Adam,you are a sensible chap to consider incorporating washout on the Flair Harvard,here is a drawing that explains just how washout works,whilst dihedral gives lateral stability to your model washout improves dramatically the flight characteristics at the point of the models stall,normally the wing will drop at the tip making slow approaches with elliptical shaped wings a nasty experience,with washout incorporated you can see from the drawing that the wing stalls first inboard thus arresting the stall.
The best way to incorporate this into your Flair Harvard is as follows-When you have laid out the wing leading edge,spars and ribs as per the excellent instructions do not glue them but just assemble dry,next take the trailing edge of the wing and prop up the wingtip half an inch at the end rib at the trailing edge end,so looking from the rear of the wing it has a reflex from the root to the tip,you should now have all of the wing ribs gradually getting steeper towards the tip,ie the washout is gradual and most at the wingtip,make sure that you have placed some polythene sheet under everything as the next stage is important,with everything pinned tight and firmly into position,take a bottle of 'thin' cynoacrylate adhesive and flood all of the joints of the wing,the adhesive will permeate deeply into the joints,leave overnight and remove the wing,do exactly the same for the other wing,just make sure that you have the half an inch incorporated the same otherwise you will have a model that will roll one way all of the time,we dont want any built in aileron effect !
Note that you may need to trim the ribs towards the tip so that thet butt up nicely against the leading and trailing edges because they will be slightly on a slant,just do this as you go along.
I trust that this will explain what washout is and how to incorporate it,best of luck and if you need any further assistance in what to do just get back here.
Note that the drawing shows washout added to the very tip,however gradually incorporating it as per the instructions is far better and as per the way real aeroplanes are constructed,it is sometimes so subtle that you can hardly see anything,but if you have a local airport,take a look at any light aircraft standing at eye level at the wingtip and looking downwards towards the wing root.
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Originally Posted by harris10 Hi Barry,
I am about to build a flair harvard. Can you explain exactly how I build in washout to the wing. Is this like dihedral?
Cheers Adam |
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