moisture problem inside your boat and want to fix it?

[Sumner]

A little late to this discussion but I have been able to leave the boat in Florida for 3 years now with no mold problems using only natural ventilation. The following is a quote from the mod page on my web site:

Ruth and I bought the Endeavour in the spring of 2011 and worked on her a little and left the boat in the yard closed up until the next spring when we returned about 8 months later. There was some slight whitish mold starting to form inside and we wiped the whole inside of the boat down.​

While we were there I build the covers below that go over the hatches while we are on the boat in the yard and while gone. They are nice even when we are there as we can leave the 3 hatches open 24/7 since they are screened. When we left in the summer of 2012 we left the covers on (tied to the inside of the boat) and the hatches open. We again returned about 9 months later (2013) and no evidence of mold at all. ​

Remember the boat is in the yard on the west coast of Florida so all results are from there. Also the boat takes on some rain water and there is always some water in the lowest part of the bilge that area wise is about 18 X 24 inches. The pump there is connected to a battery/solar panel so keeps the bilge at least that dry while the boat is there but still some water all the time.​

Next after working on the boat in 2013 we left and I didn't return until January of 2015, 18 months later. Again no evidence of mold at all and I was worried there might be some. So in this situation natural ventilation with the hatch covers has resulted in no mold in an area where many complain of it.​

Here are a couple pictures of the hatch covers I made....

....above without the rain shields yet in place... and ...

... one with the rain shield..... and a link to the construction and use of them with more pictures .....

http://1fatgmc.com/boat/end-1/endeavour-outside-mods/page-3.html

This has worked very well where the boat is, can't say for other parts of the country or another boat. As mentioned above while living/working on the boat another advantage is being able to leave the hatches open night/day with no bug problems since they are screened. If the boat ever gets back in the water the hatches will of course be left on land and replaced with screened/canvas ones while on the water,

Sumner

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[Tom Conatser]

Ok quick question. I am purchasing a Catalina 27 however it's in Alaska and I'm in Washington. I have looked over catalina down here with the same configuration but I left my tape measure at home, does anyone have a good guess as to the total area I side the cabin that can be insulated. Like deck/ roof v berth walls behind the benches etc. I'm planning on insulating the whole boat frugal mariner style only I will be using a bit heavy glue and finishing in cedar. I'm just curious how many square feet I will need. I have a pretty good idea on the deck but it's the rest of the boat. I can't find a good diagram of the profile but I have the grid top view. If anyone has ever taken the time to figure this out I would love to know what the final equation is. My guess is about 380 square feet that's bullwarks and ceiling even in the stern berths. Anyway I just joined this forum and although I have never sailed a day in my life i grew up on a fiberglass fishing boat in se alaska so I'm not an idiot when it comes to glass boats. It's going to be an apartment at least till next year I'm hoping to purchase one of those drop in diesel replacement motors out of England. It had a rusty blob that used to be an atomic 4.

 

[centerline]

Ok quick question. I am purchasing a Catalina 27 however it's in Alaska and I'm in Washington. I have looked over catalina down here with the same configuration but I left my tape measure at home, does anyone have a good guess as to the total area I side the cabin that can be insulated. Like deck/ roof v berth walls behind the benches etc. I'm planning on insulating the whole boat frugal mariner style only I will be using a bit heavy glue and finishing in cedar. I'm just curious how many square feet I will need. I have a pretty good idea on the deck but it's the rest of the boat. I can't find a good diagram of the profile but I have the grid top view. If anyone has ever taken the time to figure this out I would love to know what the final equation is. My guess is about 380 square feet that's bullwarks and ceiling even in the stern berths. Anyway I just joined this forum and although I have never sailed a day in my life i grew up on a fiberglass fishing boat in se alaska so I'm not an idiot when it comes to glass boats. It's going to be an apartment at least till next year I'm hoping to purchase one of those drop in diesel replacement motors out of England. It had a rusty blob that used to be an atomic 4.

Personally, even for the location of alaska, where i have spent some time myself, i think adding insulation is the wrong path at this time... i explained why in your other post about the subject.... my reason for saying this is that to prevent condensation, you need ventilation, not insulation.

Some may disagree or ask why, and the answer would be, because of the temperture differential between the inside and the outside, and a vapor emitting object inside... this may be a human body, a cup of water, a open heating flame, a damp/wet bilge, ect...

 

[centerline]

I wish our outside air was drier. Currently it's at 85% humidity. And that is normal in my area (PNW) for this time of the year. Ventilation means drawing in this wet moist air into my cabin. I do not want moss growth in my cabin (natures way of capitalizing on our rain forest ecosystem).

85percent is reasoably dry air... (it will be drier in your house at home because of good ventilation and a good heating system), but not inside your boat... or you wouldnt be wishing it was drier inside your boat.

if you jave ever noticed, you never see outside objects with condensate on them... as long as they are covered, rhey are always dry, in any enviroment, no matter if the humidity is 99%, in any weather.... its because even though some enviroments may be much more humid than others, with good ventilation we will never collect condensate or moisture in any measurable amount....

Some places are naturally extremely humid... too humid for comfortable human habitation, so then a mechanical dehumidifier can be used to dry the air....

 

[Tom Conatser]

Personally, even for the location of alaska, where i have spent some time myself, i think adding insulation is the wrong path at this time... i explained why in your other post about the subject.... my reason for saying this is that to prevent condensation, you need ventilation, not insulation.

Some may disagree or ask why, and the answer would be, because of the temperture differential between the inside and the outside, and a vapor emitting object inside... this may be a human body, a cup of water, a open heating flame, a damp/wet bilge, ect...

i understand venting the moist air seems a quick fix but in Southeast alaska the relative humidity is usually 90%+ so as long as a surface is cooler than the ambient temp then condensation will occur. withought being able to maintain a warm enviroment venting will only allow moist air into the boat. The only way i know how to raise the surface temp of an un-insulated boat hull is to insulate it from the cold outside. i plan on installing some small vents with fans and i have a lead on a diesel stove. once i get the stove installed i already own one of those little fans that sits on the cook surface and move the air around. i know it will be easier to keep a warm boat dry than a cold shell. i have seen a Catalina over on the coast where the owner insulated it just like i plan on it and he said he has no condensation problems unless he is boiling water.

 

[centerline]

i understand venting the moist air seems a quick fix but in Southeast alaska the relative humidity is usually 90%+ so as long as a surface is cooler than the ambient temp then condensation will occur. withought being able to maintain a warm enviroment venting will only allow moist air into the boat. The only way i know how to raise the surface temp of an un-insulated boat hull is to insulate it from the cold outside. i plan on installing some small vents with fans and i have a lead on a diesel stove. once i get the stove installed i already own one of those little fans that sits on the cook surface and move the air around. i know it will be easier to keep a warm boat dry than a cold shell. i have seen a Catalina over on the coast where the owner insulated it just like i plan on it and he said he has no condensation problems unless he is boiling water.

Ive spent a lot of time in alaska, and believe it or not the average humidity there is much lower there than it is on the gulf coast.
It doesnt matter what the relative humidity is... ventilation is the most affordable answer to prevent CONDENSATION.... when is the last time you have seen condensation in a barn, or an outhouse, or any other structure that has no heat but has good ventilation?.... the atmospheric humidity is the same as it is surrounding your boat, its just that the boat interior is enclosed WITHOUT good ventilation...

 

[Tom Conatser]

Ive spent a lot of time in alaska, and believe it or not the average humidity there is much lower there than it is on the gulf coast.
It doesnt matter what the relative humidity is... ventilation is the most affordable answer to prevent CONDENSATION.... when is the last time you have seen condensation in a barn, or an outhouse, or any other structure that has no heat but has good ventilation?.... the atmospheric humidity is the same as it is surrounding your boat, its just that the boat interior is enclosed WITHOUT good ventilation...

ok well I'm southeast Alaska there is a town called sitka. Located on Baranof island. Which happens to be in the Tongas national RAINFOREST. So while I will admit the Pacific Northwest is a wet place the town of my birth is wetter. The reason that you don't see condensation on objects that are outside is that there is no or little temperature variations. And Barns have condensation in the mornings and at night because of these variations. Boats have a bigger problem because they are constantly facing a temp variance between the air and the ocean. Now in Sitka the water isn't that cold it's actually warmer than in Washington because we have the Japanese current running around our island. Even still it's enough to have a warm hull and a cold deck in the mornings. Now as long as I can increase the temperature of the surface interior of my boat condensation will not occur. Like a heated mirror In a bathroom. Venting is still needed cause the moisture has to go somewhere but in a town where if you build a brand new house and turn the heat off it will have mold in a month vented or not you can't just vent. As the Suns rises and falls it heats and cools the boat. As long as a surface is colder than the ambient air water will condense so long as the humidity is high. Did I mention my town is in a temperate rainforest? If you google it it made me laugh it said "no dry season" so as much as I was looking for advice on what the interior surface are of a Catalina 27 I do appreciate the thought that I don't need insulation but sadly if you want a dry boat living in a coastal rainforest I will need insulation heat and venting.mid you do know the area dimensions that are accessable I would love to know as I am currently putting together my materials for when I head back north to start the remodel of my new boat.

 

[centerline]

ok well I'm southeast Alaska there is a town called sitka. Located on Baranof island. Which happens to be in the Tongas national RAINFOREST. So while I will admit the Pacific Northwest is a wet place the town of my birth is wetter. The reason that you don't see condensation on objects that are outside is that there is no or little temperature variations. And Barns have condensation in the mornings and at night because of these variations. Boats have a bigger problem because they are constantly facing a temp variance between the air and the ocean. Now in Sitka the water isn't that cold it's actually warmer than in Washington because we have the Japanese current running around our island. Even still it's enough to have a warm hull and a cold deck in the mornings. Now as long as I can increase the temperature of the surface interior of my boat condensation will not occur. Like a heated mirror In a bathroom. Venting is still needed cause the moisture has to go somewhere but in a town where if you build a brand new house and turn the heat off it will have mold in a month vented or not you can't just vent. As the Suns rises and falls it heats and cools the boat. As long as a surface is colder than the ambient air water will condense so long as the humidity is high. Did I mention my town is in a temperate rainforest? If you google it it made me laugh it said "no dry season" so as much as I was looking for advice on what the interior surface are of a Catalina 27 I do appreciate the thought that I don't need insulation but sadly if you want a dry boat living in a coastal rainforest I will need insulation heat and venting.mid you do know the area dimensions that are accessable I would love to know as I am currently putting together my materials for when I head back north to start the remodel of my new boat.

the beauty of owning your own boat is that you can do it how ever you want to.....
there are some of us that grew up without a bank account and so we have learned how to do the same things on a budget that the rich folks can do with money.... and because money always speaks louder than even common sense does, most people choose to believe what they hear from the "influential" group people who have actually spent the money to achieve results and claim that its the only way it can be done, rather paying any attention to those of us that have learned to do it without all the machinery and equipment and associated costs.

think what you will about your wet boat problems and all that you want to spend on it to try and keep it dry, but I will only add that even soaking wet laundry will dry in a damp environment without heat if there is enough ventilation... its really a no brainer and I cant understand why people are so hardheaded and have such a tough time realizing ventilation is the answer..... when they dont have the resources to purchase or power requirements to run a true dehumidifier...

but either way, insulation is NOT the answer to the humidity problem.

 

[Stu Jackson]

centerline's right, again.

http://www.marinco.com/en/products/ventilation

Click on the Global Catalog, or read your West Marine catalog under ventilation.

Our boat has never had any serious issues 'cuz we have dorade vents and leave the aft cabin portlights open. Of course, our climate is different, but the same concept applies. This is discussed also in Extending Your Boating Season in the Online West Advisors under heating/ventilation.

 

[centerline]

Tom,
here you can compare the cost of dehumidifiers that actually dehumidify, rather than the hundred dollar heating models sold at the local boat supply store.... these will work no matter if you have insulation or not, and no ventilation is needed other than a way to dispose of the moisture collected.
they will be what you will need if you want it dry inside but dont want to ventilate.... and you WILL still need heat to be comfortable on the boat.
but, with a true dehumidifier, if you insulate, it can reduce the amount of BTU's needed to keep the boat warm inside.... which is a plus.
the down side is, the cost of purchase and the cost of running it, and only near shore power as the power consumption is considerable in a damp enviroment.

with a good ventilation and a good heating system you can achieve the same results, no matter if you are at the dock or on the hook up some fjord for weeks/months at a time.... and you can still make use the insulation that you have your heart set on, to save on the heating bill...

and again, relative humidity has little to do with it in the colder climates.... here, the relative humidity has been for most of the past two weeks between 93 and 99% (I have an RH indicator on the weather station that reads both inside and outside)... and my boat is STILL dry....

 

[Tom Conatser]

Tom,
here you can compare the cost of dehumidifiers that actually dehumidify, rather than the hundred dollar heating models sold at the local boat supply store.... these will work no matter if you have insulation or not, and no ventilation is needed other than a way to dispose of the moisture collected.
they will be what you will need if you want it dry inside but dont want to ventilate.... and you WILL still need heat to be comfortable on the boat.
but, with a true dehumidifier, if you insulate, it can reduce the amount of BTU's needed to keep the boat warm inside.... which is a plus.
the down side is, the cost of purchase and the cost of running it, and only near shore power as the power consumption is considerable in a damp enviroment.

with a good ventilation and a good heating system you can achieve the same results, no matter if you are at the dock or on the hook up some fjord for weeks/months at a time.... and you can still make use the insulation that you have your heart set on, to save on the heating bill...

and again, relative humidity has little to do with it in the colder climates.... here, the relative humidity has been for most of the past two weeks between 93 and 99% (I have an RH indicator on the weather station that reads both inside and outside)... and my boat is STILL dry....

ok if im living on a boat im breathing on a boat and if im breathing im causing condensation right? so vents ok. but now im cold so im at a dock paying liveaboard so ill use electric heat. well having a heater in a boat with a vent is like trying to run an airconditioner in a car with the windows down. im actually writing this as i lay in my old bunk on my dads 52 ft fiberglass fishing boat. i grew up in an uninsulated focsle and even though we would leave the bow hatch open our bunks would be soaked every morning becaus the ocean was one one side and our breath was on the other. if my dad had foamed the hull inside the foclse this would not have happened. we can argue about condensation till the seaguls choke on irony the question i asked was the interior area of a catalina that is accesable to be insulated. i did not ask if i shoulkd because i have decided too already. and if the interior of a boat is warm condensation will not occur it might get muggy but with no cold surface the moisture cant condense. thos dehumidifiers you guys are talking about are just a refrigerated plat that condenses water out of the atmosphere. so if i keep the inside of the boats surface warm problem is alot easier to solve that 1/16 of glass with the ocean sloshing on one side all day. its the same reason old boat have carpet on the wall it was cheap insulation that resisted condensation because it wouldnt hold and transfer cold. anyway you guys thanks for the input. ill post pics when i am done. i am going with 1/2 in polyethylene foam glued to the hull and ceiling with liquid nails plastic panel adhesive. sealed behind a coat of DRT liqiud rubber to keep the air from getting behind it and then im covering it all with cedar strips 1/8 in by 2 in should look pretty when im don. good lucke to all and happy sailing

 

[Sumner]

......if my dad had foamed the hull inside the foclse this would not have happened. ...............and if the interior of a boat is warm condensation will not occur it might get muggy but with no cold surface the moisture cant condense. ....

I agree completely in this case where he is living in the boat and contributing moisture to the air. Insulation will go a long ways from keeping that air from condensing on a cold hull. It will also make it much easier to keep the boat warm (lower heating costs).

If the boat was sitting there and not lived in then we would have a different situation,

Sumner

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Our Endeavour 37

Our MacGregor 26-S Pages

Our Trips to Utah, Idaho, Canada, Florida

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[Chris Patterson]

I deleted my thought..

 

[centerline]

ok if im living on a boat im breathing on a boat and if im breathing im causing condensation right? so vents ok. but now im cold so im at a dock paying liveaboard so ill use electric heat. well having a heater in a boat with a vent is like trying to run an airconditioner in a car with the windows down. im actually writing this as i lay in my old bunk on my dads 52 ft fiberglass fishing boat. i grew up in an uninsulated focsle and even though we would leave the bow hatch open our bunks would be soaked every morning becaus the ocean was one one side and our breath was on the other. if my dad had foamed the hull inside the foclse this would not have happened. we can argue about condensation till the seaguls choke on irony the question i asked was the interior area of a catalina that is accesable to be insulated. i did not ask if i shoulkd because i have decided too already. and if the interior of a boat is warm condensation will not occur it might get muggy but with no cold surface the moisture cant condense. thos dehumidifiers you guys are talking about are just a refrigerated plat that condenses water out of the atmosphere. so if i keep the inside of the boats surface warm problem is alot easier to solve that 1/16 of glass with the ocean sloshing on one side all day. its the same reason old boat have carpet on the wall it was cheap insulation that resisted condensation because it wouldnt hold and transfer cold. anyway you guys thanks for the input. ill post pics when i am done. i am going with 1/2 in polyethylene foam glued to the hull and ceiling with liquid nails plastic panel adhesive. sealed behind a coat of DRT liqiud rubber to keep the air from getting behind it and then im covering it all with cedar strips 1/8 in by 2 in should look pretty when im don. good lucke to all and happy sailing

Sometimes, even with all the experience and knowledge that one thinks they have absorbed over the years, its difficult, or maybe even impossible to see all that they dont know about some subjects..
And some people will always follow the familiar path of what they do know, however limited it is, rather than accepting a new idea and broadening their horizons...

the bottom line is, condensate is only a byproduct of the problem. the problem is the much "wetter" air in the interior of the boat. its wetter because it will be warmer.
you can have damp bedding, curtains, clothes, food, ect without a drop of condensate ever getting to it. actually when the condensate happens, the air is actually drying itself out. the actual problem is getting better when the moisture comes out of the air.... the question is "how do we get rid of the condensate?"... preventing it is only keeping the moisture suspended in the air, which is contacting EVERY surface within the comfines of the hull.

the best way is a machine that removes the moisture from the air and discards it, and the cheapest and most natural is ventilation.

I have given many examples and reasons for the need for ventilation.
initially I was under the impression with you being a fisherman/fishermans son, that you were fixing your boat up to be live-aboard and also cruise on... I did not realize you were going to be parked at the dock all the time.
that was my reason for suggesting a forced air heater, as it gives heat AND ventilation, very much unlike the electric heater you will use while tied to shore power..... if you ever leave the umbilical, you will be without heat and at the mercy of whatever small amount of ventilation you have to keep things dry, because the insulation just wont do it...


after reading your last post, i realize that you have your heart set on gluing foam panels to the inside of your boat, no matter the reason or the consequences, and although I dont support your reasons of it preventing a damp enviroment inside the boat, I do FULLY support the notion that insulation is good for conserving heat or cold, and that we should be able to do whatever we want within our own space, wherever that may be.

keep in mind that even an ice cooler with 2inchs of insulation surrounding it will develop condensate on the outside of it, IF YOU DONT HAVE ENOUGH VENTILATION SO IT CAN EVAPORATE.

Ventilation is for dealing with moisture/odor problems and insulation is for dealing with efficiency of heating/cooling or sound.

You ask for thoughts about your project in your original post, and I gave you some.... even if its hard to comprehend and it wasnt what you wanted to hear.
good luck with your project...

 

[Tom Conatser]

Sometimes, even with all the experience and knowledge that one thinks they have absorbed over the years, its difficult, or maybe even impossible to see all that they dont know about some subjects..
And some people will always follow the familiar path of what they do know, however limited it is, rather than accepting a new idea and broadening their horizons...

the bottom line is, condensate is only a byproduct of the problem. the problem is the much "wetter" air in the interior of the boat. its wetter because it will be warmer.
you can have damp bedding, curtains, clothes, food, ect without a drop of condensate ever getting to it. actually when the condensate happens, the air is actually drying itself out. the actual problem is getting better when the moisture comes out of the air.... the question is "how do we get rid of the condensate?"... preventing it is only keeping the moisture suspended in the air, which is contacting EVERY surface within the comfines of the hull
the best way is a machine that removes the moisture from the air and discards it, and the cheapest and most natural is ventilation.

I have given many examples and reasons for the need for ventilation.
initially I was under the impression with you being a fisherman/fishermans son, that you were fixing your boat up to be live-aboard and also cruise on... I did not realize you were going to be parked at the dock all the time.
that was my reason for suggesting a forced air heater, as it gives heat AND ventilation, very much unlike the electric heater you will use while tied to shore power..... if you ever leave the umbilical, you will be without heat and at the mercy of whatever small amount of ventilation you have to keep things dry, because the insulation just wont do it...


after reading your last post, i realize that you have your heart set on gluing foam panels to the inside of your boat, no matter the reason or the consequences, and although I dont support your reasons of it preventing a damp enviroment inside the boat, I do FULLY support the notion that insulation is good for conserving heat or cold, and that we should be able to do whatever we want within our own space, wherever that may be.

keep in mind that even an ice cooler with 2inchs of insulation surrounding it will develop condensate on the outside of it, IF YOU DONT HAVE ENOUGH VENTILATION SO IT CAN EVAPORATE.

Ventilation is for dealing with moisture/odor problems and insulation is for dealing with efficiency of heating/cooling or sound.

You ask for thoughts about your project in your original post, and I gave you some.... even if its hard to comprehend and it wasnt what you wanted to hear.
good luck with your project...

Ok well I am used to the net by now. Ask a question and get an opinion instead of an answer. My original question was if anyone had taken the time to measure out the square footage of interior surface of a Catalina 27 so I knew how much insulation to buy. I have politely listened to everyone try to tell me that barns don't have condensation "wow" and that if I just ventilate my tiny floating refrigerated tube I'll be living in then I won't have condensation. I was also told my temperate rainforest isn't as wet as washington which gave my father, he's the commercial fisherman, and I some serious laughter. So I do appreciate everyone's input I hope I never have this much time on my hands but as I am currently no busy I'll walk it thru my reality and basic understanding of atmospheric moisture also known as humidity. I will be living on this boat. First argument is a cat 27 is too small to live on. Having grown up on a commercial fishing boat I can assure you I will have more space to live than I did growing up on my dads boat. Growing up fishing in se alaska on a fiberglass boat I learned a lot of practical knowledge of condensation. No matter if it was 1998 and we had a whole month of sunshine and it was 70 degrees out, that's weird in Sitka ak, we always had to prop the engine room door open to the focsle. Not to vent we always had the bow hatch vented , we needed the heat from the engine room to go into the focsle and dry out our beds. Now on a commercial boat that's running to be from the fishing grounds morning and nights it's akin to having a blow dryer for 2-3 hrs each morning and night to heat up and dry out you stuff. Now if in the off season we forgot to prop up the mattresses or leave a heater in the focsle no amount of venting would have kept that focsle from raining. And I have seen it rain in there the year our heater had quit. Just like a cave with pond in the back any object that has a cooled surface and a surface that fluctuates temperature you will have a condensation reaction. Warm moist air heats cold surface and condensation happens. How can anyone argue that insulating the surface will reduce the thermal transfer between ocean and interior? Yes I understand if I seeel the whol boat air tight and don't vent it I will have moist air. But getting warm air for the moisture to travel on is a lot easier if the boat is insulated than trying to run a heater in an un insulated fiberglass tube. Now my uncle George's boat, also a se Alaska fishing boat, has spray foam insulation against its steel hull. Now steel transfers heat even faster than a glass hull but because the interior surface is usually pretty clos to the air temp he has never had a problem other than when they are running it gets quite hot in the focsle. So in my life I have experianced an insulated boat in southeast Alaska and it was bone dry inside with little or no venting needed. And I spent half of the first 17 years of my life in a boat that always had sweating walls and damp mattresses because we did not have an insulated hull. I have personally witnessed this and yet there are people on here arguing that in my young years all these experiances are not as good as there personnel recommendations. I get frustrated rarely but when I'm not proposing a theory but an experience and someone is trying to tell me I'm mistaken it's frustrating. The water temp in se ak is usually 42-48 degrees. So any day that the atmosphere is warmer than that water will condense on the inside of a boat hull. Venting will only add water without heat. I'm done arguing this point but I will ask everyone who has attempted to convince me I'm barking up the wrong tree to actually look at how a dehumidifier works. Then tell me I'm wasting my time insulating my hull. On a lighter note. My insulation adhesives and electrical system added up to just under 300$. So once completed I will have the most overwired over insulated over heated and over appliances little live abord in Sitka ak. Next year I'll replace the main this year I just need to figure out where to mount a 56 in TV. Thank you all for your feedback even if some of it felt quite demeaning I doubt you all hold your noses up but I've been polite in my responses as much as I can be. It amazes me that every boatyard I have ever been too has a boat somewhere in it undergoing aftermarket insulation. It's hard to believe they are all wrong as well as me.

 

[Chris Patterson]

Tom, you are saying what I've been thinking for a week. Reminds me of the V8 thread......and while I couldn't care less if someone wanted a Caterpillar 3115 turbo in a C22, I am sort of interested in the plan.

For what it's worth, on bottom coatings I've always used length times beam.....and the math works out about right. On my boat being 29, I round the math off to 30 because I'm stooped....so 30 X 8 being about 240 square feet is close. If it were ME....I would use that math.

That and I would agree on everything you've said. In my experience, I see 'dry boats', and 'wet boats', fer instance.....I have a boat that seems to like moisture, and my mates boat right next to mine seems to be dryer. I use a big home model dehumidifier, and he has no use for one, go figure.

Google luck on this Tom. And bear in mind most of us are just bored to tears in the winter and just want to comment on anything. I do..

 

[Maine Sail]

Ive spent a lot of time in alaska, and believe it or not the average humidity there is much lower there than it is on the gulf coast.
It doesnt matter what the relative humidity is... ventilation is the most affordable answer to prevent CONDENSATION.... when is the last time you have seen condensation in a barn, or an outhouse, or any other structure that has no heat but has good ventilation?.... the atmospheric humidity is the same as it is surrounding your boat, its just that the boat interior is enclosed WITHOUT good ventilation...

I see condensation in my barn quite frequently when the temp changes fairly drastically, as it does on the Maine coast... Items that don't change temp in tandom with ambient air simply develop condensation on the surfaces. Ask me why I have to wax/coat my iron saw tables etc... The barn is pretty leaky and what I would consider well ventilated still rapid changes in temp cause condensation to from on items that don't change temp as rapidly...

I am currently working on a boat in a outside barn that is basically open to the surroundings and only really provides a roof and partial sides. When I heat the engine room, even with it open to the atmosphere, condensation forms on anything that does not warm as fast as the air. Nothing I can do about it despite being 100% ventilated...

 

[Gunni]

An understanding of Dew Point would help. Different temperature atmospheres have differing abilities to hold air moisture.

 

[jwing]

An understanding of Dew Point would help. Different temperature atmospheres have differing abilities to hold air moisture.

This thread as been quite entertaining so far! Why do you want to ruin it with an understanding of natural thermodynamics?

 

[centerline]

I see condensation in my barn quite frequently when the temp changes fairly drastically, as it does on the Maine coast... Items that don't change temp in tandom with ambient air simply develop condensation on the surfaces. Ask me why I have to wax/coat my iron saw tables etc... The barn is pretty leaky and what I would consider well ventilated still rapid changes in temp cause condensation to from on items that don't change temp as rapidly...

I am currently working on a boat in a outside barn that is basically open to the surroundings and only really provides a roof and partial sides. When I heat the engine room, even with it open to the atmosphere, condensation forms on anything that does not warm as fast as the air. Nothing I can do about it despite being 100% ventilated...

Mainesail, with all due respect to what you said earlier about keeping the bilge dry, which I agree helps more than any other single thing a person could do, I will only say the following because it can be simply proved...... 100% ventilation can be improved upon with a fan...

and for everyone else....
I would agree there are parts of this world where the atmosphere is so damp, that ventilation by itself still isnt enough to make it a comfortable place for human habitation, and then mechanical means are necessary.
the northern temperate climates arent included in those places, but this seems to be where most people complain of moisture problems in their boats.

if any of you want to purchase a mechanical dehumidifier, and have the capacity to run it while away from the dock, by all means do so... it may be the better choice for your style of boating... and then this thread can offer you nothing, and all you can offer it is to say that your mechanical dehumidifier works better... as long as you can have it plugged in. and I am not disagreeing with you.

but for all the others who dont want to, or cant afford to purchase, or are going to be so long away from enough power to supply the machines needs, that it isnt a feasable, then you are going to have to do it the way it was done before the machines were invented.

ventilation.... it is absolutely the cheapest and most natural way that can be used to keep the interior dry enough to be comfortable and livable... heat will help greatly with the comfort, and allow the moisture to be ventilated away at a much higher rate.

with the modern materials being so much more water tight than the majority of the wooden vessels of the past, we have began to think that if we keep the boat sealed up tight we will never have a moisture problem in side of it... and that is part of the problem. the way we are thinking about it.

I dont think I need to give the definition of ventilation, but it is ventilation that so many "damp" boats lack. wet boats usually have additional issues going on that allow moisture in, and even though some of them have good ventilation, it cant keep up with the influx of moisture from other sources.... they will always be wet, even with a normal sized mechanical dehumidifier.

a fan by itself will cause air movement and if it can move the air to the outside of the space and away from the object that its blowing on, and outside air can come in to repalce it, that will the ultimate in ventilation. the more fan you have, the better the ventilation will be.
in this case it may be ventilating the the engine in the engine room or the INTERIOR of the boat.

if you were to have the fan blow across the engine block, and that air is being carried to the exterior of the hull, the condensate that will be trying to form on the block will be evaporated into the airstream, before it can form a droplet, and carried out of the hull... the same results can be achieved in the interior of the boat, with the air being exchanged with fresh air.... if droplets are still forming then the ventilation isnt good enough.
try it and see... the proof is right there.

and that is the whole point of the post. enough ventilation will dry the boat and it doesnt not take expensive dehiumidifiers and heaters to keep it dry.