Making molds and casting pieces - update.

[Mark42]

I had such good encouraging results playing with fiberglass resin and silicone rubber caulk, (see post http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=26;t=002236 ) that I ordered real mold making supplies. Got a molding kit with two 1 quart containers of polyurathane compounds. They mix 50/50 and harden in 24 hours.<br /><br />To test this new stuff, I made a mold of an aluminum rub rail end piece that I can't find replacements for. I mixed up the mold compounds and poured it over the end piece and it hardened overnight. The next day I mixed up fiberglass resin and mixed aluminum/silver powder (fine like baby powder) and poured into the mold. After an hour it was removed. The pic below shows the mold on left, the original end piece in center, and the new cast piece on the right. The new piece is not painted, it is the aluminum /silver powder that gave it that coloring. The new piece has some imperfections because I used a bit too much release agent with the resin (wd40), but it sure will make a nice replacement for the other missing pieces! The others should come out even better.<br /><br />

<br /><br />Right now I have a mold hardening for the MFG logo and will post some pics of that when I get to casting some pieces.<br /><br />Mark.

 

[lawyertob]

Re: Making molds and casting pieces - update.

Mark,<br /><br />Very cool. I am impressed.<br /><br />Congrats,<br />Joe

 

[18rabbit]

Re: Making molds and casting pieces - update.

Great stuff, Mark! This is inspirational. Info on a source for the mold making stuff???

 

[Mark42]

Re: Making molds and casting pieces - update.

18rabbit,<br /><br />Sure! Here is the website I ordered the mold making supplies from, they specialize in making casts of body parts, like hands and pregnant torsos, but this product is not for use on people. I ordered this stuff because it will make hundreds of castings and you get a lot of product for the dollar, and it makes very detailed molds. The only real drawback is the 24 hour cure time. I used the medium hardness, and is harder than 100% silicone caulk, but softer than a gum eraser. <br /><br /> http://www.artmolds.com/product_details.cfm?product_id=196&page=0&cat_name=Resin - Urethanes <br /><br />The aluminum/silver powder was given to me about 20 years ago by a guy in the powder metal business, since retired. I only have about 1/2 pint of the stuff, so if it works well and I run out, I'll be looking for a supplier or substitute. <br /><br />The resin is just plain polyester fiberglass resin.<br /><br />I think experimenting like this is really great fun. But the only one in my family who thinks this is cool is by 6 yr old daughter! <br /><br />Mark

 

[BillP]

Re: Making molds and casting pieces - update.

Mark, <br />That is very cool. Thanks for posting the info. Are you planning to use regular poly for the final products (instead of poly casting or epoxy)? <br /><br />I don't know if it is still practiced in the industry but aluminum pellets, balls, etc were used in making small molds and cast parts to keep them cool. In production they pushed the time envelope for cure so heat was always a factor.<br /><br />Thanks again for posting.<br /><br />bp

 

[Mark42]

Re: Making molds and casting pieces - update.

Bill,<br /><br />Right now I am going to use the poly because it is much cheaper than the epoxy. Poly resin should hold up well in the boating environment (I should hope so! I think my whole boat is made out of it!). Plus it is clear so it takes to being colored well, especially with aluminum powder. The Marine Tex epoxy I have is white and and too thick for pouring. But I can always experiment. So far the first pieces I made from a silicone caulk mold are still fine, have not warped or cracked. Going to nail a piece to the back deck so it gets exposed to weather until spring and see how it looks.<br /><br />Has anyone ever tinted poly resin by using paints or dry paint pigments?<br /><br />Mark.<br /><br />Ps, how do I calculate how many gallons of mold compound I will need to pull a mold off my neighbors 23 foot cruiser?

 

[swimmin' for shore]

Re: Making molds and casting pieces - update.

Hi Mark. Since it's poly, I think you can gelcoat it for color. On the amounts of compound, ask JoeGlastron if you don't get another answer. Keep it a secret, but I think he's a genius. I just don't want it go to go his head.<br />Question here: Your original piece is of aluminum, and the casting is of poly. I don't know much about rubrails or how they go together yet, but will the poly piece take the stress that aluminum would? I guess it's a new concept to a lot of people, but I'm just curious. The piece looks incredible, though, whatever the case may be. Great job!

 

[jimmythekid]

Re: Making molds and casting pieces - update.

he sure is good at math

 

[swimmin' for shore]

Re: Making molds and casting pieces - update.

That's no joke. I think that secretly, he probably has one of those programs that allow you to just input your equations and then answers your problems for you. I don't want to turn the man into deity just yet.

 

[Mark42]

Re: Making molds and casting pieces - update.

Swimmin,<br /><br />The piece in the picture is really just a finish trim piece. They dress up the ends of the 5' or so of rub rail on the side of the boat just above the water line. If you look close at some pics of my boat you will see they are missing and a little piece of duct tape is covering up the screw hole until I can get these made and mounted. Lucky for me the boat still had one on it when I got it.

 

[BillP]

Re: Making molds and casting pieces - update.

Mark,<br />I thought the poly might be a little brittle without glass fibers in it. Maybe the aluminum will do it.<br /><br />Yes, for color in poly you use pigment mixed with the resin. Pigment comes in transparent or opague. Be sure to use enough or the color will look "weak". Find pigment at any decent fiberglass supply house. If there are any surfboard mfgs near you they WILL have it too.

 

[Mark42]

Re: Making molds and casting pieces - update.

BillP,<br /><br />I thought it might be brittle too, but some logo pieces I made a few weeks ago can still be bent about 15 degrees from flat without snapping. One problem I see with using fiberglass in the mix is that it might not fill in the small crevices in the mold and may show in the face side of the piece. I need something smaller like the micro bubbles I read about somewhere. <br /><br />Right now I am polyurthaning some doors in the basement and the resin is hardening on some pieces. Man, it really stinks down there right now. <br /><br />Mark.

 

[lawyertob]

Re: Making molds and casting pieces - update.

Mark,<br /><br /> I haven't used them, but I saw a selection of pigments on the US Composites website pigments link . I have heard that it takes quite a bit of pigment to get good strong colors....but again I have not used them at all, that is just tribal knowledge that I have read. I wonder whether using a lot of the pigment effects the strength of the resin at all?<br /><br /> You might want to do a search for "chrome". I read a few threads a while back talking about some chrome type paints that are supposed to work pretty well.<br /><br />Just my $0.02 worth,<br />Joe

 

[KaGee]

Re: Making molds and casting pieces - update.

Originally posted by Mark42:<br /> BillP,<br /><br />I thought it might be brittle too, but some logo pieces I made a few weeks ago can still be bent about 15 degrees from flat without snapping. One problem I see with using fiberglass in the mix is that it might not fill in the small crevices in the mold and may show in the face side of the piece. I need something smaller like the micro bubbles I read about somewhere. <br />

I was wandering the same... maybe the microfiber sold as part of the West System?

 

[Eggkr8]

Re: Making molds and casting pieces - update.

Hey Mark, <br /><br />Logo's and pieces like like, I bet they would be ideal for that Vaccuum chroming procedure that was tossed around in your Spotlight posting a few weeks ago!<br /><br />Just a thought<br />e

 

[Mark42]

Re: Making molds and casting pieces - update.

Joe,<br /><br />Thanks for the link!

 

[ThomWV]

Re: Making molds and casting pieces - update.

I thought you might be interested in a source for the aluminum powder, you can buy all if it you want at your local friendly West Marine store (or Boat US, or Boater's World, and an awful lot of private shops too). West Systems (not a part of West Marine) makes it as something that can be added to their epoxy system in areas where direct sunlight will be on the epoxy. The aluminum acts as a UV inhibitor and also gives the epoxy much greater surface hardness, to avoid scratching. I've used it mixed in with both poly and epoxy, no wetting problems with it. You do have to keep the stuff dry (explosion potential) and it is pretty expensive as I recall (last can I bought was a couple of years ago), but its certainly available.<br /><br />I like those pieces, but I tend to agree that some sort of fiber would probably give me more peace of mind.<br /><br />Thom