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Old Oct 05, 2011, 12:30 AM
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OK, back to it. As I said before this is not a how to do it thread but some shots of important stuff along the way.
There is no difference in making a wing mold or a fuse mold. This is just the way I make my molds. After a couple of decades doing this you get a feel of what works for you.

I do not use Tooling Resin or Gel Coat anymore for the mold face. There was always the problem of chipping on the flange edge. I always use a razor blade to cut the seams and its easy to scratch the wax off losing the release. I now use straight epoxy (ProSet right now) with Milled Fibers mixed in to increase the strength around the edges where cutting will be done.

On the mold face itself I use resin with just a small amount of Milled Fibers in it to help it flow over the tool face. Generally I do two layers to have complete coverage.
The glass can be applied over the second coat when it has tacked up. I usually wait until the next day. It takes so long for it to go off I would rather do it late in the day and then leave it alone.
Normally I use 30 min hardener for these coats, but because its a one piece wing with dihedral I used the 15 min. so it wouldn't end up as a big pool at the center.
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Old Oct 05, 2011, 12:53 AM
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Once the surface coat is cured overnight I scuff the surface to help break the blush and then rinse with Acetone and its ready to start the glass.

The most important layer you can do is the very first layer of .75 ounce cloth. It must be absolutely pin air free. "NO BUBBLES". Then the next layer of .75 is applied after the first has cured. Only because there's no way you can apply that cloth with out wrinkles if its at all sticky.

The layup schedule is:
2 - .75 oz.
2 - 1.4 oz
2 - 4 oz
8 layers of 8 oz cloth. 2 at a time.

I use ProSet Resin through the 1.4 oz layers then switch to a cheaper 5:1 Marine resin we have here locally.

Once I have finished the first side I will post pictures of it before its ready to flip over and start the other side.

Dave
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Old Oct 05, 2011, 04:25 AM
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Milled glass source?

It's looking good Dave. Where do you get your milled glass from?
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Old Oct 05, 2011, 08:11 AM
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Dave, just curious, have you tried just using micro balloons as part of the surface coat? I did this on a recent mold and my mold making friends were very impressed, the mold came out perfectly and the edges are super, super hard. I'm sure your milled fibers method works as well if not better, just curious.

One other quick question, are you letting the first layer of 0.75oz glass cure completely before moving onto the next layer?
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Old Oct 05, 2011, 01:44 PM
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Jim,

I get the Milled Fibers from our local supply house. Its just ground up fiber glass. If you don't have any available I can send you some, let me know.

Sam,

I have never used Micro balloons as an material for increasing strength. Interesting that it worked that well for you.

I do let the surface coat cure before using the glass. There is no way you can get all the wrinkles out of that light fiber if its sticky. Heavier glass not as much of a problem.
In the old days of Gel Coat and Polyester resin molds we would use Vail on the tooling gel as soon as it tacked up. But the finish is not compatible with epoxy. This is why I go with light cloth. Vail is awesome to use as it conforms into every crease with no problem.

Dave
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Old Oct 05, 2011, 02:18 PM
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Quote:
Originally Posted by samc99us View Post
Dave, just curious, have you tried just using micro balloons as part of the surface coat? I did this on a recent mold and my mold making friends were very impressed, the mold came out perfectly and the edges are super, super hard. I'm sure your milled fibers method works as well if not better, just curious.
The tensile strength of micro-spheres and resin is much lower than almost any other filler combination. Most mold edges fail from plucking (tensile failure). Typically micro-spheres are reserved for functions that require a volumizer (reduce density thus reduce weight), reduce shrinkage, or to make the resin easier to sand. Also, if you have to sand the mold surface to make a repair the surface will then contain zillions of micro pores that makes for a problematic release. Micro-spheres are kind of like the "anti-tough".
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Old Oct 07, 2011, 01:28 AM
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Duratec cost.

After comparing the cost of Duratec as compared to 2 pack primer, + 2 pack filler, + 2 pack paint, I am beginning to see that the Duratec comes up favourably. Even given the fact I cannot buy less than a gallon container and that much of it would "go off" before I could get to use it.
There may be a way of decanting small quantities to lengthen the life of this product.

Jim.
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Old Oct 07, 2011, 03:52 AM
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Jim,

I use a product called "Bloxogen" Its a commercial product that is just an inert gas to displace the oxygen in a can of paint or finishing material. Works great for my Bondo cans which always go off on me. One shot of this stuff and it is still good after months of sitting.
You can probably use nitrogen with the same effect. The Bloxogen comes in a compressed spray can so its easy to use.
Check at wood working supply houses like "Wood Craft" which is where I get mine.

Dave
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Old Oct 07, 2011, 04:17 AM
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Jim,

I use a product called "Bloxogen" .................................................. ..............................Dave
Good tip Dave.
I will be using the 2 pack paint that I already have for my current set of wing plugs, but for the next job I will use the Duratec. Sounds the way to go for my small scale hobby operation.

Jim.
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Old Oct 07, 2011, 07:31 AM
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Originally Posted by wyowindworks View Post
The tensile strength of micro-spheres and resin is much lower than almost any other filler combination. Most mold edges fail from plucking (tensile failure). Typically micro-spheres are reserved for functions that require a volumizer (reduce density thus reduce weight), reduce shrinkage, or to make the resin easier to sand. Also, if you have to sand the mold surface to make a repair the surface will then contain zillions of micro pores that makes for a problematic release. Micro-spheres are kind of like the "anti-tough".
Hmm, are you sure we are talking about the same product: http://www.westsystem.com/ss/406-colloidal-silica
?

I've only pulled 1 part form this mold and so far chipping hasn't been an issue, but time will tell.
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Old Oct 07, 2011, 11:31 AM
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Hmm, are you sure we are talking about the same product: http://www.westsystem.com/ss/406-colloidal-silica
I don't know. I thought we were talking about micro-spheres/micro balloons. West Systems 406 doesn't contain any micro-spheres but rather colloidal silica. Colloidal Silica would be much stronger than micro-spheres.
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Old Oct 07, 2011, 12:24 PM
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Originally Posted by samc99us View Post
Hmm, are you sure we are talking about the same product: http://www.westsystem.com/ss/406-colloidal-silica
?

I've only pulled 1 part form this mold and so far chipping hasn't been an issue, but time will tell.
When I read "micro-balloons" I don't think of West 406. Have a look at the West System Filler Selection Guide. West 407 corresponds better to "micro-balloons."
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Old Oct 07, 2011, 04:24 PM
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Originally Posted by samc99us View Post
Hmm, are you sure we are talking about the same product: http://www.westsystem.com/ss/406-colloidal-silica
?

.....................
No. They are different products with different uses.
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Old Oct 07, 2011, 08:50 PM
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.........................
The plug is a Blue Foam wing hot wired as usual but with a lot more sections than a standard wing. Hand finished and not done in a bag as per usual.

The core is done in a wet layup one side at a time.
I use the same carbon I use in the Arrows D tube at 0/90 top and bottom. then a 1.4 oz. finish cloth.

...............................................
Dave
Dave,
Just to clarify this early point about the plug layup method. Do you simply brush the foam cores with epoxy, lay on the glass and thoroughly wet out? Then when cured sufficiently and the LE & TE sanded, prime and fill/sand to surface it up?
I can understand what you mean when you say vac bagging causes some waviness etc.
I like the sound of this. I will do my next wing plugs that way I think.

Good stuff Dave, keep it coming.

Jim.
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Old Oct 08, 2011, 03:49 AM
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Basically thats what I do. I use 1.7 oz kevlar on the LE as on a bagged wing so I don't change the shape when sanding.

Glass the bottom first and add the 1.4 over the top of the carbon. Zip the leading edge carbon flush to the nose radius when it sets up to the right cure state.
Glass the top the same way. When the top layup is kicked but still a bit soft I put it in the bag with the bottom core bed. Pull just enough vacuum to keep it straight in the bed, like 3 hg. You do not want to put pressure on it to distort it in anyway.
I have done this a few times and it works well. I have also bagged a wing plug as normal but with Duratec sprayed on the mylars relatively thick. This also works well. Its about the same amount of sanding and filling either way.
Make lots of LE templates you will need them.

Dave
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