Foam filled tanks

[Bob Purton]

I recently acquired a fuel tank for a certain project car I'm working on and it is foam filled, I think they use these in racing to reduce the risk of explosions. Can anyone tell me if the foam reduces the capacity of the tank by much? Also can you use two stroke fuel in them? What do you know?

[richard]

One for google I would think. On the capacity well if it looks like a two gallon tank and it takes about that I reckon that's your answer 

[john p]

I have asked a workmate who works with competion cars and he said the foam makes very little difference to the capacity of the tank and it means the tank just deforms on impact rather than splitting open with scary consequences.

[Bob Purton]

Hmm, thanks John P, that interesting. I just need to know if two stroke mix is ok to put in it now. I have visions of the foam holding all the oil and just letting petrol through!

[steven mandell]

I have foam filled bladders in a couple of my race cars that I've had to replace due to normal aging of the bladders.
I can attest to the fact that the soft open cell foam is cut from sheet and hand placed inside each of the bladders.  As such it provides no strength what so ever to resist splitting of the external aluminum tank.  It does, however resist sloshing and should also slow the release of gas in the event of a catastrophic failure of the bladder, case or cap should the vehicle in which it is housed become seriously impacted, overturned/ lose the cap.
It seems unlikely to me that oil that is dissolved in gasoline could become pulled out of solution preferntially by the foam, although a temporary segregation of the oil in the initial stages of pouring it into an otherwise empty tank seems possible , but without any lasting consequence.  Then again, this is just what seems likely to myself, and is probably better off being properly checked.

[Bob Purton]

Thanks Steve, I knew there must be someone on the forum with some experience of this and I always value your contributions. I didn't particularly want the foam in the tank but as it has no baffles [diaphragm] at least it will prevent the swilling from side to side when I'm cornering at 80mph!   I have found stuff on the interweb since posing the question and it appears that as you say it doesn't prevent the tank from fracturing [obvious really!] but prevents the empty parts of the tank which will be vapour filled from exploding if impacted which kind of makes sense. I think I will use it and see how I get on.