Jabiru-type expanding O-ring fuel caps

[Old Koreelah]

This is where access to the collective wisdom of crash investigators would be invaluable. Does anyone have any experience of these caps?

 

While the baby is apart it's a good opportunity to make some safety improvements, like increasing the thickness of the rubber mounts. The tanks are made from vinyl ester (which tolerates petrol and ethanol) and S-glass, but would likely rupture in a crash . Kevlar structures tend to pop back into shape after a bingle, so I am adding a couple of layers of kevlar to reduce the chance of the tank splitting.

 

These improvements would be pointless if my Jabiru-style fuel caps are likely to pop out in a prang.

 

 

[damkia]

I would think it would depend on where you want to deposit the fuel....

 

If you are bulking up the fuel tanks so they do not split under pressure, capping them so securely that they will not spill fuel, then there is only one place for the fuel to go if they are crushed - the path of least resistance - which I believe includes plastic/rubber fuel lines in the cockpit and out the front over a stinking hot motor.

 

Personally, I would keep the "weak spot" as far away from the passengers and the hot engine as possible. Maybe it was designed this way INTENTIONALLY?

 

 

[damkia]

Duplicate...

 

 

[Old Koreelah]

Personally, I would keep the "weak spot" as far away from the passengers and the hot engine as possible. Maybe it was designed this way INTENTIONALLY?

Thanks for the advice, Damkia. Makes sense. When I designed the tanks I included small-diameter fuel vents out to the wing tips. Maybe I should have used much larger tube to cope with tank compression. Next time...

 

 

[Old Koreelah]

I would think it would depend on where you want to deposit the fuel... I would keep the "weak spot" as far away from the passengers and the hot engine as possible...

You have got me thinking. In a crash, discarding the fuel via the wingtips is the best option. I can replace my 6.5mm vent tubes with 10mm tubes. Doesn't sound much, but a 2.5X increase in cross-sectional area, and far less "friction" to fluid suddenly displaced by a prang.

Each tank holds 25 litres, and is thin and oblong, to allow quite a bit of flexing in the event of a trauma. Perhaps I need an engineer could calculate the tube size required to do this job reliably; what is your guestimate?