RebelCat 4 - Inspired
Back from Illinois, I started designing
RebelCat 4. It would be much closer to the original I had made
in Brazil, but improved in many ways - more flotation, more
sail area, kick-up rudder and centerboard like RebelCat 2,
traveler for adjusting the boom's angle to the boat and for
keeping the sail flat, adjustable fairleads for the jib... I
had it all planned out and designed on my computer. So I got
some 10-inch PVC pipe adn traffic cones.
Larger pipe would solve the flotations problem
of RebelCat 1, without making the cat longer. Well, cones on
the rear would add about 30 inches, but that was necessary to
close the water behind the hulls. I found some aluminum pipe at
a salvage yard - it was perfect. Two sections 10 feet each by
This pipe would make a perfect mast. 20 feet
would be too tall, so I would cut one shorter. I cleaned it up
with a sanding disc. I then made a coupler from slightly
smaller steel pipe to join the two sections. All was going
well. And then I saw the movie 'Waterworld', with Kevin Kostner
and his 60-foot trimaran. I watched it again, and a third time.
Hmmm, I began to wonder if this small cat I was now making
would be big enough to make an impression.
What happened next is hard to remember, but I
decided to make a larger cat. I found a perfect location on a
farm outside town, bought some 15-inch pipes 20 feet long, and
set my tiny 10-inch pipes aside for now.
I wondered how I was going to get this cat on
my roof-rack, but now I was committed - no turning back. To see
just how much bigger this cat is than the one I had started,
look at the lower right - the 10-inch pipe is to the right of a
4-inch piece and is dwarfed by the new ones.
I'm sitting outboard where I want the seats to
be, to give extra leverage without hiking out. The deck would
be a completely new design as well.
This time I would not stuff the entire pontoons
with foam, as with RebelCat 2. I decided that bulkheads would
be a better way to use it. Two or three discs together, then a
gap of 10 inches, then more discs. This would give rigidity
with less foam, and it would create many bulkheads for safety.
The discs have to be compressed to get them in, so they press
from the inside.
A tamper/stuffer made from a mast section
(aluminum pipe) and some wood scraps. After compressing a disc
into the opening, the tamper is used to push it to its
predetermined position. By marking inches on the tamper,
starting at the head, it is possible to position a disc
precisely. This is necessary to get the disc groups under
This is the first stages of making the foam form which will
be placed inside the nose of the pontoon so that the PVC will
have something to collapse around when it is heated and folded
to make the wedge shape.
This pic shows one side, with a single rectangle of foam as
the center. Each side of the form was then filled with foam and
covered with cardboard until it took on the shape desired for
the nose. Had I known how stiff it must be to resist the
pressure of shaping the hot PVC over it, I would have made it
even denser and more rigid. RebelCat 5 uses an even more
advanced method - no form remains inside at all.
Each pipe was cut back from the opening on opposite sides.
The poontoon in the background has already been cut and the
form is inside.
The completed form is jammed into the pipe against discs
which have been precisely positioned inside.
The task now is to heat the entire front of the pipe until
it's soft enough to fold around the form.
One of the many challenges faced during this procedure was
keeping the form from moving inside the pipe once the PVC
became soft and no longer held the form in place. That's right,
and I didn't think about it either until the form began
rotating. It must remain perpendicular to a line drawn between
the cuts, otherwise the nose will not form properly around the
form. This and all of the other challenges of heat-shaping
are covered in the DVD on RebelCat 5. No form remained inside
on RebelCat 5, due to an advanced technique.
I did a lot of research on shaping PVC, but I found nothing
about shaping large pipes into the kind of wedge-shaped,
wave-piercing bows found on modern cats and tris. So I invented
the technique. It worked so well, that I have advanced the
technique on RebelCat 5. The DVD covers heat-shaping in great
detail, and I believe I am the only one in the world to be
doing this - creating hydrodynamic hulls from PVC pipe by
A lot has appened since the last pic, but a friend and I
were so busy with the heating, folding and shaping, there was
no way to take a pic.
Briefly, the end of the pipe must be heated evenly, which
means turning it like on a spit over a ceramic kiln where two
large propane burners are blasting flame in our faces. It was
so hot doing this, it gave new meaning to "slaving over a hot
stove", hence no shirt.
The two by fours are attached by a hinge to form a crimper
to seal the nose into a flat seam which was later glued,
covered with a folded strip of hot PVC and glued again.
By repeatedly heating small areas of the overlapping
and somewhat wrinkled PVC, it was possible to iron out most of
The front seam was then covered with thin, hot PVC
and glued in place, feathered and sanded. The result was a
wedge shape just like catamarans today, especially the larger
It is now possible to make respectable and quite
hydrodynamic pontoons from PVC pipe of any size. The DVD shows
There were slight imperfections - bumps and dips - that I
wanted to remove, even though they would not have been in the
water. The 'curse' of the perfectionist, I admit. So I heated
thin 'patches' of PVC to cover these areas and formed them over
sand which I had used to fill the dips. After the patch cooled,
I removed the sand and glued the patch in place. Here I'm
sanding the edges of one such patch to blend it with the rest
of the hull. Because the 'patching' process involved hot PVC,
it was not possible to photograph it easily, but it was
well-documented on video. I may have invented that technique
Notice the grey PVC strip which was heated and then folded
and glued over the trimmed leading edge. I wanted a closed and
solid nose, and this worked perfectly.
I made templates from clear, flexible vinyl from the fabric
store, then taped them to the pontoons and sprayed paint over
them. The paint is Krylon Fusion and bonds well to PVC, so well
that when it dries it can't be scraped off with your
fingernials. It's also specifically made for PVC and plastic.
It dries leaving no smell after about a week.
Since I had already created the design in the computer, I
simply scaled it up from my computer printout to the templates.
The parts to be colored were then cut out and sprayed
The tail of the pontoon was shaped in the same way as the
nose, except that it was done horizontally. I wanted a 'tail',
not a second nose. Also, the water on modern cats and tris is
allowed to rise under the pontoon until it reaches the tail,
causing very little energy-robbing wake. My design works in the
The first (male) pontoon is finished, the other lies
This is a screenshot of the design in PageMaker. I usually
design in PM before starting construction. There are
another 10 pages of technical drawings, showing the frame,
seats, pontoons, and all controls, but they would take up a lot
of space here.
I had intended to paint the sails as shown, but there wasn't
enough time before the sailing event for which I was
The mainsail is huge. I spread out a 10 by 20 foot tarp to
work on (it wasn't long enough, so I added plywood at the top),
and using a chalkline, snapped a grid with 12-inch squares so I
always knew where I was. My computer printout had exact
coordinates for each corner, batten, reefpoint and cringle, so
I simply transferred them to the grid.
Okay, simply is not entirely correct. It was more
complicated than that, but as the cat will not move without a
sail, I was determined to make this sail.
What made it challenging was the material. It was probably
polyester, but it was also quite limp, unlike the Dacron
sailcloth I used for RebelCat2. This stuff moved all over the
place, created wrinkles, stretched, and generally made my life,
The sewing had only begun when the two large sails were
done. I now had a pile of trampolines to make, each one having
up to three layers.
I burned up my mother's old Brother sewing machine (shown
here) and switched to my other machine, a White heavy duty
portable. Three days later I emerged from my little cabin with
an armload of trampolines, enough to carpet my room.
The two pontoons are first positioned on spacers I have made
for the purpose of assembly. I don't want the pontoons rolling
off someplace, and I want them to sit at precisely the same
distance apart as they will be when attached to the rest of the
Here I'm setting the back spreader on. It gives rigidity to
the back of the cat and also holds the rudder. The pontoons are
held to the spreaders and deck frame with eight ratchet
Notice the shape of the pontoons at the nose. They are quite
close to the shape of modern cats and tris, which slice through
the water and waves with greater efficiency than a monohull,
which has to push a lot of water out of the way. These hulls
have been heat-shaped.
Finally assembled for the first time on Lake Powell, UT, as
part of a messabout of homemade boatbuilders. It doesn't look
so big in this photo, but those pontoons are 19 feet long and
weigh 100 pounds each.
Now you can see how big this cat is, with me standing next
to it. I'm confident it will carry six adults. The trampoline
on the back sleeps two comfortably. Can you believe I carried
this cat on my roof-rack? To see my writeup of this event at
Lake Powell, there is a page at duckworksmagazine.com with
So how did it sail? Like the wind! This cat is by far the
fastest I have made, and sailing alone I was not able to sail
it as efficiently as two. There are two sails to control at all
times, the tiller (rudder) and the daggerboard. But I
There are also two other controls for each sail. The
mainsail has a traveller at the back to adjust the position of
the boom relative to the centerline of the boat. The jib
(foresail) has a similar control on the front spreader. The
jibsheet blocks can be positioned at five spots on each side of
the bowsprit, giving the crew better control over the angle of
the jib in varrying wind conditions.
This cat is also the most complex and advanced of all
the cats I have made. RebelCat 5 borrows heavily from the
design and advanced controls but is much easier to make,
because it is mostly wood. RebelCat 4 was the experimental cat
I needed to make so that RebelCat 5 would benefit.
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