Airplane Project Needs Lofting help

[lapointekm]

I just started Fusion 360 about 3 weeks ago so I can 3D print the fuselage of a T-2C Buckeye jet trainer for a radio control plane.

I’ve done a lot of reading and watching how to videos but have run into a bit of a roadblock and could use some advice and help.

I’ve created all the cross section profiles from the drawing in order to establish the plane outlines.    I put the cross sections on the construction planes to enable lofting the plane.  Unfortunately it’s a pretty complex shape, needing lots of spline points to match the profile.  I drew 1 side of each cross section and then mirrored the other side of it.

I tried lofting the profiles but I run into real issues with getting the loft to be straight.  Often it wont even loft for me due to the complexity of the shape.

Manual editing of the loft wasn’t working.  I tried to manually edit the mapping points, but moving each point was taking 10 – 15 seconds just to move the point.   I would click on the point, move it and had to wait for 10 seconds for the computer to move the point and then redraw the body.   Its not a slow computer with little memory either, not sure why it goes so slow.  Sometimes just moving the points cause the program to crash.   Besides that the process isn’t really conducive to both sides being identical.   Also ran into the program not saving the changes I made. So while its possible to do, I clearly need a better approach.

I tried using rails with the loft, that helped a bit but manual editing was still needed.  Again painfully slow to manually edit the mapping points, and getting both sides the same was difficult.

I could change the approach and do  half the cross section, loft and then mirror the body, not sure if that is a better approach.

I tried using the sculpt mode and a tspline cylinder for the fuse middle.   That works to some extent but getting the front and back lined up to the other bodies is still an issue.  Is there a better way to be more precise with sculpting?

So Ive come to a point where I could use some real advice from people more experienced with Fusion

So here are questions and items that I need help with

1. Any ideas on how best to break the jet up into pieces. I broke up the fuse at the inlet and exhaust locations due to the extreme changes in the profile, does that make sense or would there be a better way to break down this build?

1. Why does the editing of the loft mapping points become so slow, what needs to be changed to make that faster? Is here a way to turn off the redraw until all the mapping points are moved?
2. When I used rails for lofting I had 4 rails for the shape,  top, bottom, right and left.  Are more needed, or are there locations that would work better?

1. Manual editing of the tspline shape in sculpt mode is exteremely tedious, is there a way to select points and move them to match the sketch lines on the construction plane.

1. How do you merge 2 lofts so that the edges disappear, and any slight mismatch gets aligned?

1. Is it possible to smoothly merge a loft done in the modeling to a tspline cylinder done in the sculpt space, if so how is that done?

1. Any ideas for fixing the nose? Its an ellipse, coming to a point.  Lofting doesn’t seem to work all that well for the rounded nose.   I tried tangent at the point, but that did not smooth out the shape.  Is there a better way to draw the nose shape, and then have it match the rest of the loft at the first cross section?

1. Is there a help file somewhere that describes all the colors of the points on the screen. When I connect the rails, the intersection of the plane with the sketch is red, but what are the yellow points?

Any and all advice, explanation, pointing me to helpful videos is appreciated.

Thanks

Ken

[TrippyLighting]

Probably too many spline points.

Definitely too many profiles.

It is also quite possible that this works better if you split this into several lofts as there are strong curvature changes in your geometry.

[TrippyLighting]

Also, please share your model. Export as .f3d and attach to next post.

[TrippyLighting]

---

@lapointekm wrote:

I’ve created all the cross section profiles from the drawing in order to establish the plane outlines.    I put the cross sections on the construction planes to enable lofting the plane.  Unfortunately it’s a pretty complex shape, needing lots of spline points to match the profile.  I drew 1 side of each cross section and then mirrored the other side of it.

I tried lofting the profiles but I run into real issues with getting the loft to be straight.  Often it wont even loft for me due to the complexity of the shape.

Less is more:

1. Try to minimize the number of spline points.

2. Keep the number of spline points consistent in all profiles that contrinbute to a loft.

3. Use as few profiles as possible

Manual editing of the loft wasn’t working.  I tried to manually edit the mapping points, but moving each point was taking 10 – 15 seconds just to move the point.   I would click on the point, move it and had to wait for 10 seconds for the computer to move the point and then redraw the body.   Its not a slow computer with little memory either, not sure why it goes so slow.  Sometimes just moving the points cause the program to crash.   Besides that the process isn’t really conducive to both sides being identical.   Also ran into the program not saving the changes I made. So while its possible to do, I clearly need a better approach.

Creation of geometry is handled by the geometric modeling kernel and is mostly single threaded. Fit point splines are also complex mathematical beasts as they are 5 degree multi span splines. Surfaces created from the splines are only 3 degree (modeling kernel limit) so there is another layer of approximation going on. Al that requires computing resources. The guidelines above will make this easier.

I tried using rails with the loft, that helped a bit but manual editing was still needed.  Again painfully slow to manually edit the mapping points, and getting both sides the same was difficult.

I could change the approach and do  half the cross section, loft and then mirror the body, not sure if that is a better approach.

I tried using the sculpt mode and a tspline cylinder for the fuse middle.   That works to some extent but getting the front and back lined up to the other bodies is still an issue.  Is there a better way to be more precise with sculpting?

Yes, but it is hard to provide advice without having seen the model. Sculpting might well help you here wit the complexity of the shape. It would be nice if you could post a reference image of the thing. You can also loft in the T-Spline environment an that might actually be a good start . The same is valid here as well. Use as few control vertices/polygons as necessary.

So I've come to a point where I could use some real advice from people more experienced with Fusion

So here are questions and items that I need help with

1. Any ideas on how best to break the jet up into pieces. I broke up the fuse at the inlet and exhaust locations due to the extreme changes in the profile, does that make sense or would there be a better way to break down this build?

1. Why does the editing of the loft mapping points become so slow, what needs to be changed to make that faster? Is here a way to turn off the redraw until all the mapping points are moved?
2. When I used rails for lofting I had 4 rails for the shape,  top, bottom, right and left.  Are more needed, or are there locations that would work better?

1. Manual editing of the tspline shape in sculpt mode is exteremely tedious, is there a way to select points and move them to match the sketch lines on the construction plane.

This is probably indication that you used to many polygons.

1. How do you merge 2 lofts so that the edges disappear, and any slight mismatch gets aligned?

Use continuity settings provided in the loft interface. this requires pick edges for lofting, not sketches.

1. Is it possible to smoothly merge a loft done in the modeling to a tspline cylinder done in the sculpt space, if so how is that done?

1. Any ideas for fixing the nose? Its an ellipse, coming to a point.  Lofting doesn’t seem to work all that well for the rounded nose.   I tried tangent at the point, but that did not smooth out the shape.  Is there a better way to draw the nose shape, and then have it match the rest of the loft at the first cross section?

1. Is there a help file somewhere that describes all the colors of the points on the screen. When I connect the rails, the intersection of the plane with the sketch is red, but what are the yellow points?

Any and all advice, explanation, pointing me to helpful videos is appreciated.

Thanks

Ken

---

[lapointekm]

Thanks for the response

I attached the model

I'll take another look at how to reduce the number of spline points.

I'll also look at breaking  the fuselage into more sections, but then having the same curvature at the joints becomes a problem.

[davebYYPCU]

The file to review is a great help, 

In addition to Trippy's advice, 

I work from outside -> in, meaning get the skin to conform to the canvass, before slicing for profiles.

This screams at me to be T-spline, but I don't have those skills, so I would attempt this with Surface / patch Lofting.

I generally use the top, side views as profiles, and some important formers as rails.  Canopy and nacelles come secondary to the smooth underfuse.

That your formers are not complying to the canvass, is going to make a hard job for you.  Zoom in, only H former hits the line.

Might help...

[TrippyLighting]

@lapointekm thanks for sharing the file. I don't have the time currently to help much with modeling, but I created a screen recording that explains a better approach.

What you need to do is ti identify the primary and secondary surfaces and then create those separately and not as one large interconnected loft. Hopefully the screencast helps.

[lapointekm]

Thanks for all the help and suggestions.

I was able to reduce the number of points on each former pretty significantly when I made the canopy a separate piece.

I also redrew the front nose formers to get them all the same number of points.

I eliminated a couple of former's where I could

As you can see in the picturethe result appears much better now, still needs adjustments here and there, but its getting closer

Next I need to make the wing and stabilizer.

Thanks again for the help.

[Beyondforce]

Hi @lapointekm ,

Maybe this might help:

https://www.youtube.com/watch?v=Va39Zlrm4EU&list=PLjGKAi--ZCoZntY2C0JwUjp-FZvqQUgOl&index=4

Cheers / Ben

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