Sorry, I didn't realise this thread was still active.
If MDF is available where you are then this would be a fantastic choise.
If not, try and get some very thin strips of timber such as sapele.
Whichever you get, you need to make a former. To do this get a thick board of timber or MDF. An old 44mm door would be brilliant.
Draw the shape onto this by drawing around the tank onto the thick timber board.
Cut this out with a jig-saw or band-saw. This is your former. Take time to cut it so it is a near perfect shape.
Now. You need strips of timber anything between 3mm and 6mm and slightly broader than the boarder you want to create. Lets say, 2000mm long by 70mm wide by 3mm thick. Get three of these.
Because they are so thin, the will bend so easy.
Prepae to get messy. and have a friend to assist.
Pour boiling water onto your timber. This helps it to retain it's new shape.
Using good quality wood glue, like evo-stik resin W. Put plenty onto both sides of one length of your timber. This is your middle piece. Sandwich it between the other two.
either you or your friend needs to hold this sloppy gluey mess against the former whilst the other uses brown parcel tape or prefareably cramps. Fasten it to the former
Pull it as tight as possible Wash off as much glue as you can. Leave it for atleast 24 hours.
Remove from the former and sand it down. Now you shoud see if there is any gaps. If so, don't just fill them. Put glue in first, then fill. Leave to dry. Sand again.
I hope this is helpful to you. If indeed it is what you even want.
Si
