Pressure relief in bulkhead compartment

Not an original idea, but I think it worth repeating. We all know that drilling a small hole in the bulkhead will relieve thermal expansion and contraction. Easy enough, in a composite kayak. But the foam bulkheads in plastic kayaks, such as the Necky Chatham 17, need a bit more. Using an appropriate size drill bit as a mandrill, insert a plastic soda straw through the bulkheads. This keeps the air flow open, and equalizes the pressure differential between compartments. No more sagging or bulging hatch covers. I don’t know where I heard it first, but I thought it a great idea. Ken…

My kayak retailer was very specific:

– Last Updated: Aug-18-08 8:49 PM EST –

Use a very small drill and drill into the hatch cover. This relieves pressure, is unlikely to allow water into the hole as there is positive pressure inside (effectively pushing water out), is reversible (by buying a new hatch cover), and does not compromise the mandatory and life saving flotation of the dry hatch compartments.

Hope someday to own a boat with hatches
so airtight that bulkheads NEED pressure relief.

you say straw …I believe You actually meant to say the straw that comes with a WD 40 spray can or a can of Carb Cleaner…Seems Your hands wrongly typed SODA STRAW…

Best Wishes


Drill the hatch cover?! Never!
I spend far too much time rolling to ever consider that. VCP hatch covers really do seal that well. I would not buy a boat without them, except possibly something like the C/D Caribou,. One of the finest boats I have ever owned. Besides, a dab of silicone will instantly seal the miniscule hole I am describing. Not to be argumentative. Ken… End of discussion…

Something else that works well
are the thin, long plastic straws that fit into the nozzle of many spray can lubricants. Just push it through the bulkhead and trim off the excess.

Your retailer believes that a hole to the outside elements that comes in constant contact with water,is better than one that releases to the enclosed portion of Your boat?

Everthing is easially reversiable, in fact a small dab of Your choice of either resin or goop or aquaseal would fix any bulkhead hole without buying a new (35 to 60 dollar) hatch.

HMMMM…(just a thought to think about)

Best Wishes


come on folks…
you jam a phillips head screwdriver thru the middle of the foam b/h. straw? and you don’t think a hole will let air thru w/o a straw?



Your retailer is an idiot
The pressure in the compartments varies with temperature. When the air inside heats up, you get positive pressure, but when it cools down - as when you toss a hot boat into cool/cold water - you get negative pressure and it sucks air and water (if present) into the compartment. Vent the bulkheads, not the hatch covers.

If you drill the hatch covers
You can install a drain plug on the bottom of the hull at the same time. My kayak retailer was very specific about centering the drain plug below the seat to maintain the kayak’s feng shui.

much ado about nothing

I don’t vent my bulkheads or hatch covers…Just like a baby…Burp them every now and then…

The hatches don’t seem to mind…they bulge a little in the sun and when You burp them they let out a small sigh of pleasure…

In the cold water…they suck down some…not a big issue…

as long as the boat was correctly made all stays intact and waterproof…good barometer on soundness of the water proof structure. and the dry bags stay dry on the outside as well as the inside.

Best Wishes


Just use a tape measure
and keep track how high the cover flies when it blows.

You’ve got to be kiddin’ about this thread, aren’t you?

Paddlin’ on



My QCC …
… has a very small hole drilled in each composite bulkhead. The hole is located within a couple of inches of the top of the bulkhead. During wet exit/self-recovery practices that means the hole is now at the “bottom” and typically underwater. The hole is so small water barely seeps in … and I mean seep. After a half-day of practices and being upside down over a dozen times - sometimes for a prolonged period of time during instruction - the boat took on maybe 1/4 cup to 1/2 cup of water MAX. I would never consider drilling a hole through the hatch - I imagine you’d get water in the compartments either way so why “destroy” a perfectly good hatch? And, as a previous poster mentioned, if you simpy don’t like the hole you can put a glob of silicon sealer/caulk over it. Easy enough to do over a hole drilled in the bulkhead.

Also agree
My Foster Legend generates a lot of suction or pressure because the hatches and bulkheads are extremely water tight.

I called Seaward about whether a hole should be drilled and they said not to. They said that the hatches and bulkheads will withstand far greater pressure differentials than be created by temperature and elevation changes, and that the pressure would do no harm to the boat, which is why they don’t put a hole in at the factory.

A piece of 1/8" rigid polyethylene
tubing can be inserted through an appropriately-sized hole in your hatch cover. Allow the tubing to extend the whole way to the bilge of your boat. The outer end should extend at least 2" above the hatch cover.

When surfing a sufficiently large wave, your speed will increase and Bernoullii’s Principle will suck any water from the bilge through the straw and out into the air stream.

Of course, you will need to have teh bulkhead vented for this to work properly.

The droplets of water exiting the tube will mix with the spray kicked up by surfing, and you will hardly notice it.


two points
you guys are cruel

appropriate venturi outlet
might be needed, maybe something like the raised tail on a C5A transport.

so why do manufacturers of fine kayaks
warn you against leaving the hatch covers on while car topping on hot sunny days?

I have heard of kayak damage with hatches that seal very well and stay put when the internal pressure of that hatch builds.

A little vent saves a lot of potential drama…