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Molded plastic to replace fiberglass tips?

claycookiemonster

Well Known Member
I see people here fabbing up new lenses for wingtips, etc. How is that being done?

I would like to reproduce the fiberglass tip on the VS with some clear plastic to enclose a beacon. I'm prepared to sacrifice the fiberglass tip I have to make this happen.

I have approached several local plastics places about this, and none of them seem able to do this.

Am I asking the wrong question? The wrong people? It seems possible theoretically but I'm finding the reality challenging. I've never seen 3D molding do anything transparent, so I'm guessing the laying down of layers in that process would make clean and clear items impossible?
 
Clay,

Consider clear plastic windows in that VS tip. That would maintain the structural integrity of the tip. The windows might need to bow out a bit to provide 360 degree coverage.

You flew the T-38; you can probably envision this easily.
 
This shouldn't be a problem. There are vendors that will mold acrylic or PETG lenses of any shape. You supply the plug. So in this case, you could give them your stock fiberglass tip, and they would mold you a clear plastic one using that. PETG is the type of plastic those annoying half-liter water bottles are made of.

I have built a vacuum table, and I'm working on a frame, so I can vacuum-form acrylic tip lenses. We have not been 100% happy with the PETG lenses from a local vendor. Functionally they are perfectly fine, and PETG is easier to work with - not as brittle. But the optics are not perfect and aesthetically they are not great. So - if you can wait a month or two, I may be able to make it for you.
 
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I would like to reproduce the fiberglass tip on the VS with some clear plastic to enclose a beacon.

I have approached several local plastics places about this, and none of them seem able to do this.

Am I asking the wrong question? The wrong people? I'm guessing the laying down of layers in that process would make clean and clear items impossible?
"Plastic places"?
"Wrong people"?
"I'm guessing laying down of layers"?

What?

Did you Google forming Lexan (polycarbonate) or "Plexiglass" (acrylic)? Yes it is possible. Likely not easy and you will have distortion at the leading edge. Vacuum forming into or over a mold in an autoclave (oven) will be involved. You get the material hot enough (but not too hot) it will flow. It's an art and will take trial and error.

It would be easier to make two halves and bond together, accepting obvious seam. If made in two halves you may not need vacuum form for simple "drape" and gravity method.

There is injected molded methods which is beyond average DIY fabrication methods (I think, research it). Google "çlear lens injection molding". Lot's of info and manufacturers happy to make this part.

Small semi industrial equipment may be available from China for a few thousand. I have seen some innovative semi commercial machines come out of China, including vacuum forming machines.

Good Luck
 
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If you do send a tip somewhere to use as a mold, two suggestions -

Use a rib to support the free inner edge. Hot melt can be used to hold it in place or if it's pre-punched, back drill through the tip and cleco it.

Mark on the rib what the extent of the desired part is so they won't try to duplicate the entire tip.

Dave
 
Thanks. You guys make it sound relatively easy, and my non-plastic-engineering mind conceives that it may be easy, but every plastic place I've visited has gotten a blank stare when I asked them about it.

YES, a plastic window on both sides of the VS, or from side to side and over the top is what I'd like. I actually thought simply molding the entire tip in clear something would be easier than having to integrate windows into a tip, but either way would be great. A seam down the centerline would be fine. I intend to block off the forward part anyhow, to keep the beacon from flashing in my vision. It's just a flashing light, not a telescope. Optics need not be perfect.

Yes, I think the VS tip I already have would make the mold. I actually have 3 VS Tips, so I'd be happy to sacrifice one to get the mold made.

The last place I asked wanted $8K just to make a mold, so I think either I'm not asking the right question, or I'm not asking the right people.
 
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