NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Sextant frames
From: Bill Morris
Date: 2009 Apr 16, 13:53 -0700
From: Bill Morris
Date: 2009 Apr 16, 13:53 -0700
Brad and Jeremy The coefficients of linear thermal expansion of bronze and Dural are very similar at 18 and 23 x 10^6/K respectively. However, their thermal conductivities are not. The figures given for bronzes are 42 - 50 W/(mK) while for Dural it is 164 W/(mK). In other words, aluminium alloy conducts heat much better than bronze and will equilibrate with its surroundings quicker. An alloy sextant left in the sun will get hotter all over quicker, but will also cool quicker. The T in SNO-T means that the sextant is Tropicalised and presumably the paint has high reflectivity. I will leave it in the sun with a black-framed instrument, compare temperature rise with thermo-couples front and back and report back. Bill Morris --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---
