Increasing the diesel tankage on Swan 47

Dear Friends,

200 liter of diesel, or there about, seem a little on our 47, especially when planning to get her to the med in the summer of 2010 and perhaps even further. Thus, I am contemplating adding two additional diesel tanks. One idea would be to place one under each bunk in the forecabin, trying to place them as high as possible so that they can siphon down to the ordinary tanks under each side of the saloon bunks. This solution, although possible, would add weight in the front part of the boat. Perhaps not very good. This being said, there is not very much space elsewhere to dispose of.

Questions: Please suggest solutions and improvements to this idea or other ideas altogether.

Thankfully yours

Philippe

Philippe
Had the same problem with my 40. I followed the lead of many cruisers. Jerry cans secured on the deck. Actually in my case they fit perfectly in the cockpit. Once the trip is over they can be removed thus keeping valuable space free for storage below. Not pretty I will admit but practical.

Cheers
Mike from StormSvale

I agree that diesel tankage (and water as well) on our boats is rather scanty but I would discourage performing expensive and intrusive changes. Jerry-cans on the deck is a possibility but another is plastic bladders in the bilge.
The problem then becomes transferring the liquids into the appropriate and possibly higher tank when needed which is a rather dirty job in the case of diesel!
I would advise a small electric in-line pump.

Daniel, 411-004

One other option would be to spend the money on light air sails and sail handling :-) , though I'm not sure how the 47 performs in light winds.

If you are going to build some additional tankage. The suggestion of another in line pump sounds good. It might be possible to isolate your new tanks so that you can switch between them independently using some y valves and decide which tanks the engine is sourcing from.  Although if you install too far from engine you have to consider the existing fuel pumps ability to pull the fuel from the new tank if it is farther away. Just a thought.

I'm planning on going with jerry cans and a manual hand pump for transferring the fuel from can to to tank for long voyages. (as trying to pour anything into a hole on a pitching deck can be difficult). My Swan 38 only has 110 liters of fuel :-(

-Nathan (s/v Inspiration 38/090)

Sorry but I do not agree on Y valves and a second tank on the fuel system. If, for any mistake, you get air in the system you are in trouble as we all know.
It is still more conservative to keep the fuel system as it is and refill the main tank whenever needed.
Either hand or in-line pumps are fine.

Daniel

Hey Philippe:

A previous owner added to the fuel tank storage on our Swan 47(048). Our two original tanks are port and starboard in the main salon and contain 27.5 gallons each. The 2 additional tanks are located in the aft cabin on the starboard (29 gals.) and port side (23 gals.). I have a meter on my nav panel indicating how full is each individual tank. There is a valve system forward of the engine (see pic) allowing me to select the desired tank.

I have not used any other system for me to have a comparison, but this system is fine.

Milo

s/v The Last of the Normal People

Thank you Friends: Mike, Daniel, Nathan and Milo!

All your advises and suggestions are taken into consideration thankfully. They are very wise indeed. May I make some comments?

1- Investing in light air sails and handling is already done. What do you do when there is no air at all for days on end? The last summer, crossing over to Scotland from Scagen in Denmark, we had a 36 hours with no wind. We motored very econimically and we had barely enough to reach port.

2- Jerry cans and hand pumps: probably the most reasonable but, alas, perhaps not very esthetically appealing. I still will consider the possibility.

3- Adding two extra tanks has been obviously done on Milo's 47 in the aft cabin. This souds as an attractive option. Better aft of course than in the forcabin as I thought at first. However, there is more space there under the bunks: a huge space.

4- Air problem: Indded, it is a matter to take seriously. My idea, if I go for two extra tanks aft, would be to place then higher than the existing one - which are situated on port and starbord sides in the saloon. I will then connect the aft port tank to the port tank saloon and the same with starbord pair. The result would be that when filling the aft tanks the diesel will flow first to the saloon tanks, being lower. When the saloon tanks are full, then the aft tanks start filling...as if they were the same tanks (two by two) with a connecting pipe between each pair. I presume that I might avoid the air problem in this way. Would I not?

Lars, am I missing something here concernin the air issue?

5- For many reason, I have this fix idea that I badly need more diesel capacity. I would have loved to increase it to, say 4-500 liter. AS to the water capacity, I am planning to invest in a water maker!

Million thanks to all for your insight.

Cheers/Philippe

Philippe

De\ar Philippe

I had a S&S48 which I understand is very similar to a 47' I added an additional 50 ltrs fuel tank between the end of the aft cabin and the beginning of the lazarete: just below the steering gear.
I don't konw if 47 has a similar space but the system seems to work very well.
I have a pipe ( 45 mm) going out close to the aft pulpit for diesel INput, and I have another small pipe connected to the already existing vent pipe coming from the main diesel tank for ventilation.
I then have another dedicated diesel pipe with a simple tap which goes directly into the main diesel tank. When the main tank is almost empty I just open the tap and the pressure weight does the rest. my additional tank works like just a big jerrican but fixed permanently to the boat.
No problem of air coming into the system .
The only precautions was to fix properly the additional tank to avoid from mooving when sailing .
50 litres are not much ( two jerrycans) but I ma thinking to replace the tank with a flexible one of 100 ltrs.


Fair winds



sergio/clarion of Skye 48/042

Dear all, dear Lars and Sergio,

Thank you so much for your valuable insights. All points are taken.

Sergio, there is very littel space around the steering arrangement. I was thinking of placing the additional tanks under the aft berths port and starbord.

Lars, The flow of the fuel will have to go from aft to the regular tanks in the salon. Not the other way around. In that way these aft tanks will act as fixed jerrycans (Sergio), whilst the ordinary ones will continues to act and function as they do know: excellently without any air problems and so on. An arrangement with own feed line, own vent to the aft tanks as well as a connection to the regular tansk will be done as per your kind instructions. That is if I go for this project at all.

Lars, as you know, I have a new engine and I did benefit from many advises from you, including the excellent fuel consumption data sheet that you provided me with. I include it here as a pic. You will all notice how little ca. 200 liter of fuel are in certain conditions, such as those encountered in the north sea with adverse currents and tides, with no wind or "wrong" winds, etc.

Thankfully yours

philippe

Beautiful graph! I wonder if I could have a similar one for any of the S&S 411. I was not so lucky to inherit one among the documentation of my hull (411-004) which was, otherwise, quite complete.

Regards to all
Daniel

Daniel,

I am sure that you can. You will need this:

1-Boat data, engine HP, Reduction ration, Propeller type and size.

2- You need to record 4-5 runs in relative calm and deep water (deeper that 15-20 meters) at different RPM, each time recording the speed when stabilised.

exemple: at 1000RPM= X knots; 1500= X1 Knots etc..

Choose sensible intervals that make sense. With that you can plot the data and get your graph. Perhaps Lars could advise.

Cheers/Philippe

Philippe,
of course I could... in particular I already know an estimate of the average of those quantities at cruise speed with a pretty high degree of confidence by years of sailing.
Which, by the way, are very close to the ones given in the table by Lars.
But how would you practically measure, for example, the instantaneous consumption (liter per hour vs RPM) in three points with an acceptable precision? Given that GPS are now quite precise, you still need an extremely precise flow meter or, if you rely on tank measurements by the meter stick, you need a flat ocean and calm weather for, say, at least one hour for each point on the graph.
Something that only patient yard technicians do...
Daniel

Daniel,

Obviously there are known variables and those that are worked out with algoritm. The known variables are your engine consumption at different RPM. Other variables are the hull's flow though the water given all the other variables as mentioned in the last message. The calculus intervenes to determine the right ratios between the known variables.

Lars might have data for your hull.

All in all, the figures cannot be expected to be 100% accurate, but they do give a fair indication.

Cheers/Philippe

Dear Friends,

Phillipe, I have a Swan 47 centreboard called BLACK TIE and we have larger tanks which I think were fitted by Nautor. Our fuel capacity is 400 litres and water is 600 litres. The largest fuel tank is in the bottom half of the hanging locker opposite the heads forward, with the other much smaller tank under the after end of the port settee. This arrangement seems to work well and isn't quite as far forwards as you were suggesting. Gavin

Thank you Gavin,

I am impressed by your capacity in fuel and water. I wonder why Nautor did not do it in all the 47!? Anyway, I will look at the locations that you mention. I will let you know.

Cheers/Philippe