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making a mold

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Old 06-30-2013, 08:11 AM
  #26
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Default RE: making a mold


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ORIGINAL: sensei

One of the things I learned over 30 years ago that causes premature epoxy tooling life is allowing razor knife cutting on the mold surfaces when utilizing pre-pregs or wet layup for that matter.

Bob
Amen brother Bob...preach the word! LOL
That is a statement every fabricator should put on his wall! It will destroy the edges of a mold quick. I was taught that method and changed to making a template so I can cut the glass to fit the mold without post trimming.

Tim
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Old 06-30-2013, 01:23 PM
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Default RE: making a mold

I've been using a VERY sharp wood chisel to do my post trimming. a 3/4" or 1" wide chisel works great and if your very careful, you can post trim without damaging the mold edges. Again, the key word is Careful!
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Old 06-30-2013, 07:08 PM
  #28
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I just pulled a 104 out that was layed up just short of the parting board trim line. My seam tape/cabosil covers the seam section with out issue. I will probably continue this way since it saves the babysitting of the lay up till trim time. Also avoids the entire trim sequence.

So many options in the lay up.

Steve
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Old 06-30-2013, 09:34 PM
  #29
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Default RE: making a mold

That's what I do too Steve. That way if I have to stop for the day I can just finish the half I'm working on and throw it in the vacuum back with some peelply, release film, and bleeder cloth, then set the vacuum to the amount I want and walk away.

I made templates to cut out the cloth and it gets pushed up to the edge. I use a marker when I draw around the template on the glass. This way I have a colored line that helps me see when it's pushed to the edge.

Seaming the molds (install seam tape before joining halves and add epoxy/silica mix with a syringe): I finish the two halves by wetting out seam tape with epoxy on some mylar or Monokote or whatever and then crease it and add it to one half of the mold. Next I mix up epoxy with a silica thickening agent and it gets applied with a syringe along the whole edge, even where the tape is to help fill in the seam. Then the areas I can't get to with seam tape when the halves are joined also gets a bead of silica epoxy so they will bond without tape (usually the tail and vertical stab). Now that the first side has tape that is folded over I apply the other half of the mold and all I have to do is press down the tape with my hand as far as I can reach and then I use whatever I can to press the rest down. Sometimes I will put a very thin layer of epoxy to the 2nd mold half to help the tape bond.

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Old 07-01-2013, 06:51 AM
  #30
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Default RE: making a mold

Tim

Pretty close to what I did on my last 104 fuse. But I never liked the tape on 1/2 mold.

Since the 104 mold has a pretty good sized opening in the tail section, I close the mold loosely,(.25 mm gap maybe) then I put a wet tape/bead of cabosil on a stick and place it in the fuse. Press the tape down with an acid brush on a stick, then fully clamp the mold. A lighter tape I use in the Vstab. The cabosil mix we put in a paper mini grout bag made from the pages of AMA magazines to apply.

Vac bag. I have never done since in my applications is not worth the extra materials. Not even in my composite wings.



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Old 07-01-2013, 12:30 PM
  #31
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Lots of info in here. Thanks guys. If I was going to pay someone I would get a mold I could use for a long time, not that I plan on crashing but can pull it out and make one anytime. not sure which way I will go yet. I did see some already has a mold out there as there is a Fuselage and cowls on sale in RCU. I could just buy that fus and cut it up and make formers then load them into a cad file and make a wood fuselage.

I just dont want to built this one and not be able to build another one. who knows the plane may not fly well anyway..
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Old 07-02-2013, 11:17 AM
  #32
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Don't cut it. Use a contour gauge for the shapes.

I would still make a mold.

Steve
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Old 07-02-2013, 01:03 PM
  #33
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Default RE: making a mold

Hang on to those old molds, you never know when you might need them. Here are some pictures I took today of some some old 35% Extra 300S molds that I developed and then manufactured 10 Full kits with all pre-preg and Nomex honeycomb fuselages, foam core pre sheeted wings, and tail feathers, landing gears, and canopies, I did this around 12 years ago or so. There is also a couple pics of one of the finished airplanes, and a shot of the 70% Staudacher wings and molds halves as well.

Bob
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Old 07-23-2013, 02:48 PM
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WRONG!!! HE DID NOT SAY HE WAS GOING TO SELL THEM.. IT IS HIS TO DO WHAT HE WANTS .. BEEN THERE [X(]
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Old 07-23-2013, 02:50 PM
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+1
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