wonwinglo
SMF Supporter
- Joined
- Apr 18, 2004
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- First Name
- Barry
The subject of fabric covering for aircraft is a complex one,however there is a simple way to understyand how processes and methods have changed over the years,here are a few pointers as to how fabric is applied and ways of improving its lifespan-
Fabric covering first came into being from the days before the Wrights,pioneer aviators used a variety of materials to cover their early flying machines,the purpose of the covering is to ensure that the airframe is not only airtight but gives the best lifting surfaces possible,oiled fabric or boiled linseed oil was sometimes used on early machines,even silk in some cases,however the finest material was a linen produced from flax in Ireland,this tough and durable material has remained a favourite, but phased out today in favour of Stits type fabrics which in some cases are ironed on just like model aeroplane covering,the modern materials far outlast natural fabric materials,the biggest problem being the strong suns rays,fabric will deteriorate very quickly if not protected,for this coatings of pigmented dope is used,usually silver for the base coat and a red oxide coloured interim coat.
Another type of fabric mostly used on gliders and ultra light aircraft is a material called Callico,this has a much finer weave than Irish linen which carries a weight penalty,fabric is made of a weave and a weft which are the machine runs,cut a piece of fabric and th edges will fray,this was used to advantage in the early days ( 1914-18 period) by fabric workers,when the fabric is doped it is possible for this to lift in the slipstream,if precautions are taken then only a portion of the loose fabric will lift,so early fraying was used by the factories and field workers on aircraft,today pinking is used,this is simply a serrated edge which is cut with pinking shears to give a vvvvv type edge,builders of vintage machines need to be aware of the different approaches to fabric work and the exact materials used,recently someone put on e-bay some apparently original rudders for WW1 aircraft,these had modern pinked fabric ! I knew straight away that these were far from original pieces of work,the builder had obviously overlooked this !
Another problem arises with fabric when applied to the wings of an aircraft,due to the pressure on the surfaces the fabric can balloon and lift away from the structure,this actually happened on the first flight of the Westland Lysander when large portions of fabric tore away from the wings,the aircraft thankfully landed safely but the lessons were learned.To this end stringing is introduced,whereby a large needle loaded with beeswax treated cord is threaded around each portion of the wing ribs,the stitches are patiently herring boned into place and then covered top and bottom with strips of fabric doped into place,this effectively stops the fabric from lifting away,it is a long and tedious process that usually is accomplished with two people one underneath the wing,the other on top ! as the long needle is passed to and fro blindly from inside the wing.These long lost skills are all part of the construction of vintage aircraft and you need to get it right if the aircraft is to be deemed airworthy !
To understand how these things are done in real life will help us build our models and to make them more accurate.
Fabric covering first came into being from the days before the Wrights,pioneer aviators used a variety of materials to cover their early flying machines,the purpose of the covering is to ensure that the airframe is not only airtight but gives the best lifting surfaces possible,oiled fabric or boiled linseed oil was sometimes used on early machines,even silk in some cases,however the finest material was a linen produced from flax in Ireland,this tough and durable material has remained a favourite, but phased out today in favour of Stits type fabrics which in some cases are ironed on just like model aeroplane covering,the modern materials far outlast natural fabric materials,the biggest problem being the strong suns rays,fabric will deteriorate very quickly if not protected,for this coatings of pigmented dope is used,usually silver for the base coat and a red oxide coloured interim coat.
Another type of fabric mostly used on gliders and ultra light aircraft is a material called Callico,this has a much finer weave than Irish linen which carries a weight penalty,fabric is made of a weave and a weft which are the machine runs,cut a piece of fabric and th edges will fray,this was used to advantage in the early days ( 1914-18 period) by fabric workers,when the fabric is doped it is possible for this to lift in the slipstream,if precautions are taken then only a portion of the loose fabric will lift,so early fraying was used by the factories and field workers on aircraft,today pinking is used,this is simply a serrated edge which is cut with pinking shears to give a vvvvv type edge,builders of vintage machines need to be aware of the different approaches to fabric work and the exact materials used,recently someone put on e-bay some apparently original rudders for WW1 aircraft,these had modern pinked fabric ! I knew straight away that these were far from original pieces of work,the builder had obviously overlooked this !
Another problem arises with fabric when applied to the wings of an aircraft,due to the pressure on the surfaces the fabric can balloon and lift away from the structure,this actually happened on the first flight of the Westland Lysander when large portions of fabric tore away from the wings,the aircraft thankfully landed safely but the lessons were learned.To this end stringing is introduced,whereby a large needle loaded with beeswax treated cord is threaded around each portion of the wing ribs,the stitches are patiently herring boned into place and then covered top and bottom with strips of fabric doped into place,this effectively stops the fabric from lifting away,it is a long and tedious process that usually is accomplished with two people one underneath the wing,the other on top ! as the long needle is passed to and fro blindly from inside the wing.These long lost skills are all part of the construction of vintage aircraft and you need to get it right if the aircraft is to be deemed airworthy !
To understand how these things are done in real life will help us build our models and to make them more accurate.