Crazy concept? Wood/aluminium laminate...

[Agar4Life]

Hey guys,

I'm planning a project gun and have a nice bit of teak in my possession...
However I'm rarely one to do things the normal way, so I want your opinion on a crazy scheme...

What if you were to make a more or less typical teak laminate gun, but with a couple sheets of 2 or 3mm aluminium running down the length of the gun.

I don't think adhesion would be a problem.
You drill some holes and rough up the metal surface, and with the correct epoxy you can get a bond that will break the wood before separating.

Weight might be a bit more of an issue, but surely, not how bad could it be? It's only a thin layer of aluminium...

Does this sound like a good idea? Bad idea? An interesting idea, at least?
Is it trying to solve a problem that isnt there?

Your thoughts are most welcome!
Feel free to shoot this right out of the water (no pun intended) - if it's a dumb idea.

 

[sgnips]

i'm not a spearo, but looks cool, at least for the eye
hope you'll make it (and post pics of course)

 

[-Paddy-]

What is the purpose of using this aluminium sheets?
Have you got any drawings of your project?

 

[Agar4Life]

Well the idea is that it would stiffen and reinforce the structure, particularly to twisting motions. It would prevent warping over time, too.

But as I say, maybe this is trying to fix a problem that ins't there - maybe there isn't too much problem with this on a typical euro gun.

No drawings yet, still very much in early planning phase...
My idea is essentially to put two or three layers of aluminium amongst the teak (vertical laminations).

If you wanted to get really crazy you could even put a T or a U section aluminium bar amongst the laminates and start really turning into a hybrid aluminium-bellied woody gun.

I'm in two minds as to whether it's really a good idea... but thats part of the fun, isn't it!

 

[foxfish]

The main issue would be balancing the gun, teak is pretty dense to start with.
If you were building a block design (American) mid handle then the alloy would not be an issue but if you want a sleek Euro design it will probably sink like a stone.
I have built several guns incorporating an alloy T section.

 

[Agar4Life]

Yeah, I agree, Foxfish.
Weight was my main concern, alongside the pain of shaping it...
Weight is an issue, especially when you put any hardware on it (SS trigger units, handles, anchors, reels, etc.etc.).

The only counter would be to make cavities in the non-stress bearing regions. The muzzle, handle, tailstock, etc.

Carbon fibre sheet might be an alternative, but a lot more costly isn't it?

I've still not managed to convince myself that it'd be that much of a benefit to structure...
Think you'd get a real difference in strength?

 

[foxfish]

This might interest you http://forums.deeperblue.com/diy-homemade/72837-105cm-enclosed-track-composite.html

 

[Bill]

I've had success gluing aluminum to aluminum but when I glued oak or cherry ? to aluminum on a speargun it came apart. The good news is, it took over ten years. An expert said that the difference in expansion rates when the temperature changes was the cause. Oily wood might be even faster. Something to think about.
P.S. The through holes sounds like a good idea.

 

[chipinga]

If you are looking for strength I would consider introducing kevlar strips into your laminates. Aluminium would be difficult to shape unless you had a particular profile laser or CNC cut for you and you shape your timber to the aluminium just as you would on a alloy handle.

You could secure the alloy between two laminates of teak by countersinking stainless screws through the teak and glueing with epoxy (I use West systems or Megapoxy) then you could hide the screws by laminating teak over either side....so you would have teak, teak, alloy, teak, teak.

I don't think alloy would offer any advantage other than possibly the cool factor.

I have recently made some timber guns that have been tripple wrapped in carbon cloth and the effect is very nice and really stiffens the gun, I have enclosed track for accuracy and very quiet.

 

[Tin Man]

The main problem that I see is different thermal expansion. Aluminum grows more with temperature than any other common metal, and wood grows very little. Depending on the species, wood can change with moisture, however, while alumium does not.

If I wanted to stiffen a wood gun, I would use carbon fiber, as it is very stiff in tension while not crazy heavy. It cuts and sands reasonably well, whereas Kevlar is tough and just fuzzes up a lot when you try to sand it. You end up sanding away the epoxy, and leaving broken fibers.

 

[-Paddy-]

Probably we should ask, what sort of gun you looking to build?
In most cases properly laminated teak is strong enough for most gun designs.

I don't see a problem in using aluminium to reinforce the structure, but the question is if it is really necessary? Maybe using some other material would be a better solution and cost less effort or even simplify the design and the build.


Chipinga, is the gun on the picture the one you have build?

 

[chipinga]

Yes it's my own design and I build them.

Results so far have been excellent.

You can see a few more on my Facebook
Ace spearguns Darwin

 

[chipinga]

When you get to know how to work carbon fibre it it makes for very nice guns and may well be cheaper and easier, stiffer and lighter than aluminium.

Just a thought...

If you do make the gun post some pics..

 

[Agar4Life]

@Foxfish - yes I had seen your enclosed track gun - stunning. Looks like the Formula 1 car of spearguns.

@Chipinga - that is a seriously nice looking gun.

@ Paddy - In terms of the gun itself, I was thinking something fairly standard... ~100cm euro gun. Probably open track.

So yeah, I think I have pretty much thrown out the idea of aluminium laminate...
CF still sounds like a really fun idea to throw into the mix. Having some pitch black lines running down the laminate would be very cool.

Does anyone know where you could buy Carbon fibre sheets? Not the fabric, I'm thinking like 2mm thick sheets...
[EDIT] I found some for sale - that s#¤t is crazy expensive... I'm gonna stick with plain ol' wood HAHA.

Totally different question.... Has anyone used Devcon steel epoxy in a speargun?
It's not for laminating - more for gap filling and bearing surfaces.
You could make form fit barrel channels as hard as steel (lighter too)...
It' wouldn't be up to much flex, but its one of the most compression resistant composites out there...

 

[chipinga]

@Agar4life, try looking at the model aircraft shops, they usually sell carbon fibre sheets.

Or you could make your own by cutting several (4+) carbon fibre cloth stripes and laminating them together on a flat substrate such as 19mm MDF putting a layer of gladwrap between the MDF and carbon laminates and clamping them together.

Next morning...bingo you have your carbon fibre sheet ready to go after you trim to size.

 

[scallywag]

I'm just about to start laminating my wood/carbon hybrid gun.I'ts going to slightly different but the principles are the same.Why use carbon in sheet form? can you not just put layers of cloth between the wooden laminates and clamp as normal?

 

[-Paddy-]

I’ve heard a lot of good opinion about this method. It looks like the easiest way of reinforcing wood laminate with CF.

 

[Agar4Life]

@Scallywag: Erm... I ... don't know.... :S sheet seemed to be the best way... but that's without really thinking...

Wouldn't it be best to tension the CF as much as possible before setting it?
Since we want rigidity down the length of the gun, perhaps you could stretch the CF cloth. Tension in the CF will mean that there is absolutely no play - so there will be less flex!

How I imagine doing this:
1. Stack your laminates as per normal (opposing wood) with the CF cloth either side of the central laminate(s) but with a good few centimetres of CF sticking out of the front.
2. Clamp only the tail end (towards the butt) as close to the end as possible
3. Pull evenly but strongly on the CF, from the nose... clamped between blocks of wood or something...
4. While CF is tensioned, progressively add clamps up the body of the gun (will require a second pair of hands) until the whole gun is clamped... then you can release the CF.
6. Allow to harden fully before releasing

Maybe I am reinventing the wheel here, and saying what you all already know.

 

[foxfish]

You can jump up & down from a chair on top of most laminated wooded guns & they wont break so I think adding carbon strips in between the wooded lamination's is more about style.
Once you have built your first gun, you want to build something better or different - nothing wrong with that of course I have been doing it for 35 years LOL

 

[Agar4Life]

@Foxfish: THAT'S what I wanted to hear... good to know.
Hmm... in that case I'll probably just keep it simple...

I like the wood look and I'm not gonna spend all this money on teak just to hide it under carbon fibre...
Plus, I'd probably only bugger it up, anyway...

Thanks all for the useful discussion! It's helped things take shape in my head...