Min-E-Chili Breeze 30" span...rocket!

[Frank v B]

While staring at the ceiling (remember, I am bored to tears during re-hab from knee surgery) and reading one of Simon Chapman's British model magazines got an idea that won't go away.

Build a 30" span version of the 1993 free RCM&E plans for the 48" span, .25 size Chili Breeze.
The Chili Breeze was an amazing pattern airplane with a ball-bearing .25 OS in it.  It was the first plane that had a 200' vertical from takeoff.  It weighed just below 3 pounds.
I have built 4 so far:
- 48" span per plan with an OS 25 ballbearing- The photo shows this plane at TEMAC after putting in a 400 watt electric motor.
- 43" span (90%) with an OS .25 ballbearing to get more power for the weight.
- 54" span (115%) with an OS .45 ballbearing
- at TEMAC- a 48" span per plan with a Power 25 EF1 motor (800 watts!).  It disintegrated on a low pass at full speed when the radio glitched (full down!).

Plan
- install an E-Flite inrunner 6 on 3 cells with a 6x4 prop.  That puts out about 300 watts. This combo draws 28 amps.

The size makes it a cross between our Nooner Pylon racer (200 watts, 34" span) and the Mini Tarka that I built twice, a 30" bullet but with a shorter fuse. https://outerzone.co.uk/plan_details.asp?ID=10385

Just drew the wing plans to 30" from the 8.5"x11" Outerzone plans.

Frank
ps: before anyone tells me about magnifying printers and printing services.... I am trying to keep busy while not leaving the house.

[Frank v B]

Wing plans are done:

Printed out the plan and magnified everything 2.96 times to get 30" span.

photo 91- plan on an 8.5" x 11" sheet.  All the calculations for  the 30" span size
photo 92- the calculation sheet.  No, I did not use an abacus.  Good thing I have all 10 fingers.
photo 93- the full size wing plan.

Frank

[Frank v B]

..and the full size fuselage and tail feather drawings done.

F.

[Frank v B]

Making the ribs on a double-tapered* wing.

Step 1- make a plywood template of the center and tip rib.
Step 2- collect enough rough cut balsa for each of the ribs Photo 80
Step 3- drill 2 holes through the stack for a tight fit for either piano wire or brass tubing.  Secure with wheel collars. Photo 81
Step 4- I rough cut the ribs with a #11 blade then sanded it with a sanding block.  Total time to carve and sand- 5 minutes.
Step 5- with a razor saw- cut the leading edge, trailing edge and main spar notches. Photo 84

To come:
Step 6- match up rib pairs and trim the larger of the two to match the smaller of the 2 so you have matching ribs.

Go build the wing!

Frank

* Double-tapered means the tip rib is smaller than the root rib in length (chord) and height.

[Frank v B]

How to build a double tapered wing
Building the first wing half

Note: this airfoil is flat-bottom.

The first two photos are of the trimming the rib pairs the same size.  Number them.

step 1- install leading and trailing edges exactly per plan outline.
step 2- install the root and tip ribs- glue in place.
step 3- install bottom main spar.  Pin in place so it cannot move.
step 4- divide the open bay measurement by 6 to get equal spacing for the 5 other ribs (2 3/8").
step 5- make the ribs to the size of the opening by trimming the leading and trailing as long as the main spar hole stays in line with the spar.
step 6- glue top main spar in place. Put a weight on it.

Let it cure over dinner.

Frank

[Frank v B]

Second wing half.

I build the second half off the first half (Photo 92).  The first half has been propped up 1" to handle the dihedral angle (Photo 89).
This way there is no problem matching up the leading and trailing edges and the dihedral angle.
Everything butts up perfectly at the center rib. Photo 90 is of wing after the assembly.

F.

[Gregor77]

NICE CLAMPS!

[Frank v B]

Gregor,

The clamps are Tomato clamps from Dollarama.  They are perfect for balsa because they do not crush it.  A dozen for about $1.50.  There are two sizes.  The only mod- cut off the two nubs on the pads since they will poke into the balsa.

Frank

[Frank v B]

sheeting one half of the wing.

Note it is pinned down while the glue dries so it will not develop a warp.

F.

[Frank v B]

Port* wing top sheeting

Did the same to the *left wing half top.

Wanted to do the bottom sheeting of the right wing half first but then I realized:
1) it would not lay flat at the root when doing the left wing.
2) I still have to install the dihedral brace.  I do this by cutting into the bottom ribs and installing it.  Only then can it be sheeted.  Note: this wing has sweep in the main spar per the leading edge so you cannot just glue the dihedral brace to the back of the main spar.  You will see soon.

Notice how nothing at the tip lines up (spar, LE, TE, sheeting).  See last photo 78

I learned a loooong time ago to trim it with a saw at the end. 
1) it allows me to pin the spars in place outside of the tip rib.
2) A single saw cut takes the place of many measurements.  Cutting each one the right length takes much more time than one cut, one wrong measurement and getting the balsa stretcher out

Frank

[Frank v B]

Adding the dihedral brace.

Used a saw to cut the slots. The brace is out of hard balsa.  The finished wing will have fibreglass in the center section.

Not visible are the shearwebs* added to the 4 affected bays.

Frank

* vertical grain pieces between the upper and lower spars.  Out of 1/16" balsa.

[GuyOReilly]

@Frank v B this dihedral brace looks a bit on the short side.
Should it not extend to another rib for more rigidity?
I really like this method of adding the brace, worked fine in the Spitfire to add the L/G.
Have a great building day!

[Frank v B]

Guy,

Your comment "this dihedral brace looks a bit on the short side. Should it not extend to another rib for more rigidity?"  is true if this plane had landing gear.  it does not.  It has poor man's retracts (hand-launch).

Braces should always be staggered to eliminate stress points.  The double spars go full length (10 bays), the shear webs go 4 bays, the dihedral brace goes two plus bays.  It has full leading edge sheeting top and bottom and will be glassed in the fuse area but wider than the fuse.

This is a small plane and by the time it is finished it will be overbuilt...or not.  The first flight will tell.

The ultimate in this is the old SuperSportster 40 kit.  It was a superb flyer.  You built two wing halves, butt glued the centre ribs and glass over top all the way around.  No brace at all.  I did not believe it but it held for 100 flights before I gave it away.

Frank

[Frank v B]

Glassed the center section with 1/2 ounce cloth and 5 minute epoxy.

This wing will be strong!
installed the ailerons as well.

Sanded, filled and ready to be covered.  Now the fuselage.

F.

[Frank v B]

Da Fuse!

Cut the fuse out of 3/32 balsa.  Yes, Guy, a port and starboard side....I triple-checked.

Added:
- 1/64 plywood doubler for the front half of the fuse. This paper thin plywood (cut with scissors!) and epoxy makes balsa bullet-proof.
- tri-stock at the lower front.  Triangular stock allows the corners to be sanded round.
- 3/16 square balsa at the top for rigidity and to help glue the angled top half.
- cut out the formers from 3/16 balsa.

Note the second photo.  Proof that a pattern-type plane has a length equal to span.  Added at the front is the prop and spinner.  The rudder hangs fully off the back.

Ready to put it together.

F.