1. What would be the best wood to use?
Though species do differ in their mechanical properties...grade, joinery, and wood quality...are the focal points.
2. How green can I use them?
Fresh out of the tree is fine...They only get stronger with age, with very few (if any?) exceptions if selection of the above elements are executed properly.
3. What would be the smallest diameter I could use to make a (standard?) truss? I am familiar with what the different truss styles look like. I am just not sure if there is a standard, or one better suited for building with roundwood.
Round or even live edge wood is stronger than canted (squared) timbers. As for size, that all depends on the load specific dynamics of the design sought. Style to is a mater of design parameters. The most common is probably the King and/or Queen truss systems in many timber frames.
4. What would be the best way to connect them? The type of joint, metal connectors?
I abhor the aesthetics of most metal connectors in timber frames...and...most are not necessary. With that said, truss design is not really for the DIYer, so lots of metal ($$expense$$) is going to be the easiest and safest option. Truss work is perhaps some of the most advanced timber framing and engineering one can find in a structure. Mistakes are easy to make by not understanding all the "load potentials", wood species dynamics, joinery parameters as it affects design in relationship to engineering, etc, etc,...and...these failures are usually referred to as "catastrophic failures." I have been doing this for a very long time and still have 90% of my work "back checked" by a PE I have worked with for 30 plus years that also has a timber framing back ground. This is not all said to discourage...but to warn....Be careful.
I have about 8 acres that is all wooded, and could use some thinning. Which is why I was hoping to be able to find a way to use them, instead of having to buy pre-made trusses.
It can be done, and with the correct skill sets, very enjoyable and rewarding outcomes. It is a massive undertaking, and lots of studying/learning is in order...
To achieve just the basics:
Understand center line layout completely along with scribe and template methodology.
Understand joint design thoroughly.
Know/understand the load potentials for the truss system selected.
Be able to visually grade, and assess the different tree species to be selected.
In reconsideration of this post query, I must share that almost all this information is out there and in good order; both in books and on the web. It is not a "1, 2, 3," type of subject and the information is not presented and/or delivered in a format that most lay-folk are going to really interpret well or easily, nor does it illuminate simple instructions. My book list on Amazon is permies, and the timber frame books there covers this subject thoroughly. More questions though are welcome if you have them.
Regards,
j
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