Help please

[Rootster]

I've started forming the flanges on the nose rib lightening holes, not going well, the ribs seem to warp and curl really bad, especially around the smaller hole at the leading edge. I've used a bob-stick tweak the flange, it helps a bit, but I still can't get all of the warping out. Any suggestions as to what may help or what I'm doing wrong? using an MDF form and hammering a tapered plug to form the flanges.

[ScottS]

What I found worked for me was to lay the rib down on a flat surface and slowly bend the flange up, only in the high areas. I found that once the rib got to out of wack it was very difficult to bring it back in shape There is a few videos on this forum that were really helpful for me. Scott

[Frank]

My LSA ribs are "done" and ready for assembly, as far as I know. Never really figured out the zen of managing the warp, but in the moment, I found "methods" of sorts. You're trying to figure out "if I bend it here will it straighten out there". A few Bob sticks are needed because even hardwood gets chewed up. A hard plastic material, like a thick cutting board, might be used to cut out Bob sticks which hold up better. Like Scott said, sometimes the warp goes from bad to worse as you try to make corrections. There may be a reject in the mix. Glad I made extras from the star, but still had to back to scratch for a couple.

What I learned from the aileron ribs: the assembly process takes care of the warps for you (within reason). You get your rib "done" and ready for assembly. Fasten rib to attach angle (which does some straightening right there). Mark and drill the holes in the skin. Draw a line down the center of the rib flange. Muscle that line into place under the hole in the skin. Match drill, fasten, and bingo the rib is straightened. It has no choice.

Your photos don't look bad to me at all. But then what do I know?

[davzLSA]

You need to flute the ribs, it will take the warping out. When you put the flutes in be sure you dont put them where you plan to drill holes for the skin attachment.

[geraldmorrissey]

Some more pictures would help. The chordwise curl might be eliminated by deepening the flutes on the flanges. The waterline curl as said by ScottS, clamp it down and work the flange angle and tap with a radiused aluminum bar around the radius where the hole flanges meet the rib web. Don't be afraid to scrap a couple of ribs to find out how to shrink and expand the metal. Experiment and write down a few pertinent notes. Above all be methodical, your learning a new skill. Take the scrap and nail it up on the shop wall with pride. Try to avoid installing warped parts, it will preload the assembly. Usually not a good idea. Volumes have been written on this very subject, do your research.
Good luck and let us know how it comes out.

[sjt]

https://www.youtube.com/watch?v=jqNoVAQLo0M

https://www.youtube.com/watch?v=pIvFpVV6kIQ

b-spot is a youtube channel you should watch:

https://www.youtube.com/watch?v=F_4i68Itknw

Many people use this method
There are many youtube videos demonstrating technique.

Coming out of form block they look like this
one.jpg

You will also need this kind of tool for making 90 degree edges.

Hint: make the lever 2 feet long.

a.jpg

[sjt]

My top cover mdf held blanks down. It was angled a bit so I could get a better strike with plastic mallet.

My 1 inch two sided mdf included markings where rivets would eventually go so that I could give small flutes to start process.


The first rib takes about 20 hours.(I am not kidding) Once you figure out the technique in the above youtube video the process of making a rib is more like 15 minutes.


3.jpg

[sjt]

The above methods just require a little technique like shown in the video.

If you are as crazy you will make some unnecessary and completely ridiculous tooling like this:


9.jpg

I was into Blacksmithing at the time and wanted to use my forge to make something

10.jpg

[sjt]

The unnecessary and completely ridiculous method does not require any technique. You can have your pet chimp do it.

You have to scallop out the area where the flutes will go.

b.jpg




Then you put it in a press to hold partially formed rib in place.

Then take a wood dowel and give a smack thru each hole into the scalloped out area of the blank. This method generates the correct depth of scallop at each flute.
It is not the depth of the mdf scallop, it is an artifact of holding the edge at a hard 90 and taking up what ever excess material is required at that point.


The advantage is that you do not have to do any thinking.
The disadvantage is that it takes 40 hours to make the tooling that will only be used one time.

Just do the youtube video method it is quicker.



c.jpg

[Sir Newton]

Nice work on the forming jigs. I did all my ribs the old fashioned way. 450 hours from flat material to finished straightened ready to use main, nose, flap & aileron ribs.

[sjt]

The only part of the process I did not like was acid alodine and priming.