Kevin's roundel attempt

[galacticprobe]

However, those pesky air bubbles continue to haunt me. No matter how hard I try to get rid of them, they persist.

The second try looks great, Kev; although that first try also looks pretty great as well. As for getting rid of the air bubbles... I don't know if I've mentioned trying this method before, but have you tried using one of those semi-stiff disposable paint brushes (the kind that cost less than a dollar) to "poke" around the cloth and resin to work the bubbles out? I've seen professionals doing that in several modelling magazines - some working on those filming miniatures for the Trek (TNG era et al) franchise. Once, many years ago, either the Discovery Channel or The Learning Channel (I can't remember which one aired it) had a series called 'Movie Magic' where they took you behind the scenes to show you how they made, well, their movie magic.

Several of the episodes showed the model builders actually poking at the fiberglas cloth and resin with those brushes, occasionally dipping the brush into some resin if needed, as they explained they were working bubbles out (and smoothing the fiberglas as well). The models ranged from some Trek starships to naval ships to miscellaneous spaceships. If it works for professionals, it's at least worth giving it a try on your roundel before you go to the gelcoat (which I'm guessing is more expensive than the fiberglas).

I hope some of this is helpful.

Dino.

[Theta Sigma]

Those disposable brushes are actually what I am using to wet out the fiberglass to begin with, in a dabbing motion.  I poke until my arms falls off, but the air bubbles just want to move around.  The surface veil is woven so finely, that once it saturates with resin, the air does not want to come out.  I also have a grooved roller which is supposed to help, but it only really works well on the flat surfaces.

I see there is a "bristle roller" available which might work better, but that's going to be hard to clean.

https://www.fibreglast.com/product/Bristle_Roller_01105_A/Supplies_Tools_Rollers_Squeegees


And yes, gelcoat is expensive.

[karsthotep]

They look great Kev, I again don't think the quest for the ultimate perfect roundel is required unless you are in for the fun of it.  they are all bubbly, I am looking at mine right now and there are bubbles through the whole thing and its a production one.  99.9% sure that every single one has bubbles that was ever produced.   Your work is freaking awesome if you are just on your bubble quest for fun then have at it I think they all look great as is.   

[Theta Sigma]

They look great Kev, I again don't think the quest for the ultimate perfect roundel is required unless you are in for the fun of it.  they are all bubbly, I am looking at mine right now and there are bubbles through the whole thing and its a production one.  99.9% sure that every single one has bubbles that was ever produced.   Your work is freaking awesome if you are just on your bubble quest for fun then have at it I think they all look great as is. 

If the bubbles would stay sub-surface, I might be able to overlook them.  When they cause surface voids/defects, I have to draw the line.

[karsthotep]

ah I see what you are getting at yes,  the bubbles are all internal, not surface on mine

[mverta]

Gentlemen - just checking to see if there was anything needed on this front.  My own build is going to be fiberglass, overseen by a true expert, and we're going to have these roundels on the inside.  Is everything covered in terms of having a plug/mold/source, etc.?  It looks like things are well in hand, but if not, happy to help.  My plan at this point is having a master casting pattern made from my CAD files.

_Mike

[Theta Sigma]

Any tips you pick up from your expert and share would be greatly appreciated.  If you don't mind my asking, what is the source of your CAD files and what are they based from?  Did you make them yourself?

May of us have looked into have a master produced by 3D printing, CNC routing, etc, but it was cost prohibitive due to the size of the plug.

I have also come to the unfortunate conclusion that the center of these roundels are not flat, and were never supposed to be.  Initially I thought it could be from warping, but the two I have cast are not warping in the slightest.  This further reinforces the idea that the original object was likely a slightly convex mirror with a decorative frame.

Now I just need to figure out the best way to produce a convex center via my method of plug making.  I have yet to find a mirror available today that isn't excessively convex.

[mverta]

Tony sent me some drawings for the profile. I sort of assumed they're accurate but I hadn't really gone down the road of checking yet.

As for the center being flat, I I work in VFX, and I've never seen a photo of a real one that didn't exactly exhibit the precise characteristics of a convex center. I never thought it was flat. At least it's never been photographed in a way which behaves as though it were flat.  The big giant caveat there is that I think I've only seen two photos of a real one.

In fact if I have a profile that everybody believes is accurate I can probably derive the actual shape of the convex Center pretty easily.

You know, unless it's flat

[tony farrell]

I wonder if these photos will help in deciding whether the roundels originally had flat centres or not (all photos from The Masque of Mandragora - the story which marked their first appearance):





T

[mverta]

Those are flat, 100%


This, however, is convex, 100%:




Now, you're the expert, but all the translucent fiberglass roundels I've seen have that convex bowing in the center, as clearly evident in the light play as the flatness of your posted examples is.  I'm sure there's a whole thread on this I've missed which you can link me to to avoid having to re-explain it all


EDIT: At least all the roundels in the console room and on the doors and walls in Logopolis are flat in the center - the moving cameras and reflections make it clear, so all the photos of roundels I've seen must come from some other source or exhibit the same warping in the center - again, you probably know.

_Mike

[Theta Sigma]

Well phooey.  Just when you convince yourself of one thing, new photographic evidence surfaces that makes you doubt your conclusions.  I have to agree, the ones in the black and white photos are definitely 100% flat.

I guess I will stick with the flat centers.  It certainly simplfies things.  Perhaps the convex warping came from some type of resin cure acceleration, like a heat source.

[mverta]

Don't feel bad.  Like most things, this is a moving target.  There are giant, inexplicable things which happen even day-to-day on this show - like the fact that one day the wall above the signbox was level and the next day/shot/hour/take it was crushed down, and stayed like that.  



Fiberglass shouldn't even do that - it typically doesn't melt below 2000 degrees, and there's no pressure on it.  

Just roll with it.

_Mike

P.S. Love that color consistency, amirite?

[Theta Sigma]

So I just had an idea.  I have a relatively thin flexible silicone mold with a rigid plaster mother mold support.  If I can find something to lay in the center of my flat plug to deflect the center of the silicone into a concave shape when placed back on the plug,  then I make a new plaster mother mold.  The end result will hopefully be that I can make roundels with flat centers or convex centers by simply changing out the mother mold support. 

Warm weather is coming and I will be back at this again soon!