April 05, 2012
The last five pages of the Sonex plans packet are labeled, “Basic Shapes”. Each page has a group of drawings on it, that refer to specific formed, aluminum shapes, that are used in different locations of the aircraft while building it. The typical shapes called for are; “channel” stock; “angle” stock; “flap” stock; and “aileron” stock.
Below are a couple of photographs, that will give a reader an idea of what the, “Basic Shapes”, drawing identification block looks like.
Here are a few photographs that give a reader an idea of what kind of shapes I am referring to.
Each “Basic Shape” drawing, also has a “Cut List”, of the given shape, printed right next to it.
For example, the Cut List for the 1” x 1” angle listed above, looks like this:
The Cut List for the “-04” .025” Channel Stock looks like this:
Here is the Cut List for the “-02” .032” Rear Spar Channel Stock:
Each Cut List, will tell a builder how much is needed of each Basic Shape, and where that length will be used during the airplane’s construction. Each Basic Shape piece has a length measurement, a quantity amount, and a “drawing destination” listed next to it, within each Cut List.
Take a closer look at the Cut List for the .025” Channel Stock; particularly down towards the bottom of the list. There is a length listed of, 77” long.
Now, take a look at the Cut List for the .032” Rear Spar Channel Stock. You will see listed, two 96” long pieces that are needed.
The question I had was, “How am I going to make all of these Basic Shapes?” I fiddled around with a few ideas of my own, to get a “feel” for what it was like to bend aluminum into these shapes. I also studied videos on online, and looked at some ideas other builders have come up with to deal with this situation.
The shorter lengths of stock, could be bent using a sheet metal bending brake; either purchased, borrowed, or home-built. Ultimately though, the three long lengths of channel stock, (77” long, and the two pieces at, 96”long), had to be dealt with at some point. That meant finding a way to accomplish this task.
I have been told that a contractor’s aluminum siding, bending brake, does not have the strength to handle bending, .032” thick 6061-T6 aluminum. That is unfortunate because, that piece of equipment is usually manufactured in a 10’6” length. Which, would be perfect for the Sonex! And often, used siding brakes can be found for sale, or rented from a siding contractor.
There are a couple of “home-built” bending brake designs, that are popular with scratch airplane builders. The price for the material runs about $75, so the cost IS fairly “cheap”! One of those popular home-built bending brakes, incorporates the use of a workbench. The bending brake is mounted along the edge of a builder’s workbench. Although this bending brake design is effective, efficient, and inexpensive to fabricate, I chose not to build one for the reason that it WAS mounted to the edge of a workbench.
I made the decision that I wanted a standalone bending brake. I wanted a sheet metal bending brake that could stand by itself, and would not be a part of my workbench. I also wanted a sheet metal bending brake that was long enough to tackle the longest bends needed for building the Sonex. I wanted to be able to use it anytime that I wanted to, (I didn’t want to borrow a bending brake, or rent one). And, I wanted to be able to bend material that was much thicker then the .032” aluminum; being able to use the bending brake for future projects. Finally, I wanted my bending brake to be designed and fabricated, so that I could dismantle it, and store it away if I wanted to.
What follows, is a journal of photographs, and written text, that will walk a reader through how I made my own bending brake. Its design is based on my “wants” that I listed in the previous paragraph. And, I will tell the reader right up front that, the materials to build my brake cost nearly $500. So, it isn’t cheap! But, it DOES do all that I set out to make it do!
Here are the sketches, of my bending brake design, scribbled out on my “idea pad”. I am not much of an engineer! Nor, an artist! But, this is all that I worked from to build, “The Beast”.
I borrowed a pickup truck from a good friend of mine, and drove to, Bangor Steel, located in, Bangor, Maine.
I had phoned in advance of my arrival, and ordered the material that I wanted. I do not know much about steel. I did some online research. Using the web as my resource, I studied different profiles, and sizes of the material, to inspire the sketches illustrated above, and to arrive at a materials list.
Here are two photographs of the interior warehouses of Bangor Steel.
Here is the bill that I paid. The total was $361.45.
I loaded up the pickup truck and drove home.
And, I unloaded the steel on to my garage floor.
The 4” wide channel stock was going to be used for; feet, legs, stretcher, bed support, and bed. Those pieces were the first for me to cut up to size, so I organized the channel stock on my workbench.
Using my 4” grinder, with a metal “cut-off” wheel tightened on to the arbor, I began whittling my way through the channel stock; cutting the lengths that I needed for my bending brake.
Below is a photograph of all of the parts that make up the supporting structure of my brake.
And, here is a photograph of my supervisor. His name is, “Reuben”. He is an 8 year old Black Lab; 103lbs and with only three legs!
As I previously mentioned, I wanted to be able to dismantle my bending brake. To be able to do so, I had to bolt it together so that I could unbolt it later if necessary. Below, are several images that illustrate me drilling and bolting various parts of the brake together.
Here, a reader should get the basic idea of my design now.
Under the ever watchful eye of my supervisor…….
The next series of photographs will show me drilling and fastening, what I call the “bed” of the brake to the supporting structure.
Here, I am countersinking for the head of the bolts, that will be used to fasten the bed to the structure.
Tightening up the “bed bolts”.
Here I have laid out the 18 hinges that I used to attach the bending leaf to the bed of the brake.
Before using the hinges, I had to drill one new hole, on one leaf of each hinge, so that it would “catch” the edge of the bed.
The hinges that I chose to use are for woodworking. They are designed to be mortised into the edge of a passageway, or entryway door, and also into its related doorjamb.
I am NOT mortising steel! So consequently, I had to cut up some 1/8” thick steel shims; 36 of them to be exact!
A pile of hinges, and a pile of shims, ready to be pressed into service.
My strategy here was to mount the 18 hinges, (with matching shims), to the bending leaf first. The bending leaf is a piece of steel that is 6” wide, by 3/8” thick, by 8’ 6” long. Incidentally, 8’ 6” is the intended working length of my brake.
The hinges were mounted to the bending leaf by, locating the hinges, (proper spacing between each one), marking where the holes were to be drilled, threading each drilled hole with a 10:24 tap, then fastening the shim and hinge with 10:24, flat head machine screws.
All of the hinges mounted to the bending leaf.
In the photograph below, a reader will see the bending leaf clamped to the bed. I stuck a piece of masking tape to the edge of the bed. I did this so that I could better see the marks that I had to transfer from the hinges, mounted on the bending leaf, to where I needed to drill, and tap their mating holes, for the other leaf of the hinge, into the bed.
As I moved along through this process, I would unfasten the hinge from the bending leaf, and fasten it to the bed.
Here are all of the hinges now mounted to the bed. The shims for the bending leaf side of the hinges, are lined up on the floor.
Using C-clamps and a couple of buckets, I supported the bending leaf, right next to the bed, and fastened the bending leaf to the bed, using the hinges I had previously fastened to it.
And, here it is! It should start making sense now. I hope!
This is what the extent of the bending action looks like. I had planned to bolt a piece of 1” by 1” angle iron to the top edge of the bending leaf, to give it more leverage and surface area.
At this angle, the bending leaf is “hinge binding” against the bed. I knew that it would, but I had hoped that I would get more swing of the leaf, before it bound up.
I decided to “nip off” the inboard corner of the bending leaf, to give it a little more swing. I did that using my Circular Saw with a metal cutting blade tightened to the saw’s arbor.
In the next three photos, I am drilling, tapping and bolting a piece of 1” by 1” angle iron to the top edge of the bending leaf.
After that task was complete, I was dying to see if my contraption would work! I am holding in my hand, a piece of galvanized steel. It is thicker and stiffer then the aluminum I need to bend. I had quickly cobbled together a pinch bar with a 1/8” radius along one edge. I used C-clamps to “trap” the piece of sheet steel between the bed, and the pinch bar. I was excited by the results!
Now, it was time to make a proper handle for the bending leaf. I happened to have a length of black iron pipe left over from when I fabricated my buffing / grinding station. It looked like the perfect solution for the job!
I own a Harbor Freight, hydraulic pipe bender. I had purchased it used a couple of years ago, so that I could fabricate my own set of crashbars for my adventure motorcycle.
After I got the handle made up, I needed to “cope it” into the face of the leaf to that I could bolt it to the leaf. I used my woodworking skills and my grinder again to do that.
Not bad, eh?
I then drilled and tapped the necessary holes that I needed for bolting the handle to the bending leaf.
Next I needed a centerpost for the handle. One end of the centerpost needed to be notched to the radius of the handle, (called a “bird’s mouth”), and the other end needed to be notched, like the ends of the handle were, to fit to the bending leaf.
I used a holesaw to cut the “bird’s mouth” into one end of the handle’s centerpost.
I was kind of proud of this. One cut and a perfect fit!
Here I am marking out where the notch needs to be in the other end of the centerpost.
And, cutting that notch.
Then, drilling, tapping, and bolting the centerpost to the bending leaf.
By this time, I had used nearly every tool in my shop, except one. So, I broke out my Oxy/Acy torch set, and welded the centerpost to the handle.
Now, it’s looking like something!
At this point, I decided to make another test bend. The material that I chose to use this time was, a piece of 1/32” thick stainless steel. Again, I used my temporary pinch bar, with an 1/8” radius along one edge.
The final part, that I needed to fabricate for my bending brake, is the “pinch bar”. Because there is more room, and better quality tools available, at the boatyard where I work, I headed off there for the next phase of construction.
The photograph below shows me ripping a piece of ½” Corian on a tablesaw.
On one edge of the Corian, I routed a 1/8” radius, and on the other, I routed a 1/16” radius.
After the routing was done, I headed back to the tablesaw, and I “back cut” the Corian, at a 30 degree bevel; “sloping” away from each radius.
In the photograph below, there are three short sections of scrap angle iron, “nested” together, sitting on top of the Corian platen. The two bottom pieces will be 8′ 6″ long. The middle piece will be short sections, (“gussets”), that will be welded to the other two, longer pieces of angle iron. (This will make more sense to a reader, shortly!).
I packed up the Corian pinch bar platen, and headed back to my garage.
In the photograph below, I am cutting angle iron gussets, that will be welded to the pinch bar backing structure.
All of the gussets cut to length.
Here I am laying out the spacing for the gussets.
And, here I am welding the gussets to the pinch bar structure.
All of the gussets welded in place.
Moving over to my workbench, I slid the Corian platen underneath the pinch bar structure. I needed to bolt the Corian platen to the steel pinch bar.
Here I am bolting the Corian platen to the pinch bar.
Finally, it was time to give “The Beast” a test!
I laid out a ½” “flange line” on a piece of sheet steel.
Using C-Clamps, I “pinched” the piece of steel to the bed of the bending brake.
I lifted the handle……..
For my first, “calculated” bend, I was shooting for ½”. I ended up at 33/64”. I don’t think that is too bad!
To complete this project, I wanted to cut the pinch bar into two pieces. Adding to my list of “wants”, I decided to cut the pinch bar into a 3’ 3” long piece, and a 5’ 3” long piece. The two shorter sections will be easier to handle. When I need a longer bend, (77” and 96”), I can butt them together.
And finally, I added a diagonal support, from each leg, to each foot.
Here is my finished, sheet metal bending brake.
My next step is to, begin making some practice bends, on some scrap metal I have here, to teach myself how to use my new brake.
That story will follow soon!