Hi Gang,
I am considering the purchase and installation of a Fast Flow emergency bilge pump on our CD32 (pump driven by the propeller shaft). Before I go ahead with the purchase, does anyone have any experience with the company or their pumps?
http://www.fastflowpump.com/534626.html
Thanks,
Cathy
CD32 Realization, #3
Rahway, NJ
Raritan Bay
Fast Flow emergency bilge pumps
Moderator: Jim Walsh
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Cathy Monaghan
- Posts: 3502
- Joined: Feb 5th, '05, 08:17
- Location: 1986 CD32 Realization #3, Rahway, NJ, Raritan Bay -- CDSOA Member since 2000. Greenline 39 Electra
- Contact:
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Matt Cawthorne
- Posts: 355
- Joined: Mar 2nd, '05, 17:33
- Location: CD 36, 1982
Hull # 79
RPM?
Cathy,
Does your shaft turn fast enough to get the desired flow rate? Also, do you have room? I have always thought that this would be a nice emergency pump, but didn't think that there would be room.
Matt
Does your shaft turn fast enough to get the desired flow rate? Also, do you have room? I have always thought that this would be a nice emergency pump, but didn't think that there would be room.
Matt
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Bruce Barber
- Posts: 53
- Joined: Feb 5th, '05, 15:27
- Location: 25D Nancy Dawson,
Shady Side, MD
How fast the flow??
Cathy,
I have no prior knowledge of this pump, but I'd make a couple of comments based on the web site description: The suction point is the opening around the shaft; there is no provision for a suction hose leading to a low point. So the water has flooded to the shaft level before it can begin dewatering, and obviously the engine must still be operating. There will be a lot of flooding water (think weight) already aboard when the pump kicks in. They specify that the discharge point be above the waterline -- they're undoubtedly talking about the flooded waterline -- and selecting this point is important because the flooding water will have increased the draft and probably affected the trim to the extent that the opening by then may be well under water. If so, the advertised flow rates are out the window, though this would depend also on the discharge head. The exit could be moved up to just below deck level, but this would increase the head.
Anyway, before making a purchase I'd ask some pointed questions about capacity vs actual head plus the effects of submerging the discharge thru-hull. I can't help but think there must be better ways of using engine power to dewater a flooding boat.
I have no prior knowledge of this pump, but I'd make a couple of comments based on the web site description: The suction point is the opening around the shaft; there is no provision for a suction hose leading to a low point. So the water has flooded to the shaft level before it can begin dewatering, and obviously the engine must still be operating. There will be a lot of flooding water (think weight) already aboard when the pump kicks in. They specify that the discharge point be above the waterline -- they're undoubtedly talking about the flooded waterline -- and selecting this point is important because the flooding water will have increased the draft and probably affected the trim to the extent that the opening by then may be well under water. If so, the advertised flow rates are out the window, though this would depend also on the discharge head. The exit could be moved up to just below deck level, but this would increase the head.
Anyway, before making a purchase I'd ask some pointed questions about capacity vs actual head plus the effects of submerging the discharge thru-hull. I can't help but think there must be better ways of using engine power to dewater a flooding boat.
Bruce Barber
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Oswego John
- Posts: 3535
- Joined: Feb 5th, '05, 20:42
- Location: '66 Typhoon "Grace", Hull # 42, Schooner "Ontario", CD 85D Hull #1
Fast Flow Pump
Cathy,
Up until this point, I have deliberately held off in replying about this pump because I don't know anything about it, either. From the outpouring of responses, I don't think there are many other readers who are familiar with this type of pump, but I do have some thoughts on it.
I have to go along with Matt and Bruce. I searched the specs that were offered and I couldn't find what I was looking for. In particular, I wanted to see a graph or power curve that showed the relationship with available horsepower, shaft RPMs and gallons pumped per minute. I couldn't draw any conclusions because I lacked certain data.
For instance, what is the engine H.P. of Realization? I could only guess that it might be somewhere between high teens and mid twenties, maybe more. The specs indicate that the low end of the required HP range for their smallest pump is 15 dedicated HP. That is the pumps minimum requirement.
Do you have a reduction gear in your tranny? If so, for sake of argument, I will figure on a 2:1 ratio. Since the pump impeller is directly driven by the shaft, using that ratio the engine when running at 2,400 RPM, the shaft would be rotating at 1,200 RPM. Although the specs say that the unit will pump at variable speeds, I believe that the makers mention 2,400 shaft RPMs to average 350 gallons per minute, a far cry from the very high GPM that are mentioned in the literature. Those figures are from memory and bear checking.
One of the drawbacks, as I see it, is that the shaft drive must always be in forward gear. Reverse gear will work, but only at 50% efficiency. With the engine turning the prop as well as the pump when it is pumping a high volume of water, the horse power falls off considerably and volume will fall off proportionately. I'm trying to visualize what would happen if anyone tried to use this pump while tied up in a slip with the engine racing while mandatorially in forward gear.
Shaft space to mount the pump is critical. Also, there must be room to mount the pump's frame to the hull or tranny.
The literature reads that this is an auxiliary, emergency pump to work in conjunction with the bilge pump(s). This pump won't help pumping until the water level is at a critically high level in the hull. To be effective, an engine driven auxiliary pump should have the intake in the bilge area. In my mind, somebody has to go below to find and stem the source of the inrushing water. It will be too late by the time the water level is above the shaft. Worse yet, because of the water inlet on either side of the pump, if the boat starts to list, both intakes must be under water to prevent the pump from sucking air, resulting in a higher water level. Depending on their location, the batteries might now be possibly submerged, negating the function of the electric powered bilge pump(s).
Just two more possible negatives and I'm finished. The power pickup from the shaft is by mechanical compression of a two part clamp. This is designed for ease of installation. In my way of thinking, when dealing with something so important as an emergency high volume pump, it is better to use a keyway or a flat on the shaft. And lastly, the smallest recommended discharge is 2" pipe.
Cathy, all that I have stated is mostly conjecture on my part, interspersed with a portion of doom and gloom. My reply is mostly to plant seeds of questioning of certain points that might beg to be answered. I would still like to see a power curve delineating HP, RPMs and Gal. Per Min.
Otherwise, I'm confident that the pump unit is well designed, engineered and tested, and has passed all safety requirements.
O J
Up until this point, I have deliberately held off in replying about this pump because I don't know anything about it, either. From the outpouring of responses, I don't think there are many other readers who are familiar with this type of pump, but I do have some thoughts on it.
I have to go along with Matt and Bruce. I searched the specs that were offered and I couldn't find what I was looking for. In particular, I wanted to see a graph or power curve that showed the relationship with available horsepower, shaft RPMs and gallons pumped per minute. I couldn't draw any conclusions because I lacked certain data.
For instance, what is the engine H.P. of Realization? I could only guess that it might be somewhere between high teens and mid twenties, maybe more. The specs indicate that the low end of the required HP range for their smallest pump is 15 dedicated HP. That is the pumps minimum requirement.
Do you have a reduction gear in your tranny? If so, for sake of argument, I will figure on a 2:1 ratio. Since the pump impeller is directly driven by the shaft, using that ratio the engine when running at 2,400 RPM, the shaft would be rotating at 1,200 RPM. Although the specs say that the unit will pump at variable speeds, I believe that the makers mention 2,400 shaft RPMs to average 350 gallons per minute, a far cry from the very high GPM that are mentioned in the literature. Those figures are from memory and bear checking.
One of the drawbacks, as I see it, is that the shaft drive must always be in forward gear. Reverse gear will work, but only at 50% efficiency. With the engine turning the prop as well as the pump when it is pumping a high volume of water, the horse power falls off considerably and volume will fall off proportionately. I'm trying to visualize what would happen if anyone tried to use this pump while tied up in a slip with the engine racing while mandatorially in forward gear.
Shaft space to mount the pump is critical. Also, there must be room to mount the pump's frame to the hull or tranny.
The literature reads that this is an auxiliary, emergency pump to work in conjunction with the bilge pump(s). This pump won't help pumping until the water level is at a critically high level in the hull. To be effective, an engine driven auxiliary pump should have the intake in the bilge area. In my mind, somebody has to go below to find and stem the source of the inrushing water. It will be too late by the time the water level is above the shaft. Worse yet, because of the water inlet on either side of the pump, if the boat starts to list, both intakes must be under water to prevent the pump from sucking air, resulting in a higher water level. Depending on their location, the batteries might now be possibly submerged, negating the function of the electric powered bilge pump(s).
Just two more possible negatives and I'm finished. The power pickup from the shaft is by mechanical compression of a two part clamp. This is designed for ease of installation. In my way of thinking, when dealing with something so important as an emergency high volume pump, it is better to use a keyway or a flat on the shaft. And lastly, the smallest recommended discharge is 2" pipe.
Cathy, all that I have stated is mostly conjecture on my part, interspersed with a portion of doom and gloom. My reply is mostly to plant seeds of questioning of certain points that might beg to be answered. I would still like to see a power curve delineating HP, RPMs and Gal. Per Min.
Otherwise, I'm confident that the pump unit is well designed, engineered and tested, and has passed all safety requirements.
O J
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rhunter
- Posts: 11
- Joined: Jan 2nd, '06, 11:18
- Location: CP 23/3,CP16, Alberg 22,Bayfield 25.CD admirer-looking for right boat
emergency pump/engine powered
How about a "Y" valve connected to the raw water intake with the alternate intake to the bilge. It seems that most intakes are raw water as opposed to fresh water-closed cooling systems. An extra pump and system adds more weight on the stern and is another system to maintain. The "Y" would work in F, N,or R. Unsure about the flow rate of cooling water through the engine-would it be enough to make a signifigant difference? It would probably prolong the time to "ditch"giving extra time for SOS and abandon ship prep in case of catastrophic hull breech. Bob
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Cathy Monaghan
- Posts: 3502
- Joined: Feb 5th, '05, 08:17
- Location: 1986 CD32 Realization #3, Rahway, NJ, Raritan Bay -- CDSOA Member since 2000. Greenline 39 Electra
- Contact:
Re: Fast Flow Pump Data
Here's the pump data:Oswego John wrote:Cathy,
.....I have to go along with Matt and Bruce. I searched the specs that were offered and I couldn't find what I was looking for. In particular, I wanted to see a graph or power curve that showed the relationship with available horsepower, shaft RPMs and gallons pumped per minute. I couldn't draw any conclusions because I lacked certain data......
O J
http://www.fastflowpump.net/541419.html
By the way, not only is this thing a pump, it's a bilge blower which will help keep the engine compartment cool while the engine's running. It does get pretty darn hot down there, even with the ventilation afforded by the cowls on Realization's stern.
I'm interested in the 2" and 3" pumps. Realization's 21 horse Westerbeke 21A diesel is rated at 3000 RPMs. We normally motor at between 2200 and 2400 engine RPMs, usually 2200. The transmission's ratio is 2:1 which means that at 2200 RPMs the shaft should be turning at 1100 RPMs. At only 800 RPMs, the 3" model can remove 5.9 GPS or 21250 GPH (with a 9-foot head), the 2" model substantially less.
This wouldn't be our only bilge pump. We have two already on the boat. I don't think it would hurt to add a 3rd and a bilge blower at the same time. Anyway, I just wanted to see what you guys thought. A friend of mine, with an Irwin 34, has a similar shaft-driven pump and I thought it was a neat idea.
Cathy
CD32 Realization, #3
Rahway, NJ
Raritan Bay