Re: COX .020 POWERED SPEEDSTER

1/2A Nut Sat Nov 02, 2024 1:00 am

I use to do swept tipped rounded flying surfaces, looks cool and appears fast just standing still.
Thru many Nano versions my understanding and approach for max speed changed.

Field tested noted improved performance:
Formed true airfoils for all flying surfaces, vertical stab included to obtain premium control and
function for the given surface area goals and to decrease R values.

Fully sculpting the balsa is an absolute must, I start with SIG airfoiled balsa for the wing.
3in and 4in wide planks depending on the engine displacement mod to semi or fully symmetrical.

Matching left and right moderate tapered leading edges to avoid surface trim corrections.
*** no swept tips as it reduces total leading edge drag and sharp squared off surface tips.
Leave it to gain longer narrow surface spans for improved lift and control - like gliders.

Gradual small surface control deflections to avoid abrupt drag angles from narrow
strip ailerons and elevators. Proper size surface control horns to achieve low drag.

Minimal firewall and air voids within the fuselage designed around the proper sized components / wires.

Example:

COX .020 POWERED SPEEDSTER - Page 4 Imag9029

TD ABUSER Sat Nov 02, 2024 1:59 am

1/2A Nut wrote:I use to do swept tipped rounded flying surfaces, looks cool and appears fast just standing still.
Thru many Nano versions my understanding and approach for max speed changed.

That's a nice, clean and simple design there..!
I found a few sheet balsa wings in the attic that might be worth trying with the .020 fuselage that I'm running now.
Leaving the tips squared off works for me... Smile

1/2A Nut Sat Nov 02, 2024 5:21 am

NANO X Cox Tee Dee .051 / APC cut to 4.3 x 5.5N
Static 21,962 rpm / 7.2oz thrust / 115 mph prop pitch speed
.144 hp - 108w
25" span 75 sq. in. wing / 8oz - 226g RTF
Loading basically 2.1g per watt

For TD .020 will do well reduced to 45" Sq. In. aka 60%
70% 52.5 sq in will land with ease.

Nano flown 122 mph TD .020
3ch with throttle 119g - 4.2oz / 119.07g RTF / 19.5" Span
43" Sq. In.

3.4 x 4.5 Prop Static 23,192 rpm / 99 mph pitch speed 3oz thrust / .052hp / 39w
Loading basically 3.05g per watt
A lower weight 2ch perhaps 2.4g per watt.

Small Cox Logo

getback Sat Nov 02, 2024 6:12 am

I had to look that up I guess i was thinking something diff.>>

COX .020 POWERED SPEEDSTER - Page 4 Washou10

I have some of that in my wings its call a twist lol!

TD ABUSER Sun Nov 03, 2024 12:50 pm

I found an old [and brittle] .049 Speed Wing in the attic and cut it down to 20 inch span.
Same span as the original wing but about 12 more sq inches of chord and this one is more of a "Clark Y" airfoil instead of fully symmetrical [like the red wing is].

For the first engine start of the day the nitrile balloon tank leaked....so I substituted it with a high pressure bladder.
The COX needle did a fine job of controlling the mixture.
The plane flies so much better now.
There was no stall until the plane was at 2 mph and 1 foot from touch down, then the port side wing panel would drop [into the soft, cushiony grass]. This could be corrected by laterally balancing the plane [from side to side].
The plane is a Pussy Cat to fly now and and very stable while doing long and low "speed passes"...so 1/2A Nut did his homework well with the 14 inch fuselage length from firewall to elevator hinge line.
Next move for me is to build a more streamlined fuselage out of 1/64" and 1/32" plywood and of course make a new wing...then move up to 3 pitch props.
BTW....that yellow wing is next to invisible in the gray sky.

COX .020 POWERED SPEEDSTER - Page 4 Img_0730

rdw777 Sun Nov 03, 2024 1:57 pm

That’s great TD, That’s what you built it for Thumbs Up

…. I like that you’re not afraid to cut into them if something isn’t just right….Cosmetics can come later once it’s performing…. Sounds like it’s very predictable now…Just curious, Do you have to feed in any down elevator with the new wing when it’s at speed?…..I like yellow/red for visibility on small planes….. Sometimes one shows better than the other depending on the light IMO…..

TD ABUSER Sun Nov 03, 2024 2:09 pm

rdw777 wrote:…. Sounds like it’s very predictable now…Just curious, Do you have to feed in any down elevator with the new wing when it’s at speed?

To tell you the truth I didn't take the time this morning to see where the elevator trim is right now.
I DID have to give the plane a few clicks of down trim to make it "hands off"...[but each click is less than a degree of travel]
Remember that the low thrust line is also trying to pitch UP the plane a little.....so I think I'll mount the engine upside down on the next model to raise the thrust line closer to the wing.
Doing so might bring the elevator trim back to zero...?

rdw777 Sun Nov 03, 2024 2:37 pm

I’m sure as everything including thrust line is moved closer to “zero” the less heading trims to be required…That’s the way my pattern types were back in the day…..Your speed wing is probably 1/4” thick or so?…..Even though it’s a lifting section it’s thin enough to go fast but sounds like it really helped low speed handling as well….A few sq inches helped too Thumbs Up

TD ABUSER Sun Nov 03, 2024 3:04 pm

rdw777 wrote:I’m sure as everything including thrust line is moved closer to “zero” the less heading trims to be required…That’s the way my pattern types were back in the day…..Your speed wing is probably 1/4” thick or so?…..Even though it’s a lifting section it’s thin enough to go fast but sounds like it really helped low speed handling as well….A few sq inches helped too

There's always an invisible line you can't cross when it comes to stalling the wing.
excessive weight /lack of wing area... incorrect CG...poor airfoil selection, too much aileron acting as spoilers...unseen building errors / misalignments....pilot errors... Mad

TD ABUSER Sun Nov 03, 2024 3:11 pm

TD ABUSER wrote:
rdw777 wrote:I’m sure as everything including thrust line is moved closer to “zero” the less heading trims to be required…That’s the way my pattern types were back in the day…..Your speed wing is probably 1/4” thick or so?…..Even though it’s a lifting section it’s thin enough to go fast but sounds like it really helped low speed handling as well….A few sq inches helped too

There's always an invisible line you can't cross when it comes to stalling the wing.
excessive weight /lack of wing area... incorrect CG...poor airfoil selection, too much aileron acting as spoilers...unseen building errors / misalignments....pilot errors...

Did you build the .049 powered Mach None...?
That was a great flying "pattern type"

1/2A Nut Sun Nov 03, 2024 4:02 pm

Thank you for sharing the field observations, what is the total wing squares and current weight?

Any vid yet Chuck, looking forward to seeing this one flying. RC Plane

Glad you are enjoying TD .020 power, prop design / spec choices lead to impressive 1/4A performance.
From the prop nut back every design choice is a very fun challenge to improve. Making a TD .020 fly a
plane like it has the power of a .049 is shocking to witness for Cox engine lovers.

My first .020 / 3.75x3P flight amazed me at the jump in performance 92mph pass. Prop to plane matching is everything!
Prior Cox 4Dx2.5P more mass thicker airfoil wider blades. Many props since then max rpm thus far with a TD .020:
Carbon 3x3 Prop / Best Noted Static Peak 32k rpm / 91 mph pitch speed / 3.6oz thrust.058hp / 43.3w /
Flight unloaded to 38,600 rpm / 110 mph down wind pass lots of screaming but not ideal.. ok with a .010 displacement.
Best prop loading with a TD .020 speed ship has been realized as a HQ carbon blend cut 3.8x4.5N thus far / 122 mph
Narrow blades have opened up the use of more pitch while maintaining good diameter for blistering speed with thrust.

First 3ch flight test with a 3.75x3E
E-Flite EFLUP037503 3.75x3 Prop: UM F-27Q Stryker best price $3.99
Prop hub dia is ideal low weight thin blade the 3P perfect requires no mods great thrust.
The APC drone props are better for N mods top / speeds.

Lil Speedy 66sq, in wing overkill for top speed but easy landings and acro.
Made 84mph later needle tweak to 92mph pass with stock E-Flite prop!

Small Cox Logo

TD ABUSER Sun Nov 03, 2024 6:38 pm

1/2A Nut wrote:Thank you for sharing the field observations, what is the total wing squares and current weight?

That Little Sucker is fast..!
Where I'm going to draw the line is with frequent engine failures.
I've been down that road with TD .049s and Norvel AMEs.
Coffee cans full of worn out junk to show for all of those "bargain priced" engines.
Hopefully the .020 TD is going to hold up to abuse better than the .049.
That's why for the past 20 plus years I've only needed to own 2 Cyclon .061s and have gotten 100s of trouble free runs out of both of them.
Propping them conservatively with nothing but the 4.2 x 4 the engine has never been over worked by more aggressive prop choices.
My first Cyclon might still be a "runner" but I lost it when the firewall ripped away from a sheet wing racer, so I bought the one I have today direct from Cyclon.
The fuselage I flew this morning was the one that sat out in the rain for a week, plus I fuel soaked it this morning so I built a new fuselage today out of 1/32 and 1/64 plywood.
The wing I used today [the yellow one] has 3.5 inch root and about 2.25 inch tips...20 inch span so it is about 50 sq inches.
The model weighed about 5.75 ounces dripping wet.
The new model should be a little bit lighter and with less drag from the fuselage.
The important thing is to get the plane dialed in..then I'll play around with modifying props

COX .020 POWERED SPEEDSTER - Page 4 Img_0731

COX .020 POWERED SPEEDSTER - Page 4 Img_0732

1/2A Nut Sun Nov 03, 2024 8:51 pm

Thank you Chuck great first flight with 3P!
How well do you think the oil will soak the crank case and drive shaft with the engine inverted?
That and cooling to include fuel flow / running consistency?
That front end does look good! Perhaps engine cylinder side bevels on the fuselage for airflow.

I would go for a lower weight less wood / firewall and verted engine to insure top speed / cooling.

COX .020 POWERED SPEEDSTER - Page 4 Img_0711

TD ABUSER Sun Nov 03, 2024 9:31 pm

1/2A Nut wrote:Thank you Chuck great first flight with 3P!
How well do you think the oil will soak the crank case and drive shaft with the engine inverted?
That and cooling to include fuel flow / running consistency?
That front end does look good! Perhaps engine cylinder side bevels on the fuselage for airflow.

I would go for a lower weight less wood / firewall and verted engine to insure top speed / cooling.

I don't know what will happen with extended running a .020 with the engine upside down... Shocked

We'll see soon enough...!
Plain bearing engines [like the Fox .35 Stunt] were commonly mounted that way for control line competition models like The Nobler and for any WWII fighter.
I've done it that way with several Cyclon 061 powered planes...including my V Tail Racer and Fora /049 powered Mustang.
I think I have a heat sensor / probe that came with a multimeter that could be used to compare crankcase temperatures.

1/2A Nut Mon Nov 04, 2024 7:46 pm

If you cam snag a aluminum carb body will help with cooling and allow
a tight bond with the NV assembly from migrating loose in the air.
22% castor will help.

Small Cox Logo

TD ABUSER Mon Nov 04, 2024 8:03 pm

1/2A Nut wrote:If you cam snag a aluminum carb body will help with cooling and allow
a tight bond with the NV assembly from migrating loose in the air.
22% castor will help.

I have an aluminum carb body..but haven't taken the time to install it.
The fuel I bought recently from Torco was 25% nitro, 18% Klotz, 2% Castor. I added enough castor to bump the percentage up to 25% total oil.
Time was was spent today making a wing for the new plane.
The hardwood I'm keeping to a bare minimum [I think]
I think I'll follow your example and go with the aileron servo arm and linkage exposed to save weight and gain simplicity.

COX .020 POWERED SPEEDSTER - Page 4 Img_0734

1/2A Nut Mon Nov 04, 2024 10:06 pm

Nice speed ship Chuck,

Can recommend none flared tips for those tail feathers as they add drag.
Oil should be great, do you have a socket reset tool? Wing squares?

COX .020 POWERED SPEEDSTER - Page 4 Img_0712

balogh Mon Nov 04, 2024 10:56 pm

If there is an engine with generous crankshaft lubrication, the front rotary TeeDee -all sizes-is one. The fuel enters through the crankshaft port which turns around and wets the crankcase nose on its full internal bearing surface. The short front bearing, while seals sufficiently, allows the passage of a minimal but sufficient amount of castor through it. Whether the engine stands inverted or not does not matter in my opinion. The only chance of killing the crankshaft fit is by an unbalanced prop..I have run many TeeDees in my RC planes, sizes 010 up to 09, and can only talk in superlatives about all...the simplest yet strongest and most durable COX engines. Particularly the old stock thin wall and stepped wall cylinders with taper bore.

TD ABUSER Mon Nov 04, 2024 11:44 pm

1/2A Nut wrote:Nice speed ship Chuck,

Can recommend none flared tips for those tail feathers as they add drag.
Oil should be great, do you have a socket reset tool? Wing squares?

I think 25% oil allows for more aggressive needle settings.

I do believe I have a ball socket tool for .020.
I sure would hate to have to try making one if I don't...!
This wing will have less rounding at the tips than the yellow wing..so 52 sq inches should be a pretty accurate figure.
I sure would like to come up with a gapless "skin" hinge for the elevons.
I read about someone using a dryer sheet...but have no idea how it was installed.
If you did it wrong it would be a floppy mess and of course all ideas like that carry a certain amount of weight.

TD ABUSER Mon Nov 04, 2024 11:57 pm

balogh wrote:If there is an engine with generous crankshaft lubrication, the front rotary TeeDee -all sizes-is one. The fuel enters through the crankshaft port which turns around and wets the crankcase nose on its full internal bearing surface. The short front bearing, while seals sufficiently, allows the passage of a minimal but sufficient amount of castor through it. Whether the engine stands inverted or not does not matter in my opinion. The only chance of killing the crankshaft fit is by an unbalanced prop..I have run many TeeDees in my RC planes, sizes 010 up to 09, and can only talk in superlatives about all...the simplest yet strongest and most durable COX engines. Particularly the old stock thin wall and stepped wall cylinders with taper bore.

Howdy Balough..!
One little trick I've heard of doing with engines that need more clearance for crankshaft lubrication is to lightly sand the inner portion of the crank journal and just leave the 2 extreme ends of the journal alone.
Early Norvel AMEs needed this done to them.

1/2A Nut Tue Nov 05, 2024 12:05 am

I angle the underside of the leading edge of the ailerons use shrink covering the bottom first
folding over the aileron up onto the top surface of the wing working the shrink film to follow
the sanded in angle.. when applying the top sheet of shrink film I have the ailerons in the
down position as the single sheet of covering is applied to yield a gapless hinge line.

COX .020 POWERED SPEEDSTER - Page 4 Imag3512

COX .020 POWERED SPEEDSTER - Page 4 Imag3511

COX .020 POWERED SPEEDSTER - Page 4 Nano_111

TD ABUSER Tue Nov 05, 2024 1:19 am

[quote="1/2A Nut"]I angle the underside of the leading edge of the ailerons use shrink covering the bottom first
folding over the aileron up onto the top surface of the wing working the shrink film to follow
the sanded in angle.. when applying the top sheet of shrink film I have the ailerons in the
down position as the single sheet of covering is applied to yield a gapless hinge line.

[/
I used to be in the habit of covering my planes that way..but had mixed results with the covering loosening in the bevel and becoming loose.
90% of the covering I've ever used was bargain basement Towerkote after Black Baron became hard to get.
I really liked Black Baron.

getback Tue Nov 05, 2024 5:44 am

This guy has a pot full of it > https://www.ebay.com/sch/i.html?item=116230841323&rt=nc&_trksid=p4429486.m3561.l170197&_ssn=miless59
Very Happy

new design is looking good Brad is the speed man!! Very Happy

TD ABUSER Tue Nov 05, 2024 7:10 am

getback wrote:This guy has a pot full of it > https://www.ebay.com/sch/i.html?item=116230841323&rt=nc&_trksid=p4429486.m3561.l170197&_ssn=miless59
new design is looking good Brad is the speed man!!

It's amazing how many rolls of iron on film he's got that date back so many years..!
I think Pactra Solar film was before my time...?

getback Tue Nov 05, 2024 7:34 am

My monakote is at least 40 years old and still good (well it was last time ) This Site Rocks!

Sponsored content