Notes from Windward: #62

Construction Phase One - The High Deck

     Perhaps the most structurally demanding part of the entire project is the "High Deck," a structure sixteen feet wide by twelve feet deep which features a cantilever design.

The High Deck comes together

     The "cantilever" part involves the way that the deck extends out beyond the supports on either side. This balances and carries the load better than if the support poles were the full sixteen feet apart.

     The original model of the castle called for a four foot wide balcony from which the defending archers and pikemen could protect the gate. That would have serve the minimum need, but the decision was made to extend the balcony back another eight feet in order to allow the castle defenders to use the high deck as a command center.

     This change offered the additional benefit of bracing the gate wall so that it will remain secure even under the impact of a squad of attackers trying their best to break down the castle gate.

Horizontal 2x10's on 12" centers

     The primary concern in designing the deck was to make very sure that it was strong enough that a dozen heavy fighters could indulge their martial desires hearts without having to fear for the integrity of the structure. Instead of horizontal supports on 24" or 16" centers, we went with 2x10's on 12" centers. That's a lot of wood, but it provides a lot of support.

     Confident that the horizontal supports would be able to withstand the vertical load created by twenty fighters, our attention turned to the horizontal stress that those fighters would create as they moved around on the deck.

     The first way the goal of stability was achieved was by securing four of the horizontal supports to the vertical supports located on each end and at the one-third and two-thirds points.

     The second way the deck was stabilized was by installing a 2x10 "band board" on the outer ends of each set of horizontal supports. The goal here is to prevent the horizontal deck supports from being able to roll over and collapse when subjected to horizontal stress. With heavy screws driven through the band board and into the top and bottom of each horizontal deck support board, that's not likely to happen.

The heavy duty band board

     And just to provide that extra margin of "over kill", the horizontal members were secured yet again with a run of blocks over each of the support beams. Held in place three different ways, I'm confident that the deck supports are not going anywhere.

     The deck itself is made from 2x12 planks. By going with the extra wide planks, instead of the cheaper 2x6's that are usually used, the deck was afforded yet another degree of rigidity.

     Each plank is secured to the horizontal support underneath using two screws especially designed for deck work, and while the screws we're using are not cheap, they're a very good value from the standpoint of holding power. Wood, and especially wood that's outdoors, swells during the rainy season and contracts during the dry season, with the result that regular nails become loose over time.

     One way around that is to use "coated" nails, i.e. nails which have been given a thin coating of hot-melt glue. They're often called "coated sinkers," and the thin coating of glue gives them a golden look.

     As a coated nail is driven into the wood, friction causes the glue to melt and cement the nail in place. While this gets around the problem of the nail coming lose over time, it also has two draw backs. First of all, you need to get the nail where you want it the first time, since you're not going to be able to remove the nail without doing a considerable bit of damage to the board.

     Secondly, it's still a nail with a point which always causes the risk of splitting the board on its way in. Once a split develops, almost all of the nail's holding power is lost. The power screws are made with a tip that functions as a pilot drill; as the screw rotates into the wood, the tip drills enough of a hole for the screw to go in without splitting the wood.

     The power screws are more expensive, but they provide the very appreciated opportunity to change things around. Right now, we're in a headlong rush to get the castle ready for the event, but once the initial work is done and the castle is battle ready, there's no doubt that we're going to want to change this, redesign that and modify the other thing. Since the castle is screwed together, it won't be a problem to unscrew a section, make changes and reassemble in ever more interesting ways.

The safety railing

     The High Deck wouldn't be useable without a proper safety rails. There are two key code requirements for the rail: that it be at least 42" high, and that the horizontal rails be close enough that a ball 4" in diameter will not fit between the rails.

     Putting up the safety railing was straight forward enough, but I found it especially satisfying because of the remarkable difference it made in the appearance of the Phase One work. The deck, which was a lot more work, just sort of lays there and isn't very visually exciting, while the safety rails clue the eye into how much space the High Deck offers.

     Well, dear reader, this about wraps up the work on Phase One. The next phase will involve the construction of the first 48' of the castle wall; i.e. the 16' section with the gate, and the two 16' sections to either side of the gate.

     Each of those sections will involve a good deal of work; the center section because of the substantial amount of wood and metal work involved in building a gate that can be bashed open time and again, and the two side sections because each of those will involve the construction of a 4' wide staircase leading from the main wall up to the High Deck.

Construction Phase Two - Facing the Gate Section --- Notes from Windward, Vol. 62