Album Index for Album 0006: Details and Designs

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Drawing to determine location of pedestal and length of jib-boom for a trackless, semi-self-tending jib. You need to know the jib's chord length at your tightest sheeting angle and the chord length at the widest sheeting angle that you intend to tack through. The clew is located at C1 when sailing deeper and the sail is trimmed as full as as the design allows, with the chord at the minimum designed length. The clew is located at C2 when close hauled, and the draft is shallow, with the chord at its maximum designed length. To determine dimensions for deck layout: Draw a line connecting C1 and C2, and find the midpoint, B1. Draw a line perpendicular to C1-C2 thru the midpoint, B1. The pedestal should be located where this line intersects the centerline of the boat(B2). The length of the jib boom is the distance between B2 and C2, which is the same distance as B2 to C1. When you change course from a deep reach to a close haul, trim the boom tighter with the jib sheets on both sides. The chord will increase, and the draft will get shallower. Thereafter, as long as your tacks are symmetrical, the jib will self-tack and be well trimmed. (You need a block outboard about 2/3 of the way back from the front of the club for leading the jib sheet. You trim the jib with the UPWIND sheet.) A more complete discussion of the sheeting can be found in Brion Toss' book _The Rigger's Apprentice_.
This is a modification of the Griffith Hatch, designed to be retrofitted to the front hatch of the Potters. A new coaming is fitted inside the existing coaming, creating a groove to catch any water that enters over the old coaming. The lower surface of the groove must be a little higher than the deck surface at the corners. A hole is drilled thru each corner of the existing coaming to permit the water to drain out. It is not necessary to have close tolerances between any of the opposing surfaces. I originally drew the sketch with foam at the top of the inner coaming, but in retrospect, I don't think it's a good idea. If the foam fits tightly against the underside of the hatch, condensation is trapped to the centerline of the inside coaming, rather than flowing downward along the curved inside top of the hatch all the way to the vertical edge of the hatch cover, where it can drain harmlessly to the outside. If it's trapped by the foam, it will drip on you as you sleep. And the loose fit is probably a good idea for another reason, namely that it provides a little ventilation to reduce condensation when you're sleeping. See http://mims.com/maib/coaming.htm for a history of the Griffith Hatch.
light air Vs breeze dynamics.gif
Details of the boom. A compression post for the vang bail. Also shows the "trap door" for the terminal that the internal outhaul is anchored to.
(Note: The clew of sail is mislabeled as the "tack" in this drawing. Oops.)
maststep halyard organizer

Design concept for a Potter 15 120% genoa, by Judy Blumhorst and Jerry Barrilleaux. It is full hoist and high aspect ration so it should sail to weather well. The LP is short enough to run the jib sheets inside the shrouds, which should also contribute to it's ability to point high. The clew is pretty high to permit good visibility underneath, for tacking in crowded waters.

The entry was intended be shaped so it is fairly rounded for a wide angle of attach without stalling and enough "punch" to get thru chop,

Designed to be used in wind up to about 22 knot of apparent wind. (about 18 kts true wind when pointing)

The prototype was commissioned by Jerry Barrilleaux in early 2002 from Eliot Paterson Sails (www.epsails.com). and tested. It proved to be superior to the older "class" sail, with enough power to punch through chop, excellent upwind and reaching performance and very good performance off the wind. It is now available from EP Sails, Odyssey Sails (the Potter builders' sailmaker) and AltaSails.

It has proved to be a very versatile sail for the Potter 15 and over 50 were sold during 2002. It is known as the "J&J Lapper"

Neither Jerry nor Judy receive any money from the production of the sail.

Mob recovery using lines run aft