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Posted 30 April 2008 - 03:52 AM
I have been working with polyester resin with microspheres for my lure bodies. My problem is that I am not achieving the density that I want. The best that I can get is 0.75 (water = 1.00), but this mix is like mustard and has to be injected, giving air bubble problems.
I am asking for one or two of you guys that are using this technique, to take a couple of measurements for me.
Take a plain body cast (no lips, hangers, paint etc), any size.
using cotton thread, tie on lead (must be lead) until the body just suspends.
Weigh the body
Weigh the lead
PM or post the results with a description of how you measure out the resin and microspheres.
From this information I can calculate the density that you are achieving and compare it to mine. I suspect that I have managed to procure a very large bag of the wrong stuff!
Many thanks in anticipation of your help.
Posted 30 April 2008 - 08:54 AM
Vodkaman, is this material you are speaking of anything like Alumilite? And are you refering to something akin to microballoons? If so, I will take measurements you ask for tonight as I am going to cast some more baits.
Posted 30 April 2008 - 09:12 AM
Micro balloons are the same thing, the alumilite is different. But please go ahead and do the test, the information would be useful. Thanks.
Posted 30 April 2008 - 11:29 AM
I think I know what you're trying to do but let me jump in with a couple considerations, not criticism, just observations from previous experience & experience shared here before.
Polyester resin is a brittle material, make sure you test it for impact resistance before getting too far in the project.
Polyester resin mixed heavily with fillers like calcium carbonate derives what most of us know as bondo or body filler. My last tinkering with this stuff was to add alumina powder to offset heat absorbsion in a poly soft plastic mold (didnt help)
Also, I've heard actual water density is based on temperature, or temperature affects specific gravity. I cant remember which way, but I think that colder water increases it's gravity........ in other words, a perfectly balanced, neutrally bouyant lure might actually float or sink depending on the waters current temperature.
Other than that, your experiment is on target.
I'm preparing to try the graduated beaker & scale method to try & understand (mathmatically) what you're doing now. I think Lapala & Skeeter might have some experience with this also.
Just some helpful info, I hope.
good luck, take notes (I know you will)
Posted 30 April 2008 - 11:35 AM
I use Aluminite RC3 Urethane resin with Micro balloons.
I measure the resin 1 to 1 with a scale, I add the micro balloons
by volume to about 80% of each container before mixing containers together.
Posted 30 April 2008 - 07:31 PM
Coley.... you are bringing back memories. The amount of micro balloons is roughly trial and error but Coley just got you close. To thick and it won't poor...to thin and the bait sinks. I have some of Coleys baits and the pours are fantastic.
Posted 01 May 2008 - 08:03 AM
Tally, sorry I didn't get to the meet, would have been fun. From what you are saying, that the microspheres are only going to grab a little buoyancy, I can assume that the spheres that I bought are correct.
Jerry, yes the resultant material is brittle and it's resistance to a good rockin' would need to be evaluated. It maybe that the cushioning effect of the epoxy top coat plus the reduced speed of the cast due to the trailing line, would be sufficient to maintain the structural integrity of the lure.
If someone could do the measurements whether with polyester resin or any other type of resin/plastic material, I would appreciate the help.
Posted 01 May 2008 - 08:37 AM
OK, here goes. I hope this is somewhat close to what you are looking for. Last night I poured some lure bodies and tried to get measurements you asked for. Hope this helps.
Alumilite body @ 16.1 grams needed 8.4 grams of lead to suspend. It suspended approx. 3 inches from the bottom of a 24 inch bucked filled with cold water.
WOW, that is the most scientific I have been since I was in high school (early '60s). What an experience.
Should this not be what you are looking for, I apologize. Please give me an E for effort.
Posted 01 May 2008 - 09:40 AM
Vodkaman, sorry, I failed to note that mixture of Alumilite was 1 part A, 1 part B, and 2 parts microballoons.
Posted 01 May 2008 - 03:05 PM
Are you sure you are using the correct resin.
Around these parts (TN) polyester resin is used for laying
up fiberglass cloth.
It is very heavy.
Alumilite RC3 is not as heavy as polyester resin, in fact
it is a urethane resin.
Hope this helps you.
Posted 02 May 2008 - 04:42 AM
Capt David, precisely what I wanted, thankyou.
You are mixing by volume I presume. These figures give a body density of 0.678gm/cm3 and a body volume of 23.8gm.
The ratio of microshperes that you are using is 50/50 (1 part A+B plus 1 part spheres), this is considerably less than I am adding to achieve density of 0.75gm/cm3.
I will try the RC3, as It will be possible to get down to 0.5 which will be representative of bass wood. I may have to invest in a vacuum chamber, as the higher proportions of the spheres does thicken the mix somewhat (like english mustard!). But by injecting with a cake syringe, I can get the mix in the mold. Five minutes in the vacuum chamber should get the air bubbles out, with still enough time to pour five molds.
But to get down to the densities that I want (0.25gm/cm3), I will have to change to foam.
RC3 has a pot life of 3min, so that will limit my operation. Also, the density of RC3 is 1.05gm/cm3, compared to polyester resin at 1.2gm/cm3, this is a fairly significant difference.
Edited by Vodkaman, 02 May 2008 - 04:51 AM.