Pressurizing interior to find a leak

L124C · #1 (**permalink**) 06-18-2011

I started another thread regarding a leak I am having trouble tracing.
Some SN members recommended pressurizing the boat's interior with a leaf blower or shop vacuum after sealing any routes where air can escape. At this point, I'm convinced it's the only way I'm going to trace this leak. The design of my boat includes a couple of fairly large passages between the galley and cockpit lockers, which are difficult to seal completely. To compensate for this, I decided to run shop vac intake hose from the lockers, through the passages, to two shop vacs in the galley. I filled the passage space around the hoses with rags as much as possible. I also set up a leaf blower attached to a Dorado vent as shown in the picture. I don't know about the "220 MPH" claim Craftsman makes, as everything stayed upright in the Head below. However, I certainly had a lot of air entering the boat!
For bay sailing, I replace the companion way drop boards with a single piece of Starboard, so I used that to seal the companionway. I turned all three blowers on, closed the Companionway hatch, put some tape over the drop board/hatch joint, and expected to see bubbles somewhere when I applied soapy water to the deck. NOTHING! The only area where I think air was escaping was at the companion way hatch which is difficult to seal. To seal it effectively, I think I would have to have someone seal it from inside and stay there while I looked for bubbles. I wouldn't do that to an enemy, much less a friend!
I looked at Don Casey's book "Sailboat Maintenance" and he recommends sealing the entire companionway with plastic or a garbage bag and tape. He also recommends letting the interior pressurize for about 5 minutes before testing. I intend to do both tomorrow. Any other tips regarding pressurizing will be greatly appreciated, because if I don't know where the leak is originating by this time tomorrow, I'll be one unhappy "Yacht" owner!
If you are interested the other thread is :http://www.sailnet.com/forums/gear-m...tem-salon.html

L124C · #2 (**permalink**) 06-19-2011

Well, I've spent a day and a half pressurizing the boat and dousing it with soapy water. All I've got to show for it is one very clean boat! The good news, the boat is tight. I thought surely I would find several leaks. The bad news is I've still got a leak I haven't found.
Lessons learned:
I used 7 mil plastic sheeting to seal the inside of the companion way, allowing the pressure to push and seal against the slats and hatch. My boat's engine is mid ships, so I have several passages that lead into the cockpit lockers. I put in earplugs, turned on the leaf blower, sealed myself inside, and went around with a small piece of the plastic, putting it against any seam or opening I thought might be allowing air to escape aft. If it was, the plastic would cling to the opening or seam. This allowed me to find air passages I didn't think of, like holes in the keel stepped mast for wiring. I then either taped or placed a piece of sheeting over the opening or seam. When I was sure I had all the air escape routes sealed, I slipped out the companion way, replacing the sheeting behind me. Unfortunately, I didn't find the leak, so I added two shop vacs to provide extra pressure. Still didn't find a leak. I was starting to doubt that I had enough pressure, or the right soap solution, so I unscrewed the cap for my anchor chain on the fore deck. As I got to the last turn of the cap, the soap created large bubbles around the perimeter of the cap. Another quarter turn, and the cap came off with a WHOOSH, which confirmed I had plenty of pressure inside the boat. So the pressure system didn't work for me, but I hope my experience might help someone else who finds this thread.

deniseO30 · #3 (**permalink**) 06-19-2011

Well if you went through that much trouble why didn't you get a smoke generator? It's not a candle but not so much a flare either.. but it makes a heavy white smoke that is easy to trace.

L124C · #4 (**permalink**) 06-19-2011

Quote:

Originally Posted by deniseO30

Well if you went through that much trouble why didn't you get a smoke generator? It's not a candle but not so much a flare either.. but it makes a heavy white smoke that is easy to trace.

Because others have suggested the soapy water would be as effective without the mess. I'm not particularly fond of the idea of smoking my boat. I should have seen the leak if it was there. I proved that with the test. Big rainbow colored bubbles are difficult to miss. The leak (water in the Salon) didn't manifest during my testing. It may take an even longer dousing to wick from wherever it originates. At this point, I'm wondering if it has something to do with wind acting on the rigging in a certain manner. Anyway, as someone who is starting to feel like Bill Murray in Caddy Shack, I respectfully ask that people refrain from using terms like "easy" "piece of cake" and "shouldn't be difficult to find". I assure you, there is nothing "easy" about THIS leak! If you use the link to my other thread, you'll see someone else apparently felt the same way in the past.

deniseO30 · #5 (**permalink**) 06-19-2011

The smoke is non toxic and they are made for just such testing. You could also try an infrared scanner on a cool day or night with very warm air in the boat. Oh.. and the leaf blower may seem like it's great.. but the volume is pretty small for what your trying to do.

I HAVE BEEN READING!

mitiempo · #6 (**permalink**) 06-19-2011

The other solution is to re-bed the deck hardware. If it hasn't been done for a while it is possible it needs it. As there is a leak there could be wet core somewhere as well.

GaryHLucas · #7 (**permalink**) 06-19-2011

I was wondering how long you allowed the blower to run before testing? I think a leaf blower puts out maybe 350 cfm in free air. You want to build pressure though, and that will push the blower back on it's curve, so it is likely it will produce much less volume, say 100 cfm. So what is the volume of your boat? My 26 footer has 5' headroom and a beam of almost 10' So I'd estimate the volume at 26 x 10 x 5 = 1300 cubic feet/2 to account for taper to both ends, or 750 cubic feet. So it should take about 7 to 10 minutes to pressurize the boat to the maximum that the blower can provide.

I blew up my inflatable dingy using just a shop vac. I found leaks everywhere at that pressure with soap bubbles, so a vac or leaf blower should have enough pressure.

Gary H. Lucas

L124C · #8 (**permalink**) 06-20-2011

Quote:

Originally Posted by mitiempo

The other solution is to re-bed the deck hardware. If it hasn't been done for a while it is possible it needs it. As there is a leak there could be wet core somewhere as well.

I've re-bedded most of the hardware and the toe rails. However, shouldn't the pressure testing detect any bedding failure? If air under pressure can't get out, how can water get in? Am I missing something?

mitiempo · #9 (**permalink**) 06-20-2011

Chainplates possibly.

L124C · #10 (**permalink**) 06-20-2011

[QUOTE=deniseO30;741961]The smoke is non toxic and they are made for just such testing. You could also try an infrared scanner on a cool day or night with very warm air in the boat. Oh.. and the leaf blower may seem like it's great.. but the volume is pretty small for what your trying to do. /QUOTE]
Where do you get the smoke generators? As I indicated, I used the leaf blower, and two shop vacs. The pressure I felt when I unscrewed the cap was substantial. What device would you recommend to generate enough pressure, and how do I know when it's adequate? Casey recommends sealing the Companion way with plastic sheeting and tape. I had enough pressure that I doubt the sheeting would have stayed in place had I not enclosed it with the Companionway hatch and slats. Maybe I could use a barometer to measure the increase in air pressure. How much is enough? I guess when I see the deadlights budging, I've gone too far? :eek