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Old Oct 21, 2010, 12:40 AM
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Here are a couple of pics of the bottom wing half for my zero, as mentioned its really hard to capture the surface, but i assure you its just like plastic.

Harpye heres a link to aero's old pu molding thread http://www.rcgroups.com/forums/showthread.php?t=383538

Heres my old attempt http://www.rcgroups.com/forums/showp...&postcount=467
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Old Oct 21, 2010, 06:34 AM
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Originally Posted by Heliman420 View Post
Here are a couple of pics of the bottom wing half for my zero, as mentioned its really hard to capture the surface, but i assure you its just like plastic.

Harpye heres a link to aero's old pu molding thread http://www.rcgroups.com/forums/showthread.php?t=383538

Heres my old attempt http://www.rcgroups.com/forums/showp...&postcount=467
Heilman it looks great I have just not achived your results...then agian I really have not spent alot of time useing the cast resin besides my 1/72 wildcat that I still have.

I'm going to use it in my 1/72 builds PU is just to Heavy for that size of an aircraft they fly but like rockets just heavy...
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Old Oct 21, 2010, 06:42 AM
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one of the main reasons is that you are going veryx deep in detail - compared with the Alfa or FSK planes which are consisting of 2 bodyparts, 4 wing shells and 2 to 4 rudder shells ... bit plywood and that is all.....

Aerogel - how about the wing parts ... there is some stange line all over the plug ... did you apply the splitter camo schemme to the panellines section ???

You use PU for forming ??? would be curious to see a detailed process description of the workflow which leads o a part !!!
Strange lines are to help strengthen the wing that the inside of the wing..
Not on this wing build but others I use carbon rods and fuse them into the parts also wires for lights etc…so I don’t have to worry about them later..
I paint the molds then pour the PU in them I will try to do a short video hard to do pic by pic..
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Old Oct 21, 2010, 07:20 AM
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You may want to try the TC-1630... It's not an epoxy... It's a Urethane designed to be cast in thick sections, does not require post cure heat treating, is VERY durable and is designed to used in heat... (It's widely used in the special effects motion picture industry for creating vacuum forming bucks.) I raise the temperature on my bucks for production to 140 degrees just to get them started. They actually operate at higher temps once a few parts are pulled. If you want to try a small amount, I believe Burman Industries sells it in a quart kit... I can't speak highly enough about this material... Over 20 years, I've tried a lot of materials and have stayed with this stuff for vacuum bucks, some are over 10 years old and seem to get better with age. (I will share that this material is a little brittle... not fragile, but if you were to drop it on a concrete floor, it would probably break... If you are using a press to stamp your parts, I might suggest a backing plate (if you are not already using one)...

Best,
Richard
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Old Oct 21, 2010, 11:14 AM
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Richard,

Just Orderd a gallon of the TC-1630, I have plenty of release agents wet and dry what type do you use?
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Old Oct 21, 2010, 12:35 PM
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Heilman it looks great I have just not achived your results...then agian I really have not spent alot of time useing the cast resin besides my 1/72 wildcat that I still have.

I'm going to use it in my 1/72 builds PU is just to Heavy for that size of an aircraft they fly but like rockets just heavy...

Thanks aero, they werent easy to achieve, fiddly and very time consuming, heat, pressure, timing, all have to be perfect, i have thrown out bags of badly molded parts... being a perfectionist sucks... if i see a single microscopic speck or dimple the part is rejected, and since each part takes about half an hour to mold... it can be very time consuming.

I suggest doing this in a clean dust free environment, there is nothing more annoying than getting specks of dirt, hair, and dust that sometimes get molded in to the parts.

As i also mentioned in my thread it is my opinion that its the thicker skin thats giving me these results, the multiple pressings also help....

So its not impossible, just a pain in the a**
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Old Oct 21, 2010, 01:04 PM
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Richard,

Just Orderd a gallon of the TC-1630, I have plenty of release agents wet and dry what type do you use?
The 1630 works against a lot of surfaces... just remember that it is really HARD, so any undercuts, panel lines etc that might lock it into a mold should be poured into a silicone or urethane rubber mold made from your master... Or... you can risk destroying your master pulling it out of a female mold... I usually air blow liquids over a master by applying low pressure from an air hose... it breaks up the surface tension and gets whatever your pouring into all the nooks and crannies... (takes practice and ABSOLUTELY wear face and eye protection!!! too easy to blow it back into your face!...

When pouring 16wo into a mold I do it in one casting, brushing or blowing the surface before quickly pouring the remainder into the mold...

For mold release, I swear by a product called Mann Ease Release 200... Should be available where you purchased the 1630...

Know that when you receive the 1630, there are so many solids in both parts that you will have to stir both up before pouring... Do NOT use a wooden stir stick!!!! Urethane's are sensitive to moisture and may foam up (1630 is not as sensitive) I use a metal stir stick... ABSOLUTELY, do NOT use the same stir stick for both... even if you thoroughly clean it!

Can't think of any other advice other than try it out on something expendable first and in a small batch so you get a sense of pot life, working properties etc...

Feel free to ask any other question you might have... I'm subscribed here and keep very few secrets to myself (maybe at the large volume production level, but for stuff like ths, I have 20 years of mistakes I might be able to save you from!

lol!

Hope this helps!

get a hold of the paper work that comes with the TC-1630 and READ it! lots of good info... stuff like cure time, pot time, and what materials inhibit it from curing etc.... available at the BJB Enterprises website and through Stephenson pattern supply...

BEst,
Richard
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Old Oct 21, 2010, 01:10 PM
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Dont forget using PVA (sprayed lightly with an airbrush as a great all round mold release (actually a parting film)... is always a great standby, but not needed if using silicone...

another tick I use for FINE DETAIL and hard to reach crevices... I spray a light coat of mold release then LIGHTLY brush in baby powder or just shake the mold around and not risk touching the surface... the use an air gun to blow the powder out... (make sure no large white clumps are stuck in the mold somewhere... just a super fine powder coating... The microscopic graininess of the powder breaks up the surface tension and helps any pourable resin/epoxy coat the surface helping to eliminate pin holes/surface bubbles...

another method is to use a pressure tank... (I have several... a small one made from a pressurized paint can used for commercial spraying... If you can get the casting into the tank before it begins to thicken... 40 to 50 PSI, collapses all airbubbles garaunteeing a PERFECT casting...

ok... back to work here.

Richard
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Old Oct 21, 2010, 04:39 PM
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Thanks Richard.
I have a pressure tank and I use the Manns Ease Release 200 both for resin casting and for some of my silicones that really require it to be bubble free..

Undercuts are going to be my problem I'm so use to silcone guess it going to be on the model I choose to use for this process.
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Old Oct 21, 2010, 06:11 PM
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Sounds like you are already familiar with the professional stuff... Not sure about pressing, but I am able to pull (vacuum forming), "some" undercuts and definitely horizontal panel lines and rivets... I'm thinking that the foam sheet you're pressing has some "give" to it...

I set up a pressure "blow-off" valve on my vacuum former... on the really tight stuff, I can pressurize the area that once had a vacuum and blow the plastic off the molds (the molds are held down to the table with screws...)... Other times for one-offs, I can apply a nozzle to the slit between the plastic and the mold to pressurize the interior and achieve the same results... Also molding the part in several pieces or...

Ok, here's something I have done on occasion: It's called a slider or multi-part mold... If you have a part with an undercut, you could drill holes in the female section and apply vacuum and/or make a two part mold or a three part press where you pull out the center and then the rest comes out... just ideas in case you can see where any of these might be applicable.. I am not versed in the methods you guys are using to "press" the parts between male and female molds... understand the theory completely, just no experience.

Watching like everyone else and just offering what I know "just in case" it might have any applications...

Looking forward to keeping posted!

Thanks for sharing!

Richard
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Old Oct 22, 2010, 01:59 AM
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Press molding and under cuts just dont mix, what ive been thinking about is making a silicone male and a epoxy female, this would allow for small undercuts 1mm and less.

Im currently playing around with the cowling for my zero, ive decided to mold it whole, but it has a .5mm undercut if you measure the sides, the back is .5 smaller than the middle, but only on the sides, ive went ahead and added some .3 wax around the thickest part on the female mold... im hopping the expansion of the foam will fill in the void.

If not i will go with my original idea and just mold it in two halves.
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Old Oct 22, 2010, 08:18 AM
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Thicker foam expands about 10 percent due to applied heat, so small undercuts are possible but with deficite on the quality of detail
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Old Nov 06, 2010, 03:16 AM
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nieuport 16

This is my work on a nieuport 16.
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Old Nov 06, 2010, 03:23 AM
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Cool! more info?
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Old Nov 15, 2010, 10:58 AM
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United States, CA, Felton
Joined Jan 2005
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Hello, I am just learning about the molding process and different molding techniques. Here I have found a beautiful peregrine falcon with some details on this Spanish website. A babelfish translation helped a little, but not too much.

I was wondering if anyone could help me by giving a basic rundown on the techniques used here: what material might have been used to construct the mold, and then what was used to make the actual fuselage, etc.

Or if there is a simpler method, what method would you suggest for a beginner? any links to instructional material would help. Thanks!

http://www.miliamperios.com/foro/ala...o-t126778.html

vid:

halcon peregrino electrico 1 (0 min 37 sec)
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