Photos of the
Twin Blade Manta Equation development and some construction photos. All will fit
into 800X600 and are around 40KB. Higher resolution copies are available, just
ask. Click the image for a full size shot.
Return to the
main gallery, a gallery of movie clips showing the boat in
action has also been added.
tests of the Manta Equation. We pulled as hard as we could, and just got tired!
At the equivalent of a force five blow with all sails up the boat heels up to 38°,
this is outside any helmsman's comfort zone, but easing the main and dropping
the gennaker puts things on a more even keel. You need to be a competent sailor
to be out in winds of this strength. At force six the angle increases but the
boat is still stable, though we would suggest that in a force six an experienced
sailor should have the main should be reefed and the gennaker kept very firmly
in the chute. The Manta equation stays positively stable to 89°.
||This is 24°, and
starting to get exciting. The boat will be taking in some water through the
rudder control rod openings and waves would be breaking over the lee foil. This
is about as far as you can get with all three sails up while reaching in a force
four. Either bear away or stow the gennaker and ease the main and jib to come
more upright. This will be faster as the sails will be powering forward rather
than just producing heel.|
||Now we are at 31°, a
full force four with three sails up, broad reach with the sails oversheeted.
Sailing at this angle is uncomfortable, we know, we have tried it. Water enters
through the rudder control rod openings and some splashing from the immersed
foil. Drop the gennaker, and ease the main sail to bring the angle of heel down
to something more controllable and gain more forward way. Reefing should be
considered, especially for the less experienced sailor.|
||This is 38°, the
calculated maximum possible with a force five blowing and maximum sideways
resistance from all three sails. In practice the boat would not be sailed in
this configuration. The main and jib would be powering forward offering less
sideways force and the gennaker should not be flying. Reefing would be
recommended, indeed essential for any inexperienced sailor.|
||42°, and you really do
not want to be here. This was as far as we could pull the boat with the set-up
available. All sails up, oversheeted on a broad reach and hit by a force six
gust might do it. Drop the genny, round up and ease the main to regain your
composure. Then reef up and head for the shore, time for a stiff drink!|
showing the method of mounting the foils.
You can view this as an animated GIF
(downloads in about 2mins at 56K) or as a stop-motion
AVI (similar download time but more colours).
|Stemhead fitting. This picks up a glassed in stainless steel bighead. Most
fittings are similar, seat mountings, rudder pintle mounts, mast gate mounts,
all of the rudder control system and front padeye. Other fittings that you may
want to move or replace screw into embedded marine ply.
||This is the first hull fresh out of the new mould, quite an occasion. This
view shows off the keelson. The boat carries 25kg of lead at the lowest point of