Posts by Linghunt

Hau,

Yep, yep. I will bang on the rocks on the bottom at times to attract Ling-cods in. Throwing the anchor off the boat and noise hitting the bottom works too. Usually something there when I follow the rope down to check placement. I always check the anchor with a gun loaded.

I brought this up, since there was limited chatter on it. The speed of sound in Water is so much faster than in Air, thought it would good for fellow spear-o's to think about it. 5000 ft/sec is smoking fast.

The sound can also be a positive as another thought. Any time I was hunting on Scuba, kind-a felt like I was hunting with a loud chainsaw on my back from the noise of the regulator.

The Speed variation based on Water Temperature was a something I forgot about from School days.

% wise, not really a factor, but interesting still.

Here is a reference with nice graphs.

Water - Speed of Sound

Got a young BSEE that I PICKED to have his first engineering job couple years ago. I was between two candidates. I picked him, Cody... He was hands on being a gearhead and was driving a city bus to work and pay bills. SOLID.

Cody buried me with so many ideas on this project. Need to dig thru them. Young generation of engineers.... They can't think of one or two ways to do it, have to think of 1/2 dozen. I'll get him to do the EE work on this one. A sensor Array is fun part of this one. assuming we go that way.

Project still on track, I'll keep the post updated.

Glad you made it here. The open dive forum to free speech... Welcome.

I posted this on HSD, and got JUST 1 reply... Anyway

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Hello all.

I've read lots of chatter on various forums about the spear gun shaft speeds and the such.

But I've seen very little dialog about the sound of the gun and it's impact on the target fish.

From what I've read a typical shaft goes from 25 - 29 m/sec ( ~ 60 mph) so it's humming along. But the speed of sound in water is much faster than in air. Typically 1,550 m/sec not accounting for water temp.

So anyway, Is a the noise of the gun a factor? Are some more noise dampened than others? Is this considered in the design phase?

I read about getting faster shafts and U-tube videos on fish dodging, Matrix effect, but seems to me the sound is the warning vs the other stuff.

Perhaps I'm all wet on the topic. Love to hear what you guys think.
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I know Pete will post on this one.

-John

Thanks for the Link. That diver is the guy I had looking for on a different video. Saw it a long time ago and lost the link

Deeper Perspectives Episode 16- Shaft Flex

Deeper Perspectives Episode 16- Shaft Flex - YouTube

From a technical perspective, he did a Good Job with his methods, calculations, and estimates. His numbers match up with a lot of others out there.

Shaft Flex is a whole different area of discussion. All of it is pretty interesting stuff.

I guessed wrong, figured the landlord was a Hells Angeles type with a chain belt, and he gave you a beating.

My guess is he doesn't rent to spearo-s anymore. Probably on his tenant application form now.

Quote from Don Paul

I never heard the landlords car door slam as he stopped by to inspect the recent pool work.

Cliff hanger, The Story is just starting to get interesting? How old were you then?

Here is Tromic's work in detail.

Measuring speed of the shaft | Page 6 | DeeperBlue.com Forums

He did a great job digging into this.

Don, My goal was not to evaluate spear gun shaft speeds and performance. I had seen various testing and web links on the topic. It only makes sense that this has been done.

I just want a Tool to measure more accurate changes for drag on various spear tip designs. Depending on which gun or Pole spear is shooting it was not the real goal, but relative numbers to evaluate drag reduction features. Quantifying the hydrodynamic effect was all I wanted to do.

Curious to some of the safety issues you had.

Tank looks great. The depth is good enough to account for gravity dropping the shaft. assume you are aiming to account for that.

What kind of cost did you have for your camera? What was the frames/sec specification? The Camera will give so much info on the harmonics of the spear as well as speeds. Getting into the dynamics of the flight is real interesting stuff.

Thanks for posting the link to the tank, I missed that one. Wonder what the cost of Lexan or Plexiglass would be to make say a 40 foot tank? Throw in some 2x4 ' s and some nails for the nail gun. Maybe ABS sheets? I do have a plastic welder that I don't use too often. Water tight welds might be another challenge for me.

If it's under $500 might be worth doing. All I need is another project thou. At least I got space in back yard to build it, the wife might not like it. but that is another issue.

Sure would be a nice controlled test bed. I could keep all of the electronics out of the water besides the sensor arrays. Could mount arrays every 5 feet to give a nice time profile.

Could also just buy a high speed data acquisition card for computer and do away with electronic design.

Attached is a titanic model my buddies made. It was remote control and was made for a local city here for a summer carnival. They had a smoke generator in there too. That's what you get when a couple Mech Engineers and a few fabricator have time on their hands. Wonder if I can talk them into making me a tank.

I'll have to run all of this by "Carnac the Magnificent"

Reference link on him on Anodizing.

http://spearfishing.world/spea…pears-need-anodizing.html

Dollar and donut says he will get into the aspects of the initial acceleration of the shaft before Maximum velocity is obtained. That is where the real fun stuff is happening.

Quote from hau

1." I continually read/hear terms like "shoots fast, slow, lots of penetration, accurate, shoots hard", etc. But I cannot ever remember seeing a true FPS written about a speargun shaft speed.

Yep, I read it all the time, kind a like little kids in the school yard saying my Dad is stronger than your Dad.

Do they really know how fast it is and consider it IP. (intellectual property) or do they fly by the seat of their pants?

Lots of claims out there that they make the fastest and best product on the market, and they back it up with added sales hype.

Knowing the actual speed profile over time along with the mass of the projectile ( Shaft, pole spear, etc. ) opens up lots of great information to maximize designs.

Lots of other factors as well, but a good start. High speed camera was one thought I had, but it looked on the spend-y side.

WOODGUY, how long is that tank you made? What did you make it out of? My tank is a deep long, slow moving pool in a local river. This tank is free is use, but weather, run off from rain makes it not practical year round. This worked great when I did an evaluation of my Koah gun I bought a year or two ago.

Momentum changes can be measured too, but that's a different setup. Not seen any chatter on that topic.

The use of sound recording by Tromic was a very clever method as well.

Quote from hau

1. The longest shot I could conceive taking would be 25-30feet, with most shots considerably shorter.
2. Initial and (IMO)"Final velocities" information would be a huge asset in building and designing spearguns and spears. Some spearos and spearing applications (Mediterranean) require faster/flatter shooting spears, while some spearos and spearing applications (pelagics) require heavier spears to ensure correct penetration in larger fish.
IMO,With accurate spear speed measurement:
1. A gun designer could test one manufacture of gun band against another,
2. A spearo could use spear speed to calculate spear trajectory.
3. Spear speed and weight could be used to calculate kinetic energy delivered at X distance.
4. Spear speed could be used in speargun design and efficiency.
There are many more.

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Agree 100%,

I see this item as a tool for evaluating my own designs mostly. I don't see a big market where diver would really want this.

As for the Big boys, making Guns and Pole spears, I'm sure they already have their designs completely tested for this kind of basic stuff. Couldn't give it away to them, vs. thinking of selling it.

Making one or a couple of these is about the same. Not sure If I want to make more than that and store in the basement.

Not sure I want to test gear for folks either and Play "Consumer Reports" , planning tests and other factors is important as having some data tools.

Sounds good, What is the longest shoot one would want to take?

Display would show Initial and Final velocities. I guess I could display the time to travel the distance, but operator would need to measure out the distances from sensor arrays.

I'm thinking 4 - 6 weeks based on current workload, assuming I don't have too many hurdles.

Quote from popgun pete

Maybe ask why the extension is needed, or is he asking for a longer shaft and just expressing it as needing an "extension". A length of 8 inches seems a lot given that the shaft must have some muzzle overhang as is.

Here is the reply I got this morning, after I asked the length of the spear gun shaft.

"It's 100cm. It's too short. I can't even aim to shot."

I followed up on where they bought the gun and possible manufacturer link. I'm curious now.

Just a little different with Water media vs Air.

Some of them use visible light other use IR for the detector stage. There's a couple ways to skin that cat from what I'm thinking, but going to have coffee with some techy buds next week to ring out easiest, cheapest way to go on this one along with some other projects.

Range would be slow, say ( 1/2 ft / sec to maybe 100 ft / sec ) that should cover everything we shoot in poles and guns...

Hau, in reference to the Archery Versions, do you like the bells and whistles of calculating averages and SD's etc. I was thinking of doing all that after download to PC. and only display last shot speed.

Maybe an on/off button, reset, and a display. Data storage could have raw data with time stamp.

Agree, and it's not a hard project with the technology of today. Pic chips are like dirt cheap, under $5 each and easy to program. Each Chip is like it's own computer. Low power draw, and could use rechargeable batteries, use inductive recharger.

Hermetically sealed parts for water is simple too.

Still don't know why there isn't a product.

If I had them, how many divers would want one?

Maybe I will make 2 of them. One for me and the Other for a one time auction on Ebay starting at $1. and see where it goes.

I'm a BSEE btw, but I also manufacture pole spears and spear tips along with lots of other parts.

I see the need to make an underwater chronograph for my own use in testing design features etc.

I think I can come up with something that could handle the water and measure muzzle velocity along with impact speed.

With the programmable PIC chips out there, the electronic aspects are not so hard. It's all about getting a good trig pulse for timers. I've worked with Optics for many years and have many resources, so I'm sure I can come up with a robust detector system.

With the PIC chips and associated products you can collect the data and also do downloads to computer with not much effort.

I did not want to re-invent the wheel if there is something already done. Anything on the Market?

Be a fun project, but got lots of other stuff to do.

-John

Agree, 100%. Just a messy customer service deal. I kind of thought it's a 9/32" shaft. Shaft started out as 3/8".

Second request I've had for a speargun shaft extension. The other one had a 3/8" shaft and wanted 5/16"-24 M to F threads. I recall he was in France. A longer one piece shaft is way to go.

It is interesting the requests I get at times. On the lighter side, I had a request in past for a 5/16"-24 M to F out of 5/16" stock. Took a bit to explain you can't drill and thread a 5/16" thread in 5/16" stock. "devil is in the details"....

I have a customer looking for an extension on a spear gun shaft. I think they just need to buy a longer shaft from manufacturer. Language barrier involved in dialog.

"My Speargun is a 75cm Top Gun (Brand) , shaft is 6.5MM so I need an 8 inches extension with male and female thread"

Any help would be appreciated. My search for the gun was fruitless. Thanks in advance. -John

Not really felt it, perhaps the same effect if you are in a boat all day as well out in Ocean.

I guess they can find a name for most things. Perhaps a "Saltwater Attention Deficit Diving Disorder Syndrome".

SADDS

Medication is 3 cold beers.