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Post by kd9truck on Dec 9, 2018 4:50:34 GMT
Hull condensation hacks welcome
I am really intreasted to know everyone is addressing the hull condensation because of humidity. Dehumidification is the direction I am headed and hoping to set it up to run it on solar power at 2 hours a day. The boat will be sealed and ran on a timer when we are away.
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Post by vasko on Dec 9, 2018 19:45:07 GMT
If you have power aroung I was more happy with 80w tubular heather..,
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Post by rene460 on Dec 10, 2018 5:02:07 GMT
My preferred approach to condensation issues is ventilation. After all, even when it is raining, the outside air does not exceed 100% humidity, and usually any measurements indicate a little less. So as long as you do not bring in the actual rain, you don’t add condensation. Then, when any sun warms the boat, the same air moisture content at higher temperature is lower humidity and hence lower humidity. So long as the incoming air is lower humidity than inside the boat, ventilation removes moisture, so keeps the atmosphere below the dew point.
Our SO30i has a permanent vent fitting in the main cabin hatch, the type that allows air flow but not water flow (providing you don’t have green water over the deck), and our gas regulations require vent holes in the main hatch. Our dodger is always in place and we have never had signs of water inside through either of these even in heavy rain despite wind direction.
You can also make a vent in the life raft locker that does not admit water in any weather. If you install a little 12v exhaust fan to this vent you will always have air flow through the boat, and a dry boat. Easily powered by your solar panel, especially if you build a little Arduino project to run the fan only when the batteries are well charged. We have not had the need to go this far, and I prefer the reliable simplicity of a totally passive system, but if you have a particularly humid climate, you will have to do more. It may be even worth installing a small auxiliary battery just for this purpose, in order to maximise fan run time at night. And add dome temperature differential/humidity measurement to the logic while you are at it. If you are in the tropics, there may be no alternative to a powered dehumidifier.
We had one further issue, in the bottom of the hull under the V-berth. We fitted a little vent in the anchor locker so it does not admit water, and very the front mini bulkhead means this vents around the anchor locker and directly under the bunk, then finds its way further aft. It obviously has to be a type that can be closed at sea, but that applies to every hatch.
With vents at both ends of the boat and mid ships, after nine years, we still have a totally dry boat, no sign or smell of musty air or mildew. Paper tissues left in the boat do not get damp. No condensation on walls etc.
Between the mattress and the base in the V-berth sometimes gets a bit damp when we are actually sleeping in the berth, I suspect the moisture comes from sweat or breath. It has been mostly solved with a 10 mm mesh spacer, under the mattress, and we lift the mattress when leaving the boat for any time.
Rene460
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Post by vasko on Dec 10, 2018 8:13:03 GMT
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Post by rene460 on Dec 10, 2018 11:22:27 GMT
I thought you might have, Vasko. It’s a good and comprehensive system you have.
Do do you also make sure you have good ventilation?
rene460
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Post by kd9truck on Dec 10, 2018 12:39:54 GMT
My preferred approach to condensation issues is ventilation. After all, even when it is raining, the outside air does not exceed 100% humidity, and usually any measurements indicate a little less. So as long as you do not bring in the actual rain, you don’t add condensation. Then, when any sun warms the boat, the same air moisture content at higher temperature is lower humidity and hence lower humidity. So long as the incoming air is lower humidity than inside the boat, ventilation removes moisture, so keeps the atmosphere below the dew point. Our SO30i has a permanent vent fitting in the main cabin hatch, the type that allows air flow but not water flow (providing you don’t have green water over the deck), and our gas regulations require vent holes in the main hatch. Our dodger is always in place and we have never had signs of water inside through either of these even in heavy rain despite wind direction. You can also make a vent in the life raft locker that does not admit water in any weather. If you install a little 12v exhaust fan to this vent you will always have air flow through the boat, and a dry boat. Easily powered by your solar panel, especially if you build a little Arduino project to run the fan only when the batteries are well charged. We have not had the need to go this far, and I prefer the reliable simplicity of a totally passive system, but if you have a particularly humid climate, you will have to do more. It may be even worth installing a small auxiliary battery just for this purpose, in order to maximise fan run time at night. And add dome temperature differential/humidity measurement to the logic while you are at it. If you are in the tropics, there may be no alternative to a powered dehumidifier. We had one further issue, in the bottom of the hull under the V-berth. We fitted a little vent in the anchor locker so it does not admit water, and very the front mini bulkhead means this vents around the anchor locker and directly under the bunk, then finds its way further aft. It obviously has to be a type that can be closed at sea, but that applies to every hatch. With vents at both ends of the boat and mid ships, after nine years, we still have a totally dry boat, no sign or smell of musty air or mildew. Paper tissues left in the boat do not get damp. No condensation on walls etc. Between the mattress and the base in the V-berth sometimes gets a bit damp when we are actually sleeping in the berth, I suspect the moisture comes from sweat or breath. It has been mostly solved with a 10 mm mesh spacer, under the mattress, and we lift the mattress when leaving the boat for any time. Rene460 |
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Post by kd9truck on Dec 10, 2018 13:12:52 GMT
If you have power aroung I was more happy with 80w tubular heather.., I like the heat idea but I don’t think it removes the humidity from the air unless it is the heat from a dehumidifier. i am on Long Island and sail the LI sound in the summer we can be in the 90 % range for days at a time. |
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Post by kd9truck on Dec 10, 2018 13:15:15 GMT
I will look into that, thanks |
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Post by vasko on Dec 10, 2018 13:23:17 GMT
I thought you might have, Vasko. It’s a good and comprehensive system you have. Do do you also make sure you have good ventilation? rene460 yes I I have - unfortunately I have some water leak from some of my top windows and this winter I covered the hull with plastic .. hence the high humidity that I currently have ( 70+ %) |
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Post by kd9truck on Dec 10, 2018 13:25:42 GMT
My preferred approach to condensation issues is ventilation. After all, even when it is raining, the outside air does not exceed 100% humidity, and usually any measurements indicate a little less. So as long as you do not bring in the actual rain, you don’t add condensation. Then, when any sun warms the boat, the same air moisture content at higher temperature is lower humidity and hence lower humidity. So long as the incoming air is lower humidity than inside the boat, ventilation removes moisture, so keeps the atmosphere below the dew point. Our SO30i has a permanent vent fitting in the main cabin hatch, the type that allows air flow but not water flow (providing you don’t have green water over the deck), and our gas regulations require vent holes in the main hatch. Our dodger is always in place and we have never had signs of water inside through either of these even in heavy rain despite wind direction. You can also make a vent in the life raft locker that does not admit water in any weather. If you install a little 12v exhaust fan to this vent you will always have air flow through the boat, and a dry boat. Easily powered by your solar panel, especially if you build a little Arduino project to run the fan only when the batteries are well charged. We have not had the need to go this far, and I prefer the reliable simplicity of a totally passive system, but if you have a particularly humid climate, you will have to do more. It may be even worth installing a small auxiliary battery just for this purpose, in order to maximise fan run time at night. And add dome temperature differential/humidity measurement to the logic while you are at it. If you are in the tropics, there may be no alternative to a powered dehumidifier. We had one further issue, in the bottom of the hull under the V-berth. We fitted a little vent in the anchor locker so it does not admit water, and very the front mini bulkhead means this vents around the anchor locker and directly under the bunk, then finds its way further aft. It obviously has to be a type that can be closed at sea, but that applies to every hatch. With vents at both ends of the boat and mid ships, after nine years, we still have a totally dry boat, no sign or smell of musty air or mildew. Paper tissues left in the boat do not get damp. No condensation on walls etc. Between the mattress and the base in the V-berth sometimes gets a bit damp when we are actually sleeping in the berth, I suspect the moisture comes from sweat or breath. It has been mostly solved with a 10 mm mesh spacer, under the mattress, and we lift the mattress when leaving the boat for any time. Rene460 Love the fans on there own battery we have 6, love the mattress spacer and proving them on edge we do that as well. I am looking at setting the vessel up to run the AC on an off grid system. |
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Post by vasko on Dec 10, 2018 14:48:33 GMT
If you have power aroung I was more happy with 80w tubular heather.., I like the heat idea but I don’t think it removes the humidity from the air unless it is the heat from a dehumidifier. i am on Long Island and sail the LI sound in the summer we can be in the 90 % range for days at a time. Big part of the humidity is from condensation - the heater prevents heavy condensation e.g lower the humidity in effect... |
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Post by jdl01 on Dec 10, 2018 17:00:57 GMT
If you have access to 110v power, why not put a 20-30 qt. dehumidifier on board with a drain through the galley sink?
You will still want through ventilation - we crack our forward hatch to the first lock position and the companionway doorboard has vent holes and a 3/8" gap at the top. We run it 6 of 24 hours per day during our 7 month rain season,so this does require a power source with more juice than solar panels will provide.
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Post by zaphod on Dec 10, 2018 22:24:16 GMT
I used to use a small heater, but that does not change the moisture in the air, it only changes relative humidity. The problem with that is that the hot air will vaporize moisture and carry it around the boat, and when that warm, moist air comes in contact with cold surfaces such as bare hull, windows, or engine, the moisture condenses on those surfaces. On my old boat I would find that my engine was perpetually wet in the winter because of this. Every spring I had to clean up corrosion and repaint parts of the engine.
While it is true that ventilation can help control condensation, you need to have a significant amount of airflow for that to be effective. Passive vents would not do a very good job.
If you have shore power, a dehumidifier is THE way to go! My boat is at 50% relative humidity all the time. In those conditions there is no chance of condensation, and therefore no chance of mildew and the odours that come along with it
If you don't have shore power, then you can use chemical desiccant. I have never used them, but friends who have swear by them.
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Post by ForGrinsToo on Dec 10, 2018 23:48:48 GMT
We use chemical dessicants for winter storage, and have had good success. We have a cover which breathes, though it is water-repellent. Any condensation there tends to run to the deck and off the stern of the 36i. All four hatches are locked in the vent position. The only time we really have an issue with condensation is Spring to early-Summer when nights are cool still, and plenty of condensation collects on the overhead in the v-berth. We also have a Hypervent mesh pad under the v-berth cushions and stand the cushions on edge when we leave the boat. The 36i is comparatively very dry, so other than the Admiral and me, there isn't a of water vapor, or any reason for it to condense.
Geoff
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Post by kd9truck on Dec 11, 2018 2:26:06 GMT
If you have access to 110v power, why not put a 20-30 qt. dehumidifier on board with a drain through the galley sink? You will still want through ventilation - we crack our forward hatch to the first lock position and the companionway doorboard has vent holes and a 3/8" gap at the top. We run it 6 of 24 hours per day during our 7 month rain season,so this does require a power source with more juice than solar panels will provide. Our condensation conditions are variable but contineus though out the season and are in parody with the dew forming every morning. The AC units on board (2 units, 2 zones) they have a dehumidifier mode, but as stated we would need shore power right now to run them. We are looking into setting up enough solar to run the units on a short cycle with a timer o run daily when we are not on board. The vessel is not over run with humidity and mold, it’s not often sailors collectively speak about maintained issues like moisture even though we all encounter some level throughout our respective sailing seasons. Ps love the breather layer under the mattress. |
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Post by kd9truck on Dec 11, 2018 2:33:09 GMT
I used to use a small heater, but that does not change the moisture in the air, it only changes relative humidity. The problem with that is that the hot air will vaporize moisture and carry it around the boat, and when that warm, moist air comes in contact with cold surfaces such as bare hull, windows, or engine, the moisture condenses on those surfaces. On my old boat I would find that my engine was perpetually wet in the winter because of this. Every spring I had to clean up corrosion and repaint parts of the engine. While it is true that ventilation can help control condensation, you need to have a significant amount of airflow for that to be effective. Passive vents would not do a very good job. If you have shore power, a dehumidifier is THE way to go! My boat is at 50% relative humidity all the time. In those conditions there is no chance of condensation, and therefore no chance of mildew and the odours that come along with it If you don't have shore power, then you can use chemical desiccant. I have never used them, but friends who have swear by them. Going to figure out the energy demands to run the AC dehumidifier effectively on a daily basis. I have used chem desiccant in the bathroom plumbing voids to keep condensation away from the black water tanks and plumbing. They work but have a limited life |
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Post by rene460 on Dec 11, 2018 6:16:21 GMT
Humidity and condensation is more difficult to understand than first appears, there is good reason for no really simple answers.
Keeping the boat free of condensation by ventilation depends on the air outside the boat being generally lower humidity and warmer than the air inside the boat. The daily temperature changes and the tendency of the temperature change inside the boat lagging behind the temperature change of the air outside and the generally less variable water temperature against the hull all combine to achieve a little net moisture removal, to prevent humidity rising to the condensation point.
Ventilation works well in our climate, where we consider anything over about 40% to be quite humid when combined with temperatures above 30 C. A heating element works by keeping the humidity in the boat a bit lower than the natural air temperature to stop condensation, but still relies on some ventilation with low humidity outside air to limit the accumulation of moisture and eventual condensation. It’s a useful addition in cooler areas.
In the tropics, where the humidity in the wet season is considerably higher, and other areas with similar high humidity, I don’t think ventilation alone would do the trick, though with careful monitoring it might be adequate to work for part of the year when the humidity is not so high.
As others have said, a dehumidifier is the only way to continuously remove water from the air inside the boat regardless of humidity. Set up to drain through the sink outlet, or mounted on a dummy main hatch and draining the condensate overboard with a hose through the cockpit.
The absorption chemicals also work but require frequent changing which gets expensive if they can’t be regenerated some how. Both require some restriction of the ventilation so the amount of water to be removed is limited. With chemical absorbents, it may be necessary to seal up the boat reasonably well, so once the air in the cabin is dried, it is not replaced by more moist air, but I don’t know if this results in mildew or other issues.
With warm air around 90% humidity, I don’t see a really practical alternative to a humidifier, so the issue becomes one of power supply. It would be necessary to explore available units to determine power consumption for solar and whether it is practical. They don’t require as much power as a full ac system. It would be worth some trial and error to see if you could run the dehumidifier during sunshine hours only if you are on a mooring with no shore power. Shore power is possible if your marina allows it, but you might need some level of monitoring to make sure you know if someone unplugs your lead.
Rene460
PS I notice that there have been a number of replies that I had not noticed before I wrote the above, think I must have missed refreshing the screen. So apologies for repetition.
We have had small discussions on this topic before but this time everyone is going a little deeper, making it a really great discussion. And still worth using the search box to find earlier threads for completeness on some specific aspects.
Malcolm, is there any chance of correcting the typo in the topic to help future forum readers find the topic?
rene460
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Post by MalcolmP on Dec 11, 2018 7:58:09 GMT
.....Malcolm, is there any chance of correcting the typo in the topic to help future forum readers find the topic? rene460 Sorted 😀 |
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Post by rene460 on Dec 11, 2018 8:26:48 GMT
Thanks Malcolm
rene460
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Post by alenka on Dec 11, 2018 10:11:50 GMT
If you intend leaving your boat plugged into shore power with AC circuits live it would be wise to check with insurance. Some are not happy with this scenario due potential fire risk. There is also the potential for galvanic reaction with other boats.
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Post by zaphod on Dec 11, 2018 15:46:15 GMT
If you intend leaving your boat plugged into shore power with AC circuits live it would be wise to check with insurance. Some are not happy with this scenario due potential fire risk. There is also the potential for galvanic reaction with other boats. If a boat has a correctly installed and maintained shore power system there is a negligible risk of fire, or galvanic action. Of course you dont want to run a heavy load through an undersized extension cord, but other than that there is no great risk. Around here pretty much everyone uses shore power all winter for heaters, battery chargers dehumidifiers etc and boat fires are very rare. If your insurance policy does not expressly prohibit this practice, then I wouldn't say a word to them about it, because if you do, they might decide to modify your policy! |
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Post by alenka on Dec 12, 2018 14:30:24 GMT
Perhaps a better wording would be check your insurance (policy) rather than with!
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