through hulls again

Jenni · Nov 24, 2008

From what I have seen from the wooden plugs you just wedge them firmly in the through hull opening closing it off on a semi permante basis. I have seen this done on a through hull or two on wooden boats. On a fiberglass bout if you no longer want the through hull fitting I would cut it out and fill the hole with a proper fiberglass patch.

Allan R · Nov 25, 2008

Through-hull Fittings

[FONT=Verdana, Arial, Helvetica]"Every through-hull fitting in your boat is a potential hole that could sink you in a matter of minutes. Although they are out of sight and, at times, difficult to get at, through-hulls need careful routine checking, at minimum every three months. Many through-hulls such as engine-cooling intakes and sink or cockpit drains, tend to be left open continuously and the valves may stick in the open position. You should operate the valve by turning it on and off to make sure that when an attached hose fails you can stop the water flow. [/FONT]
[FONT=Verdana, Arial, Helvetica][/FONT]
[FONT=Verdana, Arial, Helvetica]As an additional precaution you should get wooden bungs (tapered soft wooden plugs) for each through-hull in your boat. (You can get them at most Marine Supply stores.) Make sure that they are the proper diameter to fit in the through-hull. Once you get them back to your boat, don’t just throw them in a drawer. Take each appropriate size to the through-hull it fits, drill a hole in the larger end and thread a string or monofilament line through and tie it to the through-hull fitting. When the inevitable happens you won’t have to go looking for the bung. Just reach down, put the tapered end in the hole, and press down until tight and the leak has stopped. [/FONT]
[FONT=Verdana, Arial, Helvetica][/FONT]
[FONT=Verdana, Arial, Helvetica]A two inch hole just a few feet below the waterline can sink a 30’ boat in just a few minutes."[/FONT]

Steph · Nov 25, 2008

toilet bowl wax too

One thing that I have read on the forum and now stock on the boat are toilet bowl wax rings (easily purchased at Home Depot, etc). I keep two on board just in case. I understand you can squish them into a "ball" then cover the hole, back with something solid like a small piece of plywood, etc. just to get you into port. Here's to keeping dry!

Maine Sail · Nov 25, 2008

Mike8193 said:
I hope I don't seem fixated on through hulls. One question is bugging me. I see adds for wooden plugs to use in case of a through hull failure. How are you supposed to use them? I don't know what you would do with one. If a through hull fails, how does it fail? Does it leak around the fitting through the hull? Is it the valve that fails? Do you remove the entire through hull or just the valve when it has failed? Obviously, I am referring to when the boat is in the water and I suddenly have a rapidly leaking through hull. I plan to this spring take a good look at the through hulls on my boat to understand them better. But what do you do specifically in an emergency?

Mike,

Wooden plugs are for a catastrophic failure of the seacock or a snapped off thru-hull. Considering I have personally snapped one I have a good understanding of why it is important to have them on board.

Here are a few things I'vefigured out over the years.

#1 I keep them in a sealed ziplock bag as close to the seacock as possible, as opposed to fastening them off to it with string. I use Gorilla tape to secure the bag to the hull.

Tapered plugs are meant to swell when pounded into a seacock or a thru-hull. If they have been sitting in your damp bilge with 95% RH they won't swell and seal as well as they will if kept dry. Thye will still swell but they will seal better and stronger if you pound them in from a dry state rather than very moist state.

#2 Don't forget a mallet to pound them in with. Once pounded in they will swell and become quite dificult to remove.

#3 Test fit them prior to storing them in the location of each seacock. Many times I've found the need to cut them shorter (the wide end) so they could actually fit into the seacock or thru-hull.

#4 If you suffer a hose failure simply close the seacock. Tapered plugs do not generally need to be used for hose failures unless the seacock is inoperable. For hose failures double ended hose barb splices and hose clamps are the best medicine to effect a repair. It's a good idea to know the diameter of every underwater hose and then to have the matching OD to ID hose barb splices on board.

#5 If you have an area with more than one seacock, like under a sink, and you will have a bag of say three tapered plugs for each seacock you should write on each with permanent marker. This ensures that in an emergency you grab the right plug. It is always a good idea to label all your seacocks..

While I love wax Johnny Rings they are not something I would personally use in a thru-hull failure situation. Often a failure will occur when it's rough, as happened to me. The hydraulic pressure created by a boat smashing off a wave in rough seas will be considerably higher than the static pressure created by a boat just sitting there in benign conditions.

Tapered plugs are designed to swell once pounded into the orifice and they create a mechanical seal. Wax makes no mechanical seal and will need tape or another sort of way to prevent it from being pushed back into the boat. Tapered plugs are also faster to use..

Keep in mind that a 1" hole two feet bellow the water line lets in 27.8 Gallons Per Minute. That's 1668 gallons per hour! Even a 2500 GPH "Rule type" bilge will barely 400 to 700 gallons per hour when hose restrictions and head pressure are taken into account..

sailingdog · Nov 25, 2008

This is one reason it is a good idea to minimize the number of seacocks you have as much as possible. As Maine Sail said, the plugs really need to be dry fit to make sure they're the right size and shape.... and need to be kept dry. The wide end of the plug should also have a hole drilled through it and a bit of light line through the hole—so that the plug can be tied into place until it has a chance to swell up and seal properly.

Ross · Nov 25, 2008

In the absence of a proper wooden plug almost any rag can be used to jam into a hole. The US Navy teaches damage control to all recruits and they hold damage control drills on all of the ships on a regular basis. There are so many ways to let water into a hull that tapered plugs are just one of many methods that need to be known. It is not necessary to be 100 per cent successful in stopping a leak, reducing the flow from 1600 gallons per hour to 100 gallons per hour makes it manageable.

caguy · Nov 25, 2008

Ross, I learned a few years ago, the hard way, from the CG that a rag coated with bees wax is even more effective. I now keep a ring of toilet sealer and rags handy.
Frank

Don12364 · Nov 25, 2008

Carry Bungs you never know when you will need one

To qualify to race offshore in the UK every boat has to have a bung attached to every through hull with a piece of line.
One day I had an engine inlet strainer come clean off in my hand just as I went to undo the 1/4" wing nut to clean the inlet strainer. I was single handed and at sea. The internal fountain was spectacular. Unbeknown to me the through hull had de-zincified.
In a panic I stuffed my forefinger down the hole. Apart from the rough broken edges of the metal cutting my finger quite badly it reduced the leak to a trickle.
Problem was I was now captive to the damned seacock! Plenty of time to think though.
A bar of soap would have done but I didn't think of it.
Eventually I made a dash for the tool box and found a small blob of Blu Tak. It doesn't take much to fill a 1/2" diameter hole.
Anyway all was well and I nervously made it home - without an engine.
Now I keep a bag of plugs on board with a hammer to drive them home.
Cheap enough for everyone else to do this also.

sailingdog · Nov 25, 2008

Pretty amazing how fast water comes in through a 1/2" hole... isn't it... I wouldn't have trusted BlueTak, as it isn't very strong or sticky, if it is the stuff I'm thinking of.

Donalex said:
To qualify to race offshore in the UK every boat has to have a bung attached to every through hull with a piece of line.
One day I had an engine inlet strainer come clean off in my hand just as I went to undo the 1/4" wing nut to clean the inlet strainer. I was single handed and at sea. The internal fountain was spectacular. Unbeknown to me the through hull had de-zincified.
In a panic I stuffed my forefinger down the hole. Apart from the rough broken edges of the metal cutting my finger quite badly it reduced the leak to a trickle.
Problem was I was now captive to the damned seacock! Plenty of time to think though.
A bar of soap would have done but I didn't think of it.
Eventually I made a dash for the tool box and found a small blob of Blu Tak. It doesn't take much to fill a 1/2" diameter hole.
Anyway all was well and I nervously made it home - without an engine.
Now I keep a bag of plugs on board with a hammer to drive them home.
Cheap enough for everyone else to do this also.

Ross · Nov 25, 2008

If you want to make a practice damage control problem, fill a large trash can with water and knock a hole in it down near the bottom and try to plug it. Try different methods and see how long it takes before you drain 20 gallons of water.

sailingdog · Nov 25, 2008

The only problem with that, is as the can empties, the flow slows down... in a boat the opposite happens, as the boat sinks deeper, the water pressure goes up and the flow increases.

Ross said:
If you want to make a practice damage control problem, fill a large trash can with water and knock a hole in it down near the bottom and try to plug it. Try different methods and see how long it takes before you drain 20 gallons of water.

Ross · Nov 25, 2008

sailingdog said:
The only problem with that, is as the can empties, the flow slows down... in a boat the opposite happens, as the boat sinks deeper, the water pressure goes up and the flow increases.

Actually the flow rate should remain nearly the same for as long as you can reach the hole in the hull. The advantage of the can is that you get to water the lawn and not go for a swim.. You could have a friend with a hose keeping the can full. ;D

Don12364 · Nov 26, 2008

Sailing Dog

Water flow into a hull DECREASES as the hull settles - due to increase in waterplane area to support same displacement.

Blu Tak - Needs must when the devil drives!

sailingdog · Nov 26, 2008

Water flow through hole in the hull has little to do with waterplane area. It has far more to do with depth of the water outside the hole... and as the boat sinks, the depth and pressure on it increase. The formula for the rate of water entering a hole is:

Q = 20 x d x square-root of h
Q = flooding rate in gpm
d = diameter of hole in inches
h = depth of hole underwater in feet

Deeper the boat goes...faster the water comes in.

The waterplane area of a boat increases as it sinks deeper, and this slows the rate of sinking, but doesn't affect the rate of water flow into the hull, except in that by slowing the rate of sinking, the rate of water flow increases less quickly. Don't confuse the rate of the boat sinking with the rate of the water flowing into said boat, which will cause it to sink.

Donalex said:
Sailing Dog

Water flow into a hull DECREASES as the hull settles - due to increase in waterplane area to support same displacement.

Blu Tak - Needs must when the devil drives!

sailingdog · Nov 26, 2008

Ross-

I disagree, as the water level in the barrel drops, the pressure drops as well, reducing the flow rate.

Q = 20 x d x square-root of h
Q = flooding rate in gpm
d = diameter of hole in inches
h = depth of hole underwater in feet

The water flow rate through a hole applies to a hole in the side of a barrel as well as a hole in the bottom of the boat. As the water level drops, "h" drops, and the water flow rate drops as well, since it is proportional to the square root of "h".

Ross said:
Actually the flow rate should remain nearly the same for as long as you can reach the hole in the hull. The advantage of the can is that you get to water the lawn and not go for a swim.. You could have a friend with a hose keeping the can full. ;D

All U Get · Nov 26, 2008

Hi Mike,
I was following the thread and was amused that there is a history of using oakum for plugging leaks. A round bung will fill a round hole, for thise different shapes I have the following: Golf tees--small pin hole, Cedar shingles--thin cracks, lead wool--pounded in with a screwdriver to any shape to fill a crack, and a reverse stopper--like the one in the dingy. I got these ideas from some Haz-Mat training. (I used refridgerator magnets on oil tanks so if you have a steel hull.....)
All U Get
I like the math and agree with sailingdog, deeper=faster. Good reading is "The Terrible Hours" by Peter Maas, the story of USN Officer Charles "Swede" Momsen. He knew his leaks.

Ross · Nov 26, 2008

The depth of the hole below the water has to be figured on the difference between the water level inside versus the water level out side. When you reach equilibrium the flow will stop and if you start to lift the hole the flow will reverse.

Franklin · Nov 26, 2008

Maine Sail said:
Mike,
... That's 1668 gallons per hour! Even a 2500 GPH "Rule type" bilge pump will barely pump 400 to 700 gallons per hour when hose restrictions and head pressure are taken into account..

That's why I have a Rule 2000 as primary and a rule 3800 as secondary. It can pump more water then two open seacocks in my bildge...infact, twice as fast.

My test was as follows but then my primary was a rule 1500.

1) Disconnected battery so pumps wouldn't run.
2)Timed how long it took for two open seacocks to fill my bildge 3/4th the way: 2 minutes and 54 seconds...bildge is 2.5' deep.
3) closed seacocks.
4) connected batteries and timed how long it took for the pumps to turn off. It took 25 seconds for the secondary to turn off (that was 80% of the water). It took another 30 secons for the primary to turn off.

Gotta love those big pumps and you can't have enough when the time comes and they are cheap too. They came in handy when I was riding out Ike and taking on water as I tested the anchor from stern idea (stupid idea!). There was no hole to plug then as it was coming in from all over (laz, air exhaust for generator, companionway cracks and so on.

I personally believe that every boat should have at least a rule 3800. I wanted a rule 8000 but they didn't stock them and I was under a time schedule. Don't think I would have been able to run the hose though anyway as it was hard enough to run the 2" hose for the 3800. The 3" for the 8000 would have been extremely hard to fit if at all. Anyway, for $150, it's cheap insurance. Add an alarm to the secondary switch and you now have somebody on watch in your bildge at all times. Boy it sure does scare the crap out of ya when it goes off

Without a high water alarm, you will not know the boat is taking on water until it's too late. Mostlikely, the hole will be underwater by the time you realize the floorboards are floating and then it's much much harder to find the leak and most just give up and abandon the boat.