Sandia and biplane blades are not same mass

[perryjohnson]

The biplane region of the biplane blade is heavier than the monoplane region of the Sandia blade.

Fiddle with the blade_definition.csv file to match the mass per unit span for both blades.

[perryjohnson]

I think the external surface layers might be to blame for the extra mass. I didn't cut their thickness in half, and now there's twice as much external surface area in a biplane station as there is in a monoplane station.

[perryjohnson]

But, is it feasible to cut the thickness of the external surface layers in half? The gelcoat layer is so thin (0.6 mm), and so is the triax layer (5 mm)!

[perryjohnson]

In the biplane blade, station 10, we have a total mass of 2557 kg/m, and: root buildup (triax) -- 28% of station mass external surface (triax) -- 20% of station mass external surface (gelcoat) -- 12% of station mass

In the monoplane blade, station 10, we have a total mass of 2190 kg/m, and: root buildup (triax) -- 35% of station mass external surface (triax) -- 15% of station mass external surface (gelcoat) -- 8% of station mass

[perryjohnson]

oops, no I was reading the plots of percent mass wrong. it's actually the INTERNAL surface that are to blame for the extra mass. So, we really have:

In the biplane blade, station 10, we have a total mass of 2557 kg/m, and: root buildup (triax) -- 28% of station mass internal surface (triax) -- 20% of station mass internal surface (resin) -- 12% of station mass

In the monoplane blade, station 10, we have a total mass of 2190 kg/m, and: root buildup (triax) -- 35% of station mass internal surface (triax) -- 15% of station mass internal surface (resin) -- 8% of station mass

[perryjohnson]

I mean, the external surface also is to blame for some of the extra mass, but the internal surface holds a larger percentage of the station mass than the external surface. (This is probably because there are 3 or 4 internal surfaces, due to the shear webs. There is only 1 external surface, though.)

[perryjohnson]

Okay, I got the mass of the biplane blade station 10 down to 2187 kg/m -- pretty good!

To do this, I changed the following part thicknesses: root buildup height: 0.0120 m (from 0.0125 m) internal surface 1 height triax: 0.003 m (from 0.005 m) internal surface 2 height triax: 0.003 m (from 0.005 m) internal surface 3 height triax: 0.003 m (from 0.005 m) external surface height triax: 0.003 m (from 0.005 m)

root buildup height upper: 0.0120 m (from 0.0125 m) internal surface 1 height triax upper: 0.003 m (from 0.005 m) internal surface 2 height triax upper: 0.003 m (from 0.005 m) internal surface 3 height triax upper: 0.003 m (from 0.005 m) external surface height triax upper: 0.003 m (from 0.005 m)

[perryjohnson]

uhoh ... it seems like the upper structural parts are not getting included in the station mass!

For example, if I change 'spar cap height upper' from 0.057 m to 0.2 m, the mass does not change.

[perryjohnson]

I fixed both parts of this bug!

(1) The blade masses now match at each station.

(2) The upper structural parts are now getting included in the station mass. In structure.py, lines 2805-2879, I was initializing upper structural parts with lower structural part dimensions. For example, the buggy code said:

self.upper_spar_cap = SparCap(
            parent_structure = self,
            base = b_SC,
            height = h_SC)

when it should have said:

self.upper_spar_cap = SparCap(
            parent_structure = self,
            base = b_SC_u,
            height = h_SC_u)