| SE5a - another approach
Meanwhile I have visited the Shuttleworth lot at Old Warden. Give an extra contribution to the funds and you can go “back-stage” and talk to the workshop guys doing the work and photograph it all. Fascinating. No wings on yet but hopefully before the end of this month. I learned a lot, saw a lot. To me, most importantly, they are restoring to design level not operational aircraft level so it will be without battle damage or “hangar rash”, no attendant rust, holes, poor maintenance and (frequently) poor craftsmanship such as out-of-line stringers, sloppy covering, messy painting etc. That is what I intend, build what it should be not what it became. Well, that is what I hope. Am I good enough?
But I have problems. For example Greybeard talks of 5degree dihedral but others say as little as 3degrees. The Simmance plans have no front elevation and no mention of the dihedral but the wings are attached to the centre section by tubes in both parts mounted on to a rod to hold them together. There are holes in the first 3 ribs of all wings and centre sections to set the positioning of the tubes so by measuring the downward deviation of the holes and applying a bit of trigonometry I calculated Simmance drawings as 5degree. Actually I always measure by wing tip distance above the horizontal, calculating (more trigonometry) from the quoted angle.
I have obtained drawings of front elevation of full-size designs and by similar calculations they all show 5degree. I shall ask Pretoria and Shuttleworth because Simmance plans have a cock-up. Yes, hole positions giving 5degree – but the ones on the wing do not align with the holes on the centre section! In spite of spending hours studying the drawings I did not spot this until I had built both a centre section and a wing.
And again, wing (and stabiliser) angle of incidence. Always quoted as a deviation from the thrust line – but where is that? Some say (sensibly I think) the line of the prop shaft, the majority say prop centre to stabiliser leading edge and others (including Simmance) say prop centre to stabiliser/elevator trailing edge – well, this stabiliser has variable incidence so that makes sense. But was this true in 1916? Well, Shuttleworth guys say that the thrust line on virtually all WW1 aircraft is the line of the top longeron. The Simmance definition works out to be exactly parallel with that longeron line so I have no problems – except that reproductions of full-size drawings show different positions depending upon whether the aircraft is fitted with Hispano Suiza or Viper engine! Actually the Viper engine line, which is to be my version, creates a line which is parallel with the upper longeron so there really is no problem.
But there is still a question. Apparently the angle could be varied by the pilot in flight, accounting for the fabric crinkles seen on many actual WW1 photos. Apparently the pilot could lift the wing T/E which reduced the angle of incidence and caused the fuselage fabric crinkle in that area. But most “wrinkly” photos were taken on the ground indicating that the pilot set up less incidence for landing. Did he? If so, why?
Last edited by LINNEY; 21-11-2007 at 11:17.
|