Molding the Entex Porsche

Don't want to see this ad? Sign up for anRPF Premium Membershiptoday. Support the community. Stop the ads.


sjanish

Sr Member
RPF PREMIUM MEMBER
This post is going to be multi-part and long, but I want to tell the story, hopefully help others, and hear feedback. If you don’t like the wall of text just skip it and look at the pictures. :p

A couple of months ago I got the opportunity to cut up an Entex Porsche body and make molds for the Slave I parts. It seemed simple enough, drop the parts in RTV, pour resin. Right? Let’s go!

Then I started studying the Entex parts and doing some math. Traditional block molds for the rear fenders would require 12+ pounds of RTV! The front fenders need 10 pounds more! The doors need 4 pounds and the bumper3. At this rate the molds would cost as much as the model! What had I gotten myself into? :wacko

I started to try and figure out a way to use less RTV, focusing on the rear fenders. My first idea was make a custom mold box that would follow the curves of the body instead of a cube shaped box. It turns out that did not help much because the rear wheel well sticks out so far and creates lots of negative space. Then I found a tutorial on the Smooth-On website about cavity pour molds. That would be the solution, but they used Plasti-Paste for the shell. It looked simple enough but looked like a mess. I had never used it and I did not want to learn on this job. Instead, I clayed up the part, put another layer of clay over the whole thing (cavity space) and then vac formed over that with .06 styrene.

DSC05127_zpssrxto269.jpg


DSC05113_zpsk4foo1gy.jpg


DSC05116_zps5qc1fkvh.jpg


After the shell was created I removed the cavity clay.
A pour hole was cut and several vents were drilled and extended with drinking straws. The shell was centered over the rear fender and bolted down through a sheet of scrap ABS that I had laying around. I used some old MoldStar-16 silicone to seal everything up. Lots of people use hot glue for the seal, but that stuff makes a mess. The old RTV worked great and was probably headed for the trash anyway.

The first part poured and curing.

DSC05134_zpsd6tu8z5r.jpg


Clay removed.

DSC05142_zpseouawcaa.jpg


Measuring how much silicone will be need for the second parts.
I measured the first part the same way, but the pictures look like crap. The plastic beads are like what is inside beanie babies.

DSC05145_zpsv3bhag28.jpg


Poured second part. Not pretty, but it works.

DSC05146_zpsvdlopjal.jpg


I had planned on pressure casting these…uh oh.


I have a 2.5 gallon pressure pot. A pressure pot big enough would really bust the budget.
Okay, I will try the part without pressure. It turned out pretty good. There are some bubbles on the top edges, but all of them can be easily filled, some of them will be trimmed off for the Slave part and others will be hidden so deep in the ship body they will never even be seen anyway.

Raw casting.


DSC05345_zpsqtmnusyu.jpg


DSC05346_zpsnenixqmy.jpg


DSC05347_zpsp57llfkb.jpg


Other parts to follow.
 
Last edited by a moderator:

Don't want to see this ad? Sign up for anRPF Premium Membershiptoday. Support the community. Stop the ads.

swgeek

Sr Member
looks pretty good. next time run a bead of hot glue around your mother mold to keep the silicone from leaking.
 

kruleworld

Well-Known Member

Measuring how much silicone will be need for the second parts.
I measured the first part the same way, but the pictures look like crap. The plastic beads are like what is inside beanie babies.
it's funny how it looks like suds (foam)
 
Last edited by a moderator:

Don't want to see this ad? Sign up for anRPF Premium Membershiptoday. Support the community. Stop the ads.

sjanish

Sr Member
RPF PREMIUM MEMBER
Thanks everyone for the kind words.

looks pretty good. next time run a bead of hot glue around your mother mold to keep the silicone from leaking.

Ah, the wall of text reveals the non-reader... ;) That isn't leaking, I used some old RTV to seal the shell. Notice it is a different color than that in the pour hole. It worked great, and unlike hot glue, peeled off easy and clean.

DSC05137_zpss6jwbws3.jpg


it's funny how it looks like suds (foam)

Ha, it does. I am still sweeping up stray pellets.

Nice, that's a great idea! Where did you pour the resin in?

I cut a pour hole and vents on the first one. On the second I used clay to make the pour hole/vents. I can't decide which method I liked better, both have pros/cons.

DSC05289_zpspqfdmuk7.jpg
 
Last edited:

Don't want to see this ad? Sign up for anRPF Premium Membershiptoday. Support the community. Stop the ads.

swgeek

Sr Member
Ah, the wall of text reveals the non-reader... ;)
Ha, it does. I am still sweeping up stray pellets.

Haha busted. I actually didn't realize I hadn't read your text until you said something, oops sorry.
As far as hot glue clean up, if you douse it in alcohol it will pop right off.
Those beads are great, we use them at work all the time, but yeah still find them all over the shop.
 

Don't want to see this ad? Sign up for anRPF Premium Membershiptoday. Support the community. Stop the ads.

sjanish

Sr Member
RPF PREMIUM MEMBER
The doors were done in traditional box molds, nothing too fancy.

DSC05160_zps5ftdikbs.jpg


DSC05166_zpss7uiyq5l.jpg


Here is a pet peeve of mine. I HATE punching vent holes in my molds. In the past I have tried using rubber cement to tack styrene rods to my master parts. It works about 50% of the time. The weight of the flowing rtv will knock over the rods. I know I could use a stronger glue/solvent but in most cases, especially this one, I don’t want to harm the master. This time I tacked down with rubber cement and then mixed up a few grams of rtv. I brushed it on to the rod base for extra support. When the small batch of rtv was reaching the end of its pot life I poured the mold. All my vents stayed in place and the RTV cured together as one. It seems to have worked nicely, but what a pain.

Does anybody have a better way?

DSC05170_zpsgfnr0jde.jpg


DSC05178_zpsxf8pk1yd.jpg


DSC05182_zps2byspjb7.jpg


Here are some castings. I have some minor bubble issues, especially with the strip on the back and the bottom of the door. I tried putting them in the pressure pot, but oddly enough I still had the same problem. So, why bother, the bubbles will be easy to fix.  

DSC05386_zpsxbxgtxvf.jpg


DSC05387_zps1adwum4m.jpg
 

sjanish

Sr Member
RPF PREMIUM MEMBER
Haha busted. I actually didn't realize I hadn't read your text until you said something, oops sorry.
As far as hot glue clean up, if you douse it in alcohol it will pop right off.
Those beads are great, we use them at work all the time, but yeah still find them all over the shop.

Thanks for the tip. I will be trying that.
 

Bigturc

Sr Member
RPF PREMIUM MEMBER
ImageUploadedByTapatalk1423022532.044939.jpg

Very nice thread!! Lots of useful information!!!

My trick, and take that with a grain of salt, is to use clay to fix my straws on the part. Here's a pick of what I mean, in the case of the volvo panel, i still end up with lots of small bubbles in the top edge, but I haven't come up with a better way to do it!

I also thought at first to use a bead of ca glue, but didn't want to ruin my original panel!
 

Don't want to see this ad? Sign up for anRPF Premium Membershiptoday. Support the community. Stop the ads.

Your message may be considered spam for the following reasons:

  1. Your new thread title is very short, and likely is unhelpful.
  2. Your reply is very short and likely does not add anything to the thread.
  3. Your reply is very long and likely does not add anything to the thread.
  4. It is very likely that it does not need any further discussion and thus bumping it serves no purpose.
  5. Your message is mostly quotes or spoilers.
  6. Your reply has occurred very quickly after a previous reply and likely does not add anything to the thread.
  7. This thread is locked.

Don't want to see this ad? Sign up for anRPF Premium Membershiptoday. Support the community. Stop the ads.

Top