Jump to content
checkonetwo

Resin Swimbait Issues

Recommended Posts

I've been tinkering for several months with a couple of resin swimbait models. Molds are good (vacuum degassed silicone). Sprue holes and vents are properly placed. I've gotten very good results with straight pours (using no pressure pot, just burping and vibrating). But, I want perfection, or as near as I can get...

I have now experimented with degassing my resin, and with pressure casting. I have even degassed my resin AND pressure cast...Here's what Ive noticed. In order to get the buoyancy I'm after (using alumilite 7 minute), I'm having to use a ridiculous amount of MB's. The resin is getting tons of introduced air. And the shrinkage in the pressure pot is ruining my casts. Huge voids at the top of my lures...I've incresed the holding capacity of my sprue holes, to make up for the shrinkage...but what appears to be happening is, the resin is losing the battle. It can't flow down into the mold due to the amount of air wanting to come back out, due to the shrinkage.

Yesterday I experimented degassing the separate parts of resin, after mixing in the mbs...but because I had to use tall cups, my mix ratio ended up being off (due to material loss on the bottom and side of the cup). The pour ended up a mess, with too much resin, not enough hardener. I will attempt this technique again, with adjustments made for the loss.

I've got some questions for the seasoned pros.

1. Can pressure casted PU lures ever be Consistently bubble free? Or are imperfections just unavoidable? I've heard of seasoned veterans still having imperfections that require puttying, bondoing, sanding...etc.

2. In your opinion, is pressure casting even worth the extra time, and material cost? If you plan on selling your lures, the hours spent fixing imperfections can ruin your profit.

3. What do you guys do about shrinkage during pressure casting? Do you have HUGE reservoirs of resin? Do you do what I mentioned above, and degass your resin first? What are your methods if so?

4. This is a clear coat question. I've now tried two different types of epoxy. A 30 minute I bought at hobby lobby...and envirotex lite. After some reading in these forums, I've learned to mix DA with the 30 minute, and breathe on it, and use a fine hair brush...these are techniques I will try...The envirotex lite worked well for me, but I still ended up with a strange, uneven coat (even using a turner, which I made out of a baby crib mobile). The clear coat ended up with "dry" spots where the epoxy didn't fill...very strange. Any ideas what caused this?

Apologies for the projectile vomit of info and questions...I've been working on this stuff for months...and it seems like one step forward always leads to one step back.

Link to comment
Share on other sites

I also have been making resin baits for years and continue to have similar issues but have learned to work with them. I have never tried the vaccum mold so I can't help there. I continue to have the bubble issue when making baits, which usually occurs in the same spot within a specific mold. When this occurs I just use a small hole punch to create another spru hole and this usually improves the issue with that mold. When I do have a cavity in a lure it is filled with the next run of baits by placing an uncured drop of resing in the cavity. I wish I could pour the perfect bait without any imperfections coming out of the mold but have been unable to do so. Prior to learning about resin baits I would hand carve lures, which also involved a lot of sanding. This was very time consuming. Even though there is often some work with a lure out of the mold I am able to make so many more versus hand carving and therefore have accepted the issues.

 

The dry spot that you refer to appears to be the same issue I have with my first coat of epoxy. Recently I posted about this issue under "primer for resin lures". I think that was the tag. I have the same issue with the first coat of epoxy. For the past several years I put a coat of epoxy on the lure before painting and then a final top coat and never have the dry spot in the final finish. This is an extra step but gives a very smooth surface for painting. I do lightly sand with 400 grit sandpaper as it seems to help the paint stick better.

 

Jim

Link to comment
Share on other sites

I am not sure what you mean by pressure casting. It seems to me that you only have a short working time, and so mixing such a volume for a pressure pot would require a lot of molds.

 

My resin/Mbs experience was with regular resin, the kind used in fiberglass. This resin has a Specific Gravity (SG) of 1.2 (water SG=1.0). This means that the amount of MB's to get a body SG of 0.65 - 0.7 is huge, and the mix is more a paste about the consistency of English mustard.

 

The effort to mix in the MB's means that there will be air, but the air cannot rise due to the thickness of the paste. I removed the larger air bubbles, by spreading the paste thin up the side of the mixing container with a knife.

 

Obviously a paste cannot be poured. So I injected with a cheap ($1) cake icing syringe. This worked very well. With a good cleaning strategy, the syringe will perform hundreds of injections.

 

The results were very good. There will be the occasional one or two bubbles at the surface, but you can fix a dozen lures at a time with a thumb size mix of bondo.

 

As for your 'fisheye' epoxy problem. This is probably caused by contaminants from the resin. The casts should be kept for seven days to fully cure and then scrubbed in warm, soapy water. This should eliminate the problem.

 

Dave

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...


×
×
  • Create New...
Top