Leading Edge Question
 

I am building a high wing trainer, the name I can't recall right now. Anyway, after assembly of the wing I realize I totally forgot to round the leading edge. Its flat on the bottom then 90 degrees up the front then about a 30 degree slant across the top. Question is what will happen if I leave it as is? I am sure I can just get a bit of curve around it if I have to.

Thanks in advance

GW

RE: Leading Edge Question
 

You need a rounded leading edge otherwise the airflowover the wing will be badly affected and the planewill be difficult to fly.

Sounds like you have a semi symetrical wing - see what shape the plan isshowing and copy it.

I've overheard once a conversation on this topicwhere the guy told the other - quote "boy, you gotta shape 'emleading edge kin of round else the bugs will fly in themflat surface and make them plane heavy - and itwill kin offalland you will crash" unquote.....http://www.rcuniverse.com/forum/js/f...bout_smile.gif

Cheers

RE: Leading Edge Question
 

Take your wing and lay it down with the leading edge just over the edge of the table. then take a piece of sand paper wrapped around a small block of wood & run it accross the face of the leading edge. In no time you will remove the sharp leading edge & you can round it acordingly....Gene

RE: Leading Edge Question
 

I like to shape the leading edge that way to make sure I get a smooth airfoil that blends into the rest of the wing.

Tom

RE: Leading Edge Question
 

I never thought of flying an RC plane with heavy ice accumulation simulation.

If you don't shape the leading edge you'll wish you had about 1.5 seconds into the first flight. Good that you thought to build your plane instead of uncrating an ARF.

Ray W.

RE: Leading Edge Question
 

Nothing will happen that you are in a position to judge any difference.

RE: Leading Edge Question
 

As long as both are the same it will fly. Traverse City has a cherry festival in the summer. I saw a cherry fly. <BIG GRIN> Round disk with no leading edge or air foil, about 1 1/2" thick. The leaves on the back were the elevators and rudders. It had a problem taking off but once in the air it flew. Personally I would take the time to shape the edge.
John

RE: Leading Edge Question
 

Great Planes has some of the best kit manuals. I used to look at them to get ideas for different building techniques. http://www.greatplanes.com/parts/index.html
Airfield models also has great building techniques. http://www.airfieldmodels.com/
Dave Platt has DVDs showing different building techniques. http://daveplattmodels.com/
John

RE: Leading Edge Question
 

A good tool for the task:

http://www3.towerhobbies.com/cgi-bin...?&I=LXK325&P=7

RE: Leading Edge Question
 

GW,

YES, a flat leading edge will make a difference in the way your plane will fly.

I posted a few pics of a wing being built. There is one pic where the leading edge has not been shaped. If left at this stage and not rounded over, when the air meets that square, flat leading edge surface the air passing over the wing would be quite turbulent and not provide the smoothest airflow over the top of the wing which provides the lower pressure on the top of the wing as compared to the bottom (generation of lift). In other words, leaving the leading edge square is preventing the airfoil to do it's job efficiently and effectively.

You did not mention at what stage you're at in building your wing that you are considering not rounding the leading edge. Pictures always help and clear up any conjectured cures and advice.

If the leading edge material of your wing is balsa, it won't take much time with a block plane (or sanding block, 80-grit if you don't have a plane) to bring the leading edge to a rough rounded shape. Use 120-grit sandpaper to bring it to final shape, and then 220-grit to smooth it out.

Congrats on building your trainer.

EJWash

RE: Leading Edge Question
 

Thank you all for the info. I got what I needed and more.

I have another question but it pertains to the firewall, I will post it as another topic.

Thanks again!

RE: Leading Edge Question
 

I got a plane from someone with the wing built the same way. It flew fine. I took the covering off and rounded the leading edge, expecting great things. No noticeable change.

Jim

RE: Leading Edge Question
 

As I wrote in post #6 ___
Nothing will happen that you are in a position to judge any difference.

There is no doubt that efficiency and some better performance is acieved with a properly shaped airfoil but it is another matter to be able to judge and evaluate the difference.

That is what I was referring to.

Better shape the airfoil before covering.

Zor

RE: Leading Edge Question
 

How is that? "nothing will happen" Really?

Why, when "nothing will happen"? You claim "nothing will happen", yet at the same time you claim that "efficiency and some better performance is achieved", yet "nothing will happen"???? You contradict yourself. Why? Have you actually flown a model with a flat leading edge and then flown the same model with the leading edge shaped per the applicable airfoil and compared the results? I can't understand how you can make such a flippant remark unless you've done this. Have you? Yes or no?

EJWash

RE: Leading Edge Question
 

Nothing will happen <span style="font-size: larger"><span style="color: #ff0000">that you are in a position to judge any difference</span></span>.

Ifwe read the full sentence it has a different meaning.

There is a difference existing between the improperly shaped leading edge and one that is proper.

All Imeant is that the gentleman or the lady <span style="font-size: small"><span style="color: #ff0000">is not in a position to judge any difference.

I think all understood quite clearly.

</span><span style="font-size: smaller">One poster also said that he/she could not notice any difference.

End of subject for me.
</span>
<span style="font-size: smaller">Zor

</span>.</span>

RE: Leading Edge Question
 

I don't see why there is so much discussion on this.

It's easy to sand the leading edge. Why not do it ? EJ's pics illustrate how to do it, so just do it.

Your model will perform much better, if you do.

RE: Leading Edge Question
 

Congratulations on deciding to build your plane. You will learn a lot and take pride in your new 'gal'.

Whether it's kit #1 or #100, we have ALL overlooked something at some point. The key is that you discovered it and are willing to take the time to make it right. That's how we learn and progress. Almost anything can be fixed and even if it can't you'll smile to yourself knowing you won't do it again. Just be patient and the next one always comes out better!

As for the leading edge, if you haven't covered the wing, sand it to shape. Will it fly better....yes. But you'll FEEL better about it.
Welcome to kit building!

Augie

RE: Leading Edge Question
 

Just to be clear, I ALWAYS round the leading edges of my wings. Wings are beautiful structures and not doing that would feel offensive to me. But the one time I flew a plane without a rounded LE, and then fixed it, I was surprised I couldn't tell the difference when it flew. I'm not saying it would necessarily be true of all types, or under all conditions...I'm reporting what I observed in this one instance. If it meant stripping off the covering and re-covering, on a trainer type, I wouldn't bother. But re-reading the original post, I see that it was not covered at that point, so yes, I agree, round the LE.

Jim

RE: Leading Edge Question
 

Hello Jim and all readers,

Quoting from the first post ___
<span style="color: #339966">Its flat on the bottom then 90 degrees up the front then about a 30 degree slant across the top.
</span>Unquote.

This shape is not far off from being close to a fully sanded and rounded cross section of a leading edge.

Perhaps few modelers realize that the air separation at the leading edge of a wing takes place NOT at the very leading edge but some distance ahead. Even a nicely sanded and rounded leading edge has a fair part of its curvature just about 90 degrees with the flight trajectory.

Looking at the airfoil countour at the leading edge the forward point of the chord is where the leading edge present a surface that is 90 degrees with the trajectory and that is pretty well true above and below that point for up to 45 degrees above and below that chord point.

It is a gradual change until the flight trajectory line become tangent to the top camber of the airfoil.

So it is not surprising that any effect of a leading edge as described in the first post of this thread is not really noticeable on its flight characteristics.

Anyone claiming a big difference or even any noticeable difference can keep on dreaming or spend a bit more time studying aerodynamics.

One aspect of this hobby is to build beautiful models with full details as a show piece and not fly them.
I build model to fly and fly them. If I crash, and I do at times, there is usually little damage and they get fixed and fly again.

Build it, glue it properly, cover it with tear resistant finish, go fly and enjoy.

Zor.

RE: Leading Edge Question
 

Round LE makes the transfer of air from the bottom surface to the top surface smoother.
Is in that critical area where the acceleration of the upper air flow happens from zero (at the stagnation or separation point below the LE) to maximum speed (area of lowest pressure) on the forward portion of the upper surface of the wing.
This is more pronounced as the AOA increases, reaching a max just before stall.

A foamy with flat wings has perfectly square LE and still flies.
However, proper streamlined airfoils are more efficient regarding lift/drag.

Check this video out:

http://www.youtube.com/watch?v=6UlsArvbTeo