Best way to attach a keel

[pmagowan]

OK, so imagine you are building a boat from scratch. What is the best way to attach a keel assuming it is a 'short' long keel (or a long fin keel)? Bolts, encapsulated, glue? What are the major considerations? I remember Vyv mentioning keel bolts that showed if they lost tension.

 

[Ric]

OK, so imagine you are building a boat from scratch. What is the best way to attach a keel assuming it is a 'short' long keel (or a long fin keel)? Bolts, encapsulated, glue? What are the major considerations? I remember Vyv mentioning keel bolts that showed if they lost tension.

If you want to be absolutely sure you will never lose your keel, go for internal ballast with a long, deep centreboard (e.g. like the newer generation of French aluminium centreboarders). You would get better performance than the keel you desire in a wider range of conditions - especially downwind and even upwind if the centreboard is deep and decently profiled. Your only performance handicap would be in light winds where the additional ballast needed to get a decent righting moment will be a handicap.

 

[pvb]

An encapsulated keel makes a lot of sense, and spreads the loads very evenly over the boat's structure. But encapsulated keels aren't easy to build, and tend to be fairly chunky in terms of width.

Glue isn't strong enough.

Bolts are strong and work well in most cases, as long as the hull structure is designed appropriately for the loads.

 

[Sailfree]

As a structural engineer I have always liked the X boat/Arcona solution with an internal frame consisting of a long beam and C shaped ribs going up to strong points to take the rigging load. Mast sits on bottom beam. Therefore boat hull sits as the middle of a sandwich between the keel and the internal structural frame.

Both X boats and Arconas are performance cruisers tending towards racers if you go for a bigger more powerful rig. For me this is one of the best ways of achieving a good fin keel construction.

WRT ballast ratio I don't know how Arcona calculate it but was surprised that X boats include the internal frame and the keel as the ballast weight. personally as the internal frame reaches up to the deck to take the rigging load I think its stretching the point a bit but my info may not be accurate as its from a X boat salesman.

Unfortunately none of these boats were available as a deck saloon so I went for the jeanneau where there is exposed and visible internal GRP stiffening of ribs and beams/stringers. unfortunately to be competitive Jeanneau have joined all the production boat manufactures and stick an internal egg crate (to form the ribs and stringers) inner hull to an external hull which gives maximum strength to weight in GRP and is cost effective but difficult to identify damage after any impact/groundings.

 

[Tranona]

There is an ISO standard for designing attachments for appendages. Nothing magic about the subject and in your proposed design/construction, bolts, or more likely studs will be perfectly adequate, but you will need to consider casting in a framework for the studs if you are using lead, and the depth of keel makes through bolts impractical. All covered in the standard, and if you read the MAIB report on Cheeki Rafiki you will find out not only the relevant standards but also a useful discussion on its application. As that incident shows, fastenings are perhaps less of an issue than the structure that spreads the loads to the hull.

Having said that , some designers have used glued on ballast keels on wood/epoxy hulls, notably Andrew Simpson who has designed and built several 40 footers with this method.

 

[skipmac]

Have had all types, well except for glue, and for the most security, long term peace of mind and zero maintenance issues an encapsulated lead keel is my preference. This of course assumes it is properly constructed.

 

[Sailfree]

Have had all types, well except for glue, and for the most security, long term peace of mind and zero maintenance issues an encapsulated lead keel is my preference. This of course assumes it is properly constructed.

But this will never be a performance boat just a traditional heavy slow cruiser.

Does anyone sell these boats new anymore. I do say sell not offering to build at an uneconomical price!

 

[doug748]

But this will never be a performance boat just a traditional heavy slow cruiser.

Does anyone sell these boats new anymore. I do say sell not offering to build at an uneconomical price!

Ah, schoolboy error.

Answer the question set.

 

[skipmac]

But this will never be a performance boat just a traditional heavy slow cruiser.

Does anyone sell these boats new anymore. I do say sell not offering to build at an uneconomical price!

Well my boat, with a GRP encapsulated lead keel, has a modified fin and would not call it a traditional, heavy, slow cruiser. Not a racer but no dog either.

Since I have a boat and budget doesn't allow for new anyway I am not 100% up to speed on all the new models but I do believe there are at least a few makers still using this technique.

 

[LadyInBed]

When I was looking to change my boat two of the below water requirments were twin GRP encapsulated lead keel and skeg hung rudder.

 

[PhillM]

Island Packet?

 

[jwilson]

When I was looking to change my boat two of the below water requirments were twin GRP encapsulated lead keel and skeg hung rudder.

Encapsulated is fine as long as you don't want to dry out on sharp rocky or shingly bottoms, or ground hard on a rock. If you do you can get GRP damage. Fixable with sacrificial shoes, but not many boats have these. My ideal is a bolted-on lead keel, with pockets in the sides of the keel casting for nuts on studding. There is a massive difference in shock transmitted up to the hull/keel facing (and hence hull damage) between lead that gives/dents a bit on impact, and cast iron that just doesn't.

 

[doug748]

Encapsulated is fine as long as you don't want to dry out on sharp rocky or shingly bottoms, or ground hard on a rock. If you do you can get GRP damage. Fixable with sacrificial shoes, but not many boats have these......

True enough. I would never want to dry out this type of boat regularly. I had a plastic Folkboat and when I jacked it off the floor for epoxy painting under the keel, much of the gelcoat had been stripped off, down to exposed mat.
I am not sure that metal shoes don't bring even more problems, with loose fixings etc. Perhaps a bonded on shoe would be best. In fact it is probably more sensible just to choose something more suitable for a boat that needs to take the ground.

 

[pmagowan]

Mine would need to be able to take the ground as I practice hydrography by impact as a subtle art form.

 

[aluijten]

As a structural engineer I have always liked the X boat/Arcona solution with an internal frame consisting of a long beam and C shaped ribs going up to strong points to take the rigging load. Mast sits on bottom beam. Therefore boat hull sits as the middle of a sandwich between the keel and the internal structural frame.

Both X boats and Arconas are performance cruisers tending towards racers if you go for a bigger more powerful rig. For me this is one of the best ways of achieving a good fin keel construction.

Big problem of that approach is that a grounding may cause a delamination between the frame and the GRP hull. Typically galvanized steel has a poor bonding with GRP.
Not saying it's a bad solution but it has it's issues as well.

 

[pmagowan]

The gougon (sp) brothers of West System epoxy fame seem to recommend a bolt on keel where the bolt holes are oversized and filled with epoxy which then spreads the force along all the contact of the bolt with the hull layup as well as having the nut and washer. They did trials to show bonding strength.

Another question, which is best; transporting a hull with or without a keel attached? I was thinking of using coppercoat and it would be ideal to attach the keel during the build so that all the painting layers could be achieved without the normal problem of supports in the way. Obviously if you have to bolt on the keel at the waterside there will then be a join between the hull and keel which will not have the same antifouling layup. I would also be interested in the cost of transporting as my current site for construction is about 50 miles from a major port.

 

[Deleted member 36384]

.... I would also be interested in the cost of transporting as my current site for construction is about 50 miles from a major port.

£500 + VAT to move my 41' yacht 74 miles at the end of June, plus £325 inc VAT for the crane at one end.

 

[pmagowan]

£500 + VAT to move my 41' yacht 74 miles at the end of June, plus £325 inc VAT for the crane at one end.

Wow, that is reassuring. I was thinking in the thousands. I do have a potential spot next to the sea for construction but without a workshop so it would significantly delay things. If it is a reasonable cost for transport then i am home in a boat, so to speak!

Did yours have the keel on and if so did height pose any issues? It would be nicer to put the keel on before hitting the coast as then it would be a bit of a rush with the crane. It is always much nicer to have no pressure to make sure you get things done right.

 

[Deleted member 36384]

Yes, the keel is on, no problems with height and a couple of hairpins to negotiate. The Rival's keel is encapsulated and she draws 1.8m plus about another 1.8 for the topsides, plus granny bars sticking above the coachroof, max, 11' beam, 10000 kg. At that size she requires an escort van which is included in the price, mast is about 15m long and is stored down the side of the transporter within the length of the low bed semi trailer.

 

[KellysEye]

Encapsulated and filled with lead ingots, you can hit anything and it won't damage it. We had one and the ingots were held in place by tar.