Using bladder tanks in the biges for extra fuel capacity ?

[BartW]

I would like to install extra tank capacity in our boat,
Is it a option to use flexible tanks in the bilges ?
I came across some solid models, that would fit in the available spaces,

http://www.imtra.com/collateral/documents/english-us/products/nauta_brochure.pdf
these have a brass connection for a pipe or a hose.

bring each tank with a quality hose and a tap to a collector in the engine room,
and from there install a pump to empty the flexible tank in the normal tanks,
also from the collector a tap, and connection to the bottom of the normal tanks for filling the flexible tanks,

could this work, or are there issues with such a solution ?

 

[AndieMac]

Usually flexible tanks are used as temporary arrangements for extra fuel on long passages, strapped to higher decks or cockpits to gravity feed into main tanks, but as long as they are laid onto smooth surfaces and secured appropriately perhaps they would be ok.

How does the cost compare to SS, Alloy or GRP, providing the size you need can be fitted through access hatch ways? Which could be the big question.

 

[RAI]

Given the potential mess caused by a leakage, wouldn't it be better to have water in the bladder tanks and use a water tank space for a fuel tank.

 

[tinkicker0]

Bladders are great, providing you do not get wrinkles at the bottom. These can trap water until you hit rough seas, then the water runs out if the wrinkles together in one big hit. Splutter and silence.

Allegedly had a Cessna 172 do that at my flying school once. An apocryphal tale at the club bar apparently....After a long stand down, the cessna was recommissioned, filled up, tank drains checked for water without result and a taxi to the runway. The water was displaced from the bag wrinkles during the taxi out and got into the carb. Luckily during mag tests at the hold and not at the departure end of the runway in the climb out.
Bout only drawback I can think of, providing it does not sit over any sharp edges.

 

[MapisM]

Well, "leakproof" (as they say) might sound reassuring, but that's actually a rather bold statement, when you think that even with s/steel tanks, leaks are not totally unheard of...!
And even assuming that the thing is very well made, are you sure that the bilge area where you would place it is perfectly smooth, but at the same time capable to restrict its movements? I would fear that it can't withstand for long some rubbing against anything hard, down there - even just a somewhat rough GRP surface, let alone other pointy bits...
Another thing which pops to my mind (but maybe I missed it in the brochure, to which I only gave a quick look) is that you might need to find a way to allow the flexible tank to breath, while "backfilling" it as you have in mind.

PS: aside from the technicalities, do tell, are you thinking to use Port of Benghazi for refilling with cheap fuel?

 

[BartW]

How does the cost compare to SS, Alloy or GRP, providing the size you need can be fitted through access hatch ways? Which could be the big question.

yes the main issue with solid tanks is acces, and shape of the available space,
makes that we would have to fit many small tanks, with all the tubing, is a very big task.

the bladder tanks don't need "vent's", so in that respect already much more easy

 

[BartW]

Given the potential mess caused by a leakage, wouldn't it be better to have water in the bladder tanks and use a water tank space for a fuel tank.

that's a good idea, but I would like to have 2000l or 3000l extra capacity, instead of just 1000l (capacity of our water tank)
so when doing all the hassle of changing the tubing....

 

[BartW]

I would fear that it can't withstand for long some rubbing against anything hard, down there - even just a somewhat rough GRP surface, let alone other pointy bits...

PS: aside from the technicalities, do tell, are you thinking to use Port of Benghazi for refilling with cheap fuel?

how about placing a rubber or neoprene mat underneath ?


don't need to go that far for cheap fuel, available right here in this marina fe
but would like to be able to stay away longer periods, and travel some distances, without paying $$$$$ for fuel
also in summer, fuel stations are very busy, need to make appointments, etc..
would like do fewer refuelings

 

[rafiki_]

Bart, did you ever see the HLB additional tank for Mucky Farter?

 

[BartW]

did you ever see the HLB additional tank for Mucky Farter?

no I've missed that, was a solid tank ?

 

[rafiki_]

It was an old oil drum fitted in the lazerette, with a pump to transfer fuel to the tank. Primitive but effective.

 

[AndieMac]

Where on BA do you intend to install the bladder tank Bart?

If you are on the boat currently, can you post some pictures with associated dimensions of the void space. Is it possible to lay/fix sheet of plywood or thick rubber down first, to provide a smooth surface?

 

[Jim Schofield]

This site may have what you are looking for:

http://www.turtlepac.com/

I found it while looking for buoyancy bags for my boat.

Jim

 

[jfm]

I can see the attractions Bart. Thing is, I think you will need a lot of them to make a difference. Your hull frames are something like 600mm centres, so on that link only the 27x63 inch sounds like it will fit. It's only 200 litres so you need say 6 to make a difference, but can you fit that many in? And then you need a lot of plumbing both for the deck filler ( have just one, then a manifold?) and the draw off.

If they are in the bilge then the deck fill pipe could add 2m of head so needs to be hydraulic swaged fittings not jubilee clipped

Any pipe work running fore-aft in the bilge space you want to use will have to be moved to fit them in

I wonder also how effective the pick up pipe is in letting you get the last few litres out, especially when they are angled in the bilge

 

[BartW]

I can see the attractions Bart. Thing is, I think you will need a lot of them to make a difference. Your hull frames are something like 600mm centres, so on that link only the 27x63 inch sounds like it will fit. It's only 200 litres so you need say 6 to make a difference, but can you fit that many in? And then you need a lot of plumbing both for the deck filler ( have just one, then a manifold?) and the draw off.

If they are in the bilge then the deck fill pipe could add 2m of head so needs to be hydraulic swaged fittings not jubilee clipped

Any pipe work running fore-aft in the bilge space you want to use will have to be moved to fit them in

I wonder also how effective the pick up pipe is in letting you get the last few litres out, especially when they are angled in the bilge

here is a drawing of the stringers and frames:

actually in the master bedroom I have 2 sections of 0.95m length,
between 2 center stringers is difficult / not possible / existing pipework,
but from there upwards the bilge, we could place bladders on the bottom, going over one or 2 stringers,
I'll make a sketch, and post pics later.
I think then I could use 4 pcs 55"x60" = 1,4 x 1.5m (bladder size when empty) 475l when full
there are others who can make custom sizes

more foreward, under the stairs, and guest cabin heads, I have even longer space, 1,4m between the frames,
and even less obstructions,
but I'm afraid that is too much forward, and will have a negative effect on boat dynamics / consumption, etc....


I was thinking of using a brass manifold as used in domestic water or heating distribution systems,
and bring all hoses via a tap to that manifold,
also from that manifold, a connection with a tap, to the existing tank outlet (for filling)
and one connection to a pump for emptying the bladders in the main tanks

I'm confused about the Nauta "no vent" system,
makes the installation more easy,
does the forum think this will work, any issues, emptying the bladders completely, air traps, pump not getting started, etc..
all other brands mention a "vent " pipe,
this doubles the amount of work with the piping, and what happens if the vent pipe makes a siphon ?

 

[BartW]

If you are on the boat currently, can you post some pictures with associated dimensions of the void space. Is it possible to lay/fix sheet of plywood or thick rubber down first, to provide a smooth surface?

pics are made Callum, will post them later.

 

[Deleted User YDKXO]

Bart, it sounds like you want extra fuel capacity for the long term rather than just a one off trip and therefore I think flexible tanks are not a long term solution because one day you'll get a bilge full of diesel due to leakage. Why not have some proper custom made tanks made up by a company like Tek Tanks http://www.tek-tanks.com/boattanks/custom-boat-tanks/custom-fuel-tanks/

 

[BartW]

Why not have some proper custom made tanks

the main issue is getting the tanks in there Mike, the door opening to the master cabin is only 47cm wide,
not to mention the steps making a 180° turn...

 

[jfm]

I think this idea could work well - I'm not as negative as some others on this! Of course metal tanks would be lovely but you just cannot retrofit them under cabin floors without smashing up the boat. A few extra thoughts:

1. Obviously you need bilge chambers that are smooth, and maybe lined in wetsuit material or something

2. You could have just one pipe going from engine room to the 4 (or any other number) of bladders, with a manifold near the bladders. The same pipe could fill the bladders and empty them. I expect they would fill by gravity and be emptied by a pump and of course you need the right valves etc to achieve that. Electric ball valves and an LED control station would be nice. The plumbing could be something like or 3/4 BSP, nothing big needed (but see 6 below)

3. Easy lift up hatches in the cabin floors would be nice so you can quickly see each bladder. You wont have gauges, so a flow counter would be nice then you know what you have transferred from the bladders

4. As a general modus operandi, I think I would pump the bladder fuel into the main ship tans as soon as there was space, ie as soon as the main tanks had 1500 litres of space. Hence, for 90% of the boat's hours and over winter etc, the bladders would be empty with no pressure in them. They would therefore suffer almost no chafe and wear/tear as the boat bounces on waves

5. Because of that, I think you would be fine putting them "too far forward" Bart. BA is a big ship and one tonne slightly too far forward for a few days is fine. Then you would empty the bladders within in a few days, starting with the furthest forward.

6. The fill pipe, from the main tank to the bladders, needs to be big enough size that it will fill the bladders in the time you have available when filling the boat. If the delivery truck is pumping 200 litres a minute (that's what I get in Antibes) the main tanks fill pretty fast, and if the pipe to the bladders is too small so that the bladders do not fill fast enough you have that awkward job of asking the guy to wait, which may be ok but may not be if he is in a hurry. So it would be nice to have a big enough pipe. 3/4 BSP feel right

Good luck with this

 

[Nick_H]

Could you build a base and sides in situ out of marine ply, then use a bladder of exactly the right dimensions inside it? This would almost eliminate the risk of chaffing or puncture, and the base could maybe span some of the frames and stringers to use fewer but larger bladders.