Junk Rig Calculation Tools

Spar mass/strength

Calculates the mass and breaking strength of a solid or hollow spar

Input:

Length m
Base diameter mm
Top diameter mm
Thickness mm
Material

Results:

Mass kg
Breaking strength kpm

Densities from http://www.engineeringtoolbox.com/material-properties-t_24.html
Modulus of rupture from http://www.conradfp.com/pdf/ch4-Mechanical-Properties-of-Wood.pdf (mirror)
UHMWPE (PE 1000): http://www.arpnjournals.org/jeas/research_papers/rp_2019/jeas_0719_7819.pdf and https://www.azom.com/properties.aspx?ArticleID=909

Spar angle/rake

Calculates spar angles (mast rake for example)

Solve for:

Fill in the two missing factors and remember to use the same unit for length and distance

Example 1: If you want to find out how much forward the top of a 9 meter mast is compared to the base with 4 degree rake, choose "Distance" and fill in "9" for length and "4" for angle.

Example 2: If you want to find out how rake there is on a 12 meter mast which top is 1.02 meters forward of the base, choose "Angle" and fill in "12" for length and "1.02" for distance.

Input:

Spar length m
Spar distance m
Spar angle degrees

Credit goes to http://www.1728.org/angsize.htm

Hull properties

Calculates sail area vs. displacement and displacement vs. waterline ratios

SA/disp

10-14 Cruising sailboat
15-19 Cruiser-racer
20-24 Racing sailboats
25+ High-Performance racers

Disp/LWL

0-49 Ultralight
50-119 Very light
120-249 Light
250-319 Medium
320-379 Heavy
380+ Very heavy

Sail properties

Calculates batten lengthts for given sail area

Fantail calculations from https://junkrigassociation.org/technical_forum/1060993

Johanna calculations based on http://www.junkrigassociation.org/Resources/Documents/Arne%20Kverneland's%20files/Johanna's%20sail%20plan,%20sheet%201-9.pdf