Designing With SketchUp, SketchUp, Woodworking Plans
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Designing Furniture in SketchUp #2

Every now and then, I get an email asking for a SketchUp model to be made to match a photo or a change to one of my woodworking plans. I’ve received two such requests recently. Because these projects can be very, very time intensive, I now only do this on a commission basis, meaning I get paid for the work.

Some of these design projects can be challenging. I’m not only replicating a photo, more importantly I’m determining the best construction methods. Take the dining table shown above. I got an email and a photo which asked for a SketchUp model. I stated my rate which was agreed to and the work began. The photo showed a table which was slightly larger than what the client wanted for his own home. So, the first challenge was presented: how to scale down the table without losing the original look. I think the end result was successful, especially the view of the side. The view from the end, is a little suspect because the side to side measurement is 36 inches. Take 36 inches and subtract for the leg structure and the seating space is impacted, but I think the design still works. And this is what the client wanted. From the very beginning, a lot of thought went into seating space and leg clearance. And a challenging task since an inch here or there can have a significant impact on the overall look and balance of the table.

The Legs

The client and I went through three versions of the leg design. The first attempt at the splay of the legs was at 35 degrees which I thought was close to the original photo. But the client wanted to see a 30 degree splay and ultimately 25 degrees which is what ultimately pleased him. When designing in SketchUp, the “Parallel Projection” camera view is very useful (Camera>Parallel Projection). This type of view is used in the images below.

Legs at a 35 degree splay.

Splay reduced to 30 degrees.

The final design with a 25 degree splay.

Because the legs splay, odd dimensions are created. For example, the length of the 25 degree leg with the angled ends is ~35 43/64″ from point to point. Note the “~” at the beginning of the dimension; in SketchUp, this means “about” 35 43/64. The actual dimension is more precise than a 64th of an inch. If I were to look at a woodworking plan with such detailed dimensions, I would consider the design unreasonable. Part of designing this leg is coming up with a way to reasonably draw the joinery. The leg contains a through mortise which has odd dimensions and there is a notch in the top which when centered on the end of the leg also has odd dimensions. I basically had to move the location of this joinery around until I got at least one dimension to a 16th of an inch.

Then, moving the joinery around meant that I had to consider dimensions of other parts of the table structure…

Note the table top undercarriage and the base structure.

I had to find reasonable dimensions for the framework which forms the table top undercarriage. And the combined end stretchers and center stretcher as well. When, for example, I moved the through mortise in the leg, that impacted the length of the center stretcher which became one of the dreaded odd dimensions. The same was true with the undercarriage. A lot of brain power went into the actual location of the legs and the joinery for the legs so I could call this a reasonable project.

One other thing: the legs in the first example are wider than the final design. The original legs looked too wide. Each time I took some width out of the legs, I had to again deal with odd dimension.

The Center Support Joinery

Take a look at the center, vertical support for the table. It (and the legs) has wedged through mortises. In the case of the joint between the center support and the long, left to right center stretcher, I spent considerable time trying to figure out what I was looking at in the original photo. I had never seen such a joint before. This is basically a knock-down table and this joint is extremely complex.

The center structure; original design.

In the image above, note how there is a left and right horizontal stretcher which is bisected by a vertical support. There is a through tenon in the middle of this joint with a wedge on each side (wedge not yet drawn in this image). As I studied this joint, I realized that it and the whole center structure is like something you would find in a timber framed house. This lead to a little research on various kinds of timber framing. I realized that all three pieces; the left and right horizontal stretchers as well as the vertical center support interacted with each other and the through tenon and wedges were what kept the joint strong. After thinking about this joint for a day or two, I recommended a change to the client.

The newly configured center structure.

I thinking was if this joint was anything less than perfect, the base of the table could sag. And everything depended on the through tenon being tight within the joint and the wedges being tight against the tenon and anything it touched. The second design above, shows a single horizontal stretcher with a center support which rests on the stretcher and a interlocking tenon with the separate arched piece. Still a complex joint, but one which is not so dependant on perfect joinery.

The Table Top

The photo which the client provided showed a table top which was basically constructed like a door. It was frame and panel with a middle horizontal rail. I could see nothing in the design of the top which allowed for seasonal expansion or contraction of the panels. The panels were a glue-up of eight or so boards. In most parts of the USA, wood will expand and contract and in some cases significantly so.

Nice, beefy breadboard ends.

I told the client I would design a table top which allowed for wood movement. I provided two options, one of which was pretty complex and a lot of work. It involved dominos and yes, I drew the dominos in place. The other design is what you see here, a simple breadboard end construction but I did make the breadboard end a little larger than usual. The tongue for the breadboard is 1-1/8″ which I think is considerable in size, but I did think about extending the tongue outward more.

The table top is attached to the the undercarriage by way of connector bolts and anchor nuts. I have drawn these items before so that was not too hard to use in this model, but the point here is that all the screws and bolts needed are included in the SketchUp model.

The Woodworking Plan

When designing for someone else, I have to consider the skill level of the client. In this case, the client is very knowledgeable woodworker. But still, I felt the need to provide at least a little documentation in which he could better see my thought process for building the table. The client asked only for a cut list which is no big deal, but I also provided a three page material cutting diagram and then the steps for construction. In all, the plan ended up being 22 pages in length which includes a cover page.

Cover Page

Page 3 showing the main construction methods.

Page 21, adding the top via connector bolts and anchor nuts.

In the end, everything went well, the client was pleased with my work (he thought all of it was awesome 😎). I made a little money, gained more design experience and made a new woodworking friend as well.

Last night, I completed the other paid project which was for a woodworking teacher who wanted to use one of my plans in his next woodworking class.

My next SketchUp project will be a new woodworking plan for my old tool cabinet.


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