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Boat Plans And Patterns | Bilge pumps sizes for your boat

Boat Plans And Patterns


Latest News 13 Jan 3014:

As the 2nd week of Jan ends, here at Bowdidge Marine Designs this year is shaping up to be BIG. Every day whilst working on new designs,  answering emails or phone calls, our large printing plotter is working 7 days a week, printing out plans bound for all 4 corners of the globe.

 In regards to new designs, I must get on average 2-3 calls per day, asking about a new design, let alone emails. So overall, its great to see Bowdidge Marine Designs marking its mark around the world.

As for our boat building forum,  it great to see so many members sharing their builds at various stages of construction and also launchings. Some members are now into their 2nd and 3rd builds, slowing stepping up in size with their boats.
For example, Geoff who is now into his 3rd build (a Tropic 14, a Magnum 12 for his father and now a
Sea Strike 16, made up a small video about how unsinkable his Tropic 14:



Click HERE to view


On another note, we regularly have articles about our new designs in the Australain Boat Mag, a great Australian boat mag about anything to do with fishing/ boating and anything else for that matter.

Peter (the editor) writes:
Enjoy - and dont hesitate to flick the link on to your friends and colleagues, as we are taking a much more aggressive circulation stance in 2014, as we grow Australian Boat Mag back up into the 8,500-10,000 openings (circulation) asap. So the more people who get to see and appreciate this issue the better. 
To see more of this great ozzie boating mag, click the link below:
ABM Issue #206 January
http://theboatmag.boatmags.com.au/?iid=86067


Anyway, until next week, you have a good one and...HAVEAGREATWEEKEND

Latest New Design - The Shoreline 16:

"The ultimate fusion of saltwater fun and freshwater freedom."  
Welcome to the Deep V total performance design of the Shoreline 16. Equipped and geared for optimum top end performance, responsive handling and a smooth, dry ride, the Shoreline 16 is designed for the thrill of open-water, wind-in-your-face, push it to the max, taking you to the very limits of your imagination.


To see more of this exciting new design, please click HERE

Sizing Bilge Pumps for your boat:


All to often we often hear of people leaving port, driving off only to realize that theyve left their bungs out and their boat is sinking. With inadequate buoyancy foam and bilge pumps, they turn around and make a mad dash for shore, often beaching their boats either at the beach of at the ramp in order to save their boat from sinking. 

As we all know, bilge pumps would have to be on the top of the list for any boat. Failure to do so can result in water damage, loss of stability, and even sinking. Even so, water will find its way aboard through drips in windows, through hatches and ventilators, and through spray or rain entering an opening. 

In rough weather, solid water will come on deck, finding its way below through everything from chain pipes, hatch gutters or to a door left open for to long.. Then of course there are leaks in the hull itself. These could be small drips through packing glands, damaged fittings, or- the worst fear- a sizable hole from a major impact. 
As well see even a seemingly quite small hole below the waterline can admit a substantial amount of water very quickly.

REQUIRED BILGE PUMP CAPACITY:

There arent many regulations for pleasure craft pump capacity. We can refer to the ISO 15083-2003 (categories A,B and C recreational boats) and AS1799 standard for some guidance.

GPM - gallons per minute

LPM = litres per minute

ISO boats less than 19.6ft (6m): = 2.6 GPM ( 10 LPM or 600 litre per hour)

AS1799 boats less than 33 ft (10m): = 17.44 GPH (66 LPM or 3960 litres per hour)

As you can see, there is quite a variation in minimum bilge pump capacity requirements.

ESTIMATING FLOODING RATE FROM HULL DAMAGE:
















The minimum recommendations for bilge pump capacity seems too low. We can check the minimum required pump capacity against the approximate flooding rate from a rather small hole in the hull below the waterline. The following is a reasonable approx formula for flooding rate:

GPM = 5.56 x d^2 x ((sq.rt)H)

d = approx opening diameter, in 

H = depth of opening below the waterline (head), in 

Example:

Lets assume a simple puncture of approx 2" (50mm) diameter located 6 in (152 mm) below the waterline for a power boat or yacht.

5.56 x 2 inches^2 x ((sq.rt)6 inches) = 54.46 GPM
5.56 x 4 x 2.449 = 54.46 GPM
Whats interesting is: 54.46 GPM x 3.785 = 206.13 LPM !!!!!

If you were unlucky enough to get an impact 1.5 ft down ( 457mm) with the same hole diameter, then the amount of water pouring in would be approx 94 gallons per minute or 351 litres per minute !

Whoops - unless you have some form of foam flotation or sealed air compartments, your going down, unless your boat is made from wood. Even still, you would still want to have the capacity to pump the boat out faster than the water is coming in !

You can quickly see however, that even a hole of modest size (and not all that deep) will quickly exceed the minimum bilge pump capacity required above. There are practical limits to how large a bilge system you can and should install, but I recommend more than the minimum requirements given by the standards above.

SIZING UP A BILGE PUMP FOR THE REAL WORLD:

Many manufacturers bilge pump capacity ratings arent all they ought to be. Most manufacturers rate their pump capacity with no hoses attached and with no lift (head). Those that do rate for head state this clearly, and its usually a nominal 10-ft of 3-metre head or height. However, not a boat in existence operates a bilge pump with no lift or hoses attached.! Also, the friction in 3 to 6 feet (1 -2 metres) or more of hose and pipe commonly found in all bilge systems cuts the flow rate, and the batteries are seldom delivering full oomph.

Manufacturers rate capacity in gph (gallons per hour) or gpm (gallons per minute); or in metric lph (litres per hour) or lpm (litres per minute) Unfortunatly, that shiny new pump rated at, say, 1,500 gph (5,700 lph) in the catalog will seldom deliver more than half that in a real- sevice installation. Indeed, 40 percent of rated capacity is about the norm. In other words, the real flow out the thru-hull outlet from this 1,500-gph (5,700 lph) pump will be about 600 gph (2,280 lph)

Allowing for this loss in flow rate, whats the minimum pump capacity that should be installed? The following will give sensible results.

Pump Capacity (gph) = 1000 + (100 x displacement in long tons)
Or
Pump Capacity (lph) = 3,785 + (372 x displacement in metric tons)

Example:

Assuming a boat has a displacement of 2200 lbs (998 kg or .998 metric tons) 

Long Ton = 2240 lbs

2200 lbs / 2240 = .982 long tons

1000 + (100 x .982) = 1098 gph or 1098 gph / 60 minutes = 18.3 gpm

Or 

3,785 + (372 x .998 metric tons) = 4156 lph or 4156 / 60 minutes = 69.27 lpm

This is the [u]minimum power-driven pump capacity [/u](manufacturers rated capacity; weve allowed for 40 percent efficiency) that should be fitted. If you have less capacity, get a bigger pump or an additional one.

To avoid large amperage draw on the batteries, install the larger high capacity pumps on pads to lift them about 4-5 inches (100-125mm) above the lowest point in each bilge compartment, with each pumps automatic float switch up on the same level. Small -capacity submersible pumps are located right at the lowest point in the bilge sump in each compartment, with their auto float switches at their level. In this way the smaller, low powered pumps handle the vast majority of routine bilge pumping. This reduces battery draw. In the event of a serious flooding situation, the water rises high enough to trip the upper-capacity bilge pumps.

Hope this helps out.

Latest Launchings & Builds for Week 2 (Jan - 2014):

Heres the latest build and launch photos posted in our boatbuilding forum--Congratulations to all for pursuing your dream! Each of you has done beautiful work and should be very proud...
Click the thumbnails below to view some of the latest Builds and launchings:

Nathans Cashmere 27 Build (Aust):
To see more of Nathans build and his move from Marybourgh to Brisbane, click HERE
Plans coming soon ... see here for the Cashmere 35 (bigger sister ship)

Nathans Cashmere 27
















Wills Cruise Control 5.2 Build (Aust):
To see more of Wills build and his move from Sydney to Perth, click HERE
To see more of the Cruise Control 5.2

Wills Cruise Control

















Wills CC 5.2 - The Great Australian Bight
















Adams Sea Strike 16 Launching (Aust):
To see more of Adams build and his launching, click HERE
To see the Sea Strike 16 


Adams Sea Strike 16
















Phils Cruise Control 5.2 Build (Aust):
To see more of Phil planking his boat, click HERE
To see the Cruise Control 5.2 

Phils Cruise Control 5.2





















Russs SportzMaster 19 Build (Cocos Island) :
To see more of Russs rollover party and his build, click HERE
To see more of the SportzMaster 19

Russs SportzMaster 19
















Daryls Tropic 12 Build (England):
To see more of Daryls build and the floods hitting England and his boatyard, click HERE
To see more of the Tropic 12 

Daaaryls Tropic 12














Gazzas Sea Strike 16 Build (Aust):
To see more of Gazzas build, click HERE
To see more of the Sea Strike 16

Gazs Sea Strike 16


















Anthonys Flat Chat 16 Build (Aust):
To see more of Anthonys build, click HERE
To see more of the Flat Chat 16

Anthonys Flat Chat 16















Marks Sea Strike 18 Build (New Zealand):
To see more of Marks build, click HERE
To See more of the Sea Strike 18
















Nates EdgeTracker 426  Build (Aust):
To see more of Nates build and roll over, click HERE
To see more of the EdgeTracker 426

Nates EdgeTracker 426
















Guys Sea Strike 16 Build (Aust):
To see more of Guys build, click HERE
To see more of the Sea Strike 16

Guys Sea Strike 16

















Lances Sea Strike 16 Build (New Zealand):
To see more of Lances build, click HERE
To See more of the Sea Strike 16 

Lances Sea Strike 16

















Maccas EdgeTracker 426 Build (Aust):
To see more of Maccas build, click HERE
To see more of the EdgeTracker 426

Maccas EdgeTracker 426
















Steves Sea Strike 16 Build (Aust):
To see more of Steves build, click HERE
To see more of the Sea Strike 16

Steves Sea Strike 16
















Russs EdgeTracker 426 Build (England):
To see more of Russs build, click HERE
To see more of the EdgeTracker 426 

Russs EdgeTracker 426
















Barts Sea Strike 18 Build (Aust):
To see more of Barts build, click HERE
To see more of the Sea Strike 18 

Barts Sea Strike 18




















Andys Pro Tournament 21 Build (Aust):
To see more of Andys build, click HERE
To see more of the Pro Tournament 21

Andys Pro Tournament 21
















Lukes Cruise Control 5.2 Build (Aust):
To see more of Lukes build, click HERE
To see more of the Cruise Control 5.2

Lukes Cruise Control 5.2




















Anyway, we hope you enjoy reading our latest news, so well see you next week !!
Until the next bite...
Mark Bowdidge
Bowdidge Marine Designs
www.bowdidgemarinedesigns.com



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