Molding A Crankbait

[lm22]

I have made a crank bait out of Balsa that I like the action of. I have a template that I made of the side profile, but I can't make the crank bait body exactly the same from wood. Can you make molds of a crank bait body out of silicone and then make them out of resin. If so, how would I get the lip and weight into the crankbait? What silicone and resin would be best for it? 

[Vodkaman]

Your main problem is material density, you will never get the resin bait to swim the same as your balsa prototype. Balsa is extremely light, and with the ballast reasonably centered you can expect a very lively action. With a much denser resin material you will find the waggle a lot more subdued compared to the wide balsa action.

For a first attempt, keep it simple, just mold the body, cut the lip slot and holes as with balsa. This will allow you to experiment with positions of holes and slots. Once you have a prototype that you are happy with, then you can then think of refining the mold design for efficiency.

Dave

[TootsMalone]

1 hour ago, lm22 said:

I have made a crank bait out of Balsa that I like the action of. I have a template that I made of the side profile, but I can't make the crank bait body exactly the same from wood. Can you make molds of a crank bait body out of silicone and then make them out of resin. If so, how would I get the lip and weight into the crankbait? What silicone and resin would be best for it? 

You could definitely make a mold of it and cast copies in resin with microballoons added. BUT, you probably wont get the same action out of it as you do with balsa. You can only add so many microballoons to the resin before it starts affecting the strength and rigidity. Adding ballast is easy and you have a few options there. You could pour in something like bird shot or bb's into the mold while you are pouring the resin, you can drill holes and fill with melted lead, or you can drill holes and insert solid lead or any other heavy metal of your choice. 

I pour my resin copies with about 9.5% microballoons by weight and it gets the buoyancy right around the poplar i use for carving. My guess is balsa would be closer to 11% or higher but i really don't know. Never made or tried to replicate a balsa crank or any crankbait with resin so im just speculating here. Good luck in your search!! 

 

Edit: Listen to vodkaman, he knows his stuff! 

Edited December 13, 2019 by TootsMalone
Vodkaman beat me to it.

[lm22]

38 minutes ago, Vodkaman said:

Your main problem is material density, you will never get the resin bait to swim the same as your balsa prototype. Balsa is extremely light, and with the ballast reasonably centered you can expect a very lively action. With a much denser resin material you will find the waggle a lot more subdued compared to the wide balsa action.

For a first attempt, keep it simple, just mold the body, cut the lip slot and holes as with balsa. This will allow you to experiment with positions of holes and slots. Once you have a prototype that you are happy with, then you can then think of refining the mold design for efficiency.

Dave

Thanks for the advice. What silicone and casting resin would you recommend? 

[JRammit]

The amazing white resin from alumilite is said to be beginner friendly compared to other brands... i used it with absolutely no prior resin casting experience and had fine results with no problems

Others like the smoothe on featherlight stuff, but i havnt tried it so i cant comment

As for RTV silicone, ive used alumilite (the pink stuff) in the past, no complaints... but now i order the blue RTV 45 from Spike-It/Lureworks simply because i order other stuff there too... it works fine as well

[Vodkaman]

Balsa varies in density from  0.07 to 0.2 were water (neutral = 1.0) specific gravity (SG).

Resin with micro balloons is 0.65 at very best. A huge difference. The effect of SG is one of those things that you have to gain experience of.

Best advice; construct first prototypes as close as possible to your final material SG. This is important stuff.

Dave

[Travis]

9 hours ago, lm22 said:

I have made a crank bait out of Balsa that I like the action of. I have a template that I made of the side profile, but I can't make the crank bait body exactly the same from wood. Can you make molds of a crank bait body out of silicone and then make them out of resin. If so, how would I get the lip and weight into the crankbait? What silicone and resin would be best for it? 

Never used resin much...  but 2 part urethane foams I have used over the years for some lures.

Balsa used in cranks is typically 10 to 12 lbs per cubic ft.    You can get  10  lb per cubic ft urethane foam.    

 

 

[mark poulson]

10 hours ago, Travis said:

Never used resin much...  but 2 part urethane foams I have used over the years for some lures.

Balsa used in cranks is typically 10 to 12 lbs per cubic ft.    You can get  10  lb per cubic ft urethane foam.    

 

 

Is that an expanding foam?  What brand?  Do you pour it or inject it?  What are today's winning lottery numbers?  So many questions, so little time!  Hahaha

[Travis]

It is two part expanding urethane foam.  I have always used US Composites but pick your source doesn't really matter.  I always poured it straight from the small dixie cups I mixed in.  No need to over complicate the process but being lure makers.........

You make weighted wire harnesses that slides over the alignment pins (just cut off finishing nails) at the hook and line ties.    I use a story board with all the lures I cast laid out with holes drilled for pins to bend/make my wire harness.   Lay your RTV silicone molds out and then fill about 1/2 full and put the the other half one then stack the molds put cauls on and apply pressure with rubber band or  clamp.  Can make molds out of bondo, POP, or durhams also just need to avoid undercuts or demold earlier while foam is still soft and mold release helps out a lot.   The urethane blooms and fills the cavity and vents out the sprue.  I think I typically demold about 3 to 4 minutes after pouring.  If you get enough molds made you can cast a series then go back and demold and repeat with little dead time.  

My biggest knock was very much a stamping widget process and lacked any creativity and enjoyment for me. 

 

  

 

[mark poulson]

12 hours ago, Travis said:

It is two part expanding urethane foam.  I have always used US Composites but pick your source doesn't really matter.  I always poured it straight from the small dixie cups I mixed in.  No need to over complicate the process but being lure makers.........

You make weighted wire harnesses that slides over the alignment pins (just cut off finishing nails) at the hook and line ties.    I use a story board with all the lures I cast laid out with holes drilled for pins to bend/make my wire harness.   Lay your RTV silicone molds out and then fill about 1/2 full and put the the other half one then stack the molds put cauls on and apply pressure with rubber band or  clamp.  Can make molds out of bondo, POP, or durhams also just need to avoid undercuts or demold earlier while foam is still soft and mold release helps out a lot.   The urethane blooms and fills the cavity and vents out the sprue.  I think I typically demold about 3 to 4 minutes after pouring.  If you get enough molds made you can cast a series then go back and demold and repeat with little dead time.  

My biggest knock was very much a stamping widget process and lacked any creativity and enjoyment for me. 

Thanks.  It is nice to actually be able to understand what you're saying.  Hahaha