SonexBuilders.net

Hey All,

I have an easy one for everyone: just looking for ideas from other owners with the vertical split cowlings.

I have a hinge pin that runs from the oil cooler opening beneath the spinner down to the bottom center of the cowling with one long pin to hold the cowling halves in place. Currently I retain that pin by using a piece of safety wire to wrap around it so there's no way the pin can migrate up into the prop.

I think I'm going to switch the pin direction and try to insert the pin from the bottom of the cowling, but I want a way to lock the hinge pin in place so it doesn't vibrate out of the hinge halves. I know a lot of people do this, so I'm looking for ideas on how to best secure the hinge pin once it's installed. What do people do? Is there a clamp or something that you use to hold the pin in place?

Hopefully this makes sense. Just looking for simple ideas that doesn't involve safety wire! I'm all for the KISS principle and it would be great to have a method that makes it easy to install or remove the cowling.

Thanks everyone and Happy Thanksgiving!

Hi Mike,

I've done it this way a few times. You do need some hinge free area at the end of the run. Might not work in you case, don't know.



Would probably rotate better with a thin steel washer between the hinge eye and skin and the hinge eye and the rivet. Where mine are located in the pic they are lubricated every flight ;-)

As an asside, when I had a vertically split cowl I did a poor job of getting the hinge halves lined up perfectly on the cowl bottom. An easy fix for that is to use slightly undersized music wire instead of the hinge pin.

Good Luck,

Wes

Mike,
I actually had my bottom hinge pin work out and leave the plane on final. It made a few scratches in the prop that I had to fill. The replacement pin I made was a little longer than the first. I wrapped it down to the front of the cowl and put a small loop in it. I then put a rivnut in the cowl to accept a screw though the loop. To pull the cowl I had to remove the screw to release the hinge pin and pull it out. The rivnut was just below the oil cooler opening and the hinge pin was inserted from the top. I didn't want to crawl under to replace the pin. But either way should work.

Mention of cowl hinge pin damaging prop is a reminder that ALL such pins should be made to install and remove ONLY from the rear. If it can come out forward, Murphy's Law says that at some point it it will do so. A tiny but hard steel wire advancing slowing into a wood prop can saw right through the prop.

David A.

Mike, is the bottom surface of the cowling flush with the belly skin as it should be? From day one, the long bottom pin has been inserted from the rear on my Sonex. This pin has about 3/4" of the bottom end of the pin bent 90 degrees and without the cross pins inserted, the bottom of the cowling sags enough to be able to insert the pin completely. Then, when the cross pins are inserted, the sag of the cowling is removed and the long bottom pin is no longer able to move rearward as it would first run into the lower part of the firewall. The cross pins have no tendency to come out during flight any more than the pins at the sides of the cowling so all is secure without any other forms of security needed. I keep a section of outdoor type carpeting on the floor beneath the cowling area so as to be able to lay there comfortably when it's time to remove or replace the pins or do other maintenance. The above has worked successfully for almost twenty years now.

Art,,,,,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,,,,,Jabiru 3300 #261

I'm not sure I have a picture, but I put a hole in one of my aluminum ramps on the outlet. The 90 degree bent part of the pin is worked into that hole so it can't back out.

on my vertically split cowling my bottom cowling hinge pin was so hard to get in I had to use pliers to push it in from the front, while someone else held the cowling together, obviously a two-man job. There was no way this tight fit of the pin was going to vibrate out. After a few years or wrestling with it I finally cut the hinge pin in half. Now I put half in from the front, half from the rear. This works much easier. But, it is still a very tight fit, so I am not worried about it coming out unintentionally.

Ron, legacy Sonex taildragger, aerovee

Here is the keeper I made to keep the hinge pin secure. The pin is bent L on the end and the keeper is screwed on over it. The screw underneath is not visible in the angle but it is there. The fiberglass has to get pulled open to fit over the rounded lip on the inlet. So in order for the pin to hit the prop, this has to happen: The #8 screw comes out, the fiberglass keeper breaks in two and then the tight fitting pin works its way forward.

Rick Caldwell
Xenos 0057 9 hrs,