If water is left in the ballast tank for long periods,is there a risk of osmosis forming on the hull? The boat stays on a berth in a Marina.I have put in chlorine tablets in the tank to prevent algae.
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R
Ramblin' Rod - Mac 26D - SeaQuell
Not Sure
My guess is that the answer is yes, but if it were a significant problem, I'm sure we would have heard about it by now. I have inspected a couple of Mac 26's that have been kept in slips and the hulls and especially rudders didn't fair very well from an osmotic blistering stand point. That's why we applied an epoxy barrier coat before we put SeaQuell in a slip. One thing to consider is that the water ballast tank may actually reduce the risk or severity of blistering on the outside of the hull, as one factor in osmosis is the differential pressure across the substrate. Naturally, the differential pressure across the fibreglass will be less if there is static water pressure on both sides. However, this is just speculation on my part. There is certainly more likley to be a risk of osmotic blistering on the inside of the hull, if there is lying water. I have heard of various sailboat brands blistering in the bilge where standing water is often present. So the answer is, "Could be, but not a significant problem worth worrying about."
My guess is that the answer is yes, but if it were a significant problem, I'm sure we would have heard about it by now. I have inspected a couple of Mac 26's that have been kept in slips and the hulls and especially rudders didn't fair very well from an osmotic blistering stand point. That's why we applied an epoxy barrier coat before we put SeaQuell in a slip. One thing to consider is that the water ballast tank may actually reduce the risk or severity of blistering on the outside of the hull, as one factor in osmosis is the differential pressure across the substrate. Naturally, the differential pressure across the fibreglass will be less if there is static water pressure on both sides. However, this is just speculation on my part. There is certainly more likley to be a risk of osmotic blistering on the inside of the hull, if there is lying water. I have heard of various sailboat brands blistering in the bilge where standing water is often present. So the answer is, "Could be, but not a significant problem worth worrying about."
M
Moon
Thanks
thanks for the reply R'R. I have had an epoxy and antifoul put on but was concerned about the water remaining in the ballast tank.I need to keep it there for stability when the wind comes up when the boat is on its berth. regards, Moon
thanks for the reply R'R. I have had an epoxy and antifoul put on but was concerned about the water remaining in the ballast tank.I need to keep it there for stability when the wind comes up when the boat is on its berth. regards, Moon
Osmosis?
I don't think the interior of the ballast tank is a permeable membrane, so I don't think osmosis is a problem. Any blisters on the hull would be caused by weak or cracked spots in the exterior gelcoat that allows water beneath the gelcoat layer to separate it from the fiberglass layup. Water from inside the tank would have to permeate thru a pretty thick layer of fiberglass cloth and mat to cause problems with the exterior gelcoat. So my personal opinion is, keep the tank filled.
I don't think the interior of the ballast tank is a permeable membrane, so I don't think osmosis is a problem. Any blisters on the hull would be caused by weak or cracked spots in the exterior gelcoat that allows water beneath the gelcoat layer to separate it from the fiberglass layup. Water from inside the tank would have to permeate thru a pretty thick layer of fiberglass cloth and mat to cause problems with the exterior gelcoat. So my personal opinion is, keep the tank filled.
M
mrbill
blisters
I agree with RR, it could be a problem, balast to bilge, more likely that hull to balast. http://www.sailnet.com/collections/articles/index.cfm don casey has great articles and books on the subject. something all boaters should know about.... http://www.sailnet.com/collections/articles/index.cfm?articleid=caseyd015 I was very suprised to find out the fresh water is worse than salt water for blisters... something I would not have guessed...
I agree with RR, it could be a problem, balast to bilge, more likely that hull to balast. http://www.sailnet.com/collections/articles/index.cfm don casey has great articles and books on the subject. something all boaters should know about.... http://www.sailnet.com/collections/articles/index.cfm?articleid=caseyd015 I was very suprised to find out the fresh water is worse than salt water for blisters... something I would not have guessed...
R
Ramblin' Rod - Mac 26D - SeaQuell
Fibreglass substrate is a permeable membrane...
by design. That is how a fibreglass hand layup gets "wetted out". The less perfectly "wetted" the layup, the more permeable by water. MacGregor boats are known for less than perfect layup, and having a lot of voids. Not complaining or blaming, it's just a fact. Actually gelcoat, is much less permeable by water than fibreglass substrate. Normal osmotic blistering on hte outside of the hull only happens where there are microscopic pores in the gelcoat. This explains why the rudders blister much worse than the hull. Basically, they blister from the inside out. All this said, with the epoxy barrier coat, we have slipped SeaQuell for 2 years now, and have yet to come across one blister when applying VC-17 (shows every imperfection) anti-fouling in the spring.
by design. That is how a fibreglass hand layup gets "wetted out". The less perfectly "wetted" the layup, the more permeable by water. MacGregor boats are known for less than perfect layup, and having a lot of voids. Not complaining or blaming, it's just a fact. Actually gelcoat, is much less permeable by water than fibreglass substrate. Normal osmotic blistering on hte outside of the hull only happens where there are microscopic pores in the gelcoat. This explains why the rudders blister much worse than the hull. Basically, they blister from the inside out. All this said, with the epoxy barrier coat, we have slipped SeaQuell for 2 years now, and have yet to come across one blister when applying VC-17 (shows every imperfection) anti-fouling in the spring.
S
Steve Paul
No blisters
I've kept my Mac 26S on a buoy and then in a slip since 1994. Sold it this WInter but always kept the water ballast full, with Chlorine to kill algae and Zebra muscles. Have no blisters on the outside and am unaware of any inside. My rudder is pristine still. I do keep an ablative anti-fouling applied each Spring to hull and rudder. I have no knowledge of any Macs with blisters. Just don't worry about it that much. Steve
I've kept my Mac 26S on a buoy and then in a slip since 1994. Sold it this WInter but always kept the water ballast full, with Chlorine to kill algae and Zebra muscles. Have no blisters on the outside and am unaware of any inside. My rudder is pristine still. I do keep an ablative anti-fouling applied each Spring to hull and rudder. I have no knowledge of any Macs with blisters. Just don't worry about it that much. Steve
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