To Vent – or not.

[Nasher]

My Ocean 6.5 ‘The Nashers Revenge’ has a large underdeck void about 6ft long shaped like a wide coffin under the front half of the deck.
I’m sure it’s useful for something, I’ve considered a bladder type fuel tank amongst other things.
It’s sealed both ends by bulkheads and topped off near the bow by a simple hatch, which I’ve never been happy with.
Bearing in mind it’s a commercial hull so was never finished to leisure boat standards, the forming of the hatch was a bit, er rough.

Basically the builders jig-sawed a hole in the deck, screwed a bit more ply underneath to form a lip, then dropped the bit they’d cut out back in the hole with a couple of latches – See pics.

Admittedly it was all well covered in flow coat, but as you can imagine the void collects any water that gets on the deck.
Over the years I’ve tried sealing the hatch all sorts of ways, even resorting to silicone sealant which soon split when we walked over the hatch. It obviously tends to stay damp down there even after I’ve used a pump and sponge on the end of the boat hook to get the water out.

I’m currently fabricating a new hatch cover so it seals properly, more of which in a future thread, but it’s got me thinking if I should vent the void to stop condensation or anything.
The new hatch cover should stop any water getting in there, and will be as easy as the current one to remove for access.
I have the option of putting 1 or two vent grills inside the bottom of the console to allow for air to get down into the void.

Thoughts please?

Ta

Nasher.

[ncp]

I'm rather new to this and have no where near your number of posts...

But, couldn't you seal it with a quality hatch (I have a waterproof hatch from (Freeman Marine Equipment, Inc. ), and then vent to under the console somewhere that won't let the ingress of water.

I would think that a completely sealed area would need to "breath" (i.e. you vent somewhere into the console to be the safest). In racing surfcraft (paddleboards, surf skis, canoes, etc.) the builders tend to put breather tubes in so that the pressure inside and outside of the hull can equalize. Or some builders use a plug with a gor-tex membrane that allows the hull to breath but doesn't allow water in. On the beach it be much hotter that when the board/ski/hull is in the water and when they have a screw in plug, they can actually "pop" and crack the hull.

Note: the plug, below, is just like you would see in a high school chemistry lab, rubber plug, hole drilled through, rubber tubing

[Dhf]

Hey Nasher, I'm looking to fabricate a new bow locker meself, so look forward to seeing ur method of tackling, think the vent's a good idea to, and if you think ur cover looks bad you aint seen mine.
All the best with project.

[Ian M]

Nasher, could you get sufficient access via the console - get rid of the deck hatch completely? Does it go forward to an anchor locker?

[Hightower]

If you're not going to use the void I would just cover it up. If you want to use it then a hatch that will keep the water out is all you will need. My bilge has a small hatch for access and I've got no ventilation in there and I don't get any dampness in there. If you still need ventilation then I wouldn't terminate it inside the console as all your electric equipment is in there. I would run ducting from the floor of the console to outside to isolate any dampness.

[Nasher]

Thanks for your thoughts guys.

Originally Posted by ncp

But, couldn't you seal it with a quality hatch

That would involve spending some money, and wouldn't involve the satisfaction of designing and building the hatch myself.
Besides, Mrs Nasher is happiest when I'm in the garage out of her way so I'm doing it for her

Ian, I like your idea of blocking the current hole up all together and putting the hatch in the console floor, but I'm not sure it wouldn't give me the same access. The only thing I've ever stored down there is a couple of fishing rods when I had to carry them, as I didn't want them floating around on deck and the position of the hatch allowed me to feed them in from one end.
Edit. The anchor locker is seperate at the bow. Some pics at the beginning and end of this thread to explain - http://www.rib.net/forum/f8/ancher-l...ain-31831.html

HT, you are of course correct about venting into the console and the electrics, hadn't thought of that.
One use I may make of the locker once the hatch is more useable is to dump all the wet wet suits, diving gear etc down there at the end of the day rather than use wet bags in the console.

I'll post some pics of my hatch cover when it's finished, but I think the new to plan vent the underdeck space will be a sealed tube up the inside of the console venting half way up the outside - If I bother at all when I've considered it more and asked a couple of 'friendly builders' at the show today.

Thanks again guys.

Nasher.

[chewy]

You could still vent it through the console just run some pipe through it.

I wouldn't worry too much about venting it, if you do need to just leave the hatch off when your finished.
Where does it drain too?

[Nasher]

Originally Posted by chewy

Where does it drain too?

Thats the problem - Nowhere.
The rear of the compartment is a bulkhead with the underdeck fueltank on the other side. with a sealed hatch it will be completely air/water tight.

When rain or water brought on deck gets down there I have to use a hand pump then a sponge on the end of the boathook to get it out.

I've thought about putting some fresh water in there with some detergent and using it as a washing machine for the wet suits on the tow home from devon each year

Nasher.

[chewy]

What access do you have to the bulkhead and tanks?

[Downhilldai]

If you're going to have an airtight hatch and the locker is bone dry, then condensation won't form as there'll be no moisture in the trapped air (in theory ).
As a store for wetsuits, waterskis, ski-ropes, etc, then it's going to be a wet place and while a vent will help it breathe, it's unlikely to dry out completely. Leaving the hatch open will help any damp air escape. If it's fully flowcoated inside, then, there's little chance of any moisture affecting the structure of the rib, but it might get a bit pongy in there!
Also looking forward to seeing the new hatch. I'd have just popped a Bomar or Viking one in there.

[C-NUMB]

I would not make any additional holes, but would went through the hatch when boat is ashore. I blocked the hull in my SR and the trapped space stays completely dry.

The first year there was some moister but this summer it has been completely dry all the time, maybe the hull dried as it was winterizing in a warm garage?

[Nasher]

Originally Posted by Downhilldai

Also looking forward to seeing the new hatch.

Your wish.... etc

http://www.rib.net/forum/f8/new-hatc...tml#post489319