Temperature Differentials
But when you take your boat off your car that’s been riding atop in the blazing sun and put it in the cold water (such phenemon is experienced regularly here in the Great Lakes), the pressure and temperature of the air inside your sealed compartments suddenly changes, resulting in what other posters have attempted to explain. Hence the reason to vent the bulkheads to relieve that pressure before it sucks in your hatches and if extreme, blows out your bulkheads.
This may not be a problem for those who cartop in relatively mild temperatures and paddle in warm waters…
What kind of hatches?
– Last Updated: Oct-04-05 11:10 PM EST –
Glad nothing ever happened to you, but your experience with your particular gear is no reason to be a butthead and dispute the overwhelming support and proven logic of venting.
There are paddlers on this board who have had big trouble from not venting. kfsrmn had a KajakSport blow a bulkhead - going through mountain passes if I recall.
KajakSport and Valley style hatches would be most likely due to the tight seal.
Venting does no harm, and is a widely accepted practice. It does more than prevent the occasional freak catastrophic failure. By keeping the internal pressure equalized with the outside it puts less stress on the hatch covers and bulkheads, and eliminates suction leaks.
As Braumeister noted, it's the temperature difference between the hull in the sun vs. much colder water that is the most common issue. Launching hot boat into cold water, a capsize in cold water on a hot sunny day...
I have yet to see a single valid reason not to vent, or any complication or issue caused by venting.
Agreed, Greyak.
I never saw the need in my old boats either, but they used neoprene hatch covers with plastic protectors. That style of hatch cover will naturally vent enough to avoid problems. I first noticed issues on my first Valley boat when I would move from one temperature to another. The hatch covers would either puff out or suck in, which means there is undue stress on bulkheads. My current boat with Kajak Sport hatches did the same thing at first. This is one of those situations when no harm will come from venting the bulkheads, but much could come from not doing so. I, for one, will not take the risk.
It Wasn’t The Mountain
It wasn’t the mountain that caused the problem of the blown hatch. It was the wind. I had a hatch come off on flat terrain. That’s when I learned to stick it inside. Some hatches have been known to come off while launching into surf. How would venting help there?
Several years back I was involved with a goat packing group. I had informed them that I had learned of a better way to saddle my animals. Many refused to listen because it went against conventional wisdom. I held my ground for many months. Eventually some tried my method and found I was correct. The saddles rode better and their pack animals performed better. Considering my experiences with my beloved goats calling me a butthead doesn’t offend me one bit.
Why cast aspersions on the goats?
A desire to drag a discussion over venting hatches thru ridiculous dross is hardly a good reason to malign perfectly nice goats.
Leaving hatch cover off is one way…
– Last Updated: Oct-05-05 5:40 PM EST –
... but hardly counts as wisdom. No good reason not to vent. Get over yourself goat packer (and please keep your experiences with your beloved goats to yourself. Too much info)!
Wow!
Who and the heck would have thought that an educational post about venting bulkheads woudl turn to talk about…goats! Now I think I’ve seen it all and I can head off to bed.
Vent those bulkheads
All my boats have vented bulkheads and I always have lots of water in the cockpit because I’m a rollaholic.Never had a leak or any other problem except the Pintail which wasn’t vented at the front when I got it. The front hatch cover would bulge all the time until I vented the front bulkhead.I also can’t understand how properly installed hatches of any style could come loose while driving unless you drive at mach 1.
When I built my Pax 18,an S&G boat, I was in correspondence with another guy from CLC (Jack) who had paddled one of the prototypes. The Pax boats have a Valley hatch at the rear but no hatch up front,just a sealed compartment.
They forgot to drill the front bulkhead and on the maiden voyage, a hot sunny spring day with very cold water and guess what? A loud bang like a gun going off(scared the hell out of him) and the deck in front of the paddler had a 3 inch crack in it. So just vent it and go paddle.
Bert
Educational?
How is drilling an unneeded hole in your kayak educational? There’s no science backing up this venting belief. It’s 100% supposition. Buying and installing extra straps makes far more sense. No vent is going to keep a hatch more secure than straps.
Let’s talk science. The one example given so far is a hatch coming off in a mountain pass. Since hatches aren’t airtight does the pressure inside the hull increase so quickly that the hatch is blown off before the air can slowly leak out? Just how fast would a person have to drive to make that happen? Mountain passes contrict the winds causing them to accelerate. Mountain top create wind eddies that drive the wind downward. Which would seem to be more likely, a gust of wind working it’s way under the edge of a hatch or a sudden unexplained increase in pressure within the hull? Also we have to ask how do we know that the hatch was sealed correctly? Was it totally over the lip or not? All you people out there tell us how you know, for a fact, that your hatches can pop off from pressure build up. If you say temperature variances tell us how fast the temperature has to rise to cause that to happen. Don’t just throw out a phrase and think you made a point. We’re talking science here not group think.
Here’s another question. Does venting a kayak make it easier for water to leak in because air doesn’t have to be displaced? Remember, as water flows into the hold of a kayak air has to flow out.
I told the goat story to demonstrate how very subborn I am and that this group isn’t the first to agonize over that.
I kinda enjoyed it
Since it seemed that everything which can be said about venting had long since been said, I got a giggle out of the image of goats with goat-sized saddles. Especially if the goats were the size of the all white kind (breed begins with an S but I forget the rest), or the black chinchillas rather than the bigger ones. Compared to my horse saddle those must be very cute little things.
Doesn’t have a darned thing to do with the value of advice about (not) venting bulkheads, but at this point in this thread that’s long since been lost anyway.
You can’t be serious
– Last Updated: Oct-06-05 11:49 AM EST –
Venting has nothing to do with securing the hatches so they don't come off. It prevents damage (to bulkheads/hull/deck/hatches) from pressure changes. Yes, some hatches do seal airtight.
Obviously hatches should be strapped and/or tethered (depending on type). The leak question was already covered. Equalizing the pressure is more likely to prevent leaks.
Try reading more and ranting less. Methinks you need some of those straps on a jacket with extra long sleeves...
Here’s some science
A vent equalizes pressure. As others have noted, hatches bulge when pressure in the bulkhead goes up. I’ve, however, never had a hatch pop off, or have bulkheads fail due to this. The opposite situation is a vacuum, where the pressure in the bulkhead is less. This means that there’s a constant pulling of moisture into this low pressure area. Any hairline cracks, voids etc., are now much more likely to leak. In many cases people find their bulkead areas drier after venting, as the vacuum effect is negated. I’ve solved a lot of mystery leaks in boats by drilling a tiny hole! In support of your later comment, for water to enter your bulkhead through this tiny hole, would mean it has to compress the air within, which equates to very little, if any water getting in, even in rescue practices. In the end why argue over this stuff? Stubborn can be good, and limiting as well. In this case you may be similar to the people who resisted your ideas about loading animals??? Take care ya’ll
I thought…
That the goat story had to do with venting your goats and not how stubborn you are.
I remember way back in my own goat packing days when all we had were those non-vented goats. That was messy times.
Once we got up to about 4,000 feet, those goats just blew out and sprayed goat shit all over our packs. We learned real quick to wrap tarps around our goat-packing equipment, that is of course until they came out with those self-venting goats.
Those were a bit more smelly, but not quite as messy. Yessir, not as messy by a long shot.
Is 1/32 the proper size?
Yup
That’s what I’ve used in all of my boats. It’s large enough to do the job, but small enough not to allow any leakage.
Is 1/32
large enough to vent a goat? I think a 1/32 might make them whistle while venting. That could be more annoying than pash.
Bob
one way valve…
goats fart. this, while smelly, equalizes the pressure.
now, long ago, the fossil records show us that prehistoric goats had no a-holes, sure…then they would have had to burp only to solve the pressures of being a goat and sometimes, at higher elevations and in summer, it wasn’t enough…this is why the unicorn died out. no a-hole.
the fossil record goes on to show that through selective breeding with a-holes, goat design has come a long way and with these improvements the population as a hole is safer.
these days we still tether/hobble them to keep them in place though.
Ditto yup,
1/32" is just right. Never had a venting/water problem with that size.
Small bit sources
Check in surplus houses and used tool stores. They often have resharpened industrial drill bits from circuit board shops for peanuts. I bought a box of 50, 1/32" drill bits for $5.00. The break pretty easily, so it’s good to have a few on hand.
Venting foam and plywood bulkheads
Venting foam bulkheads can be as easy as poking a hole through them with a piece of wire (a bicycle spoke works well). Typically, after poking the hole I’ll take a piece of the tubing that comes with spray lube cans and stick it through the hole. A sharp chisel cuts it off flush with the surface.
With plywood bulkheads, you need to seal the edges of the hole so the wood cannot absorb water. The recommended method is to drill an oversize hole (1/8" or so), fill it with epoxy, then drill the vent hole in the center of the epoxy plug.