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SlowFISH

Removing core from hollow body - how much stretch?

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Hey guys....

  Working on a couple new ideas and I am looking to create a hollow body bait.  I plan to insert a core into the mold to create the hollow cavity - then after shooting, cooling and removing the bait from mold - pull the core out.  I've seen  guys doing hollow body swimbaits in this manner and have watched Franks video a few times that show what i'm looking to do (buthe's dipping the baits.) 

  My question is - does anyone have any ballpark guidance for how big of a core I can pull through a smaller hole to exit the bait... for example - I'd like to create a hollow cylinder of 0.25" diameter in the center of the bait - can I use a .0615" rod to hold it in place and when removing - will that .06125" section of the bait open up enough to allow the .25" to exit without destroying/ripping the bait?  I know ramping from one diameter to the other smoothly would/should help along with oiling the core - but figured I'd ask if anyone has tried this before and can provide any guidance / raito fo diamters that has worked for them that I can use as a baseline to start.

  Thanks!

    J.

 

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My advise would be to get ahold of a basstrix bait and measure it. In my video the blade was flat with sorta sharp edges. From the tail to the main body it was about 2.5 to 3 times the height. With yours being round it would be easier on the plastic. I get a lot of comments about not taking off that bait in the video I should do another one and show how it comes off. One day. 

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1 hour ago, Frank said:

My advise would be to get ahold of a basstrix bait and measure it. In my video the blade was flat with sorta sharp edges. From the tail to the main body it was about 2.5 to 3 times the height. With yours being round it would be easier on the plastic. I get a lot of comments about not taking off that bait in the video I should do another one and show how it comes off. One day. 

 

Thanks Frank.... 2-3 times gives me a ball park to start - know there are probably a ton of variable (plastic temp, plastic hardness,etc) but 2-3 times gives me a good place to start... thanks again for chiming in!

   J.

 

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On 12/15/2018 at 9:58 AM, SlowFISH said:

Thanks again.... I figured there was a ton of trial and error to do it - thanks for helping me sort through some of it!!!  Very appreciated!

 

  J.

 

You just have to get them off quick while they are warm, I got some squid lures here that are about a 300 durometer, and they get them of some mandeals that are really big. All the hollow body frogs are done the same way as well. Just got to be quick.

Edited by Baitjunkys
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Just now, Baitjunkys said:

You just have to get them off quick while they are warm, I got some squid lures here that are about a duromets 300, and they get them of some mandeals that are really big. All the hollow body frogs are done the same way as well. Just got to be quick.

This too, the warmer they are, the easier they seem to slide off the rods.

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Figured I'd post up some info on what I've learned since everyone was kind enough to share with me....

1. I seem to be able to pull about a 3:1 ratio out from a bait with decent consistency.   Meaning I can pull 3/8" diameter rod from a 1/8" hole and not trash the bait... of course there are things you have to keep in mind and do to make it happen and you can go for a higher ratio with certain design features (I think)!!!

2. Make sure you have a decent amount of plastic around the hole you're pulling from.... using my above example - if I have .030" around that 1/8" hole you have more trouble than if you had 1/8" wall around that hole.  I know that doesn't seem to make sense but too thin just rips/tears or doesn't rebound to original shape.... not sure if a really thick wall is an issue as I didn't test - but too thin won't work - you need some meat at the smallest part of the opening/hole.

3. Temp - I found I have more stretch with warm parts as many have stated... but in my case I was pulling a thicker rod through a small hole... so having a cooler bait was better as while the plastic didn't stretch as far - it rebounded better.... I was having some parts deform permanently if they were too warm.  So as usual with this hobby - it's a matter of trail and error on each design!!

4. Insert - polish that bad boy up!!!  Rougher the finish the more of a challenge - totally expected - but I was surprised even the difference between an unpolished piece of aluminum rod vs. polished - makes a difference.  Also - ramping up to the large diameter over a long stretch makes life easier than a blunt step in the insert/mandrel.  Yeah - common sense actually works here!!!

5. Vacuum - I could also up the ratio if I was ok with making a hole in the bait opposite the mandrel I was pulling out.  I found some of the challenge was as I tried to pull the mandrel out of the bait - it sucked down tighter around the insert until I reached a point where air back filled the cavity.  So if you can live with a pinhole or something - you could probably go bigger or get mandrels/inserts out much easier.

6. Just like in any mold - your insert could cause areas to shut off quick and result in sink marks.  In one mold I had much better results with a larger - longer insert that kept the wall thickness more uniform than another insert that shut the bottom of the bait off too quick and resulted in sinks/dents.

 

Anyway - figured I'd post this stuff up for anyone that likes to tinker/play.. Im still still messing around alot to get things how I like them!

 

 J.

 

 

 

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