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Skybolt CLoc Engine Cowling Fasteners

NBowers

Active Member
Fellow RV Builders, if you haven?t already heard the good news, Skybolt has announced a huge 25% promotion on all aircraft cowling kits we have developed over the past 25 years. To kick off our 25th Anniversary, we thought it would be helpful to touch on some of the statements, questions, and responses we?ve accumulated as a company over the past 25 years of working with aircraft/engine cowlings and their fastening systems. So here it goes.

1) Statement: Hinge is less expensive and typically forms a nice seam at the cowling attach points. Response: We won?t argue with this, but we wonder why, in Cessna or Piper's quest to save costs, they didn?t elect to use hinge. Is it because they knew that aircraft would be returning for warranty maintenance costing considerably more than the initial savings? A properly installed series of CLoc fasteners has every bit of "finished" quality as hinge. Many builders will say that they have hundreds of maintenance free hours with hinge. In all of our time spent with our displays at Oshkosh or Sun ?n Fun, we find that the builders that prefer the hinge are becoming a minority. Builders who have used our CLoc systems remain pleased, year after year. We have made huge improvements to the Skybolt 2008 Kits (available now) as far as fastener wear or galling..more information later. We want our fasteners looking new in 2018!

2) Statement: Cowlings using the CLocs bulge. Response: A leftover from earlier days when cowlings were too thin/thick lesser quality fiberglass, and builders did not plan on internal structure to carry the load. For years we supplied a product we called Skybeam with 4" spacing between fasteners. Then, Sam James and Vans began using higher quality materials and provided for the option to use CLocs. To satisfy any question of bulging, we increased the fastener count by decreasing the hole spacing to 3.5", thus eliminating Skybeam and the time to install it.

3) Question: Firewall and/or cowling split support strips - What material should I use? Response: When we originally built our 1st Van's aircraft using Camlocs, we used .063 6061 as support strips and scalloped the strip between fasteners to allow the strip to compound bend. Some builders have successfully used .040 and it seems that the comfort level is .050 6061 material.

4) Statement: Dash 2 studs with SK245-4 receptacles around the firewall. A friend, critic, and confidant claimed that the cowling would actually move under dynamic loads if you utilize floating receptacles in the entire cowling. Response: The definition of move is a debate, but if the theory is of concern, an easy fix to the dynamic load movement is to use SK215-4 (rigid) receptacles along the cowling sides
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5) Question: Are CLocs expensive? Response: Without a doubt, they are more expensive than hinge. They certainly do not have a place in the original cost goal of Vans Aircraft when they set out to design a $17,000 fly-a-way aircraft. Only, I haven?t seen a Vans RV airplane on many flight lines valued less than, maybe $100,000 or more? What is really expensive is a fastening system that is aggravating and has to be fixed or denies us easy access to check important things before we blast off into the yonder.

6) Statement: If Vans intended to use CLocs they would have designed it into the plans in the first place. Are we venturing away from the way the design was meant to be? Refer to item 5).


7) Question: If Vans Aircraft did not design a Camloc cowling, then who did? Response: The basic design has been used for decades on everything from a Navy Corsair to a Cessna or Beechcraft, right up to the A380 and B787. Even better, it is on tons of Vans RV airplanes! What Skybolt did was to adapt the design to the builder market, make it pretty, make it durable, and make every attempt to instruct the user on how to install it. Much of the instruction knowledge we gained came from building and maintaining our own fleet of airplanes and attending Oshkosh and Sun ?n Fun as vendors/instructors and attendees for over 30 years combined. Our face to face exchange of information and hands on demonstrations with thousands of builders is more important than anything that can be attempted over the phone.

For 2008, Vans customers are really going to love what we have improved to reduce galling of the heads through outstanding manufacturing techniques and materials. Finally, Skybolt feels that we have solved 99% of the pitfalls of a fastener designed for a Corsair or a Boeing and made it perfect for your pride and joy Vans RV aircraft. In 2009 you can bet we will improve something yet again.

8) Question: Firewall Kit versus the Complete Kit. Response: We supply, on average 3-4 kits per week to the Vans market. About half of those kits are complete and the other half Firewall only. So many of the ?Firewall only? customers come back and by the Side Kit. The other half of that half regrets that they did not install the complete kit to begin with after 100 hours of flying. It appears that the decision is more monetary than practical, much of the time. Typically, in our response to a customer that is on the fence about the Complete Kit versus the Firewall Kit, we will urge you to purchase the Complete Kit and if in the weeks following you really feel like the hinge method along the sides is calling you home, we will gladly refund the difference between the two kits. In fact, we have never had a customer tell us that they regret installing the Complete Kit. As far as the monetary choice, springing for the extra money for the Complete Kit has never been a regret once that aircraft leaves the ground for the first time. That first flight is so exuberating, the investment that goes into these aircraft becomes overly satisfying.

If you come up with an item 9 or 10, please come forward as these topics help us to help you. You make us better so that we can serve you better. In the mean time, Skybolt is hard at work looking for ways to find that final 1% to be your perfect fastener solution.

80 Knots, Throttle Hold, Engine Instruments Checked...V1,VR,V2...

Respectfully, Ned Bowers - Skybolt
 
Conflicting Instructions for Skybolt C-Loc Fastener Installations

Hi Ned,

Your e-mail post goes into detail about using .063 6061T-6 strips and .050 6061T-6 strips for a typical RV cowling install.

I just purchased one of your fastener kits for my 7A and the instructions supplied recommend .050 2024 T-4 strips. T-4 temper in 2024 is a pretty rare commodity. 2024 T-3 seems to be the norm at most supply houses. Is this an error?

Can you supply the real skinny on the recomended strip size. I have seen some old instructions from SkyBolt detailing an install on an RV-4 and I believe the recomendation is .063 2024T-3. Your competitor Mil Spec also recommends .063 2024T-3 strips.

I think the quality of your fasteners is great, but can you clear up the misleading information concerning mounting strip specs?

Thanks
 
I can?t speak for Ned but, we originally suggested 2024 aluminum in the T3 condition because it is a readily available high strength aluminum with excellent fatigue resistance. However, the drawback is that its corrosion resistance is relatively low. So, it is usually used with an anodized finish or in clad form (?Alclad?), with a thin surface layer of high purity aluminum which of course costs more as a secondary operation.

Now we recommend 6061 (T4 or T6) because it is probably the most versatile aluminum alloy and it is readily available. It offers a wide range of mechanical properties and the T4 condition allows for fairly severe forming operations. Plus, 6061 offers much better corrosion resistance without anodizing. If you want to use the T6 condition for added strength that is fine it just requires a little larger bend radius when forming. In the RV cowl application that is not a concern. Also, if you don?t mind the extra expense, it is available in the ?Alclad? form to further improve the appearance and corrosion resistance.

The thickness of .062? was originally recommended but, we subsequently found that strips as thin as .040? were adequate, easier to work with and less expensive. We settled on .050?. Hope this helps. I will update our instructions ASAP.

Best,
Jeremy
MilSpec
 
Skybolt C-Loc Engine Cowling Fasteners

Thanks Jeremy,

I appreciate a MilSpec rep weighing in on this. It says alot about your customer service ethic . I have yet to hear from Skybolt, and I purchased their fasteners.

I have already purchased a piece of 063 2024-T3. It was based on my best guess on the infornmation I had pulled from old Skybolt instructions and current and MilSpec instrucions. It sounds like it will be adequate as long as I protect the strips from corrosion.

The important thing I would like to request is that all vendors offering products for the experimental market should remember that most builders do read instructions. These instructions should be accurate and current as most of us rely on the manufacturer as the best source of information for their products.

Thanks again for your help!!!
 
The important thing I would like to request is that all vendors offering products for the experimental market should remember that most builders do read instructions. These instructions should be accurate and current as most of us rely on the manufacturer as the best source of information for their products.


And MilSpec has done just that.

RV Installation Instructions

-Jeff
 
2024-T3 is usually Alclad.

......
I have already purchased a piece of 063 2024-T3. It was based on my best guess on the infornmation I had pulled from old Skybolt instructions and current and MilSpec instrucions. It sounds like it will be adequate as long as I protect the strips from corrosion.
......

Ted... check your aluminum... If it came from Aircraft Spruce, then they only sell 2024-T3 as Alclad. It's the 6061 stuff they sell non-clad. I think most other vendors are similar....

Jeremy's post seems to imply the the 2024 Alclad is an extra step... if the material comes that way (i.e. Alclad), it is a stronger material than the 6061, and is probably more corrosion resistant than the "bare" 6061... use what you have... it's better...:)

The posting is a little confusing...

gil A
 
Thanks for the clarification Gil, you are absolutely correct. Most vendors do sell 2024 as Alclad because of the inherent corrosion characteristics of the alloy. It?s just an extra step at the mill that is rolled into the cost to the distributor and therefore to the end user. Ted, if you are still concerned, just contact the supplier and they should be able to easily pull the mill test reports and verify if your particular lot was Alclad or bare. My bet is that you are just fine with the 2024 you already have because as Gil says, it is most likely Alclad and there would be no need to start over. I apologize if my post was confusing or vague. I guess I?ve just been in the metal fab biz too long. My ?suggestion? is to use 6061-T6 mounting strips with proper metal prep because the 6061 in the T6 condition is just as strong as 2024 in the T3 condition without the extra expense of Alclad. Some builders will have a different opinion and that?s O.K. There are options in this aspect of the build just as there are in many other facets. Just my $0.02.:)

Best,
Jer
MilSpec
 
2024-T3 is stronger....

....... My “suggestion” is to use 6061-T6 mounting strips with proper metal prep because the 6061 in the T6 condition is just as strong as 2024 in the T3 condition without the extra expense of Alclad. ....
Jer
MilSpec

Jer... not quite....

2024-T3 Alclad -- Tensile 65/45 ksi-Ultimate/Yield -- 40 ksi-Ultimate Shear

6061-T6 bare -- Tensile 45/40 ksi-Ultimate/Yield -- 30 ksi-Ultimate Shear


Since most builders just buy from the usual suppliers, with a limited choice, the Alclad 2024-T3 is still the strongest, and easy to obtain - isn't that why we use it for our skins and bulkheads...:)

...data here...

http://www.transtarmetals.com/zcSite/Transtar/public/Forms/typprop.pdf

Stick with the aircraft quality stuff...:)
There's a good reason the 6061-T6 stuff is cheaper...
For this specific application - holding the cowl on to the fuselage - I think the stronger, more corrosion resistant material would be the correct choice....

gil A
 
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You can make the strips from which ever you prefer but, the cowling fasteners themselves would be long gone before they saw 30 KSI.

Jer
 
Upper Firewall Skybolt or Milspec Fasteners Installation on RV-7

Thanks fellas for the metallurgy class. 063. 2024 t-3 it is....This forum is great!

Does anyone have any photos detailing a upper firewall only C-Loc installation on a RV-7 with the stock standard hinge fasteners on the side of the firewall and cowling seam?

I would like to space my fasteners so the first one is located about 1 1/2" above the hinge that joins the upper and lower cowling. This insures that the cowling will be fastened a little better than the stock upper hinge install which ends at the bend line.

Skybolt recommends doing this but their installation instructions show the install on an RV-8 which I believe has a flat firewall.

The RV-7 (and RV-6) has a pronounced horizontal bend line in the upper firewall just above the upper motor mount attachment that complicates the installation of the aluminum strip for the fasteners. I can either plan to cut the strip at the bend line and install a separate strip on the side of the firewall from the bend line to the cowling hinge or do some really fancy cutting of the strip to maintain a constant dimension for the recommended width of the strip.

I have looked at my collection of photos of completed RV-7s that had C-Loc fasteners along the upper cowl only and I have seen buliders locate a C-Loc at this location. Just curious as to how others handled this.

Thanks for your help!
 
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Mounting strip materials

Sorry for lying off for a few days to reply to the question of mounting strip material (I was doing my annual recurrent for DAL).

The 6061-T6 (.063) strip was what we originally used in the 1st RV4 Skybolt built. The reason this was used is simple: It was the material strip we had and we chose to be very conservative with .063. Since that project, we have had great success with .040 and .050 and recommend .050 for firewall and side mounting strips. The science of 6061 versus 2024 came after our original kits we developed in 1990. 6061 is OK; 2024 seems to be better and agrees with AC43.13 "Aircraft Inspection and Repair". Standard MS20257 Hinge in 5052-34 material is rated at 34/20 compared to Alclad 2024-T3 at 59/38 tension/Shear; T4 is 58/35. If we were to debate material based on strength values, all the above references have obvious advantages. The most important criteria I find in the fastener world (working on tons of Cessna cowlings, for instance), is work hardening or stress corrosion. This is where higher strength values may not necessarily be your best friend. 6061 is a good material, but in some cases, it will stress crack and in others, it won't. Skybolt manufactures formed fastener components with all the materials mentioned with various results. For a cowling application, I'll go with Gil Alexander's reply and state that 2024-T3 Alclad is the best choice for firewall and side mounting strip applications although I am not aware of problems with the other referenced materials or thicknesses (6061, 2024-T3 or T4, .040, .050, .061....Alclad, non-Alclad; we have used all of them successfully, including fiberglass and composites that we fabricated as doubler/mounting strips).

The current Skybolt Vans RV PowerPoint instructions state 2024-T4, however, I am adding a note to the instructions to also recommend 2024-T3 Alclad.

On another note, the trademark CLoc and name C-LOCK are used in passing as if they are the same. These fasteners are not the same. In fact, they do not even look the same. All of our current kits use the Skybolt CLoc 4000 Super Series studs that have a standard #2 Phillips aviation head. The "Super" means that we found ways to boost the head hardness significantly to prevent screwdriver galling without compromising corrosion resistance. (Camloc uses a 400 Series stainless to do this, but it is not shiny and will corrode). Add up all the differences Skybolt has engineered into our newest 2008 CLoc brand and you have a stainless fastener that will outlast, outshine, and out perform anything available from any other source by a significant margin. We want the CLoc fastener to look as good in 1000 hours as the day you installed them.

Thanks to all for their input...it allows us to see many points of view and to serve you better.

Ned Bowers
 
Hi Ned,

Your e-mail post goes into detail about using .063 6061T-6 strips and .050 6061T-6 strips for a typical RV cowling install.

I just purchased one of your fastener kits for my 7A and the instructions supplied recommend .050 2024 T-4 strips. T-4 temper in 2024 is a pretty rare commodity. 2024 T-3 seems to be the norm at most supply houses. Is this an error?

Can you supply the real skinny on the recomended strip size. I have seen some old instructions from SkyBolt detailing an install on an RV-4 and I believe the recomendation is .063 2024T-3. Your competitor Mil Spec also recommends .063 2024T-3 strips.

I think the quality of your fasteners is great, but can you clear up the misleading information concerning mounting strip specs?

Thanks

Hi Ted:

The .063 6061 is what we used in our original Vans RV4, as it was the material we had on hand.

In one of our projects, I used .050 2024-T4 as it was available from our local source, however, for this application, 2024-T3 is a better substitute if availability is the driving issue. We will add a note to our instructions that states several alloys, Alclad and non-Alclad, including composite fabricated parts are acceptable alternatives for mounting strips. The strength factor is somewhat of a non-issue, as most aluminum alloys exceed that of the hinge it is replacing and exceeds the tensile strength of the fastener itself considering converting PSI load to straight load. I totally agree that the instructions need to be clear and concise, and I like you, hate reading computer manuals when they leave out one simple keystroke the author just assumed I'm supposed to know. I try to rely on pictures to tell a thousand words. But nothing beats many of the photos available on the Vans AirForce website, I believe are posted on this forum that should answer your question. If not, let me know and I'll send you a disk from my library. One neat thing about the kitplane industry, there are many ways to skin a cat and just when I thought I've seen the perfect answer, someone comes up with another clever version and we are free to adapt. Every time I get near to publishing a drawing, I see something I like better and revert back to a picture. The good news is, I have yet to see an installation that is not structurally sound.

Thanks Ted,

Ned Bowers, Skybolt
 
Where to buy 2024-t3 for this?

So it looks like I'll need about 3' by 3" of .050 2024-t3 for my upper firewall project, but Spruce will only sell me a 4' by 2'. Where do people get such small pieces?
 
Piano hinges?

Will be starting my cowling shortly and I know this is about Cloc fasteners, but what is wrong with the standard piano hinges? Generally I don't look too far ahead into my -7 project so I research about 2 months ahead to keep from mental overload.
 
Here's my two cents: I had planned from the start to use hinges cuz they're clean, cheap and light. Now that I'm nearly done with the cowl, I've decided that the hinge across the top of the firewall has got to go. The idea of reaching through the oil door across the top of a hot dirty engine every time I need to look at something I can't live with. I don't want to ever have a reason not to open things up if I suspect a problem. The other hinges seem real good. This may be different for the other models that have bigger, floppier cowls.
 
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