What can we do about the environment in the cellar?

As I said before, the cellar in which Peggy sits is very wet. In fact 'a river runs through it', quite literally - though perhaps 'stream' would be a better description. Our first thought was to see whether we could regulate this environment. This would mean sealing the walls, floor and ceiling of the cellar against water from the stream and tidal flooding. It could only be acheived by 'tanking' the cellar, i.e. rendering the walls and floor with cement, rather like a swimming pool.
There are several problems with this plan. We cannot afford to cover or damage the walls and floor because they are of archaeological importance in their own right. We would also have to seal the ceiling and it's not clear how we could do that. The room would end up too small for the boat (!), and it's very unclear how the public would access the space. And finally, a structural engineer advised that the tidal pressure is so high in Castletown that it would be difficult to achor the 'tank' to the rock sufficiently strongly to safeguard the historic building above it!
This leaves us with two alternatives. Leave the boat where it is and do nothing, or remove it to a safe, controlled environment, off-site. We have agreed the latter.
We are fully aware of the radical impact this will have on the boat and building. Separating them is a grave step. So we plan to re-unite them somehow, in due course. Meanwhile we will take the opportunity to study and record the boat cellar, winding gear, boat, masts and spars. We will ensure that the public can see more, not less, of Peggy while we work. And we will take gradual and measured steps to stabilise and conserve Peggy herself.
In my next post I'll describe how we intend to move Peggy.

Our strategy

In my last post I introduced some of the work we have done that'll help us decide what action to take. The first priority is to make sure that Peggy is properly supported so that she can't hog or sag (see below if you can't remember what these mean). MNH commissioned local firm BB Consulting Engineers Ltd. (http://www.bbconsulting.co.im/) to design a new support cradle based upon profiles taken from the laser survey described below. The design they have come up with is based upon a load-bearing spine with ribs. The construction will be in galvanised steel, and is more elegant and less visually intrusive than the current arrangement. Here is an impression of it:


General scheme of the proposed new support cradle

 The space between the ribs and the hull will be cushioned with inert, polythene foam. Polyformes Ltd. of Leighton Buzzard (www.polyformes.co.uk) are supplying the foam, cut precisely to the profiles and dimensions taken from the laser survey. The cradle is being fabricated right now by Galla's Foundry here in Douglas.
We'll have to lift the boat to insert the new cradle. Unfortunately, this will not be easy! This is because 1. the cellar is very cramped: at its lowest level the ceiling is only 20 cm above the boat, and there is less than one metre between the boat and the walls; 2. we can't put pressure on the hull because its too fragile, and 3. we can't lift (e.g. with jacks) from under the keel because we want to sit the boat back down on the beam, illustrated above. We do have one thing in our favour however, which is that Peggy's keel is not the original one. In fact the current keel dates from 1950. Because of this we were able to secure the permission of the Trustees of Manx National Heritage to modify it by drilling three holes through it. We'll put bars through the holes and lift the boat using the bars. We are going to contract a specialist firm to undertake the lift using computer-controlled hydraulic jacks. The work is currently scheduled for May/ June this year, so watch this space for news in due course...

Making decisions

Deciding what to do with such an important object is challenging in many ways. We have to test our ideas and prejudices by asking for advice and analysing data. Peggy is loved and admired by many, not only on the Isle of Man but also further afield, and it's very important that we proceed carefully and rationally when we make decisions.
National Historic Ships UK have been very helpful to us in finding ways forward. They made a special case for Peggy to be included on the NHS Register in spite of her location (the Isle of Man is not part of the United Kingdom) and size (she's too small to be a 'ship'). The statement of significance for Peggy that they published on their website has been very useful. And they have helped us find professional consultants when that has proved necessary.

One example of this was our invitation to Eura Conservation Ltd. of Telford (http://www.eura.co.uk/) to survey Peggy in 2010. Their report is a very valuable addition to our knowledge of the boat. They showed in detail what a monument she is to long-lost boat building techniques, and gave us a clear insight into her structure and weaknesses.



Peggy's frames (image curtesy of Eura Conservation Ltd.)



Their report re-affirmed Peggy's importance through a number of features not properly recognised before. There'll be many more of these as we begin to study her in greater detail.



One of the great mysteries is how and in what colours Peggy was painted. The quantity of original paint left on her is absolutely unique for a vessel of her age (and there are very few of those), but it's completely covered by the paint applied in 1950. The appearance of the original paint was not recorded. It's possible that we may one day see those early colours once again, but first we must get an idea of what is there and how extensive it is. We commissioned Crick Smith Conservation (http://www.cricksmith.co.uk/) to undertake a preliminary survey of small samples removed from the hull. It showed many interesting things, amongst which that the hull was once duck-egg blue...

Paint cross sections from Peggy (image courtesy of Crick Smith/ University of Lincoln)

With these reports and with the environmental data and the analysis of the corroded nails, we feel confident to make a firm case for action...

Hogging and Sagging

As I mentioned in my first post, Peggy has been propped upright on frames since 1950. We don't know exactly what she weighs, though we estimate about 2.5 tonnes.

Last week I introduced some of the ways in which the boat has decayed since she was made, and showed how her fixings (nails) are failing and damaging her. We wanted to be absolutely clear about this so, in 2010 I removed five timber core samples from the hull, each containing an iron nail.

Me removing core samples from Peggy's hull

I sent the samples to Dr David Watkinson of Cardiff University for analysis. David is one of the world's leading experts on marine archaeological iron. His tests showed that in every case there was practically no metallic iron left where the nails should have been, only rust. They also showed high amounts of sea salt (= bad) and advanced mineralisation (acid attack) of the surrounding timber. The failure of her nails puts Peggy's timbers under strain.

Wooden ships and boats often bend and warp if they develop structural faults or if they are otherwise put under unnatural strain. The commonest of these are termed hogging and sagging.

You might expect Peggy to have sagged because she is not evenly supported all along her hull as she would have been when she was afloat. In fact you can see that she has if you look at the distorted shape of the timbers adjacent to the 1950 props.

Hogging refers to bending of the keel. Its not easy to assess this in the tight space of the boat cellar. However in 2012 we commissioned a 3D laser survey of Peggy's hull, with the generous assistance of National Historic Ships UK (see links to the right of this post). You can clearly see the keel is slightly bent, a little like a 'hog's back'.



A preliminary scan image of Peggy showing hogging. The colours represent separate patches of data.



Next time I'll discuss how we came to decide what needed to be done to preserve Peggy.

Humidity

Peggy's boat cellar is prone to tidal flooding. It also has a freshwater stream running through it. Since 2009 we have been recording the temperature and relative humidity (RH, in %) of the air in the cellar. There are plenty of resources on the www that neatly explain what RH is, but for the purposes of this blog its only necessary to know that it's RH that influences whether objects get damp or dry out.
Above 60% RH wooden objects are subject to increased risk of attack from fungi such as 'rot', and the risk grows as the RH rises. Wood-boring insects such as furniture beetle (woodworm) also like damp. In fact just about every natural decay process you can think of is helped along by high RH.
Iron, as we all know, rusts quickly when it is wet, and the wetter it gets, the faster it rusts. It'll keep on corroding until there is no metal left at all. If the iron is salty the corrosion will be more rapid and serious. The rate at which iron rusts is directly related to RH: the lower the RH the slower the corrosion. The only way to stop iron from rusting is to lower the RH of the surrounding atmosphere. In the case of iron contaminated with sea salt, one would have to lower the RH to levels similar to those you'd find in a desert to stop it rusting. This is quite a challenge! Very dry environments are not, unfortunately, very good for wooden objects.
The RH in the boat cellar is consistently 85-99%. This isn't good, obviously. Incidentally, we are interested to know why some of the grosser forms of fungal attack such as dry and wet rot are not more prevalent in the boat and building; we suspect the low temperature (8-12 degrees C throughout the year) may be a factor, but it's a question for future research. Aside from the kind of decay you can see and easily recognise however there remains the problem of more insidious decay we can't so easily see, and above all that of iron corrosion.

As the nails holding Peggy together rust they leach acid into the timber, weakening and destroying it. The evidence for this is all over the boat in the form of brown stains and circles. The boat would theoretically, eventually collapse, though this is not imminent. Some of the fixings are failing, nonetheless.

What is this blog about?

Peggy is a Manx yacht. In fact, at two hundred and twenty two years she is one of the oldest yachts in the world. We know a lot about her because, remarkably, she is still in the cellar of the boat house built for her in Castletown, Isle of Man, in the late 18th century by her owner, George Quayle. George was a notable character on the island and in his early years, something of a rake. His correspondence is preserved in the Manx National Archive, and in it he describes the building of the boat and boat house, and his adventures at sea aboard the Peggy.
Peggy is astonishingly well-preserved and remains substantially unaltered since Quayle's day. The list of her unique attributes is long and quite incredible. If you would like to know more about this and her historical significance, a good place to start is with her entry on the UK National Historic Ships Register (http://www.nationalhistoricships.org.uk/register/1125/peggy). She also has an entry on Wikipedia (http://en.wikipedia.org/wiki/Peggy_of_Castletown).

Since the late 1930's Peggy has been owned and looked after by the Manx Government. The heritage agency on the island is Manx National Heritage, which has maintained the boat house with Peggy in it as a visitor attraction for over sixty years. When the Nautical Museum, as it came to be called, was set up Peggy was righted (she had been lying on her side for 150 years). A small number of her strakes (hull timbers) were replaced, along with her keel and rudder. She was then painted. This is how she remains.

In George Quayle's lifetime, the boat house opened on to a tidal dock surrounded by a curtain wall (the wall remains but the dock was filled in during the 19th century). In the wall were a pair of gates, the remains of which can still be seen today from the quay on the opposite side of the water. These gave Peggy access to the harbour. Windlasses (winding drums that also survive) were used to haul Peggy out of the dock and into the cellar. Peggy was never intended to be far from the water, and accordingly the cellar in which she sits is very wet. Because of this, and notwithstanding her remarkable state of preservation, Peggy has suffered many of the indignities of ageing common to other wet 200 year old objects made of timber and iron nails. I'll use subsequent posts to described a few of these and their effects on the boat.