"Saddle" fuel tanks ?

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Boo2

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Hi,

I'm thinking of extending the fuel tank in my UFO 34. There's currently a tank under the cockpit aft of the main engine, like lots of boats. Because of the shape of the stern and the internal presence of the P-bracket it's going to be hard to extend the existing tank so I was wondering about putting extra "saddle" tanks under one or both of the quarter berths. Owing to the hull shape, the bottom of these tanks would be raised roughly 6 inches cf the main tank but they would have their tops about 8 inches below the top of the main tank. Because of the shape of the rear hull, the saddle tanks would be deepest and widest at the forward end, the bottom would rise on the after direction, with the outboard side also coming inwards.

My question is really about connecting fuel lines : could a feed to the main tank run from the bottom of the saddle tanks, under the quarterberth sole boards, to the bottom of the main tank and still feed OK ?

I guess the vent from the saddle tanks could run from the top aft corner, behind the rear bulkhead and rise to the top of the main tank, would that be OK ?

Or do I need to arrange for a pump for each of the saddle tanks, maybe with valves to arrange for filling from and for pumping into the main tank ? I'd obviously much rather not have any pumps involved, and really valves are only something to forget to open...

Any advice or good links to similar setups gratefully received,

Boo2
 
I think they'd fill and drain fine on the level. You might find all your fuel pooling in the leeward tank when heeled over, though.

EDIT: Just noticed you said vents up to the level of the main tank. I'd want them much higher than this, the vent on the leeward tank needs to come higher than the highest point of the windward tank when heeled over, otherwise if the tanks are full the leeward vent will overflow.

Pete
 
Boo2 said:
Hi,

I'm thinking of extending the fuel tank in my UFO 34. There's currently a tank under the cockpit aft of the main engine, like lots of boats. Because of the shape of the stern and the internal presence of the P-bracket it's going to be hard to extend the existing tank so I was wondering about putting extra "saddle" tanks under one or both of the quarter berths. Owing to the hull shape, the bottom of these tanks would be raised roughly 6 inches cf the main tank but they would have their tops about 8 inches below the top of the main tank. Because of the shape of the rear hull, the saddle tanks would be deepest and widest at the forward end, the bottom would rise on the after direction, with the outboard side also coming inwards.

My question is really about connecting fuel lines : could a feed to the main tank run from the bottom of the saddle tanks, under the quarterberth sole boards, to the bottom of the main tank and still feed OK ?

I guess the vent from the saddle tanks could run from the top aft corner, behind the rear bulkhead and rise to the top of the main tank, would that be OK ?

Or do I need to arrange for a pump for each of the saddle tanks, maybe with valves to arrange for filling from and for pumping into the main tank ? I'd obviously much rather not have any pumps involved, and really valves are only something to forget to open...

Any advice or good links to similar setups gratefully received,

Boo2
Click to expand...

what endurance do you have now & are you hoping to do extended ocean sailing
 
I have found that one very good way to transfer fuel from one tank to another, is to gently pressurize the tank from which you want the fuel to flow, with a dinghy pump. Obviously you would need a reasonable size of pipe between the tanks, otherwise it takes ages.

On my boat I have twin 240 litre tanks. The cross-connection pipe, whIch is normally closed is 3/4", and if I wanted to blow all the remaining fuel in the port tank into the stbd, I block the vent from the port tank, put the dinghy pump hose, with some cloth round the end, into the port tank filler, make sure that both tank valves are open, and give a few pumps. I can tell when all the fuel has gone by lots of gurgling noises.

Perhaps you could do something similar.
 
Boo2 said:
Hi,

I'm thinking of extending the fuel tank in my UFO 34. There's currently a tank under the cockpit aft of the main engine, like lots of boats. Because of the shape of the stern and the internal presence of the P-bracket it's going to be hard to extend the existing tank so I was wondering about putting extra "saddle" tanks under one or both of the quarter berths. Owing to the hull shape, the bottom of these tanks would be raised roughly 6 inches cf the main tank but they would have their tops about 8 inches below the top of the main tank. Because of the shape of the rear hull, the saddle tanks would be deepest and widest at the forward end, the bottom would rise on the after direction, with the outboard side also coming inwards.

My question is really about connecting fuel lines : could a feed to the main tank run from the bottom of the saddle tanks, under the quarterberth sole boards, to the bottom of the main tank and still feed OK ?

I guess the vent from the saddle tanks could run from the top aft corner, behind the rear bulkhead and rise to the top of the main tank, would that be OK ?

Or do I need to arrange for a pump for each of the saddle tanks, maybe with valves to arrange for filling from and for pumping into the main tank ? I'd obviously much rather not have any pumps involved, and really valves are only something to forget to open...

Any advice or good links to similar setups gratefully received,

Boo2
Click to expand...
Those three tanks will act like Communicating vessels http://en.wikipedia.org/wiki/Communicating_vessels so the level in all thanks will level out.

How can / will you fill the saddle tanks?
If you plan on filling those by filling the main tank you need to size the connecting tubes for that.

prv said:
I think they'd fill and drain fine on the level. You might find all your fuel pooling in the leeward tank when heeled over, though.
Click to expand...
If you draw the tanks and placement (horizontal and vertical) at scale you can easily spot if heeling will be a problem (at what heel the problem will start)
Rolling will not be any problem as the pipes connecting the tanks will act as damper.

You should not use the the fuel line to the engine to connect the tanks...
Empty saddle tanks can feed air into your fuel line.

prv said:
EDIT: Just noticed you said vents up to the level of the main tank. I'd want them much higher than this, the vent on the leeward tank needs to come higher than the highest point of the windward tank when heeled over, otherwise if the tanks are full the leeward vent will overflow.
Pete
Click to expand...
It should be OK to tee the new went lines into the existing one as long as it is vented "higher than the highest point of the windward tank when heeled over".
 
Boo2 said:
Hi,

I'm thinking of extending the fuel tank in my UFO 34. There's currently a tank under the cockpit aft of the main engine, like lots of boats. Because of the shape of the stern and the internal presence of the P-bracket it's going to be hard to extend the existing tank so I was wondering about putting extra "saddle" tanks under one or both of the quarter berths. Owing to the hull shape, the bottom of these tanks would be raised roughly 6 inches cf the main tank but they would have their tops about 8 inches below the top of the main tank. Because of the shape of the rear hull, the saddle tanks would be deepest and widest at the forward end, the bottom would rise on the after direction, with the outboard side also coming inwards.

My question is really about connecting fuel lines : could a feed to the main tank run from the bottom of the saddle tanks, under the quarterberth sole boards, to the bottom of the main tank and still feed OK ?

I guess the vent from the saddle tanks could run from the top aft corner, behind the rear bulkhead and rise to the top of the main tank, would that be OK ?

Or do I need to arrange for a pump for each of the saddle tanks, maybe with valves to arrange for filling from and for pumping into the main tank ? I'd obviously much rather not have any pumps involved, and really valves are only something to forget to open...

Any advice or good links to similar setups gratefully received,

Boo2
Click to expand...

If you had the outlets from the saddle tanks connected to the bottom of the main tank and the saddle tank vents connected to the top side of your existing tank they would fill, vent, and drain through your existing filler and breather. You would need to ensure that when heeled over the windward saddle tank level remains below the main tank breather level if the tanks were all full. You could also fit isolating valves between the saddle tanks outlets and breathers and the main tank to reduce the chance of overflow through the vent and cross contamination.



Posted from Ybw.com App for Android
 
PaulJS said:
If you had the outlets from the saddle tanks connected to the bottom of the main tank and the saddle tank vents connected to the top side of your existing tank they would fill, vent, and drain through your existing filler and breather. You would need to ensure that when heeled over the windward saddle tank level remains below the main tank breather level if the tanks were all full. You could also fit isolating valves between the saddle tanks outlets and breathers and the main tank to reduce the chance of overflow through the vent and cross contamination.



Posted from Ybw.com App for Android
Click to expand...

why not carry extra fuel cans, or is that too simple
 
For the simple way of connecting tanks - few thoughts:
Air vents should go high, above decks of course. If not practical to make new - possible to connect them to existing vent from original tank, if this more practicable (as that vent is already organized an has a place for it) - but then vent pipes must go upwards, connection made highest possible, joined vent better be made larger.

Filling the tanks together - from main tank - may be, make the pipes large enough, put cut-off valves. Possible to make "joined tank system" that is connect all the tanks with their outlets (pipes from bottom) and this will also allow you to fill them all from main. Then they will be for replenishing the main tank only, not to feed the engine, just two feed pipes + vents. Cut-off valves at each end of each pipe.

You may put individual fuel lines (feeds to engine) from each tank, put them to the primary fuel filter (not on engine) or such connecting point. cut-off valves better at tanks. In case of something you then have choice of fuel source. Who knows, things happen, like a hole in the system...

Cut-off valves should be made at any outlet from any tank. This includes air vents ;)
 
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With respect, and please don't think this a criticism, but you do seem enthusiastic to the point of ( unnecessarily perhaps? ) determining to make things more complicated and set yourself huge amounts of work, expense and possible aggro. For questionnable benefit..
I perfectly understand if the forum posting is part of the evolving thinking process-like single line reefing- rather than This-Is-What-Im -Gonna-Do,--Because..:)
KISS for a year or two maybe? Just buy 5x10l diesel jerry cans and fill from syphon tube is my suggestion.
30h is over a day of solid motoring without refill. Ireland or France innit without refilling at sea.

Multi tanks/breathers/fillers/ links/airleaks/cleaning/space occupied,.. ugh!
I would rather get one decent quartertank built to maximise a dead space
 
Blueboatman said:
With respect, and please don't think this a criticism, but you do seem enthusiastic to the point of ( unnecessarily perhaps? ) determining to make things more complicated and set yourself huge amounts of work, expense and possible aggro. For questionnable benefit..
I perfectly understand if the forum posting is part of the evolving thinking process-like single line reefing- rather than This-Is-What-Im -Gonna-Do,--Because..:)
KISS for a year or two maybe? Just buy 5x10l diesel jerry cans and fill from syphon tube is my suggestion.
30h is over a day of solid motoring without refill. Ireland or France innit without refilling at sea.

Multi tanks/breathers/fillers/ links/airleaks/cleaning/space occupied,.. ugh!
I would rather get one decent quartertank built to maximise a dead space
Click to expand...

My crew has a saying, being a former motor engineer, "They get too far under the bonnet"
 
Blueboatman said:
With respect, and please don't think this a criticism, but you do seem enthusiastic to the point of ( unnecessarily perhaps? ) determining to make things more complicated and set yourself huge amounts of work, expense and possible aggro. For questionnable benefit..
I perfectly understand if the forum posting is part of the evolving thinking process-like single line reefing- rather than This-Is-What-Im -Gonna-Do,--Because..:)
KISS for a year or two maybe? Just buy 5x10l diesel jerry cans and fill from syphon tube is my suggestion.
30h is over a day of solid motoring without refill. Ireland or France innit without refilling at sea.

Multi tanks/breathers/fillers/ links/airleaks/cleaning/space occupied,.. ugh!
I would rather get one decent quartertank built to maximise a dead space
Click to expand...

A lot depends on the boat, on my last boat I did just that and with my fuel filler where it was I could have topped up my tank in most conditions, but in the boat before that I would have been quite worried about being able to safely top up the tank from any jerrycan in bad conditions, and once when I was out in not the best weather, I did keep a close eye on the fuel level for that very reason.
 
maxi77 said:
A lot depends on the boat, on my last boat I did just that and with my fuel filler where it was I could have topped up my tank in most conditions, but in the boat before that I would have been quite worried about being able to safely top up the tank from any jerrycan in bad conditions, and once when I was out in not the best weather, I did keep a close eye on the fuel level for that very reason.
Click to expand...

the average boat will never have tankage for ocean crossings
 
maxi77 said:
To be blunt that has sod all to do with my point that the location of the filler does have an impact on the value of jerrycans for topping up at sea
Click to expand...

it was really a general comment & Blueboatman mentioned a syphon devise to transfer fuel.
The UFO 34 was never designed as an ocean cruiser but a "Racer / Cruiser". the OP might have the wrong boat for his eventual dream
 
Last boat I went in had 2 fuel tanks (under berths) connected to main tank in the bilges, like OP wants (it was lower, they just drained into it) supplying the engine. One of those tanks has been a water tank before, but as the need for fuel is important... :)
And then we carried jerrycans and a barrel of some 80 l. Theoretically we could use the fuel from the tanks and replenish them.
Theoretically.
I can assure you - when fuel is a matter of safety, like entering harbour in stormy condition, you must be certain it will be there until berth is reached, not that you will be hurriedly dancing with jerrycans on 20 foot breaking coastal seas, trying to get fuel into your tank instead of that water sloshing on decks.

Somehow in my boat fills are not on decks... :D
 
Because i go to ostend a lot i fitted a removable reserve tank for red fuel use at home waters this having only white in the main tank which i did not intend to use much at home
Both have independent lines to the primary filter. Both with valves
However, i underestimated the amount of fuel going back to the tank from the injector overflow. This only went back to the main tank. Hence white fuel got contaminated immediately. I expected a dribble back which was wrong
The bit that you should be aware of is that of my 26 litres in the reserve i only managed to use half of it because half of it went into the main tank as injector excess. If the main tank was already full the back pressure stopped the engine & caused overflow of fuel on to the deck through the main tank vent
My reserve was an outboard tank so there is no outlet for a return hose.
To use the reserve now i have to use most of the main tank. Switch to reserve. Use it then go back to the main tank to use that which had by passed the injectors
 
Re Rossynant.
I hear what you say about water-free topping up in coastal seas..
Also for larfs I can highly recommend sitting on the stern to keep a Seagull o/b propellor immersed, but not so far back that the sea splashes the Bakelite spark plug cover cos then it splutters and loses oomph...:eek:

SM , never heard that analogy b4, ' they gets too far under the bonnet'. :)

Hope BOO2 can work a sight tube into the new tankage
 
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sailorman said:
it was really a general comment & Blueboatman mentioned a syphon devise to transfer fuel.
The UFO 34 was never designed as an ocean cruiser but a "Racer / Cruiser". the OP might have the wrong boat for his eventual dream
Click to expand...

So what there is no mention of ocean cruising. I sized my fuel storage on my last boat on a lack of wind on a Biscay crossing, something I have experienced more than once. The OP has some 30 hours fuel storage and would like more, a desire I have sympathy with. My point was quite simply that in some boats using cans to top up at sea can be problematic which may be why fitting additional internal tankage had an attraction, it may just be the potential simplicity of all internal tankage and you then introduce the idea that it is all to do with ocean passages. I rally don't see where this applies to my comments and why you apparently attacked me over this, and still try to defend your attack.
 
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