Sunday, 14 November 2010

Galley trigonometry

We were out to the boat today to collect the last of the things on the boat before the winter.  At the same time I took the chance to measure up inside.

At some time the stove has been moved from by the door to a new location just aft of the forepeak on the port side.  Cooking in the boat is a pain - no headroom and nowhere particular for the steam to go.  So, we plan to put the stove back in the locker by the door to be able to stand in the entrance when cooking.

The stove is an old Origo twin burner spirit stove.  In principle we could just have it stood straight on the drop down flap on the locker - but right now it's gimballed so I'm looking to build a frame to hold it that can be slid in and out.

The locker is not as tall as the existing suspension points so we need some re-engineering for the stove to fit...  so I'm sat down this evening with notebook and laptop to look at the geometry.  It's a long time since I needed to play with sines and cosines!

The first thing I find is that the existing solution is designed to just clear the surface below - it will work in principle with any heel angle. Nice!  With less height to work with we don't have that luxury, unless I make it height adjustable.  But - we never run the stove with the boat on the move - so that's unlikely to be a big problem.  Gimballing is to keep supper safe when we get waves coming in when we're anchored up.  How much is enough is hard to say, but 20 degrees maybe? 

Like most things the solution is going to be a compromise:  for a given pivot height, as you move the stove up to get more clearance (to tolerate more heel) but the result gets less stable. 

And you need to think about the pots as well.  Within the height available, more clearance quickly means the pots will be above the pivot.  Weight high up reduces the effective length of the pendulum - making it quicker -and too much weight too high is simply unstable..

So... a quick spreadsheet later, and the answer is.... 

Well not 42! 

The pivot moves down from 210mm today to circa 170mm. Then losing 5mm from the clearance should give me those 20 degrees of tilt and still keep stable operation.

Feasibility study: Check. Done