Replacement Built-in Fuel Tank : Aluminium vs Poly & Location
A little while back I got a very light whiff of fuel from the bilge which I (think I) fixed from replacing the old rubber hose link between the main copper fuel line and fuel tank.
But it also got me thinking about the condition of the bow mounted aluminium fuel tank - which is getting on to 16 yrs old.
So after a pile of swearing and JUST getting the tank out of the cabin by the width of a gnat's cock I was able to check it out.
And I have to say it was worth it.
The tank is very well made from 4-5mm plate ali, but was sitting on a bed of expanding foam which obviously had got wet from condensation / washing cab floor / water in bilge - and had extensive pitting / corrosion over the area that had been on contact with the foam. I'm talking BIG pits 3mm deep, so a major leak disaster was probably imminent.
From the amount of pitting I wouldn't be surprised if it was found to already have a pinhole-type leak.
So, my question is whether to get another tank made the same - with the bottom glassed to protect from the same thing happening (from reading it looks like most new boats have f/glass-coated tanks ?) or to get one of the oblong poly tanks that could go in the big storage compartment below the floor ?
The way I see it;
Advantages of new Bow mounted tank :
* All filler & fuel line pipe routing stays the same.
* Keeps the Extra 120-odd kg of fuel up the front of the now slightly ass-heavy boat with the new 4-Stroke Suzi
* Leaves existing floor storage space as usable.
The advantages of a poly floor-mounted tank would be :
* Won't offend the neighbours with obscene language when fitting.
* Won't corrode.
* Easy to source (lots of sizes available)
* I could make more use of the big space up front to store some non-variable weight (i.e. won't change as fuel load decreases)
* Probably fit a much bigger tank.
* Toilet options up front
I haven't even looked at comparing prices yet, but guess either option will be within $100-200 of each other - but maybe a duplicate of the old ally tank will be quite expensive as it's a pretty intricate design.
(I might call the guys at Chivers to see if they have a set of old plans)
I'm guessing someone else has been the the same situation at some point, so it'd be great if anyone has some words of wisdom.
Is there someone around that does CUSTOM Poly tanks ?? (i.e. get a poly tank made to replace the old ally one)
Thanks,
Dizz.
Lamby
Posts: 3145
Date Joined: 04/08/09
It's a bitch of a problem &
It's a bitch of a problem & as I read the thread I immediately thought of a custom poly tank to solve all issues
till
Posts: 9358
Date Joined: 21/02/08
Poly is usually moulded, so
Poly is usually moulded, so that kills custom really.
You know you can make fiberglass tanks? There is a special resin to use, I don't know much about it though.
I see some places recommend that you fiberglass new ali tanks all over to prevent problems with corrosion.
Lamby
Posts: 3145
Date Joined: 04/08/09
Wasn't there a thread on
Wasn't there a thread on plastic welding & custom tanks? Or am I losing my sh!t, probably the latter
till
Posts: 9358
Date Joined: 21/02/08
I haven't ever seen anyone
I haven't ever seen anyone doing more than repairs with plastic welding.
Much like ali, right angle welds are probably a bit pissweak, but the thing is with ali, and stainless, is that you can bend the metal up first, so that you're instead making butt-welds between flat sections instead. Don't think you can do that with plastic.
Or did I miss something too?
southcity104
Posts: 1659
Date Joined: 27/01/09
vinyl ester resin
.. suitable for fuel oil tanks
"Its a life style job"
sea-kem
Posts: 15020
Date Joined: 30/11/09
I've made a few ali tanks and
I've made a few ali tanks and you're right Jamie bend the ali corners so all you're welding is a fillet weld not a butt joint.Some butt joins are unavoidable. I aways test by filling with water and slight air pressure and also dye pen.But if a poly tank will fit go for it probably a cheaper option.
Love the West!
Moylees Brother
Posts: 48
Date Joined: 19/02/09
Try this link Dizzy and see
Try this link Dizzy and see if theres a tank that suits the position you had the original. Changing the weight distribution will change handling dramatically.
http://www.santmarine.com.au/store/images/Sant%20Tanks%20PDF.pdf
Cheers mate
Scott
glastronomic
Posts: 892
Date Joined: 16/02/11
:))
:))
iana
Posts: 652
Date Joined: 21/09/09
I would fit a tank midships
I would fit a tank midships or just forward of the centre of gravity, where ever that is. Then changing fuel contents won't effect trim so much. I also have a stern heavy boat, and have just started moving the batteries up forward (still on deck though, not in the cabin.). Putting in a anchor winch would also be a good way to get the bow down. So if there is space available up front where the old tank used to be, maybe it can be a chain locker. Spare anchor up front and any other heavy items.
Tank
Posts: 358
Date Joined: 12/05/12
Santmarine...recomend them....
Purchased a 100 litre tank from Santmarine some time ago...good to deal with...good warranty...I recomend them..did a lot of looking for someone to make a purpose built tank for more Allycraft tank 450...found this was the best option. easy to fit and plumb up yourself...great price into Pannawonica...and no I am not on their payroll...all the best which ever way you go
For position... the tank with the 60 Etec was slow out of the hole...put fins on it (a bit of improvement) moved portable fuel tanks up the front before deciding to fit the tank under the floor infront of the center console...100 litres of juice up there makes it sit down in the front when full but on the plan she is fine...(plus dive gear and tackle in side lockers) have fitted the tank lengthway in its own cradle - side lockers each side and storage on top of the tank under a casting platform.
I think getting the position of the tank (weight) right is important for performence and handling out on the water...if you have had the boat for a while you know where best to put the weight.
My only problem now is the misses thinks the casting plateform is a sun deck...more weight up the front...yea okay just a little bit more...(just in case she reads this) All good tho...the reel problem is I cant use it for what it is made for...lol
Dizzy
Posts: 753
Date Joined: 21/02/11
Arghh Glas, I was half way
Arghh Glas, I was half way through reading your big post & pics then had to leave for a moment, came back, logged on and it was gone !?!
Was it something I said ?? Haha.
I think I got the just of it - was just checking out your tank's mounting design.
Dizzy
Posts: 753
Date Joined: 21/02/11
Thanks for the replies
Thanks for the replies fellas.
I had a look at a few of the poly tank sites (Santmarine, Moeller) and can't spot anything suitable that would go up front.
Moeller have one but it's very small.
I think I'll just take the old tank to a few places and get some costs / options.
Anyone have good suggestions for NOR ?
I do like the simple option of putting it in the floor, but the existing subfloor storage area is located well behind half way.
There's the other option of cutting the floor and making a new spot but definitely not keen on that, especially not knowing what's underneath.
It's a good opportunity to take it out and experiment with weight placement to see how big a difference it makes.
(I never even got close to emptying the old tank as I never left without a full tank and the Zuke uses FA fuel.)
Does anyone have a big portable tank I can borrow / hire while I'm sorting it out ?
(preferably plastic)
thanks again,
Dizz.
glastronomic
Posts: 892
Date Joined: 16/02/11
Dizzy, find the balance point
Dizzy, find the balance point in your boat and it is most probably not in the middle but way aft with an engine etc at the back.
If your fuel tank sits somewhere in the middle of that fulcrum then that is in my oppinion the better place for it underdecks (as low as possible)
My fuel tank has a 6mm top plate that overlaps the deck.
If you want any more detail then PM me.
regards,
Glassy.
Dizzy
Posts: 753
Date Joined: 21/02/11
Thanks Mate,From the short
Thanks Mate,
From the short glance I got of your pic I'd worked out that the tank had a flange on it which overlapped the deck and supported the weight of the tank.
Is the filler for the tank mounted on the top for direct filling, or is it piped up to a filling point elsewhere ?
snappermiles
Posts: 2100
Date Joined: 05/11/10
dizzy i had the same problem
i coated mine in fibreglass then put a two pack resin over it! much cheaper than replacing! just a few hours work! il get the name of the resin for you when i get home! i bought it all from noahs fibreglass shop on dixon road rockingham
ALL FISHERMEN ARE LIARS EXCEPT YOU AND ME! AND IM NOT SO SURE ABOUT YOU!
glastronomic
Posts: 892
Date Joined: 16/02/11
I heard through the grapevine
I heard through the grapevine that you had a fuel pump failure while off shore?
What caused it?
Interested as I have the same engine installed at the moment.
snappermiles
Posts: 2100
Date Joined: 05/11/10
the mercury fellas tried to blame water in the fuel
but my mechanic went right over the motor and checked the fiilters and water seperators and found nothing! i was also told this can happen from running the fuel tank dry! but this had certainly not happened! so in the end nobody could tell me the exact reason! i had only done 450 hours. heres hoping it doesnt happen again as it is a big job to replace it! the fuel pump is mounted beside the right hand side engine mount! and we had to take the leg off and lift the motor slightly to get it out!
ALL FISHERMEN ARE LIARS EXCEPT YOU AND ME! AND IM NOT SO SURE ABOUT YOU!
Dizzy
Posts: 753
Date Joined: 21/02/11
Hi Snapper, How bad was your
Hi Snapper,
How bad was your tank, just corroded - or leaking too ??
Sounds like a great idea for a new or leak-tested tank to stop corrosion happening in the first place, but I'd be concerned that an existing leak would still let fuel seep between the surface of the ally and the resin / glass which may lead to problems down the line ?
After inspecting the old tank after the mushy aluminium oxide dried and I could use a wire brush I wouldn't touch the old tank with a 10 foot pole.
I really don't think this is salvageable - especially in a bow mounted tank where it cops the most stress from pounding etc.
Here's a few pics of what I'm talking about.
This is the worst face, but there's similar pitting on all faces that were in contact with the foam.
As you can see - it's pretty bad - and I've got bloody big hands (some of those holes are 3mm+ deep :
snappermiles
Posts: 2100
Date Joined: 05/11/10
pitting
my pitting was not quiet as bad as yours but my tank is also bow mounted, im not sure about your boat but i no when my tank is low the boat doesnt ride as well so just take that into account if your thinking of moving the tank.
ALL FISHERMEN ARE LIARS EXCEPT YOU AND ME! AND IM NOT SO SURE ABOUT YOU!
Dizzy
Posts: 753
Date Joined: 21/02/11
Another thing - the old tank
Another thing - the old tank never had a sender unit & I just used the engine management system to calculate fuel used / remaining etc - which proved to be very accurate.
But it was a PITA at fill time (especially if I was solo), as the breather is lower than the filler and is located on the other side of the boat - so i had a couple of over-fills with fuel coming out of the breather.
I was thinking a fuel level sender unit would be a good backup (but probably useless for accurate fuel levels in a tank of this shape)
I s'pose that'd be the advantage of a floor tank with a filler directly on top of it.
Maybe I could get some sort of inspection port / secondary filler fitted to the top of the tank.
glastronomic
Posts: 892
Date Joined: 16/02/11
That is exactly how the new
That is exactly how the new one is;
Filler is from the outside gunnels down to tank, breather outlets on the side and
a separate cap on top of tank that has an inbuild "container" linked to the tank through 2 small openings on bottom and top of tank to take a manual reading.
Get someone who knows how to do it propperly to build you one.
With build in fuel tanks it is very much "Out of sight out of mind" and they contain very flammable fuel if you run a petrol engine.
Perry Home
Posts: 434
Date Joined: 07/10/10
Dizzy - have sent you a pm
I've recently taken a stainless steel bow tank from my boat as it limited through access to te anchor well by filling the cabin space. Will be selling it - check your p.m's and let me know if you re interested. Cheers
Dizzy
Posts: 753
Date Joined: 21/02/11
I decided to keep the weight
I decided to keep the weight up the front, so I just dropped the tank of to Jim at Marineline in Landsdale to get it replicated - top bloke with some good suggestions.
He's just going to install a simple dipstick port as a backup to check the fuel levels against the engine management system (rather than go for the fuel level sensor option)
He's only just got back from leave, but his price & personal service was worth waiting for.
I'm going to get the bottom of it glassed to stop the same problem happening again.
Hopefully get it back this week.
The final product won't be very exciting, but I'll post pics if anyone is interested.
till
Posts: 9358
Date Joined: 21/02/08
Are you going to glass over
Are you going to glass over it to prevent corrosion?
Dizzy
Posts: 753
Date Joined: 21/02/11
Yes mate, underside will be
Yes mate, underside will be glassed. (Mentioned it above)
Probably only need the bottom 200mm glassed as it was the only bit that was in contact with moisture and had any corrosion - but will probably get the whole underside done for peace of mind.
glastronomic
Posts: 892
Date Joined: 16/02/11
You might want to use a Tar
You might want to use a Tar product that normally would be used to seal outside underground walls as a barrier to achieve what you want.
It could be sealing better than fibreglass to alloy which could trap water to your new shiny tank.
And is easily and cheaply applied.
Dizzy
Posts: 753
Date Joined: 21/02/11
I've actually been thinking
I've actually been thinking about that, wondering if a tar option like "proofcoat" would be better than glass.
Greg at GT fibreglass was going to whip a quick glass coating on the bottom, and said he'd use a different type of resin that bonds better to aluminium ? (as well as sanding the surface)
I figured I could just proofcoat the over where the glass ends to seal the join.
I've also wondered how the glass - aluminium bond would go with the aluminium flexing under load and also contracting with temperature.
The bit that would be coated is basically a taper, which could end up just popping the glass off the bottom if the bond breaks.
Maybe a full proofcoat / Tar coating would be a better option ?
Messy stuff though - with the amount of difficulty I had getting it out I'll probably end up with black smudges all through the boat & cabin before I get it back in.
I remember helping the old man out when he proofcoated the entire underside of his FJ45 cruiser 30-odd years ago - I reckon I can still smell the stuff !
glastronomic
Posts: 892
Date Joined: 16/02/11
Greg and his daughter are
Greg and his daughter are doing some work for me as well at the moment!