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Old Jul 09, 2010, 11:24 PM
Addicted to building...
Freddie B's Avatar
Omaha Nebraska
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Wow Pdawg, a lot has gone on since my web service has been out for 3 days! Very nice work, photos, explination, etc! I love it but understand that there is a lot involved so a one off would be true love or best for when several examples could be utilized.

I use the same PVA brand, green color, got it in Sun Valley California when I lived there. When I run out wil hope that I can find it here in the middle of the country!

I too find PVA doesn't always give a great uniform coat when spraying it on, and brushing on, forget it! Oh well practice might make perfect one day.

Fred
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Old Jul 09, 2010, 11:43 PM
I don't want to land yet!
Joined Jan 2010
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Fred... I have found in the past, the best way to apply the PVA is to strain it through something fine(like a stocking) and spray it on lightly. You get a better smoother coat that way.
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Old Jul 10, 2010, 12:10 AM
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Strike3

Thanks, and I'll give that a try! Makes sense as paint reacts the same way!

Fred
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Old Jul 10, 2010, 12:14 AM
Current project: Electrolyte
pdawg's Avatar
United States, OH, Dayton
Joined Apr 2004
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Quote:
Originally Posted by NitroCharged View Post
Exactly what is PVA and how did you apply it Bret?
NC,
Basically PVA in a dumbed down explanation is a water soluble solution that adds another thin layer between the plug and the mold. If the wax doesn't work for whatever reason this gives additional protection. In the worst case scenario (been there & done that) you can spray water on a stuck mold and the PVA layer will eventually dissolve and release the plug.

For the small models like a the Micro Stinger I've had pretty good success applying the PVA with a rag cut from an unwanted T-shirt. It usually goes on thin and flows out well to the point that it looks like its been sprayed on. I recycle the rag by washing it in warm water after applying the PVA. For larger models a spray gun is neccessary. Today I might have applied a little too much PVA from the rag but at this point I doubt this minor imperfection will be noticable in the final product.
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Old Jul 10, 2010, 12:30 AM
Current project: Electrolyte
pdawg's Avatar
United States, OH, Dayton
Joined Apr 2004
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Quote:
Originally Posted by Freddie B View Post
Wow Pdawg, a lot has gone on since my web service has been out for 3 days! Very nice work, photos, explination, etc! I love it but understand that there is a lot involved so a one off would be true love or best for when several examples could be utilized.

Fred
Fred,
Yeah I'm trying to take advantage of the time I have in LA to get this project moving. There is still a cockpit hatch and ducting to mold so the project still has a ways to go. I personally love making composite models so I hope the photos take away some of the magic often associated with fiberglass parts. Its just a series of steps to me so anyone IMO is capable if they have the patience. It does take a while to get the first flyable airframe but for high performance models, atleast the work is preserved in the molds if something happens to go wrong at high speed. Having the mold makes those crashes so much easier to handle with grace.
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Old Jul 10, 2010, 02:11 PM
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Originally Posted by pdawg View Post
Fred,
Yeah I'm trying to take advantage of the time I have in LA to get this project moving. There is still a cockpit hatch and ducting to mold so the project still has a ways to go. I personally love making composite models so I hope the photos take away some of the magic often associated with fiberglass parts. Its just a series of steps to me so anyone IMO is capable if they have the patience. It does take a while to get the first flyable airframe but for high performance models, atleast the work is preserved in the molds if something happens to go wrong at high speed. Having the mold makes those crashes so much easier to handle with grace.
I'm sure about that! And you have presented the work well here too. I find that 1/2 the art will be laying up the mold so that you get an airframs stiff enough and still light enough! I've done layups using epoxy, polyester, CA, even tried polyurethane glue once, but if light, flimsy, if strong, heavy????? Just need practice, or I'm hoping to learn even more from this teriffic how-to thread!

Thank you so much! Don't have enough years left to keep reinventing the wheel eveytime I want to learn something new!

Fred
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Old Jul 10, 2010, 09:58 PM
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New Jersey
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I just found your thread. Looks like we did the same thing all day!!

How did you get all that glass done? I did 2 layers of 3 oz, 2 layers of 5, and 3 layers of 10oz. The lighter layers I could do 2 at a time, but once i got to the heavy layers I had to wait until it tacked up because it was so heavy and stiff I would get air bubbles as the glass shifted.

I saw on Fiberglast's website they said you need 3-4 times the thickness of the part which for me is 30-40ozs. I am doing 56. Why do you go so heavy?

Do you still have to use clay after you fill the crack in the parting board with bondo?

Looks awesome man! Great job!

Brian
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Old Jul 10, 2010, 10:01 PM
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New Jersey
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You gotta tell me where you get your glass. Doing areas like around the intakes is a pain in the butt but looks like your stuff goes around curves nice!

Brian
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Old Jul 10, 2010, 10:54 PM
Team30 Micro EDF
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Adelaide, Australia
Joined Apr 2004
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Nicely illustrated Bret.

So the Cabosil is for thickening the epoxy so it doesn't run on verticals, and the graphite is for strength? What ratio is it mixed in at?
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Old Jul 10, 2010, 10:57 PM
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Yes on the cabosil. The graphite is to provide a smooth finish to the inside of the mold. 1 1/2 tablespoons pf graphite per 10ozs of resin. I was only mixing about 4 ozs at a time so I used 1 tea spoon. I am making my first mold now, so I have been learning all this stuff.

Brian

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Originally Posted by NitroCharged View Post
Nicely illustrated Bret.

So the Cabosil is for thickening the epoxy so it doesn't run on verticals, and the graphite is for strength? What ratio is it mixed in at?
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Old Jul 10, 2010, 11:11 PM
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Omaha Nebraska
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If the mold is epoxy, what type? Is it special order stuff just for molds? And if so (which I figure it is) which source do you buy it from, including the cabosil and graphite?

Thanks

Fred
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Old Jul 10, 2010, 11:12 PM
We Do It With FRQZ
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United States, CA, San Diego
Joined Aug 2009
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she looks awsome.... sister in law the jets pretty cool too ill subb lol
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Old Jul 10, 2010, 11:13 PM
DELTAS RULE
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tehachapi, CA
Joined Jan 2006
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looking sweet bret! i do this kind of stuff at work all the time. id love to do a full mold of some 70mm stuff, but it gets pricey when you have to pay for all that resin! cant wait to see the first production fuse!
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Old Jul 11, 2010, 07:25 AM
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New Jersey
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CN,

Don't use West Systems for the mold. UScomposites.com sells it by the gallon cheap!

Let me add to that... Just checked the glass and epoxy I laid up yesterday with uscomposites resin and it is hard as a rock! West Systems always seems to take an extra day for me before it fully cures.

Brian

Quote:
Originally Posted by corsair nut View Post
looking sweet bret! i do this kind of stuff at work all the time. id love to do a full mold of some 70mm stuff, but it gets pricey when you have to pay for all that resin! cant wait to see the first production fuse!
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