keels: genuine question.

TiggerToo

TiggerToo

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I am not a Bavaria owner, but could someone explain to me why fully encapsulated keels are necessarily better than bolted on ones?

In the event of a catastrophic collision at speed, would the encapsulating GPR not be damaged and let the water in this compromising keel and boat? Would the resulting water penetration not be a long term problem for anyone buy such a boat if it were not repaired properly?
 
I think that the advantage is not collision related - your points are valid that regard.

The advantage is that, on a normal use basis, there is no join between the keel and the hull which can let water in to affect the keel bolts. And no rusty lump that needs attention now and again.
 
Encapsulated keels have two distinct advantages (although others may add to this)...

1. the keel is part of the structure of the hull, there are no keel bolts to check/fail

2. If damage is done to the keel through grounding it is unlikely that water would enter the boat as the keel is normally filled (at least at the bottom) with lead/grp. There will however be localised damage/grp that could absorb water and take time to dry out if left. Repair is relatively straightforward once dried out.

Hope this helps.
 
I know of two boats with encapsulated keels both of which suffered from water ingress in to the ballast area. The damage was caused in one instance a rather hard grounding, the other I suspect she was dropped by the boat yard.

One had a lead keel and after much drying out. (drill holes through the glass, inset wicks and wait a long time)

The other had cast iron ballast + water penetration = rust and the grp just spalled away.

You pays your money and you takes your choice.
 
I'd be grateful if someone would explain what an encapsulated keel is. I think I have one (there is no join visible between keel and hull, it seems to be one moulding) but I do have keel bolts.

rob
 
An encapsulated keel is where the canoe body and the keel are a single moulding and the ballast is lowered in and glassed into place. The ballast can be a shaped lump, pigs or Belfast confetti (aka metal punchings).

It sounds like you've got a bolted on keel that is then faired with a sheath of grp. The sheath can extend over the whole keel area or be a bandage over the hull/keel join.

Some boats have a very odd system where the ballast is placed in a moulded keel/pocket and then the moulding is bolted to the hull.
 
Perhaps this sketch will help:

keels514x236.jpg
 
Can't find the thread right now but I seem to recall that a forum member attempted to move Scotland over a few feet buy means of his keel. The keel was damaged but as far as I am aware the hull was undamaged. That was a heavy duty encapsulated keel. I would be surprised if a bolt on job would have survived so well.

Disclaimer - I have an encapsulated keel and would say this.....
 
The truth is that an encapsulated keel isnt necessarily any better - it all depends on how the two keels you are comparing have been executed.

That said, the narrow wine glass type hull cross section that goes with an encapsulated keel is naturally more rigid to compression than is a flat floored boat to which has been bolted an iron keel. So you have to work harder and use more material to give a flat floored boat like a Bav the same strength - and that goes against the grain when you are selling cheap boats.

Its easy to put stringers across the boat to help resist sideways leverage on the keel, but builders are less keen on strengthening lengthwise when by definition the only time it mattera a lot is when you do something daft and hit things.

There is another issue with the trad encapsulated keel - the sloping profile of the keel can help a boat to rise over an obstruction and thus slow down less quick and put less strain on anything. By comparison a deep fin keel hitting an object can cause the keel to stop dead, the bow to lunge downwards and then the bow to stop dead when that hits something . So the deceleration may be much sharper and the forces involved much greater.

Having said all this, I have personally seen three encapsulated keel boats in serious trouble after impacts, and I've yet to see a fin keeler (several bilges but no fin) That may well be accident, but I personally wouldnt like to rely on GRP in a serious impact situation. Its a weak material impact wise.

To sum up - flat floored fin keel boats can be made strong enough and usually are in Scandinavia where there are lots of uncharted rocks. But that is done at a cost and is one reason why Bav and Benny are half the price of HR. You get what you pay for.
 
I've had various encapsulated keels, and sometime abused them.. The Corribee is made as a hollow plastic boat and then filled with a slurry of shot or similar and resin.(allegedly) I damaged mine by wearing away at LWS and when it was lifted, I saw a pandora's box of nothing underneath. It was empty at the worn bit. The shipman 28(iron lump) and ericson39(lead lump) both had bolts. The shipman showed a small crack at the forward keel/hull root, and bash damage at the front after an incident. It leaked out of the mould seam ( like some rudders) on lifting out. The ericson's bolts attached through the hull to steel floors inside, as in brick sh!thouse. I couldn't damage it. Can't see any signs of bolts in the claymore, which is a pity, as I want to connect a wire to the keel.
So, in conclusion, it's not just the plastic you have to think about, it's what's inside
 
As with everything related to yacht design there are compromises. In the early days of GRP construction designs were mainly developed from traditional wood construction where the wineglass shaped hull form with full keel was dominant. That hull shape is difficult to mould (at least the underwater bit) and make it strong enough to hang a big lump on the bottom with bolts. Hence the attraction of an encapsulated keel. However, many hulls were moulded in two parts split longitudinally because it was difficult to lay up the deep and narrow keel pocket. Joining the two halves together creates its own problems. The best of this type then used a lead casting which kept the weight low and minimised the negative consequences of water getting in. Others compromised with iron castings of steel punchings set in resin. Consequences of these solutions are obvious.

Then in the late 70's designers discovered that the one piece canoe body and separate keel foil not only gave better performance but strong hulls could be built using less material. Put a Nic 32 alongside an early Angus Primrose Moody 33, both in production at the same time, and you will see the fundamental differences in design philosphy.

The Primrose approach is now dominant, although there is still room for the Nicholson style (or modern developments), but the price differential tells it all.

The great thing is that we all end up with an endless range of choice that allows us to choose a boat that matches our own requirements.
 
There have been a few cases of damage to encapsulated keels (and skin fittings) when hit by lightening. I gather that it is becoming more common to fit lightening protection systems including grounding plates under the water in some parts of the world.
 
Thank you, that's helpful. I don't have an encapsulated keel then but I do have a scandinavian boat which according to a later poster should make me feel reassured!

rob
 
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