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lenm

Ocracoke 20 in OZ

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Happy new year to all.

 

Some update pics..

Local regulations here require a 'builders plate' for vessel registration - which required me to engage a marine surveyor.

Also, a condition/integrity certificate (for future insurance purposes) and buoyancy (going with 'Level' category flotation rather than 'Basic').

 

Happily she has passed 1st inspection!

 

Taking my time to make sure everything is well and truly 'waterproof' such as transitioning any penetrations/screw holes to solid fibreglass..

 

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Its nice to finally have the sub floor glassing finished -  seemed to take thrice as long as I initially anticipated. SMcormick did warn me about this though :-)

 

Discovered a great epoxy product for finishing the bilges.   It flows/levels out nice and even and has 100% opacity with a single coat.  Application is with a regular paint brush.

 

Started shaping the foam buoyancy  - a Neolon type foam as recommended by surveyor - a closed cell foam with chemical resistance and fire retardant properties.

I cut the edges in a corrugated pattern to help promote air circulation around the foam and compartment ventilation.

My current boat seems to get a lot of condensation and water vapour in the underfloor compartments.

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It is my understanding that foam-filled chambers promote rot more than sealed empty ones.  Have you discussed this with Graham?

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I like your ".. cut the edges in a corrugated pattern ..."  From years of repairing fiberglass boats, I learned that moisture almost always manages to find a way under the floor. Poured in place foam traps the moisture where the foam eventually breaks down where it contacts the hull. The best way to prevent problems is to cut block foam to fit, Even better is with the edges "corrugated" as you've done. Then be sure the compartments are ventilated. Even sealed, empty compartments will allow moisture to somehow get in, but at least they don't trap it against the surface. Be sure to seal the backside of the floor (sole) thoroughly, too, before you install it.

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Hi Thrillsbe,  as you mention, possibly a foam filled chamber is more prone to damp condition (and hence rot) than an empty one?

Unfortunately air filled chambers do not qualify as buoyancy over here (the authorities want foam in certain quantity and location)

 

Thanks Chick for your thoughts.

Regarding your comment about ventilation are you referring to limber holes or inspection ports? 

Personally I am a bit reluctant towards sealed compartments which are inaccessible and un-inspectable. Just don't know what's going on in there. Would it be outrageous to put an inspection port on every chamber somehow? And possibly 'vent' after each trip?

Would need to be done carefully so as not to detract the look of the deck.

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16 hours ago, lenm said:

Hi Thrillsbe,  as you mention, possibly a foam filled chamber is more prone to damp condition (and hence rot) than an empty one?

Unfortunately air filled chambers do not qualify as buoyancy over here (the authorities want foam in certain quantity and location)

 

Thanks Chick for your thoughts.

Regarding your comment about ventilation are you referring to limber holes or inspection ports?  

Personally I am a bit reluctant towards sealed compartments which are inaccessible and un-inspectable. Just don't know what's going on in there. Would it be outrageous to put an inspection port on every chamber somehow? And possibly 'vent' after each trip?

Would need to be done carefully so as not to detract the look of the deck.

Foam is required here, too. I leave generous sized holes through the bulkheads that separate compartments, limber holes at the bottom corners, and at least one hatch open to the outside. A screw out plastic hatch is fine. It's also good to have a transom drain that any water can drain out of. I always keep my boats on trailers, so I can remove the transom drain plug and open the hatch(s). Anything to get air flow.

 

The USCG requires "upright and level" flotation. Placing all of the foam spread across the bottom tends to make the boat unstable when it is flooded. It is prone to being capsizes in the waves. I built fiberglass boats for a living and had to have them tested to be sure that they complied with the flotation standards. I found that I needed to leave a section down the middle of the boat without flotation. There was plenty of room left on either side for the amount of foam required to meet the standards. A benefit of this was that it left the area most prone to water penetration free of foam that would otherwise block drainage and ventilation. It's also good to add foam under the deck to help with upright flotation if you have room for it. A book could be written on this subject, but I think this gets the idea across.

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Thanks Chick, you have me sold on ventilation.

I am supposed to place flotation as shown below for certification.

This configuration seems to be similar to how you have described.

flotation plan.png

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