Sunday, October 21, 2012

Wing Ribs Deburred – On To Fluting

Three 1”Scotch-brite wheels later and after spending far more time deburring than it would seem it should take to accomplish the task, all the wing ribs are finally deburred. Admittedly, I probably spent far more time than necessary … after all, when you really get down to it, the only places on the ribs that really need to be perfectly smooth are the edges where the skins touch the ribs and where the ribs attach to the spars. Hands will not be going into the lightening holes to rivet as is necessary in with other RV models, so they don’t really need to be perfectly smooth either. All that said, I just couldn’t make myself ignore a rough surface so deburring the ribs turned into a time sucking abyss while I was in overkill mode.

The last batch of ribs deburred were W-1210 L&R. At first glance, they appeared much smoother than the W-1208 L&R ribs that had the numerous jagged edges mentioned in a previous post … so I was hopeful of finishing them quickly. However that was not to be because they had their own unique problem. Although they did not have nearly as many jagged edges as the W-1208 L&R ribs, there were sharp raised edges where the metal was sheared, particularly where there were tabs on the ribs. As such, they required a lot of hand filing with the diamond needle files to remove all the raised edges.

Because the W-1210 L&R ribs were the last ribs to be deburred, the fluting process began with them. Interestingly, they are not nearly as warped as the W-1208 ribs which is making the fluting process go quickly … after spending a minute or two squaring all the flanges on each rib, the fluting is taking around 10 minutes per rib so there will be a few more hours of fluting left after today.
                                                              The typical bow of a W-1210 rib prior to fluting.

I’m fluting using a method I saw in a YouTube video made by Allan Gilmore and it is working rather well thus far. Basically, the rib is marked at 2” intervals which equates to every other rivet hole. A mark is made on the bench 2” from the edge.
                               One of the RV-12's W-1210 ribs marked every 2” for fluting. Note the blue tape
                               on the bench with the line on it … the line is 2” from the edge of the bench.

Allan Gilmore’s fluting process begins with placing the rib’s first 2” spacing mark on top of the 2” mark on the bench. The rib is pressed down flat to the bench between the edge of the work bench and the 2” mark which means it is being pressed flat BEHIND the 2” mark on the rib. The rib is then squeezed with the fluting pliers at the location where the mark is until the edge of the rib begins lifting off the bench. Relaxing the pressure on the fluting pliers should result in the rib’s edge laying flat on the bench. If the edge remains raised off the bench, use a pair of flat pliers to flatten the flute a little until the edge lays flat on the bench again. The flute is close to perfect when the slightest pressure applied to the fluting pliers begins to lift the rib’s edge off the bench and when the pressure is relaxed, the rib lies flat again …. once that is accomplished, slide the next 2” mark on the rib over the mark on the tape and press down on the rib BEHIND the 2” mark and repeat the process. Once all locations with marks on the ribs have been fluted, the rib should be flat on that side with all the flange holes in alignment. Repeat the process for the other side.
                         Fluting the rib at the first 2” mark on the rib while watching the end of the rib begin too rise.

After both sides were fluted, some ribs have required a slight tweaking. On some I made shallow flutes between the marks to bring things into better alignment.
                                               The edge of a W-1210 rib after fluting … almost perfectly flat.

It will be interesting to see how well this fluting method will work on the W-1208 ribs because they have quite a bit more curve in them because of their shape. Guess I’ll find out tomorrow.