Grapple Hook

[Bayshore Forge]

Hey all, 

so long story short I told a friend I'd make him something if he gave me a pile of scrap metal. He said he would be interested in a grapple hook. Initially I thought, SWEET! Now before I start I have some conflicting theories in my head.

I'm thinking spring steel because I'm scared mild might snap or bend uselessly if he ever used it for anything. So then I'm thinking harden it, but where to temper it so it doesn't break? The arch of the hooks?

Should the arches have a round cross section or should there be a rib on the top for support? 

HAS ANYONE ACTUALLY MADE ONE TO USE BEFORE? the shape cosmetically I'm confident I can produce, but I'm worried about function. 

Thanks for your time,

Brent 

PS NO he's not a ninja. He's a commercial fisherman so I guess he just likes all hooks and nets. 

 

[DSW]

I made one years ago in metals shop. It was out of mild steel, probably 1/2" or 5/8" round bar. But then again we were probably 12 or 13, so we really didn't weigh anything much. We used it to climb some small banks/ cliffs, probably all under 15 feet.

 

I've made a bunch since then, but not for climbing. They were for use wreck diving or fishing off shore, to grapple the wreck. There's two schools of thought on those. School #1 is to make them dirt cheap so if you loose it it's no big deal. Many times guys like 3/8" rebar for them. It's enough to hold a mid size boat, but in the event you can't get the hook to slip, you can power back on the hook and chances are the thin tine will bend and release the hook. 2nd group likes stout hooks often made from stainless. I've made them out of 5/8" stainless round bar. They were mostly used on bigger dive boats. They'd drop the hook in the sand up current of the wreck and drift into the wreck to catch an edge. The mate would go down, then chain in, and later free the hook and float it up on a lift bag.

[Charles R. Stevens]

I would think any of the "spring steels" wold work, 4060 or something like, pretty simple to quench and temper. A bear to forge weld with out some "magic". Certainly for strength wile keeping the weight down one might consider a "teardrop" or "T" cross section. 

[Frosty]

A lot depends on what he needs it for. If he's just snagging a float line like you see on Deadliest Catch then it doesn't need to be all that strong say 3/8" stainless and the tines don't really curve they're simply bent on about a 3/4" radius. Straight shank, bent say 120* (just guessing there) straight tines with tips rounded on the grinder.

Snagging wreckage requires tines arched to self set and pointed but not sharp. It also needs to be a couple times stronger than you think it'll need to be and more importantly cheap enough you don't mind losing hooks in wreckage.

Climbing a tree needs to either loop over limbs or be sharp self setting tine profiles. Those would be two different types of grapnels and depends on whether you care about damaging the tree.

Climbing castle walls? There are profiles that will lock against a corner IF the line isn't under tension in the same plane as the rope eye on the grapnel.

I believe that just about sums up my knowledge about grapnels.

Constructing them is a little different. Use 2 pieces of stock, one 2x as long as the other. Grind or forge the points as desired. Bend the long piece in half over a mandrel to size the line attachment. Weld the second piece in between the halves of the first piece. DON'T make me TELL you NOT TO WELD THE TINES TOGETHER!! Just weld them at the shank. Now heat all three, bend the singleton one way the other two the other way. Spread the pair and adjust till they're at 120* spread and shine it up.

Learned that in Jr. high school metal shop 1. All the boys in shop class seemed to think we just HAD to have a grappling hook, Dad took mine to keep for me. He probably didn't want me poking a bunch of holes in tree limbs and falling on my head.  Dad was a smart guy, maybe had a vision about my head and a tree.

Frosty The Lucky.

 

[Alan Evans]

As it is for underwater grappling,  but without  one DSW's divers around to release it from an unliftable snagged object, a second ring at the tine end for a release and recovery rope might be useful.

Alan

 

 

[DSW]

Good point. I should have mentioned that last night as well. The end of the rope was attached to a loop at the "hook" end. The chain rand down the shank and then was zip tied or tied with some thin cord to the loop at the shaft end. That way when you pulled, you'd break the zip tie and then the chain would pull the tines free.

[Alan Evans]

2 hours ago, DSW said:

Good point. I should have mentioned that last night as well. The end of the rope was attached to a loop at the "hook" end. The chain rand down the shank and then was zip tied or tied with some thin cord to the loop at the shaft end. That way when you pulled, you'd break the zip tie and then the chain would pull the tines free.

Ah that would work well...you could set the break-away load with the number or size of cable ties.

I was trying to figure a way of doing it with one rope...but the best I got to was a heavier dragging lifting rope and lighter release cord which could operate a release catch/yank a slip-ring off the shank so that the main rope then pulled the tines backwards.

Alan

[SmoothBore]

If you Google "slip-ring grapnel", you should get plenty of pictures of "Danforth" style anchors, designed to disengage when the anchor rode is pulled in the opposite direction of the original "set".

This design would be easily applicable to your project.

 

 

[Bayshore Forge]

I am constantly astonished at the quantity  of quality thought I get whenever I post a question. Thank you guys so much, these answers should give me plenty to think about for AWHILE! Haha. 

 

Brent 

[Frosty]

I don't know how well a slip ring grapnel would work if snagged so much depends on being ABLE to draw back to release it. Using a second line to free grapnels works well in most cases, especially if the tines are bent so as not to snag drawing back.

I hadn't heard the term, "Dansforth", for the slip ring type release. Various anchors were another group of off the shelf high school shop projects. I made a hinged fluke twin shank, Dansforth, anchor for your boat. I ended up selling at least half a dozen to other guys with boats after demonstrating that silly LITTLE 20lb. anvil could hold their boat against anything their engine could do but released easily on any bottom including a known snag.

Frosty The Lucky.

[arftist]

There are many different style and type of grapple used by fishermen. To truly help him you must find out his use for it.

Ideally he can show you a proven type or design. 

I have made grapples from the small hand thrown ones Frosty describes to monsters weighing hundreds of pounds designed to retrieve lost fishing dredges weighing thousands of pounds.

Find out the intended purpose.