Theoretical Keel Question (Encapsulate a Bolt-on)

[GuidoY]

If one were so inclined, and had the resources, would it be possible to encapsulate a bolt-on keel? Would it be advisable?

That is, grind back glass on and above the stub, graft new glass in, encapsulate keel, fill, fair, gel, etc.

I like having solid lead, and bolt-on is fine, but just wondering in case I want to upgrade the strength or make it more suitable for longer passages.

This seems like a good compromise/approach, but I'm not in the market right now.

[neilpride]

Question could be,,,, WHY?

[skipmac]

Last boat had a bolt on keel and it annoyed me. Every time I hauled the boat there was a seam visible between the keel and hull. Never saw any evidence of imminent failure or significant working but worried that the water in the seam could lead to crevice corrosion on the keel bolts.

Current boat is encapsulated and I like it better.

Theoretically you could do this but note the encapsulation is more than just a skin. The glass over the keel is thick and structural. If you didn't make the glass covering very heavy and well bonded to the hull I think it would very quickly crack and separate.

[antoha]

Just curious - what do you gain by doing this? i don't think you make it stronger (you're not modifying the attachment method, unless i misunderstood you), just slicker and prettier - until the first grounding, i suppose.

our boat is not a racer, and the ballast is external - just a big blob bolted onto the forward lower part of the keel. judging by its current surface quality, i'm glad it's not encapsulated...

[valhalla360]

If you do it, you have to basically assume that the keel bolts will fail and can't be replaced.

Therefore the fiberglassing needs to be strong enough to hold the keel by itself without help from the bolts.

[Pete7]

Getting GRP to stick to cast iron with a really good bond is going to be difficult. Stopping it rusting underneath nearly impossible if its been in saltwater before. I have twin cast iron keels, they require minor touching up each year as the rust breaks through the paint. This isn't a problem and the keels will still be around when I am long gone, it just looks unsightly after a year afloat. However, expanding corrosion under a GRP finish will just carry on spreading with no hope of treating it.

Pete

[DefinitelyMe]

Originally Posted by Pete7

Getting GRP to stick to cast iron with a really good bond is going to be difficult. Stopping it rusting underneath nearly impossible if its been in saltwater before. I have twin cast iron keels, they require minor touching up each year as the rust breaks through the paint. This isn't a problem and the keels will still be around when I am long gone, it just looks unsightly after a year afloat. However, expanding corrosion under a GRP finish will just carry on spreading with no hope of treating it.

Pete

Do the Tartans have cast-iron keels? Are they like the Beneteaus where the bolts thread into the keel from the top and can therefore be replaced?

I can't see why you couldn't encapsulate a keel. I believe it owuld have to be done from epoxy rather than polyester however if you wanted it to bond at all to the metal, and then you're talking $$$ for the kind of quantity you'd need to encapsulate the whole keel.

[chris95040]

Just to be clear, the idea of an amateur "encapsulating" their bolt-on keel such that the encapsulation is now the primary support is _ridiculous_.

I'm a pretty overly optimistic DIYer, but the work (and the engineering) to do this is STAGGERING.

If you don't like your keel bolts, replace them!

[model 10]

[QUOTE=chris95040;1899105]Just to be clear, the idea of an amateur "encapsulating" their bolt-on keel such that the encapsulation is now the primary support is _ridiculous_.

It would only be "ridiculous" if your keel bolts tended to get loose. Surely there must be boats where that does not happen?
I don't see an obvious line where the keel attaches as unsightly. It's just the way it is.

[GuidoY]

As to the why, I suppose to increase the strength. To make it structurally sound the glass would have to be as thick as the hull (?). Granted, dynamics of the fin would change, probably not for better. Lead keel & stainless bolts are holding up fine, just thinking of how to make it more permanent. There's always 5200 I suppose . (But seriously, I have heard of 5200 holding a keel on after bolts were removed for service).
Ridiculous? Perhaps good sir. But each of us, when we look deep inside, will find an Everest.

[neilpride]

If your keel is fine, bolts are sound, no leaks , no cracks no gaps, leave it like that, otherwise is a huge waste of money aka gallons of epoxy and material and no benefit at all.... I see few people in the boatyard doing weird things in their keels, a Kirie feeling with a big gap at the aft trailing edge , instead of drooping the keel or retorque the bolts they screw a strap between the keel and the stub, WTF... the strenght is intact if you keep your keel bolts in good order and the framing structure sound, after all is a bolted fin keel....

[bsurvey]

you will make the area un inspect-able and if you ever grounded the boat you would have to tear it all out to get to the stubby and any hull damage


you gain no extra strength from poured epoxy on top

[TrentePieds]

[QUOTE=GuidoY;1899173] just thinking of how to make it more permanent. There's always 5200 I suppose


Make a virtue of necessity: Enhance the joint by running a nice little cove along it, then run a contrasting colour of antifouling into the cove . The fish will think it's funny. Or they won't care. ;-)

Seriously, I think well enuff is best left alone in this case. There are very few of us who haven't touched bottom once or twice. And if you do that with sufficient conviction somewhere along the way, the necessary repairs would be rendered IMMENSELY more difficult if the keel had been encapsulated retroactively!

TrentePieds

[GrahamHO]

I replaced my fin keel 5 years ago. Not your type of keel but the attachment method might interest you. I used 6 keel bolts though really studs machined from 2205 SS stock. . Some of the bolt threading for the retaining nuts was to be inside the hull. We used a very high density epoxy mix placed on top of the not yet attached keel. The bolt holes in the hull were made about 1/4" oversize.
Using a travel hoist we lowered the vessel onto the keel which was mounted in a frame.
The epoxy mix was attended to and oozed up the bolt holes with someone inside applying more into the holes to make sure it penetrated. I had made a big sandblasted and epoxy painted 10 mm mild steel plate with holes to match the keel bolts. From the inside this was fitted over the now protruding keel bolts and bedded in the same epoxy mix on top of the keelson
The plate is the width and a little longer than the top of the keel and spreads the load.

Once the nuts were in place and initially tightened the boat plus keel was lifted by the travelhoist until it was swinging. Then the keel bolts were tightened on one side or the other
adjusting the sideways angle of the keel until it lined up by eye with the rudder viewing from astern.
The whole lot was left swinging overnight for the epoxy to set. That is the shape a boat is when floating and it sets that way. Don't leave the boat resting on the keel while the epoxy sets.
In the morning it was rested on the new keel and propped up.

That keel has practically all the ballast in a bulb similar to much larger America's Cup monohulls. That's a potentially high stress keel and there has been absolutely zero cracking at the interface. It is virtually one piece with the hull.

To remove such a keel an extended hole saw that fits around the keel bolts with the nuts removed is used to drill down into the hull over the keelbolts until it reaches the keel. That's how we removed the old keel. Very easy.

It's become quite a common method to attach keels in Auckland NZ and bulb keels are plentiful there.

I can already imagine old salts shaking their heads in horror but it is a very sound method for a glass yacht. Measuring the next morning there was only 5 mm difference from the centre of the bulb to either gunwale.
The same method works fine with a longer keel as I imagine yours is.

[minaret]

Originally Posted by GrahamHO

I replaced my fin keel 5 years ago. Not your type of keel but the attachment method might interest you. I used 6 keel bolts though really studs machined from 2205 SS stock. . Some of the bolt threading for the retaining nuts was to be inside the hull. We used a very high density epoxy mix placed on top of the not yet attached keel. The bolt holes in the hull were made about 1/4" oversize.
Using a travel hoist we lowered the vessel onto the keel which was mounted in a frame.
The epoxy mix was attended to and oozed up the bolt holes with someone inside applying more into the holes to make sure it penetrated. I had made a big sandblasted and epoxy painted 10 mm mild steel plate with holes to match the keel bolts. From the inside this was fitted over the now protruding keel bolts and bedded in the same epoxy mix on top of the keelson
The plate is the width and a little longer than the top of the keel and spreads the load.

Once the nuts were in place and initially tightened the boat plus keel was lifted by the travelhoist until it was swinging. Then the keel bolts were tightened on one side or the other
adjusting the sideways angle of the keel until it lined up by eye with the rudder viewing from astern.
The whole lot was left swinging overnight for the epoxy to set. That is the shape a boat is when floating and it sets that way. Don't leave the boat resting on the keel while the epoxy sets.
In the morning it was rested on the new keel and propped up.

That keel has practically all the ballast in a bulb similar to much larger America's Cup monohulls. That's a potentially high stress keel and there has been absolutely zero cracking at the interface. It is virtually one piece with the hull.

To remove such a keel an extended hole saw that fits around the keel bolts with the nuts removed is used to drill down into the hull over the keelbolts until it reaches the keel. That's how we removed the old keel. Very easy.

It's become quite a common method to attach keels in Auckland NZ and bulb keels are plentiful there.

I can already imagine old salts shaking their heads in horror but it is a very sound method for a glass yacht. Measuring the next morning there was only 5 mm difference from the centre of the bulb to either gunwale.
The same method works fine with a longer keel as I imagine yours is.

Recently pulled a keel on a Farr built this way (Carrol Marine). I hated it, made it much much more difficult to remove the keel. When I reinstalled it, in collaboration with Farr Design Group, I suggested we install in a more traditional (ie both flexible and removable) fashion. Farr Design heartily concurred.