To get a better end shape there, you probably want to either have the end come to a single point like the front part, or maybe if you didn't want to do that because it's kind of flat you might want to make it come to a flat end shape initially and then put a planar cap on the end and then fillet where they connect.

For the latter one you'd want to have the long rails end without swooping downwards, more like so:


- Michael

Thanks very much for the tips Michael.

I'll clean up some of the geometry and see how that goes, makes sense that 'wrinkles' would cause problems, not sure how I ended with them though.

With the tail-end I tried to Loft the tail the same as the nose (to an end point) but the Loft function didn't want to play ball. Actually the Lofts (on the four curves) seemed to be governed a little by the general happiness in the universe (ie: random) with a view change (zoom out seemed to help) sometimes causing the loft to succeed or not, but perhaps my swooping long-curves caused problems? I'll try the plan-off the end and see if I can then fillet it back to a softer 'cap'.

Will report how I go. Thanks also for the fold-over link I'll read that as well.

Hello,

You could try a two rail sweep with some regularly spaced profiles. This seemed to result in smooth surfaces as opposed to some other methods I tried out.

Which program is doing the zebra striping?

argo, what is the purpose of such a large vertical stabilizer?

Hello,

It's generated by the Lightlines feature in the VSR Shape Modeling plugin for Rhino 5.

Thankyou.

Hey that's very interesting OSTexo, thanks. I take it the rails are in the vertical plane when viewed from Front view? And the profiles are ellipses perpendicular to the rails?

Sort of on the same subject I came across MajikMike's MACH16 tutorial for a Networked organic shape. I tried it tonight and it gives great control as the control points can be manipulated, with the Networked solid following your changes - very cool. Only problem is getting the ends of the model smooth, as Networking used in this way is susceptible to non-tangent control points. I take it a two-rail system is not so sensitive at the tips?

Here's the tut if you have not seen it: http://moi3d.com/forum/messages.php?webtag=MOI&msg=5188.1

Thanks & cheers.

Hey Chris

Not sure if you're a RC plane-nut like me, so sorry in advance if I write the obvious! This is a fuselage for a slope glider design affectionately called a "Plank". Its called this because its basically just a wing, often without a fuselage at all. I'll post a picture below of one of my favourite planks.

The reason the vertical stabiliser is so large is because its moment to CG (how far the fin is away from the centre of gravity - think of a lever) is short. This means there is very little lever-effect to keep the glider's yaw in check. End result is the glider tracks like its on rails with a decent setup including large fin. These are not slow gliders, the speed record for a type of gliding called Dynamic Soaring (DS) is approaching 500MPH - yep faster than a light aircraft. This sport uses the sheer-layers of air you get with wind as it crests a mountain slope.

And now you've got me rambling about my hobby :-)

The UberMoth:

Hello,

Yes, that is correct. It also seems to work well when I tried out some lifting body sort of profiles instead of just ellipses. The two rail sweep gave a nice result as long as I made sure there was a profile set close to the nose to guide it properly. I fiddled around with moving the amount and position of the profiles and it seemed that an even distribution of profiles making sure that there were some close to the ends of the fuselage worked well. It takes a bit of work to get the curvature correct, but I found that Blending, Joining and Refitting the curves works. It is very easy to do this in Rhino+VSR but it can be done in MoI with a little more effort.

I'm familiar with the distance of the surface from the CG and relation to the area required.

Because it increases the area, does it make motion from crosswinds more of an issue or am I missing something?

Perhaps because there is no fuselage that would also increase the area from the side profile, there really is not an overall increase in the area compare to a more "conventional" aircraft design?

OSTexo just want to thank you for 2-Rail Sweep suggestion :-) I ended up using that method and it really was the easiest, plus it gave a surprising amount of control of the shape through-the-model via the profiles.

At the end of my build I tried to round-out (fillet) the interface between fin and fus, but its difficult geometry and in the end I was happy just to leave it. Below are images of the end product, its being printed in PLA and ABS plastics as I type. Printing required splitting it up so my print guy could get it on his print bed, plus hollowing it out saved some cash.

Cheers and thanks everyone for their advice and tips. Michael I'm singing MoI's praises to my fellow glider builders, you may see some more interest from this hobby segment :-)

BTW chrisd - good thinking on crosswinds affecting the big fin. I had to think about that one as the answer is no, but why? The reason I believe is that the glider flies WITH the airflow (wind), not in competition to it. This means there is no "crosswind" to a glider. The tail is there to fight the glider's inherent aerodynamic imperfections which are magnified by a wing-only ("plank") glider. As the wing moves through the air, imbalances cause see-sawing which the fin dampens out. Hope this off-the-top-of-my-head explanation makes sense.

Hello argo,

Not a problem, I'm glad the suggestion worked out for the design. Is the fuselage shaped in that way to add lift or stability to the glider?

Hi OSTexo

Other than the fin for yaw damping the fuselage has little impact on the aerodynamics of the glider (its all about the wing).

Smooth lines do however reduce parasitic drag of the interface between the fus and wing and also look cool :-) . Practically speaking the fus is there to: provide a tail to mount a vertical stabiliser (fin) to , and provide a nose to add lead to balance the glider around its CG (centre of gravity). Longer the nose the greater the leverage, so less weight required.

Cheers & tnx again.

Hi All

I thought I would post my 3d print experience with this model. Very cool to see a design come to life and the shape and dimensioning are good, however I have ended up with a course or aliased finish as the attached photos show. I exported my model to STL with 6 degree angles, just wondering if anyone could suggest what setting I actually should have used? Also its fairly obvious I did not make the tail thick enough and with the lack of detail it has actually 'faded out' and not been printed in places!

Of course the printer is a major part of the equation, however I have seen/felt some of his other prints and they are much smoother than mine even where curved.

Any suggestions would be much appreciated, as I'm keen to make this work.

Cheers, Brendan.

The faceting I see appears to be from the "printer" and not the STL. Maybe you could talk about "who you sent it to" or what printer was used. THis would help.

Good point, sorry!
It's printed on a Makerbot Replicator 2x by a local makexyz print guy. Thanks.

Hi Brendan,

As Burr mentioned it's not the STL file that is a problem, you can send the 3d print guy a super dense mesh and the end result will be the same.
This is a stepping phenomena that's common with 3d printing because the way the material is layered on step by step even with the Replicator with a 0.1mm (0.004") resolution.
The effect is more visible on curved areas, imagine a tiny staircase and it's more obvious on items with gentle curves such as spheres which your model shows.

Usually model guys will over size areas to allow for sanding to achieve a smooth surface.

There are other 3d printing technologies out there that will do a finer job unfortunately the price increases also. To get a better idea check out Shapeways they have variety of materials and processes to give you an idea on what's out there http://www.shapeways.com/materials?li=nav

Hope this helps.

Cheers

that part does not look like an STL printer part but a part from a Stratasys printer (or that type) that extrudes plastic through a modeling tip.

Is that part plastic or the actual laser / light cured resin of an STL machine? STLs, unless the machine is very cheap that is being used or very old, have much higher resolutions that what your part shows. The plastic extruder types give results that look just like the pictures you posted.

The first image (the close up) is what is drawing me to that conclusion. In my former career we had several machines that we used in-house and that looks just like the plastic extruded technology from Stratasys.

Are the red parts the cured resin but just painted? If so, the resolution on the machine that was used is pretty bad. A good machine and 30 seconds with high grit sand paper will make the cured resin parts smooth like a baby's bottom.

Hi Brendan, yes as others mention above the kind of layering effect that you're seeing there is a part of the printing process, there isn't anything you would do about that in the STL file generation itself.

If you've seen smoother prints from the same machine previously, it could be possible that the machine needs to be recalibrated or that there was some kind of post processing done on the smoother parts that you saw, like sanding, tumble polishing, acetone dip, stuff like that. You might want to ask him about what process he used on the smoother parts that you saw so that you could get the same thing done on your parts too.

It's really cool to see your model manifested in physical form!

- Michael