Major Refit of a Columbia 43

[LeighWebber]

Terra Nova -- it might be hard to get a 12:1 on the deck side of the joint, because the distance from the joint to the turn of the deckhead is only about 3 or 4 inches. I don't know how thick the hull is, but if it's a 1/2", I would need 6" of bevel above and below the joint in order to get a full 12:1.

There is a liner along only one part of the interior: where the dinette was located in the original layout. That's the only place where the hull was visible. I can grind it off, because none of that area will be visible after I make my mods.

So -- if I gut the interior sufficiently, I could grind from the inside as shown in my last sketch, then lay it up in the conventional way without any G10 or bolts. If this is acceptable, it would mean I wouldn't have to touch the outside at all. I just need to be sure to stop my grind when I reach the outer part of the H channel.

Anyone got any concerns about the strength of the resulting repair? It sure as hell would stop the leaks!

[Terra Nova]

Of course you have to "do" the outside, too, to seal it.

Nothing stops you from wrapping around the bend, a little, if necessary. But I really doubt your hull is that thick at the deck joint.

[LeighWebber]

Seal the outside? How could water get in? On the outside, the only thing left from the original would be the outer face of the H, which, after grinding from the inside, would simply be a strip of aluminum stuck to the outside of a solid span of FG. It would be just like gluing a strip of aluminum to a solid stretch of hull. Water might get behind the aluminum strip, but the hull wouldn't know or care. As long as I don't punch through that outer aluminum layer, you shouldn't be able to even tell from the outside that anything had changed.

[Terra Nova]

Originally Posted by LeighWebber

Seal the outside? How could water get in? On the outside, the only thing left from the original would be the outer face of the H, which, after grinding from the inside, would simply be a strip of aluminum stuck to the outside of a solid span of FG. It would be just like gluing a strip of aluminum to a solid stretch of hull. Water might get behind the aluminum strip, but the hull wouldn't know or care. As long as I don't punch through that outer aluminum layer, you shouldn't be able to even tell from the outside that anything had changed.

Oh my!

If water were not already getting past that outside, you wouldn't have this problem. It is not enough to glass the inside. You must also seal the outside, so moisture doesn't continue to penetrate the laminate.

[jimbunyard]

Leigh,

Terra Nova is right, if you use the G10 as shown in the diagram in your post 13, there is no need for it and it can be eliminated.

What I had in mind is shown in my first, drawn attachment. The strength is derived mainly from the combination of the bolts, the G10 and the bonding strength of the epoxy/milled fiber putty. The three wavy lines on the outside are meant to represent light fiberglass cloth that is mainly to seal the joint on the outside; it provides little strength, but adds fairing potential. The only other possible change I'd make would be to use silicon-bronze bolts. as a guard against crevice corrosion.

This method is unorthodox, and as such is just a suggestion of how I would probably do it. I take the often stated 12:1 ratio as a guide line for general practices, but do not consider it an absolute; I prefer to evaluate the situation and adapt my solutions to the problem at hand.

By no means am I saying this is the way you should do it. The suggestion to contact other owners to see what they've done is a good one.

And finally, the last 5 pictures show a repair I did that is closest to what you are going to do, butt join two panels. There are differences; the Cape Horn is a cored hull, and the panels didn't meet as cleanly as they will in your application, but you can get an idea of what is required and possible.

And if you're curious, that's what happens when you hit the exposed rigging of a sunken shrimp boat at 50 miles an hour. The only thing that stopped the cable from slicing that quarter of the boat all the way off was one of the motors, even so, the cable broke the gimbal housing right in two.

[LeighWebber]

New head. Here is my sketch of the new head:



The shower stall has fixed walls, behind the green panels marked A and B. There is a fixed fiberglass shower tray that I will fabricate to fit around the bottom of the entire head compartment (except for the vanity). It will have a drain leading to a gray water tank immediately below.


The green panels marked A and B will be made from frosted Acrylic (or similar) panels. When the shower is not in use, they will be positioned as shown by the solid green lines in the drawing. Each panel has a piano hinge. Panel A is hinged at the corner closest to the vanity, and B is hinged at the forward port corner. To use the shower, you pull panel A out in front of the vanity and clip it. Then you pull panel B out. It slides into a clip fastened to the back of panel A. Here's a detail showing this:



This creates a waterproof shower enclosure about 26" square (inside dimensions). When not in use, the panels swing back against the aft and inboard bulkheads. Panel B could have a towel ring glued on its outside face; the towel would stay dry during a shower.


Panel B might have to be split vertically in the middle, with a piano hinge. Otherwise, it might be impossible to open that panel while standing inside the shower (unless you're built like Twiggy). The hinge would solve that.

The drawback of all this is that the shower becomes a rigid enclosure 26" square. That's about 6" smaller each way than a typical residential shower stall. Even at this size, however, I think there will be enough room to bend down and pick up the soap if it falls. I'll have to verify this with a full-size mock-up, of course.


I have never seen this design, and I'm curious to hear what others think of it. The good news is that if the whole thing is just too nutty, I can simply remove the two panels and install a shower curtain. But I hate those pull-around sailboat shower curtains.

[LeighWebber]

Jim - thanks for the details and photos. Any idea how hard it would be to grind off the inside extrusion, depicted here:



Perhaps I could do it by cutting through the upper and lower shoulders, removing the outer shell. Next, grind through the horizontal part of the "H". Next, drill out the rivets. Finally, pry off the two vertical faces of the "H".
An alternative would be to work from the outside and grind at the horizontal part of the H until it is detached from the exterior vertical face (leaving two parallel strips of aluminum on the outside of the hull). Drill out the rivets, then pry off all the aluminum parts. This would avoid grinding/cutting aluminum inside the boat.
When prying off the extrusion, would it be OK to use a heat gun to soften the original adhesive? Or is there a danger of damaging the fiberglass?

[brantleychuck]

Warning! This is all " gut engineering "
So here is a question, how strong was the hull deck junction from the factory? I'm just guessing but probably not as strong as a continuos solid fiberglass layup. By keeping to the 12/1 rule that's what you are attempting to create, great if you can do it. So how strong does this joint need to be? So maybe a little wiggle room on the 12/1.
Now you could do this with polyester resin , keep to the 12/1 rule and come out with a by the book repair. Now do the repair with a high grade epoxy with superior bonding property's and maybe there is more wiggle room on the 12/1 rule. Not sure what your hull was laid up with but there might be mat in there so maybe a all cloth repair might give you a more wiggle room ( might be pushing with that one)
More of my " gut" engineering . So the book says 12/1 is perfect for making the area structurally equal to the surrounding structure. So is 6/1 ratio 1/2 the strength? My gut says no to that, maybe 10%. In your repair might be none at all. It all depends on we're the destructive load is coming from. Getting rammed from the side by another boat might show the 6/1 repair fail where the 12/1 theoretically would not , but who cares? There will be fiberglass work to be done in both cases.

If you do the repair from the outside removing the interior flange should be pretty easy as most the fastenings would have been compromised . It looks like it would easily be pried off. Of course access will play a large roll in how easy that job is. If you do have some access inside you can also remove the flange and add a few layers of fiberglass overlapping the joint generously creating a stronger joint and maybe adding to the 12/1 wiggle room even more.
If it was my boat I would be pretty comfortable going 3 inches either side of the joint. Doing a quality epoxy/ fiberglass repair using high quality materials. If you can then add some reinforcing on the inside so much the better.
I like a clean look myself. No trim . You want strength for sure but also water tightness, bolting structure on invites leaks .

Please let us know how you proceed and some pictures. Good luck


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[Jim Cate]

A comment from an unqualified observer: The original joint is so poorly designed (IMO) for structural robustness that most any repair/refit which includes glassing over the area has a very good chance of being stronger as well as less leak prone.

The reliance upon shallow spigots, flexible sealant and pop rivets surely does not imply much strength...

Jim