nose rib fluits-

[fairchild]

image_4317.jpgimage_4318.jpgimage_4319.jpgimage_4320.jpg0111082134.jpg Did 2 practice nose ribs now. They seem to look OK generaly- but i am looking at the fluits I made. The "nose" sections of the fluits seem to have a
little distortion where they are near the bend line. Would like to see this zone a little cleaner looking. I will try to post pics up close.
Maybe I have the end of the fluit up too close to the bend line ? should it be back a ways ? like 1/8 back from the tangent of the bend ?

[Bcone1381]

I had the same thing that you are seeing in my nose ribs. Before I got around to remaking them, I aborted the scratch build in favor of a kit.

The nose ribs with the most aggressive curvature are toughest to do. How aggressive is your bend radius? If you skinned those nose ribs, would the rivet that is driven between the flutes distort the leading skin on the nose rib shape so as to make flat spots on the skin? I thought if I did mine over, I would make the flanges bend radius far more gradual hoping it would accommodate the fluting process better. Possibly, fluting pliers with a proud part that has a larger more gentle radius could help.

[Bcone1381]

i didn't see the photos before. Yours look better than mine.

[fairchild]

I have the tip if the "proud part" of my home made pliers kind of a spherical shape at the tip. I have looked at the commercial ones and they have that end more
like a ramp than a ball. Im thinking that having that a ball shape might be making a maximum amount of attempted stretching right there. That might be why Im getting
a little distortion.
I suspect -- that a better way to make the pliers would be to have the lower jaw have a milled out slot---- have the upper jaw just be smooth but fit very paralell to the
lower jaw. In the upper jaw you have a slot cut completely through the upper jaw where the protruding part would be.......
Then you would have the pliers have a 3-rd handle on top that would contain the make pin that forces the sheet metal down into the lower jaw. the idea would be
to try to clamp and trap the sheet metal so it could not move lateraly as the punch is stretching the sheet down into the dish. If you dont immobilize the sheet just
around the nose of the punch--- the stretching will tend to pull the sheet inward as it goes down and in--- and leave some uneven wrinkles there. ( I think)
That might be a pretty hard pair of pliers to make--- and the clamping force would have to be big for it to work. (work better)

I will try to up-load some pics of the ribs some time tonight.......

Tim

[Bcone1381]

I Agree with you regarding the shape of the proud part. Also, making the flange bend radius more generous will help I think. I focused on the recommended minimum bend radius number when doing these, and now feel like a bend radius for these parts that is easier and more gentle would be worth trying. There is alot of built up stress right at the point of the 90 degree bend, and the point of the flute. A larger radius, and tapered flute will give the stress more area and material to act and may ease things up I think.

[fairchild]

I had 2 different pliers I used. Narrow ones on one rib and wider on the other. Both home made. tempted to order the 20$ pair from spruce.......
The ones that look like gas pliers. Did I just get the horseshoe end of the depression too much up into the bend line ? I was thinking of adding an
adjustable stop on the end of the lower jaw to maintain a fixed standoff distance from the bend line.
Tim

By the way---- my bend radius is about 1/8 on the main flange. AC-4313 lists min. BR of 1/16 for .o25 2024-t3/4
It looks like to me that 1/8 radius might be a happy medium between min. and eating up too much flange. should be OK
for the .032 rib to (if I remember right)

I have seen these fluting pliars on the web -- i think RV builders are using them- but I cant seem to find a source----
three fluting pliars.JPG They look well made--- ( was liking the center pair) -dont know if they might be way too deep for ribs..... they might be for bigger parts like fuse. bulkheads (?)
Does anyone have opinions of the cheap (19$) pliers from spruce vs the similar 40$ Avery version ???????
are the avery ones built any better or function better ?????

My first 2 nose ribs were made from unknown alloy--- (no paint ID) --- though it does feel stiff like 2024--- but since no ID marks
it was relegated to testing the form blocks and process.
Note- in my 2-nd rib picture---- I have the end of the flut probably up too close to the bend line-- looks like up in it even-
Im guessing that the part might be happier with the end of the flut just off the bend libe tangent-- so the metal im fluting has
NOT been worked yet--- (might get too hard by double working) - and the round depression going into the bend seems like it
would lead to disturbing the bend line and causing more overall potato chip curve-- in addition to double working and maybe causing a crack
there from too much work hardening.
I notice the Avery pliers have one of jaws sticking out further than the other. I am betting this is to form a "stop" on the inside of the
bend line to prevent you from getting the flut in too close and into the bend line.

Tim