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Old 10-06-2018, 01:52 PM   #1
Hpwatson
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Mahogany 150 Tuna Gun

Just finishing up my first tuna gun build, I tried a lot of new things on this build (new to me) and everything ended up coming together really smoothly. The shaft hasn't come in yet so I mocked it up with one of my smaller shafts just because I couldn't resist taking some photos. Taking this thing on a tuna trip in less than 3 weeks!

Setup is:
  • Epoxy poured enclosed track
  • Mid handle with push rod
  • Neptonics Tuna mech
  • 4x 5/8" bands @ 315% stretch
  • 150cm band slot-->shaft notch
  • 100% Mahogany
  • 5/16" x 65" shaft with Neptonics slip tip (not here yet)
  • Teak Oil finish










Last edited by Hpwatson; 10-11-2018 at 04:09 PM.
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Old 10-06-2018, 09:47 PM   #2
hydroid
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Re: Mahogany 150 Tuna Gun

Nice work, reminds me of the older Ulusubs.
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Old 10-07-2018, 02:43 PM   #3
Hpwatson
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Re: Mahogany 150 Tuna Gun

Thanks man, that's funny I was looking around and taking little design ideas from some of the more popular tuna gun shapes out there and I'd never actually seen the ulusubs. It really does look similar.
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Old 10-08-2018, 03:19 PM   #4
deanmc
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Re: Mahogany 150 Tuna Gun

Nice job, looks like a solid build. One thing you might want to consider is removing a little material by the line release so there's a little more room to wrap your line on it.
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Old 10-08-2018, 03:31 PM   #5
Hpwatson
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Re: Mahogany 150 Tuna Gun

Yeah I was trying to keep things symmetrical but I may have to shave a bit more off on that side. Stilllllllll waiting on the shafts...
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Old 10-08-2018, 03:50 PM   #6
deanmc
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Re: Mahogany 150 Tuna Gun

The epoxy track looks cool, with the clear epoxy you used you can hardly tell it's there.
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Old 10-09-2018, 07:31 AM   #7
Hpwatson
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Re: Mahogany 150 Tuna Gun

Thanks man, I would have actually liked to do a colored track but I was in such a hurry to build this gun for a trip I have in 2 weeks that I didn't want to wait for the coloring to come in. It does look kinda cool though I guess.
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Old 10-09-2018, 04:41 PM   #8
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Re: Mahogany 150 Tuna Gun

Nice build. I noticed those Bands were not tied yet. What are those bands?

5/8" Small ID (16mm)
5/8" Regular ID

I'd be careful with your power settings. I know everyone is all about 380% right now, but that's a mid handle, that's a 5/16" shaft, and those look like 5/8" small ID Bands?

How much dos the gun weigh without the shaft?

with the above info I could help a little with your band settings which might make a difference when you jump in.
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Old 10-09-2018, 06:15 PM   #9
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Re: Mahogany 150 Tuna Gun

Sure, the bands are not tied yet because I still have to de-rig and ballast. Just got too excited about taking photos. The gun weighs 7.8lbs with no shaft unballasted, will weigh 10.55 without shaft after ballasted.

They are regular ID 16mm bands. The gun is 3" wide by 1.75" thick. Total length is 65"
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Old 10-11-2018, 04:09 PM   #10
Hpwatson
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Re: Mahogany 150 Tuna Gun

Quote:
Originally Posted by Behslayer View Post
I'd be careful with your power settings. I know everyone is all about 380% right now, but that's a mid handle, that's a 5/16" shaft, and those look like 5/8" small ID Bands?

I thought more about what you said and repowered it. I also got more accurate numbers after the shaft finally arrived.

Updated band info is: Regular ID 16mm rubber @ 315% stretch. I think this should be a much better setup.


A quick question about band length calculations - do you ever factor in the width of the gun? It seems to me that passing the rubber through a 3" wide gun and then down the sides should affect the calculation but the ones I've been seeing don't ever mention gun width, just wishbone length. The calculation I've been using is:

((Distance notch-band slot X 2) - wishbone length) / 3.15 = band length for 315% stretch

It seems like gun width should be factored in especially on a fat wood gun. What are your thoughts?
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Old 10-14-2018, 02:40 PM   #11
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Re: Mahogany 150 Tuna Gun

You can go to Spearitco.com and use their Band Length Calculator. 16mm Regular ID Bands, I'd go @ 320-330% from what I can remember. That being said, 16mm Regular ID bands are not the best batch for that gun. 14.5mm Small ID Bands you can increase the stretch % to @ 340% and the bands will be shorter and less mass. It's not such and exact science regarding muzzle width. Any way you do it you got Plenty of Rubber there for a 5/16" shaft. So you are not looking to Max out your power of the bands, rather you are looking for a little less power and a little smoother release. 3 Bands, you could tie them hot.
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Old 10-15-2018, 10:04 AM   #12
Hpwatson
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Re: Mahogany 150 Tuna Gun

Quote:
Originally Posted by Behslayer View Post
You can go to Spearitco.com and use their Band Length Calculator. 16mm Regular ID Bands, I'd go @ 320-330% from what I can remember. That being said, 16mm Regular ID bands are not the best batch for that gun. 14.5mm Small ID Bands you can increase the stretch % to @ 340% and the bands will be shorter and less mass. It's not such and exact science regarding muzzle width. Any way you do it you got Plenty of Rubber there for a 5/16" shaft. So you are not looking to Max out your power of the bands, rather you are looking for a little less power and a little smoother release. 3 Bands, you could tie them hot.

So you think 3x 14.5mm bands @ 340% will kill a big yellowfin? I'd be open to changing bands because this thing does have a good kick to it which makes accuracy difficult on long shots. If I switched bands I'd be tempted to keep it with 4
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Old 10-15-2018, 11:18 AM   #13
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Re: Mahogany 150 Tuna Gun

Here are what some practice shots look like:

https://www.youtube.com/watch?v=U9Nw3RCyjqQ


It kicks, but not as bad as some other big guns out there. After about 10 practice shots what I've found is that it's got a ton of power, you can see on my second shot the shaft goes through the high-density target and travels another 15ft and hits the wall with some force. Luckily it didn't damage the slip tip or the pool, but I like the power. I'm having accuracy problems at long range though (25-30ft). Short range and holding the gun with 2 hands I can get an accurate shot but I want to be lethal at 25ft. Could I keep the same power and increase accuracy by going to four 14.5mm small ID bands @ 340%? Or would I lose some power?
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Old 10-15-2018, 02:13 PM   #14
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Re: Mahogany 150 Tuna Gun

Nice job on the ballasting. I like the way you maximized the Band Stretch. Also like the Muzzle design which Functions to arrest the bands. It doesn't look like too much recoil in that shot.

What you are doing is riding the fine line between Recoil, Power, and what that Shaft can handle. It's 5/16" which is pretty thin and light compared to an 11/32". You can Max out a 5/16" Shaft with 3 Hot Bands or you can go with 4 bands at lower settings and try for a smooth release. Basically the thing holding you back from your goal of 25' kill range is not your bands, it's your shaft.

With 3 Small ID Bands 14.5mm you would want those bands hot at 380%. You would need to change them from time to time. With 4 Small ID Bands 14.5mm you can keep them looser @ 330%. They will last longer.. Either will have about the same range. Maybe the 3 bands will actually shoot further than the 4.. Less recoil from Band Materials.. about 40" Less Band materials on the gun with 3 hot bands.

If you up your Shaft diameter, then you will have more range. But, it might not fit in your track unless you open it up a bit. Also... it will transform the whole equation and inevitably you'll have a heck of a lot more kick. That gun with ideal band settings shooting a 5/16" can be smoothish. But with an 11/32" with ideal band settings it's still going to have some kick.

Different People have very different Recoil Tolerances. Pool Shooting, while very valuable, does not equate exactly to Shooting at a Yellowfin while you are diving mid Water. You are moving, your fins are engaged, you are in Kill mode, etc.. I have seen different people vary as much as 40% in Band Stretch on 4 band guns when I ask two different highly experienced divers to tell me what they think the ideal settings are for a gun in pool testing trying multiple shots.. I don't think people understand how personal Recoil Tolerance is.

25' kill range is nice for certain conditions, what it's best for is if you miscalculate the distance from a fish in clear water. You think it's 20' and it turns out to be 25' and your shaft still goes to the same place.. But, 25' is just on the verge of being an Irresponsible shot and certainly not a shot you Want to take. I see you are from GOM and from what I've seen in videos you will be shooting at closer targets than we might be in the NorthEast or guys in Ca, or in the Clear as glass waters of Hawaii. You'll be fine with that gun as it is right now. The Pool Test looked good as far as recoil and range.
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Old 10-15-2018, 02:16 PM   #15
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Re: Mahogany 150 Tuna Gun

ps. I do think as stated above that you could make your life easier by creating a little more space for your Line release. Rather than putting that finished gun back on a table and chancing getting everything right with the Router.. make up a sanding form and use some HEavy grit sand paper. You could take out a bit with a dremel to start, but that line release space kind of matches a thumb... and a strong thumb will get you a nice smooth arc there. Otherwise, all hell will be breaking loose and you'll be having your shooting line slip off your line release while you are trying to reload.. etc.
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