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carpentry angles
I imagine it happens to most people. Every now and then you get a bolt out of the blue and say to yourself 'Duhh I'm a dummy.'
My latest bolt was that I've cut angles for cross bracing 'pragmatically' for many years. I take an angle with a a gauge and try to match the gauge to a T-square on a table saw. I never got it good enough and ended up cutting several pieces before getting it right. I did that because I always much further off when I tried to calculate the angles.
So, I was drawing a design I used for deck joists. I looked at the triangles made by the cross bracing. Eureka I said 'the triangle I need doesn't go from the top of one joist to the bottom of the next.' Two by fours still have thickness and width. The triangle I need goes from the top a joist to 1 3/4" from the bottom of the next. That's a real 'duh' 'huh.' Since I was on a roll, I hauled out ancient trig and log tables rather than a spreadsheet.
Well, it worked like a charm. I realize that all this is pretty basic for anybody done even a little study of carpentry and that real carpenters probably have tables that give lengths and angles for standard parts of conventional structures. It’s also real handy to actually measure 16” centers for the joists because then all the cross bracing can be cut at the same time.
My centers were pretty good even if each joist end is supported by a deck block set in the ground. Very tricky getting the centers accurate and the joists level using deck blocks. I did that because the deck is so low that rails used in conventional would be partially buried and parallel to the foundation. That would dam up drainage behind them against the foundation wall. I suppose there are other ways of accomplishing the same thing and maybe I’ll have another bolt out the blue next year.
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carpentry angles
So you are telling me I need to trim the 3 ft high stack of factory cut cross bracing I have in the basement, rather than trim trim them with a had saw when the 16" center is a little under.
Where were you last week?
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carpentry angles
Actually Tom, I use an even (IMHO) easier method than that. It goes like this, 1) measure the inside gap between the joists (and assuming they are uniform across the entire structure of course, otherwise repeat 1) each time), 2) measure the vertical height from the bottom of the joist to the underside of the decking, 3) lay a framing square across the 'blocking' material with one intersection (of the wood & square) at the dimension of the vertical distance, the other at half of the inside gap measurement. Now scribe the wood along the edges of the square & cut, VOILA!! a fit as accurate as your measurements. Best of luck.
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carpentry angles
Murf: You also simplified my percent grade problem. If I keep at it I might acquire a collection of traditional techniques that can keep me away from my calculations. In Toronto, it's worth visiting Black Creek Pioneer village just to see the framing done by the Mennonite farmer/builders. I don't imagine they calculated lengths and angles much. I'm not sure I completely grasped the idea from the description though. I'm probably missing a piece this morning cause I'm preoccupied with the calculation free task of spreading and grading 15-yards of gravel this morning before it gets too hot.
Peters: I'm guessing you're not entirely serious and know as well as I that wood is pretty forgiving stuff. Besides, the x-bracing in conventional framed floors serves to keep long joists from warping at the unsupported bottom edge and to distribute floor loads to adjacent joists. I don't think they have to fit as well as the joints in loaded members. Braces that are a bit long leave some excess at the bottom of joists, and it's not uncommon to see some that were whacked off with a chisel.
However, I do hope that the centres weren't 'scrunched' significantly rather than putting in one short centre joist if the floor area wasn't a standard length. Wood isn't completely forgiving, and I'd sure hate to trim a 3' stack of braces. I used a non-standard floor length in my deck and stuck with 16” centres even though it left me with one 11" centre joist. I had to do my calculations again for just one joist. I put it at the end of the deck where foot strike of people coming down a stairs would fall. I wanted an extra joist there anyway.
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carpentry angles
Tom, you bring up a good point about the workmanship of 'uneducated' tradesmen such as the Mennonites. In fact I don't have to go any further than about 500' to see it though. In our 'neck of the woods' we were blessed with travelling groups of Mennonite carpenters would build under contract to the farmers (the entire family came along, children learning at their parents sides, and the women keeping 'house'). This was a common occurance that lasted into the late 1950's in this area. To this day I doubt you could put a slip of paper between any two framing members in my barn, and except for what holds the steel on the outside I doubt there is 10lbs. of nails in the whole thing, it is all pegged mortice joints, built exclusivley with muscular powered tools to boot! Best of luck.
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