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Finding mean aerodynamic chord (mac) and C.G. Graphically. 

By “definition” the aerodynamic wing of an airplane includes the area inside the fuselage whether you have a plug-in or one-piece wing. The “aerodynamic root chord” is always on the centerline of the fuselage. If you have plug-in wings you will have to extend it to the fuselage centerline “on paper” to find the aerodynamic root chord. 

If you have plans use them for this exercise. Note the scale of the drawing and check to be sure of the scale. If plans drawings aren’t available, you will have to measure your wing, fuse thickness, etc then put them on a drawing. If making a new drawing, do it at ¼ or ½ scale. Of course your have to multiply the result by 4 or 2 to get the C.G. location. 

For the following exercise don’t include rounded or swept tips. Draw a line at the tip that is parallel to the root chord for these purposes. 

1. Draw a line connecting the root and tip chords at the 50% points.

2. Draw another line connecting the root and tip chords at the 25% points (or whatever percentage mac that you want to use for the C.G. but somewhere between (25% and 30%).

3. Draw a line equal to the length of the tip chord to the LE of the root chord.

4. Draw a line equal to the length of the root chord to the TE of the tip chord.

5. Connect the ends of the extension lines (3) and (4) with a line.

6. At the point where the diagonal line of (5) crosses the 50% chord line is where the wing mac is located. Draw a line through this point from the LE to the TE. This is your mac (mean aerodynamic chord).

7. Extend a line from the point where the 25% chord line crosses the mac  to the side of the fuselage.

8. Measure forward from this line (7) to the wing LE (parallel to the root chord). This is the distance that you will balance your airplane i.e. the 25%mac C.G. (or whatever percent that you chose).  

Ken Blackwell
Enterprise Alabama

Stuff Your Van

By using a card table, you may easily load two pattern ships, the rest of your stuff and still be able to haul seven passengers at a contest. About the only thing not shown is the ability to keep chargers etc under the seat. By removing the card table, raising the seat, you have your seven passenger capacity. It is necessary to shorten the card table legs to get the proper fit. I also covered the card table with a fine weave carpet so Velcro would stick and hold the planes in place.

Ed Hartley

Pipe Mounting System From Mike McConnville

This is on a Dr. Jekyll II. The system was installed by Bob Rupel and he got the idea from Mike McConnville. It is pretty simple and works great! I now own the plane and as of 08/25/99 have flown it one-hundred and fifty-seven times. It was first flown April of ninety-four. Since he started using this system, Bob has only broken one header. I have not broken any and the one I am flying came with the plane. The mount is a Hyde. The fitting on the end of the mount is a Dave Brown pipe mount with a bundle tie through it.

Ed Hartley

Header FIX!

It works.  Hundreds of flights now on two versions of my own Hyde mount (although this pic is pre-Hyde in plane 1) without a single break.

We have discovered that the key is damping the mass of the pipe/header combo and reducing the lever arm of oscillations/stress along the header length.  This is effectively done with two pipe clamps (we use the AAP type), then the lord-mount stud for the clamp around the header.

The "magic" is to properly mount the header so there is no VERTICAL bending, with only a single bend made to fit - ever - per installation. After once used, if you re-bend any header, they will break at the new stress point.

The header material is 5/8" OD stainless steel appliance tubing purchased at WalMart or HomeDepot or such place.  Cut off the ends.  Use a Dremel cutoff wheel to cut some angular slots about 3/16" long about 4 or 5 places around the forward edge.  This is the area you "crimp" onto the header front piece.   That's the broken Hatori piece you un-brazed the header material from by heating to cherry red with a butane torch.

Clean with a wire brush.   Apply paste silver brazing flux where the new header will crimp.  Cut the new header to approx. length, put the correct J or S bend you need, then crimp over the area you cleaned and fluxed.  You already bought the Sil Foss silver bearing brazing rod from the refrigeration/heating and air supply company.

Hold everything in place rigidly.  Heat the area of the crimp to RED, then apply the rod to flow the area.  There's a technique here, and it takes some practice.   At the other (coupler) end, I fill the coil area for one wrap of the tubing corrugation with SS wire, then fill with brazing rod, grind to shape, then smooth with wheel.  This allows a great seal into the 5/8" Viton™ coupler.

Be sure to leak test the thing before using.  If there is a leak at all, redo the deal.

Not counting the front piece, which you already paid for, the cost per header for this deal is about $7.

Yep.  I'm CHEAP.
Bob Pastorello -  faipatrn@flash.net

Viton™ is a registered trademark of DuPont Dow Elastomers

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Figure 1

Top Access

The biggest problem with top access is deciding to cut into your high dollar fuselage!

Figure 1 shows the completed setup
Figure 2 shows the canopy
Figure 3 another view of the canopy
Figure 4 is a view of the fuse front opening
Figure 5 is a view of the fuse rear opening

How do you do it? I use 1/4" masking tape to mark the fuselage where I will make my cut out. Using a X-ACTO saw blade I carefully cut out the planed area. Next I cut out the wood portion that will go on the fuselage. This is the portion that will go from the firewall to slightly behind the cut out opening. All the wooden parts are cut from a good grade of 1/16" plywood. It is advisable to cut another piece to match this one. Make them the same by sanding etc. A portion of this piece is used to go on the bottom of the canopy. This makes a good match.

Using thin CA, in a few places tack the first piece to the fuselage being sure the original dimensions of the fuselage are maintained. Take the matching piece and lay it over the glued in piece. Align it and mark the front and back of the opening. This will be cut and fitted to the bottom of the canopy to make that  good fit. 

Now cut a piece of wood to go in the front and back of the fuselage opening. Make sure the fit is true! Make two of these. The second ones will go on the canopy. This again is for a good fit. Once you are happy with the fit, tack in a few places with thin CA the ones to the front and back of fuselage in place. 

The canopy pieces are put in place with the bottom first, then the front and back pieces. If you are careful, your fit will be as good or better than the pre-made open top canopy's that come with some kits.

I use two pieces of tubing pointing to the rear on the canopy and two pointing down on the front. This will align the canopy. I use a Prather latch that must be mounted to the fuselage. I mounted one to the canopy and promptly proceeded to have it come off in flight! Not good! You can see this setup in the pictures.

After you are happy with the placement, fit and such, use GE Silicone II to glue the pieces to the plane and canopy. It Will Hold just fine. A great deal of this stuff is not required. I reach under, around and about to rub it in place with my finger. I use this to mount just about everything to fiber glass, including the firewall.

I am sure you can come up with some improvements to do this project. I use thin pasteboard to make the templates then cut the wood. I then sand the wood and fit and sand and fit until I am satisfied.

Have Fun! Ed Hartley.

Figure 2

Figure 3

Figure 4

Figure 5

Engine Thrust Measurement
Bob Pastorello

An idea for being "sure" you've measured thrust....Go to your local Builders' Square, Payless, Home Depot, etc, and buy a piece of 3/4" angle aluminum stock..1/8" thick stuff.  Cut a length at least 20" long.   Mark the center EXACTLY, then drill VERY carefully a clearance hole for the crankshaft on the 90 degree corner.  

With motor mounted, and spinner back plate installed, place the alum bar with the "point" of the angle facing forward, install a washer and prop nut. Rotate the bar exactly horizontal, measure tips of the bar back to whatever reference point you choose.  This is also helpful for checking wing/stab alignment horizontally, as you can reference up to the horizontal bar.

Rotate 90 degrees to check up/down similarly by measuring back to fuse centerline, stab, whatever.....

This works.  
Bob Pastorello faipatrn@flash.net

A MonoCote Tip
Dick Hanson

I use no adhesives --and no wood peckers--I do fine sand (320 gold #M) with a rubber block and then vacuum/blow all dust and then rub briskly with a dry washcloth and remove the remaining dust--Now--I use TWO irons --one is bare and at full heat --the other is covered with a very fine weave cotton baby sock pulled tight enough to keep any seams off the sole -then tape the sock to the handle to keep it taut. Set the temp on this one down to a point where it will not cause bubbles and will allow firm pressure and a circular rubbing to develop an even shrink that locks the film to the wood. When you are ready to do an edge , or a tip --use the hot iron -again this iron should not be used on the surfaces! practice this a little --you will find that the results stay locked to the wood and do not blister or lift in the summer heat.

Dick Hanson
Dhmodels@concentric.net
5269 Lucky Clover Ln.
Murray, UT 84123
801-261-1402
http://www.concentric.net/~dhmodels/rc.html

YS-NC Muffler Problem!

For about four days, four aborted trips to the field and a headache, one of my NCs' would run wide open for a few seconds and then go into a popping mode. The popping mode, for lack of a better description, was similar to a two stroke four-cycling at about one-third its power. You could pull the power back and immediately apply it, get a few seconds of full power and do the routine all over again. After a plunger assembly, diaphragm, looking at the clearance on the rear rotor, etc. we put a new bullet in and came up with the same problem! The only thing common was the NC muffler. Took it off its extension and found the inside had broken into three pieces. I fished them out, put it back together and it worked just fine, thank you! Soooo if you get this activity using a NC muffler, take a look before you blame it on the engine. EH

Pattern Plane Construction by Sam Turner
2716 Shadecrest Rd., Land O'Lakes, Florida USA 34639
Ph: 813-996-6421 (Fax available) E-Mail: S1Turner@aol.com

Here's a simple trick to make your work a little easier.....
Sam's Measuring Spoons

Tired of trying to find an easy means of measuring small amounts of paint for the airbrush, or small quantities of thin epoxy, I've started making these little "spoons" that make the job as easy as it can get.

Save all your plastic screw-on caps from 2-liter soft drink bottles. Just CA these to the ends of Popsicle sticks with gap-filling CA: Voila! Perfect little measuring "spoons" that cost you virtually nothing, are just the right size for the job, and will keep the mess to a minimum. 

Sam Turner

FUEL TANK SETUP

Ever have a problem with the clunk after a hard landing? This may solve your problem! First solder a piece of tubing to the clunk. Slide a piece of neoprene tubing over the metal tubing. Leave a small amount of space between the movable clunk and the tube leaving the tank. And you are all set! (see insert) Click on the image for a larger view.

THROTTLE LINKAGE

This is the throttle setup I use in my pattern  planes. Use a piece of .047 / .049 inch piano wire as the push rod. Use a piece of the "yellow" (inside) portion of Nyrod. That is the original push rod part, as the carrier. Solder and twist the wire around a chrome clevis as shown in the diagram. This makes the connection solid. You must run the Nyrod through the firewall in a position where the wire lines up on a small angle slightly to the inside of the throttle control arm. If the wire is bent at a ninety degree angle, (drawing) you can see a spring tension will exist if it passed through the control arm. It is a simple matter to set your servo to its center position, (with the radio on), then center the throttle control arm and make a ninety degree bend in the wire. Trim the wire where it just clears the carburetor as it operates.  Now use your computer radio to adjust top - low end positions of the throw. The spring tension alone will hold the wire in position. No need for any gismos to hold the wire on the control arm. The spring tension does that nicely. Quick, simple and works well.
Ed Hartley - - Click on the image for a larger view.

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for a larger view

YS - Tuning
Dhmodels

5269 Lucky Clover Ln. - Murray, UT 84123 801-261-1402

The setup is a Tee in the intake runner which faces directly rearward---this is then attached to a length of light ,thinwall 1/2" dia lightweight silicone rubber tubing --approximately one foot long which has a stopper in it's extreme end.-This simply rests along some portion of the airframe and is tied in place. The YS engine produces a positive pressure in the intake tube when it reaches about 5000 rpm as I recall--the pressure builds quickly at that point and depending on the size of the tube (plenum) will reach approximately 5.5 psi. I have proven that IF the plenum is in the system, a rpm gain of 300 rpm is the minimum boost at approximately 9000rpm.--when the plenum is blocked off the engine looses about 500 rpm--BUT adjusting the fuel mixture produces some recovery --about 200 RPM. Conversely - if the plenum is opened --at that time --the engine will pick up some speed BUT will be running lean and require that the mixture be richened to bring up the maximum power. It also appeared that some further work could cause a mild tuning effect in the setup - I did not continue the tests but simply used the engine in this form for about a year. Very strong runner -- NO problems except that the tube wore a little in the O ring seal areas. I used a quality 5 LB pressure gauge for all tests and am satisfied that the rework was worth doing. The engine was a std big valve engine (preceding the air box design.) IF some rework to the head was done to feed the rocker cover from the Tee and if the head was reworked around the intake valve to allow flow through a series of shaped holes (like on the 1.4 engine -- the engine should breath better yet and even though the measured pressure in the tube would drop, the power (torque) should come up even more -- this is to be my next test setup.

Dick Hanson
Dhmodels@concentric.net