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Author Topic: Filling small aft hull depression  (Read 435 times)

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DaveBMusik

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Filling small aft hull depression
« on: May 01, 2021, 04:11:24 PM »

I know I have seen this posted but canít find it.
Has anyone filled the small area (water trap) in the hull behind the aft cabin bulkhead and what did you use?
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Dave Burgess
Water Music
1986 C34 Hull #206, Fin Keel
Yanmar 3YM30
Noank, CT

mdidomenico

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Re: Filling small aft hull depression
« Reply #1 on: May 02, 2021, 02:02:29 AM »

if you're talking about the valley in front of the rudder post, then yes i've filled mine.  i used epoxy foam, i can't seem to locate what i used in my email.  i'll have to check to see if i still have the cans.  it wasn't a particularly fun project, i'm not sure i'd bother to do it again
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1989 Cat34 #856, original mxp-25a

kh3412

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Re: Filling small aft hull depression
« Reply #2 on: May 02, 2021, 05:37:20 AM »

This was done on the boat as part of the transmission replacement. As part of the replacement had to remove the shaft. So wanted to put a new bushing in the strut but found the strut eaten away from electrolysis. So this had me looking at the strut to replace. As taking the strut off, kept getting a drip of water in the area. This lead me to grind some more looking for the source. What I found, the heavy roving that forms the hull in that area is covered with a finish fiberglass cap that has nice squared edges something the roving could not do. there is voids that water was in dripping out where the strut come out of the hull. This led me inside the boat where I found the area you want to fill. Pictures of that area show the cracks i had in the bottom that the water was coming from. There is a second area behind the rudder post also. this area holds water also and would recommend filling also.
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1987 mk1 a work in progress #618

kh3412

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Re: Filling small aft hull depression
« Reply #3 on: May 02, 2021, 05:57:45 AM »

I cleaned and ground the cracked area and applied 5 layers of biaxial glass with west system. Then poured a two part expanding foam into the areas and let it work. Came back the next day and ground sanded the foam down so the allow the water to run toward the bilge. This was covered with a few layers of fiberglass and sanded. Finished the project with bilge paint.
I believe that this may also cause some of the leaks people have gotten from the rudder post as it forms the back of the depression as it would be the thinnest fiberglass that the ice would push against.
This issue only really affects boats up north in freshwater.
The two part expanding foam was for, pour in floatation so I feel would be ok
Think this could be mentioned in the critical updates.

 
   
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1987 mk1 a work in progress #618

scgunner

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Re: Filling small aft hull depression
« Reply #4 on: May 02, 2021, 09:02:13 AM »

Dave,

I think I was the one who started the thread you're looking for, I think it was about 2 or 3 years ago, but I don't remember the title.

Just to review, I had three valleys (not just one) which were trapping water, the big one kh3412 is talking about, a smaller one just aft of it, and a larger but shallow one under the aft berth. My goal was to eliminate all standing water and create a smooth runway for any water to run to the bilge. I don't know what kh3412 found, but the valleys in my boat had some pretty nasty stuff in them along with the standing water.

What I did to remedy the situation was after thoroughly cleaning them out I shaped teak blocks to fill the voids then poured West Systems epoxy over them to seal a smooth the area. It worked very well and now there's no where for water to become trapped.

kh3412,

While I think this is a worthwhile thing to do, I'm not sure it rises to the level of a critical update. Maybe if you live in an area that freezes, but mine was like that for decades before I got around to fixing it.
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Kevin Quistberg                                                 Top Gun 1987 Mk 1 Hull #273

KWKloeber

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Re: Filling small aft hull depression
« Reply #5 on: May 02, 2021, 10:34:11 AM »

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Ron Hill

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Re: Filling small aft hull depression
« Reply #6 on: May 02, 2021, 01:59:16 PM »

Guys : Now that everyone has told how and what they used to fill that "scag" depression: 

I've never figured out where that water is coming from??   It is fresh water in my hull and it is NOT the overflow vent leak.  So I've often wondered if I had a hole in the top of the aft tank??

A thought
« Last Edit: May 04, 2021, 02:57:03 PM by Ron Hill »
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Ron, Apache #788

kh3412

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Re: Filling small aft hull depression
« Reply #7 on: May 02, 2021, 03:52:23 PM »

Ok found most of my water coming down the rudder shaft. To control the water coming from there installed a second nylon washer under the emergency cap that was epoxied to the deck. This gives me a 1/4" lip so water does not run right down.
Also had a leak in the rear water tank. Lot of places for water to get there as you can not see in that area, leaks at rails, dash panel,lazarets, and pedestal. But found most of mine coming down the rudder shaft.
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1987 mk1 a work in progress #618

Stu Jackson

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Re: Filling small aft hull depression
« Reply #8 on: May 02, 2021, 05:22:53 PM »

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Stu Jackson, C34 IA Secretary, #224 1986, "Aquavite"  Cowichan Bay, BC  Maple Bay Marina  SR/FK, M25, Rocna 10 (22#) (NZ model)

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scgunner

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Re: Filling small aft hull depression
« Reply #9 on: May 03, 2021, 08:03:24 AM »

Ken,

Yup, that's the one, thanks!

Ron,

I can't say positively where the water in my boat is coming from, stern shower and wash down or rain leaks possibly, but wherever it's coming from because I filled those valleys it ends up in the bilge, which is what I was after, no standing water. A dry boat is a happy boat!

I had a leak in the aft tank due to a small crack at the top of the tank. It would leak out about 6 to 8 gallons. The way to determine if you've got top leak is to top off the tank once a week. If you can't get any more water into the tank it's good, if like mine you can keep putting more water into the tank then obviously you've got a leak.

FYI, if you do have a leak, unfortunately the only way I know of to fix it is to pull the tank.
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Kevin Quistberg                                                 Top Gun 1987 Mk 1 Hull #273

Ron Hill

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Re: Filling small aft hull depression
« Reply #10 on: May 04, 2021, 03:07:01 PM »

Kevin :Thanks,  We might have the same problem as it only appears when I fill the aft tank to where it is coming out of the overflow.  I am painfully aware that to really find it - I need to pull the aft water tank!!  Way Toooo much work to solve that minor problem!!!

I'll wait and pull that aft tank when something else requires me to pull that tank.  Present solution - Just fill the aft tank to where the sound says it is full!!

A thought

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Ron, Apache #788

scgunner

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Re: Filling small aft hull depression
« Reply #11 on: May 05, 2021, 07:36:11 AM »

Ron,

Sounds like your leak could be same as mine. It was a small fracture at a corner of the small step at the top back of the tank. My problem was it would leak down and fill the pan that the tank sits on. When the boat heeled the water would rush to that side then overflow into the aft cabin, it took me months to figure out where that leak was coming from.

The fix involved patching the leak of course, but I also drilled holes in the back corners of the pan so if I get another leak it will drain to the bilge and not the aft cabin. If your leak is like mine , it's hard to see, it leaks in and under the cushions so it's not readily visible, you might want to check under those cushions.
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Kevin Quistberg                                                 Top Gun 1987 Mk 1 Hull #273

Stu Jackson

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Re: Filling small aft hull depression
« Reply #12 on: May 05, 2021, 08:20:03 AM »

Kevin,

I found that "puddle" when we first got our boat and it's been with me since 1998.  I have no evidence of any tank leak, but what work was required in patching the leak, what did you do?

I also haven't looked at the rudder tube stuffing box:  https://www.c34.org/faq-pages/techdata-rudder-packing-gland.html
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Stu Jackson, C34 IA Secretary, #224 1986, "Aquavite"  Cowichan Bay, BC  Maple Bay Marina  SR/FK, M25, Rocna 10 (22#) (NZ model)

"There is no problem so great that it can't be solved."

scgunner

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Re: Filling small aft hull depression
« Reply #13 on: May 05, 2021, 11:08:32 AM »

Stu,

I'd like to say I brilliantly diagnosed the problem and deftly tracked it down, but the reality is after looking unsuccessfully for it for months I stumbled across it while replacing the reefer compressor.

As far as the repair, I tried welding the crack a couple of times unsuccessfully and in frustration I cut a patch from a sheet of Dynamat and just slapped it over the crack, that was last year and amazingly it seems to be working!

Whatever you decide to do I'd recommend putting the drain holes in the water tank pan.
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Kevin Quistberg                                                 Top Gun 1987 Mk 1 Hull #273

Ron Hill

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Re: Filling small aft hull depression
« Reply #14 on: May 06, 2021, 02:44:14 PM »

Kevin : Many of the 1986 (first production year) C34 do not have an aft water tank!!

A thought
« Last Edit: May 06, 2021, 04:41:41 PM by Ron Hill »
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Ron, Apache #788
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