Re: Lateen Rig

Gordon (
Sat, 22 May 1999 22:18:43 -0700

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West Wight Potter Website at URL
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Perry Phillips wrote:

>I enjoyed the sunfish that I had several years ago, but not as much as my
>teenage boys did. While I was trying to learn more about sailing efficiency
>with my larger sloop rigged boats, my boys were out blasting around on Big
>Lagoon in Pensacola, Fl. There's a lesson somewhere in there...
>Your statement reminded me somewhat of a similar thought expressed by Joshua
>Slocum (1st to sail around the world alone in a small ship). Slocum made the
>statement regarding the Chinese Junkrig, however, and when his crew
>mutinied and
>put him ashore in South America with his family he built a 35 ft. canoe style
>boat and rigged it with two mast and junk sails and sailed it 5,000 miles home
>to the U.S. (Voyage of the Liberdade) I must admit the lateen rig is simpler
>than the junk, but the junk offers only slightly more complexity and infinitly
>more control and simplicity of operation.


You are not the only junk rig fan in this group. Steve Barnes (OldSurfDude)
is also planning on assembling a junk rig Potter. Also are you aware that a
junk rig was offered as an option on one of the UK-built Potters?
>Did your boat come with the lateen rig, or did you add it? Did you do
>special to support the mast step on the cabin sole? I've been very curious
>about this. I'm not quite sure how I'm going to accomplish the mast step
>for my
>conversion of Frodo. I really want to build a tabernacle that will simplify
>raising and lowering the mast, and allow transport with the mast slid
>forward in
>the tabernacle with a rest at the bow and stern.

My 1967 Potter 14 had a gunter rig. To use a lateen rig, I installed an
aluminum tube as a socket for the round Sunfish mast. The base of the tube
is attached to the v-berth deck with a boat trailer roller bracket. (Steve
Barnes used a spider casting.) A bolt goes through the bracket and the foot
of the mast socket. The holes in the bottom of the bracket are elongated
(for trailer roller height adjustment) so I have some rake adjustment
there, but my initial adjustment worked so well that I've never changed the
rake, which I had set as vertical as I could make it. Since the bracket is
much wider than the tube, I could also adjust the mast verticality to port
or starboard by means of additional nuts that fix the position of the tube
along the long, fully threaded bolt. Again, my initial setup seemed to be
just right, so I haven't used that adjustment either.

The tube extends through a hole cut in the cabintop, centered 11 inches
forward of the original mast. The installation at the top is unnecessarily
complex and somewhat Mickey Mouse. I would do it differently next time. I
wanted to have rubber in the joint to allow the rake adjustment, so I used
something from a hardware store intended for the bottom of toilet tanks. To
make the mast socket look neat, I used a plastic flange for a ventilation
port. The rubber fills the space between the ID of the flange and the OD of
the tube. The rubber is too soft however, so the mast easily compresses it
and leans slightly from side to side under load when tacking.

I bolted and epoxied additional plywood to the cabintop around the mast
socket to be sure the stress wouldn't rip open the cabin. (My first
generation Potter already had 1/4 inch plywood backing to the fiberglass
cabintop and has no interior liner.) Because the mast socket was so close
to the front of the cabintop, I was afraid that there wasn't enough beef to
keep the mast from going forward, so I added a muffler clamp U-bolt thing
around the front of the mast and secured it to the strengthened cabintop
behind the mast. (I told you it was Mickey Mouse.)

I have three holes drilled carefully through the tube inside the cabin. I
bought a new tool from Sears to be sure the holes would be centered and
perpendicular. A bolt goes through one of the holes. The mast is dropped
into the socket, and the base of the mast rests on the bolt, but the mast
can still rotate, as a Sunfish mast is intended to do. Having three holes
allows me to adjust the mast height. So far I have only used the lowest
hole, which keeps the lateen boom at about the same height over my head as
a stock Potter boom. In very light air I could try setting the mast higher
to try to pick up a little more breeze, but it probably wouldn't be worth
the trouble. Or I could add another hole and lower the mast (and the center
of effort) further to make the boat even stiffer, but then I would have to
remember to duck the boom.
>I'd really appreciate your insights regarding the stress involved at the deck
>and cabin sole. Have you experienced any cracking of the gel-coat or
>of the fiberglass?

Funny you should ask. The rig seems quite strong with no visible or audible
strain when sailing. Photos show both the mast and the spars bend in the
wind, probably desirable to release pressure in a gust. My reinforced
cabintop does not appear likely to fail, but shortly after a very windy,
gusty afternoon sail on a local lake, I noticed a hairline crack at the
edge of the cabintop, all the way around. It is along the line where the
original plywood doubler ends, a couple of inches from where the fiberglass
starts to curve down to the sides. It may or may not mean the whole cabin
is flexing.

What I intend to do is to add a shelf that will be bolted to the forward
and side decks. The mast socket will pass through a hole in the middle of
the shelf so the mast side loads will be distributed to the side decks
instead of being carried entirely by the cabintop. The shelf should also
provide useful storage space for bulky lightweight stuff.

Even though the mast moves from side to side (1/8 " or so) in the soft
rubber at the cabintop opening, there appears to be enough flexibility in
the trailer bracket mount that the slight angular movement of the tube is
not noticeably stessing the mounting to the V-berth deck

Steve Barnes had a later P14 that he converted to a lateen rig at the same
time I was converting mine. He simply cut a hole in the cabintop, in the
same location as mine, and used a longer tube, which extends above the
cabintop. He did not strengthen the cabintop at all and had no problems
with the installation.

Lars Mulford can tell you about his lateen rig, the first one in this
group. It was a new boat built on order from International Marine, but the
mast socket support was badly conceived and started to come apart when Lars
sailed it. The Annapolis Potter dealer rebuilt the mast socket
installation, making it very strong. Lars was happy with the final result
and sailed it in near-gale conditions.

Larry Brown also had a custom-built lateen rigged Potter from the Potter
manufacturer. He didn't report any problems and is an advocate of the
lateen rig for Potter-type boats. The lateen rig was offered as an option
on the P15 at one time, but as far as I know Brown's and Lars' were the
only ones built.

When I bought my Sunfish spars from a Sunfish dealer in Berkeley, the
salesman wondered if the spars would be overstressed because of the much
greater mass of the Potter compared to the Sunfish, but I suspect a
200-pounder hiked out on a Sunfish would put as much stress on the spars as
the heavier Potter does. Both the Sunfish and the Potter are designed to be
sailed flat, with as little heel as possible.

Probably none of that information will help you design a tabernacle for
your junk rig mast. The lateen rig is so simple to rig and sail that I
can't see the advantage a junk rig might offer, but I confess I don't know
much about them. My Sunfish mast is only 10 ft long and is easily dropped
into the socket. In fact I can stand on the ground, with the boat on the
trailer, and hold the mast out at arms length to drop it into the socket.

Harry Gordon
P14 #234, Manatee
Mountain View, CA