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Michael Wynn

Joined: 10 Jan 2006
Posts: 148
Location: San Ramon, CA

Posted: Thu Apr 27, 2006 1:26 pm Post subject: Platenut Life

Hi all,

 

Do I need to worry about platenuts loosing their locking ability from  

running screws in and out too frequently?  Anyone know what the life  expectancy is 

in terms of this?  I am working on the tanks and was  scratching my head about 

when to rivet on the platenuts.

 

Regards,

 

Michael Wynn

RV 8 Wings (tanks)

San Ramon, CA

_________________
Michael Wynn
RV 8
San Ramon, CA

Mark Phillips in TN

Joined: 10 Jan 2006
Posts: 431
Location: Columbia, TN

Posted: Thu Apr 27, 2006 6:18 pm Post subject: Platenut Life

Hi Michael-



I know this will start a storm of incandescent blowtorches from listers, but 

in MY experience, FWIW, I tapped every freakin' platenut on my plane and have 

never, I repeat NEVER experienced a single one of them loosening as a result- 

YMMV, but I must have installed 500 of the freakin' things (all floorboards, 

tanks, interior panels, wingroot fairings, baggage bulkhead etc.) and would do 

it again in a heartbeat.



And by the way- my name is PHILLIPS and if there is ANY way I can avoid a 

PHILLIPS screw, it shall be done- I've used the torx fasteners from 

microfasterners.com with spectacular results, and you'll be glad you did the same- no 

gratuities from them, but I am in the torx camp and intend to stay there...



(Pheeew!  Do I get worked up sometimes or WHAT?!)



I mean it-

Mark Phillips - RV-6A N51PW, 300 hours and not a screw loose yet except maybe 

in the right seat!    http://websites.expercraft.com/n51pw/



p.s. - I'd happily build an RV for you and every one of them suckers would 

have a nice sharp tap drilled mercilessly thru it!

_________________
From The PossumWorks...

mannanj(at)alltel.net
Guest

Posted: Thu Apr 27, 2006 7:56 pm Post subject: Platenut Life

I wholehartedly second the emotion!  Tap them suckers and Torx forever. 

Microfasteners.com---a bit more expensive, but worth every penny.  They 

don't call them Torx, something like six lobe drive I believe.



Mannan Thomason

RV-8  N161RL  (# 1 Girl)

Engine running, almost ready to fly.



Please do not archive



---

Michael Wynn

Joined: 10 Jan 2006
Posts: 148
Location: San Ramon, CA

Posted: Thu Apr 27, 2006 8:40 pm Post subject: Platenut Life

Thanks, gents



Are you using torx screws to hold the fuel tanks on?



Regards,



Michael Wynn

RV-8, Wings

San Ramon, California



Do Not Archive

_________________
Michael Wynn
RV 8
San Ramon, CA

Mark Phillips in TN

Joined: 10 Jan 2006
Posts: 431
Location: Columbia, TN

Posted: Fri Apr 28, 2006 2:50 am Post subject: Platenut Life

In a message dated 04/27/2006 11:41:46 PM Central Daylight Time, 

MLWynn(at)aol.com writes:

Are you using torx screws to hold the fuel tanks on?

 	  Quote: 	
		  >>


	


Yessir- get 'em here:

http://www.microfasteners.com/catalog/products/SSCFCMXS.cfm



Mark do not archive

_________________
From The PossumWorks...

dreel(at)cox.net
Guest

Posted: Fri Apr 28, 2006 3:59 am Post subject: Platenut Life

Having driven screws in and out of the same platenut many times, it seems to

me that the platenut looses some of it's resistance once the first screw is

driven but that it retains it's remaining resistance over time.  I think the

same rule

applies here as is used with elastic stop nuts.  If you can turn a screw all

the way through the platenut to where the threads are coming out the other

side by hand, it's too loose to provide security against loosening with

vibration.  You need to feel some drag from the platenut before the screw

gets tight.  I would never run a tap through a platenut as that destroys

it's holding power.  The type of head on the screw has nothing to do with

the issue of platenut holding power which I believe was the main thrust of

your post.  I'd feel free to rivet them in place anytime.



Dave Reel - RV8A

hawk(at)digisys.net
Guest

Posted: Fri Apr 28, 2006 6:20 am Post subject: Platenut Life

 	  Quote: 	
		   



 In a message dated 04/27/2006 11:41:46 PM Central Daylight Time,

 MLWynn(at)aol.com writes:

 Are you using torx screws to hold the fuel tanks on?

>>>



 Yessir- get 'em here:

 http://www.microfasteners.com/catalog/products/SSCFCMXS.cfm



 Mark do not archive


	


Anyone considering using the Microfastener screws should recognize that they 

are AN507 style (non-structural with the threads all the way to the 

countersunk head, rather than the shanked structural style of the AN509 

series.)  Combine this with the effects of  employing Stainless vs. Alloy 

Steel  as the screw material, and the resultant reduction in tensile 

strength as compared to the plans called-out steel AN509's is probably at 

least 50%.



If disruption of the .032 tank skin itself would be expected to occur at a 

much lower levels of stress, then this tradeoff in screw structural strength 

may be justifiable.  I hope that some of the structural engineers on the 

List would comment on that.



Hawkeye Hughes



 	  Quote:

jim jewell

Joined: 09 Jan 2006
Posts: 82
Location: Kelowna B.C. Canada

Posted: Fri Apr 28, 2006 9:08 am Post subject: Platenut Life

If you prefer to preserve or at least extend the anti-vibration capability 

of plate nuts apply some Boelube to the screw threads when first installing 

them.



Of course there are other products that work about the same. I just prefer 

this brand.



Using Boelube on screw threads after they have been installed and removed 

without a thread prep material of some sort will also help.

The Boelube acts as a cutting agent allowing the threads to polish or 

condition each other during installation, minimizing the galling of the 

similar materials.

You will find that screws treated this way require much less force to 

install and breakage of the smaller size screws will be reduced if not 

avoided altogether.

I obtained the "Boelube" product referred to above from Avery tools.

The RV is all but done and I still have at least 3/4 of the little Boelube 

tube left for the next RV project?!



Jim in Kelowna

---

_________________
"I never make mistreaks"

Jim Anglin

Joined: 10 Jan 2006
Posts: 47
Location: Independence, OR (7S5 Airpark)

Posted: Fri Apr 28, 2006 9:33 am Post subject: Platenut Life

I had an '87 RV4 and took the boot cowl off frequently and the nut =

plates still caused me to strip out the cross if I wasn't careful.

Jim Anglin

HR II N144HR

DO NOT ARCHIVE

_________________
Jim Anglin
HR II N144HR

skylor4(at)yahoo.com
Guest

Posted: Fri Apr 28, 2006 12:06 pm Post subject: Platenut Life

True, but any fastener smaller than a -3 is supposed

to be non-structural anyway.  I believe that the

"structural" portion of fuel tank attachment comes

from the "Z" brackets fastened to the wing spar, and

the bracket between the root rib and the fuselage. 

The flush "skin" screws are simply to hold the skin

down to the spar, & not for carrying structural loads.



Skylor

RV-8 Under Construction



--- REHughes <hawk(at)digisys.net> wrote:



 	  Quote: 	
		   Anyone considering using the Microfastener screws

 should recognize that they 

 are AN507 style (non-structural with the threads all

 the way to the 

 countersunk head, rather than the shanked structural

 style of the AN509 

 series.)  Combine this with the effects of 

 employing Stainless vs. Alloy 

 Steel  as the screw material, and the resultant

 reduction in tensile 

 strength as compared to the plans called-out steel

 AN509's is probably at 

 least 50%.

 

 If disruption of the .032 tank skin itself would be

 expected to occur at a 

 much lower levels of stress, then this tradeoff in

 screw structural strength 

 may be justifiable.  I hope that some of the

 structural engineers on the 

 List would comment on that.

 

 Hawkeye Hughes

 

 

 

 

 

 

 

 

 

 >

 >

 >

 >

 >

 >

 >

 >

 >

 >

 >

 >

 >

 >

 > 

 

 

 

 

 



 browse

 Subscriptions page,

 FAQ,

 Admin.



 

 

 

  

  

  

 

 

 

 


	




__________________________________________________

Do You Yahoo!?

Tired of spam?  Yahoo! Mail has the best spam protection around 

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jamie(at)jpainter.org
Guest

Posted: Fri Apr 28, 2006 12:50 pm Post subject: Platenut Life

The -6 and -4 (and maybe -3) tanks do not have z-brackets and I believe 

are held on *only* by the screws, although there's a double-row of them 

and some reinforcement stuff going on underneath.  Someone with an older 

RV can probably fill in the details.



do not archive



Jamie

http://rv.jpainter.org



Skylor Piper wrote:



 	  Quote: 	
		  



True, but any fastener smaller than a -3 is supposed

to be non-structural anyway.  I believe that the

"structural" portion of fuel tank attachment comes

from the "Z" brackets fastened to the wing spar, and

the bracket between the root rib and the fuselage. 

The flush "skin" screws are simply to hold the skin

down to the spar, & not for carrying structural loads.



Skylor

RV-8 Under Construction



--- REHughes <hawk(at)digisys.net> wrote:



  



>Anyone considering using the Microfastener screws

>should recognize that they 

>are AN507 style (non-structural with the threads all

>the way to the 

>countersunk head, rather than the shanked structural

>style of the AN509 

>series.)  Combine this with the effects of 

>employing Stainless vs. Alloy 

>Steel  as the screw material, and the resultant

>reduction in tensile 

>strength as compared to the plans called-out steel

>AN509's is probably at 

>least 50%.

>

>If disruption of the .032 tank skin itself would be

>expected to occur at a 

>much lower levels of stress, then this tradeoff in

>screw structural strength 

>may be justifiable.  I hope that some of the

>structural engineers on the 

>List would comment on that.

>

>Hawkeye Hughes

>

>    

>

>>

>>

>>

>>

>>

>>

>>

>>

>>

>>

>>

>>

>>

>>      

>>

>

>

>browse

>Subscriptions page,

>FAQ,

>Admin.

>

>

> 

> 

> 

>

>

>    

>

__________________________________________________

Do You Yahoo!?

Tired of spam?  Yahoo! Mail has the best spam protection around 

http://mail.yahoo.com

Michael Wynn

Joined: 10 Jan 2006
Posts: 148
Location: San Ramon, CA

Posted: Fri Apr 28, 2006 2:22 pm Post subject: Platenut Life

I sent an email to Microfasteners to inquire about the specs on the  screws.  

Here is what they said:

Our stainless steel 100 degree flat head torx drive screws are all  intended

to replace the cross recessed screws of NASM24693 covering  non-structural

screws. Their tensile strength is 85,000 psi minimum, same as  the

requirement for structural screws of NASM24694, so the tensile strength  for

8-32 screws is 1190 lbs, minimum.



We emphasize that these are not  mil spec screws; first no testing has been

done to verify that, apart from  the different drive, they meet the

requirements of either of the specs listed  above, and second there is no mil

spec covering these screws, to the best of  our knowledge.



Thanks for the inquiry.



John Fleisher

Micro  Fasteners



Interesting, eh?

_________________
Michael Wynn
RV 8
San Ramon, CA

hawk(at)digisys.net
Guest

Posted: Fri Apr 28, 2006 4:22 pm Post subject: Platenut Life

 	  Quote: 	
		   



 I sent an email to Microfasteners to inquire about the specs on the

 screws.

 Here is what they said:

 Our stainless steel 100 degree flat head torx drive screws are all

 intended

 to replace the cross recessed screws of NASM24693 covering  non-structural

 screws. Their tensile strength is 85,000 psi minimum, same as  the

 requirement for structural screws of NASM24694, so the tensile strength

 for

 8-32 screws is 1190 lbs, minimum.



 John Fleisher

 Micro  Fasteners



 Interesting, eh?


	


To complete the comparison, the Alloy Steel An509 / MS24694 screws that

Van's calls out are listed at 125,000 to 145,000 psi



Hawkeye

Bill Schlatterer

Joined: 09 Jan 2006
Posts: 195

Posted: Sat Apr 29, 2006 7:09 am Post subject: Platenut Life

Why tap them?  A drop of Bolube on the screw and it goes in easy, comes out

easy ???  Why all the trouble ?  Is there some reason to put the screws in

dry ?



Bill S

7a wiring



--

gert.v(at)sbcglobal.net
Guest

Posted: Sat Apr 29, 2006 9:23 am Post subject: Platenut Life

Bill



I have had batches where even boelube did not work, they were plainly 

over squeezed by a bit. I too have run a tap through several platenuts 

depending on ease of access, structural function etc. E.g. i have used 

plate nuts for my floor in my -8, i ran the tap at least partially in 

the platenuts. actually i have a tap with a slightly longer taper, it 

cleans the threads, but does not remove the squeeze all the way.



gert.



Bill Schlatterer wrote:

[quote] 



 Why tap them?  A drop of Bolube on the screw and it goes in easy, comes out

 easy ???  Why all the trouble ?  Is there some reason to put the screws in

 dry ?



 Bill S

 7a wiring



 --

mannanj(at)alltel.net
Guest

Posted: Sat Apr 29, 2006 8:34 pm Post subject: Platenut Life

Gert:



This happened to me.  Had a batch of 200 that were over squeezed.  Every one 

I tried would "cam out" and ruin the head of the screw.  That's why I like 

the Torx head screws.  Out of desperation, I ended up running a tap 

partially through all but couple of them. (Should have explained that in my 

earlier post.)  Guess where the couple that I missed ended up.  You're 

right, in the corners where you can't get a screwdriver square on them. 

They're a bitch to remove one eighth of a turn at a time with vise grips.



For others out there reading this.  In most aplications on these airplanes, 

the Microfastener SS 65,000 PSI strength is more than sufficient.  In 

aplications that call for a shank on the screw vs. threaded all the way, 

then clearly the AN hardware is preferred.  If you're new at building and 

don't have a lot of mechanical experience, when in doubt about a particular 

situation, consult someone knowledgeable and seek their advice.  Get to know 

your EAA Technical Advisor  Buy the local A&P or AI a cup of coffee or beer 

or even pay for their time and invite them over for a look at your project. 

Any advice you see on this website, or any other is worth exactly what you 

paid for it. $0.00  (Mine included, except for the seek competent help and 

advice.)



Mannan Thomason

RV-8  Engine running, looks like a real airplane!  Flying soon.

 ---

Bob Barrow

Joined: 11 Jan 2006
Posts: 29

Posted: Sat Apr 29, 2006 9:02 pm Post subject: Platenut Life

 	  Quote: 	
		  



  I believe that the "structural" portion of fuel tank attachment comes
	


 	  Quote: 	
		  from the "Z" brackets fastened to the wing spar, and

the bracket between the root rib and the fuselage.

The flush "skin" screws are simply to hold the skin

down to the spar, & not for carrying structural loads.


	




Why do you "believe" that. On what basis do you state that opinion. I would 

suggest to you that the tanks skins carry considerable load and that those 

loads will want to transfer to the spar by the  most direct route...which 

will be primarily through the #8 skin screws.



_________________________________________________________________

New year, new job  there's more than 100,00 jobs at SEEK 

http://a.ninemsn.com.au/b.aspx?URL=http%3A%2F%2Fninemsn%2Eseek%2Ecom%2Eau&_t=752315885&_r=Jan05_tagline&_m=EXT

rv8ch

Joined: 10 Jan 2006
Posts: 250
Location: Switzerland

Posted: Sat Apr 29, 2006 11:00 pm Post subject: Platenut Life

 	  Quote: 	
		   

> 

>

> I believe that the "structural" portion of fuel tank attachment comes

> from the "Z" brackets fastened to the wing spar, and

> the bracket between the root rib and the fuselage.

> The flush "skin" screws are simply to hold the skin

> down to the spar, & not for carrying structural loads.

 

 Why do you "believe" that. On what basis do you state that opinion. I would 

 suggest to you that the tanks skins carry considerable load and that those 

 loads will want to transfer to the spar by the  most direct route...which 

 will be primarily through the #8 skin screws.


	


Does the fact that the skin is dimpled help carry load,

or do the screws themselves carry the load?



Won't the aluminium skin fail long before the "wimpy" SS screws?



I recall someone doing a write-up on rivet strength in shear,

and one of the results was that a dimpled skin with a flush

rivet was much stronger than any other type of rivet, with

the conclusion that the dimpled skin was carrying load.

Perhaps someone else knows where to find that report.



-- 

Mickey Coggins

http://www.rv8.ch/

#82007 finishing

do not archive

_________________
Mickey Coggins
http://www.rv8.ch/

khorton01(at)rogers.com
Guest

Posted: Sun Apr 30, 2006 2:23 am Post subject: Platenut Life

On 30 Apr 2006, at 02:54, Mickey Coggins wrote:



 	  Quote: 	
		   



> 

>> 

>>

>> I believe that the "structural" portion of fuel tank attachment  

>> comes

>> from the "Z" brackets fastened to the wing spar, and

>> the bracket between the root rib and the fuselage.

>> The flush "skin" screws are simply to hold the skin

>> down to the spar, & not for carrying structural loads.

>

> Why do you "believe" that. On what basis do you state that  

> opinion. I would

> suggest to you that the tanks skins carry considerable load and  

> that those

> loads will want to transfer to the spar by the  most direct  

> route...which

> will be primarily through the #8 skin screws.



 Does the fact that the skin is dimpled help carry load,

 or do the screws themselves carry the load?



 Won't the aluminium skin fail long before the "wimpy" SS screws?



 I recall someone doing a write-up on rivet strength in shear,

 and one of the results was that a dimpled skin with a flush

 rivet was much stronger than any other type of rivet, with

 the conclusion that the dimpled skin was carrying load.

 Perhaps someone else knows where to find that report.


	


Bill Marvel's report is at:



http://www.kilohotel.com/rv8/rvlinks/marvelrivets.html



I know there are a number of RVs flying with SS screws instead of AN  

hardware on the fuel tanks, and I haven't heard of any failures yet.   

But that is an experiment that I personally don't want to do.  I'm  

reminded of an Australian P-3 that was subjected to a significant  

overstress.  The aerodynamic loads were high enough that the wing  

leading edges came off the spar, destroying the ability of the wing  

to function, leading to a fatal accident.



SS screws in the tank attachments may work just fine, until the day  

that there is an significant, inadvertent overstress.  Then you could  

discover that the aircraft no longer has the hoped for 1.5 factor of  

safety, as the tanks come off well before the spar fails.



Kevin Horton         RV-8 (finishing kit)

Ottawa, Canada

http://www.kilohotel.com/rv8

wjoke(at)shaw.ca
Guest

Posted: Mon May 01, 2006 5:30 am Post subject: Platenut Life

Not to muddy the waters too much on this but the loading situation on 

the tank screws is surely a single shear situation with some clamping 

friction which "may" be enhanced by the dimpling of the underlying 

structure depending on the quality of the work. In other words, simple 

comparison of the tensile strength of the SS screw versus a steel screw 

are not the appropriate comparison in assessing this joint. Agree that 

greater tensile strength in the screws would allow more clamping 

friction to be generated when torquing the screws down and so, in 

theory, provide greater load ability.



In a positive G pull up, the mass of the fuel in the tank will tend to 

rotate the tank LE downward putting the upper aft edge of the tank skin 

in tension. There is no clear rotation point but the lower skin should 

be in compression and there could be a skin failure due wrinkling before 

the screws become heavily stressed. The tank baffle (aft side of the 

tank) should at some point come into contact with the spar structure if 

the lower tank skin starts wrinkling which would make the strength in 

the lower screws irrelevant past this point.



The outer end of the tank is supported by the tank skin lap to LE joint 

which will support some of the load as would the inboard tank support 

bracket that mates with the equivalent item on the fuselage. Not all RV 

models have this however.



Just looking at the situation, my thoughts are that the screw spacing is 

driven as much by the need for a neat and tidy tank to wing join vice 

any loading consideration. The loading envelope involves a lot more 

positive G than negative G which would imply that the upper surface 

screws are more heavily stressed and there would/should be a need for 

more screws on the top of the tank than the bottom if the strength 

requirement was critical. AFAIK, most of the RV designs use the same 

spacing top and bottom which suggests that the tank to wing join may be 

simply a case of "intelligent overdesign".



As Kevin notes, using something besides the tried and proven fasteners 

is getting into the nature of an experiment with serious consequences if 

it goes wrong. This is the sort of thing that calls for a ground static 

load test to destruction to see what fails first, etc. (just in case 

anyone has a spare set of wings they would want to sacrifice). Vans has 

done static load testing of some of the RV wing designs but the pictures 

I have seen do not look like they added any extra load to replicate the 

mass of the fuel in the tanks. That is, they were looking more at spar 

bending strength than tank to wing joint integrity.



A final thought is that examination of  RVs that have crashed with 

significant vertical velocity leading to a lot of positive G should 

indicate how and if the tanks separate from the wing structure. Has 

anyone seen such a crashed RV with anything to report?



Jim Oke

RV-3, RV-6A

Wpg, MB

Kevin Horton wrote:



 	  Quote: 	
		  



On 30 Apr 2006, at 02:54, Mickey Coggins wrote:



  



>

>

>    

>

>>

>>      

>>

>>>

>>>

>>>I believe that the "structural" portion of fuel tank attachment  

>>>comes

>>>from the "Z" brackets fastened to the wing spar, and

>>>the bracket between the root rib and the fuselage.

>>>The flush "skin" screws are simply to hold the skin

>>>down to the spar, & not for carrying structural loads.

>>>        

>>>

>>Why do you "believe" that. On what basis do you state that  

>>opinion. I would

>>suggest to you that the tanks skins carry considerable load and  

>>that those

>>loads will want to transfer to the spar by the  most direct  

>>route...which

>>will be primarily through the #8 skin screws.

>>      

>>

>Does the fact that the skin is dimpled help carry load,

>or do the screws themselves carry the load?

>

>Won't the aluminium skin fail long before the "wimpy" SS screws?

>

>I recall someone doing a write-up on rivet strength in shear,

>and one of the results was that a dimpled skin with a flush

>rivet was much stronger than any other type of rivet, with

>the conclusion that the dimpled skin was carrying load.

>Perhaps someone else knows where to find that report.

>    

>



Bill Marvel's report is at:



http://www.kilohotel.com/rv8/rvlinks/marvelrivets.html



I know there are a number of RVs flying with SS screws instead of AN  

hardware on the fuel tanks, and I haven't heard of any failures yet.   

But that is an experiment that I personally don't want to do.  I'm  

reminded of an Australian P-3 that was subjected to a significant  

overstress.  The aerodynamic loads were high enough that the wing  

leading edges came off the spar, destroying the ability of the wing  

to function, leading to a fatal accident.



SS screws in the tank attachments may work just fine, until the day  

that there is an significant, inadvertent overstress.  Then you could  

discover that the aircraft no longer has the hoped for 1.5 factor of  

safety, as the tanks come off well before the spar fails.



Kevin Horton         RV-8 (finishing kit)

Ottawa, Canada

http://www.kilohotel.com/rv8

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