This afternoon my friend Jack and I went flying up to York, PA (KTHV) for lunch. Jack is my oldest friend and he is super excited about the RV. While at York, there was a -6A or -7A doing touch and go's in the pattern.
On the way home from the airport, I stopped by Harbor Freight for some goodies. I was about to get a die grinder, but then I realized I had a rotor zip tool at home with a 90 degree attachment. So all I picked up at HFT was some small cut off wheels, a hole cutter and an electric engraver.
Once home, Jack and I went to work deburring the ribs for the empennage. It took a while to get a process down, but using the quick deburr took the the flat edges and some of the curves worked well. The deburr tool for the inside corners works great. It took some time to get a good system down to make sure both the inside and outside edges got deburred with the tool. Then I used the emery paper to smooth down the edges (scotch brite wheels were handy on the bigger burs), then scotch brite pads to finish it up.
I then needed to flute a couple pair of ribs. I found a couple issues with fluting. When I was over Bill Cloughley's house, he told me that when you flute, you want all of the holes to line up. Sounds good, since the holes on the skin that the rib holes line up with are straight. When I did this, the rib didn't lie flat on the table as Van's fluting instructions said. I fiddled with this a while because I wanted a good system down that worked. I used the hand seamer to straighten de-flute when needed. I found that a lot of them ribs had bends on the outside/inside edges (the larger main plane of aluminum in the rib). I needed to make these flat by turning the ribs upside down so the flanges were on the table. Then I lightly tapped it with a mallet until flat. I used the ruler to let me know when it was flat. It took some time, but everything that needed to be fluted was.
On one of the ribs, I accidentally bent the flange outward, with the bend line along the skin hole. I didn't know exactly how bad this was, so I posted a question on the Yahoo RV7and7A group. Here is what I got:
I just got my empennage kit the other day, so bear with me that I am
a new builder. I was doing my first fluting on the HS-708 rib and I
accidentally bowed a flange outward about 20-30 degrees, with the
crease line along where one of the skin holes is, in about the center
of the flange. I was able to bend it back almost perfect, but I am
worried about two things - 1) Is this unnecesary bend outward, then
back in weaking the flange enough to worry? 2) I am not able to get the
flange between the two flutes to be perfectly flat. It is close, but no
cigar. I have used a mallet and seamers to bring it back to as close as
straight as I can manage. Is this slight waving action going to cause
Thanks to all that can offer advice.
- Mike B
Dan C. wrote back right away and let me know what I needed to hear. I wish I would of known this before I started fluting.
Don't worry about the bending. In that one spot on that one small part,
it'll be fine. Just get the flange square (literally use a square to
check), and remember!! ...only flute if the holes don't line up! I think
people look at some of the builder logs online and see fluting being done,
and they think they too need to flute. Not necessarily the case.
Back in the day before pre-punched ribs, you fluted before you drilled. Get
the part straight, then drill it. Fluting straightened the rib so a
centerline running down the flange would show through all of the holes.
Now that things are pre-punched, go ahead and try to cleco it in place right
out of the box. If things aren't lining up, then you start thinking about
fluting. Or just lay a straightedge along the rib flange and see if the
holes are aligned. If they line up, leave 'em alone!
As a tech counselor, I've seen several builders who haven't been diligent
enough about flanging and have over-fluted the parts, and it has caused
problems...flanges pulling away from the skin, rivets not setting properly,
Square the flanges (other than on fuselage bulkheads), flute only where
necessary, re-adjust the flanges if necessary, and now you're good to go
with the drill.
RV-7 N714D (706 hours)
Bill Swaim also had some advice...
This will cause no problem & you will get the feel of the fluting squaring
process very soon!
The fluting allows the web of the rib to be flat and also allows the flange to
be at 90 deg to the web (note for the future that not all flanges are square to
the web, but MUST be parallel to the skin). I cut a small 1 x 2 wood block (90
deg) and screwed it down to my bench. Do some initial seaming to 90 deg & then
flute till web is flat on the bench. Slide the flange up against the block &
work the flange to 90 all the way around using the block as reference. Very
Please note early on in your project, that the skins are flat........If the rib
flanges are not initially at 90 deg to the web (parallel to the skin) you will
fight it & see it in the end result, especially at the end ribs!. Use any
method possible to speed up your prep work (band saw, scotchbrite wheels - large
& small, belt disk sander), but never sacrifice the final quality of each
individual step. Also, I found that a file & diamond sanding pad make quick
work of skin edges, but you will develop your own methods.
As always, just my .02 worth. Hope it helps!
Have fun & Fly Safe!
Slow Build Fuselage
I was working in the drill patterns for the main rib, but I could only figure out how to do the top hole. The bottom hole did not have good instructions on Van's drawings. Maybe it too late, but I am sure if I mull this over tonight it will be obvious tomorrow.
Finally, I had Jack help me with applying a coat of polyeurathane to my workbench. Since I won't do much work tomorrow, and I don't have anything to squeeze rivets with yet, this was a good time to get this coat on before the table go too beat up.
My friend Jack....also known as my fully automatic deburring tool! Just kidding. Jack did a great job deburring all the edges of the ribs. He is super meticulous and he produces nothing but quality!
This is one way I tested my fluting - using the ruler.
All the holes line up. Another passed test that the flute is right on.
This one took me a while to figure out. This part of the rib wasn't always flat. In fact, most had an outward bow which made it difficult to lay flat on the table (the final test I did for my flutes). To fix these, I turned the rib upside down (as shown) and lightly tapped on it with a mallet.
This is the unofficial sponsor of my project. Good old Natty Boh! (Yes, people still drink this)
Jack's first use of clecos.
Not only is Jack a fully automated deburring tool, but he is also a great painter! Putting the polyeurathane on the table gave it an awesome looking finish. I will put on 2 more coats tomorrow to make this bulletproof.
Last Modified: May 18, 2022