in tension and have good recess durability but are not to be used where a un threaded shank is called for. The biggest gain is in the smaller 4-40 and 6-32 screws as their minor diameters are so puny, that the higher alloy steel makes them more durable.

http://www.gen-aircraft-hardware.com/images/pdf/countersunk_structural.pdf

Just yakkin,:D I have not been on the forum much the last year and the light disappears too early for my liking.

Hope this helps someone keep from getting a Hardware Headache:rolleyes:
 
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