About to begin making a medium size dobsonian. Nothing fancy, and the focus is on simplicity, familiarity, and speed of execution. I just want to get it done quickly without wandering off into experimenting with new designs, which is what I tend to do unless I stay focused on more immediate goals. I need the instrument up and running before the Mars opposition, and I have yet to polish and parabolize the primary. Loosely based on the Obsession / Kriege template, but with a few twists.
For the UTA (upper tube assembly), I'll make it from two rings of thick plywood joined by a cylinder. I may have a few columns joining the two rings, for strength - but one of the twists is that the cylinder will be load bearing itself, and structurally strong.
Basically I need to make a hollow core cylinder - two sheets of some bendable material, epoxied to some cellular core material of sorts. I need help with choosing the materials.
Plywood doesn't seem like a good option for the sheets, does it? If it's thin enough to bend, it's probably thin enough to crack when pushed or bumped into.
For the core, I could use kevlar honeycomb from the carbon fiber store (they use it to make carbon fiber hollow core sandwiches), but that's the high end choice. What would be the midrange choice in your opinion?
I could make the cylinder from carbon fiber and kevlar, but that's the fancy experimental design I want to avoid, for lack of time. Although the material properties of this combo are pretty sweet.