Help with modeling curved, double-edge blade

[crescent.wire]

Hey everyone,

First-time poster and relative newbie to Fusion 360 here. I'm trying to model a small sword (80 mm total length) for one of my son's action figures. I plan to 3D print once it's done. I have a drawing I'm using for reference, and have most of the model complete. But, there's one small detail I cannot seem to get right.

Notice the flat "face" of the blade, facing upwards. I want to add a very slight raised edge down the center of that face, like so:

There might be a better way of doing this, but I've been just sketching a right triangle (I'm only working on half since it's mirrored at the end) and extruding along the length of the face, joining it to the same blade body. The problem is how this line meets the end of the blade where the curves begin. If I extrude that right triangle down to where the curve starts, I end up with this:

This gives me a flat edge (looking down the blade from the opposite perspective) on the end, which obviously looks horrible. What I'd love is a way to loft the entire right triangle profile down the length of the blade and to a point at the tip of the curved part of the face, like this:

So, I thought I could loft from the end of that existing extrusion, through a new isosceles triangle (sketched on an offset plane at an angle) and ending in a point:

But whenever I try that, Fusion complains about the guide rail I'm using (the face of the blade itself), stating "the rails do not intersect all profiles."

I tried creating a dedicated sketch line for the guide rail itself, projecting the outside edge of the blade face onto a new offset construction plane, but it won't even let me select that, stating "the selected rail does not touch all of the profiles."

I'm at a loss of what to do, and I've sunk probably 4 hours into this trying to find a solution. This would be so easy to do in a traditional surface modeling tool, but I'm really trying to commit to using Fusion's solid modeling tools. I'm honestly ready to completely trash this model and start over, but I'm afraid I'd end up in the same quandary as I am now. Fusion is an incredible tool, and I know there's a way to do this--I just don't know what it is.

What am I missing here to make this work? Thanks so much for your help in advance!

[TrippyLighting]

Looking nice so far!

Can you share the model ?

Please export it as as a .f3d file and attach it to a post.

[crescent.wire]

Thank you! Yes, certainly. File attached.

Thanks a ton!

[TrippyLighting]

Lets take a step back and start with proper sketching and modeling technique for the things you already have modeled.

1. A symmetric "thing" should be modeled with the symmetry axis aligned with the origin/sketch-origin.

2. Then at least straight lines and arcs should be fully dimensioned and constrained.

3. You can also use fewer spline point and instead adjust the shape with the tangent handles. I left that for now.

[crescent.wire]

Understood, and thank you. This was my son's drawing (on the canvas), so things are very freehand 🙂

I also understand that I should've aligned the canvas's "centerline" (down the middle of the blade) with the project's native origin. I suppose I could move that original blade sketch and so on, but I don't know what effect that will have on everything else. Still, noted for the future. Thank you.

[TrippyLighting]

Does this resemble what you are looing for ?

[crescent.wire]

Yes, very close I think! How did you do it? And do you mind sharing the file so I can see the timeline steps, please?

[TrippyLighting · Accepted solution]

The model is attached.

The screencast will take an hour or so to complete on YouTube:

https://youtu.be/tqCEHySrge0

[crescent.wire]

Wow, this is really amazing. THANK YOU! I had no idea about the blend curve/spline tool, or the necessity to use surface modeling for that inner edge. Looking at the steps altogether makes complete sense. Part (if not most) of being good with Fusion 360 is creative problem-solving--and these steps give me tons of ideas for the future.

Thank you again for your help! I greatly appreciate it 🙏

[Drewpan]

Hi,

I am really glad you said this was for your son's Action Figures. After looking at the design and imagining

how nasty a wound it would create, visions of the following War Crimes trial came to mind. 😯

I only mention this as I recently read an article that talked about modifying the Geneva and Hague treaties

to take into account weapons and tactics used in various computer and war games. The theory being that it

might be "just a game" but it apparently encourages actions in the games to be "normal".

I don't want to start an argument about the ethics of games or anything. I play games for fun. Some experts,

however, think that even games should be regulated by these Treaties. I hope your son enjoys his Action

Figures the same way most other games are intended - for fun.

It is a Nasty looking weapon. I do see the Coolness factor in the design.

Cheers

Andrew