Home Tournaments Calendar Weather Merchandise Sponsors

Go Back   Spearboard.com - The World's Largest Spearfishing Diving Boating Social Media Forum > Spearfishing Gear > All About Guns

All About Guns What's your weapon of choice, and why? Discuss the beloved speargun here!

Reply
 
Thread Tools Rate Thread Display Modes
Old 09-13-2017, 09:51 PM   #1
fr0sty
Registered User
 
Join Date: Aug 2013
Location: Cambridge, MA
Posts: 150
Shaft for short roller

I have an 80cm mako that I'm converting into a roller. I already have a 90 roller so was thinking about cutting the mako down to 70cm. I'm planning on using 14mm small ID bands that would utilize the full barrel length to ultimately be stretched to 350%.

Question I have is whether I should use just use the old 6.5mm 120cm shaft or if I should get a 7mm 110cm shaft? Or even a 6.5mm 110cm shaft?

I was reading some stuff that for rollers, it'd be better to have a shaft with higher mass to counteract the shorter spear. Other things I read were it's better to have a thinner shaft. Any new ideas or experience from your guns?
fr0sty is offline   Reply With Quote
Old 09-14-2017, 03:21 AM   #2
TVA
Registered User
 
Join Date: Jul 2013
Location: Kailua, HI
Posts: 280
Re: Shaft for short roller

What has been generally noted on standard roller guns is that the rubber contraction speed is highest right when the shaft is released and that as the shaft accelerates and the rubber slows down as it gets to the muzzle, the wishbone is actually no longer in contact with the shaft even though the rubber is still contracting and the shaft hasn't fully left the gun yet. That's wasted energy. A way to somewhat counteract this is to use a heavier shaft that requires more energy to accelerate, meaning it will stay in contact with the wishbone longer and absorb more of the energy that the bands have to give. It's a balancing act as you want the shaft heavy enough to absorb what it can, but not so heavy that it's too slow. It your case I'd run the 7mil and up your stretch ratio to 380% - 400%. Also, make sure that shaft has a loading tab or dog house closer to the middle to attach the mono to. That makes a difference as well.
TVA is offline   Reply With Quote
Old 09-14-2017, 07:48 AM   #3
fr0sty
Registered User
 
Join Date: Aug 2013
Location: Cambridge, MA
Posts: 150
Re: Shaft for short roller

Interesting. Any reason as to why to 380-400%? Also, what kind of difference would attaching the mono to the middle versus the end have?
fr0sty is offline   Reply With Quote
Old 09-14-2017, 08:44 AM   #4
TVA
Registered User
 
Join Date: Jul 2013
Location: Kailua, HI
Posts: 280
Re: Shaft for short roller

Quote:
Originally Posted by fr0sty View Post
Interesting. Any reason as to why to 380-400%? Also, what kind of difference would attaching the mono to the middle versus the end have?
With these small ID 14mm rubbers the optimal performance seems to be around 380-400%. The mid point connection on the shaft will both help prevent the mono from getting pinched by the wishbone and affect the flight of the shaft less.
TVA is offline   Reply With Quote
Old 09-14-2017, 08:51 AM   #5
fr0sty
Registered User
 
Join Date: Aug 2013
Location: Cambridge, MA
Posts: 150
Re: Shaft for short roller

380-400%? really? I thought it was 350-360%, that's what I've been using/tying. I thought it was already more than the 300% for normal ID bands.
fr0sty is offline   Reply With Quote
Old 09-14-2017, 09:05 AM   #6
Xylophone
Registered User
 
Xylophone's Avatar
 
Join Date: Jun 2016
Location: Descanso, CA
Posts: 62
Re: Shaft for short roller

I tied my 16mm small id band on my roller at 350% and the 14mm small id bands on my other roller at 370% and I have noodle arms. It isn't as hard as you think.

I tried a 20mm on my hole gun at 350% once. That gun went back to the dual reg id 16mm's at 350% after that dive.
Xylophone is offline   Reply With Quote
Old 09-15-2017, 04:44 AM   #7
TVA
Registered User
 
Join Date: Jul 2013
Location: Kailua, HI
Posts: 280
Re: Shaft for short roller

Quote:
Originally Posted by fr0sty View Post
380-400%? really? I thought it was 350-360%, that's what I've been using/tying. I thought it was already more than the 300% for normal ID bands.
For the past couple years I've been using Primeline small ID exclusively. Batches have varied from 14mm to nearly 15mm, but I've always run it between 380 and 400%. Still easy to load and the smoothness with power can't be beat. On a small roller like you're describing even with the bands at 400% they'll be easy to reach/load so there's no reason not to get all the performance you can out of it. How are you going to be securing the bands on the bottom of the gun?
TVA is offline   Reply With Quote
Old 09-15-2017, 07:44 AM   #8
RBainer
Registered User
 
RBainer's Avatar
 
Join Date: Aug 2014
Location: lake worth
Posts: 256
Re: Shaft for short roller

Quote:
Originally Posted by fr0sty View Post
I have an 80cm mako that I'm converting into a roller. I already have a 90 roller so was thinking about cutting the mako down to 70cm. I'm planning on using 14mm small ID bands that would utilize the full barrel length to ultimately be stretched to 350%.



Question I have is whether I should use just use the old 6.5mm 120cm shaft or if I should get a 7mm 110cm shaft? Or even a 6.5mm 110cm shaft?



I was reading some stuff that for rollers, it'd be better to have a shaft with higher mass to counteract the shorter spear. Other things I read were it's better to have a thinner shaft. Any new ideas or experience from your guns?


Your not going to get shaft whip with that short of shaft 6.5 in 110cm will be perfect


Sent from my iPhone using Tapatalk
__________________

FII. Level 2 Cert
50M Diver
RBainer is offline   Reply With Quote
Old 09-15-2017, 10:38 AM   #9
fr0sty
Registered User
 
Join Date: Aug 2013
Location: Cambridge, MA
Posts: 150
Re: Shaft for short roller

Quote:
Originally Posted by TVA View Post
How are you going to be securing the bands on the bottom of the gun?
I'm going to install two pegs (https://www.mvd-retail.gr/index.php/...ks-pair-detail) on the sides by the handle and then when I head out, will pull the bands to it to get pretension before actually loading the gun.
fr0sty is offline   Reply With Quote
Old 09-15-2017, 05:40 PM   #10
TVA
Registered User
 
Join Date: Jul 2013
Location: Kailua, HI
Posts: 280
Re: Shaft for short roller

Quote:
Originally Posted by fr0sty View Post
I'm going to install two pegs (https://www.mvd-retail.gr/index.php/...ks-pair-detail) on the sides by the handle and then when I head out, will pull the bands to it to get pretension before actually loading the gun.
Sounds good. You want to anchor the bands as far back as is practical. A big part of the reason that rollers have more power per band than a traditional setup is that the pair of bands that make up a single roller band (sides if you will) are generally longer than the looped band of a traditional setup. More rubber stretched to the same percentage means more stored potential energy. Anchoring them as far back as possible will allow you to make them as long as possible while still hitting your target stretch percentage.
TVA is offline   Reply With Quote
Old 09-16-2017, 04:11 AM   #11
spearq8
Registered User
 
spearq8's Avatar
 
Join Date: May 2009
Posts: 2,829
Re: Shaft for short roller

Quote:
Originally Posted by RBainer View Post
Your not going to get shaft whip with that short of shaft 6.5 in 110cm will be perfect


Sent from my iPhone using Tapatalk

+1 ... even up to 135cm length shaft, you will not get shaft whip on a 6.5mm shaft unless it is a slotted shaft or made of very soft metal. Lack of shaft stability on exit does not necessarily have to mean shaft whip.
spearq8 is offline   Reply With Quote
Old 09-19-2017, 08:36 AM   #12
fr0sty
Registered User
 
Join Date: Aug 2013
Location: Cambridge, MA
Posts: 150
Re: Shaft for short roller

Good to know. What's the harm is using a shaft with a longer overhang (i.e., the 120 vs buying a 110)? Just the aiming is a bit different? Or is it because it basically defeats the purpose of cutting the gun shorter but still having a long shaft?
fr0sty is offline   Reply With Quote
Old 09-19-2017, 12:29 PM   #13
TVA
Registered User
 
Join Date: Jul 2013
Location: Kailua, HI
Posts: 280
Re: Shaft for short roller

Quote:
Originally Posted by fr0sty View Post
Or is it because it basically defeats the purpose of cutting the gun shorter but still having a long shaft?
That, plus the possibility of ballasting issues (i.e. making the gun too nose heavy), and if you go way too long in a thin shaft it becomes much too noodley. It's best to build/select your gun around the shaft you want to use, not the other way around.
TVA is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 08:35 AM.


The World's Largest Spearfishing Diving Social Media Forum Powered by vBulletin® Version 3.8.1
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright ©2002 - 2014 Spearboard.com