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Old Jul 11, 2010, 11:22 AM
Current project: Electrolyte
pdawg's Avatar
United States, CA, Torrance
Joined Apr 2004
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Tumbler,
Yeah we both had long days! I would consider 80 oz. of fiberglass on this size mold a little overkill but not by much. I was taught to make production molds so I generally produce molds that could withstand 500 or so pulls. I don't plan to make that many but it hardly takes any time to put on a couple more layers of 10 oz cloth to beef up the mold... so I do it. 3-4 times the thickness of your part should work however...its really preference at that point and I don't want a flimsy mold that I have to be gentle with.

As you experienced the heavier layers of cloth will resist sharp angles so the layup schedule needs to be designed to gradually build up the radius around those curves. I can't stand having to babysit the fiberglass so IMO I would much rather be conservative and do 2 light layers of cloth rather than one heavy one that might need to babysitting. The Electrolyte had plenty of sharp bends and the early layers required the most effort. As the layers piled up it actually got easier. In your case I would consider more layers of light cloth around the edges giving you trouble prior to going to the heavier cloth.

Responding to your question, the use of bondo on the splitter box gave such a tight fit that I didn't feel it was neccessary to use clay or spackle afterwards. Whatever small gap remained was filled in by the wax and PVA.

NC,
I was taught to use the graphite powder not primarily for strength but to make the epoxy black so you have a color contrast which helps for laying up the fuselgae. The strength should be provided by the fiberglass and not the gel coat. Actually the graphite powder increases the chances for chipping of the mold so I usually put in just enough powder to make the epoxy black.

CN,
yeah I can't wait to see the first fuselage out of the mold also. Its always an exciting day...like the birth of a child. BTW, the cost of making a mold is not cheap but if its something worth molding then it could easily pay for itself if neccessary. I use (and have always used) west systems epoxy. I personally love its convenience with the ketchup/mustard pumps which give the perfect epoxy/hardener ratio everytime. There are better and more expensive epoxies out there but for my level of precision, west systems has worked great.
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Old Jul 11, 2010, 12:07 PM
Addicted to building...
Freddie B's Avatar
Omaha Nebraska
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Sweet!

Fred
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Old Jul 11, 2010, 12:09 PM
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Tumbler's Avatar
New Jersey
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My epoxy did have pumps too actually.

Brian
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Old Jul 11, 2010, 01:02 PM
It's a spiderweb of knit lines
Souderton Pa. USA
Joined Mar 2002
2,633 Posts
Hi Bret,
Beautiful work!
Do you use a vacuum to degas the gel coat? I always get small bubbles in it if I don’t degas or spray the gel coat.
How does black compare to orange for the mold color, I use orange dye but may try the graphite if black's better.
Mike
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Old Jul 11, 2010, 01:15 PM
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New Jersey
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Bret,

Check it out...I just took my parting board off my hatch mold. Time to it allll over again on the other side!

Brian
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Old Jul 11, 2010, 01:25 PM
DELTAS RULE
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tehachapi, CA
Joined Jan 2006
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looking good guys!
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Old Jul 11, 2010, 02:16 PM
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Omaha Nebraska
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I thought I read thet the graphite powder also helps with making the mold slippery, so the parts come off even easier after layup? That would make it, and the black color way better than dye. Is this true?

Fred
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Old Jul 12, 2010, 02:07 PM
Current project: Electrolyte
pdawg's Avatar
United States, CA, Torrance
Joined Apr 2004
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Quote:
Originally Posted by mcross View Post
Hi Bret,
Beautiful work!
Do you use a vacuum to degas the gel coat? I always get small bubbles in it if I don?t degas or spray the gel coat.
How does black compare to orange for the mold color, I use orange dye but may try the graphite if black's better.
Mike
Mike,

welcome to this thread! You are largely responsible for this project. Before the blowdart I never believed these micro edf's could produce enough performance to satisfy my flying style. Your power system made me a believer! To answer your question, degasing the gel coat is a good technique. I have used it but sometimes the gelcoat looks the same with or without. Its not uncommon to get some microscopic bubbles in the getcoat but by the time the mold has been well waxed they don't effect the molded part. To be honest I do no not strive for exact perfection but do try to make the mold as nice as possible with the techniques I've been taught. This attitude keeps this process fun for me. Taking it too seriously takes the fun away.

I would definitely give the black gel coat a try. It is really effective at revealing airbubbles while producing parts. I have not used other colors but I believe it would be hard to beat a black background.
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Old Jul 12, 2010, 02:10 PM
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New Jersey
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Dude, I left my gelcoat out in the sun for a bit to cure and it bubbled the PVA underneath! Luckily its in an area I will be cutting away from the mold anyway. So ummm....don't do that with black gelcoat!

Brian

Quote:
Originally Posted by pdawg View Post
Mike,

welcome to this thread! You are largely responsible for this project. Before the blowdart I never believed these micro edf's could produce enough performance to satisfy my flying style. Your power system made me a believer! To answer your question, degasing the gel coat is a good technique. I have used it but sometimes the gelcoat looks the same with or without. Its not uncommon to get some microscopic bubbles in the getcoat but by the time the mold has been well waxed they don't effect the moldec part. To be honest I do no not strive for exact perfection but do try to make the mold as nice as possible with the techniques I've been taught. This attitude keeps this process fun for me. Taking it too seriously takes the fun away.
y
I would definitely give the black gel coat a try. It is really effective at revealing airbubbles while producing parts. I have not used other colors but I believe it would be hard to beat a black background.
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Old Jul 12, 2010, 03:50 PM
Current project: Electrolyte
pdawg's Avatar
United States, CA, Torrance
Joined Apr 2004
5,365 Posts
Brian,

Yeah heat can be tricky! One of the reasons for doing 2 thin gel coat layers instead of a single thick one is to limit the heat generated. I've dorked entire molds before by trying to "bake" a part in the mold. The sun is pretty powerful to say the least! Fortunately for you it happen in a non-critical spot. Thats a free lesson .

BTW I'm laying up the otherside of the mold today. The 2nd gel coat layer is setting up as we speak.
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Old Jul 12, 2010, 06:06 PM
Team30 Micro EDF
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Adelaide, Australia
Joined Apr 2004
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Sounds like you are powering through the lay-up process Bret.
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Old Jul 12, 2010, 11:07 PM
Current project: Electrolyte
pdawg's Avatar
United States, CA, Torrance
Joined Apr 2004
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Quote:
Originally Posted by NitroCharged View Post
Sounds like you are powering through the lay-up process Bret.
I haven't been motivated like this on a molded project for some time. Its partly because I've had few opportunities to build over the last 2 years so I ain't taking this time for granted. The thought of flying a micro molded sport jet with great performance also keeps me going!
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Old Jul 12, 2010, 11:19 PM
Addicted to building...
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Omaha Nebraska
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Is that an old Wattage Cub I see, and a glass of Merlot?

Looking good, I feel your excitement too! Very cool thread and I am enjoying it so. Thanks.

Fred
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Old Jul 12, 2010, 11:37 PM
Current project: Electrolyte
pdawg's Avatar
United States, CA, Torrance
Joined Apr 2004
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Quote:
Originally Posted by Freddie B View Post
Is that an old Wattage Cub I see, and a glass of Merlot?

Looking good, I feel your excitement too! Very cool thread and I am enjoying it so. Thanks.

Fred

Nice work Fred! Yep on the cub and the wine. There was some left over from dinner (which i missed because the mold wasn't finished). Afterwards though I felt the wine was appropriate so I took a glass and took a few pics of my labor.

A flying buddy sold his house so some of his projects are temporarily being stored in my shed including his Cub.
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Old Jul 12, 2010, 11:43 PM
Team30 Micro EDF
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Adelaide, Australia
Joined Apr 2004
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Time for me to get my plug organised I think Bret.
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