Piano Hinge vs. 1/4 Turn Fasteners for Cowl

[Steve Ashby]

I have been pondering the manner in which I will affix my cowling to my firewall. What are the pros and cons of the piano hinge vs the 1/4 turn fasteners? What say you flyers?

[Mel]

Piano hinge works great for the vertical between the lower cowl and firewall, and the horizontal between the upper and lower cowl. Across the upper cowl to firewall, they work OK but are often difficult to install and remove. Hinges don't work well at the lower cowl to firewall. The pressure and vibration tend to break off the hinge eyes over time. The same between the upper and lower cowl at the spinner. Most people use screws or quarter turns here.

[Dean Pichon]

My -4 has been flying with hinges for about 6 years. To date, I have broken 3-4 eyelets and will soon ground the plane to switch from hinges to 1/4-turn fasteners.

The broken eyelets are along the horizontal hinge sections between the upper and lower cowl halves and between the firewall and upper cowl. So far I have not seen any damage to the vertical sections attaching the lower cowl to the firewall. I hope to have better luck with the 1/4-turn fasteners.

Regards,
Dean Pichon
Bolton, MA
RV-4
375 hrs

[RV7ator]

1/4s on the upper cowl-firewall for sure. Besides broken hinge eyes, it's often a two-man job to get the mess aligned to drive in the pin, perhaps over a hot engine to boot.

JOhn Siebold
Boise, ID

[Ironflight]

I'm using the piano hinges all around, and have not had any significant problems yet....515 hours, about 1.7 years of flying. I think I have one hinge eye on each side on the lower (short horizontal) fasteners that might be thinking about giving up. One nice thing is that with age, the hinges are easier and easier to install - obviously some wear occurs between the pins and the hinge eyes.

The hinges across the top/rear of the upper cowl take some fiddling to get right, and yes, if you have to remove the cowl with the engine hot, it is a good idea to have a long sleeve shirt - there are warm pieces of metal in there!

I think that the 1/4 turn fasteners are a good solution, and considered them briefly, but decided to go with Van's solution to start (there are an awful lot of RV's flying with the hinges!), and knew that I could change later if I needed to. Haven't had a reason to change yet, and the "fastener-less" appearing cowl does get compliments!

Either way works - just make sure that if you go with hinges that you try minimize residual forces in the system - in other words, the hinge pins shouldn't force or pull things into alignment (too much) - the hinges pretty much align naturally, or you're just asking for wear and breakage.

Paul

[MSFT-1]

When it was new they were a bear to get in and out. As I learned the technique and the airplane "loosened up" they became much easier to work with. I still always thought about converting to 1/4 turn fasteners until I asked a guy with them on his RV-8 and he said he hated them. He says he may even convert over to the hinges.

I have an eyelet on each side across the bottom that are broken.

So I guess that is one vote for hinges.



Bruce
N297NW
RV-8 (458 TT)

[n5lp]

I started with hinges everywhere except at the top and by the spinner. The bottom hinges broke in something like 10 hours. The side hinges probably lasted around 30 or 40 hours. The hinges that join the top cowl to the bottom cowl didn't start breaking until around 850 hours when they started breaking one by one on one side only, starting at the front. Except for the top to bottom cowl hinges, I replaced them all with screws into nutplates as they broke. I used too many screws and they are a pain to remove and replace, but nothing has broken on them.

By the spinner I started with screws into aluminum plates and switched to steel plates when the aluminum ones broke at 150 hours or so.

I know most people have way better luck with hinges than me, and they are also probably way better builders but that is one of the few things I would do differently if I knew then what I know now, there wouldn't be any cowling hinges on my airplane.

[robertahegy]

I have the hinges all around per the plans on my 7A. No problems and very easy to remove and replace.

Roberta

[Walt]

I have hinges all around except on the bottom. Easy to install and look better IMO. 2.5 yrs, 550+hrs no problems at all.

[gpiney]

The piano hinge Vans supplies is the inexpensive 'rolled' aluminum hinge. If you are worried about longevity, go to Wicks or ACS and order the appropriate amount of 'Extruded' piano hinge. The cost is about 2.5-3 times more expensive than the rolled stuff. Probably last 5-10 times longer.