scratch building complex curves

The place to discuss all aspects of building models from scratch.

Moderators: Joseph C. Brown, Moderators

Post Reply
grabula
Posts: 10
Joined: Wed Oct 07, 2009 7:01 am

scratch building complex curves

Post by grabula » Mon Feb 15, 2016 10:21 pm

Hey all, I'm getting ready to dive in to building one of these:

http://hgwiki.net/images/0/02/SpittingCobra1.gif

I'm not sure how to go about building the armor. I was thinking of using insulation foam coated in something to make it harder? What are the best materials for coating something like that? Are there other materials more durable? [/img]

User avatar
naoto
Posts: 24404
Joined: Fri Jul 12, 2002 3:22 pm
Location: Temple City, California, USA

Post by naoto » Mon Feb 15, 2016 11:39 pm

Okay, it doesn't directly answer your question, but have you taken a look at papercraft models? Perhaps you can look there for some ideas. With cardmodel and paper model, you start of with flat sheets of material,
Built-up model aeroplanes and boats might also provide some ideas too -- for example, sometimes you would have an internal frame onto which "planking" or "sheeting" is applied to create the external shell, or perhaps a "buck" is created onto which the shell is formed (e.g. using fiberglass layup on larger size, or analogous method using papier mache for smaller sizes.). Sometimes the form is "sacrificed" or destroyed as part of the process (e.g. the form is carved from form -- over which you apply the fiberglass cloth and sheet, and once that is fully cured, you scoop out the form to leave the outer shell only (basically you destroy the form in the process). Sometimes the initial shell you create becomes the form for the final part -- i.e. the initial pattern is made in the shape of the final part, then a "shell" is formed around that -- which then becomes the "negative" from which the final part is created -- a "negative" form allows you to have surface detail as part of the pattern.
Naoto Kimura
木村直人

grabula
Posts: 10
Joined: Wed Oct 07, 2009 7:01 am

Post by grabula » Tue Feb 16, 2016 1:33 am

Naoto, do you have any picture examples? I'm having a hard time following.


User avatar
Kylwell
Moderator
Posts: 28896
Joined: Sun Nov 02, 2003 9:25 pm
Location: Lakewood, CO
Contact:

Post by Kylwell » Tue Feb 16, 2016 2:54 am

You need Captain Foam Man! Also known as Joe Brown here. Insulation foam covered in 2 part epoxy putty, usually Aves now-a-days but it all depends on how hard you want it.

The 2 big things to remember are shaping your foam plug slightly smaller than needed to compensate for the epoxy covering and of course learning to roll your putty to exacting thicknesses. Followed by the black art of laying it evenly on a curved surface.
Abolish Alliteration

User avatar
Joseph C. Brown
Moderator
Posts: 7289
Joined: Thu Jul 11, 2002 6:13 pm
Location: Oak Ridge, TN, USA

Post by Joseph C. Brown » Tue Feb 16, 2016 10:39 am

...I was awake. Really!


Mark Y.'s scratchbuilding article is fairly relevant for this project:
http://www.starshipmodeler.com/tech/my_scratch.htm

And Chris D still has a great article on scratchbuilding:
http://www.christopher-doll.com/scratch ... -farscape/

I really need to consolidate some of my build pics in one location to as an example for this sort of thing...
________
Joe Brown

ajmadison
Posts: 1216
Joined: Mon Jul 15, 2002 10:53 am
Location: windermere, fl
Contact:

Post by ajmadison » Thu Feb 18, 2016 12:22 am

There is also my article:

http://www.starshipmodeler.com/tech/aj_scratch.htm

Besides the coating carved foam method, there are a couple of different ways of solving the complex curve problem:

1. carve a male or female mold (balsa or bass wood) and vac-form it.
2. create a prototype/original carving, and use RTV to create a female mold to produce a resin copy.
3. As in my article, cut bulkheads and profiles and build up your shape. Then stuff epoxy in-between the bulkheads and sand the epoxy down to your shape.
4. IF, your curves are mild enough, you can build up your shape, like the nose on the delta flyer:

http://i88.photobucket.com/albums/k170/ ... n/0006.jpg

Then skin it:

http://i88.photobucket.com/albums/k170/ ... n/0015.jpg

I have also done the brute force method. Laminate sheet styrene to create an approximation of the shape, and used putty to make it smooth. Its labor intensive, but for a small area that defies being skinned, or require bulkheads too small to be cut accurately, it works.

User avatar
naoto
Posts: 24404
Joined: Fri Jul 12, 2002 3:22 pm
Location: Temple City, California, USA

Post by naoto » Thu Feb 18, 2016 4:25 pm

Naoto Kimura
木村直人

grabula
Posts: 10
Joined: Wed Oct 07, 2009 7:01 am

Post by grabula » Wed Mar 02, 2016 6:58 am

Kylwell, I think that's the direction I'm leaning. Now that I have an egg I can use as a mold it seems like the best way to go.

Post Reply

Who is online

Users browsing this forum: No registered users and 2 guests