gld's lofting problem

[gld]

The problem is with Loft<Sect4>

I hate to bother you fellows again but this problem has me knocking my head against the wall. Here's the error code that Alibre posted.
{ACISERROR_SKIN_GUIDE_NOT_START_STOP: Guide curve does not start and stop on the first and last profile respectively.}

I used Alibre's coincident constraint to attach both ends of the guide curve to the trailing edge of each rib, so I'm at a loss as to where to go to fix it. I've been trying to fix this for several days.

Thanks for any help

 

[HaroldL]

I noticed a couple of things:
1 - the guide curve is not constrained to anything:


2 - The end profile has an issue. When I try to select it, it highlights at the other end of the wing at a rotated orientation. And shouldn't it be on a plane perpendicular to the starting profile?

 

[simonb65]

2 - The end profile has an issue. When I try to select it, it highlights at the other end of the wing at a rotated orientation. And shouldn't it be on a plane perpendicular to the starting profile?

I've seen that issue in the past on earlier AD versions. It was supposed to be fixed, but I guess it's still lurking in the background!

 

[bigseb]

This type of shape is imo a bit beyond AD current capabilities. Sure you could sit with it for a considerable time but even then it won't be 100%. The updated loft tool should be much better but not sure when that will be released. Moi is a cost effective solution too. Much better at the flowy stuff like this.

 

[gld]

This type of shape is imo a bit beyond AD current capabilities. Sure you could sit with it for a considerable time but even then it won't be 100%. The updated loft tool should be much better but not sure when that will be released. Moi is a cost effective solution too. Much better at the flowy stuff like this.

What is Moi? I saw it referenced in another thread you posted. Are you saying this will not work in Atom.

 

[gld]

2 - The end profile has an issue. When I try to select it, it highlights at the other end of the wing at a rotated orientation. And shouldn't it be on a plane perpendicular to the starting profile?
View attachment 34365[/QUOTE]
Yes Harold, I saw that and am trying to figure out what it is.

 

[bigseb]

What is Moi? I saw it referenced in another thread you posted. Are you saying this will not work in Atom.

I doubt it will give the exact required outcome. In my experience lofting will require a ton of cross sections and even then some fudging.

Moi is a surface modeller developed by the same person that also coded Rhino. As far as modelling capabilities go it is far more versatile than Alibre. A license costs $295. It isn't parametric so AD and Moi have slightly different uses. Worth checking out.

 

[idslk]

Hello gld,

i don't have MOI nor Atom...


Sorry

Regards
Stefan

 

[bigseb]

That leading edge looks bit iffy from this angle...

 

[albie0803]

In your file, your trailing edge is not a straight line, nor does it run down Plane7 as I assume you have expected it to. You have built your guide curve on this plane, but as you can see, Sect4<R7> doesn't link to it. Therefore Guide curve does not start and stop on the first and last profile respectively. I was going to show you how to anchor the guide curve using points like Stefan did but Atom doesn't have them. So, I suggest moving Plane7 up to under plane 2, drag the dogbone up above the first loft, insert an axis using planes 1 & 7 and then constrain the trailing edge point of Sect1<R2> to the axis.

Do the same with the outer sketch of each loft, then your trailing edge will be straight and will be on Plane 7

Section4<R8> opens as a symbol, not as lines so I couldn't constrain the trailing edge point to a new axis. If you change this you should be able to then constrain your guide curve to the new axes which should then connect everything.

 

[gld]

albie0803,
I discovered today that plane 7 was not parallel to the trailing Edge it was off by .1 degree, I corrected that. I also discovered the problem with Sect<R8> and corrected that. The guide curve was also changed to be a spline. The loft still doesn't work. I've uploaded my changes to the part file in post number one. Tomorrow I work on your suggestion and see how I get along with that.
Thank you for your input.

 

[HaroldL]

The end sketch is still not perpendicular to the starting sketch, which it needs to be if you want the winglet to curve upwards. Also the guide curve is not constrained to either sketch.


Add a node to the ends of each of the profile sketches. Then Insert Point from Sketch to each node. That will give you a point that you can constrain the guide curve to.

 

[gld]

I have discovered my airfoils do not have a node at the trailing. Hence nothing to snap too. A correcting that problem now and will start from scratch following albie0803, suggestion.

Question about the guide curve. I assume it should be a reference figure so as not to get the warning on closing the sketch.

Harold
Atom does not have a node or point function. another dam it.

 

[HaroldL]

Gary,
Sorry, I didn't notice in your signature that you have Atom. I've just gotten used to a workflow that works for me in Expert and forget that not everyone has the same tool kit.

What were they thinking?

 

[gld]

.

What were they thinking? [/QUOTE]

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

 

[gld]

Harold
Atom does have a point function. I found it.

 

[albie0803]

Aside: I wish Expert had a mode switch to atom for helping people with atom. (Disable all non atom commands) Its hard to try and work out what is available for use. Or supply Pro/Expert users with a free copy tied to our serial or activation key.

With the guide curve, this is one of the times when you can ignore the warning, as it is what you want.

 

[HaroldL]

Aside: I wish Expert had a mode switch to atom for helping people with atom.

Not the same as a mode switch but in the Help manual there is an indication on the Heading page of some items as to which version it is available in. You just have to page thru the manual to find them.

My guess is that if it doesn't indicate the version availability then is should be available in all versions.

 

[bigseb]

This is about more than just guide curves. The current loft tool is too limiting wrt what it can achieve. Even with guide curves there have always been blending issues (bulges, sharp corners, etc). Aerofoil shapes have to be smooth.

Also if you look at the profiles in the OP the main wing section has the typical aerofoil shape i.e. flattish bottom, roundish top. However the last profile (the upturned bit at the end) has a different shape in that it no longer has the flattish bottom. No guide curves in AD are going to give a smooth blend.

AD's new and improved loft tool might be the solution here. I have a feeling that the 'face-off' option might give a much better result. We'll just have to wait and see. In the meantime a much better blend might be achieved using other software like Catia, Creo, Rhino, Moi, maybe others.

 

[HaroldL]

It's kind of sad when you have to use other CAD software to achieve what Alibre should be able to. Even when new capabilities get added it seems like they are rushed at the last to get them into the release then the next several releases are needed to make corrections, updates or whatever to get them to their full potential, if they ever do.