Monday, October 26, 2015

Don't get all bent out of shape!!

                                                                                                                                                                       Sometimes in woodworking you need a shape that just won't work because of short grain issues, stock availability, design concerns etc. It comes to a choice of steam bending or bent lamination. When choosing bent lamination there are some concerns to consider. 
The First consideration is the form you wish to use for the glue-up process. I normally hate MDF with a passion, but for this application it works well. I have used cdx and a/c plywood, solid wood, and phenolic plastic to make forms and I like the smoothness of the form you can get with MDF, but they are very delicate and need to be stored safely. Laminating many sheets of MDF and using a pattern follow bit you can create a form of almost unlimited width, but they get heavy quick. When you use two piece bent lamination forms there is an inherent spring-back to the glue up that needs to be addressed so your piece will work out how you want.
Unfortunately we have to go back to math class before we can build our form. Working with your plan you need to discern your arc or chord depth, meaning the deflection the curve is to make from a straight plane. There are several formulas that can be used to approximate the final shape of the material after being removed from the form.

Fortunately we don't need to read "Composite Materials: Mechanical Behavior and Structural Analysis" to figure this out. There are some simplified formulas to be found from woodworkers who have experimented for years. Now we can move forward and feel safe using our good materials to produce the bend. The simplest formula is as follows;

Y=Distance the arc will change
X=Height of arc from base
N=The number of layers of material 
Using this equation if you have a curve with a chord height of 3" and you are laminating 4 strips of wood to make the curve you will have
 y=3/42 which will yield Y=.1875 or 3/16" difference.
Knowing this you can change your pattern to give you the curve result you are looking for.
The next thing to consider is the thickness of the material you are laminating. Again if you are laminating 4 strips each 1/8" thick your lamination will be 1/2" thick. Your form must be made with a positive and negative part with a 1/2" hollow between them.

After I have figured out the math and cut the layers out and glued them together it helps to run some bolts through the form to keep the layers from de-laminating under clamping pressure. I like to add a piece of  plywood to disperse the clamp pressure and protect the form corners form being damaged.
A good coat of finish on the form helps when you need to get the glue cleaned up. I sheet the form with a clear drawer liner as added glue protection. You have put a lot of time and material into building this form, anything you can do to keep it from getting coated in glue that can telegraph into the piece is good.

As you can see from my photos I have added strips of wood down the middle of the form, this helps keep the form even as it is pulled together. 
So now you have a form and have milled up your wood and you are ready to glue it up, dry test everything to make sure you have all the tools you need at hand and good luck. 

Monday, October 19, 2015

The year of The Book
This year has been a good year of book buying for me. I have tried to expand my chair book selection and I think I just about got it. It started earlier this year with the wonderful book by Peter Galbert "The Chairmakers Notebook". 
This is the best book on Woodworking let alone chairmaking I have ever read.

 Just recently I bought a few more that I feel are really worth the read.


 The current state of the art, with the who, the why, and the what of it  By Peter Bradford

Chairs By Judith Miller 

 Judith Miller also wrote the book on furniture, literally. If you ever want a comprehensive book on furniture her book would be it.

Chairs: A History By Florence de Dampierre

I have many books just solely about chairs and it might be a bit obsessive, but hey I am a chairmaker and there are worse things I could be obsessed with.
 I would say that woodworking is my healthy obsession.
I decided about 15 years ago to study woodworking in depth, in particular chairmaking. I have come a long way and this year acquiring these books has been helpful. 
I am not sure how interesting this blog will be to the average person other than to show I am batty about chairs, I guess that might be a good thing. There are many other books I have and a few I don't, contact me for a good list if you would like to know more.
Drawing in Perspective

You don't have to be an artist to be a woodworker, but a good foundation in perspective drawing can come in very helpful. I have the fortunate history of many art classes to pull from and I am often asked by clients to draw up a design that I have proposed. Being able to draw a design that will eventually resemble the piece you plan to build can make the process easier. I am a firm believer that a woodworker should always keep a journal of design ideas nearby to sketch out any ideas you can come up with. 

Perspective drawing will help immensely  when you have drawn out a shape you like and want to enlarge it to full size to be used as a blueprint. Without this you could be just guessing when it comes to production.

 The chair shown above was a miniature that was done in reverse where the full size drawing was done first and the reduction was done second. Using my sketch book I was able to make both plans using perspective drawing.
Sheraton, Chippendale, Hepplewhite all used perspective drawings to portray their furnishings in their books.

Knowing 1 point and 2 point perspective drawing is a valuable skill to have. It is used by architects and builders to draw up plans for buildings and can help alleviate the surprises that pop up when you are working out a piece of furniture. The 2 point perspective gives a view from an angle of the work.
This is a rough sketch that I did for a client of a bench I was contracted to build. It is done in the 2 point perspective and is helpful because you can see the piece in three planes at once. If you want to have three separate figures to work from try this trick to work up a blueprint.

1.  Draw up your piece from the front angle with height measurements needed.

2.  extend the horizontal lines to the right and using your depth measurements and angles draw in your side view. Above the first object draw a 45 degree angle from lower right to upper left. Take any vertical lines and carry them straight upward to the angle.
3. Now take the vertical lines drawn on the right image and extend them upward as you did with the first image. Use the intersecting lines from the 45 degree angle to deflect to the right and you can work up your overhead view.
You can use this to mark out joinery and make your patterns.
If you draw up your piece using the 2 point perspective and the blueprint view you can make a miniature or mock up of the piece to be made. Using these you can see your work from many different views and address any concerns before you have begun to use the good materials.
Using perspective drawing can make life easier.

Wednesday, October 7, 2015

Graduation of the masters students

While up in Portland for some much needed R&R I had the chance to drop by Gary's shop for the graduation of his masters students. My personal favorite piece was a drafting table made by Student Ben Wu. It was a very ingenious design made in Walnut, Sweet Cherry and Hickory. His joinery was well done and the desktop raises to become the drafting surface. The pen rest is held in place with magnets and can be removed if in the way. The legs are an homage to the famous Nakashima cantilevered chair.

Another order done

The oil stains in the driveway add a lot. My shop is really to small to shoot this order inside.

This Order goes to an IPIC dining movie theater in Houston Texas. It was a fun order to fill, I had to design a set of chairs that went with my bar stools and I feel they turned out nicely.
Now on to something else.