The mast tube supports the free-standing "un-stayed" mast and is
designed to withstand 32 tons of loading! It transmits these forces
through the main bulkheads and the integrated structure of numerous components.
|
|
An 8' long styrofoam mold was CNC-cut, per my design, by Foam Source
Inc. in Cocoa, Florida. They coated it with molten urethane so we could
laminate directly without the resin affecting the styrene material.
The Ø6.032" ID fits snugly on the 10' long PVC mandrel. The Ø12.375"
OD will be built-up with fiberglass and vinylester resin then the styrene
is burned-out using laquer thinner. The 30° angle, which mates
to the windshield's center panel, is also formed during this process.
Here, the sprayed-on layer of gel coat has cured and is ready to receive
the first laminate.
|
|
A layer of tri-axial fiberglass cloth is applied with the uni-directional
fibers of the warp oriented along the tube's axis. This provides stiffness
at the ID for the mast's extreme bending loads.
|
|
This detail, from the tube's bottom edge, demonstrates the strong
unidirectional main fibers. The other fibers, criss-crossing
at 45º, provide additional support.
|
|
Three layers of tri-mat are then wound around the tube, in one
continuous laminate, with the uni-directional fibers following the circumference.
The pattern is 1" shorter at each revolution to provide a smooth, tapered
transition. This upper segment utilizes the entire 51" width of the
material.
|
|
| Notice the difference in diameter between the
first axial layer and the spiral-wound triple laminate? Click the image
to enlarge for better detail. |
|
The seam between the upper
and lower spiral laminates uses the staggered 1" overlap technique, resulting
in a smooth transition and strong interlocking layers.
|
|
The finished mast tube is nearly
8' tall with a Ø12.775" OD, yet weighs only 35 lbs. No, I haven't
gained a ton of weight! It was unseasonably chilly on this day (40º
F) so multiple layers of baggy clothing were the fashion du jour.
The cold temperatures slowed the resin curing process substantially.
|
|
Time to remove the styrofoam
core. Judicial application of a volatile petroleum distillate resulted
in the rapid reduction of styrene to a goo reminiscent of the slime in Ghost
Busters 2.
|
|
| The urethane coating, applied
during fabrication of the styrofoam core, peeled-off easily. Some of
the Playdough® putty, used to fill-in surface imperfections, came off
with the urethane. |
|
| A lot more of the Playdough®
stuck to the tube's white gel coat surface. What an icky mess!
A few minutes of 1500 psi water pressure-washing and some elbow grease with
acetone removed the remaining putty. |
|
| I used the ShopBot to cut a
mounting plate which precisely centers the mast tube on the bridge deck.
The Ø12.615" diameter centers the tube perfectly for subsequent laminations
to the adjacent bulkheads. |
|
| The mast
tube is placed over the plate. Then the 2.625" aft support is positioned.
This support will serve double-duty as an armrest for the settee. Kinda
over-kill, huh? |
|
| The white
gel coat of the tube's interior is visible in this view. Notice the
completed decks above the port hull too. |
|
| This view provides our first
glimpse at the relative proportions of SEDATION 4.
The mast tube's 30° tip ends approximately 6" below the apex of the pilothouse
roof. The 8' tall tube doesn't seem very tall in this context. |
|
