Fuel Tank Design

I noticed in the worked example that there is no mounting brackets for the tank and the design didnt look like it would lend itself to tank straps easily.

how have you secured the tank in place

Also of interest is that I could not see any vapor control system in place how have you gotten around this? or is it a none issue?

I have not seen any of the aftermarket fuel cells with vapor control systems in place, is it just an issue with emissions control?

I have been considering making my own tank as I have not found anything to suit my specific application of around 90L for the long endurance races. would you recommend stepping up in material thickness given the extra size/weight or could you rely on the internal baffles acting as extra stiffness supports negating the need for thicker material

There are quite a few fuel cell companies offering 90 litre/24 US gallon tanks, and they will all make something to suit your plans, if they aren't suitable*.

Not too sure what you mean by "vapour control system", as it may depend on your specific application - it's part of emissions controls, as you thought, and unlikely to be an issue unless the vehicle is driven on the road and subject to emissions rules.

*You may be well advised to check the specific regulations of all of the race series' you may wish to use the vehicle in, as some will specify the requirements for the fuel tank - this may be the baffling, foam inserts, internal bracing, attachment method, the external tank material, inner liner, etc, as required. Oh, and the fuel being used - I doubt you're using methanol, which is very corrosive to many common materials, but some materials can be affected by high percentages of ethanol.

You are right in that there are a lot of companies offering fuel cells of that capacity however I was looking for something a little more tailored.

It was all a rough idea to begin with but after actually doing my homework the idea has been dumped. While I have access to the right equipment and the skill to actually produce a high quality tank, as you pointed out, the regulations are to much of a hassle to deal with.

I can keep the current setup of 63ltrs that has no foam no baffles no worries. apart from capacity which is not that big a deal in the end.

Or

1. Make a tank of "Free Design" (which is the easy part) and "incorporate a vent system with a gravity activated roll-over valve" and "incorporate a fill plate with one way valves to prevent fuel leakage". costs a bit more but still not that hard and then fill it with foam inserts. Then pay someone to inspect the condition of the foam every 2 years. I have not looked into how much this will cost yet.

2. Buy a FIA FT type cell which personally is way overpriced, you pay more for the certification than the actual item. The tank needs to be inspected and certified after 5 years and the bladder and foam every 2 years.

Think I will stick with my original 34yr old steel tank, just give it a good clean.

I'm in a similar position this side of the Tasman but without the option of the steel tank, if I've read the reg's correctly, for a basic "budget" road/play/club build. I don't actually have an issue with a fuel cell, as such, as the only practical location for tank has to be behind the rear axle, and having been burned before (30+ years and still marked) I don't fancy another, more serious burn - it's the BS bureaucracy I have the issues with.

Depending on your rules are, you may be able to fit foam yourself without bringing it their attention, so avoid the slosh, and an external surge tank for when the pick-up is uncovered.

what rule book does NZ run off?

The problem with foam is that it does break down and it will need to be replaced periodically. The associated problem with that is that you then need to access the internal parts of the tank for cleaning. Which means you need to be able to open up the tank. which leads to a 2 part fuel tank, which I recon would be very frowned upon.

Bladder based tanks are much easier in that you drain the fuel out, then unbolt and pull the bladder out. you then have a much easier part to clean, that can manipulated to access all the hard to reach areas.

It's a sub-section of the Gov'mint vehicle authorites reg's - Low Volume Vehicle, with my complication being it's a hatchback and changing from carb' to EFI.

Then there's the motorsport side, with authority cards and their requirements - it can be done, just takes it out of the 'cheap' build, especially as some things I want to do sometimes have other requirements that aren't directly related. In this case, I have 3 or 4 OEM fuel tanks, but if I read it correctly, I can't modify them as I'd require for the draw and return lines - basically welding on a couple of fittings - but could use them if they didn't need modification.

Doing some checking regarding foam inserts, seems to be rather a wide estimate for service life from different suppliers - E** fuels being markedly lower than straight petrol.