Dapping

Overview

Dapping is a transitive verb meaning to cut and form a recess in (timbers) for making a joint (Merriam-Webster). This makes a strong connection unlike a simple butt joint. It seems that most jointery in model railroading timbers uses a butt joint – weakest joint of all. The extra work required to dap the wood is mostly simply ignored.

I have a Proxxon MF70 Mini-Mill which I have mostly used to dap stripwood. Using Dremel router bits this works very well. The hardest part being the setting up.

Since I enjoy the actual modeling the extra time spent to dap the timbers for me is part of that enjoyment. In any case this is how the timbers may have been joined in “real life” for strength.

Angled Joints

Most of the dapped joints are straight forward in that you simply make a notch across a piece of wood equal to the width of the framing member that fits into it. The ‘problem’ is when there is an angle to the joinery and for me this raises the question as to how best do this. Following are various joints with one timber at 45° to the other timber and my comments on each. I colored the 45° timber white and the vertical timber blue. These are 1/4″ stripwood which represents 12″ timbers full-size. The cutter represents a Dremel 1/4″ router bit.

A

This is the ubiquitous Butt Joint. This is used a lot for constructing things like ore bins and honestly can be quite strong when used in a model. If yellow glue is used the joint can be stronger than the wood – breaking the joint often will tear the wood fibers rather than the glued area of the joint.

Still .. not prototypical in many cases.

B

Simplest dapped joint to cut .. and .. EXTREMELY week point as there is only 0.070″ left of the timber – effectively reducing a 12″ beam to a 3.36″ beam at this point.

I only put this in to make a point.

C

Hard to cut the area circled in red. It would require using a sharp chisel and a delicate touch. Even if successful that sharp point would break easily.

The other side of the joint would be easy to file.

D

Relatively easy to cut. The angled shoulders of the notch easily filed to shape – carefully. A small sanding block with a 45° with sandpaper glued to it would make the process easier and most likely more accurate.

The flattened ‘tip’ of the vertical beam again would be easy to do. With the beam laid flat a sanding block would ensure the angle was accurate.

This would require sanding three angles.

E

Relatively easy to cut. Like I said above a small sanding block with a 45° with sandpaper glued to it would make the process easier and most likely more accurate for the angled shoulder on the notch.

A sanding block with a 45° side would make quick work of the angled tip on the vertical timber

This only requires sanding two angles and is my favorite method.

F

Relatively easy to cut the angled timber notched to the 0.312″ width with two passes of the cutter with the mill table moved 0.062″ for the second cut.

The notch in the vertical timber would require a jig and some fiddly work. It would also require that the vertical timber be slid into the joint from the side .. still more fiddly work.