I believe that will be the same in the free 123D ;)
http://www.123dapp.com/

Pleas bear in mind that I am new to MOI !

However - based on previous tuition by Michael, Burr and others- her is my latest attempt..............


And the model itself............


This does expose my somewhat cumbersome construction techniques. In particular how to replicate the rear face of the front fillet when constructing the rear fillet ?



As before - all advice most welcome.


John

Hi,

When I went through this not long ago I tried Autodesk 123D and it doesn't import or export 3dm. Maybe someone knows if I'm wrong about that now. MoI can easily do this fillet task though. It's just of matter of figuring it out. It took me awhile too but what Burrman is showing is essentially the same thing I arrived at.

Make your wing a solid, make your plane a solid. Union them. Then fillet will work fine on the intersecting curve it makes. The reason I make the wing and plane a solid first is that sometimes there can be issues with either one. So this way you find which is messed up. But burrman did it all in one op which is fine too if you have good geometry.

What I do and what could work for you is make a leading edge (le) and trailing edge (te) curve. Then make an airfoil cross section out of two curves. A pressure side (bottom) and suction side (top). Sweep the airfoil curves along the two rails. Then see if it will union into a solid. If it does you should be good to go. I found lofting like burrman was doing can create some problem areas. Sweep gives you a very smooth surface. But lofting could work for you. You don't have as much twist as a propeller has. It looked like the lofting was working fine in burrmans video. I've never experimented with sweep when you have a non-constant chord like you do. You might need a height rail too. Michael or burrman would probably know. Bascially you would have to make sure the airfoil is scaling appropriately. I don't have that problem because I have a constant chord distribution.

Autodesk 123d is a bear to download and install. Also the interface is redonkulous. I think they were hitting the c-pipe when they came up with that. I prefer MoI. The other thing I liked about MoI was that it forces you to model more like you would build. Yes other software may work in more situations but thinking about how its made and modelling it that way seems like a good idea to me. My experience was all the failures I would have with MoI were in situations were you couldn't make it anyway. If you can make it MoI can model it.

I did have the issue with tolerancing however. That required an unintuitive switch to the mm unit system then back to the meter system I was actually using. Other than that MoI gets an A+ from me. Your fillet is way bigger than mine though, so this probablly won't affect you.

Just my two cent, I can see you're already well on your way to success.

Hi prop_design !

I took courage from your earlier post !

I can truly say that I learnt a lot from this exercise. I found that I was rushing at things - and missing screen prompts - so I took a deep breath and slowed down.

One thing I discovered - I had not really fully understood the original wing geometry.

In the front view the profile of the wing has straight line top and bottom - but in plan view there is a kink in the leading edge. Therefore the wing root section cannot simple be scaled from the mid-wing (or tip) sections.

Yep - accuracy is paramount - if your geometry is out things just will not work.

I will probably go back (at some stage) and start again.

There's an old joke in the UK -City Type to Local Resident --- " How do I get to ?????"

Local Resident to City Type ---- "Well, I wouldn't start from here"

Thanks again for your feedback


John

The problem that MoI hits and AD fusion doesn't, is, I think in the way the fillets are constructed. AD seems to recognise a sharp edge and when it does, it automatically extends the fillets until they cross then trims them back to a sharp edge. It must interpolate the crossing in some way, as the extended fillet surfaces won't always meet exactly. MoI doesn't have this interpolation and gets in a knot. Michael G will know why it works in one case but not another.

PS: just tried it in Rhino, which works if Distance between Rails is selected as the fillet type.

>When I went through this not long ago I tried Autodesk 123D and it doesn't import or export 3dm. Maybe someone knows if I'm wrong about that now. MoI can easily do this fillet task though.


Well just export in Moi3d to .SAT and import this in Autodesk 123D. Works without any problems. If you export from Autodesk 123D to .SAT as well, Moi3D will be able to import it without problems.

I found Autodesk 123D a bit better with filleting.... I really hope Michael can improve the filleting or build in filleting as seen in Autodesk 123D.

Peace,
Rich_Art. ;)

Hi Steve,

> MoI doesn't have this interpolation and gets in a knot.
> Michael G will know why it works in one case but not another.

Theoretically the "straight corners" option in MoI is supposed to produce the kind of result that would be wanted here, but it seems to have difficulty intersecting the fillet pieces with one another, probably because they are of different widths where they cross.

- Michael

Hi Rich_Art,

> I really hope Michael can improve the filleting or build in
> filleting as seen in Autodesk 123D.

It's not really so much up to me - I didn't write the fillet code for MoI, it comes from the Solids++ geometry kernel.

Filleting is not really a very strong area of the kernel, although they have made some incremental improvements.

Filleting tends to be an area that requires a lot of special case handling for different kinds of situations so it is a difficult area to develop well. It's not like you get better filleting by just improving one section of code, it's more like you add more and more kinds of specific handling for various different arrangements for how edges come together.

- Michael

Hi Michael,

Thanks for the clarifications. To bad to hear this but I still like Moi3D very much. In cases where the filleting of Moi fails I can use autodesk 123D. In most cases Moi is sufficient for me. :-)

Peace,
Rich_Art. ;)

Thanks for the tip about getting a MoI model into Autodesk 123D. That could be useful in the future. I uninstalled Autodesk 123D however. I didn't care for it much. I was eventually able to figure out how to fillet in MoI. One thing I can say about how you describe Autodesk 123D is that its convenient from a modelling perspective because it does what you want the first time. But fighting with MoI I came to understand what does and does not work. In the case of the wing example how burrman showed it makes a lot of sense from a real life perspective. They would piece the wing together from sections that extend from leading to trailing edge then apply the fillet. Rather than have a narrow wing and extend the fillet. I found this type of thing with my trial of MoI. It will work in situations where you have specified things in a manner close to reality. But having it mystically determine how surfaces that haven't been drawn should look is outside its capability. From an engineering perspective you want the human determining how things should look rather than a piece of software you may know nothing about determining it for you. The wing and the blend to the body and the body itself in reality would all be determined by careful analysis and/or testing. So those surfaces would be modeled precisely in reality. Since they all affect the performance. There wouldn't have been any question in the original engineers mind as to how those surfaces and blends would be defined. So I don't think this is something outside of MoI's capabilities. As burrman shown, once you define the wing and body, then union them together, the fillet function works just fine. I found the same method works for propellers too. Granted MoI can't fillet a surface that hasn't been defined, but to me that is a situation you should never be in anyway, so it's trivial in my eyes. Not to mention the gigantic install and goofy interface of Autodesk 123D. MoI is the better solution by far.

I, too, tried 123d and have uninstalled it after an hour playing with it. It is bloated and cumbersome.
I am spoiled by MoI ... most other software seems clunky by comparison.
cheers,
eric