Ch. 8 - Rollover structure - part 1

Making of the steel L braces (4.5 hrs)

One recognizable features of the Long EZ, among many others, is the distinctive rollover-structure/headrest built onto the pilot seat back.

My friend Steve's beautiful Long EZ

Over the years this structure must have proved itself more worthy as a headrest than a roll-over, prompting the publication of this warning...

CP#65 page 7

Some builders with flying aircraft re-engineered this area in order to restore protection in case of an upside down termination of the flight, by incorporating a steel tube roll bar.

Many of those who had not built the headrest yet, omitted the fiberglass structure altogether, and fabricating a pure tubular structure.

Chris' cool bird

Wayne Blacklers' rollbar

Personally, I like the fiberglas structure, and I love the fact that many builders have put it to good use by housing instruments for the passenger’s use. 

This is one lucky GIB (Guy/Girl In Back)

Because I did not want to to take the weight penalty of a steel roll bar, plus the fiberglass structure, I decided to go purely tubular.

My good friend Mike has already given this subject a lot of thought, so I decided to “be like Mike” once again, and borrow as much as possible from his research.

My muse... BizMan!

I could not find a steel L channel of the size and thickness I wanted, but I did find it as a rectangular extrusion (1" x 1.75", 0.065" wall thickness), so I ordered it and cut it to the proper size.

Now, on the subject of cutting...

I need to bring up the very real possibility of setting your workshop on fire, being injured by a exploding grinding wheel used in an unconventional manner, or being cut in half by a flying extrusion, if you were to do as I did.

Do not do what I did!

I replaced my table saw blade with the smallest metal cutting grinder wheel I could find. 

"Spare wheel"

I did this in order to limit the speed at which the cutting edge would engage the metal to be cut, thus reducing the chances of the wheel coming apart. 

Along the same line of thought, I also minimized the amount of blade sticking up above the table to the bare minimum necessary to make the cut. 

I also used all devices available on the saw to maintain a straight cut line, this further reduced the exploding wheel thing, and also reduced the likelihood of "table-saw kick-back". 

Table-saw kick-back in action

Should this happen, and you were to be standing behind the extrusion, you’d be as good as dead. The extrusion would be launched at great velocity toward your chest and stomach area, and go right through you like a hot knife though butter.

No surgeon could stitch you back together after this kind of accident!

Needless to say, I stayed well clear of the kickback area, just in case.

Being a bit anal, I've always vacuumed my table-saw after each use. I do this in order to avoid packing saw dust in places where it could interfere with the proper functioning of the saw. 

This turned out to be a good thing for me as you will see, since the amount of sparks thrown while cutting metal could have easily ignited the dry saw dust. 

How do I know? My wooded table has burn marks from the hot sparks landing on it.

2 foot long 4130 steel extrusion

Trimming it down to 17" (43 cm)

Dangerous longitudinal cut

One more unsafe cut to go, to call it a day.

Voilà, extrusion turned into L channel

Trimming the corners

Top longeron braces done

My friend Mike’s design calls for a top L brace as well as a bottom one, in order to “sandwich” the longeron between steel plates, and make it less likely that the roll bar might be ripped off during a crash. I have not made the bottom channel yet.

The next step was a bit controversial in my mind, since it required cutting a structural bond, but I reasoned that I’d be more than making up for it by using steel cross members.

Cutting through a structural bond (sigh)

One more painful decision was that of reducing the longeron thickness slightly, so that the roll bar could seat flush with it.

Countersunk top longeron

With the slightly wakened structure ready, I was finally ready to try the first parts of the roll bar on for size.

Test fitting the left top brace...

... and the right top one.

All I have to do now is acquire a TIG welder, learn how to use it, get halfway decent with it (or at least passable), then make the rest of the roll bar.

It sounds like another learning opportunity to me!

Stay tuned, this might take a while.