The Truth from Steve Alexander on enclosed track speargun

[Don Paul]

Speareasy, I was using full round shafts when I tested, a euro shaft will not drag as much water. You can weigh the gun with the bands in, I just lift them slightly while the gun is on the scale to get fairly close on the weight.

Slip tips and cordage never seem as accurate as a flopper, but Mori's are very close. I feel his tips are very good.
Cheers, Don Paul

 

[foxfish]

I really enjoy using enclosed track guns - there may well be some power loss but my guns still have plenty of power & shoot dead straight.

 

[Tin Man]

Phil said that people have no idea how much power they lose to enclosed tracks because water has to suck into the track behind the departing shaft, and a low pressure area is created that retards forward travel of the shaft.

This is one of those things that I have pondered, and always wished I could see some high speed camera footage of.

For example, I think Don Paul has mentioned boat-tailing the ends of the shaft to reduce drag. I wonder if there is cavitation behind the shaft? If there is cavitation, then how does the vapor space impact the significance of water having to fill the void throught the top of the track?

Someone who is more current in fluid dynamics will have to help me out on this, but the low pressure area behind the shaft couldn't possibly be stronger than a full vacuum (14.7 psi) right? So given that the area of a 5/16" shaft is 0.08 square inches, aren't we talking about a maximum of about 1.1 lbs of resistance?

None of which is to suggest that enclosed tracks don't sap energy, and probably in multiple ways (increased friction area, wedging of a momentarily distorted shaft, etc.). I'm just trying to work out the scenario that Bill mentioned.

Edit - I just realized that the low pressure theory would be pretty easy to test on a gun with a Neptonics enclosed plastic track. That would make it easy to change out the track, while keeping everything else about the gun the same. I can envision three tests - An open track, an enclosed track with the normal openning on top, and an enclosed track with the openning cut as large as it could possibly be and still retain the shaft.

 

[Don Paul]

The gun I tested was designed to use 3-5/8 bands and a 9/32 shaft or
one 3/4 band with the rollers and fairing plates. I only compared penetration
@ 20 feet, which was at was the limit in the 25 foot I was using.

My local gun lives in a environment of suspended sand in the surf entry's I
make. Tinman is right about the slight shaft friction under spline cycle when the shaft is oscillating.

One caution on the pool testing... unlike the sometimes mundane practice
of number crunching and physics contemplation, In pool testing is extremely
addictive, costly and dangerous. I have been able to stop for ten years until a slipped and acquired a Italian fart gun.:head

Cheers, Don Paul

 

[Bill McIntyre]

If Phil was correct about the suction effect of enclosed tracks, I'm thinking that I may be mitigating it by using a 9/32" shaft in my magnum hybrid with a track cut for a 5/8" shaft.

Does that make sense?

Also, does it make any difference that a hybrid only has an enclosed track on the rear wood portion? Or is any drag just occurring in the first portion of travel as the shaft is being accelerated?

 

[speareasy]

I checked the weight of the gun without shaft and it is about 2.85 Kg. I left the bands in as I would have to cut the wishbone to get them out. This gun was a little different from the back end and it was impossible to load (at least for me). I cut the back butt and added a piece of teak which I used two 2 cm SS threaded inserts on each end and used at 10mm threaded SS rod and epoxied the entire ensemble together. It changed the gun from the most difficult to load to one of the easier guns to load. That probably added some weight. I looked at the track today and it seems I could remove it. I might do that and retest for penetration without enclosed track.

I think Tinman has a point regarding cavitation. If you look at the video again you will notice at the moment the shaft comes out there is some water that has evaporated (bubbles). That could explain why there might be some suction with slower velocities which are negated at higher velocities since the gun is going through vapor. Whatever it is, I can assure you that loss of shaft velocity is NOT a factor in the gun I tested. The gun easily seemed like the most powerful 3 band gun I have ever shot ... and by that I don't mean recoil but rather at how much it penetrated the stiff styroboard at 7.2 meters.

 

[Don Paul]

If Phil was correct about the suction effect of enclosed tracks, I'm thinking that I may be mitigating it by using a 9/32" shaft in my magnum hybrid with a track cut for a 5/8" shaft.

Does that make sense?

Also, does it make any difference that a hybrid only has an enclosed track on the rear wood portion? Or is any drag just occurring in the first portion of travel as the shaft is being accelerated?

I know you meant to say 3/8'' or 5/16'' Bill, and yes having enclosed track starting midway back will have less power loss's even if the loss are small
indeed. Tell Phil good luck if you can. Thanks.
Cheers, Don

 

[Bill McIntyre]

I know you meant to say 3/8'' or 5/16'' Bill, and yes having enclosed track starting midway back will have less power loss's even if the loss are small
indeed. Tell Phil good luck if you can. Thanks.
Cheers, Don

Dammit, yes I meant a 5/16" track.

Phil and his buddies are on a charter to Catalina with Captain Leo today. I heard that they are were leaving at 3 AM and expecting to return about 9 PM. They were already pretty tired since they left Santa Cruz at 11:30 PM and drove all night to meet me at 8 AM. But then Leo's boat is slow enough and big enough so that they'll probably get to sleep on the way over and back.

 

[Don Paul]

I checked the weight of the gun without shaft and it is about 2.85 Kg
Quote: speareasy.

I think your mods to the butt end are a asset for you, and 6.28 lbs is very
close to the 6.5 lb wt of my Tiputa gun. A few ounces now in the wood in front of the bands may make it a very sweet shooter. A enclosed track can also be segmented along its span. I spend time on my bands, shafts and tips
to reduce hydrodynamic drag, which becomes more of a issue the faster the shaft travels.

Cheers, Don Paul

 

[speareasy]

I checked the weight of the gun without shaft and it is about 2.85 Kg
Quote: speareasy.

I think your mods to the butt end are a asset for you, and 6.28 lbs is very
close to the 6.5 lb wt of my Tiputa gun. A few ounces now in the wood in front of the bands may make it a very sweet shooter. A enclosed track can also be segmented along its span. I spend time on my bands, shafts and tips
to reduce hydrodynamic drag, which becomes more of a issue the faster the shaft travels.

Cheers, Don Paul

Yes, the gun could probably use some weight up front as it floats from that side. I can probably get away with adding quite a bit of weight since testing has been done in fresh water and salt water will give a little more flexibility in adding weight. I was thinking of putting a small wing up front to improve how the bands are lying, but then I would need more weight to factor that in as well.

With regards to the Mori slip tip, you are correct that they are the most accurate. I compared it to a Riffe Ice Pick and the results were almost the same for the Mori slip tip to a flopperless shaft. On the other hand one of my shots with the ice pick completely missed that huge square target at 6 meters. I think with the ice pick you have to very careful make sure the tip is in the correct place otherwise it will steer the shaft dramatically off target.

With regards to floppers, I find it incredible how people don't realize that the flopper can really pull shots of target. Before I go spearfishing I usually get in the pool early and "tune" any flopper I might use. If the flopper is underneath then the shaft tends to go up, if the flopper is on top the shaft goes down. Yesterday for my trip I had a Beuchat Carbon 95 that I wanted to take out. The night before I had quickly gotten in the pool to test it at 3 and 4 meters to see where the shaft was shooting. It was shooting uncomfortably low ... so before going to bed I put in probably the best shafts for Euro guns which are the One Spear shafts. Early in the morning I took a few shots just before we left, and it was spot on hitting about 1" low at max distance for the gun (4meters). At the same distance the Beuchat shaft with top flopper was about 10 to 12 inches low. Same gun but only the shaft changes and you have this tremendous change in shooting dynamics.

The One Speargun shaft has something that keeps the flopper tucked tight. It has no plastic cone (although I plan to buy and add them), but man it is tremendously accurate. Unfortunately the largest size it comes in locally is for 100cm euro guns. I have seen them online on european website in 7mm and 160cm length (perfect for Euro 120X). IMHO those would be the shafts to get. I just wish more shaft manufacturers would copy that design and make it easier to get a hold off. Until then, for long range shots in open water ... the super streamlined Mori slip tip is the best accuracy bet.

 

[Don Paul]

I have been using Ti cones I made for my game gun shafts a while back,
now I use the Omer cones for 6.50 on my Airbalete 7mm. I found I can split them and fill the gap with Gflex epoxy. You are spot on about the One shafts, I use one in my air gun and with the cone it fly's straight to the end of the mono with the cone.
Cheers, Don Paul

 

[speareasy]

I have been using Ti cones I made for my game gun shafts a while back,
now I use the Omer cones for 6.50 on my Airbalete 7mm. I found I can split them and fill the gap with Gflex epoxy. You are spot on about the One shafts, I use one in my air gun and with the cone it fly's straight to the end of the mono with the cone.
Cheers, Don Paul

I am interested which site you use to purchase the cones. I have also investigated the "O" rings, but they seem to only prevent the flopper from becoming annoying when swimming. The shaft will still deviate just as it did before the "O" ring.

 

[Don Paul]

I am interested which site you use to purchase the cones. I have also investigated the "O" rings, but they seem to only prevent the flopper from becoming annoying when swimming. The shaft will still deviate just as it did before the "O" ring.

I ordered mine from Omer in 6.50, then cut it and Gflex epoxied the void.The green at the tip is dynamat extreme acoustic suppression material covered by rescue tape.

Cheers, Don Paul

 

[speareasy]

Hey Don,

Thanks for the information, I will try to order some of the stuff. I guess it should be not too difficult to shape some of these cones from UV protected plastic. Not many people worry too much about these little things, but I am sure they would if they tested it in a pool. This would explain many of their missed shots. I really believe that there is a lot to improve in shaft design and hydrodynamics of shaft flight, and at the moment it seems to be the weakest link in speargun design.

 

[Don Paul]

Hey Don,

Thanks for the information, I will try to order some of the stuff. I guess it should be not too difficult to shape some of these cones from UV protected plastic. Not many people worry too much about these little things, but I am sure they would if they tested it in a pool. This would explain many of their missed shots. I really believe that there is a lot to improve in shaft design and hydrodynamics of shaft flight, and at the moment it seems to be the weakest link in speargun design.

I just enjoy the the development of gear and the satisfaction when I have a performance gain. This personal aspect of our sport is part of the draw for me. We all are at different places in our journey, some just want to walk into a shop and spend the money on what is said to be the best.
Others like myself like to design, fabricate, and tweak the gear.
Enjoy your journey mate.
All the best, Don Paul

 

[Mr__scott]

I am looking for a new gun to replace my older Omar 120 which shoots very low and slow. What enclosed gun would you recommend for hawaii reef fishing? I would like something with more range

 

[Ginger ninja]

Has anyone experimented with fluting or perforating the track like a muzzle break on a rifle? The other thing would be to create a spear with golf ball dimples on it. golf balls fly further because they create dead pockets of air in the dimples. When the air outside the dimples contacts these dead pockets the coefficient of frication is less than that of a golfball plastic thus a dimpled golf ball goes farther.

 

[Linghunt]

Has anyone experimented with fluting or perforating the track like a muzzle break on a rifle? The other thing would be to create a spear with golf ball dimples on it. golf balls fly further because they create dead pockets of air in the dimples. When the air outside the dimples contacts these dead pockets the coefficient of friction is less than that of a golf ball plastic thus a dimpled golf ball goes farther.

Dimpling does work, goes back to WWII on torpedoes, some fish/ sharks do something similar with their scales to reduce drag and the turbulent wake.

After this process is complete, how straight is the shaft. Doable to straighten but is the added cost of something like this practical? dimpling patterns can endless.

I drew up some tooling sketches to dimple Aluminum tubing for pole spears a few years ago, and was not too crazy, but l did not start making it. Part of my hang up was removing the temper from the AL for the process, then going back to a tempered state. that's not too hard, but how straight will it be? Still on the long " to do list ".

 

[seatrophy]

for sure enclosed track is a bad idea.
1 uncomfortable load, time waste
2 acceped new shaft only
3 energy loss on friction steel to plastic
4 energy loss with hydrodinamical water play in cleft between shaft and track
.. but i guess if use a special OPEN track profile and low friction material for track can safe some notable power ..