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Thursday, December 30, 2010

Update: Beaver Goes BL

Cost: 40" GWS Beaver ($30) + Super Tiger T 370 ($15) = $45
(reflects 20% Tower Hobbies member email discount)



Luv that Beaver. I plan to run this as a child's plane with a 10x4.7 SloFlyer and 1000 mAh 11.1V LiPo on a buddy box.  Switching to the ST 370 saves 0.9 ounces (10% of the no-battery aircraft weight), doubles max prop RPM, and allows the use of a same weight but triple capacity and 50% higher voltage 3S Lipo.   Hopefully, the BL motor doesn't tear the wings off.   Toning the throttle curve down should give 45-60 minute flight times with about 1:1 thrust to weight ratio.  I sandwiched all leading edges, the CG line, all all tail surfaces with clear mailing tape for a little more strength. 

More here when the BL Beav shoots skyward:


Houston we have a problem.  33 ounces of thrust from the ST 370 w/10x4.7.  12 ounce plane.  Time for 2s.


First test flights:

The first flights reveal what a beautiful little floater this air plane is.  It is so light that it is very sensitive to small changes in weight distribution and flight characteristics change accordingly.  Balance is gong to be a bit of a trick.  Even with a 7.2V 2S battery instead of an 11.1V 3S, the plane wants to pitch up to vertical under full power.  Elevator effectiveness is changed dramatically by thrust output (rudder effectiveness is unchanged).  At the same time, the plane is so airy, it is easy to trim out a broad range CG points.  So there needs to be a delicate balance between the trimmed elevator position, the best CG location, and the amount of power applied from glide to mil.  I am searching for the best battery position and may need to alter the recommended thrust line given the tremendous output of the feather light BL S/T 370 motor.  When I get it sorted to perfection I'll post the info/photos here.

Overall, it is easy to see that the plane will putt along like a dream at 20-30% throttle. The unique power to weight ratio of the ST 370 is presenting some solvable challenges to otherwise carefree handling.  Shouldn't be long to find the right CG placement and thrust line, if required.

Update:
Winds are not friendly to a 12 oz model, so we have a little longer development cycle than desired.  This morning I was able to float airborne in moderate swirl and identify the need to lower the thrust angle.  In order to balance the Beaver with the S/T 370 in the nose, I have pushed a 1000mAh battery all the way forward to the lip of the cowl cowl.  It is actually a very convenient spot since the wing can stay in place while changing batteries.   I was thinking 2S but for now at least, I'm going with 3S due to (1) I don't have a heavy enough 2S battery to balance the light engine and (2) the plane can barely hover with 2S.  The Beaver is perfectly balanced with the 1000mAh.


Update - Full Flight Review

Final verdict up front:  A

This little Beaver is a amazingly slow super fun flier, but because it can go so slow, it can be quite unforgiving if you fully stall it out.   If you have a small field and need short take offs and landings, it is exceptionally capable if not a bit tricky, a lot like the real thing.  It can glide incredibly far and is often advertised as a slope soarer.  In fact it can be difficult to spot land because it catches air so well and only has rudder and elevator--no slips. 

I wound up using a 3-cell brushless Super Tigre 400 ($19) that weighs less than the chunky stock brushed 2-cell, the larger coils are a better match to a smaller, low pitch prop than the 370 was at half throttle, which is where the Beaver thrives.  An 8x4 is the perfect prop size to keep both thrust and speed under control while still climbing out 80 degrees nose high in a steep torquey spiral, or straight ahead with half right rudder. The increased low rpm low prop load efficiency of this motor is impressive, average flight duration with a 1000 mAh 3-cell is about 20 minutes with mixed performance.  Practical throttle range spans from around 40% (DX8) for an easy max endurance cruise, to 60% for spirited over the tops.  A larger low pitch prop might increase cruise flight times even more at lower RPM, but full throttle thrust would probably need to be ESC travel limited to keep the plane under control at all times.


GWS Beaver  --  Super Tigre 400  --  GWS 8x4 Prop  --  1000 mAh 20C 3-cell
Flight Regime
Power Setting
Amp Draw
Flight Time
Extended glide
30%
0.3
---
Max Endurance Cruise
40%
1.2
50 minutes
Fast Cruise
50%
2.2
28 minutes
Over the Top Aerobatics
60%
3.6
16 minutes
Max
100%
6.2
10 minutes
Based on installed static thrust  - Airborne Amp draw will be lower

The plane could easily haul a 30% larger battery with the high T:W ST 400 up front, but with the above flight times, there is no need, and being an Induced Drag machine it might not fly significantly longer.  A smaller battery would likely require some lead up font to counter any weight reduction, so it may not make sense either.  I'm very happy with the overall power system/flight regime match.

The wing design of the Beaver is actually an under-cambered pocket, which provides good strength for the very light construction and an incredible amount of lift, as it is 2/3rds airplane wing and 1/3rd para-sail. The end result is an ultra light foamie with classic ($25) Beaver looks that easily flies backwards in a steady headwind. Winds are not kind to any 12 oz floater, and the GWS Beaver is no exception.

The build is more like a foam kit plane than ARF. The fuse and wings ship in halves and need to be glued up, it takes a full day or two to complete. The fuselage is tough. The wing is not very thick, but well supported with functional struts--I reinforced mine with clear mailing tape from tip to tip. The supplied push rods don't work without a secure sleeve around them (I used carbon fiber tubing pinned with foam safe CA), they bend way too easily making the plane difficult to control.  The landing gear is thin wire that flexes a lot during medium bounces, so much so, that you can strike the prop.  I solved that problem with small collars on the piano wire gear struts, close to each wheel, then I stretched a long thin rubber band over the two to act as a support and shock absorber.  The steerable cheap plastic tail wheel functions well, but the plastic has no grip--replace with a conventional rubber or foam tire for functional steering.  The plastic pinwheel mains work great, and are darn near weightless, but are the low hanging fruit to be replaced for scale looks.

Even though this plane is an exceptional slow/fun flier and excellent glider, it's not always the easiest plane to fly near the edges of its extreme performance envelope, and that will delight intermediate to advanced fliers.  The elevator can be overly sensitive to high throw due to the short distance from the CG. The wing design is pocket under-camber, which catches the air beautifully and floats just like an air-hockey puck (same principle). It has plenty of dihedral and is largely self correcting in flight, but if you push the rudder to far or too hard too fast, the wing can display some pretty unstable and asymmetrical, falling leaf stall characteristics. Loops, Hammerheads, Barrel Rolls, and 3 foot radius cornering turns are possible. It can make a really wonderful slow flying trainer after an intermediate flier trims it out and most importantly, limits the throws before handing it over.

As long as one realizes that the Beaver's amazingly short take-off rolls (5-10 feet), steep climb outs, near motionless slow flight, and glider-like engine-out performance comes at the cost of being quite tricky on the edge of those same generous limits, it will be a sure fave that can do uncanny looking stuff with the simplest maneuvers.  Commonly available for $30 or less, it's a lot more fun than ordering pizza.

Tuesday, December 21, 2010

UMX Beast Review

Addendum: As a result of my review, Horizon lowered the price of the UMX Beast to $99, earning it a B+ Z8RC overall rating.  Horizon deserves kudos for taking criticism and correcting their flaws.

Standing tall (5.5 inches)
In keeping with the theme of this blog, and unlike the unsophisticated sales pitches you'll find disguised as reviews on the popular scam sites, I am genuinely putting the new, E-Flight UMX Beast though its paces.  As always, I am not contractually bound to give a positive review that is tied to sponsorship money.   The review that follows has not been bought and paid for by the model's manufacturer.

That said, I enjoy a great product as much as the next guy.  While my reviews are a lot tougher than others because I actually know what I am doing, and have my own money at stake instead of requesting payment, perks and gifts, they are also much more fair to products that actually make sense.  
Horizon did a great job creating a tiny Pitts Model 12S II
Bryan Jensen's airshow animal, born March 27, 2009 
(Update: Died Aug 20, 2011.  RIP Bryan)

First impressions:

The 180 motor is smaller than the spinner
The little Beast is a great looking little model.  As usual, Horizon clearly paid attention to detail in an effort to deliver a high quality product, deserving of their premium pricing.  The paint job is very attractive and almost flawlessly executed.  Construction method is unusual for a micro, with a higher level of craftsmanship evident to assemble the wing struts and wires, a clear bubble canopy, and a more complex battery compartment and engine bay under a magnetic hatch.  Speaking of batteries, this is the first 2-3S ready HH micro.

Also typical for Horizon micros, is the use of fragile base material.  The flimsy foam board is well reinforced by carbon fiber wiring that mimics the 1:1 scale Pitts, but it is the same old poor quality and low durability flat sheeting.  Even the fuselage is weak compared to the better micros, if you aren't careful you could crush the integrity of the side walls with carefree handling of this product.  The clear bubble canopy is a nice touch, but it is so thin you can permanently dent it just by looking at it funny.  The wings and tail feathers need special care not to crease or snap their structural integrity during routine handling.  Reasonably strong micros, like the Hobbyzone Champ, have nothing to worry about here, Horizon/E-flight continue to churn out feeble builds that will hardly last the day if you aren't unreasonably careful.   The use of flimsy foam presumably keeps the weight down, but unfortunately for that rationalization, we've seen solid micros that weigh less.

Just to reiterate, the Beast's frail build doesn't stem from a lack of care, the problem is the selection of low grade foam as the base material.  It's a real shame, because the Beast, like many ultra flimsy Horizon micros, is a pretty cool plane.  One obvious way Horizon could reconcile their neat ideas with their inability to cobble together a durable product, is price.   With only a few happenstance crashes away from crooked obsolescence, it seems $70 would be a  more reasonable retail price point than $170.  For the amount of use even the best RC flyer will squeeze out of their low grade materials, the Horizon micro fleet is horribly overpriced and the Beast is the worst offender yet.

Another troubling thing about the product is the battery system, some monopolistic urge convinced E-flight to stray from a standard JST 2-cell balance connector, making the included battery charger your only lifeline to air time.  That wouldn't be as bad if they included an AC power cord for their custom charger, but recharging your battery at home costs extra.  Worse, my charger was defective out of the box, failing to charge the battery after more than 90 minutes of hook-up time.  I was forced to put an adapter together to mount the included battery to a standard balance charger.

The delivery defect made me think a little more about E-flight's choice of the battery.  Shipped with 2S,  the Beast's unique power system forces you to add a small Lipo + charger inventory that really doesn't overlap anything else in the market place, effectively raising TOC substantially.  As you can see below, the stock battery won't set any endurance records either, so you'll need at least one more.  That raises the cost by $14 for another tiny 120 mAH Lipo, or $16 for the 180 mAh version, plus about $20 for an AC adapter to use the included charger at home.   If the charger itself goes poof (like mine shipped) that's another $20 (estimated since no direct replacement is available).  That makes the effective cost to both own and operate the UMX Beast around $205.

Additionally, cell's this small are hard to find on the open market, meaning there is no downward price pressure on E-flight to bring their prices in line with reality.  It strikes me that a much smarter idea would have been to supply the UMX Beast with a standard, double battery input, to internally link the required number of 1-cell's in series.  Then, users would not be forced to buy a unique charger (even with the BNF version) and could use their existing 1-cell battery pool, or at worst, have access to any number of $1 to $5 batteries (double that cost to match the stock setup).  For that matter, it would be less expensive, and provide much more flexible power and charging options to snip the connector off the included battery and toss it in the trash, then and solder up a multiple 1-cell-series connector.

It is a sad day when your customers can easily blow away your value proposition using retail price components from your own parts dept.  E-flight, either your engineers are clueless or you are offering intentionally silly product configurations for the express purposes of ripping your customers off.  Disgusting incompetence in either case.

Here is the parts list to fix E-flight's UM-intelligence:

The Beast looks the part, even as a pip squeak

The miniature Pitts 12S II tipped my scale at a portly 2.2 ounces with the included light-duty 120 mAh battery, making it very possibly the heaviest UM ever.  For comparison, the 3D Ultra Micro 4-Site mini bipe only weighs 1.3 oz with a 150 mAH, and it suffers from the same 12 hour half-life super flimsy base materials.  Fortunately, initial installed thrust tests look promising, with exactly 3.0 oz of fresh battery pull, giving the mini Beast a respectable Thrust-to-Weight Ratio of 1.36.

"Respectable," that is, while it lasts.  Beast LVC motor waver ensued after a little over 2 minutes of T:W testing at full throttle. A more realistic battery weight would impact the peppy T:W, as will a rapid degradation of available power as the flight progresses.
 
Test Area
Result
Flying Weight w/120mAh 2-cell
2.2 oz
Fresh Battery Installed Thrust
3.0 oz
Fresh Battery Max T:W Ratio
1.36
Fresh Battery 1:1 T:W
80% Throttle
Run Time – Full Throttle
2:24 to LVC
Run Time – 60% Throttle
4:53 to LVC










The UMX Beast  arrives just in time for Christmas.  
It looks so nice under the tree it is tempting to display
it instead of fly it.  Nahhh!

Flight Impressions:

Too windy for a full review, today.  

I got the little Beastie airborne for a short flight (bounced around by winds, but controllable).  I couldn't help but notice that it felt a lot like a UMX 4-Site.  I suppose that shouldn't be unexpected since the 4-Site has the same wingspan, wing area, and flat foam "airfoil."  The Beast definitely has a higher T:W, and notably heavier nose when the power is down.   In fact, I didn't put quite enough up-elevator throw in my low rate setting.   In the heart of the flight envelope, the Beast is a faster 4-Site with a little more oomph when the tail is down.  Overall though, based on the Beasts edgy advertising, I expected a more outrageous 3D experience than I got.

The Beast is built a lot better than the 4-Site, which isn't saying much.  It has a beefier fuse and more CF wires to keep the tail and wing box from going trapazoidal.  

At first blush the Beast is a really fun plane to fly, but I generally prefer the lighter wing loading and similar handling at slower speeds offered by the 4-Site.  Additionally, the 4-Site has the option of floating down-lines with its giant optional speed brakes.  At half the weight and wing loading, the 4-Site is the more capable 3D micro, with the exception of straight-up pull.  The 4-Site is more susceptible to winds, but it can also be flown in small indoor spaces.

At around $205 BNF operating cost, pre-radio, it is hard to imagine passing up a hand-covered Great Planes 41" Edge 540 ARF @ $105 for a semi-disposable die-cut foamie, or even E-flight's own 42" Pitts M12 ARF for $150.  These large, capable 3D aerobats are top performers, and they sure ain't suckin' no Chick-let battery...


Great Planes 41" Edge 540 is $130 as a balsa & ply ARF 
including a Super Tigre .10 motor pumping a 1.5:1 T:W ratio
(minus 15-20% with usual Towerhobbies member coupons, no affiliation)
Even the 42" span E-flight Pitts M12 is $150 in ARF form
The 33.5" Art-Tech Pitts Special is $170 as a brushless 
foam RTF with a real symmetrical airfoil and solid build 
quality, including a nice 2.4GHz Radio, 1800 mAh 3-cell Lipo,
charger (with AC adapter), sim software, and Tx cable


In the flat airfoil EP foam category, there are numerous models that outclass the micro beast for the same price or less.
32" span Great Planes Edge 540 EP 3D
costs $89 with a brushless 250 included
(minus 15-20% with usual Towerhobbies member coupons, no affiliation)
The 17" span brushless TechOne Mini Eagle is $100 Rx ready
(minus 15-20% with usual Towerhobbies member coupons, no affiliation)

TechOne's 32" span F3P is $45 in ARF form
(minus 15-20% with usual Towerhobbies member coupons, no affiliation)
Kyosho's Minimum Ultimate is $120 as an RTF, with more 
power to weight on 1S and includes an LCD radio and charger.

Having flown the Beast several times now, I feel comfortable passing judgment.  The plane is really cute and a ton of fun for the front yard, calm wind warrior.  In terms of aerobatic prowess, it isn't bad at all for the small scale, but it isn't outrageously capable, either.  Thrust-to-weight is very good, but could use a little more oomph at times, especially as the battery fades after a minute of two.  It's not easy being a micro foamie in a very big world.

As far as 3D stunts, the Beast benefits from a lack of formal definition for 3D.  It cannot hold a stable hover, even though the T:W is better than 1:1 (for the first minute or two of each flight).  It can do a respectable knife edge, though it is a bit unruly.  Spins and inverted spins are good.  Snaps are good too.  Slow flight gets a little twisted at times, but mostly controllable fun with a consistent dose of rudder.  Vertical lines are all over the place, and not always from getting bounced around by puffs of wind, from a combination of torque, an off-kilter longitudinal CG, and manners that are rough around the edges.  I think the best word to describe the UMX Beast in "3D mode" is a very solid "flailer."  It's capability is nicely matched by a lack of precision. 

I think it goes without saying that the mini-Beast has its work cut out for it at the price point E-flight selected.  As a UM foam bipe, it is basically an expensive paint job on a faster, denser build that isn't necessarily better, aerobatically, than a lightly loaded 3D bipe or monoplane, plus it forces you outdoors.  As an outdoor brushless aerobat, it gets trounced by full sized 3D models that cost less.

So for a great looking UM biplane with a premium price tag, poor predicted durability, sexed-up but familiar flat airfoil flight characteristics, and an incomplete battery/charger system, I give the E-flight Beast a D+ (Avoid).  It's simply not a smart buy for any existing class of RC fliers, and its priced to compete with a class it can't see standing on it's tippy toes (yes, it has toes).

If E-flight cut the price to the $100 range or less, I could highly recommend the micro Beast.  It could even define a new class of front yard fun.  But front yard fun isn't fun when less expensive, fully capable 3D models literally blow it away.  That said, I think the entire UM(X) category is selling about triple free market retail value, due to monopolistic bad behavior on the part of colluding manufactures majority-controlling and exploiting the influence of low-cost Chinese labor. Until we see free market distribution in this market segment, companies like Horizon will continue to push prices higher and quality lower.  Worse, they are imposing a non-competition based distribution model that forbids price competition even among retailers, ultimately spiking the retail incarnation of extremely low wholesale price tags, preventing a lot of good products from reaching the hands of kids and low income buyers.  Sad.

Like other micros in the E-flight lineup, this paper-mache UM(X) will have a half-life best measured in days to weeks given moderate use.  So far, the only Horizon micro buy that didn't make me feel painfully violated is the Hobbyzone Champ, which can be reasonably durable given great care.  If you disagree with my basic value assessment, it is definitely worth dropping $200+ on this super-cute little lawnmower and its required accessories.

To add a little more pain, the manufacturer recommends a DX6i radio or higher, due to the Beast's touchy setup on a DX5e, raising the cost of ownership by another $150 to $400 for those without a Horizon brand expo capable radio.

Oh yeah, and the prop spins the wrong way!



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