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Paper Modeling & Nested Hull


By petehdgs - Posted on 12 January 2013

I have taken a stab at modeling in clay and wood sculpture because a 3d object is very descriptive to the mind.  I want to build a 2 stage, nested, progressive Vee hull as the basis of the Long Coot Amphibian's high speed water handling characteristics. I have some 2D sketches of the step that appear to channel the outward flow of water properly to create lift and separation thus reducing the cantact footprint of the hull to about 25-33% of total hull volume and reducing power required as the boat accelerates to flying speed.  The nested hull has proven difficult for me to duplicate in clay or wood carving (likely due to my lack of skill as a sculptor) so as to create a decent hull form capable of extrapolating templates.  This led me to look for alternative methods of modeling. 

Recently I came across a complex paper cutter in a craft store and I started doing some research on it. These machines are like printers but instead of printing ink they cut paper in complex ways based on the image sent to be printed.  The best of these machines for my purposes appears to be the Silhouette Cameo, a paper cutting machine capable of executing files that you create yourself.  I could spend a lot of time discussing this machine, but most of the reseach is available on line at Amazon.com as customer reviews, over 100 of them. 

Next I started researching paper modeling techniques.  I came across http://paper-replika.com which burried deep in their website is a multiple lesson tutorial on how to create 3D models using your computer, paper, and a Silhouette Cameo paper cutter.  The first chapter of the tutorial is here: http://paper-replika.com/index.php?option=com_content&view=article&id=6256:introduction-on-how-to-design-paper-model-using-computer-software-tutorial&catid=135:tutorials&Itemid=200144

The Paper-Replika tutorial describes a 4 part process for creating 3D shell models. This method is unique but it seems to make sense and it can be adapted to full scale reproduction techniques.  Since the 3D scale model is built up from 2D imgages, it is possilbe to make a paper shell of the final model, but it is also possible to produce scale cut components that can be glued together and assembled just like the real thing, I think this methodology has real uses for us in our amature boat designing processes. 

So far I have downloaded all the software and started learning to use INKSCAPE, a drawing program.  This program has the ability to trace a drawing or photograph from a bitmap image.  It will not trace a JPEG, but MS-PAINT can be used to convert a JPEG to a BitMap image that can then be traced.  This program is extremely capable and complex.  I have learned a lot with the INKSCAPE tutorial, but so far I have only scratched the surface. 

My plan is to build 1/16 scale models of the complex hull and forms and see if this works before spending my money on plywood and lumber.  Paper and glue is cheap and can be made waterproof by painting with thin epoxy resin or wood glue as the model is assembled.  Scale weight can be added to the model in the form of pennies.  Each penny being 25 scale pounds.  The pennies can be used to weigh the structure so that it represents the real thing.  The scale model can then be tow tested in the water by towing it beside a boat.  I think the ratio is 1/4 speed gives the same dynamic performance, so 8 kts represents 32 scale kts.  Once that is done, the same files used in building the model can be the basis for the full scale parts.  I think this will really give me some good brain tools for development of the project. 

Another note: I purchased a used Cherokee fuselage for the tail and control systems.  I have the rudder, vertical stabalizer, horizontal stabalator, control yoke, trim device, pedals and conecting components.  One miracle at a time.  Comment if you wish. 

Have FUN!  Fly SAFE! 
William "Pete" Hodges
N5586F N225XC

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