lemonade, OR adding a sump near the bulkhead, core repair

[Kushtaka]

I'm in it now, past the point of no return. I've drilled through the inner skin on my hull (deck) and removed quite a bit of rotten balsa from about 2-3" in each direction. Most of the rot is contained, but this area has multiple screw penetrations through the inner skin to service the bilge pump, that is protected by a fiberglass box that is ALSO screwed through the deck making more trouble. Now water does collect along the cabin bulkhead, but it sits mostly in the center (even though my boat then listed to starboard, it still didn't hold its water at the pump, or even near it. But it certainly held water where the many penetrations servicing the pump and protective box sit, allowing water to sit there constantly. I'm surprised the rotten core isn't much worse, but it must be addressed.

Because I'll be removing the inner skin of my hull to remove the affected core, and because my 1993 vintage hull is so thick, I believe I can add a sump the maintains the level of the centerline back far enough to starboard to accommodate a pump and switch, although I could make a slightly smaller sump and utilize an automatic bilge pump there and move my switch-activated pump aft to the transom sump.

At the same time, I'll be moving my kicker to a mini-jacker just to port of my main motor, and may add a third small dinghy motor on the old garelick bracket. This should balance the transom well and keep water from sitting on all of the penetrations that hold the pump in place.

Has anyone done this before? I'm aware that some newer boats have a sump on the opposite side of the cabin bulkhead, although the core forward of the bulkhead seems okay. If I'm going to do this, I think I'd be best off doing it where I already have to remove rotten core, not where perfectly good core exists.

So this area will have thickened epoxy between both skins here (i.e. no core) and should therefore be suitable for mounting a shoot-through-hull transducer. Does anyone have any experiences with this? I'm aware that any bubbles in the epoxy is going to make the transducer work poorly, but assuming I can get an even pour without bubbles, I should be able to do this, correct?

Thanks, in advance, for the input. This is a pretty big project that I wanted to get going the day I bought the boat. The screw penetrations have lingered in my mind, and I think about them most days when my boat is in the water. It will really free me up to obsess about something else, like adding an acr relay and a start batter, or my pot puller, or auto pilot, or radar, or a spot for my cooler and genrator and a radar arch or something I haven't even thought about yet, which I'm looking forward to!

 

[Sunbeam]

Always good to replace "is my core getting wet" thoughts with more enjoyable musings about new fun gear

I haven't done anything in the location you are thinking of, although my boat does have a core-free sump to starboard/aft under the galley as built, and later ones have a similar sump on centerline just inside the cabin door (these all went away when the "permanent" flat cockpit sole was introduced sometime around 2007).

But I did close out the core in the after sump (centerline at the transom), in somewhat similar fashion to what you are talking about (if I understood you correctly). If you are interested in seeing more about that, I have some photos/info in my boat thread, linked below. Essentially, I eliminated the thin core in the after sump. Reasons were a few: One was to make it deeper, as it was really shallow. Two was to eliminate the core there, which had been penetrated by previous pump screws (did turn out to be dry though). And three was because it was really an offshoot of the big goal, which was to eliminate the thin brass tube that used to be the drain-plug drain (which was not at all well installed). As little as my boat had ever been in the water (previous owner stored indoors and only had 50 hours use), there was STILL some moisture in the core there, and looking at the installation it was no surprise why. Luckily it was only a small amount, and came out as a part of the upgrade.

Starts about 1/3 of the way down this page (just scroll to the first photo):

http://www.c-brats.com/viewtopic.php?t= ... c&start=75

And then follow-up here (starts at the fourth post from the top):

http://www.c-brats.com/viewtopic.php?t= ... &start=105







By the way, I'm also thinking of doing a shoot-through-the-hull transducer, but in the no-core sump under the galley. That's about as far as I've gotten on it, but I'd like something that is not subject to the apparent voodoo that a transom mounted one is (?).

 

[thataway]

I have put in a number of shoot thru the hull transducers. Always use a baggie of water with the transducer in or above it, to be sure it will shoot thru this area. My favorite trick is to build a box, put in the transducer in mineral oil., But this would not be practical for the C Dory22. I have used epoxy, as well as silicon (without bubbles) and it works fine.

As I understand it, you are taking out the core, and putting in glass, down to the outer layer of the hull in the area in the cockpit, just aft of the cabin bulkhead. That the cabin bulkhead is fully glassed (tabbed) to the inner skin--but it will now need to be tabbed to the outer skin/new sump.

I would prefer to use a diaphragm pump, to the side, and a suction foot in the low area of the boat. Not sure if that is possible for your setup or not. The pump should be either set in place with screws which were potted in epoxy, or set on a wood block epoxied to the cockpit floor.

 

[NCPete]

Sunbeam-like you I did not want another hull penetration for the transducer. I had mixed results with the stick on transom mount.
I have had past success mounting the transducer in solid fiberglass areas of other boats. I epoxied my Garmin transducer (after discussion with Garmin) to the floor of the bilge under the stove (see photo in my album).
As Bob suggests confirm area with a baggie filled with water to be sure you can see thru the hull. My set up has been in place now for five years with success. I can accurately see the bottom (checked by charts) and I can also see fish. Temperature readings are possible but they are slow because the transducer sees the hull/water temperature.

 

[Sunbeam]

Thanks, Pete. I'll have a look in your album. Since I already have a transom mounted transducer (actually two), I'll keep one for the handy temp and speed, but I think I'll see what's available for the other head unit in a shoot-through-the-hull unit and try it in that sump under the galley. It's not the best bilge sump, being off-center, but maybe it will shine in this new use

 

[Kushtaka]

I have put in a number of shoot thru the hull transducers. Always use a baggie of water with the transducer in or above it, to be sure it will shoot thru this area. My favorite trick is to build a box, put in the transducer in mineral oil., But this would not be practical for the C Dory22. I have used epoxy, as well as silicon (without bubbles) and it works fine.

As I understand it, you are taking out the core, and putting in glass, down to the outer layer of the hull in the area in the cockpit, just aft of the cabin bulkhead. That the cabin bulkhead is fully glassed (tabbed) to the inner skin--but it will now need to be tabbed to the outer skin/new sump.

I would prefer to use a diaphragm pump, to the side, and a suction foot in the low area of the boat. Not sure if that is possible for your setup or not. The pump should be either set in place with screws which were potted in epoxy, or set on a wood block epoxied to the cockpit floor.

I think I get it. Put my transducer in a plastic bag full of water and press it to the spot where my core was removed to make sure there aren't interference from bubbles in the new epoxy core. I can then install the transducer to the sump if that works.

I have, in the past, cleaned my floor well with alcohol and used 5200 on the inside of the attachment screen's screw holes and a dab on the botom of each screw hole. It makes an hourglass shaped adhesive attachment and holds in my transom sump for about 8 months, but I'll secure with screws into my expoxy cored sump.

What I am not sure of is exactly what you mean by having to tab the bulkhead to the outer skin. Do you mean the outer skin of the cabin, or to the outer skin of the hull (i.e. the inside of the skin that makes the bottom of the hull?

 

[Sunbeam]

Kushtaka,

Something you said makes me wonder if I'm misunderstanding something. On the trandsducer mount, you mention wondering if air bubbles in your "epoxy core" will interfere with the soundings. But I was thinking you were making a sump something like I did, by removing the core. In that case you'd likely be adding cloth/resin (as I did), but why would you add "core" of epoxy? The way my sump ended up (and the way I believe my galley sump came from the builder) is just glass/resin. In other words it's basically the outer and inner skin tight together with no "filling" of core of any type. So a transducer would just be shooting through a thick(er) hull.

I think what Thataway means (again if I'm visualizing correctly) is that now the cabin bulkhead is tabbed to the top skin of the cockpit. If you were to cut out the top skin, dig out the core, and then "close out the core" by just laminating the new top skin straight to the inside of the bottom (skin/hull), then the cabin bulkhead would be "hanging" in mid air (about 3/4" above your new, core-less top skin). This is the case with my galley sump, but for that, C-Dory did leave it "hanging" (but the core is closed out) because they made it into a little slot that allows cockpit water into the under-galley sump (though it doesn't work all that well since it is off center if the boat is balanced port/starboard.

Or am I way off in what you are thinking about doing?

PS: Added photos:

This is the under-galley sump in my 2002 22 Cruiser. I realize this isn't what you are planning (and I don't recommend it really, in any case), but I thought it might be interesting to see anyway. In this first photo, yes, the core is closed out under the bulge - so there is no core at the bottom by the "slot."

The second photo shows it from the inside. The bottom of this sump is "core free" and is subsequently about 3/4" lower than the rest of the interior "sole." I imagine they did this to make is as sump-ey as possible. The photos aren't the best but I have them on hand.