Saturday, October 6, 2012

Sparring With The Spar

As mentioned in a previous post, the spars are long and the weight is not evenly distributed because the spar keeps getting thicker and thicker towards the inboard end.  Add to that the RV-12 spar extends to the far opposite side of the fuselage which means there is a lot of metal extending beyond the area of the wing that is skinned, I’m guessing around 43” or so. After bringing the left spar out of the shipping crate, I quickly realized the inboard end of the spar would require more support than I had planned on. As a result, thought it best to move the big square wing crate yet again, and push the assembly workbench further back so a portion of the spar would extend slightly into the shed. A sling was made to offer support to the end of the spar which will help stabilize the spar on the workbench.

                           Left spar on the workbench with the heavy inboard end in a sling to help hold the weight.

Didn’t proceed with any assembly today because of a late afternoon start due to family commitments … but after sparing with the spar I wasn’t motivated enough to be drilling holes. I think the spar won today’s session but it will be drilled and tapped into submission tomorrow.

One of the first steps in the plans calls for the drilling and taping of the AEX tie down extrusion. Interestingly, the plans call for tapping both ends (meaning upper and lower wing sides) and the drawing shows the left and right spar sharing a detail calling for drilling and tapping both ends of the AEX extrusion. I questioned that … as logic would dictate, only the lower portion of the wing needs a tie down ring. I called Van’s for clarification and was told yes, the tie down is really only needed on the bottom side of the wing. However, because of the removable nature of the RV-12’s wings, Van’s has offered the builder the ability to secure both sides of the wing for trailer transport. The upper wing skin has a small hole above the AEX tie down so it can be drilled out to accommodate a tie down ring should the need arise.
                                                         AEX tie down extrusion before drilling and tapping.

Guess I will go ahead with drilling and taping both ends of the AEX extrusion even though there are no plans to have the RV-12 as a trailer stored aircraft. I’ll just place a pop rivet in the small hole in the upper wing skin and should I need a tie down on the upper side of the wing, will only need to drill out a rivet and enlarge the hole in the skin a bit.