Whaler try works “duck pen”

[Srodbro]

I’m working on a couple of model whale ships and have a question about the construction of the Try-works. 
I have read that the furnace below the pots enclosed by the brick masonry was separated from the ships structure by a water-filled “duck pen”. Wiki says “A reservoir of water under the bricks keeps the furnace from scorching the wood of the deck. I’m having a hard time visualizing how this worked.
 

In these pics from the web, there is clearly a substantial masonry structure supporting the pots and the lid. And while the fire in the furnace might not have had to be a blaze like in a smelter (I think the blubber probably released its oil at relatively low temperatures, like 150°), the trying out process lasted for days, so the ships structure certainly needed protection from the heat. 

Iron pots that big had to weigh several hundred lbs plus the weight of the blubbery contents. The masonry support must also have been complemented by some internal baffles to get the heat all around the pots, and back to the chimney. 
So, where is this layer of protective water?

In the lower pic, I can imagine that the wooden structure below the fellow’s knee could be a water tank. But, if so, how was all that masonry and the weight of the pots supported above it?

[wefalck]

The CHARLES W. MORGAN should have had such structure, so perhaps contacting Mystic Seaport might help?

 

On the other hand, the stoves/baking oven on ordinary warships must have been very busy at times and I don't recall having seen such structure under their bottoms in contemporary drawings. There would be some sort of iron drip-tray around them to prevent the surrounding deck from becoming soiled.

[Srodbro]

Thanks for the reminder. Upon further search of their website, it appears that they have a separate detail drawing of the tryworks construction. I have a set of Morgan plans purchased from them, but the particular detail I’m looking for is not included. I will contact them. 
 

Below is a copy of the section thru the tryworks on those plans. Not much help in describing the relationship between the pots/masonry/deck. However, the lowest course of bricks curiously shows conspicuously large joints between the bricks of that course. Perhaps this is to allow water retention at the bottom?  
 

We will see what the additional detail shows. I’ll update this post then. 

[Srodbro]

Mystery Solved !

 

I obtained from Mystic Seaport Museum a drawing of the try works construction details. Here are a couple ( very rough) sketches that describe the construction shown on the drawings. 
 

 

The bottom course of brick rests on a layer of yellow pine sheathing over the deck. This course has open joints with no mortar between. Several courses with mortar joints lay on top of the base course, and form the floor of the furnace. In several locations, brick piers are built up to where the iron pots can rest on them. I suspect ( but this isn’t clear from the construction drawings) that these piers extend all the way down to the sheathing, penetrating the water course. In the sketch the blue represents the water “ coolant “ that provides additional protection to the deck. Filled at the “duck pen” the water level could be kept high enough there to assure flow thru the bottom course interstices. 
 

The next sketch shows additional detail 

The bricks of the bottom water course are widely spaced athwart ships to provide even more water protection. 
 

This whole try works structure would have been enormously heavy. There is a wooden plank structure with massive iron brackets fastened to the deck on the starboard and port sides of the structure to hold it in place,  but it doesn’t seem there is much to keep it from sliding fore-aft … but apparently the weight was enough. Nonetheless, the working of the ship must have played havoc with the integrity of the joints. 
 

Seeing this construction, I wonder whether the water course was less intended to protect the deck from heat than from fat/grease leaking thru the layers of brick ( due to cracks in the masonry and joints ) from the burning of blubber scraps as fuel and spreading fire to the deck below. 
 

At any rate, the arrangement of this water course and the structure supporting the pots is more clear. 

[jud]

Quote from Srodbro, ( I wonder whether the water course was less intended to protect the deck from heat than from fat/grease leaking thru the layers of brick ( due to cracks in the masonry and joints ) from the burning of blubber scraps as fuel and spreading fire to the deck below ). Suspect this is the correct reason for the water. Used as a barrier to the oil preventing the decks and supporting timbers from becoming soaked in oil and a stinking messy fire hazard later.