Mustang Fever

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Getting the covering done, a little at a time. Thought I'd make it look like one of the Avro Arrows of the 1950's. A little more neon orange, tho, as this thing will be hard to see as it is. The nose will be orange, as will the pod and the upper fin.

oceansfiftyseven

Outstanding! Thanks for sharing. Rich

Mustang Fever

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Thanks, Rich.

Here's today's progress. Only the elevons left to cover, then it's install the pushrods and get the balance. The rudder is hinged with UltraCote.

Mustang Fever

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Everything's done except the battery and hull bottom installation. Weight shown here, with 0.062"pushrods and adjustable connectors on the servo arms, is just over 18oz. I was able to balance it with 3 oz of lead near the aft edge of the canopy/hatch, so I ordered the EVO 25 1200 mAh LiPo battery for it, which weighs a bit over 3.5 oz. That's about the smallest battery with sufficient capacity for a 10 minute flight, and a comfortable margin on the max amp draw. RTF weight will (hopefully) be below 25 oz, so the wing loading will be a nice, low 16 oz/square foot or less.

This project started 26 days ago, and she'll fly next week.

Mustang Fever

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This info is also on the big Arrow build thread,

http://www.rcuniverse.com/forum/m_72...tm.htm#8216545

For the CG and control surface throws, I'm dividing everything from the big Arrow in half. Since this is an electric and the CG won't change during fuel burn, I wanted to start off with a simulated "full" tank. The CG on my big Arrow with a full tank is 15 and 1/8" forward of the TE (less elevons). So, the electric will be 7 and 9/16".

Mustang Fever

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After consulting with Ed Anderson on the "EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT" thread, I cut some air inlets on the nacelle on both sides of the motor, and made a scoop inlet with an outlet to funnel air past the battery and the ESC. The back end of the nacelle is already open, so no need to cut holes for air outlet on it.

I realize now that my three Astro 020 systems are 5 years old. One of them died while I was configuring it for the EArrow- probably because I didn't pay much attention to cooling when I had them both in a little P-38.

Mustang Fever

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The battery, horns, and props arrived yesterday, so a bunch of progress.

I used Dubro EZ connectors at the servo ends of the P/Rs, which are just .062 piano wire. At the control surface end, I used Dubro Micro adjustable control horns, so as to get everything lined up real nice. I've use some sort of adjustable control horn on many models, now, and I'm kind of sold on them. I had to drill these out to .062", but there seems to be plenty of material remaining around the hole so strength shouldn't be an issue. To hold the rods into the horns, I used the Dubro mini EZ links that are intended for .062 wire.

The CG required that I cut a hole in the step former, and stick a little bit of the 1200 mAh battery aft of the step. This puts the tail end of the battery about even with the CG. Next step is to put a nice 1/16 ply floor in the top of the battery opening. I'll use velcro to hold the battery in place so I can move it around a little if necessary.

The prop shown is an APC 5.1x4.5E thin electric. It seems the best of the bunch I bought so far, as far as a good combination of top speed and thrust: 19,350 RPM with a somewhat discharged 3S battery. Thrust/HP software says 82mph and 3/4 pound of thrust, but it feels like a lot more. I think this prop design, with it's wide section near the center of the blade arc, generates more thrust than conventional software would indicate.

Tower's sending me some Astro 0 loss connectors for my Whattmeter, as it came with Dean's, which I have no use for. If the meter shows current consumption on the ground at 25A or below, I'll probably go with the 5.1x4.5E.

Last items will be putting the rest of the bottom sheeting on, and making a removable hatch on the bottom for battery access.

Mustang Fever

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She's ready to fly. Final weight hit 24oz on the nose. I'm just doing load/prop testing, and getting used to my first big LiPo battery.

I have a couple of questions that maybe one or more of you watching this can help me with:

My battery is a Flight Power EVO 25, 1200mAh, 3s, and I'm using their cell V-balance cell balancer.

I ran the motor a little bit to get the battery voltage down to about 11.4, and then hooked up all the charging stuff. I'm using an older Astro Flight Lithium charger, with the version 1.5 software. (Current is 2.0)

When the balancer is connected and turns on, the balance lights on the right flash through in sequence. Every time, Cell 1 flashes green, Cell 2 yellow, and Cell 3 green. Does anyone know what this means? The instructions don't say anything about it.

The charging seems pretty much normal, with the Astro going through its C1, C2 and C3 phases, but so far, when the voltage gets up near 12.5, the voltage numbers start freaking out and the charger turns off, and displays "Fault". This is also not covered in the AstroFlight instructions. Static voltage on the battery at that point is just under 12.4, indicating that it is not fully charged.

Any ideas, guys?

Mustang Fever

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Did some more testing, and I've concluded that the Flight Power V-balancer is defective in one area: It's voltage measurements are way off, although it does a great job balancing the cells.

What's happening is this:

1. The Astro charger gets the pack up to 12.60V during C2, as it should. It then switches to:
2. C3, where the it alternately hits the pack with 1.2 amps, then turns off and watches the static voltage. It does this with the duty cycle getting wider and wider until it's satisfied that the pack is at 12.6, then signals "charged" and cuts off. But-

It won't do that when charging through the V balancer. The V balancer interprets 12.4 V as 12.6, and breaks the circuit from the charger through itself to the battery. So...

I connected my charger directly to the pack, but plugged in the balancer lead. It balanced the cells all the way up to an indicated 12.4 volts on the charger, then freaked out, all the lights started flashing, and it refused to turn on anymore. My multimeter, my whattmeter, and my charger all agree on the voltage when the balancer loses it: 12.4

I ran all my prop tests, and hooked up the balancer afterwards to check on the cells, relative to each other. All OK. I guess I'll keep the dang thing, unless someone can recommended a better setup.

I think I'm going to go with a 6x4 prop. Lot's of thrust at WOT, almost a pound and a half, pulling less than 25A, 72mph, and a good half throttle cruising speed, 60 mph at only 10-11 Amps. I'm thinking I'll be able to back off on the throttle even more, to down around 40-45 mph, and get 6 or 7 minutes. For the first few flights, until I see how rapidly the pack is going down, I'll stick with 5 minutes.

Mustang Fever

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We're having four days of 30mph+ winds, so no flying until next week. Did manage to do some taxi testing on my snow covered driveway, tho, and the airplane really gets up and scoots. ROS will be no problem.

Strykaas

[8D]

Mustang Fever

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Just now did the math to obtain the percentage of MAC that the CG is located on. 5.2% That corresponds to the location of the CG on my big Arrow with the fuel tank almost full.

I suspect that as root chords on delta wings get longer as compared to the wingspan, CGs may be moved aft. I've seen references to 15 or 20% CGs on F-106 models, which have a really long root chord in relation to the span.

Small Arrow: span 22.75"; root chord 16.25". Ratio 1.4:1

Small F-106, same wing area as small Arrow (about 220 inches square): span 21.65"; root chord 19.82". Ratio 1.09:1

I think these ratios indicate the inherent stability of a given delta wing planform. The lower they are, the more wing area hanging off the tail end, which gives more stability.
The F-106 is 50% "better" than the Arrow in this respect.

OK, you math/engineering wizards out there, how can I set up some kind of sliding scale that indicates where the CG should be for different ratios?

I suspect this discussion will end up being as useful as screen doors on a submarine, but it's fun to play around with.

Mustang Fever

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5 minute float test, after 3 tries at making a good battery hatch seal.

I used the standard method of putting a piece of plastic plans protector between the hull and the hatch, and putting the sealant on the hull. I used the red, RTV gasket maker this time. Worked really well- not one drop of water to be found inside the hull.

Mustang Fever

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[:


Snowbird!

Full elevator, feed in the throttle slowly, keep it straight with the rudder and she's gone. Way too sensitive in roll, had to concentrate really hard just to keep it steady. Have since set the aileron function way down, and bumped up the aileron expo. Balance seems perfect. After 2-3 minutes of laps at half throttle for trimming (a fair amount of right aileron- I think I have a slight incidence difference right to left) I set it down and it slid real pretty, taxied back and went home. A check of the battery revealed less than one volt down from full charge, so 10 minute flights are within the realm of possibility.

I would recommend this to any extreme speed pilot with lots of experience. Get those plans to the copier and reduce em.

oceansfiftyseven

Right on! Congratulations! Rich

Strykaas

Cool

Any way to fix that incidence issue though ?

Mustang Fever

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Thanks, guys.

No incidence corrections possible. The wings are epoxied on. You have to look close to see that I have more reflex "up" on the right than on the left, and the transmitter says I've used 20% of the available trim in that direction. (I ended up gluing the wings onto my big one, too, as the right panel was getting "floppy".)

I just did the math - this rocket has 200 watts per pound. [&:] I could do my EF-106 using a similar motor/battery combo and probably make it a bit bigger, say 250 square inches of wing instead of just over 200, and still have plenty of scoot. If I do the EF-106, I want to use some kind of micro retractable gear.

Mustang Fever

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I just saw the ad for the KMP Avro Arrow EDF today in MAN. I went to the website, and started drooling. I have to have one. The KMP website is also the first place where I have seen the truth about what happened to the Arrow project: the RCMP suspected a Soviet mole at Avro, and they were proved right by the Mitrokhin archives.


http://www.kmp.ca/product_info.php?p...fd5cce8d24f405

Mustang Fever

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Got in another flight yesterday, and the changes to the aileron function worked out exactly right. She's about as sensitive in roll, now, as my big Arrow. Had a lot of difficulty with takeoff, and I think a bit of nose heaviness is the cause. I spent some time this morning getting the CG exactly where I had calculated it should be. Finally had to use a 1/4 oz lead piece in the back end of the nacelle. For future reference, the servos should go in the forward location. I used the aft.

simhatus

Hi

Just read your message , must check more often.

I have aquired a friends damaged arrow that was built at the same time as mine, i am currently restoring that.

Your mini arrow looks nice, i have a half built mini north star that will be powered with a cyclon 15 brushless motor.

Simon

Mustang Fever

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Simon:

Glad to hear you're getting back into the Arrow business.

The mini Arrow went for its third flight today, from frozen Lake Cadillac. Temp was about 15F, and no wind. After 5 or 6 laps, my finger tips got cold, so I brought her in. The re-balancing really worked. Takeoff was not squirelly with no nose planting tendencies, and I had plenty of elevator authority during a final approach power off glide.

Can you post some pics of your mini E Northstar here?

Flypaper 2

I wouldn't read to much into the history of the Arrow on the KMP website. For starters it never did fly with Iroquois engines, only the Pratt& Whitneys. Went through the sound barrier in a climb on its 3rd test flight. Did do almost mach 2, mach 1.96 to be exact, on the Pratt&Whitney engines. Also first fly by wire plane.

Mustang Fever

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I took a look at the Mitrokhin Archives, and although I didn't take the time to find the Avro reference, I did find a lot of the other stuff they talked about.

Got flight number four in today, at the Midland Club snow fly. Did well, right up to final approach when I went to throttle up and there was no one home. Minor damage- had to do a nose job this afternoon. The cause was a bad connector pin solder joint.

Soft snow takeoffs have been difficult from the start with this bird, but I think I finally got the combination today. Hold about half up elevator, and nail the throttle. It accelerates so rapidly that it doesn't have time to get in trouble.

Mustang Fever

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I starting to think I built the wrong bird for the right purpose- snow flying.

The Arrow is so light for it's size that I can only consistently takeoff from FRESH, light snow. That's because anything older than a day or two seems to get sculpted by the wind into steppes, and then gets partially melted and refrozen until it's a series of bumps. The Arrow accelerates to about half flying speed, gets thrown into the air by a bump, then the high power plant location causes an immediate face plant. I tried today at the Jersey Coast Sport Fliers field in Colts Neck, and gave up after a half dozen attempts and trying every combination of elevator and throttle I could.

My next entry here will be about flying it off the water this spring. I'm thinking I'll get out to the lake about sunrise, before the waves have a chance to get going, and it should perfect conditions for the little Arrow.

Mustang Fever

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I found a pond at a park near my son's house, and attempted a water takeoff. No dice. The torque from the motor causes the left wing tip to dig in as soon as she gets up on plane, then she spins out. The last time, she spun out and got inverted. Wrecked the Rx, but nothing else. Right aileron doesn't help because there isn't enough airspeed.

So..... here's my solution. I'm waiting for a glass calm day at Lake Cadillac to test it out. Wish me luck.

This thing's a great little flyer, but takeoffs have been a *****.