Concrete cast keel

[Fishguy]

Looking at a home built mono with a concrete fin keel filled with lead & cast steel pieces.
The concrete is painted with copper coat bottom paint same as the rest of the hull below the wate line.
The concrete finish is ruff.
My question is shouldn't the concrete have been smoothed and faired with epoxy filler and then painter with epoxy primer and then painter?
The boat is in freshwater Canada where the winter temps can get into the -30's. Boat get hauled out for winter.
My concern is the possibility of the keel to absorb water, freeze & crack.

Any thoughts??

[billknny]

Originally Posted by Fishguy

Looking at a home built mono with a concrete fin keel filled with lead & cast steel pieces.
The concrete is painted with copper coat bottom paint same as the rest of the hull below the wate line.
The concrete finish is ruff.
My question is shouldn't the concrete have been smoothed and faired with epoxy filler and then painter with epoxy primer and then painter?
The boat is in freshwater Canada where the winter temps can get into the -30's. Boat get hauled out for winter.
My concern is the possibility of the keel to absorb water, freeze & crack.

Any thoughts??

So this boat has a cast concrete keel filled with both lead and steel scrap that is then bolted to the hull? That sounds like the worst of all possible worlds...

Usually boats that had a cast concrete keel with extra metal for weight had the concrete INSIDE a fiberglass shell.

There are so many questions...
Is there a proper re-enforcing grid in the concrete?
Is there any trace of rust from the internal steel scrap?
How are the keel bolts attached to the keel?

I am not sure how "ruff" it might be, but anything other than smooth costs a lot of power and speed. Just like layers of marine growth.

[Cheechako]

Yeah, the ones I've seen were concrete inside the glass keel. I'm not sure what you describe wouldn't be OK if done right but not fond of it. Concrete as a filler isn't that bad, commercial fishing boats were done that way a lot. My old Rawson 30 was done that way. They were a fishing boat builder before they started building those sailboats.

[AndyEss]

How old is the existing keel/boat? Is there evidence of existing freeze cracking?
You might induce what you fear by “sealing” the concrete keel with epoxy. Small leaks will fill the concrete pores, but the epoxy will keep it from draining and drying when the boat is hauled in the fall.
You might grind/polish the concrete so it is smoother. Diamond grinder wheels are available for finishing concrete at reasonable cost

[Fishguy]

Yes the fin is about 4' down from the hull X 6' long where the keel meets the hull X 12" wide where the keel meets the hull.
It tapers at the bottom.
It'rougher than the finish on a side walk.
Yes reinforcing steel inside with stainless bolts to attach through the bottom passing through the stringers.

[Cheechako]

Originally Posted by Fishguy

Yes the fin is about 4' down from the hull X 6' long where the keel meets the hull X 12" wide where the keel meets the hull.
It tapers at the bottom.
It'rougher than the finish on a side walk.
Yes reinforcing steel inside with stainless bolts to attach through the bottom passing through the stringers.

Is that the only ballast? It almost sounds like someone added that for more ballast after the fact. There is nothing in the part above the 4 feet down? You mean the keel is 4 feet from the hull then the cement is added... right?
Based on the rough finish etc, it woulds to me like it's not well done. Good hydraulic cement can be smoothed real nice and smooth.

[Fishguy]

The boat is 27 years old.
Some of the small gravel stones are exposed near the surface and a seam of concrete where 2 of the boards came together and wet concrete squeezed out has not been sanded down.
I think some of the surface concrete has either worn away or has flaked off due to moister freezing. So to repair would take some fairing & sanding.

[Fishguy]

The whole fin keel is the ballast.
So he made a form and poured concrete & lead into the bottom and then layers of concrete and cast steel for the rest until the form was full. This was done in 1 pour which took a full day. Reinforcing steel & the keel bolts were set into the concrete as is was being poured.
Then once the concrete had cured the wood form was removed.
I don't know how ruff it was when it first came out of the form.
But it's pretty ruff now, so was wondering about what is would take to clean it up. Not interested in making a new ballast keel.

[AndyEss]

Grind it some and use portland cement based troweling mix to fair out. The keel has apparently performed satisfactorily for 27 years, so changing the coating to impermeable (you hope) epoxy seems like running an experiment on a working solution.
In this case, if it ain’t broke, don’t fix it.

[Orion Jim]

Might be prudent to just walk away. If this is the finish on the stuff that shows just imagine what doesn’t show.

[billknny]

Originally Posted by Fishguy

Yes the fin is about 4' down from the hull X 6' long where the keel meets the hull X 12" wide where the keel meets the hull.
It tapers at the bottom.

That seems to me to be a really bad shape for a material--like concrete--that is really only strong in compression, and is quite weak in tension.

Is this a boat that will stay in the lake or are you considering it for open ocean work?

[Cheechako]

Originally Posted by billknny

That seems to me to be a really bad shape for a material--like concrete--that is really only strong in compression, and is quite weak in tension.

Is this a boat that will stay in the lake or are you considering it for open ocean work?

That's true, but entire boats were made of concrete and seemed to do pretty well, albeit not popular. Still, it comes down to expertise...

[psk125]

Can we all agree that having smooth underwater surfaces is important on a boat? Can we also agree after looking at any poured basement wall that getting a relatively smooth concrete surface is not difficult to achieve? (All they do for basements is to wax or oil the plywood forms.) If the builder of this boat has neglected to do something important (smooth surface) that is relatively easy to do (wax the forms), it would seem likely that he may have neglected other important things that are more difficult to do. We don’t know. Even if the rest of the hull was built to Hinckley standards it sounds like this keel needs to be cut off and re-done properly, from scratch. If the hull is built to the same standard as the keel, it may be more valuable as scrap than as a boat.

[mvweebles]

Willard trawlers used concrete ballast with steel punching for additional weight and strength. All ballast is internally poured. Still, after 50 years or so of a wet bilge, not uncommon to have it swell and deform.

Bottom line - external concrete ballast is an awful idea. If the surface is rough it's because it has spalled over the years, a process that will accelerate over time.

You do not want this boat. It is best suited as a reef.