Fin keels - Moulded or attached fin?

[Neil_Y]

We mould metal powder into composites so we could make a very heavy solid composite moulding, but we'd need a very big high pressure mould.

Now there's an idea...

 

[sailorman]

Until you hit something and the encapsulation fails.

Bolt it on. Have access for maintenance.

Example 1)

How can you torque the bolts if they're laid up in GRP?

Example 2)

How do you drop the keels 3" every 3 years to renew sikoflex and retighten?

Example 3)

If you're trying to pull speed from the boat - you should have bought something faster in the first place.

Why drop every 3 yrs to renew sikaflex

 

[geem]

Why drop every 3 yrs to renew sikaflex

The keel on our boat appears to have been made from lead encapsulated in GRP with keel bolts imbedded in the lead then the whole thing was bolted to the bottom of the boat. The bolts were glassed over and the keel to hull was heavily laid up (somewhere over an inch of glass). Done to Lloyd's 100a1 a long time ago. Lead keel weighs 6 ton. There is no visible sign of a join.

 

[ganter]

Why drop every 3 yrs to renew sikaflex

Offshore.

Little bit of hull flexing.

Drying out mooring.

Sikaflex is great but it don't last forever.

 

[Birdseye]

Bolt on but lead attached to a decent sump. Seen too many damaged and leaky encapsulated keels. Plus their aspect ratio is all wrong

 

[doug748]

And lo.

A seamless monocoque. No leaks, no joints and a material that let you build in strength just where it is needed. A perfect small boat, a perfect piece of engineering elegance. We had finally arrived.

Then some bright spark thought:

"I know, why don't we drill a load of holes in the bottom and hang a iron casting on the bottom. Just like the old days, something to worry about and cheap as well"

 

[ganter]

And lo.

A seamless monocoque. No leaks, no joints and a material that let you build in strength just where it is needed. A perfect small boat, a perfect piece of engineering elegance. We had finally arrived.

Then some bright spark thought:

"I know, why don't we drill a load of holes in the bottom and hang a iron casting on the bottom. Just like the old days, something to worry about and cheap as well"

Good theory. Can't fault it. Wouldn't want to. But you're missing out on one factor...Neptune.

What happens with you greedy racers when you "bump" the bottom of that sand spar when you're going about a little wide of the marker, your encapsulation tears and fails and you have nothing to tighten or repair the boat with except a lot of ragged GRP that needs complete renewal? And with only a metal detector to try and find your keel with that's now on the bottom.

Keel bolts hold the keel on. Encapsulation pretends to do this providing you don't ever aground it, run it ashore, hit anything, or any of the other slings and arrows that boats are heir to.

 

[sailorman]

The keel on our boat appears to have been made from lead encapsulated in GRP with keel bolts imbedded in the lead then the whole thing was bolted to the bottom of the boat. The bolts were glassed over and the keel to hull was heavily laid up (somewhere over an inch of glass). Done to Lloyd's 100a1 a long time ago. Lead keel weighs 6 ton. There is no visible sign of a join.

Mine is 3 tons fin keel ( see #10 ) made of lead bolted on & no sign of any movement @ the hull / keel joint since re bedding 12 yrs ago

This was @ haul out last year showing the joint

 

[Kelpie]

Keel bolts hold the keel on. Encapsulation pretends to do this providing you don't ever aground it, run it ashore, hit anything, or any of the other slings and arrows that boats are heir to.

My own boat, the Vega, was designed to withstand a head on grounding on rock at 6kt. And, erm, I can attest that it can indeed do this

Edit: encapsulated keel, btw.

 

[sailorman]

My own boat, the Vega, was designed to withstand a head on grounding on rock at 6kt. And, erm, I can attest that it can indeed do this

Edit: encapsulated keel, btw.

How does she go astern :disgust:

 

[Kelpie]

Just as badly as she would if the keel was bolted on.

 

[DJE]

Strangely quiet. I would have expected the catamaran crowd to have waded in by now!

 

[Neil_Y]

Failed encapsulated keel, do you really know what is going on inside your keel?

"The builder has added bits of scrap iron, steel, and probably anything else he could get his hands on to add weight to the poured concrete ballast (concrete is not very heavy, particularly as compared to lead). Once water seeps into the ballast (from the bilge or possibly via hull damage) the metal scraps begin to rust and expand, causing the FRP of the hull to crack and rupture. The voids in the concrete indicate where metal scraps were located."

At least with a bolt on you can inspect all the elements, so for offshore I feel more comfortable with a keel that has been inspected re bedded, bolts pulled and checked or renewed.

or this, would the ballast have fallen out?

 

[geem]

Failed encapsulated keel, do you really know what is going on inside your keel?

"The builder has added bits of scrap iron, steel, and probably anything else he could get his hands on to add weight to the poured concrete ballast (concrete is not very heavy, particularly as compared to lead). Once water seeps into the ballast (from the bilge or possibly via hull damage) the metal scraps begin to rust and expand, causing the FRP of the hull to crack and rupture. The voids in the concrete indicate where metal scraps were located."

At least with a bolt on you can inspect all the elements, so for offshore I feel more comfortable with a keel that has been inspected re bedded, bolts pulled and checked or renewed.

or this, would the ballast have fallen out?

Or have a professionally constructed lead encapsulated keel rather than a diy bodge job that resembles landfill.

we met some Swedes in Caribbean in 2005 who had a new Elan with the steel grid in the bilges and a bolt on keel. They had sailed across the Atlantic and noticed water in the bilge. It got worse and they had to mop and pump the bilge everyday. They contacted Elan on arrival in the Caribbean. They didn't know why the keel was loose. The boat was shipped back to Europe to the factory. The boat didn't sink but it must have been very disconcerting to be sailing across an Ocean not knowing if the keel was going to fall off! They hadn't hit anything they were aware of and believed it was a manufacturing or assembly problem.