Master's Thesis on Speargun Design: Aalborg University

[popgun pete]

While conducting a google search for a parts diagram I stumbled on this pdf format document on speargun design considerations. There are 165 pages in all and its format is like a brochure with plenty of photos and diagrams. I have not read all of it, but to find it was a surprise to say the least!
https://projekter.aau.dk/projekter/f...n___Team_4.pdf

 

[popgun pete]

A bit more info. https://www.aau.dk/digitalAssets/362/362448_ardea.pdf

 

[popgun pete]

It looks like this ARDEA speargun is a leg loading, telescopic barrel band gun with foot pegs to push against with your fins when you cock the gun. A muzzle roller is used with an under barrel band anchor to run band length over top and bottom decks, the band staying the same with a greater stroke providing more power. The spear is assembled from various segments to change its length. Not sure how far the gun has got in terms of someone making it in any volume for sale to customers.

None of the ideas used are new, but the combination of them is a bit different. The hammerhead horns at the muzzle would not be suitable using such a gun in kelp, or poking it through small gaps in a reef. However they could be folded back to keep them out of the way, although there is always the prospect of a shooting line snag.

 

[Mr. X]

I saw a video yesterday on youtube by a guy who has developed and refined a repeating bow for archery. It has a magazine of 6 or 7 arrows. During development he realised he no longer needed full length arrows, so now shoots shorter than normal arrows. He has fitted it to different styles of bows, including, a long bow, a Mongolian recurve bow and a cheap Chinese compound hunting bow. The latter required him to modify his repeater mechanism but that lead to a significant improvement in the design. Perhaps we need to point him towards the above document, getting him working on spearguns instead of bows

 

[popgun pete]

Spearguns have much heavier projectiles than bows, hence require more energy to shoot them and that involves a long power stroke. One thing that is not apparent is how the ARDEA speargun locks its barrel during cocking and releases it for the next reload.

 

[Tatara]

@essayhave​

Hello guys, I study Marine Engineering at the College of the Florida Keys. And I need some help with my research project: Analysis of Speargun Performance, Design and Ergonomics. Any other useful resources / books / pdf's and/or projects?

 

[Mr. X]

Hi. Have a look round the forum, a forum member in the UK recently posted about his project on speargun performance. You could probably reference that.

 

[Jesse_Spiller]

Hi. Have a look round the forum, a forum member in the UK recently posted about his project on speargun performance. You could probably reference that.

That is me. Tatara, see my research outline below, I submit in 8 weeks. Would love to chat.

 

[foxfish]

I saw a video yesterday on youtube by a guy who has developed and refined a repeating bow for archery. It has a magazine of 6 or 7 arrows. During development he realised he no longer needed full length arrows, so now shoots shorter than normal arrows. He has fitted it to different styles of bows, including, a long bow, a Mongolian recurve bow and a cheap Chinese compound hunting bow. The latter required him to modify his repeater mechanism but that lead to a significant improvement in the design. Perhaps we need to point him towards the above document, getting him working on spearguns instead of bows

Ha Ha, i have featured this same man on the forum before, i can assure you he knows very little about spearguns!
He has several videos about testing spearguns !
I do like his videos though, find the one where he near kills himself with a steel ball fired from a catapult, it is very graphic!

 

[Mr. X]

Are we witnessing the sprouting, if not the actual birth, of academic speargun research? Perhaps a new UK/USA speargun maker/designer?

 

[popgun pete]

I doubt it, trial and error over 75 years has produced what we have now and virtually all speargun permutations have been tried. Often lessons learned have been forgotten and then had to be repeated, but each time ends up with the same result. Spearguns are very simple devices, but need to be suited to particular jobs while offering a measure of reliability.

 

[Jesse_Spiller]

During development he realised he no longer needed full length arrows, so now shoots shorter than normal arrows.

I'm looking into shorter spears (bolts?) with my speargun simulator.

They'd only work in enclosed tracks and the floopper design requires modification, but they shoot significantly faster with the same kinetic energy and are more recoil efficient. Since they are shorter, they can be thinner with less chance of buckling. Thinner shafts require less energy to penetrate a given depth in fish. Shorter shafts are less likely to bend when hauling a fish.

Unfortunately, the higher velocity has a downside. Drag is proportional to velocity^2 so they slow down and bleed energy faster than longer, heavier shafts.

We also cannot have an informed discussion about precision and accuracy differences without testing.

There is a crossover point at a certain range where the efficiency gains of the lighter, thinner shaft are outweighted by the enery conservation of the longer, heavier shaft. I won't be able to say exactly what this range is or whether 'ShortShafting' will be feasible until I've done the hydrodyamics work with a high speed camera (hopefuly later this year).

JS.

 

[Jesse_Spiller]

I doubt it, trial and error over 75 years has produced what we have now and virtually all speargun permutations have been tried. Often lessons learned have been forgotten and then had to be repeated, but each time ends up with the same result. Spearguns are very simple devices, but need to be suited to particular jobs while offering a measure of reliability.

Disagree. Firearms have been around over 500 years and we're still inventing new systems. Speargun are nascent by comparison.

Spearfishermen can be very simple. Spearguns are complex - especially rubber powered ones. These are the mathematical expressions that just manage to predict where their energy is even going. The very act of measuring a rubber in the system can permanently change it's behavoir. Rob Allen believes it's impossible to predict rubber behavoir with any accuracy. This makes repeatable data almost impossible - a complex problem.

Rollerguns are a new idea - they started emerging around 2006 and inverted guns are even newer. The hardware, even the best purpose designed stuff isn't yet of a great standard. Further, very few speaguns are designed as a system - most resemble a collection of components.

I contacted all major speargun manufacturers and many minor ones - very few were interested in research (Rob Allen and Picasso being notable exceptions). Very few conduct science based product development, and of those few, most have only started recently:

"I have been building guns for 35 years. For the majority of this time I was just working by trial and error and thumb sucking" - Rob Allen (10 Feb 2020)

There is also a huge trend towards marketing glamour in the industry. Manufacturers are capitalising on spearfishers lack of understanding to offer products that often don't make sense. Spearfishers are our own worst enemy - we don't hold manufacturers to account with our purchasing power.

We're seeing two big industry changes at the moment:

1. The dissemination of CNC and automated processes (Eg 4-axis routers) to large scale speargun manufacturers; think Riffe legacy vs Riffe Maurauder. The CNC machines required to make speargun components (steel) only leaked from large-scale machine shops around 2015 - although they are still mighty expensive. 3D printing also allows micro-makers to compete with injection moulding and large-scale operations to conduct rapid R+D without using unresponsive Chinese supply chains.

2. A burgeoning academic interest. The Ardea study was written in 2016. The first scientific study was conducted by Worthington in 2017. Duncan Henderson has been conducting research in New Zealand. My Thesis will drop this year. Tatara might carry the torch onwards?
Academic research is important; it supports the development of knowledge in the spearfishing community - not withhold knowledge as competitive advantage.

For example, I just launched a website that simulates any speargun using just 14 variables - and returns data like predicted spear velocity, energy, gun recoil , efficiency etc. Coronavirus has prevented pool testing so far, but I anticipate confirming the analysis later this year.
It can be used to compare spearguns and their characteristics - although I'm taking a few more days to work on the interface before sharing it.

The future is bright. I foresee a slow transformation and general improvement in the spearfishing community and our tools.

JS.

 

[popgun pete]

Short shafts lack stability, it has been tried as the shaft, which was much shorter than the gun, emerged from the surface of the test pool and flew out of the water when it was aimed horizontally in the pool. A hydropneumatic speargun can fire a short shaft if it is lever loaded via a hydropump and has no shooting line, but the impact energy at distance is low. A long heavy shaft can kill at long distances because of its momentum even though it may not be moving that fast. Spearguns use heavy projectiles to maintain penetration at distances such as 20 feet which is a long shot for a speargun underwater. Firearm projectiles and arrows are lighter because they don't traverse a dense fluid and they don’t have to tow a shooting line to attach to the fish.

 

[Kodama]

I love to see all this research being conducted and I am sure we will learn from it.

As a side note it is worth to mention the APS (Avtomat Podvodnyy Spetsialnyy). This is a Soviet underwater assault rifle developed in the early 1970s to give Soviet frog men a weapon that can be effectively used underwater, allowing them to take out enemy frog men without having to fight in close combat with only spear guns and melee weapons.

Note the 5.66 mm ammunition and the long bolt it fires. These very short ‘spears’ are being propelled quite accurately and pretty far. Off course they are being powered much harder.
Anyway I thought it might fuel the discussion.

 

[Mr. X]

The discussion of short spears has made me more appreciative of the possible benefits of longer, heavier spears. Perhaps this is partially why Rob Allen increases spear diameter across the product range with increasing power e.g. 6.6mm for 1x16mm band, 7mm for 1x20mm band, 7.5mm for 2x16mm. As far as i know, he doesn't increase the spear diameter for longer barrel lengths, which also have more power - but perhaps the increased mass of the longer spear takes care of that. I think the 16mm rubber version of the RA roller railgun has a thicker spear than the 14mm rubber model.

On another current thread a couple of forum members have been telling us about the range, accuracy and power of their Italian double roller spearguns, which use an 8mm spear.

 

[Mr. X]

I was delighted to read Jesse's enthusiastic, positive response to Pete's historical perspective. It is as it should be, with the "young Turks" taking up the torch and pushing things ahead.

I understand Pete's point. "Ain't nothin' new under the sun and the moon" as the saying goes. Also, I like to keep spearfishing simple, that's part of the joy. Otherwise the odds are too unfavorable for the fish, which are increasingly threatened. But I can see some opportunities for incremental improvements and perhaps some things completely new. Increased use of new materials (more carbon fibre, more ultra-high molecular weight polyethylene (UHMwPE) materials like Dyneema, metal foams and graphene perhaps, better rubbers perhaps) and techniques, as mentioned above, including hydroforming and 3D printing of plastics and metals. Perhaps more novel pulley systems? Perhaps Dyson style vortex applied to pneumatics

Perhaps better matching of spear length/mass to band/muzzle configuration and barrel length.

Perhaps warmer, less buoyant wetsuits, so we can carry less lead. Or inexpensive, auto-inflating safety vests, as pioneered by Terry Maas.

LED torches, smartphones, GPS, Google Maps, GoPro style cameras, YouTube, spearfishing discussion forums (DeeperBlue.com), etc. are all relatively new things that a spearo in the 1960s and earlier could barely dream of.

Or perhaps we'll just exhaust fish stocks and take up cycling instead. Or destroy the environment and make ourselves extinct?

 

[popgun pete]

If you read all the early patents, most of them are in French because spearfishing with spearguns basically started in France in the thirties, then you will see that in the thirties and forties many things were tried because no one knew anything about spearguns. The inventors soon found out what worked best and that resulted in the Arbalete type of gun which after WWII was exported from France all over the world. The spring gun had ruled the underwater world as band rubber was poor, usually because early band rubber was scrounged from other applications. The Italians and Spaniards copied the French spring spearguns and kept producing them for longer into the sixties until the pneumatic gun took over. In the formative period enclosed track band guns were tried with shafts fitted with empennages, a sort of horizontal winged tab, but wishbone notched shafts won out as the best ones to use. When enclosed track band guns started again in recent years people had forgotten those old guns back in the forties. On this board and elsewhere I showed the enclosed track Espadon which was decades before its time, an enclosed track band gun from the forties.

1943 enclosed track metal body band gun! - Spearboard.com - The World's Largest Spearfishing Diving Boating Social Media Forum

1943 enclosed track metal body band gun! All About Guns

www.spearboard.com

The Russian underwater assault rifle has limited range and would be useless for spearfishing as well as illegal these days as owners of SMG guns will know to their disappointment.

 

[popgun pete]

Here is the French patent from 1942 for a winged tail enclosed track gun shooting a short shaft compared with the length of the gun stock.

Those who forget their history are doomed to repeat it, which is why I spent several years reading all the old spearfishing patents. As could be expected the pioneers completely ransacked the cupboard of spearfishing ideas looking at every possible spear and gun propulsion combination. Only really novel idea today is the "Dreamair" which has spiral drum pulley tracks which would have been extremely difficult to fabricate in the distant past in any sort of quantity. For that you need computer controlled machines.