Stow-flat grapnel anchor - how ?

[electrosys]

If you were any good at solving those bent wire puzzles as a kid - take a look at: http://www.youtube.com/watch?v=3FJp6Ur5jeE and see if you can work out how those two halves of a grapnel anchor are fitted together.

I've watched it a dozen times, even freeze-framed it - and I still don't see how it's done.

Touch of the Paul Daniels ...

 

[MontyMariner]

The crown on the 'free' half is not joined to both flukes, so the bottom of the shank on the shackled half can be pushed down the middle of the 'free' half shank.

EASY!

 

[electrosys]

I did wonder about that - but that would imply that those two flukes (on the 'free half') would be unsupported at the crown - making them much weaker (more flexible) than the other two ?

I like the basic idea - but maybe a couple of nuts and bolts would make for a stronger design ?

 

[prv]

Can't see how that's any better than the traditional folding grapnel in which a collar slides up and down the shank. Stows a little flatter but much wider, questionable strength, and very little fluke area to hold it in sand, mud or gravel.

Cheap to make though.

Pete

 

[Seajet]

Folding grapnel

While I'm a fan of the folding grapnel for the right jobs ( holding on weedy rock in emergency, use as an angel in folded state ) nb it does rely on the strength of the fluke pivot pin/s, ie not very much for protracted or heavy duty use.

 

[electrosys]

My main interest is in using these as demersal long-line anchors - at the moment I'm using a couple of classic folding grapnels with the slide-down collar but have found that the collars have an annoying tendency to rotate and fall away - so at the moment they're being held in place with a rubber band (ex inner-tube).

I need at least half a dozen, and was going to make up some DIY jobs from rebar, but they're bulky and space on the boat is at a premium - it was while looking for alternatives that I came across the 'Paul Daniels' video ...

Think I'll make-up a few along similar lines to those shown in the video, but smaller and more substantial, and with something meaty to secure the crown. Think I'll be welding some 'arrow heads' onto the flukes too, to increase the holding grip.

 

[PuffTheMagicDragon]

It could be made using 10mm rod.

• Bend the part with the ring at the crown (part A) in such a manner that the gap between the two straight parts is slightly wider than 6mm. Make sure that the ring part is not too small. I would suggest 50mm to enable the assembly motion described later.
• Weld a piece of rod to bridge the open end of the parallel ‘slot’.
• Make up the sliding part (part B) using the same principle but with no ‘ring’ at the crown end.
• Close the open end of the gap in part B with a short piece of material that is 6mm diameter, say 25mm long, .
• To assemble: One side of Part B is threaded into the ring at the crown of the shackled part and slides down the gap in Part A until the 6mm bit comes up against the closing piece of the slot in Part A.
• The shank of part B is held securely because the 10mm material cannot pass through a 6mm gap.


I hope that this description is clear enough.

 

[electrosys]

Any chance of a diagram or sketch ? You've clearly crystalised a viable mechanism in your mind - be a bl##dy shame to waste it.

 

[PuffTheMagicDragon]

I'll get round to making a sketch and either take a photo or have my son scan it. Not tonight though as I'm about to hit the sack. If I forget, feel free to give me a nudge (e.g. via PM) to remind me. I've become rather lazy.