Castable, Strong, and Light Weight Alloy?

J.McDonald Knives

J.McDonald Knives

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I'm wanting to make a knife with a handle that will float. Blade will be about 1 1/4"x3/16"x5" bird and trout style. I want to make the guard and pommel out of it. I am doing a short hidden tang about 3/4" long and about 3/4" wide. I need the pommel to also be as strong cause I am going to cut out a wrench for bowfishing tips. I need to be able to weld that alloy to steel tubing. I also need to know what I can fill the handle with to make it float. I plan to wrap the handle with neoprene or thin rubber. I want to also make finger grooves in the steel tubing by heating it up and pounding in the grooves. Thanks for the help.
 
the steel tubing will collapse if you get it hot and beat on it. I think might be able to cold form it if you fill it with sand and cap the ends. The only light weight easily castable alloy I know is aluminum and it won't weld to steel. Why not use aluminum for the entire handle, and have the blade end with say 1 1/2 of 3/8 or 7/16 nc threads and thread and dbl nut the handle on. Have the handle hollow with a threated but cap.

That girl must be keeping you busy your post count is not climbing very fast.
 
Even on a stub or stick tang knife, blade dimensions like that will require a substantial handle in order to float, especially if you put a wrench on the other side. A bird and trout knife would usually be 1/2" wide, or so, with much thinner blade stock, .095" or maybe 1/8", imho.

As opposed to hammering in your finger grooves, you might consider building them up with fiberglass, this won't add much weight to the handle and will probably be easier to make it look right. Don't know what I would do to make the handle float, because I would want to put the floating mechanism at the very butt of the knife. This will be considerably more difficult with a wrench stuck in there. I would consider a floating sheath system with a lanyard to keep the knife in my hand.
 
Jacob.. I did a quick calc for interest sake based on steel blade approx 125mm x 2mm x 20mm with handle of aluminium tube 30mm diameter and 2mm wall thickness. Assuming no other weight additions such as pummels etc and assuming air is sealed in handle cavity, this gives a knife with an average relative density of 1.147, compared to waters relative density of 1. Blade makes up 45% of total

Its a big challenge you set yourself up for! Maybe Ti blade is the way to go or go with Acrids suggestion of floating sheath and/or lanyard.

Using the cavity for storage will make things very much more complicated.

Good luck with it
Lang
 
I was just pointing out that a bird and trout knife is usually narrow and thin. Sort of like a shorter, stiffer version of a fillet knife. You may not want a big knife for small game like many birds. A lot of folks don't even use bird and trout knives anymore, a pocket knife or paring knife can work fine. None of this is to say you can't use something wider and thicker, just that it's not what comes to mind for that style knife.

I would think you want a small, light knife that can cut a fish open. Cutting an arrow out of a fish is no different than cutting flesh, you're not cutting through the head or shaft, you're cutting around it. Any reasonably heat treated knife with a good edge will be able to withstand these rigors.
 
ib2v4u said:
That girl must be keeping you busy your post count is not climbing very fast.
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Actually its not a girl keeping me busy unless you consider my bow a girl. :D I've been doing a lot of bowfishing lately and also going to stay with mom for a few days at a time helping her finish fixing up grandpas house so that she can sell it. I'm just addicted to bowfishing right now and because of everything going on I haven't worked on a knife in a long time. I plan to work on a knife again once I move back in with mom or after we sell my property and grandpas estate and move down to the coast.

The alloy doesn't necessarily have to be castable but just needs to be strong and light weight. Not looking for anything too expensive because this knife can't be worth more than $150-$200. The blade i need to be 4"-5" and strong. They want serrations on it so that they can cut rope and line quicker. They need it to float and also need the wrench for the bowfishing arrow tips. I want to add a no slip grip to it like rubber or neoprene. Any advice on how I can accomplish this better?
 
Sooooo, You say you've been pulling it a lot lately.... (the bow that is)

The knife you are describing is not likely to work in any real way.
Everything that goes into making it is heavier than water. The lightest thing to fill the tube with is air, next is urethane foam.The blade could be Titanium. Have you thought about cutting a slot in the blade itself for the tip wrench?
You could make the tube from aluminum or titanium. The finger grooves could be ground in and curved pieces of metal heliarc welded in to make a shaped handle.
This knife won't be cheap, and may not float unless the handle looks like it belongs on a camp knife. It also is beyond your equipment and abilities.
The idea sounds good, but is not feasible.
Stacy
 
Here is what you could do. Make the knife with the hollow handle, but instead of trying to make it float use a floating butt cap and fill the handle with line and use a water soluble glue for the butt cap, so if you drop it the glue dissolves in say 30 minutes and the butt cap floats to the top with the one end of the line and the other is connected to the knife. which would hit the bottom blade down butt up.
 
I might do the wrench into the knife blade itself which would cut down on weight. I would make the handle out of thin steel tubing and fill it with the foam and cover the whole handle in either neoprene or rubber (whichever will be lighter) and attach the blade to the handle by welding it to the top of the handle and then put a pin in thru the handle and blade and then spot weld the pin to the blade and to the handle. Do you think that would work?
 
ib2v4u said:
Here is what you could do. Make the knife with the hollow handle, but instead of trying to make it float use a floating butt cap and fill the handle with line and use a water soluble glue for the butt cap, so if you drop it the glue dissolves in say 30 minutes and the butt cap floats to the top with the one end of the line and the other is connected to the knife. which would hit the bottom blade down butt up.
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only problem there is that you would have to keep the knife dry all the time and if you are bowfishing (never done it my self so i cant say for sure) i assume you get just a little wet

-matt
 
SR_matt said:
only problem there is that you would have to keep the knife dry all the time and if you are bowfishing (never done it my self so i cant say for sure) i assume you get just a little wet

-matt
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It will get wet a lot as well as covered in fish slime.
 
I was going to suggest the spanner in the blade in similar arrangement to a gut hook but closer to the handle, but Stacy beat me to it! It should save a fair amount of weight.

Lots of guys with some very clever ideas on this site! Whether they work or not they are still good concepts.

I think your best filler for the handle would be fresh air. Foam will just add weight with negligible structural gain. Just make sure the whole cavity is sealed. With a thin walled steel tube make sure the user doesnt have a super powerful fist grip.

Lang
 
I've got only one thing to add to this conversation....

IF YOU PLAN TO HEAT AND FORGE TUBING DO NOT CAP BOTH ENDS.

If you take a tightly capped piece of tube and put it into a forge it may very well blow up on you.

What you want to do is whittle down a plug made of wood and drive it into the end that sticks out of the forge (if you intend to hold that end with a hand). That will keep the flame from shooting up the tube.

-d
 
Floating kives are not new....I remember owning a fishing/diving knife made in the 60's which had a cork handle .............You could use cork in the same way as using leather spacers, stacked on top of each other..the bolster/guard could be made from wood....maybe cork flor tiles?...Study some Scandinavian handle designs and you may find an answer there somewhere as they have been known to use light materials like cork amd balsa woods for fishing knives....but weldomg a wrench on the end may be a problem!
 
When nI used to do a lot of diving, I found that the floating knives would always be at the bottom, point first, with the handle acting as a beacon. After you make the knife, consider a lanyard with a real float on it. It might look a bit funky, but it might also make it really float.

Marine stores sell floats that are made for car keys. They work. You could probably find a larger, but tasteful, styrofaom float that would do the trick.

One guy I knew had a fancy life ring made of wood for his keys, in case he dropped them. Being the yachtie type that he was, he had the ring made from teak. Teak doesn't float, nor did his keys when they went in the drink.

Gene
 
If you take a tightly capped piece of tube and put it into a forge it may very well blow up on you.
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Hot damn! I'm gonna hafta try that!

I gotta wonder if my gas forge body is strong enough to contain a little explosion...
 
Dan Zawacki said:
Hot damn! I'm gonna hafta try that!

I gotta wonder if my gas forge body is strong enough to contain a little explosion...
Click to expand...

And in true Redneck style...his last words were:

"HEY YA'LL! WATCH THIS!"

Seriously, it's a potentially VERY bad thing.

-d
 
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