Swing Keel on a Cruising Boat

[Leither]

Originally Posted by Jim H

I once looked at a Pearson 35:


It obviously has a centerboard, but it wouldn't be a boat to beach to dry out (unless you careened it).

I think your Mogan 30 is similar:


I also thought about a Tartan 37 with centerboard, but I noticed in the story of Tigger, a Tartan 37 that circumnavigated, that the owners simply glassed the centerboard up into the raised postion at one point because it caused more problems than it solved. Some have systems that fail, and others rattle quite a bit, etc.

By comparison, this is what parking an Ovni or Southerly might look like:




Hopefully, a newer boat like the Southerly or Ovni wouldn't have problems for awhile. Good luck with the Morgan-- she's a classic.

Thanks for the Morgan layout drawing - that's something I don't have in my collection! And thanks, too, for your comments about the Morgan. She is a beauty and great fun to sail.

I understand your point about the beaching problem (the picture of the Ovni ia amazing) and about maintenance issues on the centreboard. I suspect that this problem is like almost anything else boat related - as long as you carry out regular inspections and adequate maintenance then you are OK. Otherwise, trouble is bound to catch up with you eventually....

Incidentally, twin keeled boats which sit level on the hard are very common in the UK where East Coast harbours tend to dry out at low tide. I had a 23' sloop with this feature and it was very handy. If we needed to replace a seacock, for example, then any convenient sandy beach would do - choose your tide state, run her aground and wait for the tide to go out......

Stuart

[OsmundL]

May I make some observations as an actual owner of an Ovni 395, going on 3 yrs now? It has been a gorgeous ship that I sail singlehanded, last summer north of the Polar Circle. There seems to be a lot of theory and little first-hand knowledge floating around.
First, the centreboard: on the 395 and smaller models there are no hydraulics, only a rope easily pulled by hand to raise it. The keel swings back, so I have scraped bottom a few times without the slighest damage to it. The rudder does have a manual hydraulic lift, but it is secured with a tiny brass seal that punctures if the rudder is hit. Easily the cheapest spare I have met on a boat: €1 for a replacement to screw into place on the spot. I bought 40 of them, that should cover the next few years’ of bad maneuvering ☺

To the never-ending saga of Ovnis and “capsizing” formulas: I actually found one calculated at In-Depth Discussion of Aluminum Boat Design & Selection, Part I|Offshore Sailboat Voyaging|Attainable Adventure Cruising
The short answer is: In 30 years, nobody has reported a capsized Ovni, and they are possibly the most consistently cruised boats in circulation. I believe some reasons lie in this: my boat has only 80kg of ballast in its “keel” but many tons of lead in the actual hull. For a start, that means it would survive a loss of keel without noticeable loss of balance. It has capsizing characteristics closer to motor boats such as the sea rescue launches, reknowned for their ability to do a “cano roll.” Add to this a lesser danger when broaching, as you can “surf” this boat with the centreboard up and thus avoid the capsizing momentum of a deep keel boat.

Finally, corrosion: By all means take it seriously, but can we please not explain matters as if there is an untreated bare aluminum hull lying in the water? That is equivalent to explaining the flaws of a fibreglass yacht as if it were built in ply sandwich without a gelcoat. The Ovni is coated inside and out with a pretty hard surface. The easily most exposed anodes are by the propeller and rudder, as on all boats. The anodes on my hull are so far barely attacked. Without “dumping” on other materials I have to say the most satisfying feeling is to look in the incredibly clean dry bilge after three years. This boat stays dry! In November this year at sub-zero temperatures I lived in it and had brought a de-humidifier for comfort’s sake. To my surprise the hygrometer soon dropped to 40% and I stopped bothering with the de-humidifier.

There are many reasons why we prefer one boat or another. I just want to make the point that very few long-distance sailors would call Ovni a “risk” – to the contrary, this is a blue water thoroughbred.

[tweitz]

My Beneteau 323 has a lifting keel and I know it was an option on several Benteaus. Like all boat decisions, it is a compromise, but my compromise lets me bring the boat into my dock, a pretty damn important consideration. I have found, after 3 seasons, that it makes absolutely no noise, the boat tracks superbly, even with the keel up (probably hleped by winglets on the keel stub), there is little leeway even with the keel up, and the only interior compromise is that the dining table is on the centerline. I am delighted with it. I would guess the boat is a tiny bit more tender, but can't tell for sure. Of course if you want an almost ideal boat, and money is no object, a Hinckley Bermuda 40 also has a centerboard.

[OsmundL]

Originally Posted by sailingdog

The big problem with the Ovnis is that Aluminum is pretty low on the anodic scale and a small electrical problem can cause major damage. There was an aluminum boat down in Rhode Island that went from being in good shape to having to be total lossed over the course of one season due to bad stray current problems in the marina it was at.

Sailingdog, how much more evidence do you have? One anecdote about one unidentified aluminium boat (how many amateurs have not tried their hands at a self-build in metal?) hardly justifies a bombastic "The big problem with Ovni" as you put it. I have tried to find people with Ovnis who can confirm a "big problem" but so far without success - and I have spent a couple of years in their clubs and forums.

If I may be so bold: one advantage of the (hypothetical) "Ovni problem" is that it would occur in harbour and hopefully be spotted there. Rather more scary to me is the equally real - and statistically far more common - problem of a keel boat losing its keel or springing a leak on the high seas.

[noelex77]

Originally Posted by OsmundL

Finally, corrosion: By all means take it seriously, but can we please not explain matters as if there is an untreated bare aluminum hull lying in the water? That is equivalent to explaining the flaws of a fibreglass yacht as if it were built in ply sandwich without a gelcoat. The Ovni is coated inside and out with a pretty hard surface. .

The ouside of the Ovni hull is just bare untreated alumium. There is no hardcoat added.(The topsides are painted for asthetics and to reduce heat absorption. The underside is antifouled). The inside of most other aluminium yachts is also bare untreated alumium. (The ovni is usally painted arround the bilge)This is fine. Marine grade Aluminium is almost immune to saltwater attack, better than fiberglass which even with a gelcoat absorbs water and looses strength.
I pointed this out because many people believe aluminium corrodes in seawater. It can be attacked if electrically attached to other metals or has electrical current running through it, but with sensible construction and common sense, as others have pointed out, this is not be a problem.

[sailingdog]

Osmund-

The problem with aluminum boats is generally only a risk in marinas... since a single boat with a grounding problem can damage the hull beyond repair rather quickly. It doesn't apply just to Ovnis, but to all aluminum hulled boats. Ovnis, being solid bluewater cruising boats, probably spend less of their time in marinas than coastal cruisers would...and as such probably don't see the issues as often... since it is specifically limited to marinas. There are a fair number of cases cited in the Boat US book Seaworthy IIRC... which is well worth reading in any case.

[noelex77]

Originally Posted by sailingdog

Osmund-

The problem with aluminum boats is generally only a risk in marinas... since a single boat with a grounding problem can damage the hull beyond repair rather quickly. It doesn't apply just to Ovnis, but to all aluminum hulled boats. Ovnis, being solid bluewater cruising boats, probably spend less of their time in marinas than coastal cruisers would...and as such probably don't see the issues as often... since it is specifically limited to marinas. There are a fair number of cases cited in the Boat US book Seaworthy IIRC... which is well worth reading in any case.

Thank for the note about the book I will look out for it. Most problems in marinas come from incorrectly wiring shore power on the aluminium boat. Unless the ground wire is isolated a metal boat can suffer very rapid corrosion. There are simple ways around this, but every once in a while someone will add a battery charger incorrectly to an aluminium boat and create a major problem. This is the stuff that creates horror stories about aluminium boats, but the cause is just ignorance or stupidity.
Stray current in the water from a nearby steel boat or an unusually "hot" marina can produce a small amount of corrosion but usually the zincs will provide complete protection.
These problems are rare and seen less than , fiberglass boats with core or hull deck joining difficulties,

[OsmundL]

Originally Posted by noelex77

The ouside of the Ovni hull is just bare untreated alumium. There is no hardcoat added.(The topsides are painted for asthetics and to reduce heat absorption. The underside is antifouled). The inside of most other aluminium yachts is also bare untreated alumium. (The ovni is usally painted arround the bilge)This is fine. Marine grade Aluminium is almost immune to saltwater attack, better than fiberglass which even with a gelcoat absorbs water and looses strength.
I pointed this out because many people believe aluminium corrodes in seawater. It can be attacked if electrically attached to other metals or has electrical current running through it, but with sensible construction and common sense, as others have pointed out, this is not be a problem.

Noelex77, the outside of the Ovni hull is just bare untreated aluminium *above* the waterline; this is because the corrosion risk is zero there. As you point out, the issue is "electrolysis" and not "rust" as some confuse it with. Aluminium in the air does not deteriorate, which is why most of us have masts and spars in the material, and jumbo jets overhead don't drop on our heads.
Below the waterline but equally important on every inch of surface inside the boat, Ovni is coated. Bilge, sides, top, the lot.

*Under* the waterline the Ovni is coated under the antifouling. Here too is a point: if a scratch should result in bare paint on a point, that is where all electrolysis would concentrate, ultimately sinking the boat. But again, it would sink before the remainder of the hull is damaged, so even though an Ovni sunk in a marina (which I never heard of) would be water damaged, the hull would remain intact and rescued.
The very first boat built in aluminium did indeed dissolve, and quite some thereafter. This is because proper *marine grade* aluminium is a relatively recent phenomenon, basically post-1960s on leisure craft. If the problem had been so severe, it is doubtful that such a high proportion of the world's rescue craft, military craft below 50', fishing fleets and pilot ships would be built in aluminium. A long-term study by the US Navy recorded these craft to have a longer service life than all other materials.
As you say, Noelex77, it comes back to common sense and maintenance - which by the way is less than on a fibreglass boat and less onerous than on a steel boat.

[sailingdog]

Unfortunately, there's plenty of both Ignorance and Stupidity to go around... finding somewhere it is in low supply is the tough part.

Originally Posted by noelex77

Thank for the note about the book I will look out for it. Most problems in marinas come from incorrectly wiring shore power on the aluminium boat. Unless the ground wire is isolated a metal boat can suffer very rapid corrosion. There are simple ways around this, but every once in a while someone will add a battery charger incorrectly to an aluminium boat and create a major problem. This is the stuff that creates horror stories about aluminium boats, but the cause is just ignorance or stupidity.
Stray current in the water from a nearby steel boat or an unusually "hot" marina can produce a small amount of corrosion but usually the zincs will provide complete protection.
These problems are rare and seen less than , fiberglass boats with core or hull deck joining difficulties,

[noelex77]

Originally Posted by OsmundL

Noelex77, the outside of the Ovni hull is just bare untreated aluminium *above* the waterline; this is because the corrosion risk is zero there.

*Under* the waterline the Ovni is coated under the antifouling. Here too is a point: if a scratch should result in bare paint on a point, that is where all electrolysis would concentrate, ultimately sinking the boat..

I hope this doesn't get too boring for others, but I believe a good understanding of aluminium corrosion is helpful to us owners of aluminium boats. Its a bit off topic, but as I stated before I think the Ovni is best choice for a swing keel yacht so perhaps even as esoteric discussion of electrolysis is relevant.

The corrosion risk above the waterline is not zero. If any stainless steel fitting is not isolated properly you will get electrolysis even above the waterline. Fortunately this is very localized the formed aluminium oxide tends to isolate the fitting reasonably quickly, but it is worth looking out for and re isolating any fittings that are showing signs of problems.
I may be wrong but I think you are misunderstanding the purpose of the paint underneath the antifouling below the waterline. Its main purpose is to simply isolate the metallic antifouling from the hull just as you would isolate any metal fitting. If its scratched to bare aluminium you can get some localised problems as you state, but remember you will have other areas of bare aluminium such as the rudderstock and corrosion is not a major problem. If the whole bottom was unpainted there would be no problems. Aluminium does not need to be isolated from seawater. Indeed many trailerable aluminium boats in Australia have unpainted aluminium bottoms. Some of these use very thin aluminium and work boats get used daily with no corrosion.
If they ever perfect sonic antifouling (I very much doubt it) you will be able to leave the bare aluminium your Ovni unpainted below the waterline as well.

Aluminium corrosion is a complex issue and even the experts arugue, so I am happy to be corrected on any of the above points.
For owners contemplating buying an aluminium boat don't worry structural problems in aluminium boats are less than in fiberglass construction.