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Hard Foam Casting

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#1 biggamefish



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Posted 08 April 2013 - 02:44 PM

hey guys im looking into trying to make some jointed swim baits out of hard foam, im looking for a foam that floats/bouyant like wood or have the same density as bass wood or popular and good impact strenght, ive seen all the 3 up to 16lb foams but i do not know what it stands for or which one would be ideal for my application lol. 


I've made a 2 part mold that i used for casting urethane resin baits, was thinking of using the same 2 part mold for casting the hard foam, how do i figure out how much foam liquid to pour inside my mold or how do i go on about trying to cast a bait out of the hard foams? 


any helps or suggestions is greatly appreciate!


#2 quickdraw



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Posted 08 April 2013 - 09:40 PM

Scroll down through these videos and there is 1 or 2 using foam. Go to the products page and there are several foams and they tell you the expansion rate. You can call their 800 number to ask questions of what product will meet your needs.



#3 jkustel



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Posted 09 April 2013 - 01:43 AM

The numbers such as 3lb, 10lb, etc. indicate how much a cubic foot weighs which is a measure of its density. The lower the density the more expansion occurs (allowing it to capture more air when it cures). This material shows good promise in terms of its density when trying to mimic light weight woods as well the strength is very impressive and increases with higher densities such as the 16lb and 25lb. 


So why aren't more folks using this stuff? It is much more difficult to pull off clean castings using silicone molds due to the expansion. Even with large vents in your mold the pressure it exerts even when compensating for the expansion is troublesome-it is very difficult to avoid distortions and material pushing into the mold half parting lines and seperating the halves. Has the headache started yet?. 


Also the finished casting seems to have more voids and defects than urethane and at the least will require quite a bit more clean up such as filler to prep it for paint. Which brings yet another issue. Getting paint to adhere to it is much more difficult as well. There are methods of pre-priming the molds that I was only able to get a fair result from.


To sum up my experience. If your super motivated to use this material you had better be prepared to invest some serious time and effort to master it as it is much different than working with urethane resin. It certainly can be done but you have to basically make a study of how to deal with the expansion, achieving a nice skin to minimize paint prep, and getting good paint adhesion. If your making simple designs like big spooks or ms slammer type wake baits it might be fine. If your attempting more detailed casting with scales, fins, etcs...its going to be much more challenging to deal with. Also, the expansion is affected by things like temperature and humidity so keeping your densities consistent might not be as predictable as the number on the label. 


Personally, with all the additional issues over urethane resins I opted to look at other ways to make the urethane resin lighter where need be. Larger swimbaits in general don't often perform optimally with the densities of light woods such as basswood or cedar. If your looking for more buoyancy you don't necessarily need a lighter material you might instead add more volume to your design (make it fatter). In other words, instead of fighting your material...re-engineer the shape to work with the material your using. Urethane resin is a DREAM to work with next to urethane foam but if your super  motivated you could possibly discover new ways of taming the beast that others haven't. 


Good luck.


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Posted 09 April 2013 - 11:24 AM

Where are my baits, John?

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#5 slideaction


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Posted 09 April 2013 - 10:00 PM

^likewise would like to know as well but u can always return the money too. I can fwd my address to ur facebook or here if u lost it

Edited by slideaction, 09 April 2013 - 10:05 PM.

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#6 Anglinarcher


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Posted 09 April 2013 - 10:51 PM

I beg to differ a bit with the negative rap on the foams.  OK, maybe I am just a super design and pour guy, but I always use foams.


What I usually do is pour mine from Alumilite products.  I make up some Alumilite White with microballons, a small amount, and I pour it into the mold and rotate the mold to distribute the material.  This coats the inside of the mold and provides a very paintable surface.  I then make up the foam and pour, allowing the extra to come out of the vents and pour holes.  The key is to mix fast and pour faster.


The Alumifoam skins well and has the same density as a white cedar.  This stuff is more difficult to pour without over expanding, but figure it will expand a little more then two and a little less then three times the original volume.  This stuff is so tough that it is almost hammer proof.  When using a silicone mold, I normally have a couple of plywood boards for the sides and I put a couple of clamps on it to help maintain dimensional stability.


The Alumilite 610 (6 pound density with 10X expansion) foam has about the same density as balsa and is about as tough when it comes to pull out of screws as balsa, but it is a bit more resistant to breaking.  I use through wire construction in the mold when I pour with this material.  This stuff extrudes out of the pour holes and vents when it is still pretty soft.  I normally just hold my mold together with a few rubber bands.  I use this stuff with the Alumilite White skin and so far even muskie have not destroyed it -- but one did shatter when it hit a rock cliff at high speed on a cast.  LOL


I find that both of the Alumilite foams mentioned skin smooth.  They clean up well with a little sandpaper and a bit of wood filler fills any imperfections.  I also find that if I hit the material with 600 grit sandpaper, hit it with a little alcohol, then mist it with a rattle can of clear lacquer, any paint will stick to it.  FYI, this is just what I do with wood lures that I seal first.


I cannot comment on other foams, these are the ones that I started out with.  I tried the Alumilite 320 and found it to be far to soft for my use, but with an expansion of about 20 times, who knows what can be done with it.


I would not discount the foams for your uses; they are just different.  With a little practice, you can make excellent lures from it.  I have attached a picture of what I do with these foams, and for what it is worth, I think this is more then a simple spook, etc.....

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#7 capt mike

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Posted 01 July 2013 - 11:01 PM

hey AA,  when you rotate the mold with the urethane resin, what about clogging the vent holes?  How big are the holes?  Can you post a pic of a mold that you use with the foam?