[Balloon-makers] basket bottomes

[Ron Cassidy]

Greetings Glenn & Others,
  I've had good success with Marine grade plywood for basket floors. I added a layer of West System Glass on top and bottom. The top, bottom, and sides were all coated with several layers of West Systems Epoxy. 
  For a lightweight floor I would consider honeycomb sandwiched between two thin layers of plywood, all encapsulated in glass or carbon and epoxy. 
  Check out some of the projects and tips at westsystem.com e.g "Plywood Basics". 
  Regards,
  Ron Cassidy

 -------------- Original message ----------------------
From: "GlennADavis.net" <gdavis at glennadavis.net>
> I have seen the recent discussion regarding the materials for a basket
> bottom.
> 
> I am an experienced engineer but very new to balloon design but I had some
> thoughts regarding the recent inquiry about choosing the right material for
> a basket bottom.
> 
> If  I were going to build a basket, I’d either copy one that has been
> popular or go through some design process in an attempt  to improve it.
> Copying a basket doesn’t require much thought but I have some ideas
> regarding a redesign.  Since I am new to ballooning you might consider my
> ideas more an exercise in brainstorming.  Perhaps someone with more
> experience could  give the floor some thought and try to improve it.  Here
> are my thoughts.
> 
> The first approach in designing the floor is to delineate what you want to
> accomplish.  That doesn’t seem so simple to me.  I’m sure there is criteria
> in the back of the minds of experienced people, but I’ve never seen any
> design criteria listed which would be a good basis for input from others in
> a collaborated design approach.
> 
> Possible design requirements might include resistance to puncture, light
> weight, high strength to weight ratio, energy absorbing,  abrasion
> resistance,  easy to slide into a van or onto a lift, appearance, and ease
> in transitioning to wicker sides (if a wicker basket).
> 
> Treated plywood is hard to beat.  Plywood with water resistant glue (what
> used to be called marine plywood) makes the most sense.   If you have
> sufficient armor on the bottom and crisscrossed cables underneath, the
> chances are that half inch plywood would be adequate for dead load. Double
> this for impact loads.  Instead of using ¾ inch  plywood, why not use two
> layers of half inch. Then trim out the edges and add skids.  Skids should
> probably be placed in the direction in which you are loading the basket onto
> a lift , van or trailer floor. Skids should be armored with something
> slippery like Teflon or high density polyethylene. They need not be large or
> deep and any type of material might well be adequate provided it is
> reasonably abrasion resistant or armored with something.   Two layers in the
> floor would allow you to slip in a thin sheet of steel to provide some
> puncture resistance. (I cringe at the thought of being impaled on a sharp
> object that came through the bottom in an unfortunate landing.) Kevlar is
> another possibility.   I would consider the extra 40 or 50 lbs that a 40-50
> guage steel plate weighs, worth  the loss in load capacity for the benefit
> it might provide..
> 
> The crisscrossing of ribs on the underside of the floor (which I have seen
> often) seems to be a bad option except for the fact that you can hide
> crisscrossed cables within them.  It is not appropriate for ribs to
> reinforce the floor or for skids. Structurally it would make sense to run
> any ribs in the long direction however from a loading up point of view it
> might be better to run them in the short direction and if so, they would be
> less strong but strong enough and much more efficient for loading up onto a
> lift or trailer. From my experience with plywood, I would think that except
> for very large baskets, skids are only needed for abrasion resistance, not
> for strenght.
> 
> Could someone experienced list some design criteria, and let’s start getting
> innovative together.  Its time to apply some of the technology we now have
> to overhaul the design of the floor.
> 
> Glenn A. Davis, P.E.
> gdavis at glennadavis.net
> 
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