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bottom cowl hinge pin - from side?

blaplante

blaplante

Well Known Member
This past weekend I was under the RV6A under construction and was trying to install the lower cowl bottom hinge pins for the first time after installing the hinges to the cowl. What a pain! As I'm lying on the creeper under the plane I'm thinking ... but this is so much better than lying in oil and gravel at Podunk International. Gotta be a better way.

Question - has anyone tried using the hinge pins - but installing them from the side inward rather than the center outward? It looks to me like the hole would be low on the side, well into the rounded area, and the pin could fold under the outside of the cowl. Ok, points lost for having the pin end hanging 1/8" into the airstream (but is it any worse than the original design of the side cowl pins?). It wouldn't be very noticeable as you stood near the plane. Did searches and didn't find any examples.

Of course, my other option would be to take this all out and put in some more 1/4 turn fasteners...

Thanks!
 
They would probably be covered by the upper intersection fairings....

Most people seem to have eyelets from the hinge break by the middle of the cowling where you are trying to currently insert the pins. I would recommend replacing the hinge with a piece of .063 and nutplates/1/4 turns fasteners etc.
 
blaplante said:
Question - has anyone tried using the hinge pins - but installing them from the side inward rather than the center outward?
Click to expand...

They get easier to install after it's flown a bit. Besides, in order to remove the cowl, you're going to be down under there anyway since you need to loosen a couple of bolts and remove U-621. This bracket is also what retains the pins, so you'd need to come up with your own way of doing that as well. Given this, I don't see much benefit to having the pins come out the side.

crabandy said:
They would probably be covered by the upper intersection fairings....
Click to expand...

Not on an RV-6A they wouldn't - no intersection fairings there on nosedraggers.
 
I do it this way

On my -6A, I have the bottom hinge pins exiting out the side. There is about 1/2" section with a 90-deg bend to help hold the hinge pin in

To hold the hinge pin during normal operation, I cut a single eyelet section of the hinge. Drilled a hole for a #8 screw. Put a to nut in the side to accept the screw.

Slip the eyelet bracket offer the 1/2" section plod hinge pin and screw the bracket into the rivit on the side.

I don't need to crawl under the plan to remove my cowling.

Very easy.
 
Get a scrap of carpet to throw under the plane and lay on when you need to decowl.
 
I don't use the center bracket. I have not had any issues with the rivits poping out of the hinges.

For the faring. I have a tab that tucks into the lower cowl and a single screw that can be reached from the side of the plane. To remove, take out the screw, slide the faring back, and slide it down the nose gear faring.
 
I'll offer another opinion in favour of replacing the lower hinge with a row of screws instead. When the innermost eyelets cracked on mine, I cut the hinge back and replaced it with an aluminum plate bolted to the firewall flange, and screws through the cowling into nutplates. I still have the hinges for the rest of the lower cowl, so I guess i've really got the worst of both worlds... Screws, and hinge pins that come out from the center. :)

At overhaul time I'm thinking I may re-do the whole setup with Skybolt fasteners at the firewall. Haven't decided yet.
 
I would definitely ditch the piano hinge in the bottom location, regardless of what you may install elsewhere. The outlet opening concentrates stress. Screws in nutplates, and 1/4 turns are both good choices.

If you ever want to think about reducing outlet area, and thus increasing lower cowl internal pressure, know that piano hinge problems will increase. Pushed to reasonable limits, I found that even the tab strip holding a pair of quarter turns was stressed enough to smoke attach rivets and flex the belly skin. I went back and added "flying buttress" braces, which seems to provide adequate stiffness.

Photo taken while I was working on oil cooler ducting:

 
After a few hours using the per plans hinge method I noticed some working rivets in the suspect area. I added an angle riveted to the firewall to support a nut plate and put one screw with a large washer on both inner sides. Only two screws to remove and the hinge pins.
650 hours, all good.
 
I'm in the process making the hinge pins removal from the lower sides. I'm having S.S. tabs welded to the rods. I'm using a #8 Screw and nut plate to secure it to the fuselage.

So far no reason to believe it won't work.
 
Simple and easy, screws and nut plates all the way around cowl to fuse. Only hinge we use is down the sides for top to bottom cowl. Works very well and you can spend the money not used on the 1/4 turn fasteners on something that is necessary. :)
 
Yep

After the predictable cracking of the lower hinges got underway, I deconstructed my 6A to end up just as Snowflake described, screws underneath and hinges everywhere else, but if I had it to do over, Reiley wins my vote with screws into nut plates all the way around.

Just to keep cussin' to a minimum, let's specify Torx head screws for this job:D

-Stormy
 
Bill Boyd said:
After the predictable cracking of the lower hinges got underway, I deconstructed my 6A to end up just as Snowflake described, screws underneath and hinges everywhere else, but if I had it to do over, Reiley wins my vote with screws into nut plates all the way around.

Just to keep cussin' to a minimum, let's specify Torx head screws for this job:D

-Stormy
Click to expand...

Yes Sir Stormy, torx #8 Stainless Screws only in my book. The Phillips head screws strip too easy and do not looks as nice. :)
 
Another data point....

A per plans RV-14(A) build will be screws into plates on the bottom of the cowl, and hinges everywhere else.
 
I didn't see the point of a hinge along the bottom. During the build I added a backing plate along the firewall/skin rivets as a bottom cowl support. Installed nut plates and use three screws peer side. With the backing plate taking most the stress I have not had any problems with the screws pulling through the cowl. I can remove those six screws without even getting a knee in the dirt.
 
bottom cowl hinge pin

A friend's RV-8 has pins from the outside which are easy - fixed with #8 screws thru curled end of pin. I elected to go with three Camlocs on either side and these are very easy to fasten/unfasten without even kneeling down.
 
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