Cowl Ventilator – II

How Big?
CowlVentilatorsI started this tutorial without anything more than a general idea of what size cowl ventilators needed. While looking around I found this photo though. We can see the stack in the background, projecting through the “Fiddly Hatch” which is sitting on top of the Boiler Room Hatch and with two cowl ventilators. The single cowl ventilator is just in front of the Engine Room Hatch complete with skylight.
EngineRoomCVFit_1I have been sketching out a Boiler Room Hatch and Engine Room Hatch for my O scale ship Grażyna. So .. I created a ‘quick and dirty’ cowl ventilator using the 1 inch cowl and 1/2 inch. How ‘Quick’ and how ‘Dirty’ you ask? So much so that no attempt was made to make an inner and outer skin to the mesh .. poor thing. Still .. quite good enough to use to scale the thing. Prior to saving I made sure that the QAD Cowl Ventilator was grouped. Very important.

I imported the cow ventilator and placed it approximately where it would go on the Engine Room Hatch.

EngineRoomCVFit_2Since Sketchup is a CAD program we can make use of that. I switched from Perspective to Parallel View and then selected view from the Left. I used the Tape measure tool to double click the vertical lines formed by the corner of the Engine Room Hatch and the Skylight. This showed me that the cowl was too large as it overhung both the skylight and the Engine Room Hatch.
EngineRoomCVFit_3I then hit ‘S” on the keyboard which invokes the ‘Scale Function’ in Sketchup. You have a series of handles spaced around the object by which you can scale it depending on which handle you grab. Using a corner handle and you can – “Uniform Scale around Opposite Point”.

I scaled until the cowl fit within the dashed lines indicating the corners of the hatch and skylight.

EngineRoomCVFit_4I then duplicated the cowl ventilator three times and spaced them on either side of the skylight. I also used the Dimension Tool to find out what the diameter of the cowl was – 0.818 in.
Duping, Scaling and Re-Scaling
HatchesCVFit_5I duplicated one of the Engine Room Hatch Cowl Ventilators and scaled it a little larger and stuck in on top of the Boiler Room Hatch .. then duplicated that and moved it to the other side.

I wasn’t happy with the results. The darn things were just .. too big. They fit within the confines of the hatch corners and the skylight and .. overwhelmed the hatches. So .. no problem. I scaled each set down some until they “looked” right to me.

I ended up with the larger cowl ventilators with a 0.874 inch dia. cowl .. and the smaller set with a 0.711 inch dia. cowl. Respectively .. in O scale these would be 42 inches and 34 inches diameters.

The final picture is only good as far as it goes in respect to the footprint of the hatches. The heights are only approximate – placeholders. The same can be said for the cowl ventilators .. the heights are strictly dependent on clearing objects in front of them so they get a good draw.

So – what’s the point?
I could have simply said .. “I need two cowl ventilators with a cowl dia of 0.874 inches and 0.711 inches. I thought that watching how I came up with those numbers might be helpful .. that it shows how when using Sketchup the various components and can be imported, moved around, scaled, duplicated, re-scaled as needed. They are simply virtual legos. 🙂

I now return you to creating the cowl ventilators.

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