Wednesday, November 17, 2010

The Trigonometry Of Framing

Imagine you had a trianglular wooden painting that measured 300x400x250mm on the sides. You don't know the angles. You have some framing wood with a deep 24mm rebate. You need to know what length the wood needs to be on the internal edge, and at what angle to cut the ends too. Quite a conundrum!

I'm faced with just that (well, apart from those specific sizes) for the painting below so I've written a small program in Visual Basic to solve the riddle. One day I'll probably adapt it so that I can cut the angles for any quadrilateral... just in case!


Thanks to the Internet I managed to program this without actual mathematical knowledge. Phew. I can't ever recall hearing of the law of cosines before but now I have.

Alas I don't have a mitre saw so I'll have to saw the angles by hand. Awkward, but possible. I've done it before and the results weren't that bad.

7 comments :

-Don said...

Yikes! Good luck cutting the angles without a mitre saw. That's going to be fun. (If you want to swing by and pick it up you can borrow mine.)

Have fun!

-Don

Robin said...

And this is what you do when you are on rest time?!

Mark Sheeky said...

Maths is fun Robin :) I mitre take you up on that Don (groan - sorry for that awful pun.)

Peggy Stermer-Cox said...

Hi Mark, Yes, good luck! Nice to be able to right a program to figure your framing requirements out. We used to have a mitre saw, but sold it to the neighbor so he could have two! My Dad used to be able to cut with out a fancy-dancy mitre saw; don't know how he did it though! I know, no help at all!

Mark Sheeky said...

Hi Peggy, When I tried to cut without a mitre, I just drew a pencil line on the wood and sawed very carefully! Maybe your dad did it that way too.

John Salmon. said...

You could clamp the pieces to the shape you want and saw at the intersection. That way you would be sure that the fit was good.

Kathy said...

I like your inventiveness ... and, I agree that math is fun - especially geometry!