TOPIC:

Hi Folks,
Please indulge me while I start a thread that doesn't perzactly deal with 1300 Kaws.
I'm fortunate in that as a part of the my full time job I'm part of the company's Innovation Group. A couple of years ago I built a CNC Router that can accept a 4' by 8' sheet of plywood.
Last year I imagined a new type of wood joint that could be used to join sections of wood in a manner that engages the faces of the boards in compression and tension. I'm thinking that this new joint will have structural advantages over more traditional methods of joining two boards such as doweling or mortise and tenon joints, which typically join the boards at the neutral axis.
When I imagined this new joint, which I call a "Bulb Joint", I didn't think I'd invented something new but rather just combining existing technology in a different manner. As a matter of fact my IT guy, found a similar joint on one of the Do It Yourself CNC websites. My joint is different in that each board has both male and female parts and that each side of the joint is machined exactly like the other side. When joined together the boards grasp their mates just as ancient Romans used to shake hands by grasping each others forearms.
Here's a picture of two boards, one of which must be flipped end for end to be joined.


Until now I'd only used bulb joints to make picture frames and various cabinet / fixture types of projects. This fall I decided to venture out into the realm of structural applications by building an 11' by 16' shed that will have a barrel shaped roof. The picture above is of two 2" by 8" pieces of Douglas Fir that will join four other pieces to make one complete arched rafter.
Here are the rafters joined together and stacked on the floor of the shed.

Here's another picture of a few sections joined together on my work bench.

Now that I've assembled the rafters I'm going to frame the walls and then stand up the rafters. I'll be adding more pictures as I go along.
Bill

Nicely done Bill !

Well, I've never seen the likes of that, other than in some jigsaw puzzles. Those joints not only look beautiful, I guess they'll be very strong. I can't picture what the finished shed will look like, but I'm looking forward to finding out!

There are some seriously talented people on this site. I really enjoy it when we share our technologies with each other. I have a strong background in machining and welding but have had no exposure to CAD CAM so here it sit for hours on end "designing" a camshaft profile to incorporate valve velocity and acceleration /decelerations then mapping it out only to find that what would work by design will not work out due to flat tappets. If I was a CAD versed person, this whole adventure of mine would be a piece of cake but I'm old school. I bow to those who have kept up with the new technology. My work career was all about keeping a 1970's designed reactor and associated equipment running and nothing to do with manufacturing. I'm good at what I know but wished I had done some "extra curricular training". The flip side is if you don't use it, you lose it.

Looking forward to following your "build" Bill. Very interesting wood joint which could only be done with a CAD/CAM set up. Very Nice !!

Hey Bill looks very interesting
always admire those who step outside the box
how are you holding it together laterally ? epoxy glue and clamp / or Screws?
can i ask respectfully would a Dovetail joint lying flat achieve the same result if you stepped it as you have in 2 layers
Dion

Dion wrote: Hey Bill looks very interesting
always admire those who step outside the box
how are you holding it together laterally ? epoxy glue and clamp / or Screws?
can i ask respectfully would a Dovetail joint lying flat achieve the same result if you stepped it as you have in 2 layers
Dion

Hi Dion,
My bulb joint is essentially a dovetail joint so yes if stepped to have male and female sections it would do the same thing. Of course the typical angular, sharp cornered dovetail cannot be achieved with a spinning router bit orientated perpendicular to the work piece.
I spent some time deciding on which sort of glue to use and finally settled on Titebond Type III. Franklin Industries typically refuses to approve structural uses of their glues, however they're quick to point out that their glues are fine for structural applications as long as the design is signed by an engineer. For the rafters shown, earlier, I've just glued them. For my "Barge Rafters" (Overhanging Facia on the gable ends.) I'll be using a single bulb that will be glued and bolted. The picture below might be a bit confusing because the boxes on the ends are really just an area to be pocketed out by the router. But this will be how I'm joining the Barge sections. There will be some sort of antiqued bolt going through the center of the bulb.

Sorry if that's too much information.
Bill