How to dry out water inside hollow stringer?

[waterboy222]

Hello All, I am working on some bilge repairs in a 1997 Trojan 400 Express. The hull (made by Carver) utilizes top hat style hollow fiberglass stringers. During the bilge inspection I found a couple of the limber hole seals had failed. Apparently Carver's version of a proper limber hole is to cut a hole in the stringer, insert a piece of 1 1/4" white sanitation hose and let the floor managers 5 year old kid glob silicone around the edge. The hoses they used are about 3" too long on either side of the stringer and have curled up towards the deck over the years. With the hose curled up, it effectively raised the level of water needed to drain by about 1 1/2". When the sealant failed from the hoses curling up it allowed water to run inside the stringers. Now i need to get it out and repair the limber holes correctly using fiberglass tube and glassing them in. No more flexible sealant.

The limber hole is not flush with the bottom of the hull, it is about a 1/2 to 3/4 inches up and that lip is what is holding water inside the stringer. I have shop vac'ed most of the water out and used blue shop towels crammed in the limber holes to wick out what I could get to. But since the boat is sitting in the water, there is no way to get to the very back of the stringer to drill a hole and drain any water inside (without a haul-out, engine and genset removal).

Being that there is no rot to be found, would using iso alcohol or acetone inside the stringer dry out any standing water? Should I holesaw a few places along the top of the stringer to allow air circulation? We aren't talking gallons of water but enough that I want to make sure I am not trapping it insides by sealing around the edges of the limber holes.

Any advice is appreciated! Thank You!

 

[ondarvr]

If the stringers are hollow, then a small amount of water in them isn't going to a be a problem, but it's not like you want it there. Acetone and other similar products aren't going to help, drilling vent holes will. The thing I like about hollow stringers is that all you need to do is drill holes anywhere you want to get it to drain correctly, but if you can't get to the stern right now it rules that out.

​I would enlarge the holes, and lower that lip so water can flow freely into places where you can more easily get at it.

 

[waterboy222]

The reason I mentioned using alcohol is that it dries out water then evaporates, I don't want to trap alcohol or acetone inside if that is how it read when I posted it. I will take a look again and see if there is a way to get behind the gen and put a hole in the stringer. Maybe if I removed the rudder tie bar....

 

[ondarvr]

When recycling acetone and other solvents you use evaporation to separate the exact solvent from the rest of the stuff in the mix, and that includes water, Only a very small amount of water is actually evaporated with the acetone or alcohol. It does spread the water out thinner on a surface though, so when the solvent evaporates it leaves a much thinner layer of water than can evaporate much easier and quicker. Inside an enclosed space you don't get the same result.

 

[waterboy222]

Ahh, Thank you for the clarification!

 

[Kdreese89]

I'd avoid drilling additional holes in the stringer. Especially a hole stringer it gets its strength from being intact and as designed. Ever thought about filling it with something like a low expansion for the. Going back in to drill through the existing lumber holes and some how epoxying the interior of the holes?

I've never done that before but maybe you can find a foam that would utilize the little bit of water in there.

Just a thought, might be crazy though haha

Good luck let me know what you decide.

 

[jbcurt00]

Its already got a 1.25in hole in both sides of the stringer. A little larger shouldnt hurt.

I for sure wouldnt try to fill hollow core stringers, and definitely not w expanding foam.

Waterboy, I didnt see where you expressly stated the plan for putting flotation foam back below decks. Depending on how you plan to do that, fixing/filling/putting the hoses back thru those 1.25in stringer holes needs to be addressed too.

 

[Woodonglass]

Hollow stringer don't need any interior filling. They're designed to support the hull just like they are. Drilling a few 1/4" holes in various DOWN LOW areas of the stringer, will in No Way, sacrifice their structural integrity, and will ensure proper drainage and water flow to the bilge area. As long as the Boat is always stored BOW up...You won't have any further issues.

 

[Kdreese89]

Ok so maybe foam is a bad idea I was suggesting an idea to use as a backer for the epoxy. What about getting an insert in the limber hole and fiberglassing that in to prevent further ingress of water. Of course make sure it's completely dry first. And yes a very few 1/4" holes may not hurt but I would avoid that.

It sounds like the limber holes are properly positioned it's the failed hosing that allowed the water to get in.

Try a fan to dry it out over a few hours and come up with a solution to prevent water from getting in again.

Definitely do not hole saw along the top of a stringer. They should remain fully intact. Woodonglass is right they don't need filler (otherwise the manufacturer would have put it in) just come up with an idea to prevent the water entering the stringer vs ventilating it.

 

[ondarvr]

You can drill rather large holes in structures like this with no adverse affects, it's not a concern unless you plan to remove a great deal of material near the top, you could drill thousands of 1/4" holes and it would mean nothing. There are other ways to use foam that wouldn't require plumbing or tubing, I'd eliminate all of it and let the stringers drain freely into a location where the water can be pumped out

 

[Scott Danforth]

Y you could drill thousands of 1/4" holes and it would mean nothing.

that is as long as the holes as spaced about 1/2" apart or more.

 

[ondarvr]

​Rather large holes can be cut in beams when the correct spacing is used, that's why small limber holes are not an issue. The taller the stringer (beam) the larger the hole can be.

 

[waterboy222]

Some of mentioned an issue with foam, but just to clarify; The stringers are hollow.. I think tonight i will try a handful of 1/4 inch holes along the bottom edge of the stringer. Can anyone confirm if hollow stringers are hollow the entire length or do they have a type of bulkhead in them every few feet?

 

[ondarvr]

Normally they're hollow all the way, but about the time you say that you find one that isn't.

 

[Woodonglass]

As long as you have limber holes in the right locations, it doesn't matter at all if water gets in. As I stated, If you store the boat Bow up (As ALL boats should be...) then the water will drain out.

 

[waterboy222]

The problem with "storing the boat bow up" is the boat sits however it wants to sit. At over 22,000 pounds I don't have much say in it..

 

[Woodonglass]

If she's in WET dock she'll automatically drain to the bilge. If she's in Dry Dock you should always attempt to have the bow Higher than the stern. It's not that hard to ensure.

 

[waterboy222]

Woodonglass, I wish that were the case but the Trojans have 3 separate bilges with no access between each of them. The limber holes only allow water from the outboard stringers to the inboard stringers, there aren't any limber holes from bilge to bilge, if that makes sense. The way the bilges are setup, if the boat is sitting in the water, the water is dead even across the bottom of the boat, it doesn't pile up at the back of each bilge. The forward pump is 3' ahead of the forward bilge bulkhead.

The reason I am trying so hard to get the water out is that I believe the water that is coming from the limber holes is stagnant and may contain sewage due to a failed hose fitting (water in hull froze and lifted tank just enough to break fitting). I just replaced all the fittings and sanitation lines tracking down the source of the smell. After a week away from the boat I came back and there is new water in the forward bilges that has that lovely septic smell that I've been chasing. I vaccuumed it out the best I could and dried everything with a rag. When the tank leaked out it looks like the water from the blackwater tank got into the stringers through the limber holes and is slowly seeping back out into the bilges.

I noticed on a big Sea-Ray they have access plates in the stringers, about 7" or 8". I think this is a great idea for being able to pull any water out of there, rinse them out and repeat til I get the smell out... Any thoughts on adding an access plates?