Easy way to put and edge on the elev / flaps hinge

[Paul Taylor]

What is an easy way to put the bevel in the elevator / stabilizer for the Hinge?
I know some use two steel rods, but I don’t have any. I bought one of the Great Planes sanders that has the three different edges, but the one that has the sharp edge is more for LE and not TE.
Need some ideas.
Pictures would be great.


Paul 

[wmiii]

 I have done just the leading edges, works fine.

 Walter

[Wynn Robins]

Paul.
leave them square - there is no reason to make them taper - other then the miniscule weight saving, and the way they look
 For the hingeline - the way I do it is buy some triangle stock - cut the LE back the same width as the triangle - then glue that on the front - make for a perfect 45 degree angle on to and bottom.....I have pics somewhere......

[Warren Wagner]

What is an easy way to put the bevel in the elevator / stabilizer for the Hinge?
I know some use two steel rods, but I don’t have any. I bought one of the Great Planes sanders that has the three different edges, but the one that has the sharp edge is more for LE and not TE.
Need some ideas.
Pictures would be great.


Paul 

Hi Paul,

I'm not clear as to exactly what your question is.  Are you talking about *tapering*  an elevator (or flap) surface using pairs of metal rods, or are you talking about putting a *bevel* on leading edge of an elevator (or flap) to allow clearance for the surface to move at the hinge line.

Please clarify your question, and then we will know which direction to go.  Like most other things in modeling, including flying, it's easy when you know the right techniques.

Cheers.

Warren Wagner

[Larry Cunningham]

With all due respect to those who don't do it, I believe flaps and elevators should
be tapered, with a 90 degree angled leading edge, and slightly rounded or rounded
trailing edge.

The rod method works quite well, and the music wire rods are not that hard to find.
You can usually find them at a local hobby shop, often in hardware stores, and certainly
by order from the internet. You can get it in increments of diameter of 1/64" from Brodak.
Here is a link:

http://www.brodak.com/shop_search.php?pageNum_SearchResults=1&totalRows_SearchResults=20&productsearch=music+wire

Buy wire diameters for the leading edge size (e.g. 1/4"), the finished trailing edge size (e.g. 1/8") and the size
intermediate to them (e.g. 1/4" + 1/8" = 3/8" divided by two = 3/16"). By sanding the taper in two steps, on
both sides, the symmetry is properly maintained, and the rod method works well even with flaps and elevators
having rounded perimeter contours. It is simply not that much of a task, and well worthwhile considering the
results, and the finished appearance.

(I first read about the rod method in a Ted Fancher column, and haven't strayed from it since.)

I'm showing the cantakerous side of my aging mentality here, but when I see flaps and elevators left flat, untapered,
I think to myself that the builder is simply lazy..

I've heard the arguments that untapered moving control surfaces work the same as tapered ones, but considering
just how sensitive these flight surfaces are to things (e.g. taping the hinge gap makes a serious difference!), I cannot
believe that they are equivalent. JMNSHO, possibly wrong. I'm an old man, so..

That said, I'll refer you to a Stunt News construction article by Joe Adamusko, on his "Stuntress" which has beautiful
elliptical wings and stab, with a lot of curvature on the trailing edges. He did something very clever, a good variation
of the rod method for tapering the flaps and elevators. He made up a sanding jig using square brass rod stock, bent
to fit the trailing edge. Awesome approach, IMO, and the Stuntress is absolutely gorgeous. IMO, that ship would have
looked incomplete without its flap and elevators tapered.

Cunningham Goes Off On quasi-rant complete.

Good luck to you!

L.

"Fear nothing, for every renewed effort raises all former failures into lessons, all sins
into experiences." -Katherine Tingley

[Ted Fancher]

With all due respect to those who don't do it, I believe flaps and elevators should
be tapered ...

SNIP

See, Larry.  I knew we'd find something to agree on before the year was out! 

Happy New Year and a healthy one, as well.

Ted Fancher

[RandySmith]

What is an easy way to put the bevel in the elevator / stabilizer for the Hinge?
I know some use two steel rods, but I don’t have any. I bought one of the Great Planes sanders that has the three different edges, but the one that has the sharp edge is more for LE and not TE.
Need some ideas.
Pictures would be great.


Paul 

http://stunthangar.com/tips.htm

HI Paul

Take a look at the Stunt Hangar building tips page   

Randy

http://stunthangar.com/tips.htm

[Paul Taylor]

I'm talking about putting a *bevel* on leading edge of an elevator (or flap) to allow clearance for the surface to move at the hinge line.

Please clarify your question, and then we will know which direction to go.  Like most other things in modeling, including flying, it's easy when you know the right techniques.

Cheers.

Warren Wagner

Thanks Warren for helping me with this one. It is hard to explain the question when you don't know the answer.
I am looking for an easy way to bevel the leading edge of an elevator (or flap) to allow clearance for the surface to move at the hinge line

Thanks
Paul

[Leo Mehl]

I round my hinge line. It works just as well. I also notice Paul Walker does this. I also use  non tapered flaps that are rounded on the trailing edjes. The look just as good when finished and are a little faster when they hit the air stream. Works for me. Good alturnitive and take just as much work as tapering. Also have to knotch for hinges. I don't care if I am lazy.

[Mark Scarborough]

FWIW, I took a peice of Particle board, like shelving material? I ran it through my table saw with the blade set on a 45 degree setting. the board is about 18 X 6 inchs. Then on the beveled side, I stuck a strip of 12o grit paper,( I use sandpaper from the autobody supply shop, its a roll about 2.5 inches wide and has preadhesive backing) Then I trim it flush. Lay the board on your glass table or your bench, the flap lays flat on the bench and you just stroke the board back and forth along the leading edge of the flap until you are sanded to the centerline of the flap. Oh I forgot to mention I mark the centerline of the flap first with a pencil of fine sharpie. Flip the flap over and sand the other side of the leading edge till its down to the centerline as well. Your choice as to whether to sand in the hinge barrel relief first of after. I prefer to do mine first. I will be building my flaps for th 109 soon, I will take some pictures when I do if interested.

[Harleyman]

I do it just like Ty describes above.
Quick and simple.

[Larry Cunningham]

What Ty said. The only thing I would add is that if you have a T-Bar aluminum sanding bar,
you can glue on sandpaper to its top side horizontal and a vertical edge (on the "handle" strip),
and get a very sharp 90 degree corner sander. After the general area is shaped, you can
slowly true the 90 degree corner and get perfect alignment on your V-shaped LE.

L.

"I was born by Caesarean section, but you really can't tell.. except that when I leave
my house, I always go out the window.." -Steven Wright

[Larry Cunningham]

The rounded leading edge is typically combined with a rounded trailing edge where it attaches,
and was very common on older models, with thinner stabs and elevators. For example, the
Roadrunners I saw that Bill Melton built had that setup.

L.

PS - Ted, there is a great deal we "agree" on, I learned almost all my building techniques
and tricks from your columns. As is well known, I steal freely of good ideas, and I've
stolen almost everything you wrote.

The only thing you did that drove me nuts was to "Swiss cheese" your TP cowls so
beautifully.. You know what I'm talking about.. ;-)

PPS - You need to rerun all your articles, perhaps with some updates and revamps.
I know, I know, it's a lot of work!

"I went camping and borrowed a circus tent by mistake. I didn't notice until I got it set
up. People complained because they couldn't see the lake." -Steven Wright

[Leo Mehl]

Rounded Nobler flaps and it flys good without taping hinge line. May be old school but it works.

[steven yampolsky]

Got this tip from Eric Rule of RSM:

If you have a 1/4" flap/elevator, buy 1/4" triangle balsa stick and glue it to the flap leading edge with sigment or any other glue that's easily sandable. You'll get a perfect shape and virtually no sanding.

[Larry Cunningham]

Steven, that would definitely be the Easy Way. Unfortunately, the Cowboy Way is seldom the
Easy Way!

Haven't you figured out that the goal of building the model is to suffer? Either you build and sand
your butt off, or you flog yourself with a bag of balsa sticks.

L.

"Nothing overshadows truth so completely as authority." -Alberti

L.

"Think of this doctrine -- That reasoning beings were created for one another's sake." -Marcus Aurelius Antonius

[L0U CRANE]

First to Larry, and then of course to all: Happy and HEALTHY New Year!

There was a long thread, somewhere, not too long ago arguing mostly FOR a sharp, "vertical" back edge to control surfaces or wings. A bit sophisticated - nah, not really... remember the racing sports-car Abarth Spyders of the 1950's? No, well, how about the Honda CR-Xs with a window in the vertical back end?

An aerodynamicist named (Sidney?) Kamm gets credit for such bob-tail shapes. America's Cup racing yachts don't bring their transoms to a sharp, streamlined point, the extra waterline length needed causes more drag. Rowboats, speedboats, y muchas barcas otras, have the same type of chopped off back end. Even the X-15s didn't bother cleaning it up back there.

So, why? Another scary word: Vortex, or actually more than one. Call them "vortices." Look at the wake of a square-transom speedboat. It flows smoothly aft, past the hull quite a way, then rolls over on itself. (Those are vortices.) The shape of high civil or military jet plane contrails usually make other vortices visible, too.

ALL our wings generate some kind of tip vortex. More pressure under; lower pressure over. Air rolls from high pressure to low pressure when the object in the way ends. ...Like at wingtips.

Rounded ending edges make it easier for the higher pressure air to 'roll' over and blanket part of the lower pressure working area. Reduces effective lifting area, IOW. Sharp trailing edges do very well to delay that rollover until very near the sharp edge, but it WILL occur there. And they are very vulnerable to hangar rash, warping, and other damage...

Enter Prof. Kamm! A sharp cornered, "vertical" back edge - well, call it perpendicular to the chord line of the surface, anyway - lets the airflow pretty much "run past' the structural surface, before it rolls into a vortex, or pair of vortices... That is, after the model's physical pieces have left the room...

As I recall, the discussion implied full effect came with a "vertical" height of around 1% of the total length of the surface. That would be counting the wing AND flap chord, or the stabilizer AND elevator chord... E.g., a 14" chord wing+flap could use a vertical height of 0.14" - a bit over 1/8". And, the edge should be sharp, because air has enough viscosity to 'stick' to a surface it slides over. The sharp edge breaks that off; a rounded edge may encourage it.

Besides, some taper does look better...