Sonex Fuel Tank & Oops Fittings

[WaiexN143NM]

Hi tom,
I had the pleasure of sitting across from you, the last 2 years at wayne daniels wed nite bbq, michael here. Dave amsler will send you the tools, he has your address now from your post. When your done, id like to use them. He will include my address in the box he sends you.
To use the PM feature click on DCASonex. Blue 'handle' name . It will bring up a small bio page, look lower left it will say send PM message. Click on that.

WaiexN143NM
Michael

[DCASonex]

Tom,

Tools will be going out today.

David A.

[DCASonex]

Tom,

To add to what Michael said about PM messages. Any sent to you will show up in your e-mail as coming from >>> chris@sonexbuilders.net <<<. If you are using one of the overly selective spam filters, be sure that address is not rejected. After not hearing from you, suspected you might have had a problem with PM messaging, so previously sent you a PM message with my direct e-mail address.

David A.

[Direct C51]

I am getting ready to make the decision on my tank but am having a hard time figuring out how the fitting are "spinning." As seen in the picture below, the hex head of the fitting is molded in to the plastic. Doesn't this keep it from spinning? I would imagine the amount of torque to strip out the plastic holding the hex head in is a lot more than required to screw in a properly lubed male fitting. I understand how repeated side loads can cause leaks, but can someone enlighten me on the "spinning?"

[Waiex 49]

From my experiences with these fittings, the larger one (the one you are showing in the photo) doesn't spin out (or are less prone to spinning). The two smaller fittings in the sump area of the tank "spun out" on me. The larger fitting doesn't seem prone to spinning out, but there have been reports of them developing leaks.

Generally speaking, the fittings don't spin when you install the male fittings. They spin out somewhere down the road when you need to remove the installed fittings.

By my way of thinking the smaller fittings don't engage sufficiently with the plastic of the tank to prevent spinning. The "flat" area of the hex head on the molded in fittings is much smaller on the small fittings, and they cannot counteract the torque used to remove installed fittings.

I believe the problem was made worse (on my tank) by the original builder of my plane being very serious about torquing things down and ended up over tightened things. When I attempted to remove the installed fittings, even though I was very careful, the fuel tank fittings spun in place. I never had a problem with the larger fitting, but in the end I had to remove it to get access to fix the two smaller, spun out fittings.

You may wish to consider changing out the sump fittings with the "oops" fittings while you still have the tank out of the plane. Doing a removal and replacement of an installed tank can be a real chore (and not much fun).

My experiences with replacing spun fittings are on my web page. http://www.mykitlog.com/donbowen

Best regards,

Don Bowen
Viking Waiex N49YX

[rizzz]

I am getting ready to make the decision on my tank but am having a hard time figuring out how the fitting are "spinning." As seen in the picture below, the hex head of the fitting is molded in to the plastic. Doesn't this keep it from spinning? I would imagine the amount of torque to strip out the plastic holding the hex head in is a lot more than required to screw in a properly lubed male fitting. I understand how repeated side loads can cause leaks, but can someone enlighten me on the "spinning?"

If you're making a decision on whether or not to install the oops fittings, YES! Do it now!

Mine was perfect until recently, it started leaking from the big fitting. I have not touched the fittings since the initial installation.
Mine have not "spun" and were screwed in very carefully to absolute minimal torque (just a little more than hand tight).

The leak I have currently is very minimal, only a few drops over the course of a couple of weeks of standing in the hangar and it only seems to leak when we have really cold weather (not so much of a problem now).

I will probably attempt Phil Bird's fix first before installing an oops fitting, the fix is very easy to do and requires only a 3/16 plate, drilled and tapped to screw onto the AN fitting and some Permatex #3 to go between the plate and the tank.
But with the warmer weather we're starting do get here now the tank is fine, no leaks for the moment, so this will be a next winter job.

[kmacht]

For those of you with the oops fittings installed and flying do you find that they loosen up a little over time and start leaking too? On mine it seems that after 20 hours of flight or so mine have vibrated loose enough that they start to drip a little after letting the plane sit for a few days. It takes about a half turn of the nut to get it tight again and leak free. I never liked the design because there is no way to safety the nut that holds the fitting in.

Keith
#554

[DCASonex]

RE loosening over time: I have my oops fittings installed with two O rings, one being outside, under the nut. BUT When installing those found they would be mashed out unevenly as nuts were tightened so cut groove in underside of all nuts to secure the O rings. If you have access to a small lathe that would be my recommendation. Others have successfully used fiber washers under the nuts, and can see where these might work loose over time. A bit of medium strength Loctite on the threads might be worth a try. Would avoid the high strength stuff as there is not much to grab to secure these if later wanting to tighten or remove.

David A. Sonex TD #1327

[DCASonex]

My fittings were very carefully installed and did not start leaking until a year of so after first flight, (and a cold winter).

If you want them, the tools I made for installing those are at their last stop on their most recent journey about the country and will be available soon. (No charge but for the $7 priority mail cost.)

David A.

[fastj22]

If your tank is out, do the oops. Even though the oops isn't a perfect solution, it's easily adjusted in the plane.