Posts

Washout (twist and shout)

In the last post I covered some topics on analysis.  In this post I want to focus on washout, in this case structural washout sometimes called twist. This can be a tricky subject and one that some builders and manufactures avoid.  I will do my best to describe what washout is and why I chose to include it in my design.

There are 2 types of washout, structural and aerodynamic. Aerodynamic washout refers to the use of several different devices that can accomplish the washout effect without incorporating a structural change to the wing. These include modified airfoil section, vortex generators, leading edge wing fences, notches, or stall strips.  The main purpose of these devices is to reduce airflow along the wing span to reduce the likelihood of a tip stall.  I am going to focus this discussion on structural washout.

Structural Washout I pulled together this diagram to try to explain washout. This discussion will focus also on lifting airfoils, airfoils with a cambered top surface.  St…

Yo, analyze this...

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In my last post I spent some time going over some of my design decisions, which ones were based on engineering reasoning and which ones not so much.  This installment is going to cover some of the analysis I did early on and the application I found for this task.

When I first started talking to Adam about designing a wing he asked me if I was using an aerodynamic analysis software.  It was at that point that I wanted to engineer the shit out of this thing.  I started looking a round for software packages that would give me some insight into how well my design was working.  I first looked at SimScale.  SimScale is a very capable FEA and CFD analysis package that is cloud based.  I have used it in the past to analyze some of my 3D printing designs.  It is a sister company to OnShape, the 3D drafting package I use for my printing designs.  The problem that i ran into is that SimScale is very powerful and it was overkill for this project.  It was just to cumbersome to configure for what I…

If it quacks like a duck...

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In the last post I spent way too much time explaining airfoils and why I selected the one that I did.  Airfoils are important but so are the aspects of plan form, all the other dimensions that make this think look like a wing.  I wish I could say that I had a solid scientific basis for all my dimensions but truth is I don't.  Some of my dimensions are based on the " I like the way it looks" principal.  "Some time you gotta say what the fuck" (are you old enough to name the movie that came from?)  and go for it.  If engineers were the only people that were responsible for most of the things we see and use everyday we would all be driving "boxy" cars and living in boring cookie cutter homes.  There has to be some style in what we create and fly and sometimes there is a compromise between Form and Function.  Life is too short to spend flying ugly wings.



Wingspan I wanted a good sized wing, one that could take some wind and carry some load.  I have a coup…

Airfoil, Airfoil, Airfoil

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The single biggest consideration and the one I spent the most time on was the Airfoil.  The airfoil selection can make or break a design.  There are tons of published airfoils to choose from but there are three basic types: lifting, symmetrical and semi-symmetrical.  Each type of airfoil is designed for a specific requirement.

Aerodynamic design is a game of compromise, you cant get something for nothing.  Every design decision is a balance.  I wanted to see what others designers were using and why.  A symmetrical airfoil is a good choice for a high performance wing such as a race wing.  These types of wings are usually thin and flown fast.  There are several advantages to a symmetrical airfoil.  Symmetrical airfoils are a non-lifting airfoil, meaning their shape doesn't generate lift.  They must generate lift by deflecting the airflow down off of the bottom of the wing.  The generation of lift causes induced drag.  Because the symmetrical airfoil doesn't generate a lot of li…

Any Color You Like So Long As It's Black

I have a couple of race wings and a twin boom pusher and few other airframes in the hanger.  What i was looking for was what I call a 'Sport Cruiser'  A sport cruiser is a wing that can be used as a mid to long range cruiser but is still agile enough to do some proximity and aerobatics with.  Let's breakdown the requirements.  
Flight Time My first consideration was cruising.  I wanted a wing that I could use to do some exploring with.  Something that I could rig with a long range system and use for extended flights.  My flight time goal was 30 - 45 minutes at a reasonable cruising speed.  This is actually a very complicated requirement, it governs a lot of aspects of the design.  One of the most important factors governing flight time is fuel, in this case, mAh.  Battery capacity will dictate the weight of the wing and thus the amount of lift needed.  This will be a big part of the design.
Wingspan I wanted to have a sizable wing.  A larger wing will make it easier to car…

Welcome to the Dark Side

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In my last post I gave a rather long (sorry) account of how I got into FPV and why.  FPV is not a hobby, it is a lifestyle, an addiction as strong as alcohol, weed or gambling.  Why? I think the answer is the same for any addiction, the way it makes you feel. The rush, the release of endorphins that makes your hands shake and stomach flutter.  I am an FPV JUNKIE!

So why fixed wing over multirotors?  The simple answer is that I got a bigger rush from the wings.  I use to think that my hands shook because I was nervous but then I noticed that they shook more when I finished a flight than when I started.  Because I fly alone most of the time and have to self launch I end up having to fly standing.  This is a full body rush, hands shaking and knees knocking all the way.   Race quads are flying bricks.  When you power them up they beat the air into submission and when you cut power they fall out of the sky.  Don't get me wrong, I still love to fly them because you can do anything you …

So Why a Blog?

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So why a blog?  Well, why not.  I love the design-build process and I love flying wings.  This installment will be mainly about how I got into this hobby and why i decided to design and build my own wings.  I decided to write a blog after someone ,Nathan Knight,  asked me if I had one documenting my process.  I didn't, now I do.  Nathan is a very talented scratch builder and you should check him out( Instagram).  This blog is as much for me as it is for whoever reads it.  I need to get this crap out of my head so I can concentrate on the tasks at hand.

A couple of things up front:  This has not been a solitary journey, I have has a lot of help and advice from a lot of people that are considerably smarter than I.  I would like to claim credit for most of what I have done but the truth is that I have stood on the shoulders of giants.  Secondly, I will be pouring my thoughts out here and they are not all pleasant.  I will do my best to keep it PG, but no promises.  I once heard a of…