Steel boat bilge drying?

[LeoKa]

The condensation is filling the bilge in my cabin. I cannot access the bilge there and I am trying to figure out how to keep it dry. I have a heavy duty. blower, which works to an extend, but not enough. The PNW cold water and winter heating overwhelms it and water accumulates. I tried dehumidifiers, too. No luck. They dry the air in the cabin, but not the bilge. If there is no rain and I can run the blower for few days, it seems dry where I can see it. Unfortunately, there are sections I cannot access, nor see. The cold steel is always wet. I had to open the floor in my cabin, so I can blow it somehow, but still not enough.
What anyone is doing to eliminate this much water?
Is there a hot air bilge blower, which I can put way below and let it dry out the area?

 

[Portage_Bay]

Heat, insulation and ventilation. Bring in outside air to heat as opposed to recirculating interior air to take advantage of the change in relative humidity.


If you can vents on cooking and shower areas just as you would in a dirt house.

 

[LeoKa]

Heat, insulation and ventilation. Bring in outside air to heat as opposed to recirculating interior air to take advantage of the change in relative

My cooking is rare. Shower is at separate location.

I am building an air-in and air-out duct system, but is not enough. I use quiet fans, because of the noise level. The airflow is ok, but not enough in these rainy and cold days. I need direct warm/hot air blown into the bilge under my bed where I have no access to, so it could evaporate and the duct system would carry it outside.
One duct is coming down from the diesel furnace area with warm air into the bilge. The other duct is sucking air up from the bilge section at the other end of this area. It works, but not good enough. I would need more airflow ( which is noisy for sleep ), or hotter air blown in during the day, so it could dry out, before I go to sleep. If I could find a small 12v hot air blower, I could setup a timer and let it blow during the day.

 

[LeoKa]

You can buy one of these ...
https://www.seaflousa.com/product/seaflo-dry-bilge-system/

or build your own ...
https://panbo.com/a-dry-bilge-for-50/

Thank you. I have seen these articles and they look good. In my case, it will not work.
There is no access in this bilge area and there is no way to install anything there. The bilge is filled with lead bricks, which are very heavy.
Also, the water accumulation is not significant, but it is enough for rust development. That is my concern.

 

[Pascall]

If the temperature outside the boat is significantly lower than inside the boat, condensation will form on the steel.
The higher you make the temperature in the boat, the more condensation will form!
Insulating the steel is the right solution, but because it is not accessible to you, that is obviously not a solution.
We have a natural ventilation behind the panelling by means of ventilation grilles and works very effectively.
Is there no solution to get under the floor?
We had a similar problem under the polyester shower floor.
I could get under it but it was very difficult.
A hose had broken off from the shower drain and I couldn't replace it through the adjacent inspection hatch.
I then cut a hole in the floor and renewed the hose, also cleaned and painted the bilge under the floor.
Closed the hole again and finished sealant, if I want to be underneath it now I cut the sealant and it is accessible again, you can hardly see it!
Can't you drill a hole for a suction tube to go through so you can suck up the water with a pump?
What I'm trying to say is that there is always a solution.

Mvg,

Pascal.

 

[Pascall]

Thank you. I have seen these articles and they look good. In my case, it will not work.
There is no access in this bilge area and there is no way to install anything there. The bilge is filled with lead bricks, which are very heavy.
Also, the water accumulation is not significant, but it is enough for rust development. That is my concern.

I also had to move 500 kilos of lead under the floor, which is also the reason why I sawed the floor open, pffffff......

Mvg,

Pascal.

 

[LeoKa]

This might work.

 

[LeoKa]

I also had to move 500 kilos of lead under the floor, which is also the reason why I sawed the floor open, pffffff......
Mvg,

Pascal.

Yes, I also cut up the floor where I could. To access the area in question would require me to take apart my queen bed/frame and disassemble my 3 tank fresh water reservoir, including piping. I do not want to do that. It will be easier for me to blow air into this inaccessible area.
The lead bricks in my case are huge. I could not even move them with a pry bar. Forget about lifting them.

You did a nice job there. Your hull is steel?

 

[LeoKa]

Or this.

https://www.homedepot.com/p/Vornado...vanced-Safety-Head-Tilt-EH1-0181-17/316321825

 

[Pascall]

Yes, we have a steel hull and know the problem of condensation in winter.
We have an air dehumidifier in the winter and when we come back on board after a week's absence, everything is dry.
The condensation occurs when the water temperature drops below about 50 degrees Fahrenheit, above which we have no condensation.

 

[Pascall]

I think it's a temporary solution if you're blowing warm air under the floor.
You are going to increase the temperature under the floor, which will lead to a larger temperature difference with the outside, which will eventually result in more condensation when the airflow stops.
Is there no possibility to suck up the water?

 

[LeoKa]

I think it's a temporary solution if you're blowing warm air under the floor.

Is there no possibility to suck up the water?

No. Only small sections are accessible, like I said earlier. To dry this area out, only air blow can be considered.
I understand your point about the temp difference creating the condensation, but the hull wall is dripping and slowly accumulating into the bilge. I have to heat this area, because this is where I sleep. Even though the temp here is between 50-60F that is enough for the dripping. I don’t mind the cold cabin for sleep, but rust is a problem for me.

I think my only workable solution is to evaporate the accumulated water and suck the humid air outside with the duct system.
Dehumidifiers work to a certain extend and in small air mass. I have two of them and I tried to rely on them, but did not work. I mean not enough drying.

 

[Bmarler]

My last live aboard boat was steel. I didn’t have condensation issues with it, it was a very dry boat.
I used an espar forced air for heat, drawing in outside air. The duct ran under the floor, in the bilge area, un insulated. There were two 4 inch Nicro vents in the high point of the boat, the wheel house.
The espar would ensure a slightly pressurized interior and lots of air exchanges, with the moist air exiting the wheel house roof. Worked well for me.

 

[hollywood8118]

Get a better dehumidifier, one designed for a crawlspace. Heat will make it worse. Warm air holds a lot more water than cold air. You can get a commercial dehumidifier that pumps itself out and will remove about 12 gallons ( yes 12 gallons!) a day for under $ 800.00 that will work fantastic and last. I currently have 2, one with almost 4000hrs on it that works just as well as the new one we just got. When you get the relative humidity down around 40% that boat should dry up. You will need to move a little air into the inaccessible areas to assist those spots in drying.
Oh, get a get of ear plugs or get used to the sound of the units making your world dry. Do not confuse these units with those countertop things home depot sells, its like comparing hamburger to prime rib.

Hollywood


https://www.amazon.com/Industrial-C...&qid=1706974696&sprefix=aloair,aps,781&sr=8-8

 

[rslifkin]

Inside vs outside temperature will have no effect on condensation. It's strictly a matter of dew point vs hull temperature. If the interior dew point exceeds the hull temperature, you'll get condensation.

The best way to avoid condensation is to get access to that space, get it dry, and insulate the hull. If you can't do that, then interior humidity needs to be lowered by some method. Warm air blowing across the hull may help a little bit, but unless you're exchanging with outside air to lower the humidity inside the boat, it won't do a lot (as the hull is still cold enough to condense water out of the air).

 

[Lepke]

I spent many years on steel boats and ships. The key to maintaining dry areas is first have enough ventilation of the hull to rid excess moisture. Then draw out air from areas where moisture accumulates. Let dry air in the boat find its' way onto the area.
On ships we had forced ventilation in and out. Incoming air passed thru a heat exchanger. No dehumidifier and no moisture problems. On boats, a diesel heating system that used inside air for combustion. Insulation was spray foam covered with plywood and fiberglass. Steel was either protected by zinc spray or proper paint systems.

I have a wood boat now and have bilge blowers running at very slow speed constantly drawing out bilge areas. I use a rheostat to slow the bilge blowers. I can heat with diesel, wood or wood pellets. Mostly wood pellets in the winter and cook on a diesel stove. My boat is dry and smells like a house.

 

[Delfin]

I sprayed a sound deadening compound on all Delfin's interior steel, then glued 1/4" acoustical cork over the steel. Zero condensation, ever.

Given the difficulty of access, I'd insulate the areas I could reach with cork, then spray the more difficult areas with something like the below. The key is to get a few mils of thickness.

https://www.acousticalsurfaces.com/coat-of-silence/coat-of-silence.html

 

[LeoKa]

I used an espar forced air for heat, drawing in outside air. The duct ran under the floor, in the bilge area, un insulated. There were two 4 inch Nicro vents in the high point of the boat, the wheel house.

Yes, I would to build something like this, too.
Was the Espar diesel, or electric?

 

[LeoKa]

Oh, get a get of ear plugs or get used to the sound of the units making your world dry. Do not confuse these units with those countertop things home depot sells, its like comparing hamburger to prime rib. /QUOTE]

Wow, that is some serious equipment! I am sure it would work for me, too. The budget is a bit tight these days, so it has to wait.
I surely understand your point and I envy you having two of these... lol

 

[LeoKa]

The best way to avoid condensation is to get access to that space, get it dry, and insulate the hull. If you can't do that, then interior humidity needs to be lowered by some method. Warm air blowing across the hull may help a little bit, but unless you're exchanging with outside air to lower the humidity inside the boat, it won't do a lot (as the hull is still cold enough to condense water out of the air).

I cannot access those hidden areas, unless I take apart and remove everything in the cabin.
The outside air these day here in the PNW is very humid already. I am trying to work out something with the duct system and a dehumidifier.

 

[LeoKa]

Then draw out air from areas where moisture accumulates. Let dry air in the boat find its' way onto the area.

I have a diesel furnace in the salon and a duct going down to the bilge, taking the accumulated warm air from the ceiling next to the furnace. This is a slow air flow and cools off completely at the end. It goes through the ER and only 3" OD. For long time now, the floor in the cabin is removed and I use a portable air blower to push air under my bed to dry the bilge sometimes. Like I said, this is not enough.
Based on the replies, it seems that blowing hot air under my bed will not help, or make it even worst. It seems that a stronger, under the floor, air blowing could move the moisture out of this hidden area.
I am almost done with the duct sucking air out of the other end of this bilge section and that takes the air outside directly. This will not be hot air, as I have planned earlier. I was wrong about this, I think. The key is a strong air flow, even if it is not warm air.
Now I need to install a blower below the floor, so I can close in everything and be able to walk around my bed again.

 

[LeoKa]

Given the difficulty of access, I'd insulate the areas I could reach with cork, then spray the more difficult areas with something like the below. The key is to get a few mils of thickness.

I am sure it is a good method. I wish I could. To do this, I would need to completely break down the cabin and empty it out and treat it. That is just not possible to do. At least not for me.

 

[Lepke]

Most people, especially in cold climates don't change enough air. They don't have enough heating capacity and have their boat closed up tighter than a virgin. I'm on a river near the coast and the humidity outside in rain or fog can be over 90%. Yet my inside humidity is usually about 40% and I'm venting bilges 24/7. Somehow that outside moisture doesn't carry over to an already dry boat.
Many times in winter my inside humidity gets below 35% and I have to run a tea kettle to put moisture back in.

 

[klee wyck]

Listen to Lepke.
This is probably best solved in your case, as you describe it, by increasing heating capability.

Condensation or not is a triangulation between temperature, relative humidity, and dew point. Warm air can hold much more water in suspension than cold air can. If you take that very damp 35 degree/85%RH outside PNW air and heat it to 80 degrees, it holds the same amount of moisture at that higher temp in terms of weight but falls to a much lower relative humidity and dew point since warm air can hold that moisture until you exhaust it.

Warm air can possess more water vapor (moisture) than cold air, so with the same amount of absolute/specific humidity, air will have a HIGHER relative humidity if the air is cooler, and a LOWER relative humidity if the air is warmer.

Turn the heat up until it is so hot in there that you need to open some windows. The boat will dry out. You will need to drive that warm air into the spaces that are condensing currently. Too bad the vessel was not more well-conceived in terms of coating and insulation, but I expect adding more heat and make up air will solve your issue without major reconstruction. (Do not heat with propane/gas as this will add moisture.)

 

[Bmarler]

Yes, I would to build something like this, too.
Was the Espar diesel, or electric?

The heater was a d4 airtronic diesel. Even on the coldest days, I didn’t feel any lack of heat as a result of using outside air.
The boat I’m on now is glass hull, and I have hydronic heat. No outside air coming in. Lots of condensation on cold days. I have to find a solution for this one too.

 

[LeoKa]

The boat I’m on now is glass hull, and I have hydronic heat. No outside air coming in. Lots of condensation on cold days. I have to find a solution for this one too.

My heating is a diesel furnace (Refleks, made in Denmark). It has a coil inside, where the water circulates. I have heating hoses going down to the cabins and shower, where I have mounted radiators. Two pumps doing the circulation, one in each direction.
It works pretty well and the furnace is just perfect. However, there is no outside air involved. Interestingly, the salon, where the furnace is, fairly dry when the furnace is on. Without it, my windows are dripping. Of course, less heat accumulates down below, particularly in my cabin, where I sleep. The forward cabin and the shower does not warm up much, unless I run the furnace full speed. ($$$ diesel).
I am not sure, how could I incorporate outside air into this setup? The first duct is in place and functioning and pushing some warm air into the bilge under my bed. The flow is very weak, but it is coming out. Obviously it is not enough to dry up anything. I am installing the exit air part of ducting now, which will pull the air out from below and push it outside at the top of the boat. It will use quiet fans, so it is possible that I could run it 24/7. It will certainly help, but I want to create more turbulent air at the lowest part of the bilge, where the moisture sits.
Based on the replies, I do not know, if I should create high blow hot air, or high blow regular temp air, into the bilge. Certainly high air flow will start the drying.
Finding a heating air blower is not easy, unless I buy a commercial version. Not only it is pricey, but I have very limited space in the area, where anything can be installed.

 

[klee wyck]

My heating is a diesel furnace (Refleks, made in Denmark). It has a coil inside, where the water circulates. I have heating hoses going down to the cabins and shower, where I have mounted radiators. Two pumps doing the circulation, one in each direction.
It works pretty well and the furnace is just perfect. However, there is no outside air involved. Interestingly, the salon, where the furnace is, fairly dry when the furnace is on. Without it, my windows are dripping. Of course, less heat accumulates down below, particularly in my cabin, where I sleep. The forward cabin and the shower does not warm up much, unless I run the furnace full speed. ($$$ diesel).
I am not sure, how could I incorporate outside air into this setup? The first duct is in place and functioning and pushing some warm air into the bilge under my bed. The flow is very weak, but it is coming out. Obviously it is not enough to dry up anything. I am installing the exit air part of ducting now, which will pull the air out from below and push it outside at the top of the boat. It will use quiet fans, so it is possible that I could run it 24/7. It will certainly help, but I want to create more turbulent air at the lowest part of the bilge, where the moisture sits.
Based on the replies, I do not know, if I should create high blow hot air, or high blow regular temp air, into the bilge. Certainly high air flow will start the drying.
Finding a heating air blower is not easy, unless I buy a commercial version. Not only it is pricey, but I have very limited space in the area, where anything can be installed.

.

You are fine there. The diesel furnace is combustion so it requires an air source. Usually these are low in the boat and often in the engine room which is almost always vented providing the air source. As long as you put that heat out low in the boat and then exhaust the warm air somewhere high in the boat, significant moisture will leave the boat with that warm air.
Yeah, burning that diesel will be expensive, but not as expensive as a chronically wet bilge in a poorly coated steel boat.
Pick your poison, no free lunch.

 

[LeoKa]

.
Pick your poison, no free lunch.

I love free lunch....
Understand you and I am working on the duct to pull air outside from below.
I also put in place a decent dehumidifier. Lesson learned.
All I want is a dry bilge, when I finally put the floor back.

 

[Bmarler]

If you decide to install a heated air supply, the Chinese knockoff heaters are really inexpensive. The fuel cost is not insignificant though.
I think my previous success at the dry bilge had much to do with air exchanges, using outside air for the heater pressurized the interior of the boat, forcing air out any cracks and the big vents up top.
I only ran that heater when I was on the boat. I left small electric heating units running when away or sleeping.
I think using fans to draw air out will bring outside air in any cracks or holes, making for a drafty feeling interior.

 

[LeoKa]

I think using fans to draw air out will bring outside air in any cracks or holes, making for a drafty feeling interior.

My diesel furnace is very efficient and economical. No wonder they are not cheap. However, I am guilty of not running it 24/7. I can handle colder temps in the boat, particularly for sleep. It seems, this does not help my moisture management, at all. Also, I did not have any air exit built-in for drying. Yes, the air would escape through cracks and gaps where it can, but that is not enough to manage the condensation. Now I know that heating should run more, or at least to maintain warmer temps inside and the air below needs to be removed to improve circulation. This air pull out will be installed today and put to work. The dehumidifier will run all day from now on. I also plan to install an in-line fan into the critical bilge area, to move that moist air around above the hidden corners. It will not be perfect, but that is the most I can do, without taking apart half of the boat's interior.