Working Backwards

First, a quick announcement. Openings in my classes for this year are almost gone but there are a few spots left to anyone who doesn't want to wait until next year.
I will be at the Connecticut Valley School of Woodworking teaching the Continuous Armchair
Friday – Sunday April 11 – 13 & May 9 - 11  There are only a couple of spots open here.

And I have three classes this summer here in Sterling MA
June 23-28 Fan Back Side Chair

July 21-26 Balloon back Side Chair

August 11-16  Continuous Armchair (chairmaking experience required)
Each of these classes has a couple of openings, please contact me for more information


Hopefully you have seen the posts and videos that I did regarding my sightline rule. The sightline rule is basically a chairmakers framing square that eliminates the need to use trig tables or elaborate graphics to transform rake and splay into sightlines and resultant angles. If you didn't see them, check out this post ,or this one, or visit my youtube channel to see videos on the sightline rule.

Anyway, I've found one more handy way to use the sightline rule, which is to take an already existing pattern and derive the rake and splay from it. This is very handy if you want to use the same angles or change angles on an existing pattern and don't know the rake and splay. Here is an example

So there it is, rake of 17 degrees and splay of 16.5. Of course, if you knew this info first, you could simply follow the drawings in reverse to get the sightline and resultant.
It was a slap on the forehead when this one dawned on me. I still have the pdf's available if anyone wants the printout, email me at peter@petergalbertchairmaker.com

Sightline Rule Refined

I've been all over the map lately, but I am home now for a few months and am excited for all of the new stuff that I have to show. First, I'd like to share the sightline square that Steve First made for me (us) at Kelly Mehlers. It's a beautifully accurate way of creating the sightlines and discovering the drilling angles for laying out legs mortises etc...
He made to versions, a large legal version and one that fits on normal sized paper that requires a bit of cut and pasting but works just the same.
Here are the PDFs (actually JPEGS)

I've also made this video to explain the use of this tool and a bit about rake and splay.



You'll also notice, in the upper right column, that you can subscribe now via email to the blog so that you'll be notified when I post new content! Doesn't life just keep getting easier :)

Sightlines Revisited

I recently had a "eureka" moment, or perhaps a "duh" moment working out some sightlines for the two walnut armchairs that I am making. ***please see the edit at the end of the post***

I've shot a short video explaining the details.



Hopefully the video clarifies the process enough, but if not, here is the brief synopsis. The sightline is based on a relationship between the amount of rake and splay that you want. If the rake and splay are equal, the sightline will always be 45 degrees. By using a straight edge with marks based on degrees from a single point, the incremental increase of distance is accounted for and we can use this scale for direct layout. If you are dying to know why this works, take a look at this drawing of the graphical process. (and perhaps visit this posting and it's second part for a refresher)




You'll notice that all of the views of the chair come together to make a small triangle. Well, by using the special rule based on degrees, we skip all the steps and simply make the triangle directly on the pattern. What enchanted me about this was the ease of finding the resultant angle by measuring the hypotenuse. Perhaps I'm just a total nerd, but this one made my day!

*** One of the comments that I got questioned whether the Bevel Boss scale was created by measuring from a single point for all of the angles. This method presupposes that it is, and it isn't! That's the bad news, the good news is that the angles below 30 degrees do converge nicely and since theses are the numbers usually used in chairs, the scale should work fine. .***