Modular Tansu 2.0

A few months back a customer reached out asking if I could build a version of my Low Cherry Tansu as well replicas of the accompanying smaller tabi-dansu. They more or less wanted the same thing as what’s pictured here on my site, including the same hidden mitered dovetails on the low cherry tansu, as well as pegged box joints for the two tabi-dansu. One request which is a departure from the original is the scale. They asked me to make the cabinets nearly 2x larger. After some further discussion and working out pricing, it looks like the project is going to happen.

(Here’s my original set of modular tansu, including the Low Cherry Tansu which I designed and built, along with two antique tabi-dansu sitting on top):

As a woodworker, you’d think that any job that comes your way would be cause for celebration, and deep down it is exciting and I’m thrilled anytime I get a request to build something special. But new orders also come with a reality check that now the pressure is on to make something that lives up to, or better yet, exceeds the customers expectations. That means envisioning and working out any problems that could arrise either with the construction of the piece or down the road once it’s in the customers hands. Not to mention just thinking long term about the life of the piece and it’s functionality.

In the case of these cabinets the fact that they will be nearly 2x larger than the originals brings up a few particular challenges related to wood movement and functionality that I’m currently trying to work out.

One concern I have with increasing the scale of the cabinets is the likelihood that the lower cabinet could sag from the weight of the upper cabinets, especially once they are loaded up with stuff. The overall length of the scaled up lower cabinet will be nearly 2 m long or approx. 78″.

Sagging of the lower cabinet is particualry an issue when it comes to the functionality of the drawers and door. The door in particular is a Japanese style ken-don door, which sits in a set of grooves cut into the top and bottom panels of the main case. Removing the door involves sliding the door up into the deeper upper groove and swinging the door out from the bottom. Here’s a quick video showing how the door opens:

I like this style of door a lot, but you can imagine how any movement/sagging of the cabinet would negatively affect the functionality. So how to design and build the cabinet in a way that prevents sagging while also maintaining the overall lines and proportions of the parts is the big challenge. The back of the cabinet is one area where I can add a ton of strength and resistance to sagging. But another area I’ve been considering is the base.

Probably the simplest way to reduce sagging would be to incorporate a leg or two in the middle of the base, but clearly that would also have a huge affect on the aesthetics of the cabinet and that option was pretty quickly set aside. Another option which I’ve been thinking about is reinforcing the long support rails of the base with a stronger material, and brass is one material that comes to mind. My initial thought was to sandwich a piece of solid brass between a couple pieces of cherry forming a laminate of wood and brass to form the long support rails.

I have to imagine the brass would really stiffen up the support rails, and it would be a nice little special detail for anyone who cared to get down low and admire the ends of the base. I still have to work out how certain aspects of the base’s joinery would work if I go this route, but overall I think this has potential.

Another big challenge with scaling up all three of these cabinets is the door construction. Specifically how to build the doors such that they aren’t too heavy, and so that they stay nice and flat. With the ken-don style construction and the need to fully remove the doors to open up the cabinets, the lighter the door the better if you ask me. The original antique tabi-dansu are made from paulownia (Japanese: kiri 桐) which is extremely lightweight material, almost like balsa wood. Given that the new cabinets will be made from hardwood, plus the increase in overal scale, the doors are definitely going to weigh more, but my goal is to keep the weight as low as possible. That means figuring out a construction method that allows me to keep the door parts are thin as possible.

I see two option for constructing these doors, namely the solid wood approach or a veneered panel approach. I’m definitely partial to the solid wood approach so that’s where I’ve been focusing most the past few days.

Looking at the inside of the Long Low Tansu’s door here is an initial concept for reinforcing a solid wood panel. The orientation of the panel is in keeping with the original antique tabi-dansu and their doors with vertical straight grain, but it’s definitely not the easiest or pehaps smartest way to build a door. My thought is to reinforce the panel with battens that run across the grain, using unglued sliding dovetails to join the battens and panel. The battens could then be joined to the vertical frame members of the door with mortise and tenon joints.

Here’s version 2.0 of that concept, this time reducing the horizontal battens down to just one piece, and incorporating a pair of vertical supports to reinforce the horizontal batten. The horizontal and vertical supports are all much thicker than the door panel and frame parts in an effort to maintain as much stiffness as possible, hence the ends of the supports which taper down to cleanly meet with the surrounding frame. I came upon this idea after reading through Chris Hall’s blog recently, but now that I think of it, this style of construction is also really reminiscent of the inside of an acoustic guitar.

Here’s the frame work with the panel removed.

And a close up.

On my original Low Cherry Tansu the door measures around 708 mm wide x 275 mm tall x 15 mm thick (27 7/8″ W x 10 3/4″ T x 5/8″ D) and the panel itself is close to 630 mm wide (24 3/4″), and made up of a glue up of quartersawn strips of solid cherry. The panel itself is 10 mm (~3/8″) thick and there are no internal supports or cross bracing. Building the door this way was defnintely a bit of an experiment, but so far over the past couple of years it’s been just fine. Japan’s humidity level is fairly stable, but even so the door has stayed flat and the panel only moves a small amount relative to its width. In winter when we are using our heater and the air gets drier the panel shrinks opening up a 2 mm gap on each side of the door, and during the hot humid summer those gaps all but close as the panel expands. All that is to say that so far my experience using a door of this style with a quartersawn cherry panel has been enlightening and it’s nice to have an idea how much the wood will move.

But again, in scaling up the design I think it definitely makes sense to reinforce the panel with some battens, especially since the cabinet will be heading to a much drier climate than Japan.

An alternative to the solid wood door approach that I’m considering is to make a veneered panel. A veneered panel should in theory be far more stable and less likely to cup/warp/shrink excessively. However my experience with veneering is somewhat limited, and here in Japan things like vacuum presses seem to be virtually unused. Vacuum pressing and veneering is pretty common in all sorts of work back in the US but that seems to be not the case here in Japan. I can’t even find a vacuum press kit or supplies here. Instead what most people seem to use are massive clamping presses like this one:

These presses seem to come in a huge variety of sizes and styles, and I could see how they could be useful if you have the space. But I definitely don’t have the space, and I don’t know of anyone who has one of these, so I’ve been searching for alternative options instead.

One option I’m interested in are the vacuum press kits sold by ROAROCKIT. I have no experience with their products but from appearances I feel like a simple vacuum kit with hand pump like theirs could work for a couple simple veneered panels. If anyone has any experience with these I’m all ears. The main benefit with a kit like this is that I could order and have one shipped to Japan relatively easily, compared to a more full blow vacuum pump setup.

So that’s where things stand at the moment. Ultimately the wood choices for these cabinets has yet to be officially decided but once that decision is made, I’ll be sourcing some material and begin work on the smaller cabinets.

More on this project next time.

Thanks for visiting.