Square Pocket Protractor

A grid map tool that is modified with 1/16" drilled holes makes for the perfect pocket chart plotting protractor. Drill the holes by hand using a 1/16" bit spun with the index finger and thumb. Make a pilot hole at the spot to be drilled using the point of a divider leg.

Longhand Sight Reduction

An obscure sight reduction formula derived by a Frenchman named Doniol is the only reduction method that can be quickly done longhand without logarithms. Needed are four place cosine, sine, and haversine tables which can be found in the 1958, 1962, 1966, 1975 vol 2, and 1981 vol 2 Bowditch editions.


http://fer3.com/arc/m2.aspx/Haversine-how-derive-it-Bernecky-jun-2015-g31663


Doniol Formula

Sin h = n - ( n+m )a

Same name:
n = Cos ( Lat-Dec )
m = Cos ( Lat+Dec )
a = Haversine LHA

Contrary name:
n = Cos ( Lat+Dec )
m = Cos ( Lat-Dec )
a = Haversine LHA

rule:
Lat + Dec > 90 use (-)Cos of Complement

When haversine tables are not available then substitute
a = ( 1-Cos LHA )/2

Ditty Box

Every boat should have a go to ditty box for storing miscellaneous extra items collected over the years. Rubbermaid tubs work well and are in various sizes to fit available onboard space.

Paracord Dispenser

Improvised Artificial Horizon

A salsa container and a black plastic coffee can lid pair up well to form an improvised artificial horizon suitable for sextant celestial navigation practice when a sea horizon isn't available. Punch quarter inch holes around the perimeter of the coffee can lid to create a baffling effect that smooths and settles disturbances at the surface. Fill the salsa container to the rim with water then float in the plastic coffee can lid. Tap and spin the lid to remove any bubbles trapped under the lid.

Modified Double Becket Bend

The modified double becket bend will add extra friction over the single becket bend and insure this bend from slapping loose.

Cap Lanyard

A neck lanyard can serve double duty as a cap lanyard by leaving a 6 inch tail finished with a figure eight knot. Feed the cap strap through the eye and never lose a cap to the wind again.