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2thman(at)cablespeed.com
Guest

Posted: Fri Feb 15, 2008 6:06 pm Post subject: Cowl Fasteners

Sending this a second time - didn't see it come up yesterday.  I apologize

to all if it's redundant.



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Mark Phillips in TN

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

Posted: Fri Feb 15, 2008 9:27 pm Post subject: Cowl Fasteners

In a message dated 02/15/2008 8:08:16 PM Central Standard Time, 2thman(at)cablespeed.com writes:

  	  Quote: 	
		  So almost all of us on that list agree that hinges are the better way to go. 	


 Hi John-

  

 I conditionally respect your attempt to promote your product here- wish I had something to sell as well!  I am confident they are well engineered products and meet the needs of suitable builders.  I must admit I looked at carbinge while constructing my RV, but considering my limited budget, opted to use the standard hinges supplied with my kit.  Appropriately applied, they have worked quite to my satisfaction.  The use of screws on the bottom cowl to firewall addresses a common problem with use of aluminum hinge in this area, and it has worked flawlessly for me.  My upper/lower hinge pins insert quite easily through the firewall- no retention problems and no exposed fasteners, nor any possibility of prop interference.  No failures in 450+ hours of use kinda negates some of your suggested difficulties using cheap old aluminum hinges and screws.

  

 "weight, difficulty of installation, dinging up the cowling when removing and replacing cowl, appearance, frictional drag and so on."

  

 Huh?  And just what the heck are "rivet divots"?  No idea what you're talking about.  Neat thing about the Experimental family- use common sense selecting products that suit your needs, do what you think is best and let the results speak for themselves...

  

 Amazing variety of fine feline pelts, no?

  

 Mark Phillips, Columbia, TN

 Builder RV-6A "Mojo"- earned Bronze Lindy OSH '05, Sun&Fun Best Metal Homebuilt '06, Grand Champion SERFI '06

 http://websites.expercraft.com/n51pw/

 do not archive



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  [quote][b]

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_________________
From The PossumWorks...

2thman(at)cablespeed.com
Guest

Posted: Sat Feb 16, 2008 8:31 am Post subject: Cowl Fasteners

Mark writes:  Huh?  And just what the heck are "rivet divots"?  No idea what

you're talking 

about.  Neat thing about the Experimental family- use common sense selecting



products that suit your needs, do what you think is best and let the results



speak for themselves...

*********************

I'm referring to the little dimples that either are immediately apparent in

the paint job where rivets were placed or that show up later after vibration

and working cause them to pull the paint layer back and forth a little.



Please understand the comments about breakage, fingers getting damaged etc

with metal hinges didn't come from me - those comments were offered by

another builder on the RV List and I was referring to those.  



Agreed that metal hinges can and will work OK and certainly at the front end

they cost less.  However, we do hear about the corrosion and breakdown of

aluminum hinges a good bit on the Lancair Mail List so there is reason to

consider that aspect.  Sometimes there are black streaks that come out of

aluminum hinges on aircraft.  That streak is the result of oxidation turning

to powder, getting mixed with water and running out of the hinge joint onto

the paint surrounding.  We have quite a few reports of hinges wearing out on

homebuilts to the extent that builders need to replace or try to insert a

Teflon sleeve over the pin to get more service life out of the hinge.  Also

there are credible reports of the attachments working loose over time where

rivets are used to attach aluminum hinges to composite.  Perhaps those

builders were not as accomplished as some, but it is fact that two

dissimilar materials like aluminum and composite mechanically joined with a

long joint will work and expand/contract at different rates during thermal

and vibrational cycles.  This activity tends to stretch and wear the

attachment points and can and does lead to loss of the integrity of the

attachment.  



Regards,



John Barrett, CEO

Leading Edge Composites

PO Box 428

Port Hadlock, WA 98339

www.carbinge.com

  



7:08 PM

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Mark Phillips in TN

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

Posted: Sat Feb 16, 2008 8:19 pm Post subject: Cowl Fasteners

In a message dated 02/16/2008 10:33:36 AM Central Standard Time, 2thman(at)cablespeed.com writes:

  	  Quote: 	
		  I'm referring to the little dimples that either are immediately apparent in

the paint job where rivets were placed or that show up later after vibration

and working cause them to pull the paint layer back and forth a little. 	


 >>>

 Ahhhh!  I can certainly see how that could happen, and wished to avoid it when building my plane.  I'd heard about the following technique from the RV-list (circa 2001-2002?) before tackling any hinge attachment to fiberglass- the application is shown here:

  

 http://websites.expercraft.com/n51pw/index.php?q=log_entry&log_id=23983

  

 Not to say there isn't a superior method, and don't recall who the original advocate was, but it sho 'nuff works.

  

 I surmise the reason Lancairs have this "problem" is airflow/skin friction heating resulting in unven expansion of rivets and composite materials causing the separation around the rivet heads?

  

 

  

 Mark

 do not archive



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_________________
From The PossumWorks...

2thman(at)cablespeed.com
Guest

Posted: Sun Feb 17, 2008 7:55 am Post subject: Cowl Fasteners

Mark writes:



_http://websites.expercraft.com/n51pw/index.php?q=log_entry&log_id 3983_

(http://websites.expercraft.com/n51pw/index.php?q=log_entry&log_id 3983) 



Not to say there isn't a superior method, and don't recall who the original

advocate was, but it sho 'nuff works.



I surmise the reason Lancairs have this "problem" is airflow/skin friction

heating resulting in unven expansion of rivets and composite materials

causing



the separation around the rivet heads?







********************** 



Mark



That's an interesting technique for hiding rivet dimples (or divots) I just

kind of like the sound of "rivet divots".  I had not seen that before.  Some

builders add a layer of very fine glass over the line of rivets and I think

they report that does the trick.  With the Lancairs, there are quite a few

areas where countersunk screws reside on the outside skin leaving a similar

conundrum.  I think most builders add the thin layer of glass over those

prior to body work to keep them from dimpling. It probably would help in the

situation we're discussing.



I don't think it's so much friction in the air stream causing the thermal

cycling but that might have an effect, and it does remind me of an incident

in the 1960's when I was flying one of the Navy's training jets - an F9

Cougar.  I was out playing and I put the aircraft in a vertical dive for the

purpose of catching and passing a buddy who didn't know I was several

thousand feet higher and behind him.  The victory roll I did right off his

nose surprised him and put a grin on both our faces, but I had the airspeed

to VNE - about 400 knots as I recall. The F9 had countersunk phillips head

screws on the wing surfaces and during my post flight inspection I

discovered that the paint in the screw heads was peeling out of the grooves.

I remember it well because I worried for days that the plane captain would

do a thorough post flight inspection and report it as a discrepancy.

Fortunately for me, I didn't get caught.  I have no idea whether that

peeling was caused by pure friction or if heat was a factor in softening the

paint so that the thermal and mechanical effects combined to create the

result.  After consideration, I'd surmise the combined effect is the more

reasonable conclusion.



I think the major cause of thermal cycling in our airplanes is rather the

difference in OAT from sea level to 25,000 feet.  And the thermal cycles

just from sea level to 10,000 or 12,000 feet can be significant.  I think

this plus the vibration is what causes these joints between dissimilar

materials to work back and forth and often bring about early failure after a

few hundred hours of service.



Regards,



John Barrett, CEO

Leading Edge Composites

PO Box 428

Port Hadlock, WA 98339

www.carbinge.com

  



2:16 PM

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martin(at)gbonline.com
Guest

Posted: Tue Feb 19, 2008 7:14 am Post subject: Cowl Fasteners

Robin et.al.

 I now have 1600 hours on my RV8 with the Sky Bolt  Stainless fasteners and adjustable receptacles..  When I built my RV8   10 years ago the Skybolt fasteners were just coming on the market.  The  regular fasteners available at that time were all to long for the limited  clearance and also thin top cowl that Van supplies.  At that time I became  acquainted with the  owners of Skybolt and advised them of my  requirements.  They then designed  an extra short fastener ( number 0)  and  a adjustable receptacle  that would clear the engine.  I  have never had a problem with the fasteners or the Skybolt people.  They  have been honest and prompt with delivery.  Good luck with your  project.

 Dick Martin

 RV8 N233M

 the fast one

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robin1(at)mrmoisture.com
Guest

Posted: Tue Feb 19, 2008 9:36 am Post subject: Cowl Fasteners

[quote]Thanks Dick,               I had initially decided to use the Skybolts on only the upper firewall and the underside of the bottom cowl (SJ Cowl). Since then I purchased a complete set to connect the upper & lower cowl too. I prefer the clean look of the wire but the SB’s with the really nice backing strip are too good a combination.                I have to say however for the budget minded builder a simple solution are $0.05 S/S machine screws and countersunk washers. My RV-6A has a full set (only wire is on the sides of the lower cowl) and this looks good, works great and can be replaced any place there is a hardware store. I also think the S/S screw set up is a lot lighter.  RobinRV-4       SoldRV-6A    450 HoursRV-10     Panel this week???Do Not Archive[b]

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