Urethane material list?

10 posts in this topic

Hi guys, been lurking for awhile and trying to make my own baits for a little longer:wink:

I'm hoping to start using urethane for my baits as opposed to carving them out of wood and was hoping to get some info on what I will need.

I'm going into this completely blind so anything, no matter how elementary it might seem would be greatly appreciated.

My baits are all between 7 and 14 inches with the majority around 10". Topwater and sinking as well.

Materials, tools, tips, anything would be a great help.

Hopefully I will be able to offer something in return someday!


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I was going thru the member tutorials and found one by a Sr Member named Husky titled "Making A Bondo Mold and Expandable Foam Lures". Sadly, all the pixs in the file seem to have been lost in the great server crash some time back. Still, it looks like Husky is still an active member and he may be able to replace the photos.


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Bruce is right, Husky is the main man for this type of construction. Do a members search and read everything that he has written. Then ask a few questions and you'll be an expert in a few days!

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Re: mold for crank baits

Mike P (Husky here) PM any time.

Read this;

TU lost all pictures, but the Freeman site is the best for what you're looking for.

You'll want to make a 2 part Silicone mold.

Michael @ Hobbysilicone is great. You can get most supplies from him. His Prices for Silicone in 10 lb Tubs is VG.

or Call theses guys for Urethane Resin. Tell them exactly what you want to do. Very reasonable and helpful. The will stagger you with info.

Get your 3M glass micros here.

Originally Posted by Coley

Micro Balloon Formula for Urethane Resin (Alumilite is a UR)

Here it is;

First of all let me say this about Alumilite. It is really great stuff for

making bass crankbaits. It comes in part A and part B. It has no

fillers, until you add one. The mix ratio is 1:1 by volume or weight.

I use weight for the resin and volume for the filler, in this case

Microballons. Using no filler the bait will sink, using 50% filler the

bait will suspend and 100% filler the bait will float.

What I do is this.

I pour some part A into a clean half-pint jar (at this point it doesn't matter how much)

I pour some part B into a clean half-pint jar (at this point it doesn't matter how much)

lets say both jars are 1/2 full. Add 1/4 pint Microballons to both jars. This will give

you a 100% mix. Then using a scale I weigh out equal parts of A & B, mix and pour

into mold. You need to mix the Microballons into each part, before mixing

them together. You only have 2 1/2 to 3 minutes to pour after part A & B get


So far, I have seen no separation of the microballons from the resin..

I am pouring all my molds from the tail end of the bait, this eliminates

a big sprue to remove and sand down on the top or bottom of the bait.

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I recently set out to do what you're asking about to make a bait similar in construction to a triple trout, but with my own additions like facial features, different profiles and tail attachment. All carved in basswod masters.

For mold material, I used the OOMOO line of RTVs from Smooth-on Inc. mainly because I didn't want to mess with vacuum degassing. But with most RTVs the degassing helps eliminate bubbles....and you will get bubbles.

The OOMOO line works fine for the Urethane resins, but may a bit too soft for foams..if you are planning on using the foam, some of the harder RTVs like ReoFlex 50 or 60 may work better, but require degassing. BTW this RTV stuff is pricey.

For large pieces, a 2 part RTV mold will work best. I made mine just like the tutorials on this site, and at other casting sites. Like Tap Plastics for instance. Petroleum jelly works as a release agent to keep first RTV half from sticking to the second half. Just a very thin layer applied to the first half before pouring the second is all it takes.

For smaller pieces, I made a 1 part molds and used a razor to cut about 1/2 way around the master after it cured so I could extract the castings. Used the razor to cut a pour spout also.

For casting material, I'm still experimenting a bit. First try was with the Task 3 resin from smooth-on. I wanted the 7 minute working time for the first tries, but I'm looking to try out the faster curing ones next.

With the task 3, a 50% by volume addition of microbubbles will make a very slow sinker...almost suspending, but it'll pop to the suface and wake nicely with a slow retrieve. At 75% by volume of microbubles, it gets pretty thick to pour but the bait will float....just what I was looking for. I didn't add any ballast weights to the first ones, and they swam very well.

My pour holes for the molds are on the backs of the pieces, so if the microbubbles wanted to float up before the resin cured, I'd get a little "automatic" belly weighting. Not sure if that matters much, but I thought it was the best way to go.....without having to experiment too much.

One note about the Task line of resins. They say they are designed for up to 1/2" thick castings. I've done up to 3/4" without deformation problems.....your mileage may vary.

And one more thing for all the amazing guys on this site....:worship:

My stuff isn't worthy!

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Updated after experimenting with a fast cure Task line of casting resins from Smooth-On

I tried the Task 8 mainly because it has a lower density & viscosity. Lower density so it requires a little less of the micro bubbles, and lower viscosity for easy pouring.

With this resin I ran into the reason they say it should not be poured for things over 1/2" thick. The section I poured with no problems with the Task 3 resin (just under 3/4") developed surface blisters with the Task 8. I might experiment with trying to slow down the reaction time by cooling the components prior to mixing, but maybe I'd be better off with a different resin on the thick castings.

For the thinner sections it worked great, it's strong, pours good, and the surface finish is nice, less problems with bubbles due to the lower viscosity....I like this stuff except for the above mentioned problem.

I have an order in for some Alumilite to see how it compares. One thing that bothers me about the Alumilite web page is that they don't post any spec sheets, so comparing material properties isn't possible. That's why I started with the Smooth-On product. I could see right away how the Task line compares to the Smooth-Cast line, and chose the stronger of the 2 to begin with.

Anyone have any spec sheets on the Alumilite casting resins?

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Thanks Coley, looks like Alumilite is very comparable to the Task 3 & 8 resins. I tried it out in my largest mold and had the same problem I had with the Task 8....surface blisters. SO, I went back through all the literature I had and found that it's recommended to heat the mold up to 140-150 Deg F before pouring the fast cure resins..not sure how I missed that!

Anyway. heating the mold is the ticket for these fast cure resins on thick castings...came out great!

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