What is the difference between a dutchman patch and a butterfly patch?

Question

In How can I repair a split in a board?, the accepted response suggests a "dutchman patch," but I'm getting mixed messages from various sources. Some show a dutchman as being the removal of damaged material and insertion of a patch of the same size. Others seem to specifically be a bowtie/butterfly shape reinforcing a crack in wood.

For instance, both of these images are being referred to as dutchman patches:

^{Source: https://makezine.com/projects/dutchman-wood-repair/}

^{Source: http://www.woodworkingtalk.com/f5/pre-dovetail-butterfly-dutchman-joints-question-36119/#post306942}

So which is it? Is there a difference between a dutchman patch and a butterfly patch? Is this just a case of the same phrase meaning two different things?

Is a dutchman a general term and the buttefly specifically that shape of dutchman?

Answer 1

So which is it? Is there a difference between a dutchman patch and a butterfly patch?

Yes and no. A Dutchman can be the shape of a butterfly (also called a bowtie) as well as many other shapes.

But a butterfly in modern usage typically means a wooden fixing to secure or stabilise a crack.

This is yet another example (of many!) of terminology being used loosely or irregularly in woodworking.

Note: Dutchmen patches are usually thin, and can in fact be made from veneer, butterflies or bowties are typically thick because of their structural requirement.

Answer 2

A dutchman patch is basically using wood to fill a void larger than can be done with filler alone. A butterfly patch is typically used to prevent a check from getting larger, or to reinforce a joint. You could consider a butterfly patch to be a specific case of a more general dutchman patch.