April 28, 2012

The Sonex drawings call out for seven pieces of “Cross Tie” stock to be made. Three pieces tie the top edges of the, “left” and “right” sides, of the fuselage together, and three pieces tie the bottom edges, of the fuselage sides, together. An eighth piece of “Cross Tie” stock is needed, but it is fabricated out of “Channel Stock”. This piece has different dimensions called out for then the “Cross Tie” stock.

The “Cross Tie” stock can be found on the “Basic Shapes” drawing page, SNX – Z04.

This is what the “Cross Tie” stock looks like in a profile view.

Here is the “Cut List” for the seven pieces of “Cross Tie” stock.

Once these lengths of “Cross Tie” stock are cut, I am supposed to head to drawing page, SNX – F24. The “F” designates that the parts are going to be used in the construction of the Fuselage. Drawing “F24” will layout for me what I need to do with the rough cut, “Cross Tie” stock pieces.

Here is the “Information Block” of the drawing page, SNX – F24.

On the “F24” page, specifics as to what needs to be done to the “Cross Tie” stock are given. Of interest to me, is one particular dimension called for in the drawings. Three of the “Upper Cross Tie” pieces are to have flanges, (1½” wide and ¾” wide.), as called for in the “Basic Shapes” drawing, SNX – Z04. The remaining four, “Lower Cross Tie” pieces are to have flanges of equal widths; ¾” and ¾”.

That would mean, I would have to cut material for the “Lower Cross Tie” pieces, (as per drawing SNX – 04), and then re-cut the pieces as called for on drawing, SNX – F24.

Here are a couple of photographs to illustrate better what I am trying to communicate.

In the photograph below, it shows the “Upper Cross Ties” with the 1½” wide and ¾” wide flanges.

In the next photograph, the “Lower Cross Ties” requirements are called out on the drawing.

Then, there is the detail of trimming the 1½” wide flange back to a ¾” dimension.

The same trimming job is true for the lone “Cross Tie” located aft, in the Tail Cone area.

I decided that I only wanted to measure once, and cut once! I prepared a length long enough to get the “Upper Cross Ties” out of, and then a length long enough to get the “Lower Cross Ties” out of. This way, there was no re-trimming of the “Lower Cross Tie” stock flange.

What follows is what the process was like for me to fabricate the “Lower Cross Ties”.

This piece of aluminum is left over scrap from “Sheet 10”.

I laid out my measurements for the bend tangent lines…..

….then I cut the “Lower Cross Tie” blank off of the larger sheet.

I used a 10” Vixen file, (A MUST for construction of a sheet aluminum airplane!), to fair my cut line smooth, and to my measured line.

With the “Cross Tie” blank cut out, and faired to specification, I clamped it into position on my sheet metal bending brake.

Next, I positioned the Pinch Bar into position……

…and clamped it into place.

I lifted the handle of the bending leaf to begin the bending process.

I discovered that I need a “helper bar” to gain more leverage for making bends. This is just a piece of 2” wide, by 1/8″ thick steel stock. I have covered one face with masking tape to protect the aluminum against unnecessary scratches. (I also covered the bed of the brake, and the bending leaf with masking tape as well.)

The “helper bar” is placed between the bending leaf and the work piece.

Now, I continued to bend the flange of the “Cross tie”. In the photographs below, I am shooting for a 5 degree deflection from 90 degrees; or an 85 degree bend.

After making the bend, I unclamped the Pinch Bar, and removed the work piece to check it.

Now, for the opposite side.

I positioned the work piece and Pinch Bar……

….and clamped them together.

Then, I made my second bend.

I checked my measurements.

Ninety degree flange.

And, a 2 63/64” width. (Honestly, I was lucky to get this!)

Finally, I referred to the Cut List, and measured out the lengths of “Lower Cross Tie” stock that I needed.

Using a pair of “Andy Snips”, I cut the flanges up to the web section…..

…then, scored the web section several times with a scoring tool.

I then, bent the “Cross Tie” piece along the scored line……

…to snap the piece in two.

I marked each piece as to what it was, according to the plans, and also its length measurement.

I will continue to fabricate all of the “Basic Shapes” in this fashion.

Putting the whole process together, and in motion, this is what my workflow looks like on video.

April 22, 2012

In my final bending practice project, I wanted to see if I could fabricate some “Basic Shape” parts, that were the actual dimensions called out for on the Sonex drawings.

Instead of using 6061-T6 aluminum, I chose to practice with the same scrap sheet steel that I used for fabricating my camera bracket, and my metal boxes.

I decided to tackle trying to replicate the, “ – 04 Channel Stock”, that is located on drawing page, SNX – Z02 “Basic Shapes”.

Here are the dimensions of that part.

Various lengths of this part are needed in fabricating the Sonex. I wasn’t concerned with that. I just wanted to see if I could bend a few channel pieces that had the dimensions called out in the above photograph.

I laid out the necessary measurements, cut the blank out, and deburred it.

I bent the first flange…..

…then the second flange.

Here is a finished length of -04 Channel.

Everything went very smoothly up to this point. Now came the REAL test! What was the measured width of the channel going to be?

EXACTLY what the plans call for!

But, I know it was beginner’s luck! So, I cut out and bent two more -04 Channel pieces. I wanted to compare all three channel width measurements, with my skill, at how to set everything up on my bending brake.

I tried to do everything exactly the same way as my first, “lucky”, channel piece.

Here is the measured width of my third attempt.

All three channels measured within 1/32” of each other. I felt that was “Good Enough”!

I feel that I am now ready to return to fabricating actual parts for my Sonex airplane!

April 22, 2012

The two goals for my next “bending practice” project were to; make something useful for my workshop, and to focus on hitting my measurements accurately with my developing bending brake skills.

I decided to fabricate a couple of sheet metal boxes. The idea behind making them was to have something to store Cleco clamps, or rivets in.

I laid out some measurements on to one of the pieces of sheet metal, that I dragged out of a dumpster, where I work.

Using a pair of snips, I made cuts in the sheet metal that would allow me to bend a box shape.

I did not want a raw, sharp edge along the top of my finished boxes. I needed to fold over the top edge.

Here is the piece of sheet metal, clamped into my bending brake, ready to make a “top edge” bend.

Making the bend.

Using a mallet to tap over the flange.

Here is the working blank, with all “top” edges folded over.

Now, I can begin to bend the actual sides of the box.

It really doesn’t matter what I use for a pinch bar! Because I can do this, I guess I can say that, technically I have built more then just a sheet metal bending brake. I actually have a “Box and Pan brake”!

Here is the roughed out box.

In a previous practice session, I had bent some 1” x 1” angle out of the sheet steel. I cut four “legs” for my metal box.

I drilled, and riveted the legs to the box. The legs and rivets hold the sides of the box together.

I know that it is going to take practice, practice, practice to develop the skills that I need to bend parts for my Sonex, using my homebuilt bending brake.

So……..

……I laid out measurements for second sheet metal box.

And, fabricated a “mate” for the first box!