Fiberglass mold design and fabrication.

bill_23

Attached is a series of pictures showing a mold designed using Onshape.  The mold model is public.  The second picture is the CNC simulation.  The next picture shows the mold being machined from pink foam from Home Depot.  The last picture shows the finished mold.

andrew_troup

@bill_23

Nice clean loft! I'd be intrigued to know how you set up the loft sections 1 & 2: how did you position the key points, given that you don't appear to have used mirroring? And I presume you created each sketch from scratch - I'm not aware of any way currently to copy sketches.... 

Q2:
Do you have any ideas up your sleeve how you might proceed if you had to try to model the stem using Onshape's current toolset?
(In my limited experience, it's a case of the last 10% of a model taking 90% of the time - perhaps more like 5/95!)

bill_23

There are only three profiles for this model.  The bow, center, and stern.  Lofting takes care of the rest.  Planes are added to locate the drawings of each profile.  This model is a proof of concept.  I am going to build a US 1 Meter RC sailboat.  Rather than a plank on frame or a plug/mold.  I decided to try to machine a mold out of foam and then layup the fiberglass inside the mold.  After the resin has cured, I will cut away most of the foam and sand the rest down to the fiberglass hull.
I put a couple of coats of sanding sealer on the foam today.  I will do the layup tomorrow.

Q2:  To design a stem to be cut out of plywood, I would cut the model in half leaving the profile of the hull.  Then add a sketch profile at the center and draw the part.  When I get to the full size boat, I will have to do this.  I will also have to draw some bulkheads that will be made out of plywood.  They can be drawn the same way or the sectioning tool can be used.

andrew_troup

Sorry, I wasn't clear: I fully realise you only used three sketches, and I understand that's why the loft is so clean; I took the liberty of inspecting your feature list and opening the sketches (in a copy of your public model)

My first question was about the detail of how you created your sketches 1 & 2 symmetrically and accurately, because you don't seem to have used any mirroring, and most of the entity endpoints are unconstrained?

In my second question, I was asking if you had any ideas on how to model the missing stem in Onshape, to produce a realistic-looking model with the current (limited) feature set. (Maybe that's not something you care about, though)
I can think of a way to do it, but I'm not sure it would work out smooth enough, particularly near the knuckle, and my method would take a lot longer than modelling the hull to the current stage.

I guess my question was an attempt to find out whether fairing the bow of a round-bilge sailboat is necessarily as difficult in general-purpose MCAD solid modellers as I have found it to be in the past (unless the designer relinquishes shape control and accepts compromises the modeller can accommodate), or if there's some magic bullet I have not yet stumbled across? 

bill_23

The profile was drawn fully constrained.  Only one side was drawn, then mirrored and the mirror line removed.  After the profile was complete, the constraints were removed to clean up the appearance.  Originally I modeled only half the hull then mirrored it.  However, the CAM program didn't like the .Step model that was produced from the mirrored side.

The front plane goes down the center of the boat.  If a stem were to be added.  The profile of the stem would be drawn on the front plane and then extruded to add or remove the stem profile.  Remove in the case of the mold.

andrew_troup

Thanks for the description re the sketch geometry, I understand how it lost its constraints now. 

re the stem: Hmmm -  wouldn't that result in something a bit like a "C-130 Hercules" nose job?