Gentlemen while putting my leading edge skins on and drilling the holes through the skin into the ribs, drilling the holes in one side and using the ratchet straps and 2 x 4 to pull the other edge down to the spar I decided to remove the skin to see if I was getting any marks. When doing the forward ribs I did try to round and smooth the edges to help with the marks that others have had problems with.
There is a “trick” where you drill a hole in the bend of the flange near the nose of the forward ribs (maybe an inch or so back from the nose end), then cut the flange bend (you don’t cut the flange off completely) back to that hole. Be sure to clean it all up so that there are no stress risers, and keep the end of the cut nice and rounded (hence the reason for drilling a hole). The idea is that the end of the flange can bend in a bit more, and the nose of the ribs can be rounded off some more as needed and will not put the little dimples in the nose of the leading edge skins.
Maybe someone will have photos as I don’t think my description is very clear.
That’s what I did, based on what John M showed us during the shop visit many years ago. It works very well, but be careful not to take the ‘notch’ back too far as I did on a few ribs (second photo). This will affect the edge distance on the forward rivet hole. I had to add a second rivet (on Kerry’s/Sonex tech advice).
When tipping a flange on a convex curve there is more material outside the bend than at the bend. That material has to be accomodated. In this instance, this is achieved by fluting. If the fluting is insufficient to accomodate the now extra material, the edge will get wavy and or the part will develope a bend along the longitudinal axis. . The area circuled in yellow appears to show a disortion/wavyness, suggesting missing or under developed fluting. Place the rib with the flanges facing up on a table, if it forms an arch, add fluting, if you can rock it back and forth, reduce the fluting, if the flange angles out, increase the fluting, If it angles in, reduce (i.e. patially flatten) the fluting. No need for extra hole, rivets cut etc.
Thanks for the ideas.
John I see what you are talking about, the flute is as it came from the factory and before I attached it to the spar the ribs all laid flat on a table.
Kevin and al_lizon thanks for your suggestion and photos. I appreciate the help.
My ribs came from the factory (or maybe the previous owner) with the treatment that @Kevin_Conklin and @al_lizon mentioned. I still needed to trim a little bit back to avoid the dents you mentioned:
Thanks for all the help everyone. I did reach out to Sonex and they gave the approval that this is the correct method to help with preventing dings in the skin.
