Marking the area for a thru-hull

[crazycarl]

I've been putting off drilling a hole in the bottom of our 19 for the sink to drain.

I measured, remeasured, and measured again, and again.

Finally I went and bought some magnets.

I placed one inside the boat where I figured the hole would go.


Next, I went under the boat and moved the other magnet around until it pulled to the inside one.


I let the outside magnet hang there and returned inside the cabin.  The 1st magnet was right where i needed it to be.

Now that I know for sure my measurements are correct, there is no need to hesitate any longer.  Although...I'm not sure the Life Caulk will set up properly in this cold weather.  Better wait 'til next summer!

[HideAway]

Don't do it -- the pressure from the water trying to get in the boat will overcome the pressure of the water going out.  Even if it doesn't the drain water has no where to go.   Make the hole above the water line or run a hose to the bilge and pump it out  Matt

[Bob23]

Listen to Hideaway. On the 23,the sink drains to a through hull just above the boot stripe.
Bob23

[Subsailor637]

As the kids say "OMG" DO Not Do that!!!! You must install the thru hull above the waterline

[capt_nemo]

PLEASE, PLEASE, heed the aforementioned advice!

OR

Just run a drain hose to a container under the sink, keep an eye on it, and empty when almost full! Simple and easy.

My cruising solution for running water is this with large plastic drain pan. Works great.



capt_nemo

[Eagleye]

Carl,
The Eclipse's drain is also above the waterline as you can see in the pic. 
I will remember the magnet trick though.  That is a great idea.

-Allen

[brackish]

It needs to be above the water line for reasons mentioned above.  Also, make sure that while it is above the waterline it is below the level of the tailpiece from the sink, or it will not drain.  I put a valve on mine so I can close it when not in use, but the highest point on the valve inlet is just slightly below the sink drain, so water drains slowly and the line stays full to just below the sink basket.  Going to do a little modification to the valve configuration this winter to get it lower.

[skip1930]

Brackish comment--> " the highest point on the valve inlet is just slightly below the sink drain, so water drains slowly "

Reminds me that IN GENERAL, either flowed by gravity or forced by a pump ... when figuring flow and speed of water through a hose, pipe or sewer, liquids run at 33 fpm.

So if you know the volume and the time needed to evacuate and you have a fixed speed, then the diameter in square foot of the hose, pipe, or sewer can be calculated. That was just for poops and grins. The hose diameter is what it is.

Anyway the discharge is always above the waterline + a bit more for the 'wife and kids'.
I like the valve up stream of the hole. Just in case of a brakeage.

Coming up on her last days the USS Coral Sea [CV-43] lost her integrity to the ingress of the ocean while tied to the wharf. Several sea chests [sea chests are down stream of the last valve] let go due to rust, and she sank by the bow into the mud. Three days later she was refloated and the 'O`man never left the compartments flooded while being pumped dry.

skip.

[crazycarl]

I have been looking at placing it just above the waterline.  However,  I've owned 2 boats where the sink drained straight down to a thru-hull BELOW the waterline and they both worked without problems.  (22' Bristol Caravel and 19' Starwind)

"the pressure from the water trying to get in the boat will overcome the pressure of the water going out."
 
Not so, as long as the bottom of the sink is above the waterline, the sink will drain.  Water seeks it's own level, and the water left in the thru-hull and ball valve will only be as high as the waterline. 

In theory, one could vertically install a pipe through the hull and leave it, say...6" above the waterline.  Sail all day and no water will enter the boat.  Yes, the up and down motion of the boat would cause water in the pipe to rise and fall, but as long as the pipe is above the water outside, the boat will stay afloat.

As for using a jug and bucket, I'm doing this to make things easier for the admiral.

Draining into the bilge is not an option as the sink will be used to wash dishes and the like.  The bilge will be used for stowage of can goods on long trips.

Look at sailboats with dagger board keels.  The slot is open, and above the waterline, but not as high as the gunnels. 

[MacGyver]

Carl has the right idea.
When he was down we talked extensively about it, and I have seen a ton of boats, with sinks emptying out below and above the water line.

It is all about where it comes out, and his plan is to use the thru hull when he needs it and shut it off otherwise.

Some folks prefer to leave it open all the time, and some manufacturers count on the idea that people wont remember to turn em off so go above the water line as that is the best chance for non failure.

as a side note, and pretty sure I told carl about this, a surging of the boat could potentially start a siphon, but that only comes from one experience and we are not sure if the sinking of that boat was actually from that, it is just the best idea we had at the time.

Mac

[skip1930]

Our Star Boat had a metal pop-up scupper flat on the hull plank below the waterline that drained the rain water and splash out of the hull, but in order to work properly she had to be moving and keep moving. If the boat was stopped and the scupper was open, she'd fill and sink. Again.
Kind of works like those NASA scoops you see on aeroplanes and race cars.

skip.

[Bob23]

   This is quite interesting and informative. I guess I'm  "thru hull below the waterline" paranoid. I removed the sink from my 23 because it was too small and plugged the through hull. I also plan to remove the other 2 through hull fittings  (depth and another one from a previous owner). If it fails and no one's there to see it, down to the bottom she goes.
   I use the same fresh water supply that Capt. Nemo uses. Simple, portable and trouble free. I also get to place the additional weight a bit forward while sailing thus helping to balance the 23.
Bob23

[Jon898]

Just a couple of observations on the photo by brackish...probably OK if above the waterline, but be careful of that kind of installation below the waterline.  If below the waterline, it should have a proper seacock (technically a ball or better yet a greasable plug valve with a flange one end and a hose barb the other with the flange bolted to the hull) and not the little stub of hose between the through-hull and the valve.  Good practice is also to double the hose clamps (two per hose barb) and make really sure all the components of the clamps are non-magnetic (300-series) stainless (lots of clamps are out there with low quality screw components attached to a nice SS clamp band...corrode off in short order).

Another thing to watch is the quality of the through-hull fitting itself regardless of whether it's above or below the waterline.  BoatUS's Seaworthy frequently reports on plastic through-hulls that have degraded under UV (sunlight) exposure and have split/cracked and caused a sinking.  If it's close to the waterline it can easily become otherwise if the loading or use of the boat changes (e.g. above the line in salt water can become below the line in fresh water).  Marelon is a bit more expensive than the plastic ones, but probably worth it if you do not want to spring for bronze (and fight dezincification to boot).

[Eagleye]

As this is only my second season sailing the learning curve has been rather steep.  One lesson that became apparent this season was that the screw down sink stopper on the Eclipse not only keeps the water in the sink but also keeps the sea out of the boat.  On one occasion when the winds were "frisky" and the Madame was healing around the 45-degree mark, I noticed, after the fact that water was coming in through the sink drain.  The roll of paper towels that was bouncing around the cabin ended up in the sink and turned into a soggy glob.  Lesson learned.   





I do like the setup that Brackish pictured and I will put that on my to-do list. 
This has been an interesting thread!

Thanks,
-Allen

[brackish]

I have been looking at placing it just above the waterline.  However,  I've owned 2 boats where the sink drained straight down to a thru-hull BELOW the waterline and they both worked without problems.  (22' Bristol Caravel and 19' Starwind)

"the pressure from the water trying to get in the boat will overcome the pressure of the water going out."
 
Not so, as long as the bottom of the sink is above the waterline, the sink will drain.  Water seeks it's own level, and the water left in the thru-hull and ball valve will only be as high as the waterline. 

In theory, one could vertically install a pipe through the hull and leave it, say...6" above the waterline.  Sail all day and no water will enter the boat.  Yes, the up and down motion of the boat would cause water in the pipe to rise and fall, but as long as the pipe is above the water outside, the boat will stay afloat.

As for using a jug and bucket, I'm doing this to make things easier for the admiral.

Draining into the bilge is not an option as the sink will be used to wash dishes and the like.  The bilge will be used for stowage of can goods on long trips.

Look at sailboats with dagger board keels.  The slot is open, and above the waterline, but not as high as the gunnels. 

correct on all counts, however if you have a choice that is functional it should be above the waterline.  If you get a break in the line where both the break and the thru hull are below the waterline, boat sinks.  If you get a break in the line with the thru hull above the waterline, boat floats regardless of the position of the line.  That simple.  Can't happen you say?  when I bought my boat it had a split in the sink drain line that caused me to need to replace it.  If that split had been below the water line with the thru hull where you are planning to put it, my unattended boat would have sunk.  All of my boats of the past that had below waterline drains, primarily for heads, had heavy, expensive, and maintenance requiring bronze seacocks right at the thru hull.  Just saying.....