Skybolt CLoc Engine Cowling Fasteners

[NBowers]

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

[Tedtheflyer]

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

[Thatchman]

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

[Tedtheflyer]

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!!!

[RV_7A]

Originally Posted by Tedtheflyer

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

[az_gila]

Originally Posted by Tedtheflyer

......
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

[Thatchman]

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

[az_gila]

Originally Posted by Thatchman

....... 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...ms/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

[Thatchman]

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

[Tedtheflyer]

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!