Spar thickness (1x2 VS 2x2)

[klattin3]

Do i have to use 1 x 2 spars or can i use 2x2 ? i havent measured the thickness of insulation yet for the roof. Can i go with the 2x2 and use house insulation like R19 instead of the rigid foam stuff?? has anyone tried that??

Also, can i use pine (2x2) for the hatch spars or should i go with poplar like the generic benroy plans suggest because of the harder wood.
Thanks. Keith

[bobhenry]

Most 2x10's and 2 x 12's are southern yellow pine which is about 50% stronger than spf grade lumber I cut my 2x2's out of 2x12's you need to look them over because due to grain release some will go a bit wild. Cut a few extra and select the best and straightest. Let them rest a couple days because as the dry they may twist and or curve. I personally would avoid spun fiberglass because of its nature of trapping water in the voids. The foam is easy to work with and will stay in place without glues or fastners. Just my opinion I am sure others will differ..

[Juneaudave]

Keith...I'm sorta at the same point that you are...putting in the spars and insulating. My spars are 5/4 spruce ripped to 1 inch, with 1 inch of rigid Foamular.

I don't know what the magic formula is...but what I have discovered (and other builders have said, and I didn't really understand) is that the curve of the roof adds an incredible amount of strength. Even with 1 inch spars..I think I could do the "Turkey Trot" on top and it would be fine. From a practical standpoint...your spars need to be of a diminsion that will allow you to properly fasten them to the headliner and sides. If your design is flat roofed...you might have some other strength considerations as the curved surface of a traditional Tear does add strength....Juneaudave