Installing a new Sant Marine poly fuel tank

[Debro]

Your opinion please. We just had a new tank fitted (the previous one cracked at the neck). It was replaced and fitted by the boat manufacturer and we are just concerned about the expansion after fuel goes in. It is fitted with supports on the top, sides, rear. The tank will expand 3% after fuel goes in (manufacturers instructions is to allow space for the expansion). But as the supports fitted do not allow for any expansion or movement do you think the tank will expand okay around the supports? or perhaps the supports be fitted after the tank expand? We are concerned as presumably any movement of the tank may crack the neck (we don't know how the neck cracked in the first instance).
We cannot get any information or reassurance from the fitters or supplier about our concerns.
Would anyone have knowledge of the fitting of a poly tank please. The tank sits in the rear of our boat, there is plenty of space for expansion without the supports. It is the supports we are concerned about.
I have (i think) attached photo's.
Thank You, Debro

[billfisher]

Well it has to be able to expand in all directions. Is it possible to modify the supports to allow for some expansion? You can also use foam so it doesn't move around too much. I think the bottom has to be fully supported too. I fitted one and used a yoga mat cut to size to support it. Another thing is if you fill it completely the fuel breathers will be blocked and they tank will expand a lot in hot weather - which may not be good for the tank.

[Debro]

Well it has to be able to expand in all directions. Is it possible to modify the supports to allow for some expansion? You can also use foam so it doesn't move around too much. I think the bottom has to be fully supported too. I fitted one and used a yoga mat cut to size to support it. Another thing is if you fill it completely the fuel breathers will be blocked and they tank will expand a lot in hot weather - which may not be good for the tank.

Thank you so much for confirmation of my concerns about expansion. We do not like 'she'll be right mate' or no explanation about our concerns. We were at risk for quite a while until we discovered where the fuel was leaking from. We could smell fuel but thought it was just the breathers working. Not so.

Our thoughts are to remove all the hard supports and put a rubber/foam blocks or similar (we need to look at the products to figure out) at the top, rear and side. One side and the bottom will not be possible due to the position installed and the Neck of the fuel tank being connected to the Hose which leads where we fill the tank. This hosing appears to be extremely strong and not flexible, not allowing for expansion, which may be what caused the neck of the fuel tank to crack in the first instance.
Therefore if we replace the hard fixed supports with rubber (or something) the neck and hose still doesn't allow for expansion. I'm sure you will understand what I mean being a supplier of fuel tank equipment yourself.
The installation arrangement just does not seem to be appropriate.
Thinking about the neck and filler hose - to us it would be logical if the filler hose (connected to the neck) was flexible to allow for expansion.
What would be your thoughts on this - being in the field of fuel, is there a flexible hose. We don't know if it is possible to replace.
We really appreciate your response and if you have any further advise would be appreciated too.
Thank You.

[Debro]

Thank you so much for confirmation of my concerns about expansion. We do not like 'she'll be right mate' or no explanation about our concerns. We were at risk for quite a while until we discovered where the fuel was leaking from. We could smell fuel but thought it was just the breathers working. Not so.

Our thoughts are to remove all the hard supports and put a rubber/foam blocks or similar (we need to look at the products to figure out) at the top, rear and side. One side and the bottom will not be possible due to the position installed and the Neck of the fuel tank being connected to the Hose which leads where we fill the tank. This hosing appears to be extremely strong and not flexible, not allowing for expansion, which may be what caused the neck of the fuel tank to crack in the first instance.
Therefore if we replace the hard fixed supports with rubber (or something) the neck and hose still doesn't allow for expansion. I'm sure you will understand what I mean being a supplier of fuel tank equipment yourself.
The installation arrangement just does not seem to be appropriate.
Thinking about the neck and filler hose - to us it would be logical if the filler hose (connected to the neck) was flexible to allow for expansion.
What would be your thoughts on this - being in the field of fuel, is there a flexible hose. We don't know if it is possible to replace.
We really appreciate your response and if you have any further advise would be appreciated too.
Thank You.

Hi Billfisher,
We took off all the hard supports, put a piece of pool noodle at the rear of the tank. We believe the tank can expand against the pool noodle because there is a the hole through the middle of the noodle. The filler neck and rigid fuel hose is hard against boat moulding with no allowance for expansion as the filler hose is too strong. Still a concern. Now the top, front and rear can expand and a little at the sides. Keep our fingers crossed that expansion will not crack the neck. If you have any other advise please let us know. Many thanks Deb.Attachment 126027 Attachment 126029 the photos are upside down. (like my computer skills)

[billfisher]

Hi Billfisher,
We took off all the hard supports, put a piece of pool noodle at the rear of the tank. We believe the tank can expand against the pool noodle because there is a the hole through the middle of the noodle. The filler neck and rigid fuel hose is hard against boat moulding with no allowance for expansion as the filler hose is too strong. Still a concern. Now the top, front and rear can expand and a little at the sides. Keep our fingers crossed that expansion will not crack the neck. If you have any other advise please let us know. Many thanks Deb.Attachment 126027 Attachment 126029 the photos are upside down. (like my computer skills)

Maybe try a slightly longer section of fuel hose. If it has a bit of a bend in it then there should be some scope for movement. Also having some room for expansion on the other side would help. The moulding can be changed to with a bit of fiberglass work. I had to do some fiberglassing to make room for the hose and neck.

When you say 'supports' that worries me. The whole bottom of the tank has to be supported. I made up a plywood base matching the shape of the tank and then put some yoga mat over it.