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Bluewater gun design questions

ShortfinMako

New Member
Apr 1, 2018
2
0
1
31
Sydney
Hi everyone,

After too many engineering conversations and forum trawling I'm getting close to a final design for my Bluewater gun and if you guys could help me get across the line of uncertainty then I can get on with it and post the build

So here it is, I've already got the teak and it will be an 11/32 shaft with 4-5 rubbers, enclosed track, inline muzzle, 60"+ stock, mid handled.

What i havent't decided is:

How much shaft overhang would you run? Reading terry Maas book suggests 18" but that seems like a lot and a lot guns run a lot less and I can't figure out why.

How much should the unrigged gun weigh and if you are just weighing a commercial gun is it 65" shaft or 72"? (770 grams vs 854g + the tip) As I don't know the overhang I haven't chosen the shaft.

And finally, for those of you with inline muzzles, what is the gun barrel visibility like? For example if you have something like a sea sniper do the flat top surface sit the too high? I can easily round it off to accomodate the rubbers and lower the ferrules. This seems to be the a thing a few people mention for some along with vibrating rubbers whilst tracking when reasoning against an inline muzzle.

I would love to here your thoughts.

Cheers.
 

sharkey

Well-Known Member
Nov 22, 2013
306
165
58
On ballasting, I would try to be around the 4 kg for the basic stock for the spears you mention, the heavier the better, but making a gun which displaces 4.5 litres of water isnt easy to make feel responsive in the water. Its the spear which hits the fish , not the gun, if you can get a gun shoot a longer spear well then its like having a bigger gun. When you have four or five rubbers bunched up together they wont vibrate. Why enclosed track? I thought this way of thinking has been accepted as redundant, especially if you are trying to get the most efficiency (which also reduces recoil).
 
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ShortfinMako

New Member
Apr 1, 2018
2
0
1
31
Sydney
hey sharkey thanks for the reply,

4 kg is a lighter than I was expecting. If I had too guess I was going to go 6kg. The length of the spear is really about the overhang IMO, a combination of lateral drag vs tip vis ability and weight/balance at the muzzle.

Looking at sea snipers for example the spear is the same size as the stock so you get overhang equal to the 3" mech + the space behind it which couldn't be more than 5" or 6". Add the slip tip and that's about 12". Andre's on the other hand are a bit longer.

Why do you consider an ET inefficient or redundant? Many top tier commercial guns are still sold that way.
 

sharkey

Well-Known Member
Nov 22, 2013
306
165
58
An enclosed track may assist with loading the spear into the trigger but that is about all it really does if the gun is tunned properly. The idea behind the enclosed track was to stop or control the whip of the spear when overpowered. If the spear is overpowered then as it tries to bend the friction is increased which results in less power, think about trying to pull a bent spear through a straight tube, it will use up some energy. I avoid the whip in spears by having a very slight (one or two millimeters at the most) dip into the track or rail of the gun, this is the same principle used to tune archery gear. As the spear is very slightly biased towards bending into the stock it will, & it will also do this every time instead of trying to bend randomly left ,right ,up or down. By tunning all your guns like this it also lets you change from gun to gun without fear of them shooting to different points. IMO this is overlooked by most gun manufacturers except a few custom builders who understand the principle of "the archers paradox". If you can build a 6 kg gun that you are comfortable with, then that is going to be great to shoot. ATM I am using a 3.5 kg stock to shoot a 1.8m 11/32 spear with four 16mm rubbers. It groups better than a grapefruit at about 8m from the muzzle if I have a good grip & use my spare hand to brace the back of the gun, if I shoot it one handed it shoots over 100mm left & high (I am right handed). Its good to know these things about the gun you use, I think if you do go with a six kg gun you should expect better accuracy than this if it is well tuned.
 
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