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Screws vs quarter turn fasteners around the firewall

UnPossible

Well Known Member
Hey -

I am making good progress on my 10, and am looking ahead to working on the cowling. I am not a big fan of Van's hinges around the firewall, and on my 7A I used quarter turn fasteners all the way around the firewall. However on my 10, I am considering just using screws and nut plates. Why????

1) Price... I think the firewall kit fastener kit is around $500.... screws and nut plates would likely be $25 or less.

2) Putting the cowling on and off is a bit of a pain. The quarter turn fasteners hang down from the cowling and can scratch the paint if you aren't really careful getting everything aligned before setting the cowling down into position.

3) Long term maintenance... I have had to replace a couple of the quarter turn fasteners (which were replaced under warranty) when they failed to lock into place. Additionally, I have a couple of them that don't want to stay in the cowling when unlocked.

4) Speed... while the quarter turn fasteners are going to be faster... using a screw gun I can't imagine the time difference being all that much.

Is there some reason I am not thinking of why I shouldn't go ahead with screws and nut plates?

Thanks,
Jason
 
I used the 1/4 turn fasteners. I would use screws if I built again for all the reasons you mentioned.
 
Some people complain about the longevity of the standard hinges.
Keep in mind that the threads on screws are like saw teeth to fiberglass.
With vibration, plain screws can make a mess of a cowl over time.
If you do decide to go with screws you should use ones that have some smooth shank (like AN509 or AN525).
Using a flush screw with a tinnerman washer can be beneficial because of the increased baring area provided by the countersink.
The main down side in my opinion, even if you do these things to mitigate the screws causing wear in the hole, is that with the custom paint jobs done now a days, it is common for the paint or clear coat to migrate out from under the screws over time.
 
I used -8 screws on my 8, and after 3 years they look like the day I put them in. I've won a few bets; I can remove or install the upper or lower cowls in less than 2 minutes each.

I also removed the hinge pins on my 9A, and replaced with -8 screws. I use the Bosch gyroscopic screwdriver from Home Depot. 'Wont leave home without it'

Roger Bloomfield
KAEJ Buena Vista 8,000 MSL
 
I used screws across the top and bottom of the cowl on my -6. I reinforced both flanges on the cowl with extra layers of fiberglass. That system has been faultless for ~18 years.

I went with quarter turns on the -10 and wish I hadn't. They are expensive, harder to install, and there are probably other issues I don't know of right now.
 
I used the 1/4 turn fasteners. I would use screws if I built again for all the reasons you mentioned.

I agree. I would just go with screws and nutplates if I were doing my rocket cowling over. Camlocs are nice, don't get me wrong but its not that much more work to use a cordless drill.
 
Hinge pins here for the last 15 years, work like a dream, super easy to remove/install cowls. I used screws on the bottom of the cowl and on the front only. Would do the same again if I was to build another.
Oh yea forgot the most important part... they look good!
 
My Cessna has screws. There has to be a pretty good reason to take that cowling off.

My Dad's RV has skybolts. I will pop that thing off for hardly any reason at all.

I would do the quarter turns, if for no other reason it takes away one more excuse to have a looksee under the hood. In the grand scheme of things it's probably not much more time, but psychologically those screws are a pain in the behind.

DEM
 
No screws! On my RV-8, due to the curvature of the cowling, the quarter turn fasteners were installed without the retaining rings to those were removed for cowling removal -- no paint scratching.

Screw heads can get damaged over time, screws have been known to break, etc.

YMMV

Ed
 
1/4 turn

I've had my cowling on and off what seems like 100 times during the build and engine installation..... SO GLAD I went with 1/4 turn fasteners.

I too, do not use the retaining rings... but instead treat the 1/4 turn fasteners as screws (put them in pocket or bag as they are removed).
 
No screws! On my RV-8, due to the curvature of the cowling, the quarter turn fasteners were installed without the retaining rings to those were removed for cowling removal -- no paint scratching.

Screw heads can get damaged over time, screws have been known to break, etc.

YMMV

Ed

My cowl is the same. The bottom four ? fasteners on each side do not have the rings and pull out. Eliminates the scratching issue.
 
My last plane, a 6a, had screws around the top cowl. Decided that the next would have 1/4 turn fasteners. The problem wasn't a time issue, it was trying to collect all the screws/tinnerman washers without dropping them, and one or two needed to be replaced just about every time the cowl was off. Oh, and inevitably I'd go looking for the screw gun and it would be at home for some reason....

Hinges along the sides, and (retained) skybolts over the top for me.
 
Cowling

Phillips head camlocs. Won?t regret it.
At night when you hear the funny noise
Crossing the desert or mountains
And you did not want to take the
Time to unscrew the Cowling to be sure. ?
 
My 1958 Cessna has screws and they still hold the cowling together after what must have been hundreds if not thousands of cowl removals and installs. with an electric screw driver it is no problem.
 
My 1955 Cessna has screws. Over time, the holes in the cowl have gradually enlarged, so the recommendation for the Tinnerman recessed washers is a good one. Every once in a while I need to replace one of the Tinnerman nuts (a nutplate will also sometimes wear out) and at least those didn't need riveting.

Installing or removing the cowl is a pain. There are enough screws that it takes a little bit of time. The Cessna has a 6 cylinder Continental, so its cowl is about the size of an RV-10s.

Before he moved it, an RV-8 was in the hangar next door to mine. It used the stock hinges. He had enormous trouble reinstalling his hinge pins, but I don't know why. That made such an impression that I bought a set of the Mil Spec 1/4 fasteners for my RV-3B project.

Dave
 
Love the SkyBolts. Used them around the firewall perimeter, and hinges for the upper/lower cowl joint. The biggest advantage is that the screws are captive in the bezels, and you never have to worry about a mucked-up nut plate. And on a purely aerospace-is-cool note, these suckers are used on the ISS! :D

Scratches have never been a problem on the paint. They do scratch up the receptacle mounting plates, but they're bare aluminum and, of course, hidden when the cowling is fitted.
 
Hinge pins here for the last 15 years, work like a dream, super easy to remove/install cowls. I used screws on the bottom of the cowl and on the front only. Would do the same again if I was to build another.
Oh yea forgot the most important part... they look good!

What Walt said!

The Doll's first flight was 19 years ago this week. My pins and hinges are original and still working great. On the bottom of the cowl on each side to the air ramp I used three #8 button head screws. I used 8 counter sink screws as per plans in the front behind the spinner. When installed correctly, they are easy in, and out. Everything you need comes with the kit at no extra charge.
 
I?m not at that point in the build yet, but I?m planning on SkyBolt quarter turns on the top cowling at the firewall and piano hinges everywhere else. On my first build I used the quarter turns everywhere on the cowling, but I wouldn?t do that again.
 
I'm doing Skybolts on the top cowl/firewall intersection and along the upper and lower cowl seam (horizontal). Using the hinges on the lower cowl.

I took the screws out of my grandfathers 170 and 172's enough times (manual) screwdriver) that I am looking forward to the sky bolts. Over time the holes seemd to enlarge and the nut plates would strip- I grew to hate them.

We used to use Dzus fastners in the racing applications so I have a fondness for the 1/4 turn stuff I guess.
 
Where do you put the nut plates?

Hi All,

Am building a 10 and am ready to fit the cowl soon

What do you attach the nut plates to if using screws?

Thanks

Amer
 
to use the 1/4 turn fasteners an alum tab, .040-.062 is fastened to inside of one cowl half. fastener is riveted to the tab. tab is fastened to cowl half by countersunk solid rivets . countersink a little deep and they fill and sand nicely.
in less than flat places tab may need to be bent/ twisted a bit so it fits flat against both cowl pieces.
 
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