May 2021

 May 4,

Worked on the tanks again this weekend.

I am welding in the side of the black water tank that will fit in the curved bilge.  I start by welding the inside.   This side piece is critical because it will fix the curvature and define the one side that is square.  I did not properly model the tank here and stepped back to produce a full three dimensional model.

Shown here is the full three dimensional model.  Note that  the part that lays on the table is square while the rest is not.  This is correct.  When I welded the outside,  enough heat is generated that the plastic relaxes into the correct angle.

Heating the bottom of tank 2.  I'm using the 3 dimensional jig (model or mold) of the tank here and the results were perfect.  When I took off the clamps,  the HDPE plastic did not spring back and laid comfortably on the mold (except for the very ends which easily clamp down). 

May 7,

I took a lunch break and worked out how to make the inspection ports for the tanks.  Basically I've cut out a 14.5 inch circular disk from the HDPE for a port cover and made a doughnut of the same outside diameter for a backing plate.  I'm going to thread the backing plate and tank skin to accept a bolt.  This is just to keep the bolts in place during installation. I will use nuts on the bolts to actually hold the port in place.  

This will be the ring for my backing plate.  I've mounted it on a jig to put in a wood lathe were I will cut out the center to leave a ring.

Just the back side of that backing plate jig. 

Attached to a lathe and cut with a nice finish.  

inspection port cover in the top of the figure with the backing ring at the bottom.

Fitting the tanks.  I placed the tanks in the bilge so I'd get the curvature to the sides correct. 

May 15,

Clamped up and ready to weld    

All four sides are in.

Measuring to build the first internal baffle.

Fitting the baffle.  It needed a minor adjustment.  Also note that there is now a lip around the edge that will eventually receive the top.