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How to Make Plans?

Namactual

Well-known member
#41
I was using SketchUp 10 or 12 years ago and I'm about to get back in for 3D modeling planes. Seems to me I'll be constructing curves as needed by extruding circles or ellipses, so the extrusions will actually be many-faceted faces, not curves. Should have no trouble unfolding that.
All 3D representations of objects portrayed on a screen are created from faces. Actually triangles at the base level. With CAD, the number of faces that create a curve is typically auto generated depending on the distance from the camera. Sometimes you can dictate the number of faces that represent a curve through the UI or during export.

This issue is finding the optimum number of faces to create the geometric shape you are trying to reproduce either using facets via score cuts, (small number) or pulling the paper off of the back and shaping the foam (large number).
 

Monte.C

Active member
#42
All 3D representations of objects portrayed on a screen are created from faces. Actually triangles at the base level. With CAD, the number of faces that create a curve is typically auto generated depending on the distance from the camera. Sometimes you can dictate the number of faces that represent a curve through the UI or during export.

This issue is finding the optimum number of faces to create the geometric shape you are trying to reproduce either using facets via score cuts, (small number) or pulling the paper off of the back and shaping the foam (large number).
Let's slow down a bit, friend. Cad works with true arcs, the info saved is vector and I don't care how it's plotted or shown on my screen, it still looks like an arc to me.
In SU - if/when I decide to work for example with a tube-shaped fuse - I can draw a circle with 64 sides, then extrude (push/pull) it. I can unwrap that. It's made of rectangles. No issue.
What am I missing?
Oh - you must be talking about 3D work producing more complicated shapes in Cad. Ok that's your game, not mine.
 

Namactual

Well-known member
#43
Let's slow down a bit, friend. Cad works with true arcs, the info saved is vector and I don't care how it's plotted or shown on my screen, it still looks like an arc to me.
In SU - if/when I decide to work for example with a tube-shaped fuse - I can draw a circle with 64 sides, then extrude (push/pull) it. I can unwrap that. No issue.
What am I missing?
You are not missing anything. We are on the same page.

I just mean that even CAD represents a curved surface with faces at the basic level. We are doing the same thing trying to represent a surface with foam. The idea is to find the right number of faces to do what you need without making it too complicated or labor intensive to build. This goes for virtual and physical builds. The larger of number of faces you use, the longer it takes to unwrap.
 

Monte.C

Active member
#44
You are not missing anything. We are on the same page.

I just mean that even CAD represents a curved surface with faces at the basic level. We are doing the same thing trying to represent a surface with foam. The idea is to find the right number of faces to do what you need without making it too complicated or labor intensive to build. This goes for virtual and physical builds. The larger of number of faces you use, the longer it takes to unwrap.
Gotcha. Does it take a long time for the "unwrap engine" to flatten out something in SketchUp? As far as shaping foam, if we want a true conical or cylindrical form then the only time I would score it is when the curve gets too tight. I did this on my A-26 build. For a "faceted" build it isn't made of curves.
If I built a cylindrical or conical shape in SU, I'm sure I could have faces at as much as 3/16" wide and it still works fine as my cut template. And that's not a lot of faces.
 
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Namactual

Well-known member
#46
Gotcha. Does it take a long time for the "unwrap engine" to flatten out something in SketchUp? As far as shaping foam, if we want a true conical or cylindrical form then the only time I would score it is when the curve gets too tight. I did this on my A-26 build. For a "faceted" build it isn't made of curves.
If I built a cylindrical or conical shape in SU, I'm sure I could have faces at as much as 3/16" wide and it still works fine as my cut template. And that's not a lot of faces.
The unwrap tool I used with SU is fairly easy, but you still have to click on every face to flatten them. That can get frustrating if you have a large amount of small faces as you have to click on them in a particular order. But yeah, as long as you are not trying to score cut all of those faces it is not bad.
 

Monte.C

Active member
#47
The unwrap tool I used with SU is fairly easy, but you still have to click on every face to flatten them. That can get frustrating if you have a large amount of small faces as you have to click on them in a particular order. But yeah, as long as you are not trying to score cut all of those faces it is not bad.
Oh - I haven't gotten that far yet. I see. What a bother. Thanks!
 
#48
Inkscape doesn't do 3d modeling I use a series of measurements to get a good baseline for 3 dimensional parts such as the skins for master series planes.
Sorry, hopping on this thread late. @Grifflyer what measurements do you take and how do you convert into curves? Watching your Pe-262 build I saw you had some pretty flawless curves. My attempt to make curved MS-style skins resulted in wrinkles galore.
 

Grifflyer

WWII fanatic
#49
Sorry, hopping on this thread late. @Grifflyer what measurements do you take and how do you convert into curves? Watching your Pe-262 build I saw you had some pretty flawless curves. My attempt to make curved MS-style skins resulted in wrinkles galore.
Unfortunately I haven't quite figured out how to put my process into words, it's surprisingly hard to explain for how simple it is. Although if you're getting a lot of wrinkles in your parts I do know how you could fix it. The biggest thing is to make sure is that the direction you're bending the foam is parallel with the grain of the foam, this makes curving it SO much easier. You also might need to spend a bit more time rounding it against the edge of a table, this will also make assembling it SO much easier.
 
#50
Thanks! I had to redo the nose section of my Kate today, and I successfully implemented your tips. Another thing that helped was having the cut-out pieces of foam from the first attempt, and using it as a template for the second. I think I also saw @The Fopster do something similar in his Cessna build on Instagram, but with paper.

And @Grifflyer, if you ever find a way to put your process on paper, let me know. 😄
 

Monte.C

Active member
#51
There is a paper folding plugin for sketchup floating around out there somewhere. It only works on faces though. Not actual lofts or curves.

@DamoRC used that plugin and sketchup to make a lot of great designs.
Update: I've been putting a lot of time into a design lately and I'm finding SU ideal for this work. Our "curves" are either cylindrical or conical forms. In SU, cylinders are made up of rectangles and conical shapes are made of triangles or 4-sided polygons (depending on if the tip of the cone is included). It's very easy to flatten these. You can make your curves with a lot of little segments. Then just copy your model from one place to another in SU, then on your copy, throw out all the parts that aren't part of the piece you're templating. Then flatten what's left.

Remember, in most places we don't need to model the thickness of the foam; We're just modeling the outside skin.
For places where we do need to use the foam thickness, like where the fuse is notched for the horiz stabilizer, I'm finding the brown FT FB I have is exactly .22". I'll measure the DTFB when I need to. Best way to do this is to stack a bunch of scraps, maybe six of them, measure that, then divide by six.

The below image isn't a model made up of curves, but of facets. The principles are just the same though. This is a fun exercise.

SU.png