Hi
While the Avenger/Tarpon had power folding, as far as I can find the Hellcat had manual folding like the Wildcat/Martlet. Indeed the Grumman 'sto-wing' system is very similar to the earlier (1937) Blackburn Skua folding system:
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The Supermarine system for folding wings proposed in 1939 for the 'Sea Spitfire' (from 'Spitfire, The History' by Morgan & Shacklady) also appears to be similar to the later Grumman system:
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Or the system of the two-seat N 8/39 proposal (from same source):
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These were also manual (as they had been on bi-planes from 1912 onwards). As has been mentioned power folding did increase the weight of the system and it became more viable and necessary as aircraft got heavier and had more engine power.
Mike