TopStriperAngler

Anyone Using Alumifoam?

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Alumifoam is an expanding foam resin from alumilite. It's said to be about equivalent to red cedar in density. It's pretty darn tough but I have found on larger lures with larger hooks the hook rash can get pretty serious. 

 

I am getting cracks in just about all my lures I made with this stuff. Doesn't seem to matter whether I fish or don't fish the lure--they all develop a crack or multiple cracks. Many lures its just a single crack, goes all the way through, usually perpendicular to the length. I have a hypothesis that the foam is shrinking and the wire harness and epoxy prevent the foam contracting. Over time something has to give and it's the foam, developing a crack. The cracks also run through the epoxy. 

 

Just curious if others have had this happen? Maybe I got a bad batch of the resin...let's hope because this foam is actually pretty useful.

 

   

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Posted (edited)

I have one big plug that I never got around to painting and epoxying and it has no cracks. I was thinking if the problem outlined above is caused by shrinking foam inside rigid epoxy I could try just epoxying the area that the hooks can reach and leave a large percentage of the plug unprotected. That would leave space for some contraction and maybe prevent the cracking.

 

I would go unepoxied if I could but this foam gets bad hook rash. Much worse than wood I'd say.  

Edited by TopStriperAngler

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Posted (edited)

Well Alumilite has a good customer service department and they responded to my email contact to them. They suggested trying to add microballoons to the alumifoam in a 10% by volume. I wasn't sure of the volume/unit weight of the microballoons so I tried doing .5g to 32g resin. I waited 48 hours to paint. Waited 72 hours after painting to epoxy with Devcon 2 ton. Fished the next day. Today I find the first crosssectional crack and it's a full split. Will not ruin plug as its away from the hook hanger so that's good news. 

 

It may be that the microballoons worked and I just epoxied a little too soon. But the microballoosn might have weakened the foam to the point that the failure happened with less tension built up in the foam. Who knows! 

 

I'm going to buy some more resin and see if I just got a bad batch. 

Edited by TopStriperAngler

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Alumilite is a good product, but I know some of their stuff has a shelf life, like you say, maybe a bad, or old, batch.

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Yeah Ed and I been quite happy with the Amazin Castin Resin. Happy with the alumifoam too ecept for cracks. I remember I ordered it and it took a while to ship and I was thinking hmmm maybe they having supply chain issues. So I will probably just try another batch. 

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Did you give the alumifoam another go?

 

I was looking forward to trying it but the splitting is concerning.

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1 hour ago, Bait Tailer said:

Did you give the alumifoam another go?

 

I was looking forward to trying it but the splitting is concerning.

I made two more plugs with the same batch of resin which is now over a year old. One I epoxied with D2T and it split about 48 hours later. The other I left unepoxied and its fine. So I think the foam was shrinking and the D2T was preventing it from contracting.

 

Someone said etex might be a solution because it is flexible and would allow the plug to shrink. I haven't tried that yet. 

 

I am hoping that the batch of resin I got was just old even when I got it or something was off about it. 

 

I will probably buy another batch of the stuff but I'll try etex for a topcoat probably.    

 

Aside from teh splitting I really like it. 

 

 

 

 

 

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1 hour ago, TopStriperAngler said:

I made two more plugs with the same batch of resin which is now over a year old. One I epoxied with D2T and it split about 48 hours later. The other I left unepoxied and its fine. So I think the foam was shrinking and the D2T was preventing it from contracting.

 

Someone said etex might be a solution because it is flexible and would allow the plug to shrink. I haven't tried that yet. 

 

I am hoping that the batch of resin I got was just old even when I got it or something was off about it. 

 

I will probably buy another batch of the stuff but I'll try etex for a topcoat probably.    

 

Aside from teh splitting I really like it. 

 

Thanks sounds promising.  I tried the alumilite with microspheres and feather lite this weekend but couldn't get the buoyancy I need for a deep divers weighting. 

 

Alumifoam and 320 is on the way. hope to try a few combinations and layers next weekend. 

 

 

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Posted (edited)

5 hours ago, Bait Tailer said:

Thanks sounds promising.  I tried the alumilite with microspheres and feather lite this weekend but couldn't get the buoyancy I need for a deep divers weighting. 

 

Alumifoam and 320 is on the way. hope to try a few combinations and layers next weekend. 

 

 

 

What I been doing with these molds is make a harness and then cast just alumifoam without any weights. Then use that piece for float tests. 

 

So I did the archimedes dunk test with two of these pieces to find volume and the neutral buoyancy weight. 

 

The following weights for these two plugs includes a throughwire with loops on each end so this isn't just alumifoam here. 

 

Spook weighs 21.4g and volume is ~59cc. Would sink in saltwater at about 61g total weight.   

Pencil weighs 19.5g and volume is ~56cc. 57 or 58g saltwater sink. 

 

The spook specific gravity (21.4g/59g) is .32 which is about equal to red cedar. The pencil is .34. 

 

So as you can see there's a lot of room for lead with this alumifoam. The density can vary depending on how much you put into the mold and how easily it can escape as it expands. It can be "packed" if it can't escape easily and that would make more dense.

 

 

 

 

 

Edited by TopStriperAngler

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On 8/1/2022 at 0:42 AM, TopStriperAngler said:

 

What I been doing with these molds is make a harness and then cast just alumifoam without any weights. Then use that piece for float tests. 

 

So I did the archimedes dunk test with two of these pieces to find volume and the neutral buoyancy weight. 

 

The following weights for these two plugs includes a throughwire with loops on each end so this isn't just alumifoam here. 

 

Spook weighs 21.4g and volume is ~59cc. Would sink in saltwater at about 61g total weight.   

Pencil weighs 19.5g and volume is ~56cc. 57 or 58g saltwater sink. 

 

The spook specific gravity (21.4g/59g) is .32 which is about equal to red cedar. The pencil is .34. 

 

So as you can see there's a lot of room for lead with this alumifoam. The density can vary depending on how much you put into the mold and how easily it can escape as it expands. It can be "packed" if it can't escape easily and that would make more dense.

 

Great notes.  I hadn't considered the packing, but makes sense - looks like it expands and sets up pretty quick.  I'm trying to match a few pine and AYC prototypes with a weight transfer system.   I overlooked the buoyancy until I saw the specific gravity chart but this should give me enough wiggle room.  

 

 

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One other thing on the alumifoam is that in a cast piece anywhere the internal cell structure is exposed you get bubbles or little cavities in your paint. So where the seam on the mold is and the spru hole. And any where you sand the skin even a little bit.  

 

I just tried coating the seam flash area and spru with some wood filler--Elmer's Carpenter's--and it seems to have worked. Another spot where I barely touched the plug with some sand paper I failed to coat with the filler and it's showing bubbles. Next time I might try wetting the filler a little bit once its on the plug to try to get it into all the holes.  

 

Right now I made two plugs with my old batch of alumifoam and am going to coat with etex after about four days and see if these split.  

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Etex doesn't seem to solve this problem. I made a new spook, waited 4 days to cure, and etexed. I've had it in the car and fished it for two weeks. Today finally put some fish on it. They whacked the plugs several times on cobbly shoreline. There's three crossectional cracks in the topcoat that weren't there yesterday cause I been checking it regularly. 

 

Meanwhile a plug I made a year ago, fished with no paint or finish for a couple months, then epoxied, then painted, is still going strong no cracking. 

 

 

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