flyrotary@lancaironline.net Mailing List Archive

Six PSI is one thing, 40 psi is much different. I've experienced too many cracked plastic parts on cars, trucks and RV's to feel comfortable putting me and my family inside a cabin with a plastic RV fuel valve. A small crack under 40 psi can cause a very real fire hazard. To me, this is a no-brainer. If its the cost of a quality aircraft quality valve, then get a part time job and save up your lunch money. That's my reasoning.

Oh, one more thing... my kit included a 6-way Andair valve. So, the decision was easy.

On Tue, Oct 28, 2014 at 7:01 PM, Stephen Izett <flyrotary@lancaironline.net> wrote:

Hi there Ernest.

I completely agree with your logic and risk analysis. You could tow a car with the FI hose I was using over a good barb with a quality clamp.
How any well maintained vehicles have had fires associated with the flexible lines. I believe the risk level is way below so many other areas we don’t even consider.

Im building a Glasair with my Father and in the end he wanted to go with a stainless AN system.
He was convinced by a race guy talking about ethanol being added to fuels and the danger to traditional flexible lines.
But we have vinyl ester tanks which won’t like ethanol anyway.
The system we have now has many times the failure points in the form of joints.

As far as the Polak valve, I’m in Perth Western Australia where are you? Ill check postage.

Steve

On 29 Oct 2014, at 3:58 am, Ernest Christley <flyrotary@lancaironline.net> wrote:

But, WHY do you draw the line there, Mark (or anyone else that cares to chime in)? What is the physics behind it. There are literally MILLIONS of plastic parts running around in the fuel systems of vehicles that live in environments much more abusive than airplanes. Fires do happen, but for the most part they are old junkers coated in oil and grease.

And all the calls for steel braided hose: the max fuel pressure in the project I'm working on is 6psi. There isn't a tubing manufactured that will be noticeably stressed by 6psi. I've heard that the steel braid is to protect the hose against abrasion. But, wouldn't a better idea be to eliminate the rubbing, and then replace with a lighter hose that puts less stress on expensive aluminum AN fittings that always seem to be adapters screwed into NPT ports (ie, why not just stay with NPT if we're using it everywhere anyhow?) And why not use a barbed fitting? Nearly every vehicle on the highway today is using them exclusively. Are we really expecting AN fittings to hold the rubber hoses together when we wrap up in a ball tight enough to deform the entire airplane?

It seems we insist that the laws of physics somehow change just because the wheels leave the ground, all in the name of doing a "little bit better", which doesn't seem to me to translate to anything actually beneficial. If we need a rope to hold 100lbs, and I have one rated for 1,000lbs, is it worth paying to get a chain rated at 100,000lbs?

I'm ranting a bit, but I really can't wrap my brain around a lot of this. I bought my current project and I've been pulling off "improvements" the build did. I've got a fortune in AN fittings that are totally pointless...and all to serve 4gph of fuel to an updraft carburetor at 1.5psi. I'm just like, "SHEEESH!!"

On Tuesday, October 28, 2014 3:17 PM, Mark Steitle <flyrotary@lancaironline.net> wrote:

Unlike airplanes, trucks can pull over to the side of the road. Besides, we all know that trucks/busses/RV's never catch fire. ;-0
Personally, I would never use a plastic fuel valve in an airplane, but that's just where I draw the line. YMMV.

OK, I've said it. I'll go back to lurking now.