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 Sailplane Construction Project Session #100

Comet Sailplane Project
I started laying out the wing's left tip panel last Wednesday afternoon and finally finished the lay up this afternoon because of a few problems I encountered. While the laser cut parts and wood are outstanding, a few of the parts did not fit the plans. However, this is not to say that most of the parts fit very well. The reason for the misfits are because the Sailplane plans already existed so there was no CAD file available for generating the laser parts cut file (I think I am saying this right).
First of all, the w1, w2, and w3 tip parts all needed a little modification to fit the wing tip contour. This was accomplished by gluing on extra wood taken from the same sheet the part was cut from as shown below.
Then the extra wood on the parts was trimmed and sanded to shape so that when the three parts were glued together they fit the wing tip contour as shown below.
The four tapered 3/16" spars for the left wing tip were removed from their sheet and lightly sanded to remove the laser burn. Then they were trimmed and beveled on the ends and fit the plan exactly as shown below.
The 1/8" X 1/2" and 3/16" X 5/8" leading edge pieces were cut a little over length and soaked in warm water. Aliphatic glue was applied between the two damp leading edge pieces and the excess glue wiped off. Then the leading edge pieces were bent to shape and pinned down using a number of short blocks over the wax paper covered wing tip plan as shown below. The leading edge is only slightly bowed, however the combined 5/16" laminated leading edge requires some serious blocking up to get it bent to shape. Once dry, the curve in the laminated leading edge will permanent.
Then a problem with the sub ribs were found as shown below. The No. 15 sub rib was a repeat of the No. 14, the 17A sub rib was a repeat of No. 16, and the No. 18A sub rib was actually No. 17.
What this meant was that there was no No. 15 or No. 18 sub ribs. In order to make a suitable pattern for each of these, the forward shape of the full ribs on either side of the missing sub rib was traced on a common piece of paper. The pattern was developed by drawing a line between the two rib tracings and then the two missing sub ribs were cut out as shown below.
The bowed leading edge was trimmed to fit the notch in the w1 tip piece and the assembled trailing edge, including the tip, was glued to the leading edge. Then each of the six full rib was glued in place between the leading and trailing edges, being sure that each rib was perpendicular to the work table surface. Again, these laser cut ribs fit extremely well, except the last tip rib, which was too short and not shaped correctly. 
There were several iterations of custom trimming and tweaking of the rib cut outs required to get each of the four tapered spars to slide straight through the cut outs in the all of the ribs. However, with a little patience and persistence this was accomplished. Finally five of the six sub ribs were glued in place as shown below. Oh yes, 3/32" gussets were added to the end of the ribs to help stabilize and hold the wide trailing edge in place. 
In the picture below you can see that soft filler wood is going to have to be added to the top of the tip pieces where the leading edge attaches to the tip. Notice also that the second spar from the front is partially elevated relative to the tip pieces. So soft filler wood will have to be added around the tip in order to get the wing tip sculptured properly. Once this is completed, the last sub rib will be glued in place. I think this structure is going to make a beautiful wing once I work through all of the hidden challenges. :O)..........................Tandy   

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