installation of new aluminium fuel tank

[bonneville]

just ordered a new aluminium fuel tank, which is full length under floor about 160 ltrs.
there's a lot of conjecture on installation methods of aluminium tanks, and incorrectly fitted ones have caused horror stories for a few people. done a lot of research, and I believe that when correctly fitted, there's usually no problems.
my intentions were to make it a fairly tight fit, with about 15mm clearance on the sides and to take full advantage of the length, change from the current set up and have the filler and breather pipes exiting and entering at the back on the top of the tank, currently the old tank the filler and breathers are on the end of the tank.
with air flow the trick in stopping electrolosis, I was told by the manufacturer, that all there doing for installations now, is using a urethane, large blobs under the tank, setting the tank down on the blobs, and it will keep the tank up 10-15mm underneath.
now they are a pretty reputable company and I don't doubt there methods. the problem I have is that ive just found where water was getting trapped in a cavity behind the eye lit up front, its completely boxed in and when changing to a bigger eye, found that the v block or timber structure was saturated ! to cut a long story short. cut out an inspection hole to get access, about 30 litres of water later, realised ot needs to be fixed ! on further inspection, the floor in the cabin area is showing signs of softness, including the well area where the tank is to be installed. A boat fibre glasser said the cabin floor and tank well area will probably survive for a season or two ( got transom checked, thank god solid as a rock ) but need to get the bow/ eye area done now. back to my original question, if I use the method of using urethane blobs under the new tank to install, this will make it fricken near impossible to remove when I get to do the flooring ! the normal way of removing with the urethane blobs is to tap wooden wedges underneath and apparently over a couple of days it separates it, well, I will have no access to get down and use this method with how much of a snug fit the new tank would be.
I have read, that cutting 10mm strips of Perspex, in long strips, gluing them firstly to the bottom of the tank, was an alternative method to give them clearance, then use urethane blobs to pack and hold the tank down the sides.
thoughts would be appreciated.
I'd love to replace the floor area's now obviously, but the budget and the upcoming snapper season constricts me

bonneville

[Chimo]

Use white cutting board material in strips under your tank. Don't bother glueing anything. The tank can be held in place with some crewed chocks and you can insert some more of the cutting board material on either side to lock it in place under the floor. How is the floor held in place?

The cutting board will keep the metal off the frp bed under the tank and prevent electrolysis, or at least minimize it to the greatest extent possible even if some salt water gets under the tank. The fact that there is a sender unit in the tank with power connected means you have to isolate the tank which you can do by sitting it on the strips of cutting board.

My 250 ss tank in my Vagabond was installed directly onto the frp bed because someone in the factory forgot to instal the spacers when the tank got dropped into place. At least they looked after me when the replacement tank was installed even though as it turned out" it was no ones fault cause Dolly did it!"

The replacement tank has them and it was fitted years ago and we have had no issues.

There is no way I would glue / stick a tank down onto the bed especially if your going to take it out in a year or so to redo your stingers / floor etc.

Frp boats are fine if the water stays on the outside but if you have wood inside them you don't want to mix that with water.

What breed of boat have you got? Not that it makes that much difference unless it has no wood in it which you apparently does.

Cheers
Chimo

[robothefisho]

Sikaflex some thin plastic/rubber strips along the length of the tank stopping short of the end of cavity so water always drains. Plonk tank on top and pack sides and top with pool noodles cut to size. Apparently some rubber reacts with alloy so check with tank manufacturer or google that. Epoxy paint is also a good idea to prolong life of tank

[bonneville]

Hi Chimo, great post, thankyou,
the boat is a cruise craft reef finder, 89 vintage. in, what I thought , pretty good nick , softness wasn't picked up on a survey when I purchased it 18 months ago. the well area is fully glassed in, on removing the two tanks that were there, badly set up and one actually had a small leak as I found out, noticed the floor had some flex. I wasn't going to install a sender unit, I will be running a fuel flow meter connected thru the nmea lowrance set up, plus looking at repowering next year which will have the fuel management system with the motor. The depth of the well is only 190mm so allowing 10 mm under the tank and a 10 mm clearance at the top, only gives me about a 165mm tank height, so allowing more for a fuel sender will cut my volume down.
even with the age of the boat, I love the room it offers and its capability, so factoring in the pending work and re-powering Im happy with the set up.
So you would just sit it on the Perspex/cutting board strips, then just use wedges down the side to chock it in ?
I know the weight with fuel in would hold it in place, but I was worried about it with less fuel, or in some heavy conditions sliding etc.
the way its set up, there will be salt water that sloshes in there until the bilge takes over, the tank builder has said most boats he fits out have the same situation, but getting air underneath the tank is the trick, he even advised that when hosing out the boat, lift the floor boards and hose the cavity under the tank, as its the salt residue that causes the issues, but to ensure no salt water sits in there.
But I like the idea of not setting in glue, as I recon I'd damage the tank when time comes to strip it to get the flooring done, that's if I could actually get in there to prize it up......
bonneville

[bonneville]

Thanks robo, That was one thing I was going to mention Chimo, if strips of anything are put underneath, I was told to totally glue the area of the packer to the tank ! if you don't, water will get between the surface and be trapped there and start a reaction.
The painting of tanks seems to be a point of conjecture as well from what im researching !
from what ive read, the oxide on the tank is its own protector and a lot of coatings need this oxide removed in order for it to successfully adhere, which to me de feats the purpose, not sure about an epoxy paint though. So im picking the best method so far is to get some cut strips, just short of the length of the tank, probably a sikaflax glue, ensuring the strips have no gaps for water to get in and sit, glue to the bottom of the tank only, then chock the sides with a non reacting product ! makes sense for easy removal !
im picking that cutting board material is just an acrylic of some type, so i'll probably try and scource something similar. got about a 10 day wait for the tank build, so i'll track that down next week.......
bonneville

[Chimo]

Bonneville

So you would just sit it on the Perspex/cutting board strips, then just use wedges down the side to chock it in ? Yes but mine has a screwed down clamp at the stern end too

I was told to totally glue the area of the packer to the tank ! if you don't, water will get between the surface and be trapped there and start a reaction. Has not happened to my tank and unglued connection strips yet. I have fresh water washed around the and under the tank when I have had salt water around it. Thr tank is and area you need to keep an eye on. Seafarer fitted a sticker when they fitted the new tank urging that tank and connections be checked as part of normal servicing. I do it more often than that but once you have lost a tank you tend to be conscious of this as an issue.

Cheers
Chimo.

[bonneville]

Thanks Chimo, yes I agree with the checking and maintenance part !
I didn't even know I had a leak in the back one, probably did get the odd wiff, but put it down to the breather, so as I often do a cook up with a little portable cooker, Im not taking any risks.... be interesting to know how many don't even bother to check their tank regularly or if at all.
let alone clamp fittings etc, hence another reason to make it easy to remove, so at seasons end it makes it easy to do a thorough clean out and check !.
regards
bonneville

[scottar]

I have also read somewhere in internet land that the strips should be totally sealed to the tank to stop water sitting against the alloy. I guess it would be pretty pricey but always wondered about coating with something like Rhino-coat or similar heavy duty medium.

[Lucky 1]

Here is a really good article. Pity the guy who installed my fuel tank didn't want a bar of it :(

http://www.yachtsurvey.com/fueltank.htm

[gofishin]

...im picking that cutting board material is just an acrylic of some type.... this material is not acrylic Bonneville, it is generally HDPE, or in some specific cases PTFE. You can but HDPE from you local plastics supplier.

Black is the cheapest, but don't use it!!! Black plastics and most rubbers are mostly made with an activated carbon compound. This is very bad for aluminium. Hatch rubbers etc used on tin boats have to be made without it otherwise corrosion and paint blistering starts pretty fast.

I like the strips under the baffles, for structural reasons, and use multiple strips across the tank, not one long one as it just creates a dam. Gotta let the water out/thru.
Cheers
Brendon

[gofishin]

Here is a really good article. Pity the guy who installed my fuel tank didn't want a bar of it :(

http://www.yachtsurvey.com/fueltank.htm

That is a good article & website Lucky!
Cheers
Brendon

[bonneville]

this material is not acrylic Bonneville, it is generally HDPE, or in some specific cases PTFE. You can but HDPE from you local plastics supplier.

Black is the cheapest, but don't use it!!! Black plastics and most rubbers are mostly made with an activated carbon compound. This is very bad for aluminium. Hatch rubbers etc used on tin boats have to be made without it otherwise corrosion and paint blistering starts pretty fast.

I like the strips under the baffles, for structural reasons, and use multiple strips across the tank, not one long one as it just creates a dam. Gotta let the water out/thru.
Cheers
Brendon
Thanks for that brendon, one queery though ! I will source out that HDPE from a plastic supplier. But you say to put strips across the tank ? wouldn't that just create a build up point ? once any water gets trapped in there, the salt water turns to salt, which is the corrosive part, I was intending on running strips length ways, about 10mm wide, maybe 4 or 5 over the 500mm width of the tank. that way every so often I can lift the centre boards and hose it underneath from the front so everything runs out the back, cross ones would stop the flushing process and would help dam up salt water ? or am I confused on what you were saying ????
bonneville

[gofishin]

I meant not just 500mm strips across the tank, multiple segments, ie 3 x 100 pads plus 2 x 100 spaces = 500. Or shorter pads but more of them etc to reduce the dam effect.

If your tank is longitudinal (along the boat), it will have transverse baffles. No point in running longitudinal strips as the unsupported ally panel in between the baffles is weak.

What are the dimensions of your tank?

[bonneville]

OK, spent the morning ripping a bit more stuff out of the boat so as to get proper measurements for the tank, the last part of the tank well rises 20mm up front, so im getting the tank custom made with a taper in it on the last 500mm. I also have an old solid live bait tank made out of ply and fibreglass over, bolted to the floor against the transom at the back. geez it had some weight to it, 15 kilo's, I took it outside and filled it up, it hold 85 litres !! no wonder the arse was dragging recently when it was full of slimies and we were out off eden at the shelf trolling LOL any ways, even though its a ripper of a set up, its staying out, going to incorporate a live bait tank in a seat pod. SO, upon removal, I had a bit of a spanner thrown in the works ! I have a fibre glassed division in the well area, which was under the live bait tank. separating the tank well area to a bilge area, now I had hoped to have the inlet pipes and breathers exit the top of the tank, well I'd be kicking into them while at the cutting board if they did, so it looks like the new tank has to be set up with the filler and breathers entering and exiting the end of the tank ( if you understand my terminology )
I would prefer they came in and out at the top, what is every ones opinion on both ways ?
I guess the alternative is to re-fit the live bait tank, which is on small legs, which may give me enough clearance to have the pipes on the top of the tank...... should have made it easier and taken a photo ! sorry
bonneville

[bonneville]

Hi brendon, the tank runs length ways, dimensions app, 2100 long 170 high 490 wide......

bonneville

[gofishin]

Bonne, I should have clarified that that pads under your baffles are the main/primary supports.

'If' the baffles are too far apart for the thickness/type of ally used, then secondary supports (under unsupported panel between baffles) may be necessary to stop drumming due to fuel weight & hence fatigue ....IMHO
Cheers
Brendon

[bonneville]

cheers brendon, got that !
Even though the fit wont be permanent, I really want to do it properly, so your feedback is appreciated. I'll speak with the guy when the tanks built and make sure I get it packed underneath where the baffles are. The floor being soft was an unexpected disappointment to say the least, but guess that's what you get with previous owners not installing things properly and drilling holes everywhere in the floor without correctly sealing things ! I sat my live bait tank back in the boat and pondered a tad, decided to refit it, that way all the pipes can be fitted on top of the new tank and there's enough room for the hoses to have a slight radius under the live bait tank and then go to the filler point and breather outlets and be protected well enough. Im picking the partition in the actual tank well is probably structural so Im not going thru the hassel of moving it back further so the tank can be longer and outlet pipes out of toe kicking range.
I'll take some picks of installation when the tank arrives back in about 10 days hopefully....
cheers
bonneville

[Dignity]

A very interesting thread as I was considering altering my set up but I just realized that the last time I had the floor up there was some sort of black mat on top of my tank that a previous owner must have put in to possibly stop it chaffing on the flooring above it. I think I will be removing it post haste.

[gofishin]

Fuel tanks & fuel systems must be the flavour (or is that pain) of the month! (Well they have been on another forum at least :) )

This old thread might have a few hints for you too Bonnie...

http://www.ausfish.com.au/vforum/showthread.php?t=190016

[bonneville]

Brendon that was a brilliant read, very interesting.
firstly I know i'll be asking the manufacturer whether the filler has a pipe going down near the bottom of the tank !
Im pretty sure he does do this, they have a great name, plus I know he said that there will be two breather pipes, and one is vented internally up to the front.
The actual breather set up was a good read. Even though I mentioned that I wanted the fittings on the top of the tank at the back, its mainly because it will be near hard up to the previously mentioned fibeglassed partition, all the hoses will come out of the fittings, the filler will be made so it exits the tank and has a 45 degree angle on it, but they all head upwards with a slight upward curve, then once clear of the back of the live bait tank, they again curve upwards, no liquid could sit in the hoses over this area. my vents are up high exiting the engine well, with no chance of creating a riser situation and having them drop down to the vent pipe ! but hey, i've got a hungry 2 stroke, keeping fuel in my tanks is my issue LOL
But I will put some thought into that set up.
cheers
bonneville

[Fed]

Mine has holes drilled in the back of the coffin to take inlet, outlet & breather hoses + fuel gauge wiring. Tank is screwed straight to the false bottom front & back, not sure if there's anything under it along its length, I suspect not.
I have no idea what the extra brackets are for at the front, common sense would say for a previously fitted tank but the current tank looks very original (30 years old) and the brackets don't look like something you'd use for a fuel tank... very strange.

[gofishin]

...I have no idea what the extra brackets are for at the front... and the brackets don't look like something you'd use for a fuel tank... very strange. STB bracket looks like it was extended (2 x ~1" flat tabs with hole centres same as main angle bracket), and the wingnut on the PT side is even more intriguing Fed. Obviously to secure something but allow easy removal...maybe a tote tank bracket ...or maybe something else :-?!

I will leave you ponder that question. Put your CSI pants on though...;D


Cheers
Brendon

[juggernaut]

Just throwing this out there, but you could "hang" the tank with appropriate brackets welded onto the tank and bolted through the side panels/or angle bracket so that it sits on the side panels - so that it doesn't sit on the floor at all.

I have a 2001 Quintrex with a 95 litre tank and this is the method they have used and I see no problems with this method and is very easy to remove for cleaning.

As for some sort of coating, I use Johnson SC paste/wax after my brothers recommendation from his job as a skipper on a commercial cray boat of which is what he used on the cray tanks etc - which still look as good as new after 10 years. Apply liberally and don't rub it off after applying as you would normally do. Unfortunately, it's cheaper to by in from the US. But still available online in Aus.

Cheers

[bonneville]

Just one more opinion required on the new tank !
the maker has said that the ideal way of putting the filler and breathers in, is on the top of the tank ( at the end )
however, that's just not going to work for me, standing at the bait board, im picking its just to close to "toes"
so I want the pipes to come out the end face of the tank horizontally !
the filler pipe continues inside the tank down to the bottom, like wose one of the breathers is internally made to go to the front of the tank
so im picking there's no real issue with doing it this way ??? just the fact the maker said he preferred to put the pipes in from the top
is their any real difference or disadvantage in doing it my way ??
cheers
bonneville

[Rip it up]

Only for the ease of welding for him I guess. A horizontal fillet weld around the vertical pipe is easier than the other way around.

Only other thought is if you have a hose failure on the horizontal pickup you may lose bulk fuel to the bilge whilst a top mount would stay in the tank?


Damo's dodgy boat building factory.

[bonneville]

cheers Damo,
Yep, hearing you regarding hose failure ! its going to be very easy to access, visually you'll see the filler hose going straight up from the rear to the filler, the floor board will be covering the entry point to the tank, but super easy to lift the board up, even at sea.
if that's the only issue, I can deal with that, just wasn't sure of any function issues having it that way. I see Fed's pic of his tank above is the way I want to have mine, so the makers comment on preffered set up, must have been as you say regarding ease of welding.
definitely is far far easier for my set up, so, i'll run with it my way
cheers
Damo
bonneville

[scottar]

I may be missing something, but if the filler is run through to near the bottom, won't the fuel "back up" and be slower to go into the tank when filling once the fuel gets to a certain depth or is there holes drilled in the sides of this tube once it gets inside the tank.

[bonneville]

Hi scottar,
now, i'll go out on a limb here, but in my defence ive had so much technical sh@t going thru my head lately, I could have got this wrong LOL.
From what I've read, the filler enters the tank and it continues down near the bottom, not sure about any holes in it or not, don't think so, now the principle of this is that that is where the breathers come into it, if it just stopped at the entry, then effectively it would breath straight back out the filler point, from what I gather air is pushed out the breathers allowing for fuel to be pushed in via the bottom of the tank.
now I asked my maker yesterday, and he confirmed the filler continues down towards the bottom.
If this is wrong, im going to spend the rest of the nite, going back over the search function here and find the thread and the culprit who wrote this and put me crook LOL
I think that's how it works thou Scottar.

bonneville

[scottar]

You may well be right but as once the end of the pipe goes under fuel level it will take a bit of time for the levels to equalise I would have thought as you are only relying on gravity and you run the risk of it backing up in the filler pipe until it shuts the bowser off or overflows. Certainly none of my tanks have ever had the filler go any further than the top of the tank. Hopefully I am wrong or it may make for a painfully slow exercise to fill the thing.

[bonneville]

Scottar,
you've now sentenced me to hours of searching ! on old posts LOL
I hear what your saying, maybe I read wrong...


bonneville

[scottar]

Sorry mate. Good excuse for a bevy or two.

[gofishin]

Scottar,
you've now sentenced me to hours of searching ! on old posts LOL
I hear what your saying, maybe I read wrong...


bonneville

Didn't read wrong bonne, needs to be near the bottom. See here, last page, post #104, probably more towards the bottom half of my post. Maybe some other posts too (Too lazy to re-type).

http://www.ausfish.com.au/vforum/showthread.php?t=190016

Your tank man sounds like he has it sussed re filler pipe. Personally I don't like fillers and both breathers exiting at the rear. Any front breather run internally in the tank invariably acts as a trap as soon as it has a bit of fuel in it (boat floors therefore tanks generally run down toward the back). However, that's how a lot of typical aussy tanks are designed/built/installed.

Re top connection, this is not so much a welding 'thing' but more to do with the hose connection (potential leak point) being above the normal max fuel level.

We don't have any fuel system standards for recreational vessels. US, CE, etc have had them for decades, and all were similar. From memory it was a requirement for the filler hose connection to be above the normal max fuel level for safety reasons.

Cheers
Brendon

[bonneville]

Hi brendon,
I just found your post before you replied LOL
O.k, I suppose that's why my floor in the tank well angles up towards the front, I thought it was only the last 500mm or so but maybe its a continuous slope. Ive not actually ordered the new tank yet, ive got to get a straight edge or laser in there to get an accurate drawing for the guy, as I want to get the biggest tank I can in there, so 10mm clearance bottom and same on top, and sides, I'll see what the shape is once I get a straight edge in there.
I just cant fit a new tank with vents exiting from the top, as I have a division wall in the well, dividing the tank area an the bilge area, and the pipes will effectively be kicked into while at the bait board ! my fibreglass mate has suggested to cut it out and move the partitioning back towards the bilge area about 200-250 mm, make the tank longer and then alls good, it would just be a lot easier if it would work and function properly with the filler and breather exiting the end of the tank ! geez, now that's made me think about it all over again LOL
I suppose I could still pre measure the tank, allowing for the partition to moved back, im presuming its there to strengthen the side walls of the tank well, so as long as its put back, 200 odd mm further back, its still functioning or serving its purpose.
Brendon, if I did decide to go with my original idea, filler and breather exiting the rear, as a lot of tanks seem to, it still should work satisfactory ?
bonneville

[bonneville]

p.s,
if the tank is sloped down towards the back, then if the filler was on the top, wouldn't the normal max fuel level be slightly above the filler ?

bonneville

[scottar]

Interesting read. Just wonder though whether or not all those sort of things are bought about by anti-polution requirements rather than practicality. I can see the filler going to the bottom of a tank being of benefit in a roll over situation in so much the fuel should be a lot more contained. The fuel lines in the US are required to have anti syphon valves to prevent spills that way - not sure about the breathers though. I guess we will get to find out soon enough.

[bonneville]

Hi scottar,
I stand to be corrected, but I think all commercial vessels in Australia have to be set up this way, the states are a lot stricter and its already a requirement there, but not with recreational boats here in aussie, but apparently it the system works !
I would say that this would all but eliminate breathing back out the filler, and force all vent fumes out the intended vents !
but I do stand to be corrected....
brendon was right about the fact that specialist tank builders are using this method, well the ones I spoke to anyway, so it must fill o.k

bonneville

[Fed]

Hey Brendon I should have updated that old thread...
http://www.ausfish.com.au/vforum/showthread.php?190016-Blocking-Fuel-Breathers-to-prevent-condensation
I found the spitting problem, the breather hose had shifted forming a dip and once repositioned I can fill at full speed.

[bonneville]

Hi Fed, I read all of that thread with great interest, glad u got it sorted !
amazing how by fixing up the breather position that it fixed the issue of filling !
bet there's a few people that will read that and go check there breathers now !

bonneville

[gofishin]

That's good Fed!

Yes bonne, they are one of, if not the main cause of issues with filling, even if the rest of the system has been designed & built well.

Ensure your breather/vent hoses have no traps, and some nice risers (or inverted traps) at the breather fittings and it should 'work satisfactory', or maybe even better than a lot of others around :) .
Cheers