Math

[GhostFist]

Are you a numbers person or do you have your own "ultimate method" for determining common woodworking problems.
For instance, you're building a fence and need to determine spacing in between slats. There are three sections of fence, post to post distance between each section is as follows; 1st section 73", 2nd section 76 1/2", and the third is 82 1/8". the slats are 5 1/8" wide and you want roughly a 2" space in between.

What is YOUR method for solving this common problem? I've seen five carpenters each with their own method, none 100% clear on how to execute it argue amongst themselves to determine which method is best. This is a common mathematical problem and can be used for laying out wall paneling, to making head boards for beds, porch railings well anything that requires an equal division of solids versus voids.

Curious to see how many different solutions come up.

 

[jonny round boy]

There are three sections of fence, post to post distance between each section is as follows; 1st section 73", 2nd section 76 1/2", and the third is 82 1/8". the slats are 5 1/8" wide and you want roughly a 2" space in between.

Well using metric would be a good start... [poke]

[tongue]

 

[Deansocial]

add the total minus 1 slat then divided by 1slat+ideal spacing take answer and round to nearest number.

take total-1slat again divided by last answer minus 1 slat=spacing

if i understand you correctly

 

[Deansocial]

There are three sections of fence, post to post distance between each section is as follows; 1st section 73", 2nd section 76 1/2", and the third is 82 1/8". the slats are 5 1/8" wide and you want roughly a 2" space in between.

Well using metric would be a good start... [poke]

[tongue]

thats why i didnt bother working it out, too much faff with gimperial

 

[Holzhacker]

Not sure what you want to figure out here and make it over complicated. Since the difference between the sections is essentially one slat. Build one section, whichever one you choose, to the exact spacing dimensions. Fudge the 1/16" - 18" spacing difference on the last few slats on the other two sections. No one will see the difference. If for some reason it has to be really precise for a fence (picky client); split the spacing difference 1/2 between spacing and 1/2 between ripping a bit off of a few slats. It's a fence.

 

[Jesse Cloud]

Not sure what you want to figure out here and make it over complicated. Since the difference between the sections is essentially one slat. Build one section, whichever one you choose, to the exact spacing dimensions. Fudge the 1/16" - 18" spacing difference on the last few slats on the other two sections. No one will see the difference. If for some reason it has to be really precise for a fence (picky client); split the spacing difference 1/2 between spacing and 1/2 between ripping a bit off of a few slats. It's a fence.

Well said Holzhacker!

Every now and then I find myself scribbling out calculations and then think, "What are the odds that all those are correct?"  Then I just measure part A with calipers (taking care never to look at the number), use that to mark the spacing on part B in a place that "looks good." 

 

[VictorL]

Well using metric would be a good start...

Yes, metric is much easier for math unless you sticked to 16" between studs

 

[mastercabman]

Well using metric would be a good start...

Yes, metric is much easier for math unless you sticked to 16" between studs

Yes,but we are not talking about studs [laughing] [laughing] [laughing]s!!!!

 

[mastercabman]

Really it's not hard.Add the width of the board + the space in between.
Divide the overall by that number and you get what you need.At that point you can make some tweaking about the spacing once you get the answers for each sections.

 

[GhostFist]

Ya I agree with everything I'm personally not trying to determine anything. I use that standard division method, total minus one slat and so on. I was just amazed to see a bunch of guys arguing about this on a site recently and was curious as to how many ways there are to screw up this common problem. I'm with you on metric as well, a lot of crapenters still swear by imperial here though. I'm not saying you lot would screw it up either just curious thats all as to different people's methods.

 

[norwegian wood]

i use the iphone baluster app. works awesome

 

[Wim]

I'm so spoiled by computers, I make this into a formulea and open it in a spreadsheet. With the what-if method I try a few possibilities until I find the right one. Works like charm, especially when you have three different distances between the posts.
I did the same for drawers. Input the thickness of the plywood, the width, depth and the height and presto, I have a dimensional list of all components.

 

[mishle]

I would use sketchup that way I can change the spacing by a 16th of an inch or what ever needed to give it the best look before I start. Yes I take my computer to job sites.

 

[GhostFist]

Hmm interesting, using computers. how well does everyone trust their eye? ever tried this????
http://woodgears.ca/eyeball/

 

[mishle]

pretty cool http://woodgears.ca/eyeball/

 

[Wim]

One of the things they teach you in Holland in the technical field is: Gissen is missen, meten is weten. Or in a sort of translation: To guess is to miss, to measure is to know. So if I can measure, I will do it. If I have no way to measure, I will give it my best shot.

 

[kdzito]

Actually my first comment is why did you set the posts at unequal distances of each section?

1st - Regardless of my question above and assuming that you are putting the slats on furring and surface mounting the furring to the posts then I would start at the center (middle) of all 3 fence sections being combined and work outwards and at the ends you wind up with both slats being of equal width.   Thus you have a fence run of a symmetrical proportion.

2nd - Just take a spacer block 2" wide and hold in between each slat being fastened to the furring, thus no difficult math calculations except for the layout in the entire run of all 3 combined fence sections when fastening the first slat.

For layout a carpenter always works from either top down or center out and tries to use math as least as possible.  

 

[Ken Nagrod]

Actually my first comment is why did you set the posts at unequal distances of each section?

1st - Regardless of my question above and assuming that you are putting the slats on furring and surface mounting the furring to the posts then I would start at the center (middle) of all 3 fence sections being combined and work outwards and at the ends you wind up with both slats being of equal width.  Thus you have a fence run of a symmetrical proportion.

2nd - Just take a spacer block 2" wide and hold in between each slat every time you fasten it to the furring insert the block and thus no difficult math calculations except for the layout in the entire run of all 3 combined fence sections when fastening the first slat.

For layout a carpenter always works from either top down or center out and tries to use math as least as possible. 

What happened to bottoms up?  [smile]

 

[kdzito]

Actually my first comment is why did you set the posts at unequal distances of each section?

1st - Regardless of my question above and assuming that you are putting the slats on furring and surface mounting the furring to the posts then I would start at the center (middle) of all 3 fence sections being combined and work outwards and at the ends you wind up with both slats being of equal width.   Thus you have a fence run of a symmetrical proportion.

2nd - Just take a spacer block 2" wide and hold in between each slat every time you fasten it to the furring insert the block and thus no difficult math calculations except for the layout in the entire run of all 3 combined fence sections when fastening the first slat.

For layout a carpenter always works from either top down or center out and tries to use math as least as possible. 

What happened to bottoms up?  [smile]

That's at the end of the day, drinking!!!

 

[atomicmike]

What happened to bottoms up?  [smile]

Why do you think the posts are spaced unevenly?  [big grin]