How to add a base matching model perimeter

I’m new to sketchup and 3D modelling in general. I just bought my first 3D printer and I’m trying to learn the basics.

I chose an .EPS image I converted to STL with an online converter (JPGs result in a very bad conversion) and imported it to Sketchup.

Unfortunately the image the resulting 3D model has some “floating” pieces (for example the center of an “O” or the car silouethe).

I’m trying to add a back face in order to have a base to hold everything, unfortunately the design is not a regular shape, so I was trying to add a big rectangle, extrude it and then remove everything exceding the model perimeter.

I’m attaching the .SKP model for reference.

Thank you in advance, any help will be greatly appreciated.

Rally 2011.skp (2.4 MB)

why not use the outer face as the basis for the base extrusion?

group the sign. copy the outer face out. paste in place. remove inner hole. push pull and group

plz excuse typing…

Would something along these lines work?

It’s really a shame that you don’t have a high res image to start with.

I redrew the outer shape using the native drawing tools because your curves are so rough due to the low res of your starting image. After giving it some thickness, I used Offset to create the inner borders and added that in the center. I copied the text and other outlies down to the surface and use Intersect Faces to intersect them. After that Push/Pull to push down the areas that need to be relieved.

You’ll need to fix the geometry in a few places and either create some small gaps or widen the area so they don’t meet in a single point.