compound curves in plywood

My question is, would it be possible to laminate your own shell using
vacuum bagging? Seems to me even the wettest veneers would split if you
tried to force them into or around a male or female mold. to date, the
only
sort of manipulation I've done with ply is to wrap 1/16 leading edge
pieces
over a hot pipe. I just don't see how Hawley Bowlus got the compound
curves..


They used a boatbuilding and canoemaking technique that used bands of thin
veneer laminated over a male mould. The process is called "Cold Moulding"
and there are a couple of books about it in the "boatbuilding" section of
the library.

Essentially you build up a male plug with plywood formers covered with
fairly closely spaced strips of lath. The veneer thickness is selected to
give you an odd number of laminations, 3, 5, 7, etc. The bottom layer goes
on about forty five degrees to the lathing. Staple it down here and there
to hold it in place. It is wise to use heavy cardboard tags under the
staples because you are going to pull them out when you put the next layer
in place.

Brush the first layer with glue and cross it with the second layer at
something approximating 90 degrees. Aerolite glue works well. Brush the
cream component onto the first layer and then brush the hardener onto the
bottom of the second layer. Pull the staples as you go and restaple through
both layers.

The third layer goes on like the second, but aligned with the airflow so the
finished grain will be pretty! :-) Pull staples and staple it down as you
go.

After all the layers are down pull you vinyl over the whole banana and turn
on the vacuum pump to pull it all tight and hold it down.

If you want more than three layers of veneer repeat layers 1 and 2,
finishing with the top layer aligned with the airflow.

After the glue is hardened, remove the bag and sand the whole thing with a
random orbital sander to contour.

Standard industrial veneer for veneering furniture, etc. is 1/28 inches
thick. That is just under a millimeter for you continental folks. A three
layer veneer would be close to 3mm thick or a stout 1/8 inch. Be gentle
sanding because it is really easy to sand completely through a veneer layer
and get real embarassed!

Any stringers or frames are glued inside after the skin is finished. This
CAN be done without expensive or bulky tooling. The Dutch made fighters
using this technology in WWI.

Highflyer
Highflight Aviation Services
Pinckneyville Airport ( PJY )