[Mark Bolton]

I hope this is not posted in the wrong spot since it is not model specific but rather a general firewall forward topic.

I am building an RV 4 and there has been some discussion about using twist / lock style fasteners to hold the cowls onto the firewall instead of the fairly awkward piano hinge / bent hinge pin method. This is not specific to RV 4 but the bends are tighter so it is that much more difficult.

Has any one tried this ?

I would expect a considerable amount of reinforcement would be needed along the screw line / frire wall - probably a strip of Aluminium glued to the fibreglass with Proseal (or Sikaflex).

What amount of fastener spacing would be best ?

I hasten to add I wouldnt comtemplate using this method to hold the top / bottom halves together the pin method works just fine and probably has better structural integrity.

Thank you in anticipation of your replies.

Regards

Mark Bolton

 

[frazitl]

I used Milspec

quarter turn fasteners on my 7A firewall (see: http://www.milspecproducts.com/KITPLANES.htm#vans) and very happy I did. I used the standard hinges along the top and bottom split. Philips heads seem easy to use without slipping and gouging the fiberglass.

The 1/4 turn fasteners require a flange riveted to the inside of the existing firewall and skin flange that faces forward. I made mine from six pieces of .063" 2024t3 about 1 1/2" wide. The top and bottom pieces on each side included the curves around the firewall with short straight sections on each side. Be sure you plan to have the cowl split not line up with a split in the .063 firewall flange.

Simple instructions come with the Milspec kits. It's not hard, just a little tedious to get a good fit (just like the rest of the project).

Good Luck!

 

[Ironflight]

Do a forum search for "Milspec" or "Camloc", and you'll find dozens of threads, hundreds of pictures, and detailed accounts of how people have installed these instead of hinges. this is an extremely common modification!

Paul

 

[breister]

Yep, I wish the builder of my plane had used MilSpec - having to match the "correct" fastener to it's hole is a PITA. The MilSpec ones have adjustable receptacles, so all the fasteners can be the same length.

 

[Snowflake]

Philips heads seem easy to use without slipping and gouging the fiberglass.

I'm fairly certain that you'll be cursing those Phillips heads a few years from now. I have yet to see a Philips head screw that gets regular use that isn't stripped out.

Someone on the RV-lists a while ago arranged for Southco to make Torx-headed 1/4-turn fasteners... I can't find the thread right now, but you could look into that as an alternative. Or you might be able to find some with a Robertson head (square) instead. Either would greatly reduce the tendency of the screwdriver to cam out of the head of the screw and leave a nice mark/scratch/dent on your paint.

 

[tommylewis]

mil spec here

I have Mil Spec Phillips head "camlocs" on my RV7a. I used them on the entire cowl, no pins anywhere. I have 650 hours and 2.5 years on the RV7a and am very happy with my decision. The following picture shows them.

 

[flion]

I'm fairly certain that you'll be cursing those Phillips heads a few years from now. I have yet to see a Philips head screw that gets regular use that isn't stripped out.

These aren't screws and, if adjusted and used properly, I would be very surprised to see them get stripped. There is not nearly the torque required to use them as there is on a structural screw.

 

[Snowflake]

These aren't screws and, if adjusted and used properly, I would be very surprised to see them get stripped. There is not nearly the torque required to use them as there is on a structural screw.

Sorry, I wasn't very clear... I wasn't referring to any threads, I was referring to the heads themselves. Phillips heads are virtually designed to cam the screwdriver tip out of the screw when you're trying to tighten them.

As long as the fit of your cowling remains close to perfect, and you don't need a lot of pressure or torque to get the screws to turn beyond the camlocks, you might be fine. But you'll want to be more careful as parts age and start to not fit as well as they used to.

 

[GAHco]

Not the good ones!

Sorry, I wasn't very clear... I wasn't referring to any threads, I was referring to the heads themselves. Phillips heads are virtually designed to cam the screwdriver tip out of the screw when you're trying to tighten them.

As long as the fit of your cowling remains close to perfect, and you don't need a lot of pressure or torque to get the screws to turn beyond the camlocks, you might be fine. But you'll want to be more careful as parts age and start to not fit as well as they used to.

I sell many different sizes and styles of Phillips and other bits made by Zephyr tools, they work well and do not wear the recess's out, if you start with good ones in the first place a Phillips bit made to mil-specs, its a beautiful thing Available in small or large qty's

Ref Book Page http://www.gen-aircraft-hardware.com/images/pdf/zephyr-bits.pdf

Purchase Link http://www.gen-aircraft-hardware.com/store.asp?alternate=D1222AA

Let me know how they work out?

 

[Kyle Boatright]

I'm fairly certain that you'll be cursing those Phillips heads a few years from now. I have yet to see a Philips head screw that gets regular use that isn't stripped out.

That's why I buy 'em 100 at a time from Aircraft Spruce. When one gets worn, I toss it and grab a shiny new one. I usually replace about half of 'em every time I do a condition inspection. At $0.05 each, I'd have to live to be 100 for the screws to cost more than camlocks would have.