Some semi-random notes and observations on this topic from someone who
has messed about some with composite tooling:

* The C-150 is a pretty poor basis for such a project. If you do get
to the end of it, you'll have - a copy of a Cessna 150. If you're
going to go to the trouble, you might as well make something special
or at least different. If what you want is a 150, just take the cash
and go buy one. It will cost about half or a quarter of what it would
cost to replicate it in composites.

* Some pretty smart people designed the Cessna 150 for low-cost,
high-volume manufacturing in light sheet metal. If they had started
with the idea of a composite airplane, they would have been at liberty
(as you are now) to accommodate more compound curves and many other
improvements for lower drag and better performance of one kind or
another.

* Making a mold off of any riveted aluminum structure can be a
heinous, hateful experience. The seams and universal-head rivets won't
want to separate, and when they do you've got a mold with a bunch of
dimples and seams. So you end up spending hours and days refinishing
the molds.

* A while back, a couple guys made molds off of a BD-5 fuselage, and
then made carbon fiber shells from the molds. It was a neat project,
but I don't think any airplanes came from it, and last I heard of it I
think the whole project was for sale.

* The trouble it would take to smooth out a 150 fuselage enough to get
a nice mold off of it would probably be better invested in making a
new fuselage plug from scratch using plywood, lath, foam, and bondo.

* If you want to save some trouble, buy transparencies (windshield,
canopy, etc) for some other aircraft and incorporate them into your
plug. That way you know the plastic parts will be available and
relatively inexpensive, and it will save you the trouble of making
transparency tooling and having custom transparencies made.

* In the history of general aviation, there have been several
instances of someone using someone else's fuselage or wing or cowling
or whatever without permission as a direct pattern for their molds. I
don't know of any of them that became legal intellectual property
issues. However, it has almost always ended in tears for the
plagiarist. That history alone makes me believe no little bit in
karma.

* You have to show the FAA very little if anything in the way of
substantive data about the thing you've built. About all you have to
do is convince them that the major portion of the thing was made for
education and recreation, and that its operating limitations are
clearly marked. Ron W. can tell you a lot more about that than I can.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com/hp-24