Does anyone know how this was done?
On moving from the DH60 to the DH82 Tiger Moth, the wing was sweptback by shortening the rear spar. This left the ribs and aileron gaps misaligned to the airflow, but this was considered unimportant on a 100mph trainer.
On the Hart Trainer, where the sweepback was reduced by two and a half degrees, was the rear spar lengthened or the main spar shortened? Is there a difference in wingspan quoted? Was the wing redesigned to align the ribs and aileron gaps with the airflow or not?
Thanks for any help.
By: Graham Boak - 4th June 2010 at 20:01
The 5 degrees is the sweepback on the normal Hart wing, so if that was retained on the trainer then they used the wing outer panels unchanged and put up with half that as a misalignment.
I’m still not clear whether they pivoted the wing about the front spar, thus needing to do something about the rear opening up a gap, or pivoted about the rear spar, thus needing to shorten the main spar. The former seems more likely, but if so did they realign the mating surfaces by extending the rear spar inside the wing, or just put some bridging structure?
By: chumpy - 4th June 2010 at 19:52
Hi Graham…from memory yes the basic wing structure was as per a normal Hart. Though looking at my photos I find that it was back in 1992, so alas my brain cells cannot be 100% positive.
However I am pretty sure that all the ribs had a 5 degree offset in relation to the spar booms. Attached is a shot of a portion of the Trainer wing, sticking a protractor up against the second rib in from the left seems to confirm the 5 deg, ( bit Mickey Mouse, I realise )!
As previously mentioned modified pick up fittings on front and rear spars / mating surfaces. Though thinking about it, the sweepback change only on the upper wings and NOT the lower as previously stated.
Sure I had a photo of the fittings..just finding it.
Chumpy
By: Graham Boak - 4th June 2010 at 13:10
Thanks. So you think they didn’t bother with any realignment of the main wing structure, and restricted changes to the mating surfaces? Re this pick-up fitting: I presume you are referring to the main spar? In which case there would need to be a small extension to the rear spar. This could be an addition to the existing wing structure or by realigning the inboard end-rib. Is this ringing any bells?
By: chumpy - 4th June 2010 at 11:52
Several years back I dealings with things Hawker Bi-plane, had access to one of the RAF Museum’s Hart Trainer wings.
The change in sweepback acheived by means of modified wing pick-up fittings. These a chunky steel fork-type fitting that plug into the ends of the spar booms, those on standard Harts having a 5 degree offset between lug and body..those on the Trainer 2-1/2.
Seem to recall that the inboard end-ribs of both top and bottom wings were a bit different due to the change. Otherwise the rest of the wing bog-standard. ( I stand to be corrected on this)
somewhere I have some photos!!
Chumpy.
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June 4, 2010 at 11:18 am