Need help. Building a gun.

[lawstraljan16]

Ps: from last spear tab to (nearly) half of barrel underneath the gun

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[Jegwan]

I don't think I understand then - sorry if I'm a little slow - but how can you have tabs for more than 300% when the rubbers are 42cm and the maximum length they can stretch is 127cm (minus the wishbones)?
Jégwan

 

[lawstraljan16]

I dont think your slow, I might be wrong in my thinking?

I cut the bands to 42cm which is 300% of the 127cm. The 127cm I got from the last anchor on the shaft to almost half way on the body underneath the gun. Then every 7.8cm I added more tabs which equals another 20%. Cant this be done? I added more tabs to adjust strength from 310% to 380%. Am I wrong?

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[Jegwan]

Ahh... our posts crossed. Now I understand - 42 cm sounds fine then. You might want to make them a little longer to be on the safe side. You can always shorten them.
Jégwan

 

[lawstraljan16]

Hehe. Damn I thought I went wrong! Ive got a lot of extra old bands so im using old ones for now to test out.
So are those tabs right or will they be useless?

Sorry for the awful pic but I drew by hand on my mobile

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[Jegwan]

Thanks for the drawing.

So the maximum stretching length on your gun is 160cm. If you want to be more safe you can cut your bands: (160 - 6 (wishbones minus space for constrictor))/3,5 = 44cm.

I think that you will find that 3 taps is enough. I suppose that the spear has more than one shark fin.
Approx. 16-17cm between them sounds fine then (127cm + 2X17cm = 161cm)
Jégwan

 

[lawstraljan16]

Sorry for the incredibly bad drawing...

Between the rollers there will be a space of 17mm wide and itll be 30mm high. Will it be strong enough? Or would I have to reinforce it? Im unsure whether itll be strong enough as it is, and if I were to reinforce it itll most likely make the muzzle too heavy? Thoughts? Ideas?

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[Jegwan]

I think it will be ok, but you need to stabilize the wheel axel at each end with at steel plate from the muzzle in front of the wheels. Like this: http://www.contesub.it/public/prodotti/spondine-a-braccio-singolo-244.asp
Jégwan

 

[lawstraljan16]

Yes I have those. I juat hope that the 17mm thickness is enough to not break off!

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[Jegwan]

It won't. The main part (close to all) of the force from the rubber is parallel to the barrel/spear and it is working on both sides. That’s another roller benefit ;-)
Mine is approx. 20 X 30mm.
Jégwan

 

[lawstraljan16]

Ah ok great thanks Jegwan.

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[lawstraljan16]

Minor tinkering to be done to the trigger mech and all that is left is forming the shape and sanding it down. Almost there!

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[lawstraljan16]

Ill be forming the gun tomorrow and wont stop for the next 4 days until its done. So laminating the gun will be done soon too.

Thoughts about using teak oil?
Epoxy resin? Polyurethane...? Others? Goods and bads on them. Thanks

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[lawstraljan16]

Handle epoxied on, shape cut, now just a lot of sanding down to do and rounding it up.

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[foxfish]

The most satisfying bit for me, not necessarily the nicest bit though!
Looks very accurate & well made

 

[lawstraljan16]

Thanks foxfish. Im trying my best. Quite a few mistakes made but ilk make sure not to make them on my next build.

I just glued the handle to the body, and ive just noticed I used a 2:1 mix when I was instructed 3:1... did I f*** up big time?

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[foxfish]

It might set ok but wont be max strength... bummer!
I have done similar several times & that is why I try to get equal push mixing pumps, west systems do pumps but it is still 4 pumps to one pump but international use one pump to one pump.

 

[lawstraljan16]

Should I go see if I can remove the handle and do it again then? Not being max strength scares me

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[foxfish]

Yeah I recon you should try to mate... sorry but you will never be happy otherwise.
If the glue has set you could put a couple of dowels through the joint.

 

[lawstraljan16]

Luckily I was able to get it off, and wiped off most I could of the epoxy off with a blade and redone it, feel much better now hehe. Thanks will post better pics with better lighting tomorrow once ive sanding all (most) of it down.

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