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pull measurements
- Thread starterportinfer
- Start date
Thread Status: Hello
, There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.
It can take a long time to get an up-to-date response or contact with relevant users.
It depends on the band, but 16mm bands are normally about 40-50kg, 20mm about 60kg
cheers
dave
www.spearo.co.uk
cheers
dave
www.spearo.co.uk
Last edited:
pair of bands will give you that pull 
imagine 120kg pull, who can load it? rofl
http://www.omersub.com/data/slings/slings.htm
(check the bottom of the page)
imagine 120kg pull, who can load it? rofl
http://www.omersub.com/data/slings/slings.htm
(check the bottom of the page)
Last edited:
Well what I really mean is at what force will a spear leave the gun ?
My mate is saying that the guns are really inefficient compared to a modern bow.
I don't disagree but I also thin that the thick rubber is just a different way of moving an arrow/shaft in a medium (air/water).
Different strokes...
My mate is saying that the guns are really inefficient compared to a modern bow.
I don't disagree but I also thin that the thick rubber is just a different way of moving an arrow/shaft in a medium (air/water).
Different strokes...
Yes, compared to modern bow gun is inefficient, but its very different to shoot underwater than above water.
As much as the pull, you can compare, but thats about it.
The arrow for instance is very different. Modern bows shoot carbonfiber arrows, we instead use steel arrows. Steel arrows weight many times more than carbonfibre ones. As the water resists movement very well, the heavy arrow is the only way to go. Also the heavy arrow is by far more 'powerfull' or you could say that is has more punch.
Also, modern bows use small reels ( dont know they are called in english ) to make it easier to load. This however is not possible with our guns, since we need power that has very strong and fast with very little movement.
I'm sure some physics expert can tell more about that, but its anyhow very different to shoot an arrow underwater than above.
Tuomo
As much as the pull, you can compare, but thats about it.
The arrow for instance is very different. Modern bows shoot carbonfiber arrows, we instead use steel arrows. Steel arrows weight many times more than carbonfibre ones. As the water resists movement very well, the heavy arrow is the only way to go. Also the heavy arrow is by far more 'powerfull' or you could say that is has more punch.
Also, modern bows use small reels ( dont know they are called in english ) to make it easier to load. This however is not possible with our guns, since we need power that has very strong and fast with very little movement.
I'm sure some physics expert can tell more about that, but its anyhow very different to shoot an arrow underwater than above.
Tuomo
He is probably talking about a Compound bow a totally different story when used underwater. The resistance of the carbon/fibreglass blades moving through the water would severely reduce the power of the bow in water. besides the little cams would also not work as efficiently underwater, I believe that the only reaseon the cams are there to make the bow compound is to ease loading beyond a certain point. ie the effort of loading is not linear it gets easier once the bow is pulled beyond a certain point.portinfer said:
remember that water is 800 times denser than air and you see the need for linear pull in the same direction as the shaft.
The little cams on modern compound bows are really clever. There purpose is to reduce the load that it takes to hold the bow in its compressed state. For example , it takes say 100lbs draw weight to compress the bow but only 50 lbs to hold it compressed. Without cams a 100lb draw weight bow would take 100lbs to hold compressed. Therefore with cams you can hold and so aim a powerfull bow more easily. Seems to defy scientific logic but it works.
As there is a mechanical trigger on a speargun and you are not holding the rubber stretched by arm power cams are irrelevant. Any way they wouldn't work on speargun geometry, with the straight rubber pull.
The real point it seems is the "efficiency" of a speargun compared to a bow. I would think that bearing in mind the differences in the media they work in there would be little difference. A bow would be crap underwater and a speargun totally outclassed by a bow on land.
The performance of each weapon loaded with 100lb of force would probable translate into about the same efficiency.
Personally I think that the longest single rubber that you can physically load makes for the "best" most efficient performance. This means a limit of about 80cm strech and 120lbs pull. Beyond that you need multiple rubbers which increase force but decrease efficiency.
The ultimate would be a gun with one massive rubber needing 150cm stretch and 400lb pull. Trouble is only an orang u tang could load it! Clyde. Where are you Clyde? Left turn Clyde.
Actually this is where the crossbow developed from the long bow. The gun mentioned above could be loaded by a crossbow loading mechanism. Should be highly efficient and sweet to shoot. Has anyone ever built such a gun?
Maybe this thread should be looking at crossbows.
Dave
As there is a mechanical trigger on a speargun and you are not holding the rubber stretched by arm power cams are irrelevant. Any way they wouldn't work on speargun geometry, with the straight rubber pull.
The real point it seems is the "efficiency" of a speargun compared to a bow. I would think that bearing in mind the differences in the media they work in there would be little difference. A bow would be crap underwater and a speargun totally outclassed by a bow on land.
The performance of each weapon loaded with 100lb of force would probable translate into about the same efficiency.
Personally I think that the longest single rubber that you can physically load makes for the "best" most efficient performance. This means a limit of about 80cm strech and 120lbs pull. Beyond that you need multiple rubbers which increase force but decrease efficiency.
The ultimate would be a gun with one massive rubber needing 150cm stretch and 400lb pull. Trouble is only an orang u tang could load it! Clyde. Where are you Clyde? Left turn Clyde.
Actually this is where the crossbow developed from the long bow. The gun mentioned above could be loaded by a crossbow loading mechanism. Should be highly efficient and sweet to shoot. Has anyone ever built such a gun?
Maybe this thread should be looking at crossbows.
Dave
Hi Eric,
Carbon fiber spears have always been an idea that interested me. Picasso came out with one years ago with limited success I think. The cost was also prohibitive for most divers since loosing $100 shafts isn't an option. The shafts were a preset thickness of 6.5mm with a carbon fiber sleeve bringing them to 7mm.
advantages as I could see it were:
downsides:
Carbon fiber spears have always been an idea that interested me. Picasso came out with one years ago with limited success I think. The cost was also prohibitive for most divers since loosing $100 shafts isn't an option. The shafts were a preset thickness of 6.5mm with a carbon fiber sleeve bringing them to 7mm.
advantages as I could see it were:
- stiffness- prevent a shaft from flexing during flight that could only be achieved using a thicker shaft or by applying less power
- weight - light weight so the initial velocity would be very high I think
downsides:
- light weight- the initial high velocity of the lighter shaft (I think) would be lost quickly for long range shots where the punch of the heavier shafts still delivers
- wear and tear of carbon fiber - I'd hate to be eating my fish worrying about picking out carbon fiber shards from the meat!