examples of (classed) yachts using bladder tanks

The "ventilation" I have overlooked! Hence my comment that of course they "have to" collapse. And yes I thought about multiple bags or liners as I named them, what else?

[baeckmo]

Originally Posted by apex1

........... what else?

Neee Apex, not much, you summed it up pretty clearly. My comment was more towards the blue noses of the LR, who were inclined to reject the collapsing bladder, based on a "nonunderstanding" of the working principles. One of the main features of the bladder is the total absence of vented fuel fumes from a fuel storage!

[wardd]

volume could be replaced by water to maintain trim

ala, old diesel subs

Originally Posted by wardd

volume could be replaced by water to maintain trim

ala, old diesel subs

That was,nt uncommon, but as Thorwald said, it is hard to find that stuff today. And according to his experience it seems some classification bodies do´nt like it anymore.

[expedition]

Nada de salto mortale !!

We are using a bladder tank NOT because we want a non-venting tank but because we need a flexible tank we can put inside another tank through a manhole. This creates a cofferdam equivalent class is looking for.

Bladder tanks happen to fullfill that need.

So of course for this particular application where they are not allowed to collapse, we need to add a venting connection (not to the cofferdam of course). It is exactly this connection (and that of the fuel piping) that class wants fixed which in turn requires it's not collapsible.

I hope it's clear now.

Have a look at my post at http://www.expeditionyacht.org/safet...n-bladder-tank - maybe that clarifies it.

[expedition]

Ohh, and mr. baeckmo,

There is no sloshing issue when you use fire surpressant material.

See this video if you don't believe me.

http://www.youtube.com/watch?v=naPuw...layer_embedded

Thorwald

[TeddyDiver]

So Thorwald to be precise, what you want is a liner in your tank, not a bladder tank.
That fire-supressant-material seems to be enough to take care of the non-collapse issue as well..

[expedition]

Well, all liner applications I have seen do just that: they line anothe surface to seal it and make it leak proof and are usually open on the top. I need a real tank, a tank that collapses. And we need air around the tank to created the cofferdam function.

So I'd call it a bladder tank. Just because we put a vent on it doesn't make it a liner.

No manufacturer I have contacted so far told me 'ahh, you're talking about a liner'.

Anyway, I'm just happy I found a solution that can be approved by class :-).

Originally Posted by expedition

Anyway, I'm just happy I found a solution that can be approved by class :-).

Which one now, Thorwald?

[Yellowjacket]

Look at ATL fuel cells. They have a marine product that is what you are looking for.

Take a look here... http://www.atlinc.com/marine.html

Yeah, thats the stuff we need! It seems they have no difficulties to pass the class survey.

Thank you Yellow.

[baeckmo]

Originally Posted by expedition

Nada de salto mortale !!

We are using a bladder tank NOT because we want a non-venting tank but because we need a flexible tank we can put inside another tank through a manhole. This creates a cofferdam equivalent class is looking for.

Bladder tanks happen to fullfill that need.

So of course for this particular application where they are not allowed to collapse, we need to add a venting connection (not to the cofferdam of course). It is exactly this connection (and that of the fuel piping) that class wants fixed which in turn requires it's not collapsible.

I hope it's clear now.

Have a look at my post at http://www.expeditionyacht.org/safet...n-bladder-tank - maybe that clarifies it.

Guess we have a question of definition here, to me a "bladder tank" is just that, a bladder. By definition collapsible and without venting and perfect to fit into a closed structure. In my book your arrangement is a liner, and as such in need of a vent. My finger was pointing towards one-eyed rules that have no provision for new thinking. I was not stepping on your toe here (at least not intentionally)!!!!

[TeddyDiver]

ATL seems to call that a "fuel cell"