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Old Jul 19, 2010, 05:21 PM
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Germany, Berlin
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nose cone links...

if you havent seen 'em, I posted a thread a couple yrs ago about different techniques, and got a bunch of different answers. I have yet to use the techniques yet, but I have another plug waiting to try it on if this one works out.

I was going to do the three-part mold, making the sub-nose cone out of water putty, as discussed in that thread. The thread's a mind-bender, but if you look at it a couple times it becomes clearer.

I like the shape of your pod/tail.

Ben
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Old Jul 19, 2010, 06:07 PM
Stirring the pot
johannlochner's Avatar
Port Elizabeth South Africa
Joined Jun 2008
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The gel coat's on and laid up with strips of 50g glass.
The glass was applied after the gel coat "gelled"
A couple more layers of 86g cloth...
And we'll see how she pops off!
No PVA....
With all my problems lately having stick-ups with paint in the mould. I'm almost ready to try the PVA (never done so before)
But...
The had none in stock!
Sooo...
Back to Mirror Glaze and elbow grease!
(It does give you a great mould finish... If you get it right!)

Thanks for the info Ben. I'll check it out tomorrow!
Good luck with your casting!
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Old Jul 20, 2010, 03:51 AM
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Port Elizabeth South Africa
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Quote:
Originally Posted by skinnydoc View Post
if you havent seen 'em, I posted a thread a couple yrs ago about different techniques, and got a bunch of different answers. I have yet to use the techniques yet, but I have another plug waiting to try it on if this one works out.

I was going to do the three-part mold, making the sub-nose cone out of water putty, as discussed in that thread. The thread's a mind-bender, but if you look at it a couple times it becomes clearer.

I like the shape of your pod/tail.

Ben
Thanks for this Ben!
A lot of threads going in all directions.
Took a bit of reading...
I think I may stick to a canopy for now as it is the simplest.
I'll give the nose cone a bash if the plug comes out intact..
I would like to try!

For now....
"Theraven"will have one big eye!
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Old Jul 20, 2010, 03:27 PM
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Port Elizabeth South Africa
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We have a canopy mould!
It's tiny....
This must be one of the smallest canopies I've ever had or built!
It came out perfectly...
No stick-ups without PVA.
And the finish is all smooth and shiny!

Should I take the risk with the plug????
I would like to have the mould the same finish...
I'll think about it as I cut out the splitter board
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Old Jul 20, 2010, 03:35 PM
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very nice J
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Old Jul 20, 2010, 04:46 PM
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next steps...

nice little mold...

I want to see what you do next. the next steps with canopies have always confused me (not having done it yet), e.g. do you make a canopy cutout now with a stepoff like Adam (Wyo) does? or do you scribe a line, mold it in, then cut the resulting mold, THEN make a canopy step with a piece of a canopy (like Samotage did?).



Ben
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Old Jul 21, 2010, 12:35 AM
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progress update w pics

ok, so some progress, and I have my first mold half done. I'm very pleased with the finish, the best I've had yet. I really like the Frekote system, so simple and you can get back the hard work put into the plug with the finish on the mold. I'm happy to report the Tap Plastics epoxy (a local store, relatively cheap epoxy) is quite compatible with the Frekote system.

You can see my little practice Silly Putty mold in the pics. It was a good test run for me. Note the lentil bean backing... very high tech.

To summarize following the pics below, I glued my little nosecone plug onto a slice of my wing, and filleted with Split Second filler. That SS stuff is amazing, it sets up in 3min, and is very light and sands easily. I heard about it on RCG from some builder. Much easier to work with than Bondo.

I then went back to the Duratec 2 part primer, this time spraying with a larger nozzle HVLP gun with better results. I still had to do some sanding, but much less. I started with 320 grit wet/dry, and worked up to 2500, and finished with the meguiars polish.

I built the splitter and splooged it. The release of the frekote on the plug from the splooge was amazing, just popped out. Application is a breeze too. (just 3 wipes with Frekote FMS sealer, then three wipes with the Frekote NC, with just a little drying time.) I put microballoons and cabosil in my splooge. Unfortunately the Cabosil made bubbles in the finish of the splooge on sanding, so the finish of the flange around my plug is pretty crappy. Not a big deal for molding, but lost some style points.

I built the dam of coroplast lined with packing tape, pretty simple and flexible when you cut some ribs. I Frekoted the packing tape for good measure.

I used Adam's epoxy surface coat recipe: epoxy, WS 404 filler, and graphite, following his guidelines. I tried the torch thing, and cooked my first test. I ended up doing a few passes with a heat gun on low, as getting a torch into my narrow dam was too dicey. I didnt see many bubbles bursting. I used Tap Plastics Marine Grade epoxy with fast hardener, and was able to put on 3 coats of surface coat, with only 40min of curing time in between to gel the coats.

I then did 1 bias layer of 2oz cloth (?66 in metric), then 1 bias layer 3oz, then gelled that layer. Then I built up the mold with random pieces of 3oz / 6oz / 8oz cloth in graduated layers, maybe about 6-7 layers total. Then gelled some more. Finally I made a slurry of lentils with microballoons and chopped glass, and filled in the dam to make a backing. I did the whole layup last night, it only took about 4 hrs, including gel time.

I let it cure at 70deg overnight, then put it in the hotbox all day today at 95deg or so. 18 hrs of cure time total, and it was solid as a rock, so I pulled off the dam on coming home from work.

I did the forbidden thing and pulled out the plug because I'm planning to try and fix up that messed up splooge impression a little. It slips back in tighter than a glove though.

In the next couple days I'll do the second half of the mold.

Its nice to have something come out so well. Try Frekote if you can, its the bomb compared to spraying PVA and stressing about dust, etc. Its so easy I can just play around and try out different molding techniques without the lengthy waxing/PVA rigamarole.

Sorry for the long post, just wanted to give back to RCG.

Oh, and yeah I know, its a pretty phallic pod ... niiiice ! It wasnt planned that way, but my wife likes to give me crap about it.

Ben
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Old Jul 21, 2010, 12:58 AM
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Ben, nice work!

A couple of thoughts.

1) Adding glass to the back the of the lentil surprise will give even more stability to the mold. Ideally, the glass backing should be the same weight as the face lay-up. If you decide to add it, don't force cure with heat too early (3 or 4 days). If the backing cures too quickly it will shrink more than the face and could lightly warp it.

2) The bubbles in the parting sploog is pretty common. I've had that happen before too. It shouldn't present a problem. I polish my parting board and seal with micro-mesh pads on a random orbit sander. This brings a gloss to the sploog seal. Typically the first mold half will have raised bumps (positives from the female bubble divots in the parting board). These can be shaved off with a razor blade even with the plug still in the mold half. Its best to slide the razor blade toward the plug.

3) I'm sure that you know this, but make sure that your seal and release treat the entire 1st mold half before putting the plug back in. The surface coat from the second half can leak between the plug and the first mold half.

Again, nice work!

Adam
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Old Jul 21, 2010, 01:05 AM
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thx Adam...

Dooode... I wouldnt have thought of (3)! A good one.

(2) above: I'll have to find out what a micro mesh pad is, but I assume you do this sanding/polishing WITHOUT the plug in, next to the rapidly vibrating piece of machinery?? I would also worry about chipping an edge with such intense treatment, no?

Lastly: I found a few hazes and mild defects in my mold surface, what do you suggest next to fix up that surface? The Maguiars polishing stuff? Can I use a buffing wheel, e.g. in a hand drill, to help with the mold polishing process? Anything you can pass on (in brief) about finishing up the mold surface would be appreciated. I havent seen this documented anywhere before. (I'm entering total newb territory here)

thanks again...

Ben
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Old Jul 21, 2010, 01:20 AM
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Quote:
Originally Posted by skinnydoc View Post
(2) above: I'll have to find out what a micro mesh pad is, but I assume you do this sanding/polishing WITHOUT the plug in, next to the rapidly vibrating piece of machinery?? I would also worry about chipping an edge with such intense treatment, no?
Micro Mesh I wouldn't try the random orbit trick on the mold. I use it on the parting board & seal before making the first mold half

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Originally Posted by skinnydoc View Post
Lastly: I found a few hazes and mild defects in my mold surface, what do you suggest next to fix up that surface? The Maguiars polishing stuff? Can I use a buffing wheel, e.g. in a hand drill, to help with the mold polishing process? Anything you can pass on (in brief) about finishing up the mold surface would be appreciated. I havent seen this documented anywhere before. (I'm entering total newb territory here)
2000 grit paper with soap and water, then 3M 3000 grit Trizact pad with water, then polishing compound. Gluing a piece of synthetic sponge for polishing compounds to a felt dremel wheel works well for polishing small tight areas. Whatever you do, don't try just the Dremel felt pads for polishing.

Lastly, how are you going to index the mold?
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Old Jul 21, 2010, 01:32 AM
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gotcha...

Ok, I get it. I'll try that next time with the splitter.

Yow, the Trizact stuff is pricey, see Amazon for example at $98! Do you put that on your velcro sanding pads? Any cheaper sources?

For Indices: I think I'm going to just do the drill bit thing maybe? make a depression with a 3/8" bit or something, then hit it with Frekote. I have a drill press now, but I'd still be a bit stressed about going all the way thru my surface coat.

I also had seen how you tell folks to sand down the resultant raised index to allow better wet seaming and epoxy pooling (?).

Buffing: Do you really buff your bigger molds with a dremel? or is that only for corners? I would think that the tiny dremel would be maddening on a larger mold (this isnt large), and I wouldnt think that the sponge soft enough. But I dont know anything about buffing... I assume its for the polish removal step, not the polish application step?

Thanks as always for your time Adam. (Jeez, you're an hr ahead of me, shouldnt you be sleeping??)

Ben
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Old Jul 21, 2010, 01:47 AM
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Quote:
Originally Posted by skinnydoc View Post
Yow, the Trizact stuff is pricey, see Amazon for example at $98! Do you put that on your velcro sanding pads? Any cheaper sources?
Many parts stores will sell you a single 6". I get them at car quest. A sweet option is getting a 3M headlight polishing kit. They sell them for around $15. In it you get 3" attachment for your drill, a 3" trizact pad, and a foam polishing pad for compounding/polishing. Just wash the pad between grades of polishes.

Quote:
Originally Posted by skinnydoc View Post
For Indices: I think I'm going to just do the drill bit thing maybe? make a depression with a 3/8" bit or something, then hit it with Frekote. I have a drill press now, but I'd still be a bit stressed about going all the way thru my surface coat.
Going through the surface coat isn't a big deal. I've done it plenty. If you want a nice glossy key, you can cut the female into the first mold half then dab it with some fast curing resin so it just lightly "pools" in the cut. Once cured, you should have a nice glossy surface in the female key. If you're careful you can do this without getting any epoxy on the flange of the new mold half. I use a tooth pick and a Q-tip.

Quote:
Originally Posted by skinnydoc View Post
I also had seen how you tell folks to sand down the resultant raised index to allow better wet seaming and epoxy pooling (?).
Yep. I sand down the males so they are about 3/32" tall. This is also really helpful when sliding the molds halves together when wet-seaming. A tall key makes this much more difficult.

Quote:
Originally Posted by skinnydoc View Post
Buffing: Do you really buff your bigger molds with a dremel? or is that only for corners? I would think that the tiny dremel would be maddening on a larger mold (this isnt large), and I wouldnt think that the sponge soft enough. But I dont know anything about buffing... I assume its for the polish removal step, not the polish application step?
First off, I rarely ever polish my molds (except with a little super-fin polish with a new mold...and I do it by hand). It's much easier to polish a master than a mold. A 3" or 6" pad works well if you have to polish a repair. But even a 3" pad is difficult to navigate in a fuse mold. Here some little 1" pads on a dremel (variable speed and as slow as possible) are king.
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Old Jul 21, 2010, 04:24 AM
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Port Elizabeth South Africa
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Great stuff Ben!
I don't know what my issue is with PVA...
Other than what has been mentioned,
And my spraying abilities!

I'm going to try a casting to see....
Frecote sounds like a good option!
Unfortunately they only sell it here in 5l quantities.

Great input Adam...
It really helps a lot!
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Old Jul 21, 2010, 04:21 PM
Stirring the pot
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Port Elizabeth South Africa
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Hey Ben!
What a mammoth post...
I've had to read it all slowly to take it in!
Between you and Alex (Jart build), you are making me nervous with the application of the PVA.
I'll give it a bash on a fuz casting I need to do for Sean.
It's into a gel coat mould, so should be OK.
As I can't get hold of some Frekote... sooon,
I'll polish up with Mirror glaze and dive right in!

Not much done tonight, or tomorrow...
But at least I'm getting fit!

Keep it up, and well done!
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Old Jul 21, 2010, 09:23 PM
working to the closest cm
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brisbane australia
Joined Nov 2002
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dremel sanding adapter

Quote:
Originally Posted by wyowindworks View Post
.. in a fuse mold. Here some little 1" pads on a dremel (variable speed and as slow as possible) are king.
Hi Adam do you have any posts/pics describing these little dremel adapted polishing pads?

cheers jeff
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