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Why a long shaft?

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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donmoore

New Member
Aug 19, 2002
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In a scuba store I was talking to a sales rep about a man who had extensively modified his JBL. Everything he did made since to me, like shorter thicker bands, ect., except a longer shaft. My Riffe MT-5 comes with a 65” shaft, which stick out past the muzzle 10”. I don’t get it. Can anyone enlighten me as to why a long shaft would be better than a shorter one? Seems like the weight from excess length beyond the muzzle would weigh down the front of the spear causing it to shoot low.
Thanks,
Don
 

Dogmatrix

Deeper Blues pet
Jun 4, 2002
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I believe the theory is that a longer shaft helps you get closer to the prey... hence is more accurate, however yes if you go overboard or really powerup the shaft then it is going to be more prone to bending due to the unsupported weight leading to a loss of accuracy... Guess you just find whats comfortable for you and go from there.
 

andrsn

Just visiting...
Aug 26, 2001
1,213
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good and bad

if the shaft hangs off the end of the gun too far, it'll sag. if the shaft is bending just slightly as it's fired it will oscillate through the water. just as accurate as a knuckle ball. not good. you need a longer gun to support a longer shaft, especially if you're loading it up w/ rubbers.

the longer shaft actually has more momentum which equals mass times velocity. if your hydrodynamics are pretty equal between two different length shafts(same dia.), the longer one should always have more punch. there are always performance curves with each gun. each curve involves the use of a certain number of rubbers and a certain size shaft. IYA has been doing a good job at giving us some of this info. kudos, IYA! :friday what he's saying is that there's a maximum efficiency for every setup. underpowering may give you better accuracy, but w/ less punch and at only close range(i won last keys kraze w/ a single 16mm band on my 116 omer master which is considered way underpowered!). if you overpower the gun, you get more range and punch at range but w/ xtremely poor accuracy. what this means is that there's a good compromise b/w the right shaft/band power and resulting accuracy and punch at range.

maybe db should start sending IYA some more tools to finish this research. :D

happy shafting ;)

anderson
 

fuzz

Hawaiian transplant...
Sep 9, 2002
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For closed muzzles, I like the sighting advantage a longer shaft gives me.

For open muzzles, I prefer a smaller shaft for the reasons andrsn outlined.

Typically the closed muzzles are european guns and I'm too cheap to upgrade them, so the "new" shafts are are just longer stock shafts which are light and don't really flex. Just up 10cm or so to extend the range of visible point past the muzzle.

:D
 

Bill

Baron of Breathold
Oct 17, 2001
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"the longer shaft actually has more momentum which equals mass times velocity. "

I think I'll challenge that one. Better to say that the longer shaft loses momentum slower. Same rubber, same gun and the shorter (lighter) shaft will start off faster. Since the shorter shaft is stiffer, you could also reduce the diameter for the same 'whippiness' and get even more momentum.
I know, picky picky, I hate it when the doctor orders me to stay out of the water. Balance is what counts and tuning works best for that. Accuracy is the main reason for the muzzle overhang, MHO.
Aloha
Bill
 

Murat

Promethian
Jun 21, 2002
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Andrsn is right. momentum is mass time velocity. p=mv.
From the conservation of the energy;
Kinetic Energy=Potential Energy.

In that situation we have max potential energy at the begining that also depends on mass.When we launch the shaft it start to loose its potential energy and convert it into the kinetic and heat energy(Coming from friction).At the end of the trajectory of the shaft (just before the impact) KE is max and Potential is zero.At the impact time all the KE convert to the Potential energy.This is what we call impact power.Because of these heavier shaft has longer range and more impact power. With the right power, heavier shaft will have more flat trajectory.

KE (kinetic energy)+Heat (friction)=Max Potential energy (at the begining)

Friction in the water is very high so you can not convert great amount of your Potential energy to the KE.So more band power and heavier shaft will have better results

If you use max long shaft that your gun can support you get the best results.Ther will be no lower shoot if powered it up right.
 

frogman

New Member
Sep 10, 2002
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Euroguns typically put an extra 40-50 cm for the shaft compared to the length of the gun (130 cm for 90 cm gun, 140 for 100, etc). I assume that all these companies (OMER, Beuchat, Spora, etc) have figured out the physics and hydrodynamics to optimize their product (or I guess, it could be an example of the blind leading the blind). For pneumatics, the shaft protrudes only about 10-20 cm, the reason being the thicker shaft (8 vs 6.5 mm) needs to be lighter to accomplish adequate propulsion.
 

Iyadiver

Mr. Long Post
Apr 22, 2002
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DB want to give me tools for research...WOW...Thanks:D :D

One of the reason ( I think ) Riffe made the overhang of the shaft that long is for aiming. In the high power Riffe-s, you can't aim zero degrees flat on the shaft cause of some muzzle kick. I aim my JBL straight down the front muzzle. Since the muzzle of the JBL is quite high above the gun barrel, don't you think this is also indirectly a modified aiming ?? People may say that they aim just straight on JBL, they do but the use the enclosed muzzle as a reference. This is not straight aiming, this is elevated aiming. A Riffe, a Wong or an ALexander has nothing above its shaft to use as a reference aiming, so we elevate our aim by trying to see more of the spearhead, which mean muzzle up-butt down. This is more so on the high power models.

I shoot target board often so, I see the difference clearly. When you spend all ur shots shooting fish...especially big ones..it will be hard to tell. I am a land based hunter before I shoot fish, so I carry over the discipline of "zeroing" a gun before hunting with them. However speargun is more complex in its own way but being a close range gun ( say max at 7 meter s/23 feet effective ) many inaccuracy are not obvious cause you need range to open up the "grouping" circle.

The definite reason why Riffe has the same overhang for its threaded shaft on its entire range is that it is designed to ACCOMODATE the Riffe Ice Pick, that uses a slide ring to attach its cable. That overhang equals to the length of the Ice Pick cable.
Some people have shorten the overhang and get better result. Until I shoot target board with modified settings, I personaly can not claim anything I do results in better accuracy. How to define increased accuracy if there is no reference or measurement to use ?

I think longer overhang being better or not, depends on how each gun is suited to that overhang. If you can keep away shaft whip/oscillating, I suppose u can have the longest overhang possible if that benefits you. Don't think that overhang is a useless design. As long as you gun shoot well, it works.

An open muzzle like Riffe, has the simplicity of being able to use all kind of shaft diameter without much hassle of different slide ring/s size. At higher power Riffe, hitting a slide ring like a JBL set-up will be a disaster, this is why all high power guns will not use slide ring to attach a shooting line.

One thing we must understand on all projectile being fired out of a gun is that it will have a parabolic trajectory......some is more some is less. Depending on shaft weight and powerband used. I am not talking of muzzle kick induced low shots, strictly gravity related trajectory. The moment the shaft exit the gun, gravity acts upon it and the longer the shaft's flight time, the more it will head down. Let's not calculate the extra drag caused by various spearhead or thick shooting line and so on, just gravity. If a gun can shoot effective 7 meters /23 feet ( meaning it will be quite useless at 9 meters ) and the owner tell you that it is flat shooting, that is a ton of bull shit. There must be some few inches trajectory involved.

As far as trajectory is concerned, it is difficult to accurately measure on high power guns like 3 x 5/8 rubber ( or more ) Riffe or any other brands. I mean if you ask me to measure trajectory by 0.5 inch increment or by shooting a target board per 1 foot increment, I might have problem cause there is no fix or accurate sighting system to use. Practice is the key cause shooting a speargun is more by feel eventualy. The only kind of grouping you want to avoid on any guns is the erratic shots going left and right, this is inaccuracy. Consistent low on a fix distance is trajectory. Untill someone come up with a "smart shaft" that has some kind of steering control, trajectory is something we must live with.

What I foud out is that high power guns ( as long as recoil can be managed ) using thin shaft has better/flatter overall trajectory. It is not to say thin shaft is better, it juts move faster in water and means less time in flight, thus less gravity effect. I am still trying to find out the best shaft set up for each of my guns. The problem with fast shaft is that water drag increase (can't remember the exact formula ) tremendously for speed increase , so much so it become inefficient. I mean energy required versus shaft speed produced.

I recall the rule of thumb to double speed on boats require quadraple horsepower and that is applicable for up to certain speed, later the underwater gear ( propellers ad brackets ) will produce cavitation and can not push the vessel much faster efficiently in terms of power applied. I just surf around some NAVY submarine info and it seems 80 knots/ 92 MPH is about the critical speed any underwater object/projectile can do most with efficiency. The next step is to produce super cavitating torpedos where they introduce an air bubble to envelope the torperdo and eliminate water drag......some fancy physics. If anyone has a boat with step hull, this is similiar in concept but probably 100 times more advance.

Don't we wish one of us spearo works in a naval research facility and can "steal" some simulator time...Wha ha ha ha.
 

donmoore

New Member
Aug 19, 2002
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reply

Thanks guys for all your insight. Because my gun is already long, a MT-5, I don’t think I’m going to lose a significant amount of momentum if I shorted the shaft. I also won’t lose much in “how close I can get to the prey”. Seems like the most important factor effecting accuracy is the length of the barrel and track on it, which I already have. I think Iyadiver is correct that one of the reasons the standard Riffe shaft has a long overhang is to accommodate their ice pick, rather than for optimal performance.

Cutting 9” of the shaft will only decrease mass by 14% and still leave a 56” spear which is more than a lot of folks are using. It should also help in decrease bending and oscillating as Anderson mention. I shook my shaft, and at 65” it bends pretty easy.
Don
 

Shadowkiller

Digital Hunter
Jul 30, 2002
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The original reason for having an overhanging shaft was to balance out the sag in the middle of the shaft.

A lot of guns have a muzzle support that is raised from the barrel and of course a trigger housing that is slightly raised. To avoid the shaft sagging downwards they extended the protruding length to counteract the sag. That way, when you fire it, there will not be a pre-existing sag to screw up your trajectory.

Riffe was one of the first to use a full length support for the shaft. Now most companies try to use a rail or enclosed track, except for cheapos.. *cough* SeaHornet *cough*.

An overhanging shaft on more modern guns is either to allow for wear of the tip (tahitian) or as Iya said to allow for Slip tips. Or the designers do it because its "standard"... :hmm

If the speargun companies have done a lot of research then they sure havent published it for the customers to peruse. The best stuff I've seen has come from Steve Alexander and Terry Maas.

If you look at the Mundial Elite from Beuchat you will see that is it unsupported in the middle. I guess thats why most euro guns have so much overhang... poor use of new innovations.
 
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Iyadiver

Mr. Long Post
Apr 22, 2002
998
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I have good news on shaft overhang. If situation permit I will do some testing this weekend. I have just received yesterday my Riffe MT#0, I been waiting for almost three months for this unit. There is so much hassle in the importation, permit & tax, this gun cost me fortune. I could have got a Riffe Blue Water with a wing kit for all the expenses I cough out, let alone the trouble and misery of waiting that long.

Anyway a spearo's gun is a spearo' wife, that's my motto and no one....no one...will take my wife away. ( I'll swap for Britney , he he he )

Somehow the shipment came in with a wrong 3/8" shaft. It is supposed to be 32" but it came as a 36". Then it got me thinking, why not experiment with this extreme over hang. I mean extreme in contrast to the total length of this short shaft. The total overhang is actualy almost as long as any 40" up Riffe. I just realized today that the smallest of Riffe ( all with #0 ) has short overhang. At 32" shaft length a typical 8-10" overhang sure look funny.

Anyway I got this MT#0 to learn the followings :

01. To test if its is feasible to have a shortest posible gun at 81cm/32" to be as powerful as my Standard#2 at 49"/124cm at 3 bands. I'm trying to compare if length versus rubber quantity make sense.

02. Metal Tech butt being 3" further than teak mid-handle is about the kind of mid-handle dimension I am comfortable with. I been avoiding teak mid-handle cause I fear my mouth get ripped off by the butt kick. I like shooting single hand so much, I have always feared mid-handle.

03. To test what happen it I power up short 34" by 9/32" Hawaiian shaft with 6 x 9/16 bands. I believe there is a maximum speed that can be achieved by thin shaft and above that rubber power will be wasted. The speed of the shaft will never exceed the speed of the rubber "rebound" anyway. How much can I push ?

04. To test what kind of recoil 5 or 6 x 9/16 rubber at this short length will be like in this kind of short gun with 3 different shafts.
I know my limit of single hand shot being comfortable is 3 x 5/8 shooting 3/8" shaft with Ice Pick on a 61" Riffe Standard #4. Since heavier shaft produce more recoil...techicaly MT#0 with even 5 or 6 rubbers should not be very offensive.

05. Shorter shaft even thin ones are less prone to shaft whip...yes we know that.....how many rubbers/poundage can it take at this shaft length ?


The MT#0 is set up as such : ( next week I'll do full photo and review )

aa. Alumimum muzzle. Can take 5 x 9/16 rubbers and in fact 6 rubbers if for physco like me.

bb. Floater Wing Kit.

cc. 34" x 9/32" Hawaiian - Original Size. With 270 lbs coated stainless steel cable at 3 wraps or about 3.7 meters.

dd. 32" x 5/16" Threaded - Original Size. With same SS cable. Plan to use large spearhead.

ee. 36" x 3/8 Threaded. With same SS cable. Large spearhead.

I have extra 36" x 3/8" shaft which I will shorten by two inch per testing till it become 32". See which one will be best suited.

Why the Metal Tech series ? I just realized that Metal Tech is the only Riffe that can take the same amount of rubbers for its entire models, from shortest to longest. The strength lies with the aluminum barrel. The teak Riffes has stock size jumping up when the length start to be in the 60" length and above. I shop with catalogs, so I can't see products till I paid for them and wait like shit for it to arrive.

Next to test will be the enclosed track for 9/32 and 5/16" shafts. Will it do wonders on this shortest gun ? Riffe mentioned that it benefit most the long guns like MT3 upwards, naturaly. Since experimenting is fun, me must test enclosed track.

Best of all, where can you get this kind of crazy review unless at DB from Iya ? Wha ha ha ha ha :D :D.


IYA
 

donmoore

New Member
Aug 19, 2002
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IYA,
Great research IYA. I sure wish I had access, like you do, to a testing place. I have been looking to make friends with someone who has a long swimming pool, but haven’t had any success yet. I have to do my experiments in the real world, which for me is a long, time consuming, expensive, boat trip. There is no decent diving from shore. You have to get out at least 18 miles before the visibility is good. But its not all bad because during he summer the visibility can be over 100 feet and we have large fish, compared to some of the Europeans on the group.

I would have a few reservations about your short gun, even if you could get it accurate and with power. Seems like the fish want to stay away from my body and they are less concerned, sometimes even curious, about the spear tip. I would think with a shorter gun your shots are going to have to be longer. Plus so far of never heard of anyone being able to get a short gun as accurate as a long one at distance. The effects of being further from the fish and losing distance accuracy could combine.

As you said, the only difference in the metal tech series seems to be the length of the aluminum barrel. You know the price difference Riffe charges between the small MT and the large ones is more than their cost increase of a longer aluminum barrel, plastic track, and shaft. Just thought I would throw that in!

Keep us informed of the experiments. Looks like I may get a chance to go Thursday. My machinist friend was slow at work so he already shorted my shaft by 9”.

Shadowkiller,
What you said about shaft overhang makes sense. Seems like both the manufactures and the users try to use shaft length as an inexpensive and easy fix for problems that are caused by other design factors.

Rigdvr,
If you’re out there. I love the GPS Waypoint Search map on your http://www.rodnreel.com/ link. I found a platform that is on none of my 3 maps. Only problem was, when I got there it had a sign that said no tying off to it and no diving. But that’s another subjection.
Don
 

Iyadiver

Mr. Long Post
Apr 22, 2002
998
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Hi Don,

Getting viz of 30 feet is a problem with me. I always do my testing at sea. There is an Olympic size pool in one of my client's house but I dare not borrow it, I am afraid I owe him favor and he ask for discount on my services:D :D . Anyway I have a nice #2 fully rigged Riffe to give him as a present. He doesn't dive but he loves fire arm. I suppose the teak Riffe should please him as a weapon collection and pool here I come.....................:eek: :eek:

I tried public pools and they won't allow me. My friend has a pool but only 5 meters long, too short.

My closest testing ground is 40 miles out to sea on a private island, the island belong to my boss and it is being leased out to one of my friend. The lease will expire soon.....I'm in trouble. I can be at the island any day, any time but getting there is the expensive part, u own a boat u know how it is. So the routine is that I tag along my friend who is also a spearo ( naturaly a Riffe owner too ;) ) who goes there almost every week cause he is the one who rent the island. I may be poor but I live a very WET life on weekends:D :D. It is just sad that this island is located in Indonesia worts sea, the Java sea. Shallow at 140 feet average and barren. You can see reef fishes but Jacks, Spanish Mackerel and all the godly fishes are hard to come by. Those oil rigs only 20 miles further north of this island WERE my heaven :waterwork :waterwork . This year I seen super bad viz hanging around so long, I am very sad.

I think you are probably right about short gun has more difficulty to achieve good accuracy at long range but what I observed of my fishes here in my usual hunting ground is that they fear my gun more than my body. They fear most my sudden swinging of the gun. I probably lacked the stealth stalking skill.

I am hoping this 81 cm MT#0 as a 4 meter effective gun, that is all. My #2 , I consider a 4 meter effective gun. I have one wreck where the current is so strong, aiming a #2 is impossible at times. If I am 12 o'clock dead into the current it is OK but once my aim start to be at 1 o'clock to track the fish, the current will swipe away my aim. I lost many fishes this way, I can not track them. Being a scuba diver, I use the other hand to hold on the wreck while kicking to maintain position. The right hand does all the aiming and tracking. This is why teak mid-handle Riffe is a no-no at this location in strong current. The butt will kill me. MT butt position is still acceptable. The fishes hang around torpedo damage holes at the hull which get current directly from either port or starboard side while the wreck sank/sat flat on its port side hull. Either way I can not avoid being positioned on the smooth-nothing-to-hide-at hull side if I want to shoot them. This is a 565 foot long wreck. This is when a short gun idea came to my mind...........to be able to aim and track in strong current.

The other big fish possible place is a FAD made out of 4 buses stacked 2 up , 2 up, side by side. At 120 feet this FAD is all dark, in terms of water viz and interior lighting and this is where the giant trevaly loves to hang around.... INSIDE the bus. Everytime I need to be able to see the bus interior, I must get very close to the window frames ( no more glass ), to see in that shitty dark. When my face is so close to the window, my #2 will have protrude at least 90 cm into the bus. Either the GT get scared by the gun or I aim/track too late. I am hoping the MT#0 being so short can remedy the situation. Less protrusion into the bus and naturaly faster tracking.

Even on the abandoned rig I frequent, the snappers and the red groupers do not hang in the open. They love to hide under the rig legs cause at each corner of these 4 sided rig, there is a steel plate welded. More or less parralel to the sand, thus it create a table like shelter to hide under. This shelter is only 30 cm high, some less depending on sand being washed under this plate. Everytime I use #2, since it is long, I need to position my body further away from the shelter and I lost sight of the fish cause of the angle not to my favor and sand surface not being flat at all location around the rig. If the fish is big enough I sometime I can olny shoot them by placing the pistol grip next to my RIGHT EAR ( ha ha ha ) and aim by estimation. The other method is by being inverted, fins up head down, this give me an overall low profile to see better at this small opening cause my body need not add extra height as it rest on the sand. By all means a shorter gun will benefit me under this hunting situation.

I shot many fishes by being in inverted position because there are times when it is the only way possible. The short pneumatic was my favourite for this kind of position. I hope the MT#0 can do as well.

Let us know how ur shorten MT5 shaft perform. I suppose ur shaft is 5/16". The 3/8" is stiff enough even at 65". U can always shorten ur Ice Pick cable.
 

donmoore

New Member
Aug 19, 2002
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IYA,
You love spearfishing so much, you have develop ways to do it in almost any condition! Sounds like the short gun may have its place for you. What time is there? You should be about 10 – 14 hrs different than here. Its 8:48AM Wednesday morning here. Do you have a night job you post from?
Don
 

Iyadiver

Mr. Long Post
Apr 22, 2002
998
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I post from home. I don't go to my office cause I am a field person always out station. I think we are somewhere between 12 hours diff. My little brother is in Austin Texas, I don't know if that is close to you. He works in a chip design company.

Have Fun
IYA
 

donmoore

New Member
Aug 19, 2002
958
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IYA,
Does your little brother spearfish? Austin is 5 hours away from me. If you ever get a tourist visa and plan a trip to visit your brother, let me know. Well do some legal rig diving!
Don
 

Iyadiver

Mr. Long Post
Apr 22, 2002
998
72
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Thanks 4 the invitation. I swore I will never go to US again. I am one person who can not keep still on long flights and a will-die-soon smoker. U may call me an addic. My little brother is my exact opposite. If I am the crook, he is the Police:D :D :D. He is too busy being a good boy. He will be going to MIT soon for his business degree, will quit his job. I just don't figure him out. Out of Melon and on scholarship to Berkeley for his master in Elect Egn and he still wants to go to MIT. Best of all, he never like Electrical ?????

I used to recall my Mom told me along time ago :

"Iya, if u can ever get a Bachelor degree, let alone a Master degree, I will burn one truck load of candles for you as sign of happines ". :confused: :confused:

Ha ha ha, I hate any flights over 4 hours and I can not sleep on an airline seat. By the time I reached the US east coast, I look like a zoombie. I was supposed to be in Austin to accompany my Mom visiting my little brother earlier this year but those long flights is just too much. Get my elder sister to do this "impossible" mission.:D :D

Do I an Alien ( US goverment called non US citizen Alien..........but I don't live in Mars.......... Mr Bush.......ha ha ha ) need a fishing licence to shoot fish in the US ? I know Guam cater sportfishing to Japanese.


Have Fun
IYA
 

Aquiles

King of the Kup KK04'
Sep 19, 2001
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Too much talk about shaft sagging in this forum. I know nothing of this subject so I will sit back and read.:D
 
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