Loft problem

[leescienseen]

Hello! I am trying to design an archtop guitar based on a Gibson ES-335. And I know that in Fusion 360 you can make a similar body shape with a carved top. But I do not have enough knowledge in Fusion to do it. I have to ask you for help...

- The only tutorial of its kind on the ES-335 shape in Fusion is on the YouTube channel @TwoCherrisInstrument. And if I followed his example, I probably would not have to write on the forum.

But I really like another method of building a body with a carved top. Using cross ribs and the Loft function. This method seems more convenient for making changes. The most obvious example: suggested by the author of the channel @AustinShaner in this video: https://youtu.be/9duiqt5yuic?si=-Za9MrM2RgtOn12F

But, having tried to repeat Austin's actions in relation to the ES-355 form, it turned out that the Loft function is not so friendly to this form. For some unknown reason, there is an intersection in the area of ​​the horns.

On the surface of the Loft itself, some auxiliary lines appear that cling to the wrong place. Other people who design similar forms in a similar way do not have this happen.

Tell me. What am I doing wrong??

Is it possible to fix this error without making significant changes to the form itself??

P.S.: Instead of recording a video, I would like to provide an f3d file with the project. If someone agrees to spend their time and look at it.

[davebYYPCU]

The video worked because he knows that Lofting sharp corners like this will always be problematic.

The horn shape is going to fold over itself.  Will need some separate Lofts.

Right at the end of the video, he spoke about a flat centre section face, 

Obviously, you will have to incorporate the corner with that possible face.

No file can't see the rails.   If I don't tell you, someone else will, there are far too many spline points in the profiles and rails - to get reasonable reaults.  

Might help...

[Drewpan]

Hi,

When posting to the forum it is always a good idea to give us the file to look at and to provide an explanation and a

screenshot. With the file we can often troubleshoot the original and return the working version to you instead of

having to loft up a version that you might not want.

Lofts tend to like nice curves and I can see where you might run into trouble with the pocket. One idea might be to

split up the loft so that you do the top section separately and the rail becomes the centreline and the corner edge

will be calculated differently.

If you want structure under the loft then one method might be the way that many of the aircraft modellers create

the internal structure of aircraft. Model the loft as a surface initially and then thicken the loft to the desired

thickness, this will be your wooden top. Do another loft as a full depth body to the surface of the Guitar and create

your rib structure from this. Trim the surface of the full body with a combine cut with the initial thickened Top you

created. Then REMOVE the parts of the full loft body you don't want leaving the ribs and the top fitting nicely

together.

I am writing this on the laptop away for Christmas at present but I will try to fire up fusion remotely and post

an example file. If not @davebYYPCU is very good at this technique and may have a file to guide you with.

Cheers

Andrew

[Drewpan]

Dave,

One of these days I am going to outright beat you! 😎

Andrew

[davebYYPCU]

And I was held up watching the video, so I don’t stick my foot in it.

[massmasskaressmassmiass]

Unfortunately, I'm just trying to understand the capabilities of Fusion functionality. But, to my even greater regret, I'm not a native English speaker. Therefore, it's quite difficult for me to perceive your attempt at help in text form.
... - if the solution to my problem seems obvious and not too difficult for you, and if you have time and opportunity to look at my project, then I will attach the file to this message. If nothing works out, I won't be upset. I'll try to implement the project in Blender. But, it's just more difficult to work with precise sizes there. Fusion seemed more convenient in this regard).

[massmasskaressmassmiass]

I apologize for the confusion. At the moment I do not have access to a computer, I had to answer you from another device, from another account. 

But it's me, Leescien).

[davebYYPCU]

No problem, thank you for the file. 

Start over.

Do you know the centre line of your guitar sketch 1, is only 50mm long?  Very small.

You must calibrate the canvass/s to actual size.  Scaling after with spline curves is nearly impossible.

Next the Spline curves in sketch 1 (Shape) are not tangent connected, so this means they will not be able to be used in Loft as Rail.  (Yellow line must be Tangent.)  

I might be doing the horn section as a Patch off this big surface Loft for the rest of the body.

Might help...

[leescienseen]

Understood! Thank you! So, only a more thorough reworking of all the lines of the sketch will help? Otherwise, there is no way to connect the end points of the guides to the external shape?

[davebYYPCU]

What size is the model Shape, centre line? (Will find it on canvass)

Fusion Loft - Yes must be very accurate.  For loft, Rails must be tangent connections, profiles - not required.

Because the Horn shape makes overlap, have to do it separately.

Might help…..

[leescienseen]

470 mm along the center line. Error in all sizes - lack of 0 at the end. Sorry I didn't notice.

[TrippyLighting]

The problem with following that tutorial is that Austin Shaner also use not fully understand the underlying surfacing concepts. He makes good and helpful videos and I've watched a few of them as other users have referred to them, but the makes statements in his videos that sometimes are simply incorrect.

I wonder how he developed what he calls "his technique". I posted this years ago on this forum, before he created his guitars!

The horns indeed are very tricky and I personally would try this with T-Splines!

[TimelesslyTiredYouth]

Cowboy?

[davebYYPCU · Accepted solution]

Nah the guy said he was going to be quick, Trippy is refined accurate, all the way.

@leescienseen 

This is my rendition of getting the first go done, needs tweaking, as I have tried to follow the canvasses, and they result in lumpy, so from here, educated moves for the spline points in the profile sketches, (outlines are fixed) might smooth it out, let you fiddle.

Happy with the Patch for the horn, given Sketch A is so lumpy.

Yellow canvass icons are from the size change and without the original canvass could not fix them.

Might help....

[leescienseen]

Awesome, man... You were able to solve a problem in a few hours that I had been scratching my head over for about a week. 

I've been poking around in the timeline trying to figure out how you did it. I don’t know to what extent, but I managed to repeat your actions. 

I understand you even had to adjust the cross guides. 

Thank you so much for your efforts and time spent solving my problem!

You helped me a lot♡

[davebYYPCU]

Ok, some more tweaking

for picture ending 302 - edit Rail 2 to be tangent controlled to the extrusion.

for picture ending 416 - in the Patch disconnect chain selection and select each boundary separately.  Then you can also control tangent to the loft and extrusion of the centre line.

Might help...

[leescienseen]

Okay! Understood. Thanks)

[TrippyLighting]

I like @davebYYPCU approach. I d have recommendations on top of what he said.

For the perimeter curve I would stick with a single fit point spline except for the 2 horns. If the instrument is symmetric, I would only sketch half of it.One curve for most of the perimeter. One for he horn. Then I'd extrude surfaces from those curves and use the surface edges for modeling, instead of curves.

The rail curves I would model with control-point splines. I would also use fewer. One for each inflection point of the curvature. If you use too many spline control points of spline fit pints and also use to many rails for a single loft, the resulting surface becomes uneven.