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Bilge Pump Hose Placement
My wife and I purchased a Cape Dory 28 last summer, after having been out of sailing for 30 years. So we don't mind the most basic advice.
We enjoyed our first season, doing a bit of open water sailing between Long Island and Cape Cod, which the boat took to nicely. However, its clear our boat, as well as her new crew, need some work if we are to be more sea worthy.
I have some questions about the placement of the automatic bilge pump hose. First let me try to describe our current setup: The pump is in lowest part of the bilge, just forward of the main hatch steps. From the pump, the hose (plastic with reinforcing ribs outside, smooth inside) runs 18” straight up to enter the engine compartment. From there, it travels 50” at about a 70 degree angle, where it enters the forward bottom of the starboard lazaret. It then moves up the inboard side of the lazaret 48” at a 45 degree angle, where it is tied to the engine exhaust hose. It then moves down 30” at 45 degree angle to the lazaret sole, across the lazaret sole to the outboard side and then up, with a nasty, tape covered 80 degree angle bend, to the thru-hull fitting. Altogether about 12 ft of hose from pump to fitting; however, the fitting is only about 2.5 ft higher than the pump.
Assuming we use the current thru-hull fitting and want an arrangement that keeps the hose off the lazaret sole, (where it lays about with various bumpers, line and chain, boat hooks, etc), and also allows the hose to enter the fitting at a more reasonable angle:
Question 1: In general, what is the effect of length of smooth hose vs. height of rise; so, for example, how much length of smooth hose rising at an angle to 2 ft produces the same pump work load as a perpendicular rise of 3 ft?
Question 2: Is it better to have the hose quickly raise to just above the level of the thru-hull fitting in the forward part of the lazaret and then gradually move aft and down to the fitting; or, should it gradually rise toward the fitting over the length of the lazaret?
Question 3: Given the thru-hull fitting is located at the far aft end of the lazaret on the boat’s starboard side, only 3” forward of the stern and 9” above the at rest water line, can I do anything to the hose, short of a siphon valve I would prefer to avoid, to reduce the chances of sea water flowing, perhaps siphoned, into the bilge. (Someone suggested the line be run higher up, under the top of the lazaret and back before going lower to the thru-hull fitting, and perhaps add a loop to the hose.
Discussion: It seems to me there are two conflicting objectives: the first to maximize the amount of water that can be pumped; and second, to passively prevent water from easily reentering the boat. Also, I have this vague notion that the less hose length lifting the water to maximum height the better, with the longer length moving aft and gradually downward toward the fitting. Perhaps with a loop at the top well forward, combined with a gradual downward run aft, to reduce back flooding and ease the strain on the pump. Of course what is gradually flowing out downward aft could turn to flowing in, downward forward by a substantial following sea if the pump if were not running.
After writing this, I am thinking that perhaps a new thru-hull fitting, more forward near the pump and higher up the hull is really the proper answer. Our previous boat, I now recall, had her thru-hull fittings for both the automatic and manual bilge pumps located higher up the hull, just above each pump. Hmmmm, maybe they were onto something. It does seem a bit bizarre to have the thru-hull fitting so far aft of the pump. Clearly Carl Alberg knew what he was doing when he designed our boat, which handles wonderfully, but I am not sure he had much to do with the fitting placement. I am missing something obvious here?
Sincerely,
BillOfCapeCod
My wife and I purchased a Cape Dory 28 last summer, after having been out of sailing for 30 years. So we don't mind the most basic advice.
We enjoyed our first season, doing a bit of open water sailing between Long Island and Cape Cod, which the boat took to nicely. However, its clear our boat, as well as her new crew, need some work if we are to be more sea worthy.
I have some questions about the placement of the automatic bilge pump hose. First let me try to describe our current setup: The pump is in lowest part of the bilge, just forward of the main hatch steps. From the pump, the hose (plastic with reinforcing ribs outside, smooth inside) runs 18” straight up to enter the engine compartment. From there, it travels 50” at about a 70 degree angle, where it enters the forward bottom of the starboard lazaret. It then moves up the inboard side of the lazaret 48” at a 45 degree angle, where it is tied to the engine exhaust hose. It then moves down 30” at 45 degree angle to the lazaret sole, across the lazaret sole to the outboard side and then up, with a nasty, tape covered 80 degree angle bend, to the thru-hull fitting. Altogether about 12 ft of hose from pump to fitting; however, the fitting is only about 2.5 ft higher than the pump.
Assuming we use the current thru-hull fitting and want an arrangement that keeps the hose off the lazaret sole, (where it lays about with various bumpers, line and chain, boat hooks, etc), and also allows the hose to enter the fitting at a more reasonable angle:
Question 1: In general, what is the effect of length of smooth hose vs. height of rise; so, for example, how much length of smooth hose rising at an angle to 2 ft produces the same pump work load as a perpendicular rise of 3 ft?
Question 2: Is it better to have the hose quickly raise to just above the level of the thru-hull fitting in the forward part of the lazaret and then gradually move aft and down to the fitting; or, should it gradually rise toward the fitting over the length of the lazaret?
Question 3: Given the thru-hull fitting is located at the far aft end of the lazaret on the boat’s starboard side, only 3” forward of the stern and 9” above the at rest water line, can I do anything to the hose, short of a siphon valve I would prefer to avoid, to reduce the chances of sea water flowing, perhaps siphoned, into the bilge. (Someone suggested the line be run higher up, under the top of the lazaret and back before going lower to the thru-hull fitting, and perhaps add a loop to the hose.
Discussion: It seems to me there are two conflicting objectives: the first to maximize the amount of water that can be pumped; and second, to passively prevent water from easily reentering the boat. Also, I have this vague notion that the less hose length lifting the water to maximum height the better, with the longer length moving aft and gradually downward toward the fitting. Perhaps with a loop at the top well forward, combined with a gradual downward run aft, to reduce back flooding and ease the strain on the pump. Of course what is gradually flowing out downward aft could turn to flowing in, downward forward by a substantial following sea if the pump if were not running.
After writing this, I am thinking that perhaps a new thru-hull fitting, more forward near the pump and higher up the hull is really the proper answer. Our previous boat, I now recall, had her thru-hull fittings for both the automatic and manual bilge pumps located higher up the hull, just above each pump. Hmmmm, maybe they were onto something. It does seem a bit bizarre to have the thru-hull fitting so far aft of the pump. Clearly Carl Alberg knew what he was doing when he designed our boat, which handles wonderfully, but I am not sure he had much to do with the fitting placement. I am missing something obvious here?
Sincerely,
BillOfCapeCod
