Last Updated on 05 August 2016 by
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Sections of the ketch Presto by Commodore Munro (1885)
The Presto design was developed by Commodore Munroe in the 1880s on the US Atlantic Coast. The boats sailed up and down the coast some distance offshore and were confronted by the frontal weather systems and the influence of the Gulf Stream found in that part of the world.
The first time I came across the lines of the Presto was when an old friend pulled out a dusty set of large wooden moulds he had once built from lines lofted on the floor of his shed. I was immediately intrigued by the flare in the sides and the flat bottom. Sadly, the project never progressed further and some years later he passed away.
When I saw the lines above at the time of my first visit to New Zealand, I was fascinated. It is one of the few hulls I have ever seen that was so obviously designed by a highly experienced seaman for seamen. Nothing else came in the way. All the design decisions made come together consistently, there is not a hint of design trends, beliefs or conformism perspiring through.
It was a revolutionary design in 1885 and it took over 80 years before yacht hull design as a discipline started just edging closer to it, increasing beam and reducing hull depth. It took another 20 years almost until we saw broader aft sections appearing on displacement vessels, finally letting go senseless shapes and beliefs that had originated from Scandinavian lifeboats.
Today, one should check the fore-and-aft volume distribution achieved and – if needed – correct it based on what we have since learned about hull hydrodynamics and wave-making resistance, but the general shape of the sections is still just as perfect for the displacement achieved. It demonstrates an outstanding grasp of stability and hull shape versus seakeeping characteristics. I never imported the Presto lines into 3D CAD – no doubt many others have; it would be quite interesting to see what comes out.
There are a few modern and “damaged” versions of the Presto hull around, a case of name-recycling for marketing purposes. They seem to have a different waterline beam-to-hull depth ratio, a different relative displacement and they are just different boats.
I’m confused, are you saying you saw munros presto lines in nz or are you talking about the early nz boats?
Guy,
Yes, I am saying I saw frames for Munro’s Presto design in New Zealand. The boat was not built and I am not aware of any true Presto ever built in New Zealand.
Best regards,
Eric
Hi Eric
I am interested to know where you saw the frames for Munro’s Presto Design (just out of curiosity)
I am reminded of a conversation I had with Jack Cropp about hull design and efficiency…he had a reputation for designing fast sailing and fishing boats.
I recently saw a newly built traditional East Coast (of the USA) fishing boat and was struck by its width aft…it reminded me of the Volvo 70’s being used today…I understand that these fishing boats were also (like the Presto) designed to be seaworthy (enough to fish off the coast without motor)
I lack the technical expertise to make a full assessment of these boats…do you have any knowledge of them?
Greetings,
New Zealand Sailor
Roger,
I discovered them in Otatara near Invercargill in 1999. They were in an old shed. Some years later the property was sold and the frames stayed behind. They may still be there today.
Narrow and pinched stern lines were always a mistake, they gave boats that were unable to accelerate in following seas and became unmanageable as waves caught up with them. I never specifically heard about the fishing boats you are referring to, but they may well be related to the Presto hulls. I would expect so due to the geographic location.
I am particularly uninterested in traditional designs in general due to them so often being hydrodynamically senseless, based on misconceptions and ultimately unseaworthy when you take them to the limit (you just can’t sail them any more), but the strength of materials and construction methods constrained what could actually be achieved for a long time. The evolution in design hasn’t just been one based on new ideas and understanding.
In this context, those boats from the US East Coast are quite remarkable, because their design was excellent from a seakeeping point of view at the displacement that was imposed by their traditional construction and they could be built strongly enough. They weren’t designed according to beliefs like almost everything else that went on for almost 100 years on both sides of the Atlantic.
You may remember that when Francis Chichester commissioned the design of Gipsy Moth VI to sail around the world, the brief he gave to the design office represented what would have been an early Open Class racing yacht: “I asked for a scow-shaped hull, that is to say of broad beam, shallow draught, and flattish bottom, with a deep keel”. Such a hull would have been very stable and powerful and most interesting. He was told that he was wrong and the boat he got instead was narrow, deep and also basically a heap of garbage. What a missed opportunity…
I sometimes work on designs with fishermen and commercial operators. It is essential to listen to the people who go and spend time at sea and work the boats. They have interesting things to say. What they believe and the conclusions they draw are one thing, but their raw experience is something that can’t be touched. Looking at the Presto boats, some people clearly had an outstanding grasp of both stability and dynamic seakeeping. These people not only understood marine design and construction, but they also spent plenty of time at sea in bad conditions or they wouldn’t have come up with these hulls.
Kind regards,
Eric
Read “The Commodore’s Story”, Ralph Munroe & Vince Gilpin, for first-hand accounts of the Presto class abilities. Available online at the Wayback Machine book repository at archive.org
Richard,
Thank you for sharing this, it looks exceedingly interesting! I followed your suggestion and found a PDF scan of the book at the following link: https://ia802500.us.archive.org/19/items/commodoresstory00munr/commodoresstory00munr.pdf
Not sure how permanent this will be, but it saves searching the archive if it works.
Kind regards,
Eric
I have a Presto 36, built in glass, in 1992, by Perfection Industries of Ft. Lauderdale, Florida.
Hello Nelms,
There have been quite a few boat designs “inspired” by the original Presto, the lines of which are in the public domain today. People appear to have altered the original lines for some reasons, so technically they are not Presto boats any more. Our knowledge of hull hydrodynamics has significantly increased in the past 50 years; there may be somewhat compelling reasons to “optimise” the hull shape. As I have never drawn the original Presto lines in CAD to analyse them, I can’t specifically comment in this direction. Any such changes prompted by hydrodynamic optimisation would target the longitudinal distribution of the volume as this is what determines the position of the centre of buoyancy (LCB) and the prismatic coefficient (Cp). These are the primary figures of importance for hydrodynamic performance. Changes to the shape of the main cross-section should be called arbitrary in comparison, they would impact the stability and essentially depart from the essence of the original design.
The other aspects that changed over time are materials and construction methods. A hull built today would almost invariably be lighter than the original and allow a higher ballast ratio / lower centre of gravity. It is good for safety and sail carrying ability, but it can change the motion of the vessel in a seaway. This could be compensated advantageously by using a somewhat taller rig, balancing the added stability with a greater sail area.
A good yacht design is a fine balance between many parameters and it appears to have been achieved in a truly remarkable way at the time by Commodore Munro. Once changes are introduced, the design needs to be rebalanced differently overall and the outcome simply becomes a different boat.
Kind regards,
Eric