Is VSP right for my project?

[Mark Waldron]

Greetings.  I'm brand new to VSP, but for years I've been wondering about the potential of a particular GA aircraft configuration, and am wondering if VSP could be a useful tool to learn more.

The plane would be a small two-seat, high-wing,  twin-engine centerline thrust GA aircraft--something like an approx 1/2 scale Cessna 336 (Skymaster).  The critical issue with a design of this type is achieving acceptable single engine climb.  So, I'd like to input the design into VSP (I've got an idea of major parameters--span, wing area, empty and target max gross weight, airfoil, etc) and then:
  1) See the design in 3D
  2) Get some basic aerodynamic estimates: L/D, equivalent flat plate drag (induced and form), and (ideally) drag curves for approx 40 kts through 170 knots. 
  3) Given thrust figures for each engine at appropriate airspeeds, find single engine climb rates and estimated cruise speed (on two engines)

In addition, other smaller issues concerning the aircraft's configuration would be great to model.  For example, it would be great to see the difference in drag (and performance) between tandem seating and side-by side seating.  In addition, some of those I am working with see great value in using wing lift struts, others would prefer to avoid them: seeing the drag (and performance) impact of the struts would be an important factor in making informed decisions going forward.

I know this is a tall order, and that VSP may not be able to do it all (maybe with Vorlac?).  But is it the right place to start, or should I invest the time somewhere else from the beginning?  Any suggested roadmaps (start with VSP, export to XXX to do xx) would be appreciated.

Thanks in advance for any suggestions.  I participate in other boards and know that "newbie questions" can be tiresome for the experienced group members.

Mark

[Brent Robbins]

Hi Mark,

OpenVSP will help you with #1 and 2 (if you have Vorlax).  I do not believe OpenVSP will help with #3.  If I were you, I would model your concept of the plane in OpenVSP, get some basic characteristics of it (wetted area, CD0, etc.) and then do a constraint plot diagram to size your engine appropriately for your performance requirements.  I am not aware of a free off-the-shelf constraint diagram modeler, but you may try getting a copy of Advanced Aircraft Analysis (AAA)...it has that capability.  Or...code one up yourself...it's not all that hard.

Brent

 

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From: Mark Waldron <markwa...@gmail.com>
To: ope...@googlegroups.com
Sent: Monday, January 5, 2015 6:30 PM
Subject: [OpenVSP] Is VSP right for my project?

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[Nelson Brown]

The AAA software is primarily a software implementation of the methods in Dr. Roskam's books: http://www.darcorp.com/Books/?url=/Books

Similarly, Dan Raymer sells RDS software as a companion to his Aircraft Design book: http://www.aircraftdesign.com/ (and web design that make you nostalgic for Netscape.)

Come to think of it, pretty much every aircraft designer I've met has assembled their own conceptual design software tools, but most of them keep it private.

Hopefully VSP will inspire more aerospace tools programmers to go open source…

Nelson

[rv6]

Another alternative is ADS

http://www.pca2000.com/en/software/ads-demo.php

Several version are available and the demo version gives a good idea of its capabilities

Jan

[Mark Waldron]

Brent, Nelson:  Thanks for the lead to AAA.  I'll try to sketch/render/model my idea in OpenVSP first, then see about AAA.  Would any of the 3d "depictions" of the design export to AAA, or would I be re-entering the numbers and making new drawings?

Jan,
  ADS looks interesting--it promises so much that I gotta say my spidey sense was triggered.  Have you had any experiences with it--feedback?  Heck, the demo price is right, and I usually learn something when I dabble in these things. I wonder if it can import anything from OpenVPS.

One big thing OpenVSP has going for it is this user community.  I'll try not to be a pest and require lots of spoon feeding, but I get the impression that there is honest help here without a vested interest in making any exaggerated claims for the software.

Thanks again,

Mark

[Rob McDonald]

Mark,

Welcome to VSP. I think you'll find that this community has a lot to offer.

OpenVSP is certainly not a one-stop turn-key aircraft design program.
You don't put requirements in one side and sized airplanes come out
the other.

OpenVSP tries to do a good job of the geometry -- and then we try to
feed a wide variety of the analysis that you would do in an aircraft
design study. For example, we make it very easy to calculate wetted
areas -- which you will need to do a drag buildup.

Some of the other members have mentioned some comprehensive aircraft
design tools. I don't think any of them have direct input or output
connections to OpenVSP, but I wouldn't let that stop you from using
either tool.

In general, I'm not a big fan of that kind of tool. Instead, I
require my students develop their own tools from scratch. They may
not get as far, but I don't think there is any substitute in Aircraft
Design to actually knowing what is going on in your study.

Rob

[Nelson Brown]

This.

[Mark Waldron]

Rob,
  Thank you--and thanks to you and the team for OpenVSP. 
  I agree that there's no substitute for understanding what is going on, and that building a tool to apply the formulii in the right ways (and to do the number crunching) is among the best ways for a student to learn what is happening. Among my concerns with any tool that "promises a lot is that 1) I'll miss out on some opportunities to learn and 2)The tool won't be doing what I think it is doing, and I'll get inapplicable results without knowing it.
  The best tool for a "piker" like me would be one that steps the amateur designer through the process and shows which formulii were applied, mentions any common alternative approaches (if applicable), and then does the math.  Raymer has been recommended by many sources as offering a text that can walk an amateur through the process, and then offers some tools to help with the numbers.  I know I'll have to take that approach, or something like it, eventually.

Mark

[rv6]

Hi Mark,

I have had good experience with ADS and feedback from the developer in Belgium - As you can see on the web site he also have validation study for a couple of aircrafts and information about the underlaying math.

Have you seen the design series that was written many years ago in EAA ?  It also had a Excel sheet build up which was great to follow as you build up the formulas .. Gives you a better understanding of what is going on .. than just plugging in numbers and see what drops out ... :-).

[Mark Waldron]

aviator,
   Regarding the EAA design series--I have read (and printed for future reference) the series in EAAs "Sport Aviation" written by John Roncz in 1990--including the old Lotus 1-2-3 spreadsheet entries.  I need to go back and review that info with my eye on this particular project--thanks for the reminder.  I also found "Aircraft Design" by Richard Hiscocks to be a useful guide (though he clearly l takes steps to minimize the math). 
  Thanks for the info on ADS.  I'll plow into it later and get a better understanding of what it offers.

Mark

[Brent Robbins]

"Hopefully VSP will inspire more aerospace tools programmers to go open source…"

I hope many do go open source, but I doubt OpenVSP will inspire them.  VSP was funded by NASA, and OpenVSP is *still* funded by Nasa.  Rob and the developers aren't working for free.  Haha.

I'd release my software to the public for free too if I got government funding.  :-D

Brent

 

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From: Nelson Brown <nelson...@gmail.com>
To: ope...@googlegroups.com
Sent: Tuesday, January 6, 2015 10:15 AM
Subject: Re: [OpenVSP] Is VSP right for my project?

[Rob McDonald]

Brent,

While I agree with where you're coming from, I don't think it is at
all that simple.

The economics of Open Source are different. That difference has been
making substantial waves throughout the software industry for some
time. I think it is clear that most of those projects are not
government funded.

In a large organization, it is seldom the developer who gets to make a
decision whether and how to distribute a program.

If you take something like CFD, Aerospace companies used to do a lot
of in-house development. Today, they've mostly moved to using COTS or
government developed tools. Those are complex decisions, but one
thing you may lose is the ability to modify tools for highly
specialized needs.

I think we will see cases where companies choose to contribute to open
source tools rather than develop their own or rely on an external
vendor. Open source is a different model between those options.
Sometimes the open source project will start because the company
decides to release what they have internally. CFD has wide
applicability beyond Aerospace, but there are lots of tools that
Aerospace companies develop that won't ever spur a software industry
to provide COTS tools.

For small businesses, I think we will see cases where the hassle of
marketing, selling, and supporting a program are not worth it.
Instead, an open source model may get their tools into more hands --
and that increased exposure may drive their other core businesses.

I think open source is a great model for a lot of things -- but I
think everybody out there is in the best position to choose their own
model.

Rob

[Karén Melikov]

This will sound silly, but MS Excel is a good tool for working on aircraft design. So is MATLAB. Writing code for the latter is simple.

Cheers.

понедельник, 5 января 2015 г., 21:30:48 UTC-5 пользователь Mark Waldron написал:

[Jim Baker]

Based on this comment:

"OpenVSP will help you with #1 and 2 (if you have Vorlax)."

How does one go about getting Vorlax? I poked around on the web a bit and it seems that if you once had it you are okay, but can't get it now, is that right?

thanks,

Jim

[Rob McDonald]

On Saturday, February 7, 2015 at 7:04:07 AM UTC-8, Jim Baker wrote:

Based on this comment:

"OpenVSP will help you with #1 and 2 (if you have Vorlax)."

How does one go about getting Vorlax? I poked around on the web a bit and it seems that if you once had it you are okay, but can't get it now, is that right?

thanks,

Jim

That is pretty much correct.

However, some people have been working very hard behind the scenes and hopefully we'll have a solution soon that is much better than Vorlax anyway....

Rob

[Erik Olson]

Another alternative to Vorlax is AVL, an open-source vortex lattice code. The "plate" model in the degenerate geometry export file should give you most of the information you need to write an AVL geometry file.

[Jim Baker]

Do you have any idea of a time frame? I really could be making use of Vorlax right now if I had access to it. It probably violates the terms of service for anyone else to supply it to me as well.

Jim 

 

[Karén Melikov]

I can supply a short tutorial and sample AVL input files if needed.

воскресенье, 8 февраля 2015 г., 22:58:08 UTC-5 пользователь Erik Olson написал:

[Rob McDonald]

On Mon, Feb 9, 2015 at 12:28 PM, Jim Baker <162j...@gmail.com> wrote:
>
> Do you have any idea of a time frame? I really could be making use of Vorlax
> right now if I had access to it. It probably violates the terms of service
> for anyone else to supply it to me as well.
> Jim

I don't have a specific timeframe for the release of the new project.
However, my hopes/expectations are that it will be measured in weeks
rather than months.

Rob