Now that the glue has had a chance to dry, we can work on the leading edge, the top main spar, and the rear main spar.

As we get ready to put the main and rear spar in place we need to take a minute and take a look at how the parts fit together. This goes back to discussion on the shears webs, and also what I talked about with gaps. Any gaps between parts will make a weak joint, and since the shear web gives our wing strength we want to install the top spars so there is no gap between the top of the shear web and bottom of the spar.

If you look at picture # 1 you can see the the top of the shear web sits lower than the notch in the rib, this will result in a weak joint when we put the spar in place. To correct this we need to take a little bit of wood from the bottom of the notch in the rib. Picture # 2 shows using an X-acto knife to carve off the wood. Just like everything else, do a little bit at a time. Picture #3 shows another great tool that will come in handy in a lot of places. It's a nail file that you can pick up in the beauty department at Wal-mart, picture #4 shows using the file to file down the notch level with the top of the shear web. Picture #5 shows the notch even with the shear web now, and a test fit of the spar in picture #6 shows that we have a good tight fit between the spar and the shear web. This is exactly what we are trying to get, this will give you very strong joint. At this point don't worry if they don't match up exactly, as a little difference can be taken care of with some sanding later. Please note in picture #7 the 3 inner ribs do not extend all the way to the top of the spar. This is because there will be sheeting installed on top of these ribs. For now we need to focus on the joint between the spars and the shear web. Picture # 8 shows the test fit of the top main spar, and #9 shows a test fit of the top rear spar.

The instructions tell us to compare the leading edge to the cross section on the plans to see the proper alignment of the leading edge. If you look at picture #10 you will notice that the leading edge is not a symmetrical piece, so it's important that you get the proper alignment for this part. I've marked the part with an arrow in order to show which way is up. Picture #11 shows a test fit of the leading edge.


Pictures
1. Difference between the top of the shear webbing and the bottom of the spar notch in the ribs.
2. Using an X-acto knife to remove wood from the notch.
3. Cheap nail file can be found at Wal-mart.
4. Using the file to sand the notch in the rib
5. Bottom of the notch now is even with the top of the shear web.
6. Test fit of the spar shows a tight fit between the shear web and the spar.
7. First 3 ribs sit lower than the top of the spar. This is to install sheeting.
8. Test fit of the top main spar.
9. Test fit of the top rear spar.
10. Marking the leading edge with the proper alignment
11. Test fitting the leading edge.


Until next time

Ken