General HydroStatics
Ship Stability Software
Command of the Week
(New or interesting aspects of GHS that you may not know about)

(Requires GHS Part Maker version 16.34C or later)

As announced in an earlier COW, the CYLINDER statement within the Part Maker CREATE command offers a convenience that can eliminate the need for starting location numbers when cylinders are arranged end-to-end in a chain-like fashion. It was shown there that this is especially useful when the end location of the cylinder that you want to attach to is unknown because it was defined by Length, Azimuth, and Elevation (the LST option).

But it was not mentioned that the same feature is available when multiple cylinder statements are used to define one component.

This could be useful when modeling a propeller shaft if you want to give it some extra diameter in way of the prop hub and especially if the shaft is not perfectly horizontal.

Here is an example -- using names (variables) for numbers in PMX to make it easier to read.

REAL L:=-1.0, T:=0, V:=3.0, Len1:=2.0, LenHub:=0.3, LenTail:=0.15
REAL DShaft:=0.1, DHub:=0.2
REAL Angle:=-2.0
CYL(12) L, T, V, Len1, 0, Angle, DShaft, LST
CYL(12) ^, ^, ^, LenHub, 0, Angle, DHub, LST `hub
CYL(12) ^, ^, ^, LenTail, 0, Angle, DShaft, LST `end

Now let's chain to the end of the last bit of prop shaft and make a new component for the nozzle -- reversing the cylinder direction.

REAL NozLen:=0.5, NozDiam:=1.0, NozThick:=0.2
CYL(48) ^,^,^, NozLen, 180, -1.*Angle, NozDiam, LST
CYL(48) ^,^,^, NozLen, 0, Angle, NozDiam-NozThick, LST
JOIN Nozzle

For a propeller approximation (a cylinder with reduced effectiveness), here is a trick to avoid calculating the location.

REAL PropStart:=2.1, PropThick:=0.1, PropDiam:=0.7
CYL L, T, V, PropStart, 0, Angle, 0.1, LST
EFFECT 0.1 `estimated volume factor for the prop
CYL ^,^,^, PropThick,0,Angle, PropDiam, LST

And finally some fancy rendering to dress up our COW:

surface (hull\propshaft.c) shaft; color:bronze; opacity:1.0
surface (hull\nozzle.c) nozzle; color:blue
surface (hull\Prop.c) prop; color:red
render shaft, nozzle, prop

Not that this kind of detail is necessary in stability work. But anything goes in a COW. Someone said we've milked this one dry.

Questions, comments, or requests?
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