pressure relief hole in bulkhead?

Forget the duct tape
It’s not going to make any difference in the drilling of the hole and it will just gum up the drill bit. Leaving it on will likely block the hole you just drilled.

It’s common practice to put MASKING tape on fiberglass panels before cutting or drilling them, but again, with a small hole, it’s completely unnecessary.

You’re really WAY over-thinking this. Just drill a hole and be done with it.

The paradox is…

– Last Updated: Aug-06-11 7:19 AM EST –

...that drilling holes in your bulkheads actually makes your boat drier. The reason is pretty simple. A boat on a car top, exposed to the sun gets pretty warm, the air inside expands and at least some of it leaks out. When you put it on cool water, the air inside contracts, creating low pressure. As air seeps into the low pressure compartments, it often brings water along with it, since water tends to collect around hatch covers, deck fittings and other likely air seepage points.

As for the bulkhead holes themselves, unless your cockpit is full of water, you're not going to get any water into your compartments because there isn't any water near the holes. Even in a capsize/rescue situation, you're cockpit would have to be over halfway full for any water to reach the holes and that's not particularly likely. Even if it did happen, a few drops of water is hardly the end of the world.

The bottom line is that the risk of damage to an unvented boat is a LOT higher than the risk of any water-related issues inside the compartments.

dry hatches
Drilling holes is not something that kayakers made up. P & H starting doing it years ago. I’ve seen boats with oval VCP hatches all puffed up. It’s just bad design to have that happen. You will not get a drop of water in the compartments with a pin hole in the center of the bulkhead. If you start getting a suction and the seal is not perfect, then you can suck in water. I’ve done rescue practice, wet exits etc. with relief holes and my compartments were always bone dry.

No more overthinking . . .
only drilling. Thanks, everybody.


I understand that point…
When the hatch covers aren’t on the kayak the warm air expands and leaks out through the hatches. When you put it in cool water, there is a bit of suction… I just “burp” the hatches. Doing that general takes care of air expansion and contraction to the point of sucking water into the hatches.

My cockpit is full of water quite a bit… When the surf is small I pop my skirt and flood my cockpit for an added challenge. I also re-enter and roll and just goof around with a cockpit half full of water quite a bit. Water in the hatches isn’t the end of the world, but it is a pet peeve.

I agree about damage. I made the rookie move of leaving my hatch covers on while driving over the blue ridge mountains. When I stopped at an overlook not only were my hatch covers bulging up the deck was too. So I burped… when I got gas in the peidmont region the hatches and deck were sucked in quite sharply.

Ever since then I take the hatches off unless the kayak is going in the water.

I have owned a couple of boats with pinholes for air vents and I have not been happy with the results.

I know several companies do this…
I personally don’t like it. The kayaks I have had with relief holes have always had water leak in to the hatches - until I covered the relief holes :slight_smile: When you say “you will not get a drop of water in the compartments with a pin hole in the center of the bulkhead” you need to send that memo to my former kayaks with relief holes.

Like I mentioned above, I have seen not only oval VCP hatches puffed up, but round NDK hatches on NDKs puffed up and the deck as well. Taking the hatches off solved the problem and didn’t involve power tools.

Heck, I once saw a WS Zephyr (plastic) with puffed hatches…

The point is… its not necessary to drill holes to keep the hatches from puffing up.

no water
Valley also has small holes. They have tape over them from the factory and I had the same problem with the hatches bulging out in heat. Good to know they are air tight. Valley test them also.

I haven’t noticed any water in my hatches with the small holes. I do rescues all the time and they stay dry.

I also suspect that the hot air inside the hatches is not good for them. I’ve noticed that the VCP hatches start cracking on the inside. I have posted pictures of this before and a lot of other people mention this same issue.

Did you do it? Details for using Dremel
I’ve drilled relief holes in three kayaks: a Merganser 16 S&G, an Explorer LV, and a Pilgrim Expedition.

I had to use a Dremel-type (electric rotary) drill because the cordless drill/driver was too bulky to place the bit where needed. The little electric drill is also a fraction of the weight! Makes precise drilling easier.

For the wood kayak and the LV, I used blue carpenter’s tape as backing tape. I think it might have been good for the wood-and-glass bulkheads but it was not necessary for the BHs in the NDK kayaks. Just aim for a spot in the center of the BH, make sure the bit is set perpendicular to the surface just barely touching it, and THEN turn on the drill to its lowest setting (if using a Dremel). The hole will be done, cleanly, in a instant. Do not press hard against the BH, because the high rpms on soft material make that unnecessary.

I don’t remember what size bit I used, but it may have been as small as 1/32". Certainly no bigger than 1/16".

Although I drilled both the front and rear BHs in the wood kayak (which has fully vertical BHs), I did NOT drill the slanted middle BH in either of the NDK kayaks. Actually, NDK had drilled the LV’s front BH but not the other two (go figure!). So, until I drilled the rear BH, the front hatch cover would not puff up but the two rear ones did–a LOT. After drilling the rear BH in that boat, the two rear hatches would still puff up some if I did not remove one of the hatch covers. After a shocking experience of the rear deck sucking inward from driving from 10000 ft altitude to 6000 ft, I started removing the day hatch cover for such drives. Fortunately, and to my great amazement, the boat shows absolutely no spidercracking or any other sign of damage from that incident. However, I take pains to remove one hatch cover when traveling across huge altitude changes, just in case.

Interestingly, in the Pilgrim Expedition, I have not needed to do that even though the compartments are watertight after lots of rolling. I believe there may be just barely enough air passing through the skeg cable housing to the cockpit to prevent more than a slight puffing up of the two rear compartments. In the LV, I had sealed around the perimeters of all three BHs, plus I had sealed around the skeg cable housing where it passed through the BHs.

We just returned from a road trip to the PNW and I kept all three hatch covers on the PEX. At each stop I would inspect them, and they never needed burping. At most, the two rear ones would show slight puffing up (or sucking in)…nothing to worry about, as this happens all the time when going in and out of cold water to warm sun and vice versa.

I don’t like hauling the kayaks with the covers off, since that (a) hurts mpg, and (b) allows rain to get in. Light rain doesn’t matter, but hard downpours do put a lot of water in.

BTW, SnapDragon makes a neoprene cockpit cover sized just for the Pilgrims, and you don’t need to send them a tracing. It’s a good, tight fit (unlike the nylon ones I’ve used in the past), so put it on BEFORE you load to the rooftop. It’s hard to put on otherwise.

Why would you not drill the others?
Clearly, you understand the benefit of the vent holes - since you vented some of them - so why not vent all of them? It doesn’t makes sense not to.

All but the slanted bulkheads
In the Pilgrim Expedition, I don’t need to drill that one, for whatever reason, as explained above.

In the LV, I would rather just take off the day hatch cover when planning to drive over mountain passes. If it’s going to rain, I can always stuff some bubble wrap in that small compartment.

The amount of puffing with lesser changes in altitude is not enough to worry about.

What does the slant have to do with it?
Again, there’s not much point in venting the bulkhead between the day hatch and rear compartment if you’re not going to vent the one into the cockpit. If you’re willing to vent the forward bulkhead, which also borders the cockpit, why not the slanted bulkhead? I just don’t see the rationale here.

I drilled!
Today I drilled the bulkheads with my smallest bit, 1/16th. The hard part was the front bulkhead – reachable with my short arms only through the front hatch – but that’s a small round hatch and I couldn’t look in it and drill at the same time. So I drilled by feel. Turns out the hole is not centered laterally but is just right vertically, 2/3 the way up from the bottom.

I noticed that the skeg cable housing passes through the slanted bulkhead at the back of the cockpit, so I thought I’d hold off drilling that bulkhead while I test for a natural leak around the housing. If it leaks air, I don’t need a drill a pinhole. The way I’m testing is I put on all the hatch covers and set the kayak in the sun. If the day hatch and back hatch covers puff up, then I’ll drill the last hole through the slanted bulkhead.

Thanks to all for good advice!

G in NC