Moving Cockpit Drains to Transom?

[Heathenly Twins]

Trying to figure out the logic behind having my cockpit drains led via hoses to seacocks well below the waterline. Seems like a really huge design flaw. Is there a reason I shouldn't relocate them to the transom? The steep following sea argument is moot as I'm hove-to by that point unless inshore and close to calmer options.

Additionally, the relocation would mean space for more batteries 😀

I dunno...thoughts?

[zboss]

Venturi effect. When the boat is moving the water moving across the exit of the drain acts as a force to suck out water from the cockpit.

[Heathenly Twins]

Originally Posted by zboss

Venturi effect. When the boat is moving the water moving across the exit of the drain acts as a force to suck out water from the cockpit.

Ok, but it poses an enormous sinking hazard and renders two whole lockers unusable because of the seacocks. Is the transom option somehow worse? My 1st boat had them and it was great, really simple.

[Muaddib1116]

What type of boat is it? You could build some reinforcing bulwarks around the locker seacocks so that the locker could be more usable.

[Jim Cate]

If your proposed drains are of sufficient size there is no downside IMO. If you are really worried about seas from astern, simple flap valves over the exits will solve the problem completely. We've had transom draining in this boat for many years and many thousands of miles, and still think it is a big improvement over the through the sole and then the skin fitting (and valves if fitted) plan.

A couple of bits of 3 inch PVC pipe glassed in will give enormous flow (hint).

Jim

[sailortype]

not enough info there... but- if the existing cockpit drains are at the forward end, the cockpit sole is 'tilted' forward and will not drain properly if you close them off and install new drains at the aft end. You will always have standing water

[tarian]

I have 2 large seacocks under the boat in the lockers and no water comes into them nor are the lockers not used. In fact the driest part of the boat one wonders did boat designers knew more than us

[wingssail]

Originally Posted by Heathenly Twins

Trying to figure out the logic behind having my cockpit drains led via hoses to seacocks well below the waterline. Seems like a really huge design flaw. Is there a reason I shouldn't relocate them to the transom? The steep following sea argument is moot as I'm hove-to by that point unless inshore and close to calmer options.

Additionally, the relocation would mean space for more batteries 😀

I dunno...thoughts?

I think this is a good change to make with little downside. Transom mounted outlets will work fine provided they are lower than the cockpit floor. They are safer than hull mounted outlets which are always immersed because a failure will not result in flooding.

[sailortype]

"Transom mounted outlets will work fine provided they are lower than the cockpit floor."
and IF the water on the sole flows aft naturally

[Clivevon]

Yes I have thought about this also to get rid of 2 seacocks but my boat is centre cockpit with aft cabin so would be a real fiddle. It remains on my list of things to do, maybe, one day, unless its better weather to go sailing.. But if you have an aft cockpit its a good idea to add the transom drains for sure, simply to increase your seawater dumping ability if you ever get pooped. They dont even have to be right at floor level to be useful. I would put some wire netting in the drain though just to reduce the chances of accidentally losing something through it.
You might keep your existing cockpit drains at first. Just close them off & hose the boat down - you will soon see how well the new transom drains work for removing rainwater.

[Minggat]

Originally Posted by zboss

Venturi effect. When the boat is moving the water moving across the exit of the drain acts as a force to suck out water from the cockpit.

It takes more engineering than that to create the venturi. In my boat, water was actually blocked from draining out by gravity while underway. I dumped a bucket of water in the cockpit once and discovered that where water wasn’t coming in while heeled over just a little, it also wasn’t draining out. The cockpit scuppers were defeated by original design!

Moved mine just above the waterline and did it with shorter runs than the original design. Also eliminated the seacocks altogether. They would become a negative if ever closed.

[SVTatia]

Originally Posted by Heathenly Twins

Trying to figure out the logic behind having my cockpit drains led via hoses to seacocks well below the waterline. Seems like a really huge design flaw. Is there a reason I shouldn't relocate them to the transom? The steep following sea argument is moot as I'm hove-to by that point unless inshore and close to calmer options.

Additionally, the relocation would mean space for more batteries 😀

I dunno...thoughts?

The problem with under the waterline drains is that they are slow, since the water seeks its own level.
How are you planning to lead the hoses to the transom, much above the waterline? Straight out or crossed?
I don't know what type of transom you have and how high above the waterlne is your cockpit, but give some thoughts on heeling - will the drains be underwater? Or when becalmed with large swells, will the water gurgle up to the cockpit when the bow goes up?

[Cadence]

The more water you can get out of your cockpit, fast the better. I can't fathom below the waterline cockpit drains. Through the transom and flaps seems logical.

[Paul Howard]

Some boats with deep cockpits have drains through the floor as the water level is not much lower than the cockpit floor.
If you change to transom drains you may get your feet wet in the cockpit when heavily loaded in the cockpit or when sailing or motoring fast with the stern squatted down and a wave coming up behind the transom.
Depends on the size of boat and conformation.

[chasfgr]

Originally Posted by Heathenly Twins

Trying to figure out the logic behind having my cockpit drains led via hoses to seacocks well below the waterline. Seems like a really huge design flaw. Is there a reason I shouldn't relocate them to the transom? The steep following sea argument is moot as I'm hove-to by that point unless inshore and close to calmer options.

Additionally, the relocation would mean space for more batteries 😀

I dunno...thoughts?

Probably because your cockpt floor level is below your waterline (or very close to it).
Most traditional cruisers had that drain arrangement.
On some transom-drained boats, picking up sufficient speed could result on the drains siphoning water into the cockpit - I've experienced that on a prototype boat, and had to add additional aft buoyancy to stop the problem.

You could, of course fit one-way flaps (as sailing dinghies) but you need an enormous area to successfully drain the cockpit.