Thursday, June 4, 2015

Bear pattern rework number....

... I've lost count by now. 

Even though the sides were smoothish and had some draft to it from my last rework, I think part of my problem is the lack of fillets. In the bit of studying I've been doing about casting, several books mention them but it was actually a short paper by Ian M. Kay from the Cast Metals Institute in Des Plaines, IL. (Who knew there was such a thing? The CMI... not Des Plains, IL. I'll have to check them out. Again, not Illinois.)

The paper is called "Patternmaking 'Tricks' [sic] for Better Castings". Although the paper is relatively short (2 pages) it contains one of the better explainations about fillets, radii, and their importance than almost all the other books I've read through.

I won't rehash here what he wrote but I encourage you to read through his paper if you have a second. There's some good info there.

So back to the bear. I'm not a fan of the wood putty I used the last time I "fixed" the pattern. It was far too gritty and difficult to spread on Masonite. Instead, I thought I'd give Bondo a try. Plus, there's nothing like huffing some MEK peroxide and styrene.

It's been a while since I worked with Bondo. As you may note in the first pic, I mixed up quite a bit the first time. The instructions say something to the effect of "only mix what you can use in a couple of minutes". Boy, they weren't kidding! I barely used any of that first batch before it got difficult to spread. On later mixes, I made much more conservative batches.

It went pretty well though it was difficult to smooth in the tight spots. I figured I'd just take care of that when I was sanding. 

Yeah, difficult location to smooth means damn near impossible location to sand. I did the best I could. 

I think I sanded for probably two or more hours just trying to get all sides as close to perfect as possible. I spent this time because I swear this is the last major rework of this pattern before I scrap it and start over. (Famous last words....)

Once it was smoothed to my satisfaction, I hit it with several good coats of the Rust-Oleum 2x Paint + Primer. As I've mentioned before, I really like this stuff because it lays down a good, thick coat and I don't have to use clear/urethane afterwards.

Also note the board of screws I quickly made to support the bear. This wasn't done as a form of torture for the bear, though some is probably due for the grief he's caused me. It was to support it while making as little contact as possible. This was to avoid having to wait for it to completely dry before flipping it over to do the back side. The re-coat times, according to the label on the can, were within one hour or wait 48 hours. As I'm hoping to try to make a mold in the next day or so, I don't have that kind of patience. 

Here is his new look.

By the way, happy birthday Dad. RIP.

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