Aerotow hook question

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harry curzon
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Joined: 21 Jul 2018, 09:32
Location: Cheltenham

Aerotow hook question

Post by harry curzon » 03 May 2019, 07:49

I am building the Charlesworth K-18 4 metre. I have a Multiplex tow hook to put in the nose. But I am concerned about whether the nose structure will take the towing forces, especially any snatches of the cable. The tow hook would be glued into the balsa nose block which is glued to the nose ply former which is glued to the ply keel and balsa stringers, and the nose sheeting. My worry is that the force or sudden snatches, would break the front ply former away from the keel and stringers.

Is this a real problem or have others got experience of this type of structure and had no problems?

john greenfield
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Re: Aerotow hook question

Post by john greenfield » 03 May 2019, 08:04

Hi Harry
With a model like the K8 the towing (and snatch) forces are not that high and if the model is properly assembled with good glue joints there will be no problems at all with the structure by mounting the tow release in the nose block.
Do ensure, however, that you put a good servo on the release that will work with a pull of at least twice the model's weight.

AEB
AEB = Aeronautical Energiser Bunny (with thanks to CW)

John Vella
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Re: Aerotow hook question

Post by John Vella » 03 May 2019, 08:56

Harry, I have had many years of aerotowing with a Cliff Charlesworth K8 with the same structure and there are no problems. As John G mentions the weak link can be the servo. Put your "best" servo on your release. Regards John.

harry curzon
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Location: Cheltenham

Re: Aerotow hook question

Post by harry curzon » 04 May 2019, 09:27

Another K- 18 question -
The fuselage is very flexible, if I hold the centre section I can twist the tail by a lot with little force. Will fabric covering stiffen that sufficiently or should I sheet the rear fuz? Or just add more diagonal braces from the centre keel at one former to the top outer stringer at the next former?

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RobbieB
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Re: Aerotow hook question

Post by RobbieB » 04 May 2019, 10:52

Harry, the fabric covering on the fuz will stiffen it up just fine. The bracing already shown on Cliff's plan is sufficient. When I did my K8 I copied Cliff's fuz design at the rear and it was ok.

Just make sure that when you are covering you don't accidentally 'fabric in' some twist - both while covering and later when you shrink it.

harry curzon
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Joined: 21 Jul 2018, 09:32
Location: Cheltenham

Re: Aerotow hook question

Post by harry curzon » 04 May 2019, 11:44

Thanks Robbie

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