Need to learn CAD as first step - advice please

[pierre]

Hi -
I'm planning to build bearhawk 5

i know how to use lathes and mills, but I'm totally useless at CAD, and I think putting the drawings into CAD and / or solidworks would make life way easier, and also I would learn good skills



total beginner - never used any CAD
I got a bachelors in aeronautical engineering and aerodynamics 1995-1999, which was 23 years ago. back then we used pencils and paper. it ouwld be fair to say I am useless as CAD


questions I have are -

1 - what program should I learn how to use
2- how is the best way to learn ? youtube?

[jaredyates]

There is definitely no need to do any CAD. If you'd like to, that's a separate pursuit that might be fun or enlightening.

[Daniel]

I wouldn't call it a separate pursuit. It certainly can be helpful for a builder to visualize concepts prior to building. Especially the instrument panel layout. Garmin makes most components available for solidworks from their website so that builders can fine tune and thier concepts prior to cutting any parts. Many other applicable uses as well. Needed, no...useful, absolutely!

[Sir Newton]

CAD programs do not build or test fly airplanes. lol

[SpruceForest]

Pierre:

BSAE Degree in '89, when we were still required to keep a physical lab notebook and write out sample calcs/final report in longhand for Dr. Winklemann's aero labs... and ink the final drawings for the capstone design project. Going through the same process as you, with a focus on building once in the computer to avoid building multiple times in the real. Take this advice as coming from someone a step or two ahead of you on the journey, versus the more valuable hard-won wisdom from a veteran with boots many times reshod and years on the trail.

Note that there are several other Bearhawkians (Bearhawkers? Bearzerkers? residents of Patrolville?) working in Solidworks and posting here, so if your goal is drawing files versus CAD/analysis proficiency, leveraging the reduced-cost EAA Solidworks for Makers may be a good fit. In my case, one of the folks at work (shadowy quasi-government think-tank) with four decades of computer design experience suggested F360 for someone without real experience with a design suite (design/analyze/manufacture etc.).

Autodesk has 3 year-long educational and small business startup programs for 'free' use of the standard version of Fusion 360, so my life-long dream of becoming a manufacturer of plans and kit-built float and amphibious landing gear came along at precisely the right moment to justify Autodesk's designation of my effort as a start-up. I should note that the process to qualify was arduous... I spent what seemed like days (but was in fact 15 minutes or less) creating a spin-off social media page for my startup, and then linked to social media site in my application. All told, perhaps 30 minutes of time to get Autodesk's buy-in on my aspirational goals in the form of three years and about 1200 rapidly shrinking US dollars or so of access to Fusion 360.

I got started by running through Lars Christensen's basic Fusion 360 tutorials on YouTube, as well as his aero-oriented airfoil and aerostructures tutes, using various bits and pieces of the Patrol as subjects for the second pass through the vids. This is a 'two birds - one stone' task, as converting what can be sketch-level details in Bob's plans (e.g., flap and aileron nose rib flanges) nails down a lot of details that lead to more accurate jigs and fixture design.

As workflow in any process is more progressive revelation than cookbook guidance, I've been redrawing parts as my proficiency improves. I've managed to devote about an hour a day to focus on the Fusion work, and have started building out the flap, aileron, and main wing spars, nose ribs and other support structure... shot is the RH flap as it stood a day or two ago.

Sure...baby-steps, right? But progress all the same ;-)

Good luck!

Todd

PS - In the vein of 'the map is not the ground', since Jan 11th (the date I ordered the plans from Bob), Ive also managed to build out the complete set of templates, forms, and cauls for all the wing/aileron/flap ribs, set up and press/form prototypes of sample nose, flap, and aileron ribs (aluminum order en route)... the CAD work happens when I have time away from the 80 hours a week as an avionics researcher engineer/other full time gig as guitar builder/repair guy, and actually making progress on the Patrol scratch-build effort.

[sjt]

No need for cad. But, I do not do not follow my recommendations.
I would recommend the cad program that comes with the EAA membership -solidworks

Although mostly I only use it for 3d printing plastic.

https://www.eaa.org/eaa/eaa-membership/eaa-member-benefits/solidworks-resource-center

[pierre]

Dear Chaps,

many thanks for your fabulous tips .


I will get going with them

I want to get good at CAD because for my work being able to rapid design and rapid protoype small devices is super useful, not to mention long term plans to build a bearhawk .



by the way I love the "Bearzerkers " name
very apt.
also reminds me of a line from CLERKS, one of my all time favourite Kevin Smith movies, with my all time favourite characters Jay and Silent Bob.....

great hearing from you, Pierre

[pierre]

Can I trouble you all for one more question?


can any CAD programs do reasonable quality fluid dynamics anaylsis?
If not - which CAD design program lends itself to easiest analysis of airflow and computational fluid dynamics with another software package? or is that not possible?


the reason I ask is as follows -
re bearhawk - I would love to weld a cargo pod under the fuselage - this will help stiffen the fuselage, but I'd be interested to see what effects it has on the drag. I'd also be interested to see the effects of wing-tip winglets, just for fun.

2nd reason - i'd be interested to see if engine cooling exiting sideways, like the wolf cowls on a Pitts, would help reduce interference drag (meredith effect), or if that makes no difference due to the high wing

many thanks, Pierre

[Daniel]

I've used solidworks fluid analysis a few times. The free package through EAA does not have it. It can do complex simulations like through an engine cowling but, that would be hundreds of hours of modeling. Also, when it comes to those types of analysis, the results need proper interpretation based on the study parameters. I have done lots of load simulations and some fluid analysis is solidworks. Air flow through a cowl is not something I would attempt.

[Chris Werner]

There is a program called FreeCAD. I've never used any 3d software and I'm learning this on. It was free to download and there are a bunch of good tutorials on YouTube. I have been able to draw a few items and get them to quote for cnc machine or 3D printing. Might be worth a look.

[SpruceForest]

Again - caveat: no direct experience with either Fusion or SW CFD. Both apps appear to have add-on CFD modules not included in the standard or student editions (as mentioned above re: Solidworks and the EAA reduced cost version). You may want to leverage available engineering fora for more in-depth comparisons and advice from primary users... the Engineering Tips site (https://www.eng-tips.com) is usually a decent place to start for this sort of get smarter effort, then it's down the rabbit hole to the more esoteric sites that will likely be mentioned in the relevant threads. Also consider the user fora for the applications themselves re: taking a look at the problems being encountered in use or solved with the CFD capability. Finally, consider checking in with other communities of practice - particularly the larger ones like VAF - to cast a broader net.

[nborer]

I agree with the folks here that CAD is not necessary for the Bearhawk, but I can see its benefits in terms of visualizing assemblies in 3D, etc. At one point I thought about doing it, but I've found that sitting around many evenings with a glass of wine and walking through the 2D drawings while making notes is just as helpful for me.

I'm a practicing AE and finished my BS a year later than you (class of 2000) - though we did do a small amount of 2D CAD in school. I had an engineering internship that included updating hand drawings that dated as early as the 1940s, 2D CAD drawings, and even some solid modeling (SolidWorks 95!) when I was a senior. I picked it up pretty quickly, and suspect you can too. I did download SolidWorks under the EAA membership deal (when it was free, not discounted as it is now), and found that the whole interface had changed massively and/or I had completely forgotten everything. I never did jump at it and elected to just start banging out ribs.

Regarding flow solvers, the CFD folks I work with are pretty snooty about most (all) of the codes that are attached to the CAD programs (and for that matter, most of the structural analysis tools). That doesn't make them wrong, but CFD and FEA are very sensitive to gridding, resolution, etc. It's not something that's easy to "pick up," at least in my opinion. I took a CFD course in grad school and even wrote some code, but I farm it off to the experts I work with. I am trying to learn some OVERFLOW for a mix of work and home stuff but haven't had much time to pick it up. It's not an easy feat - it takes far more effort than picking up a CAD or solid modeling program.

I usually use lower-order flow solvers that don't require the detail for CAD for most of my day job - vortex lattice & panel codes, as well as simple 2D boundary layer models and semi-empirical methods. AVL, XFOIL, and XFLR5 are all free and can get you some answers, but you have to know what is and what is not included in the answer. OpenVSP is a great, free, parametric 3D modeling tool that has a built-in solver called VSPAero. For something like the Bearhawk - low subsonic, incompressible flow - VSPAero should be pretty good. Like all of them, take the answer with a grain of salt. I did start building up a Bearhawk model in OpenVSP, with the hope of eventually porting it to OVERFLOW to look at some options for the flaps. (I'm 95% sure I'll never actually finish it, though, and will use the tried-and-true design in the plans.) When I do stuff for my day job, the geometries provided by OpenVSP do more than a good enough job for gridding to OVERLFOW, FUN3D, etc. Most flow solvers actually need you to attenuate the details that you'd otherwise put into CAD - those small details add numerical noise that gets smoothed over in "real life" but can provide misleading answers (at best) or stall the solver (typical).

Whatever you choose, enjoy! I've had to take over a year off from building because of an unexpected/emergency remodel to 40% of my house, but I see light at the end of the tunnel - I'm finally getting my garage/shop back in order. It's nice to bang on metal after a day of staring at a computer screen, but maybe that's just me. Find your zen and have some fun!

[geraldmorrissey]

My local community college offers CATIA classes. Don't get much more high end then that. Take a few classes and Boeing will hire you.
Gerry
Patrol #30

[spinningwrench]

I am modeling much of my Bearhawk Patrol in Solidworks. I taught Solidworks for 25 years so it is pretty second nature for me. As many have stated there is no need to do CAD modeling but I find it very useful for creating complete assembly drawings of how my Patrol goes together much in the style of what Van’s does for all of their kits. These drawings are really useful for many reasons. The first is that I model all my sheet metal pieces and then download the file to my CNC router for cutting. Secondly it is so handy to have reference drawings calling out all the hardware and how everything goes together.