Another day, another Dahlgren!

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Cutaway side view from the patent drawing for Dahlgren Shell Guns, 1861

Today’s question seems like a simple one – how long is a Dahlgren Shell Gun? As I mentioned previously, I am designing a set of drilling equipment to clean inside the XI-Inch Dahlgrens recovered from USS Monitor, and as part of that I need to establish parameters for actually using the drilling equipment. Well, one very important parameter to know is how far in can you drill? There are two ways to answer that question: you either need to know exactly how deep the bore is before you begin, or you keep pushing the drill into the gun until it hits metal. Given that the latter option cuts a shiny new groove into the back of the bore, I like to aim for the former.

Fortunately, guns from the 19th century often have government ordnance records or patent drawings which give more or less complete dimensions, and Dahlgren shell guns in particular have both patent drawings and multiple Board of Ordnance drawings which survive. Unfortunately, they don’t all match. The patent drawing gives a standard ratio for all Dahlgren shell guns that the bore should be 12 calibers in length, meaning an XI-Inch gun should have a bore 132” in length. The Board of Ordnance drawings give a bore length of 131.2” for an XI-Inch Dahlgren, or approximately 11.93 calibers. In addition, we have both Board of Ordnance pattern drawings and inspection drawings, and while the bore lengths are the same between them, the powder chambers have different measurements.   Read more

Dahlgren plans, and a new face in the tank farm!

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A view down the bore: although the front section is largely clean, patches of concretion several inches thick remain on most of the interior surface, beyond the reach of hand tools.

Hello everyone! After a sneak-preview of my existence in the most recent blog, I’m writing this post to introduce myself as the newest addition to the USS Monitor team. My name is Erik Farrell, and I joined as an Archaeological Conservator at the beginning of July. I previously worked as an archaeological conservator for the NC Department of Natural and Cultural Resources, conserving materials from the wreck of Queen Anne’s Revenge with a focus on artillery and other ordnance. Before that I interned at Bevaringscenter Fyn in Denmark, working on a variety of objects including archaeological arms and armor components. I have a great love and affection for historic weapons (and historic artillery in particular), so I’ll give you two guesses what I’m most looking forward to… Dahlgrens!

A lot of work has gone into the conservation of Monitor‘s two XI-inch Dahlgren guns and their carriages already over the years. These are big, complex objects though, and there is still a great deal of work to be done. Marine archaeological guns always have one big problem in particular – how do you clean the inside?   Read more