This is transferred to your foam.
Why only half the section? The
other half is the mirror image of the
first. If you mark the centerline on
the surface of the foam, simply
flipping the drawing over and
aligning it at the centerline and an
elevation will give you a full section.
This method eliminates any
asymmetry in the form.
offsets you've noticed some
negative numbers. What's that all
about? In boat design the in the
buttock sections of the table the
numbers represent heights and
depths from the datum waterline,
even though a buttock line is a
centerline the buttock line is, and all the following columns give the height at which the form intersects that
buttock line. The datum waterline corresponds to our zero baseline. Just as there is boat below the water
we have nose cone hanging below the zero baseline. The negative numbers reflect this part of the nose. As
these lines are again more horizontal they are more accurately captured by vertical measurements. So we
revert to buttock measurements here. Let's look at station 23 for an example:
data that helps us with Station 23.
the upper buttock and waterline
offsets. As you see the full section
is made up of three curves. The
ends of these curves may overlap.
For example, the curve of the
waterline plots (in red) starts at
elevation -7 and the lower buttock
plots (in blue) end at -3.
14 are transected by the
forward frame line. The forms
will have to be cut to remove
the waste behind the frame
line. The table of offsets
contains a column of
distances forward from station
0 to the frame line for
elevation 2 thru -11. To make
this cut accurate and less
difficult you may want to
remove the center material
from form 12 below the
elevation 2 line making it a
semi-horseshoe shape. The
thinner sides (say 2") will be
easier to cut accurately and
each side can be cut
separately.
you'll notice that there's still nose beyond the form for station 22. As the forward face of what would be form
23 merges with face of station 22 with a curve we can't just cut another slice of salami to get this shape. We
have to develop the lines for the transition from the outer nose surface to the air intake.
plot these parts. If you look at the Buttocks table of
offsets you'll notice that the last two columns have a
different format. The "Apex" column gives the elevation
and station coordinates of the farthest point that the
buttock line extends to the front of the car before it turns
back. The "Return" column contains similar data for the
point where the curve ends inside the nose's air intake.
in the Apex and Return columns for those waterlines that
curve around into the air intake. To get our mold to this
stage we have been working from the rear of the nose to
the front of the car developing the sections. Now we are
looking across the car at the front profile. How do we
develop this front surface without having a plane for
reference? Assuming that we don't have a CAD/CAM
set up to carve it for us, my approach is to use
cardboard templates of the apex cross sections. CAD
file here Apex will save you having to loft them.
"0" template. It starts at station 22 has its apex out
beyond station 24 and turns back toward 23. If we cut out
the male profile of this template in cardboard or thin
plywood we can mount it on Form 22. In effect the
template itself becomes a small form. As the back
vertical of the template is station 22, we can cut a slot in
form 22 and align this vertical with the rear surface of the
form. After making male profiles of all the apex cross
sections and fixing them in form 22 you should have
something like this:
form, that is they are more than 23" from the rear of the
nose. The templates in gray are 23" or less from the rear
of the nose. My approach to get the end shape is to glue
small blocks of foam between the templates and then to
sand the foam to their profiles.
frame or adjoin the skin should have a 3/4" return flange molded in.
You should avoid any edge radius of less than 1/8th inch. As
bonnet and frame angles approaching the rear of the nose will vary,
I haven't provided any detail on the recess for the bonnet join. You
should allow at least 1/8 inch here for weather stripping and for
your bonnet thickness. This join will look something like this in
cross section between stations 0 and 2. The angle will depend on
your frame rails and scuttle height.
the finish. You have two choices: you can pull a female mold from your male mold which, if you've done well
with your plastering, will give you a nicely finished part. Or you can lay up your nose cone over the mold and
fill and finish its rough surface. If going with the female mold I think a two piece unit is best. I would have it
separate along the buttock "0" centerline. If you're just doing a male one off remember to deduct the
thickness of your lay up from the dimensions given in the offsets. Good luck!
given to any individual or groups to copy and distribute these materials for non-commercial uses only. I encourage
members of the Locost community to use this intellectual property to build tooling for the production of the nose cone
and to share the tooling freely with others. But if you're going to make a buck, I'll want my 10%.