"Hidden" bilge

[TR6]

OK I know this has had a lot of attention but I've tried searching for photos without success. I've finally had enough of the flush / bleach / routine every month or so and want a final fix to the smell.

I am planning major surgery to the bilge, drilling holes, enlarging holes, getting to the root of the problem and filling the hidden bilge with resin / glass filler using a large syringe.

The gap between the liner and hull is clean as are the limber holes that I have been able to see, well, as far as I can see with my handy inspection camera anyway.

I understand that the issue is hollows between the liner and hull, I have sounded the sides of the bilge and marked all the hollow areas ready to drill BUT I understand there may be a void under the floor of the bilge as well, this is my area of concern.

Someone on here has tackled this with a 4" hole saw !!!!! I'm a bit nervous about doing this right off the bat so am looking for pics and advice from anyone who has done this.

Hope someone can help

 

[Steve Dion]

Could you possibly make the situation worst?

If there is no air that can get into those area and you have condensation I think you will have a worse mess. The major areas are under the v-berth, aft of the engine pan and the drain from the ice box into the void area. I doubt that you can get to all of the areas without removing the interior.

You may want to look at some of the projects on the H31 and H34 of that era. It will give you an idea of what you are dealing with. Don't forget that the interior pan is a structural part of the hull.

 

[TR6]

A misunderstanding- I'm not planning to "seal" the whole of the area, just get to, drain, treat and fill the "hidden bilge" immiediately around and below the bilge depression itself. I figure that if I can fill the voids that Hunter didn't when they built the boat then there's nowhere for the water to get trapped.

Your comments about excluding the air are fully valid, that would be a bad move,

I understand these voids are there because Hunter didn't put enought filler in when the hull and liner were mated together

This is the area I am on about filling, called the "true bilge" right below the "false bilge"on the diagram (thanks for the tip, I found a couple of useful posts !

 

[Allan12210]

TR6,

I'm the 4" hole saw guy. Here are some pictures of what I did to my "false bilge". I would strongly recommend you do not fill any area with resin. You do not want to impede in any way the progress of the water to the very bottom of the hull. Instead, you want to gain access to that area as that is exactly where the water is going anyway, right now. By attempting to block it will never be entirely successful and instead will trap water where it can't be removed and it will turn septic and stink.

The hull liner was bonded to the hull with passageways to allow water to migrate between the layers. Unfortunately there is a bottom to the hull liner forming a sump that is suspended about 1" above the actual inside surface of the hull. Water collects under there and actually is as much as 12" above the bottom to the lowest drain holes inside the perimeter of the sump area. On the underside of the hull liner is a piece of 1/2" plywood that is now rotten because it is always saturated. Cutting out the bottom of the sump allows removal of the rotten piece of wood and access to mounting a bilge pump directly on the bottom of the boat. Don't worry, the hull is 1 3/8" thick down there so you won't be drilling through. Besides, the keel is under that as well.

As you can see from my photos, I used a large hole saw and made a series of cuts. The first penetration allowed trapped water to well up until it sought its own level. It was black and really smelled. Once that was bailed out with a sponge, the rest was cut out. I used a multitool to lop off a couple of the points to make room for a 2000 gph pump. As I said, the back side had a plywood board that was rotten. After getting all of that out, it is really easy to rinse the interstitial space between the hull and the liner because it all comes down to the bottom where the bilge pump now sits. With a dripless shaft seal the bilge stays completely dry for months at a time and the contribution to odors is eliminated. The task did not take that long.....4 x 4" holes and 2 x 2" holes. Probably could do the whole job now with a multitool and a few blades as the fiberglass does dull them. Clean up and remount the bilge pump. Done.

Allan

 

[Mike Culik]

Allen12210 thank you for the pictures….

I have a H31 of the same era. My understanding they are of similar construction.
I have drilled small holes in the sides of the existing sump bilge pan to drain the under liner area. Even though it has made a difference, it only gets so much water out and I know that there is still stinky water trapped below.

I have seen previous notes about “opening” this area up to get to the actual hull. Now with your pictures I’m sold! You say I should expect a gap of about 1” I’m sure it full of stinky water.

So perhaps if I fill just under the “true bilge” I’d still have water trapped around the slug of resin. Thinking about what the hull form looks like, that makes sense. Opened up you absolutely know there is no water trapped.

Thanks, Mike

 

[Benny17441]

Aeriating the stinky trapped water will only make the situation worse. Just dump a chlorine solutions by the packing gland and down the cooler drain and let it flow back to the main bilge. Now have patience as it may take some days and a couple of outings to get the boat in motion to get the solution and water to mix up and circulate. I don't mind the boat smell as it is like the fresh air of the mountains, is some level it lets my senses know I'm in the boat and makes me feel good. The other good thing is that we quickly adapt and by the 2nd day aboard I'll be saying "what smell?" When you approach land after many days at sea it stinks badly so what are we fighting?

 

[TR6]

That is fantastic info, exactly what I was hoping for. I have hollows between the sides of the "false" and "liner" bilges. did you adress these as well ?

 

[Mike Culik]

TR6, I'm thinking of opening the false bottom up as allen12210 did with a multitool. The sides wont matter, they will drain down to the real hull bilge. That's why after thinking about it, the resin idea probably wouldn't help. Water could still be trapped.

Thanks to all for the great info and idea,

Mike

 

[TR6]

I have been to Home Depot today and picked up a 90 degree drive for my dremel, while I was there also got one of the larger vibrating saw gizmos as well, can't resisit getting "tooled up" so I'll be attacking the bilge in a couple of weeks. If you get there ahead of me, let me know how you get on with photos!!!)

 

[TR6]

update

The 31 doesn't have a hidden bilge like the 34. I did a number on the bilge area at the week end and found in the bottom of the bilge is a layer of fibreglass, some pieces of plywood and then the hull itself. The stink is caused by voids at the fore and aft ends of the bilge and at the sides of the bilge also. To make matters worse, the ply isn't fully encased so water gets trapped between the ply and the hull as well where the bedding material wasn't thick enough. The gap is maybe 1/32 of an inch but it's enough.

I dug out the bottom of the bilge, chiselled out the rotting stinky plywood and trimmed the sides of the bilge liner 3/4" from the bottom. The water now has nowhere to get trapped.

DO NOT drill down at this stage, this is the hull. I have to be a bit inventive now to mount the bilge pump and switch permanantly and will post more pics when finished.

 

[McZube]

TR6, since the odor is the ultimate concern, please let us know how this turns out. I have to do something about the smell on my H31. It has made its way to the top of the problem list.

On Sunday I got my foul-weather gear from the boat so I could use it outdoors during Sandy. Every time I put it on I could smell my boat.

I read somewhere that adding aerobic bacteria to combat the anaerobic bacteria would neutralize the smell. I might resort to that.

I'll never understand why Hunter designed the boat this way. Any time there's a leak at the holding tank, the seepage goes right into this space.

 

[TR6]

I'll keep you posted. I have been chasing the smell for years. I replaced the flex head hoses with solid PVC which made a big difference but finally got tired of the flush / sail / empty routine only for the smell to come back within a few weeks. Things came to a head (pun!) a couple of weeks ago when we were heeled further than usual in a race and the guy working the mainsheet nearly puked from the smell coming from below so I thought, that it ! I'm going to fix this once and for all.

I am also in the process of replacing the 26 year old upholstery and foam, have wiped all the hard surfaces with bleach and also white vinegar and am seriously thinking of ripping off the hull "carpet" and installing marine vynil or something similar. I am also going to add limber holes to ensure full drainage. Oh yes, I have purchased an ozone generator for good measure, hopefully I don't have to see if it works !

Re biocides, Busan and Kathon (trade names) will kill the critters, both aerobic and anaerobic (its only the anaerobes that smell) but I wouldn't recommend their use to a layman, they're not very nice materials to handle but I use them in my work. Also it would be another temporary fix.

I guess I have to ask, is the smell mould / mildew or rotting stuff ? the treatments for the two complaints are quite different.

I will be at the boat this week end so will see what has (or hasn't) happened.

 

[finding41]

TR6 do the biocides kill mold? I have a boat load of it. I tried TSP without much success however it's still kind of damp from topside leaks.
I plan to clean it out tomorrow and get in and power wash. (No carpet or fabric in the boat.)
I then plan to spray a super saturated solution of Borax everywhere I can get with my garden sprayer. Between the liners, in bilge, etc.
Am I wasting my time with the Borax?
Any direction would be greatly appreciated.

 

[TR6]

No biocides won't kill mould. There are a number of readily available products out there but I have used white vinegar, bleach, sunlight, all with some degree of success but not permanent fixes. I believe that anything that is organic has the propensity to grow mould so keep these materials (cotton / wool etc) out of the boat. Uncoated wood is also a prime candidate for mould growth and I believe at least 1 person on here has varnished things like the inside of hanging lockers, cupboards etc to seal them after cleaning which is something I am also going to do.

I see you are in Ontario, Try running a dehumidifier to keep the air in the boat dry once you have cleaned up. I have a buddy here on the West (wet) Coast runs one on his H45 and keeps bedding etc on the boat year round with no problems.

 

[NoggyTDoggy]

I know, as TR6 stated earlier, this topic has been beat to death.

But...I just acquired a 2000 Hunter 320. Would that boat have a "hidden" bilge as well ?

 

[mr c]

Even though this subject has been revisited many times, I have learned something new from this thread. I own a h31 and am in the process of drilling the superficial bilge. I have drilled the holes lower in the bilge with success. But more needs to be done. This thread with pics have given me more confidence to dig further. Thank u

 

[TR6]

Glad to be of assistance. Once I have finished I'll post more pics - It's still a work in progress right now. I can't stress enough that once the plywood is out don't go any further down, that is the hull you can see !