Eflite uMX Whipit: Horizon Hobby has given us an easy conversion for an 18mm RCRG

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At least, it certainly looks like it........the new Whipit micro DLG

Span about 24", flying weight of 1.53 oz with battery, a carbon spar strong enough for discus launching.

https://www.horizonhobby.com/umx-whipit-dlg-bnf-basic-eflu3150

Video:

https://www.horizonhobby.com/umx-whipit-dlg-bnf-basic-eflu3150

Modify the rudder and fin and put it below the boom and add a 18mm motor pod. Would not be hard to do a depron and carbon inverted V tail either.

Will be on order at my LHS on Monday on Monday....:)
 
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That was exactly my thought when I saw that info on the Horizon Hobby site.....very much worth looking into for exactly that purpose.....
 
What would be neat is a good *beginner* RC glider kit that converts readily to RCRG. You know, one that you don't have to 'fly' on the way up....
 
Well, the uMX Whipits have arrived. Picked one up at my LHS today at 5 bucks off the normal street price, net price 64.95. Includes the AR64xx AS3X brick. A real bargain. It does not include the one cell 150 mAh lipo, but I have a large stock of them. All you need to fly it is the RX battery, a compatible Spektrum TX and a way to charge the small lipo.

Wingspan is 24.4", wing area is 80 sq in and the advertised weight is 43 grams. All flying surfaces have carbon reinforcement. Wings and tails are molded Depron type foam and the fuse is unusually lightweight injected molded EPS foam with a molded plastic nose cover. Tail boom is 1/8" sq. carbon tube.

Have been tinkering with it tonight and thinking about the conversion to rocket boosted flight. This first one will be for use as a B and C class boost glider with a pop pod. I think it will be fine with a B and ought to handle a C, but it might flutter a bit.

I have already peeled most of the stock decorative stickers off, which ought to save a gram or so. Will mist a bright color on the wingtips for visibility.

I think the easiest conversion will be to invert the fuse, bolt the wing to the mount as a low wing model and slip the vertical tail even lower on its mount, about 3/4", to clear the rocket exhaust. This also has the effect of lowering the horizontal tail from 1/2" above the boom to 1/2" below the boom, also spacing it further away from the rocket exhaust. It will need a little bit of foam to fair in the wing to the fuse as a low winger, plus some small standoffs on the rear wing bolts to set the wing incidence. The only other mod will be to move the rudder control horn so that it lines up with the pushrod again.

Will do some test glides tomorrow in the low wing configuration to if the dihedral is enough with the center of mass raised up.

Easy enough to reverse the controls as needed with modern TX units.

One advantage to this overall approach is that it would be instantly convertible to stock configuration by assembling it normally and reversing the controls again.

Here are some pictures of the stock model, high wing, and one of it assembled as a low wing model with the fuse inverted and the vertical tail lowered.

More to come!

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I'd replace the depron tail feathers with balsa. BP motors can be bad news even at that distance.


Richard
 
Just went out to the very soggy front yard and test glided the Whipit a few times. Glides, turns and handles nicely as a low winger.

Were it not for the terrible weather, I could be launching it in 2-3 hours!
 
Been wondering about it too since it was announced. I got the impression it might be too weak for anything beyond an A3. Certainly the UMX Radian (Mini-Radian) wings are too flimsy, twist too easily, so would likely flutter (I just checked.... yeah, twists easily). But of course the UMX Radians have a higher aspect ratio and perhaps thinner airfoil than this.

Well, you know your stuff with Rocket Gliders an what to expect.

I will say if I tried one on a B, I'd use a B4, less thrust longer burn than a B6 (I have had models such as the Stiletto-B Slide Wing Rocket Glider, which when built with light balsa the wing holds up on B4 power but can shred on a B6). If I dared try a C I'd use a Quest C6 from China, which are more like C4's as the black powder used burns slower than usual for whatever reasons.

I have done other B4 and C6 powered R/C R/G's, designs of around 95 to 110 sq in depending on model. They boost so fast, that the B4 helps make it boost not quite as crazy fast, and the Quest C6's also not quite as crazy fast.... but still fast. Wings on those were hotwire cut foam cores with composite laid up fiberglass skins and some graphite on top and bottom for spars. But at high speed the spars don't prevent torsional flutter, it's the fiberglass skin stiffness that does that.....unless too weak or boosting too fast (have not had one fail on boost yet).

It could be possible for the wings to flutter but not shred. Long ago (1970's) for small free flight Rocket Boosted Gliders, I would use Styrofoam Meat Tray foam, NOW we call it Depron. In small aspect ratios it worked well. But for even just medium aspect ratios the bare foam fluttered on boost.... held together but it made a muffled "buzz" sound and visibly had way more drag on boost than a smaller glider with balsa wings that did not flutter. In the 1990's I re-discovered meat tray foam wings, but used a simple vacuum bagging process to apply Japanese tissue damp with epoxy to get a smooth surface and the tissue provided a lot more stiffness than before.

- George Gassaway
 
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Very interesting find!! I was going to put a couple on order but they are out of stock already, grrr. The wing loading looks reasonable and I think with a vacbag job the surfaces will be plenty stiff. Looks like a quick way to get a couple of ships in the air while I work on the programmable foam cutter rig. George I remember the early bare foam gliders with the buzz-n-shred tendencies. :wink:
 
A B4 is the first planned motor.

The wing and wing spar is far more substantial on the Whipit than the micro Radian, as it was designed and stressed for a mild discus launch. The carbon spar goes nearly to the tip and you grasp the tip of the spar when you do the mild discus/sidearm launch. I went out one afternoon recently and trimmed my flying buddies stock Whipit for him and flew it through about a dozen launches.

I foresee no issues on B4s, but it might approach the "speed of Depron" with an Estes C6. I might ballast the pop pod with some extra weight should I try the Estes C6. Do not have any Quest C6 at the moment.

It is really a delightful model flown stock. I would highly recommend it as a low cost trainer for an aspiring RCBG pilot. After a couple of hundred hand launches, you would likely not have any trouble with a decent RCRG.

Ended up working this weekend, but might be ready to launch the Whipit RG next weekend.
 
An unboxing video, review, and flying that begins at 9:30:

[video=youtube;kk5-3ROnMO8]https://www.youtube.com/watch?v=kk5-3ROnMO8[/video]

Several other vids to be found as well.

Also this thread on RCgroups which began with the announcement in January. Seems like people started getting them end of April, page 28 seems to be a good one to start with:
https://www.rcgroups.com/forums/showthread.php?t=2335017&page=28
 
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Another thread on RC Groups.

https://www.rcgroups.com/forums/showthread.php?t=2334904&highlight=whipit&page=60

Bottom if the page linked above has a video of some fixes/improvements one guy made.

Very notably (video below), he shows where the wing root are is wrinkled from stress, possibly over-tightening the wing top support plate (about 1:20 into the video). Also some cracking possibly due to hard landings.

I am going to get one of these soon, maybe by Tuesday if one is in stock locally. I'll try something to beef up the root area a bit, perhaps some lightweight glass cloth for the first few inches from the root, perhaps a 2nd layer for the first inch or two from the LE where those cracks appeared.

[video=youtube;--aPTj20IW4]https://www.youtube.com/watch?v=--aPTj20IW4[/video]
 
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Got a WhipIt today. HobbyZone has it for $69.99 on their website. But they have a walk-in store in Plymouth, MN (near where I am, currently), so I got it there…. where they had it for $62.99 (can only get that price in person, not mail order).

Wing stiffness….feels really borderline for B4 speeds. I'd be really surprised if it could take a C6 without at least fluttering a lot.

Anyway, too windy the next few days to try throwing it.

I took some pics with two "Raven" style models based on the Raven-10 wing used for the FAI S8D Rocket Glide events.

The Raven A , red wing, has a span of 19.8", area of 65 sq in, and glide mass with battery and burned out casing of 34 grams. It is just about perfect for A power. Decent boost height and if there is a thermal it can catch it.

The Raven C , natural blue foam wing (and red leading edges), has a span of 34", area of 144 sq in, and glide mass with battery and burned out casing of 84 grams. It was designed for C power (the design won A, C, and Team Dv at NARAM last year), so it also flies of course on B's, gets about 75-80 seconds in dead air on a B, over 3 minutes dead air on a C.

The WhipIt, glide mass of 43 grams. That is without burned out casing, engine mount, and other possible modifications. Wingspan a bit over 24", wing area 85 sq in.

In the past I have had an R/C R/G built to fly B R/G at NARAM-51. Based on the Apogee 30 DLG wing (Apogee is the glider design name, nothing to do with the rocket company). Composite foam/glass with graphite spar, and IIRC the span is about 28-30", wing area was about 110 sq in and glide mass of around 95-100 grams. The larger Raven-C is lighter than that one mainly due to having lighter R/C gear than the B model used.

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Flew the WhipIt late Wednesday afternoon when it was pretty calm, and 3:00-3:30 PM Friday with low variable winds and lift.

It has a really nice glide. I added a little bit of clay to the nose. The elevator throw was too much, I went to 33-40% elevator throw using a DX-8 TX, I think I ended up with 40%. Rudder (aileron channel) is at 100%. With the relatively low amount of dihedral compared to other small gliders I fly, I had expected it to be sluggish and need more rudder throw, but no, it is quite responsive as-is to rudder.

Throwing it, my left-handed discus throws usually end up with the model climbing banking a bit to its right, sort of like a spiral climb, but as a coasting spiral. Which is reminiscent of old classic free flight hand-launch gliders that would be thrown with the wings banked for a spiral climb, and trimmed to roll out at the top. So in this case, with the WhipIt often in a bit of a banked right climb spiral, I give it left rudder at the correct time to roll it out level near the top. Of course the throws and transitions are not 100% consistent, sometimes it needs some elevator too, either down if it is about to stall or up if it has already stalled.

My throws are to about 30 to 40 feet, other people could probably throw higher. Glide times around 25-30 seconds. Friday when there were light variable winds and thermals, it was the thermals that caused the wind to vary so much in velocity and direction. Those are great conditions for flying since if you know the basics of thermal picking, you have a good idea of where a thermal probably is. Although if the thermal is 500 feet away, perpendicular to the general wind direction....you can only wish you were 500 feet closer to it since it's not practical to throw and glide it 500 feet and have any useful altitude left to catch such a thermal. So, anyway, more useful for finding thermals that are close, and flying this kind of model helps with learning how to find thermals or brushing up. A lot of times, found a little bit of lift that improved the time by 10-20 seconds. Sometimes a circle or two that held altitude, but then lost it. But I did have a couple of flights that caught lift and went up for awhile. One of those was for probably at least 3 minutes. I could have made that one last longer but it was starting to drift behind a house and when I steered it clear of the house it fell out of the lift.

So,. anyway, it flies pretty well. I will say it is a little bit sensitive in pitch, something about the handling. It reminds me of an R/C Rocket Glider kit I built long ago that had a smaller horizontal stab area than I was used to, and the pitch stability felt a bit different and sensitive. So I think if it had a bit more horizontal stab area, that might "feel" a little better. In the pics abov,e look at how much bigger the stab is on the red winged Raven-A model that has a smaller wing than the WhipIt (I know the stab area on mine is a bit bigger than needed but I like to err on having the stab a little bit too big than a little bit too small). But it is a bit of a problem to try to make the kit's stab bigger. If the whole stab was replaced, a cheap styrofoam plate of about the same thickness might make a good source for material to cut out a larger stab. Balsa would be heavier requiring a lot more noseweight to balance, although if this was converted to fly as a rocket glider, the engine and pod assembly mass could be located accordingly before gluing the pod on (test throws to find the exact location, with the pod taped on).

Having flown it, I think it would make an excellent conversion as an A3-4 powered Rocket Glider. The wing is probably (?) stiff enough to handle an A3 boost. I'll be interested tohear how it goes when Tom tries it on a B4. If it holds up to a B4 without fluttering, it would be a superb model not just for learning R/C RBG's, but a very competitive one too.

The thing this one offers that others do not is the potential to learn how to fly R/C with this model.... just by throwing it, and once learning how to fly R/C WELL, adapt it for rocket power. Otherwise I always recommend that people learn how to fly R/C first with a beginner model. And,. this can be a beginner model, a unique one that can also be adapted for rocket boost (pending results of seeing what actually happens on rocket boosts).

As for myself, I have other rocket projects stacked up (preparing for NARAM and the US Team flyoffs). So I won't try to adapt it for A3 power till after July. Till then, I'll get good use of it flying for fun and practicing flying small thermals.

- George Gassaway
 
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George, Thanks for the ongoing commentsr regarding the Whipit - I have tried to order a couple from Horizon (well place a backorder) but it won't ever let me finish the transaction. I could call but by then I have moved on to something else. I, too, am curious to hear how it flies on a B4.
 
Finished up the Whipit RC BG conversion tonight and it is ready to test. Picture attached.

As I mentioned before, I inverted the wing mount on the Whipit and turned it into a low wing model to prevent possible heat damage to the wing and to get the tail surfaces lower in relation to the motor as well. Decided to make a new vertical tail and preserve the original tail.

Some design choices were made for my conversion in order to be able to convert the Whipit back and forth to a completely stock model, whenever I desire.

If it works well, I might get another one and make it into an RC RG permanently, with other conversion design choices.

Glider weight stayed at 43 and a fraction grams and the weight with pod but without motor or streamer is 57 grams. The decal removal seemed to offset the added socket for the booster pod attachment.

Picked up some fresh B4-2 motors today....;)

Planned first flight is Wed afternoon after I get to Littie Rock. Will report back on the success or failure ASAP....:) Still betting the B4 will work. Will have lots of photos and possibly some video of the first flight.

George, good comments on the Whipit. I found it to be fly very well, personally. The Whipit is very much following current practice with smallish tail volumes for small DLGs. Small DLG pilots want excellent maneuverability over excess stability in order to work tiny patches of lift very near the ground.

image.jpg
 
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Well, the news is good! The Whipit RC BG is up to the challenge of the B4 motor!

Launched it three times this evening on B4-2s and it worked extremely well, except for a hung pod on the first flight. Was easily able to circle and land with the pod in place trailing the streamer. shortened the pod attach pins after the first flight. Boost was dead vertical on two flights and angled off a bit on one flight.

I saw no evidence of flutter anywhere in flight on any boost.

After the flight where the boost that angled off a little bit, I did see some evidence that the 3M Blemderm tape that I used for rudder hinges had stretched out a bit under the boost air loads when it angled off from vertical. Will get rid of the stretchy Blenderm hinges shortly.

I do think it helps to keep the boost as close to vertical as possible to help keep the airspeed down a bit. I predict a horizontal boost on a B4 could easily exceed the speed of foam....:)

We got video of the first and second flight and I will upload later or tomorrow. My still photographer was running late and we did not get much in the way of still photos.

Here it is on the rod for the second or third flight.

Dead air time with imperfect trim was bout 1:20 Wind was about 4-6 mph.

Site is the FARM R/C club flying field south of Little Rock, AR, close to Wrightsville, AR.

More details soon.

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And here is the video of the second flight! Time from launch to landing was about 1:20. Extremely happy with the boost performance on a B4.

Not sure why the pitch trim was a bit off after transition. A number of hand launches before the boost flight had it flying nicely with no nose weight. Needed more down trim after the boost was over. Trying to avoid adding any extra weight, but might have to add a touch of nose weight as others have done. Note near the end of the glide how it did with more down trim.

Many thanks to my flying buddy Paul Willenborg for his excellent video work.


https://www.youtube.com/watch?v=Hzuf7JEhaHI&feature=youtu.be
 
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Little more info. I had added a bit of aluminum tape on the foam fuse behind the pod for heat protection. After the first boost, you can see a bit of heat damage on the sides of the fuse near the sides of the pod pylon area in the picture. I covered these areas with a little more aluminum tape.

The other picture is of the tail group after the three launches.
Note the small scattering of BP burning particle impacts on the stab LE.
And note the BP exhaust collecting around the vertical tail mount, in the tape edges, and in the hinge line area of the vertical tail.
Also note the tiny bit of heat-caused erosion at the top front of the vertical tail, on the foam above the tail mount.
The gray exhaust deposit patterns on the tail boom behind the horizontal stab mounts are interesting.

I will add a little Mylar tape to the stab LE and over the vertical tail mount.

You cannot see it, but I added a small carbon spar the the hinge line area of the vertical tail, in a shallow V-groove on the center line.

Based on this minimal heat damage to the foam parts, I think converting the Whipit to a low wing with under-slung tail surfaces was a good idea....;)
 
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Congrats Tom! Really impressed that it held up to a B4.

- George Gassaway

I was pretty sure it would. However, I am in no particular hurry to try it on an Estes C6, though...;)
Might have to get some of the Quest C "less than 6" motors and try them first.

Depron type foam with some well thought out carbon rod or strip reinforcement compares well to balsa wood at a similar weight.
 
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Nice work! I have a couple of these on the way finally...I'll keep you posted on if and when I do a conversion to RCBG to either of them. I appreciate the work you have done to give some initial thoughts on how to do this.
 
Way behind in updating this thread.

Have had two more flights since last June. One at a Dars launch in Frisco Oct 17 and one at my local RC field a couple of weeks later. Both on B4-2 motors. The B4 at the Dars launch seemed be out at the upper end of the performance bell curve as the boost speed and altitude was noticably more than the other 4 flights. Still held up well and no evidence of flutter.

A fun little glider.
 
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