Correcting the Lunar Models 41" Excelsior

Vidar 710

Well-Known Member
As I get closer to start the build, I've finally began looking deeper into the vacuum forming process. In doing so, I discovered that it's highly likely that the heat from the hot styrene will most likely damage if not destroy my masters due to the materials they are made of. I just ordered a large amount of molding and casting material to copy my masters. The molding material can take up to 450deg F. Plastics require up to 375deg F to successfully soften the plastic to form properly. I'll have the option to pull the plastic down into a mold or cast copies of the masters and use them as bucks.

Before all that, I have to start the corrections to the nacelle struts. This will be the last of the corrections, but there is a list of smaller scratch-builds to accomplish. In addition, Bob Morgan is in the works on the 3D print for the main cargo bay details.

Tracy
 

Inquisitor Peregrinus

Master Member
RPF PREMIUM MEMBER
Have you considered negative vac-forming -- plastic sucked down into a concave buck rather than over a convex? Good way to capture sharp surface detailing and not have to calculate for material thickness.
 

srspicer

Well-Known Member
RPF PREMIUM MEMBER
Have you considered negative vac-forming -- plastic sucked down into a concave buck rather than over a convex? Good way to capture sharp surface detailing and not have to calculate for material thickness.
This is a good idea, that way you are only casting a hard copy over you master and then flipping the casting over to create your vac-form mold. Less expensive than rubber and less steps.
 

Inquisitor Peregrinus

Master Member
RPF PREMIUM MEMBER
Enhh... I'd go with UltraCal or similar -- something with little to no volume loss in casting -- and make an interpositive. Take care with the master, mould it in silicone and fiberglass. Make a copy, and then cast a negative buck off that.

Or, if you have access to a machine shop and 3D pantograph, mill the bucks out of aluminum by tracing the topography of the master with a stylus. With the adjustment settings, you could also scale up or down if you felt like it.
 

ProfKSergeev

Sr Member
Alternatively, you could make fiberglass castings. There would be zero loss of detail and sharpness and the castings would still be hollow. It is a bit messier than vac-forming, however.
 

Starbase101

Sr Member
A concern I'd have with vac-forming a part as large as the LM saucer is the size chamber you'd need and the amount of suction power to pull such a large part. Vac-forming also yields "soft" details - no way of getting crisp lines due to how it inherently works. In my opinion, casting would be more practical and give better results.
 

Vidar 710

Well-Known Member
The only parts I'm wanting to vacuum form are the saucer (top and bottom), the primary hull super structure, the secondary hull, the main body of the nacelles and their forward and aft upper hoods. None of these parts have any skin detail to pull, so I'm not concerned about that. Look back at what I've done to these main parts to simplify them for this purpose. I actually pointed up the edges in anticipation to vacuum forming them.

My options will be to pull down into the molds or make durable castings and use them as bucks. We are talking about very basic shapes here. The skin details will be scribed in or raised plate details will be added during the build.

I have a very large vacuum forming table that will be able to pull half the parts in one sheet.

Tracy
 

Vidar 710

Well-Known Member
Digging around, I found the Collective's vacuum formed Planetary Sensor Dome part at the bottom of my scraps pile. Here it is compared to my completely scratch built version. My master will be molded and cast in resin. However, the dome itself will be cast in clear due to two of the radii's radiate light.

1654229491603.png
 

Iskelderon

Sr Member
Digging around, I found the Collective's vacuum formed Planetary Sensor Dome part at the bottom of my scraps pile. Here it is compared to my completely scratch built version. My master will be molded and cast in resin. However, the dome itself will be cast in clear due to two of the radii's radiate light.

View attachment 1582900
Demonstrates the difference between "good enough for most people" and "full potential".
 

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