Got into the shop for a couple of hours on Friday afternoon. Busy week working around the house and cabin now that the nice weather is here.
First order of business was to finish making the new wing root rib for the 701 wing repair. When I last left the shop, I'd prepared the aluminum rib cutout by placing it into the wood forms. Now it's time to bend! Tools of the day... workbench board, plastic dead-blow hammer and fluting pliers.
Ron has made many wing ribs over the years and has developed some great ideas to make the work easier. One of his ideas is a wooden two-by-four with a channel cut down the middle. This workbench board is screwed to the tabletop and gives a great surface to bend against from many angles.
Next tools needed are a plastic headed deadblow hammer and fluting pliers. The hammer is plastic coated to avoid damaging/scratching the aluminum and the deadblow properties (non bounce) prevent leaving tooling marks.
Fluting pliers are used to slightly crimp the rib edges to take up the extra aluminum that bunches up when corners are bent. Pliers can be bought at a tool supply shop, but Ron prefers to make his own from re-purposed tools.
So lets bend!
Forming aluminum around a form takes equal parts of patience, gentle hammering and finesse. Starting at one end I used the deadblow hammer to start bending the rib flanges over, a little at a time all the way along and back again.
As the flange starts to conform to the curve of the form, fluting pliers are used to "take up" the extra aluminum in strategic locations. This is more of a do as you go type of thing, adding a little crimp here and there. The fluting pliers are just the thing:
One nice thing about the Zenair plans is that they take some of the guesswork out of deciding where to place the crimps. It still takes some experimenting to decide how much is required for each bend.
Once all the flanges are bent, the rib is removed from the forms.
Looks great.... until I laid it on the flat table! That's not right.... hmm...
The cause? Crimping depth wasn't enough. Flipping the rib so the web side is face down and the flanges face up allows one to adjust the crimps slightly, completely flattening out the rib. Perfect!
This was great to practice with and a big step to getting the 701 wing repair complete. I'll have a ton of ribs and other formed parts to bend for my 750.
The next thing I managed to do was finish rivet the fuel bay rib cap repair. Real happy with how good the repair looks:
In the closing moments of the afternoon, I started drilling apart the damaged slat ribs and brackets. I wanted to get these done as they are the next repair up after the main wing.
The title of today's blog entry refers to finesse and a stupid move. I've covered the finesse part with the wing root rib creation. But no day is complete without a stupid move....
While drilling out the rivets on the damaged slat ribs, my smart brain apparently took a coffee break without the rest of my brain knowing. Holding onto one the slat ribs in my left hand and drilling with my right I managed to remove the rivets fairly easily. However, one of the rivets required more pressure on the drill. Well... too much pressure and yup... through the rivet, through the rib and into the palm of my hand.
Ouch! I immediately thought "oh-oh" but considering how much it hurt, there wasn't much needed to stop the bleeding. Two days later, after much consideration about a weekend trip to wait in the understaffed ER, my hand is finally starting to feel better and I'm getting the flexibility back in my index finger. Hopefully no permanent damage. No pictures either, too hard to hold the tablet camera and take the photo with only one hand!
Who knew building could be so much fun!
Where did March go?
Work, family vacation to Florida and a week away from home for a work conference left little time for any shop work. It was difficult to be away so much, but it was a much needed break and I'm making up good shop time again this past week.
Took an hour and started comparing my CAD drawings to the templates already made for the 701. Ron and I had previously sat down and compared drawings and it was a great exercise in determining the commonalities between the two aircraft.
For example, I pulled out Ron's form block for the 701 slat rib and compared it to my CAD drawing for the 750 slat rib form (top right CAD drawing in the picture above). It's a perfect match, which means that is one form I won't have to make for manufacturing my part:
Every form has a matching template for the aluminum that needs to be cut for the specific part (that's the slat rib template CAD drawing directly below the form in the picture above). So somewhere the template already exists for this part, another thing I won't have to create for myself.
On the same track, I pulled a good number of templates and compared them to my plans. Every template has a matching form (where a form is required). What an amazing amount of time and labour this is going to save me:
Next up, I worked towards finishing the fuel tank bay repairs on the 701 wing. As you may recall, I've been working on repairing the spar, rib and channel tops using a "L" doubler. Working inside the nose skin is a challenge!
I made a spar cap doubler repair and test fitted it along side the new spar root doubler:
The only way to get this tight to the existing spar cap is to remove the rivets holding the spar cap to the web. As I indicated, the room to work inside here is really tight and I don't want to remove the nose skin any further than it is and risk creasing the thin aluminum.
Right angle air drill to the rescue!
With the required spar cap rivets removed, I back drilled from the rear of the spar into the new spar cap doubler and clecoed it in place. Another parallel row of rivet holes will be drilled between where the clecos are and the lightening holes of the spar web. This will be very solid when rivetted later:
Finished off fitting and match drilling the rib repair caps as well. Other than some final drilling and riveting, the fuel bay repair is complete and waiting for the new fuel tank.
The next thing to do is replace the root rib with a brand new one. Like a lot of the other repairs needed, it has less to do with being bent from the crash and more to do with poor workmanship by the original builder. Holes that missed centre line, cracks from forgotten de-burring and the like.
Ron and I pulled out the root rib forms. Root ribs are the same length as the wing ribs, but much shallower in height as the wing chord narrows dramatically as it approaches the fuselage.
Forms are what are used to shape flat aluminum into ribs or other structural components. The flanges created by folding the aluminum edges over create rigidity in the part being formed. It starts with matching forms:
Between these, the aluminum that is cut from the matching template is placed:
Before fastening the two forms togther, it's important to check the forms are oriented the correct way. The forms have a beveled edge. This is too allow the aluminum to be bent past the 90 degree mark and spring back to 90 degrees once removed from the form. My first look at the orientation showed I had the forms backwards:
The next important thing is to remember which way the rib flange is to be bent. Often the same parts are bent either left or right, depending on what side of the airplane they are on. It's about symmetry. In this case I have the advantage of looking at the part being replaced and comparing. Then I make a note on the part which way to bend it in case I get sidetracked on something else and button it together with through bolts and wing nuts:
Also needing replaced is the wing root nose rib. The original builder cheaped out and used non standard aluminum and again wasn't very careful with the drill. I found the template for this piece and the form.
Comparing my 750 plans to the 701 plans indicates that this part is identical, so while making the new one for the 701 wing, it made sense to make my two at the same time. My first manufactured parts.... YAY!
So cool to make some parts for MY airplane. Many, many more to come :) Time to go buy some plywood for the remaining forms unique to the 750.
Oh look, my build time log has 1 hour for the wings!
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Husband, father and 911 dispatcher. Long time pilot with a licence that burns a hole in my pocket where my student loan money used to be. First time aircraft builder. Looking to fly my own airplane.