TOPIC:

Hi Folks,
Please indulge me while I start a thread that doesn't perzactly deal with KZs.
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

I've been working my butt off to try to get under roof ahead of the winter weather. Didn't make it. No snow yet but it can't be far away. I did get all the rafters up today and managed to pull a tarp over the whole thing. Still got to add the barge rafters (Gable Facias) before I can sheet the roof.


What do you think?

A modern Quonset hut,
That's a great idea for a joint Bill.
Are you using a urethane glue?

Nice Bill
Has the potential to be a very marketable idea.
Does away with the need for gang nail plates , so you save cost and probably longer fire resistance .
Great innovation
Dave

Street Fighter LTD wrote: Nice Bill
Has the potential to be a very marketable idea.
Does away with the need for gang nail plates , so you save cost and probably longer fire resistance .
Great innovation
Dave

Actually I doubt that it'd ever be a marketable idea given that each section took 45 minutes to machine out on a CNC router. Even if I optimized the the code, I doubt that I could shorten the time to less than 30 minutes. There are nine rafters with six sections per rafter. Fifty-Four times Thirty minutes each is still Twenty-Seven hours just to cut out the parts. No I did it just because I imagined it and I imagined that I could do it. That's not meant to diminish your compliment. Thank You!

bluej58 wrote: A modern Quonset hut,
That's a great idea for a joint Bill.
Are you using a urethane glue?

I considered using urethane glue but I've had issues with it foaming up and separating the pieces. In the end I used TiteBond Type III, which is supposed to be water proof. I called Franklin Industries about their "Not for Structural Applications" disclaimer and was told "Why should we accept any structural liability for a two dollar bottle of glue." When he turned, with the other side of his face he said that folks use their glues for structural applications every day but if I wanted to I'd best hire an engineer.
I also checked on resorcinol glues only to find that they're hard to get, with manufacturers wantin to only let certified users purchase them.
I've got a plan for the barge rafters that relies on one three inch bulb in a two by six section that I hope will be attractive.
It'll look something like this:

That's an unbelievably cool idea.....I am always interested by thought processes like that and as a professional modelmaker I have been building models of stuff like this for a while. I can only imagine what that might do if one were able for example to transfer what you did in wood into metal, braze the joint and leave it visible....etc. etc....?

edit: It would also make that joint stronger by interlacing the metal and not relying on a weld for strength.

My CNC router broke down and it took two weeks to get a new spindle. I'm back at it again. Take a look at my first Barge rafter.







Still got a lot of work to do but I'm pleased that these fit as well as they did. These barge rafters are trickier because I have to pay attention to which surface is up so that the texture all matches.
Bill

That is a really cool idea Bill. I get your idea about the grain surfaces matching but will that not tend to make the assembly want to twist in one direction as opposed to flipping each piece to limit that? Don't mind me, I tend to overthink wood movement instead of the practicality sometimes. I think your idea would give a cool stained look in a cabin or bunkie application. There are also those out there who would pay for your time to have a unique product in their house.
Keep scratching the old noggin!
kawboy74

Good work. Is that spruce? I've used plywood and staggered the joints for top/bottom plates for round walls with plenty of screws. Never thought about doing rafters like that. A work of art or like Carl would say, "A thing of beauty and a joy forever."
Steve

Bill, did you manage to get a roof on your structure before things turned to cr@p? Got any more/updated PICs?

!Seymore wrote: Bill, did you manage to get a roof on your structure before things turned to cr@p? Got any more/updated PICs?

For now, all I've got on it is a good heavy duty tarp, so it's at least staying dry. I'm still cutting out sections of the barge rafters which I need to install on lookouts before I can start bending the plywood roof sheeting. I suppose, at this point, I'm just going to have to hope for good weather.
Regards
Bill

Have you considered corrugated metal roofing?
These guys will curve it and they are all over Montana www.bridgersteel.com/metal-roofing/curved