Best way to attach a keel

[pmagowan]

That's interesting - how do you attach a block or a cleat with epoxy? Obviously lighter stuff can just be glued on with a runny filler mix, but I'm not sure I'd trust that for an anchor cleat, a halyard turning block, or a block for a jib sheet.

I have seen a design for building shroud chainplates from epoxy and kevlar integral with the hull, but it was pure speculation, hadn't yet been done at the time.

Pete

Have a look at the Gougeon Brothers West System book (it is free online). They did loads of tests on this and the epoxy comes out stronger than mechanical fittings. For some bits you can use both and drill and fill with epoxy essentially making the fitting integral with the deck. The deck fitting can also be made integral rather than bolted on. There is no reason not to have a wood/epoxy/fibre cleat. The fixing only has to be as strong as the substrate.

 

[doug748]

First thing, long term problems are not inevitable with bolt on keels - typical sweeping statement that ignores all the other variables.....

No, all these problems are not inevitable, nor did I say they were. You can normally perm one, or more, from a long list.
There is one drawback that always remains, the nagging doubt about the history and probity of keel bolts in a secondhand hull.

 

[pmagowan]

No, all these problems are not inevitable, nor did I say they were. You can normally perm one, or more, from a long list.
There is one drawback that always remains, the nagging doubt about the history and probity of keel bolts in a secondhand hull.

You could xray them.

 

[lw395]

No, all these problems are not inevitable, nor did I say they were. You can normally perm one, or more, from a long list.
There is one drawback that always remains, the nagging doubt about the history and probity of keel bolts in a secondhand hull.

It's not the bolts that worry me TBH.
It's those little fibres in the whole structure between the keel and the rig.
Weakest link and all that...
How do you evaluate the history of a hull laminate?

 

[doug748]

You could xray them.

I think X ray photographs produced usable results in wooden boats, where they were mainly looking for waisted bolts in the deadwood. The principle is said to be simple: expose an isotope on one side of the hull and hang a plate on the other.
If you could reliably, and cheaply, do it, It might be an excellent business to be in. I guess it would struggle to tell you the condition of the threaded section within the keel or to detect cracks at the interface.
Of course with your project you are in a position to over engineer it and a lead keel bedded and bolted onto a stout stub ought to make it into the next millennium. Provided, as iw395 has pointed out, the rest of the structure is up to it

 

[30boat]

It's not the bolts that worry me TBH.
It's those little fibres in the whole structure between the keel and the rig.
Weakest link and all that...
How do you evaluate the history of a hull laminate?

The majority of boats are second hand and you don't see the keels or laminates fail.

 

[geem]

There is an ex charter boat lifted out in Antigua next to me. It's a Bavaria 42 with what looks like a bolt on lead keel. The boat as obviously had a knock with something very solid. The keel had a large dent about 2 inch deep in the front of the keel. It looks like it has deformed and absorbed some of the impact. There is also a clear gap at the front of the keel where it meets the hull. This boat could be expertly repaired or bodged. How would a new owner know the difference? Have the keel bolts been stressed? Looking at the damaged to the keel I would guess yes. Will the keel bolts be replaced as a precaution? What do you think?

 

[Robin]

I tend to agree.
There are hundreds of perfectly adequate designs covering the spectrum.
So unless you are pushing the boundaries, or genuinely have requirements that are not addressed by previous designs, what is the up-side?
First prototypes of new designs often get significantly modified as a result of early experience.

I design stuff for a living, electronics not boats, but I suspect the 'right first time' mantra is equally unlikely to go well in boats.
We take many man-years of experience, do a lot of simulation, design things fairly rigorously, etc etc, but most designs go through a prototype phase and at least one major revision before being good enough to sell.
A yacht is a pretty complex system, with many inter-acting systems.
I think it might be like my German friend said about houses, you need to build at least three, the first one you will sell to your enemy, the second one you can sell to a friend, the third one will be OK!

Indeed I believe Andrew Simpson's was one of three such and I'm pretty sure his was not the first one built.

 

[Tranona]

That's not really "glued on" though. All the strength in that arrangement comes from the flange on the GRP stub, sitting inside the hull.

The original question was about attaching a keel, not about the structure than takes its loads - hence the mention of Andrew's method. He specifically wanted to avoid mechanical fastenings going through the hull (which is wood epoxy as the OP proposes) to avoid the possibility of water getting into the composite structure.

 

[Tranona]

It's not the bolts that worry me TBH.
It's those little fibres in the whole structure between the keel and the rig.
Weakest link and all that...
How do you evaluate the history of a hull laminate?

Exactly as the Cheeki Rafiki incident shows. bolts are rarely a problem on their own as the safety margin is huge (although where they are positioned can be). If there is a problem it is with the underlying structure and it has always been a "problem" dating from the first time ballast was bolted to the outside of hulls. Hence the attraction in the early days of GRP to moulding in ballast. Not surprising as most of the designers and builders had experience of the problems with wood construction. However, as I pointed out earlier once hull and keel shapes changed - partly because of the possibilities available with the new material it became less attractive and eventually just about disappeared. It is still attractive if you want to build a boat of the older type shape - but few people do.

 

[pmagowan]

The original question was about attaching a keel, not about the structure than takes its loads - hence the mention of Andrew's method. He specifically wanted to avoid mechanical fastenings going through the hull (which is wood epoxy as the OP proposes) to avoid the possibility of water getting into the composite structure.

A way to prevent that with bolts is to drill and fill an oversized hole with epoxy and then re drill for the bolts or, as recommended by the Gougeon brothers, drill an oversized hole and glue the bolts in with epoxy so that the forces are spread over the whole bolt and surrounding structure. Either would maintain the encapsulated wooden composition.

 

[Tranona]

A way to prevent that with bolts is to drill and fill an oversized hole with epoxy and then re drill for the bolts or, as recommended by the Gougeon brothers, drill an oversized hole and glue the bolts in with epoxy so that the forces are spread over the whole bolt and surrounding structure. Either would maintain the encapsulated wooden composition.

There are always potential ways of trying to resolve a problem. However, once you have looked at a few composite boats - even those built by reputable builders there always seems to be vulnerable points that might take a few years to show themselves. There is also an issue of the amount of time required to do all the nice things you are talking about that makes such boats so expensive to build commercially.

You might get the PBO back numbers (about 10 years ago) where Andrew describes building his boats, as although his style of boat might not appeal he has a very pragmatic approach that utilises the techniques well without trying to make the boat look like a piece of furniture. This to my mind is where many boats using wood/epoxy fall down in excessive use of bright finishes and decorative woodwork. Great when they are new, but still need a lot of upkeep and can look terrible if neglected. Andrew has been cruising his boat non stop since he built it and is now across the pond.

 

[westhinder]

The OP may be interested in this article from the GT Yachts website:
http://www.gtyachts.com/files/Keels_Why_Compromise_GTYachts_Jan2015.pdf
And just to forestall any dispute on the merits of a design of which barely one yacht has been built: it looks exactly the same design as on the Starlights. Starlights and GT were both designed by Stephen Jones, so that may not come as a surprise.

 

[pmagowan]

The OP may be interested in this article from the GT Yachts website:
http://www.gtyachts.com/files/Keels_Why_Compromise_GTYachts_Jan2015.pdf
And just to forestall any dispute on the merits of a design of which barely one yacht has been built: it looks exactly the same design as on the Starlights. Starlights and GT were both designed by Stephen Jones, so that may not come as a surprise.

Thanks, I had already read that article but, as with all these things, a second read is worthwhile. Their technique is interesting.