Ventillation of the Tomcat's enclosed areas

[rogerbum]

Tomcat owners,

There has been some previous discussion about condensation in the sponsons below the berth and in other areas of the boat. When I store the boat for extended periods of time (say 1 month), I leave a heater on inside the cabin and that keeps the cabin dry but many of the other areas of the boat stay moist and there is considerable growth of mold/mildew in the sponsons (both fore and aft). So, I'm looking for ways to provide active ventilation to these enclosed spaces. In particular, I'm looking for ways to move air when I have 120v available as the boat is usually connected to shore power when I'm not fishing (or when it's on the trailer). Given that the aluminum fuel tanks are also in these enclosed areas, I'm also thinking it would be a wise investment of time and money to do what I can to help keep them drier.

For the area under the berth, I'd like to put a fan/vent combination on the vertical space near your feet just before you crawl into the berth. There's several inches of fiberglass face there that forms the aft end of the enclosed space under the v-berth. If I could draw air from under the berth and exhaust it out the aft end of this surface, I could then provide some venting under the mattress near the bow. With the hypervent I have under the mattress, the air flow would then be, under the mattress, into the sponsons and back out the the aft end of the enclosed area. I'm hoping to find something like a residential toe-kick electric heater that would not only draw air from under the berth but that would also provide heat when on shore power. At present, I use a space heater to provide heat while on shore. So far, the residential toe-kick heaters I've found appear to draw both draw cold air and exhaust warm air through the front. I may be able to modify one of these to draw air from the back or side of the unit.

Since the primary goal is to move air from under the berth, heating is not absolutely necessary. Hence, I'm also looking at floor register fans that could be flush mounted to the surface. The downside to these is that most are designed to only turn on the fan if there is airflow through the register (driven by a furnace or aircon). Hence, I'd have to modify the electrical setup of these to achieve what I want.

So for venting the berth, does anyone have any ideas/suggestions/sources of products that might do what I want?

For the aft end of the sponsons, I'm less clear on how to provide ventilation. I'm thinking about buying additional hatch doors for the transom hatches and putting in computer or bathroom style vent fans. I'd keep the hatch doors in my garage and just swap them in for the winter. At a bare minimum, I need to add additional passive venting to the sponsons towards the stern. When I pull out the the coaming boxes on the gunnels, it's amazing how much mold/mildew is behind there. So again any ideas from the crowd to improve ventilation back there would be appreciated.

[Beflyguy]

Hi Roger,

I have also felt the need for more ventilation, although when I have water in the front sponsons it seems to be from rainwater coming in from places unknown. I purchased some additional vents to install on the top of the coaming boxes. The passive venting there is ok but the one vent per side is not enough I think.
I did install a solar vent over the chain locker that I am going to convert to 12V. I don't think it helps with the sponsons necessarily but I had a hole to fill after installing the windlass and I figured venting that area would help dry out the rode and vent the berth. I don't think air can get there from the sponsons but I might consider putting vents in so that air can flow through.
I am fortunate at this point to be able to store the boat in a nice big garage space where I can just open all the hatches and dry everything out.
I think as you said that airflow, not necessarily heat is the key to drying out things so I would try to move some major air, even if just as needed.

[BrentB]

Would a bilge blower work?
http://www.replacementboatparts.com/3bilgeblower.aspx

[thataway]

I would go with computer fans for you ventilation. You don't need the massive amount of air that a bilge blower moves; just circulation. It will be interesting to see if this really helps or not. I didn't have problems with the forward areas, but kept the boat AC or with a marine dehumidifier in the winter. Aft there was some build up over the years. Probably a good rub down with chlorox periodically would help--along with the computer fan vents.

[hardee]

Roger,

You may have already considered this, or it may not fit, I'm not sure.


WEST MARINE
Air Dryer with Fan, Dehumidifier

Air Dryer with Fan, 110V AC 7867518 9406WM-ABX In Stock
Save $14.60
Reg. $72.99
$58.39

I have two of them and have found that they keep the 22 Cruiser moisture free through the winter storage period. They do a slight warming and a low volume flow continuously, drawing 90 watts.

Harvey
SleepyC

[rogerbum]

So I've been making some progress on adding active ventilation to the area under the berth. Since I'm usually at a marina on shore power or on the trailer at home hooked to power, I decided it would be better to have a fan that ran on 110V. I don't really need the fan to run when I'm out fishing for the day. I looked around and settled on a fairly low volume fan designed for home use. This is a "booster fan that is designed to go in 4" duct work. I built a mount for it from some left over decraguard marine plywood. I attached it with 3 stainless steel brackets. The brackets are screwed to the mount and riveted to the fan with stainless rivets.


This will mount behind the toe kick area under the berth. I used a 4 1/8" hole saw to make a cutout in the toe kick. That area is cored with balsa.



A vent will get mounted in that hole.


And the fan assembly goes in behind it.


Now I have to seal up the core and do a little shimming to get the fan lined up exactly. Then the fan will get mounted with some 4200. Some foil duct tape will seal it all up. For now, I'll run an extension core to it. Eventually, I'll wire in a switch and wire it into the 120V system. I also need to install a couple of flat vents in the berth area under the hypervent and mattress (the hypervent will allow air to flow under the mattress).

[c-ness]

Nicely done. I can envision dry!

[Sea Wolf]

Not only will the ventilation keep the berth dry, but could be useful to heat the berth and it's occupants in the winter, and cool it/them in the summer.

With the right ducting, could be a real climate control feature.

Joe.

[Captains Cat]

Great job Roger! Wanna open a Right Coast installation facility?

Charlie

[Ted Osborne]

I use a fan like the Wesr Marine one that Harvey has (you also need a small amount of heat) and be sure and leave all the drawers and doors open. Never have had a problem. Roger, your nice setup should be ample to get the air movement you need.

[rogerbum]

More work on the ventilation project yesterday and today. I added the vents under the mattress. I bought some flat, stainless steel vents that are 3.25" in diameter and about 1/8" thick. To install them, I bought a 3.25" hole saw and a 2.5" hole saw. I located where I wanted to place them and then used the 3.25" hole saw to remove about 1/8" an inch of gel coat.



I then took my router with a 1/4" bit set to a depth equal to the thickness of the vent. With that I routed the fiberglass down between the outer edge and where a 2.5" hole would later be cut. I then cut the 2.5" hole.



After the holes were cut for two vents, I undercut the balsa and filled it in with epoxy. Then I glued the vents in with 4200. The routed depression I cut allows them to sit flush with the gelcoat.



Here's the final view (a little yellow with my cel phone cam in low light). This is prior to gluing the vents in and of course I straightened the vent holes to run parallel to the front bulkhead.



Now I just need to permanently mount the fan base and wire in the 120V with a switch installed someplace convenient. With this arrangement, air will get drawn under the mattress through the hypervent, then through the vents, into the compartment below the berth and out the toe kick in front of the berth. That should keep things plenty dry.

[thataway]

Nicely done and illustrated! It will be interesting to see how much air flow you get thru the hyper vent. Great idea!

[Sunbeam]

Yes, nice work on those vents and thanks for showing how you did them.

[redbaronace]

Can you post a follow up as to how this is working as a solution. Im thinking it would be a good mod for me as well.

[rogerbum]