Spars in CMAD Planes
Just a note of caution. Any of the CMAD QM-40 planes with 2 piece wings use a 5/8 diameter pultruded Carbon spar. The supplier says they have very low Hoop Strength. This means that if dropped or crushed on the ends they can crack pretty easily. I started out sending balsa plugs to fill them with and for some reason in the interest of shipping sooner than later they did not get included with the kits.
Please plug the ends of your spars with either soft balsa end grain cut to fit with a sharpened piece of 7/16″ brass tubing sharpened to cut. 3/4 to 1″ long. glue in with medium CA and saturate the end with thin ca. This will solve the issue. You can also use a piece of hardwood dowel but install with epoxy.
Sorry for not following up with this sooner.
These are very strong spars but do have a week point. This is the solution.