skeeter_ca

I have a squared edge on the leading edge of my elevator. It needs to be sanded to a beveled edge. If i just sand it by hand it ends wavy. I remember seeing some kind of tip awhile ago on how to make a jig to sand it accruately. What is a good way to do this?

skeeter

Laird SS

Have you considered using a razor plane or a block plane? Place the piece you want to bevel at the edge of a table or counter and plane one side then turn it over and do the other side.

flyngfrog

After using the razor plane you can sand finish using a block under the sanding paper.

beepee

I ripped a guide out of a 2x4 on my table saw at 30 deg from vertical. Set my elevator half and rudder on it to help me get a straight consistent bevel.

Have fun!

Bedford

epr3

I use a 2ft T bar sander, first I mark a center line and lines where I want to bevel to finish on the control surface

Edwin

My Feedback: (2)

I'm pretty close to what epr3 does. Make the marks, but I free hand with a 6" sanding bar. Has always worked for me. Just takes practice.
Edwin

DavidAgar

My Feedback: (108)

Great Planes makes a 12 inch sanding bar that has a couple of rounded leading edge sanding guides built into it. I use mine all the time. Good Luck, Dave

bullseye000

About 3/4 of the way down the page is a snarky sanding block that makes sanding control surface bevels a snap. I made a couple of different lengths and use a cut 1" sanding belt for the long block. Works great.


[link=http://www.airfieldmodels.com/information_source/model_building_tools/sanding_blocks.htm]Bevel sanding block[/link]

skeeter_ca

Thanks Bullseye, that recommendation is right on target of what i was looking for (pun intended). lol Also that page has alot of ideas on sanding blocks.

skeeter

KitBuilder

I just 3m spray sandpaper on the back of an 18" or block. Place the piece needing sanding at the edge of your bench such that the ruler can reston the bench corner and you angle as needed. couple minutes and your done. I have the great planes sanding bar deal with round and angled lengthwise shapes but found you need to continually clean out (blow) the dust out of the channels your using.

GREG DOE

I strongly recommend learning the following technique to insert 1/64" plywood in the leading edge,
and trailing edge. There are different ways to slot the square surfaces, but the one I like bests,
involves a dedicated slotting tool for the specific thickness wood you are using. I have 3 tools:
one for 3/16", 1/4", and 3/8". I've used them numerous times over the last 30 years, and they
are as good as the day I made them. Each tool has a x-acto blade made into it. The tool is "U"
shaped, with the x-acto imbedded in the bottom of the "U". In practice the tool is slipped over
the edge of the un-sanded stab, or rudder, and slid around the part resulting in a slot exactely
in the middle of the square edge. The slot should be between 3/16" to 1/4' deep. Next take a
piece of 1/64' plywood and sand one edge of it sharp. Now slice off a 3/16" (or 1/4") strip. The
plywood strip gets pressed in, and glued in the slot. Finally comes the easy part. Using a wood
plane, or a sanding block shape each side by removing the soft balsa up to the hard plywood.
The plywood insert does a couple of things: it gives you a perfectly centered dead straight hard
point to shape to, and a very durable edge. I don't recommend gluing the plywood strips in with
CA glue, because if the glue doesn't pennetrate all the way to the inner most edge of the plywood
strips, the balsa in that area will "puff out", and create finishing problems. This technique has been
used for at least the last 30 to 35 years, and kits like the Prather Tony's and many others were
built this way. Another use for the slotting tool is to make "pilot" hinge slots for traditional type
hinges that are centered in surfaces. Good luck, Greg

Bax

My Feedback: (11)

Here you go. It has the bevel built in so that you can make an accurate one:

http://www.greatplanes.com/accys/gpmr6190.html

This can be ordered through any hobby retailer who sells Great Planes kits and accessories.

GREG DOE

Bill, Your tool is excellent for wings, where a radius is desirable. This inquiry was about
elevators, where a sharp leading, and trailing edge (for racing) is desired. Greg

KitBuilder

In the pic of the tool.. you'll notice the V groove... thats for making the leading edge you need.. Mine has two different angles of V.. one larg and one smaller.

kenh3497

I may be wrong so if somebody has more knowledge than me, pipe up please.

I was under the impression that the leading edge did not contribute to drag nearly as much as the trailing edge does. This is the reason leading edges on wings are never "razor' sharp. Something about making the wing stall easier or making it "pitch sensitive" or something like that. However having the trailing edge as sharp as possible was better.

KitBuilder

The more blunt (round) the leading edge.. the more stall resistant and more drag. Higher angles of attach allow the air to still flow along the top of the wing and not seperate. Fighter jets "generally" have quite sharp leading edges.

beepee

Just remember the OP opened with the subject of elevator leading edge. Talking about wing leading edge is a different kettle of fish.

Bedford

8KCAB

My Feedback: (1)

For my PT-20, I marked  a centerline on the edge and a bevel-to line on the top and bottom of 

jaka

Hi!
I just sand it by hand...
I use a Aluminum U-bar, 30cm long on which a "Sandvik" steel sander plate is contact glued on

GREG DOE

Skeeter. Back to the origional question, and answere. If you haven't seen it yet, go to the
"Hurrikane Build Thread" in the 'Q-500 Racing Section' and check out the slotting tool, and
the treatment for the stabilizer. Racers have been doing this to their stabs and rudders for
40 plus years.
We could wright a book on what's happening with wings, and stabilizers at high angles of
attack, but were going to keep it simple. Also we are discussing conventional airplanes,
not duration freeflight, or 3D stuff: pylon racers is the topic at hand.
Think about what happens if you hold an arrow, a few inches from the tip, out the window
of your car. The feathers on the end of the arrow want to take the path of least resistance,
so they end up parrallel to the slip stream. On a conventional airplane, with the center of lift
slightely behind the center of gravity, the stab is trying to assume the path of least
resistance, but in order to keep the nose from diving, we have to incorporate some down
force at the tail. Most of the time we think and talk about the nose of the airplane climbing,
or diving, but actually the tail is going DOWN or UP, and the fuselage is rotating about the
center of gravity, so that moves the nose up and down. Now if we apply excessive elevator
inputs we can force the wing to change direction at such a high angle of attack, that the wing
will stall. Sharp leading edge WINGS will stall much sooner than blunt, (rounded) wings.
The leading edge of the stab, (or rudder) is rarely subjected to such high angles of attack,
that it would stall, and certainly not in our application on a Quickie, or other race airplanes.
I hope this helps explane why sharpe leading edges on stabs and rudders are good design
practice. And as stated, the 1/64" plywood inserts make the leading, and trailing edges very
good at resisting dings, and "hangar rash". Greg

maukaonyx

I do what some others are suggesting...use a razor plane and go slow at it. Then use a sanding block. Make sure you are resting your aileron, elevator, or rudder on a very flat and smooth surface. NOW, here is my tip...use double stick tape (cellophane, not foam) and in a few places on the elevator, apply 1" strips to the wood, close to the LE. Stick the elevator down right on the edge of your smooth surface so that you can sand it without the razor plane or sanding block hitting the table. Flip the elevator and do the other side. This frees up both hands and really helps to get a consistent bevel on the LE. Hope that works out to be as helpful to you as it has been for me! Jon

DustBen

My Feedback: (3)

Sanding is an art form.  It's an integral aspect of real building (not ARF assembly).

Beveling and rounding leading edges is tedious, requires precision, and either yields uniform results or horrible messes.
After building 300 models, I have gotten to the point where I do most of it by hand.

I use a 12" block, 2" wide,  by 3/4" thick.

But, If I have many long pieces of aileron, elevator, stabs and rudders to do (or building multiple airplanes at once and have dozens of edges to work), I'll set up a 45 degree router bit in my drill press and using a guide fence, take a "first pass" cut. This establishes a uniform line to then "work to". From this first bevel, a few swipes with 50 grit gets most everything formed and ready for finish sanding

Perhaps most critical of all is the selection of sand papers. Using too fine of paper early in the "forming" stage allow softer grains to be eroded while stiffer ones remain. However, it is obvious that one extra stroke with a heavy grit can quickly take off too much. Patience at this exact moment renders results you have to live with for the life of the model.

Sanding is a challenge but one of the most important techniques in building. Just have to learn what works, and get really good at it.

Oh... now that I am done here, I am heading back to the shop to shape a leading edge to a wing from a 1/2" x 1-1/4" chunk into an ever changing radius. It'll take me a few minutes... step by step.

DustBen

My Feedback: (3)

Sharper leading edges will stall at much slower speeds than more rounded leading edges.
But... The sharper angle leading edge will break laminar flow at shallower angles of attack than a more rounded edge.

It's a tradeoff; the increased lift and slower stall speed of the sharper leading edge versus the more rounded leading edge creating less lift that can withstand more angle of attack.

DustBen

My Feedback: (3)

Do keep in mind that anytime you want, any nylon bolt can be transformed from head style to another.

In other words, if you want the fastener you show above to be an allen key socket head, warm up the allen wrench, and carefully insert/melt a socket into the top of the screw.

Sooner or later, you're going to break a nylon screw head off, and then appreciate how easy it is to insert a hot allen wrench or common bladed screwdriver into the stub.

Tarasdad

I'm in the process of sanding the bevel on the ailerons for my Tiger 60. Earlier I was sitting here thinking about how I could set up a disc or spindle sander to do the job. Moot point, since I don't have either one![sm=angry.gif]