any problems with rot building enclosed spaces?

[greatharbor]

i am finishing up a 19' plywood flat bottom skiff and am thinking that instead of floorboards and bilge pump i would lay in a fiberglass deck and make it self bailing. anybody have any experience with what treatments, materials, etc. i might need to deal with the possibility of problems caused by moisture trapped in a small space that won't dry out with exposure to air? also, any thoughts on using red lead vs. epoxy coating in this application?

[Woxbox]

Epoxy. The usual approach is to have deck plates or inspection ports that can be removed to allow for ventilation when the boat isn't in use, as well as to see what's going on in there. That's pretty much assuming the boat lives on a trailer. Is that your plan? Also, more details about the specific design would help. Keep in mind that changes in temperature can change the pressure in an enclosed space pretty dramatically. An airtight space like that, when going into cold water on a hot day, can create a partial vacuum that will suck in water anywhere it possibly can.

[greatharbor]

it's ken swan's nez perce 19 built with meranti plywood. it would live at a dock or mooring six months per year. yes i was thinking of two inspection ports at transom above drain plugs to monitor. both bottom and self bailing deck would be fiberglassed but i have a 19' fiberglass work skiff that has same arrangement and like you say thru condensation or what not there will always be moisture in that dead space ( about 8 " in this case ). am sorting thru all the info on heated epoxy vs. cpes etc. but was wondering if anybody has experience with such an airtight small space in wooden boat construction accelerating the rot process to a very short life span. this is a different situation than even tight bilge spaces behind ceilings in wooden boats which would allow for some release of moisture and the water would more likely be salt rather than fresh. i've never seen or ever heard of it being done, but then again there aren't that many ply boats around here. thanks

[SawmillBrook]

I did research on this when I built my boat, which is similarly constructed. As stated above, I installed 3 deckplates. I remove them after each use to allow the bilge to dry.

Second, I invested in a cotton canvas cover to keep the elements out. Cotton breathes as does the wood. Plastic does not and creates a mini-ecosystem of moisture.

Hope this helps.

A>

[TerryLL]

The underdeck space does not need to be airtight. By providing openings to the underdeck space high in the bow and stern, and under the side decks, you can have a self-bailing sole and a well-ventilated underdeck space.

[JimD]

Nez Perce 19

http://www.swanboatdesign.com/images/gallery/nezperce19-1.jpg

Inside of smaller version:

http://www.swanboatdesign.com/images/gallery/nezperce13.jpg

I always vent airtight compartments. Any size vent is better that nothing. Here's what I have done numerous times:

http://im1.shutterfly.com/media/47b7cf30b3127ccec2c31f3267fc00000010O00CbOGrVu4cMQ e3nw8/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/

I did have serious rot in a floatation compartment of an older kayak I had built that did not have any venting. Can't say for sure if the problem was entirely a lack of venting but it couldn't have helped matters.

[greatharbor]

thanks,

[greatharbor]

thanks, that helps. i didn't see any scupper plugs in snow goose so i assume it doesn't self bail but the condition is the same. the idea of venting for some reason hadn't crossed my small mind but should be easy to do forward because the deck butts to a fishwell bulkhead and from there into an anchor locker. i'm sure i can figure out some inoffensive snorkel for the aft end which would keep the vent high in case somebody forgets to pull the deck scupper plugs ( i know - how could that happen ) i do think it would need a vent at both ends for any meaningful air movement. great idea, cheap insurance. just curious jimd, how did you treat the floatation compartment in the kayak you had problems with?

[JimD]

just curious jimd, how did you treat the floatation compartment in the kayak you had problems with?

Total epoxy encapsulation. The compartment was filled with a styrofoam block. The foam had to be removed as it was wet so quite a lot of moisture got in and I never did figure out where. Could I have been careless and not as thorough as I thought? Maybe. Don't know. I ended up cutting out several square inches of very soggy punky plywood and replacing it. The patch worked, and I had no further problems with the boat. But patching is a time consuming nuisance. A day in the garage instead of on the water. It was a good lesson learned about being meticulous in the first place and leaving a way out for water just in case.