It shouldn't really apply to any scratch built projects with freshly cut cores but it serves to mention, for others who may have GP kits, that I had a manufacturing problem with my first set of cores:

The root airfoil templates were dislodged (in all likelihood) on passing the bow through the foam. This seems to have been a systematic problem (probably the first few runs) as the exact same error is introduced in each core. The LE expands in thickness toward the root (last couple of inches) and since the core panels are all cut single sided, one ends up with a LE which is overly thick on the top of one panel and on the bottom of the other. This leads to unequal incidences in the panels when joined.

In order to correct for this, I had to sand out the excess thickness in each panel leaving me with even thickness LE's. I'll have to check but hopefully the roots will now bond squarely while producing equal incidences.

The second set of cores, produced 5-10 years later, has another set of issues but I haven't gotten to them yet. I'll probably try to fix any problems with those at the core level prior to wrapping them in wood.

I suppose this is an example of lack of proper QC in the early days of Great Planes. My original '82 Tipo kit (described above) was one of GP's first production kits given GP was founded in '82.

David.