What, another bent wing sailplane, you say? Those of you who read my story about the Super Soarer might now think I have a thing for gull winged airplanes. Actually, what really intrigued me about this little scale sailplane was the idea of aerotowing it with a small park flyer tug, which I got from the Hobby Lobby web pages.
The Hobby Lobby Habicht is scale model of the DFS Habicht, a German single seat, open-cockpit sailplane of the 1930's. This diminutive (dare I say "cute?") foam ARF spans only 1 meter, and tips the scales at around four ounces, ready to fly.
The ARF consists of just a few parts. The major components are all made of extruded polystyrene foam (EPSF), and include the fuselage, wing, and the horizontal and vertical stabilizers.
The fuselage is hollow: it's actually made from two halves that have been joined together, so it's built almost like a composite molded plane. It has lots of compound curves, and looks quite scale. One thing immediately noticeable is that there isn't a whole lot or room to place the radio equipment!
The gull wing comes as a single piece. The airfoil is a constant thickness slab, but it is curved to form an under-cambered shape.
The tail feathers are both made of thin foam, and are precut. The elevator and rudder hinge lines are pre-scored, making it easy to separate them later.
All the foam parts have a very nice, smooth finish. In fact the finish is so smooth that, from a distance, one gets the impression that the parts have been painted pearl white. The wing and the fuselage also come pre painted with blue trim exactly as you see in the photos. Note: be careful with using tape around the blue areas, as it may lift the paint.
In addition to the foam pieces, there are a few plywood parts, such as the main former, servo tray, belly skid and tail skid. All the hardware needed to complete the kit is also in present. Finally, the ARF includes some finishing pieces: a clear windshield and decals.
Assembly is fairly simple, though as you might expect, it's a bit complicated by the fact that everything is so small. Care must be taken with the foam parts, as they can dent easily. The instructions recommend working on a foam-covered surface to prevent damage, which is a good idea. I used 5-minute epoxy to assemble most of the parts. You can use odorless (foam-safe) CA or polyurethane glues too.
The first step is to cut out the "wing fairing" (the upper part of the mid fuselage), so that the shoulder-mounted wing can be attached in a later step. This is fairly simple, because three of the cuts have already been made. All that's needed to free the fairing is to cut out the rear portion. Make sure to always use a good sharp blade when cutting the foam, otherwise it may tear.
The wing saddle is precut, but the upper portion of the fuselage must be removed. The wing fairing removed.
With the fairing removed, the main former can be installed just behind the cockpit. I found that the ply former needed quite a bit of sanding before it would fit into the fuselage (as was the case with almost all the wood parts in the kit).
The former glued in place.
The next step is to install the nose-mounted tow release hardware. A wood reinforcement block is first glued to the inside of the nose. Next, a small wire hoop is mounted through the outside of the nose and into the block. A small tube gets installed on top of the block, so that it protrudes horizontally out the nose. The tube acts as a guide for a pushrod that engages the hoop to capture the towline. When the pushrod is pulled back, it disengages from the hoop, freeing the line (see the picture for a better idea of how this works).
The tow release in the closed position. When the horizontlal piece of wire pulls back, the towline is released.
The servo tray gets added next. I was a bit worried about being able to fit the tray through the hole in the cockpit, but as it turned out, it fit fine. As with the former, the servo tray required some sanding to fit correctly in the fuselage.
The servo tray.Yes, it actually fits through the cockpit opening.
A thin ply keel/skid needs to be installed along the bottom of the nose. There are no slots for this in the fuselage, so cutting them is a job for the builder. There is also the option to install a small high start tow hook (which I did). A small ply plate installed on the floor of the fuselage provides reinforcement for the hook. Finally, at the rear of the fuselage, a small ply skid is installed to protect the tail and the rudder.
Next we move to the tail feathers. The control surfaces are joined to their respective stabilizers, but the hinge lines come scored to the point where they are just about cut free. A bevel gets sanded into both the control surface and the stabilizer, which frees up the surface enough to move freely in both directions. After beveling, I hinged the surfaces with small pieces of transparent tape. Finally, the small ply control horns are glued in place in their precut slots.
Once the tail feathers are all assembled, they can be mounted to the fuselage. The mount for the horizontal stabilizer was a bit crooked, but a bit of sanding sorted that out. I glued the horizontal in place with 5-minute epoxy, using a couple of pins in front and back to hold the piece in alignment.
Attaching the horizontal stab.
The vertical stabilizer gets mounted into a tab on top of the horizontal, making alignment easy. Before gluing, I made a small triangle out of some scrap ply, so that I could make sure the part was positioned at ninety degrees to the horizontal stab. Again, I used 5-minute epoxy to glue it into place.
The pushrods included with the Habicht come with music wire already installed in the housings. The ends of the wires are pre-bent, so there's no way to adjust the length of the pushrods, or the linkage. Adjustment is actually accomplished by the positioning of the servos, which I'll get to later. Small dimples in the rear fuselage mark the pushrod exits, so holes can be made in the proper places.
The pushrod housings get glued in at the tail, and at the former in the forward fuselage. Care must be taken to make sure the correct pushrod is going to the correct surface. The pushrods are the same length (though the instructions incorrectly state that the rudder pushrod is longer), but they can be told apart because the wire bends on the elevator pushrod are at ninety degrees to each other. On the rudder pushrod, the bends are parallel.
Once the pushrods are installed, the bent ends can be placed into their respective control surface horns (you can also do this before gluing them in place to check the alignment). They are secured in place on the surface horns by gluing a small piece of extra pushrod housing material to the ends of the wires.
Rudder horn and pushrod. Elevator horn and pushrod.
Time to mount the servos. I used Hitec HS-55's, which are the servos recommended in the Hobby Lobby catalog. They fit perfectly, though you could probably also use HS-50's to save a bit of weight (about 0.16 oz total savings). However, when the wing is installed, it actually pushes down on the pushrods, causing some extra friction. I couldn't get rid of the friction; so I figured the higher torque of the HS-55's was the way to go (and it turns out they work well).
The pushrods are visible at the rear of the wing saddle. The wing will push down on them when it's mounted.
As I said earlier, there's no way to adjust the linkages on the pushrods (because there are no linkages). That means that everything must be adjusted by the positioning of the servos. To accomplish this, the cutouts in the servo tray are made extra long. The servos themselves are first mounted (using a bit of CA) into their own little ply sub-frames. The servo/frame is then placed into the overly large slot in the servo tray. With the pushrod hooked up to the servo arm, the servo/frame can be slid fore or aft in the tray until the control surface is in neutral. Once everything is lined up, the frame gets glued to the tray with a CA.
A servo in its sub-tray. Servos and pushrods in position.
Once I was satisfied with the movement of the rudder and elevator, I set about hooking up the tow release. There's obviously no room for a dedicated tow release servo, so the Habicht is designed to have the release coupled to the elevator servo. A small pre-bent pushrod gets attached to the elevator servo arm, on the same side as the elevator pushrod. The rod goes forward, into the small tube in the nose, where it exits the fuselage and engages the wire hoop. So, whenever the pilot inputs up elevator, the release pushrod is pulled back away from the hoop. The idea here is to set it up so that full up elevator will pull the pushrod back far enough to completely disengage from the hoop, thus releasing the tow line.
The release pushrod that came with the kit was actually a bit too short to reach the servo arm and still engage the hoop. This wasn't too much of a problem, as I was able to take some similar sized metal wire I had on-hand around and bend it to the proper shape, then cut it to a good length.
The elevator servo, with the elevator pushrod (left) and the tow release pushrod (right) attached.
The instructions suggest setting up the release so that it disengages at full up elevator. I decided to get a little tricky with my computer radio, though. I set up the elevator throw so that pulling the stick back all the way would give enough up throw for flying, but still not allow the tow release to open up. I then programmed a mix in my radio that would move the elevator servo full travel only when I pulled back on the spring loaded trainer switch…more like a true release switch. Of course, hitting the switch would still cause full up elevator, but at least there would be no chance of accidentally causing a release when too much up elevator was applied.
There's not much construction involved with the wing. There are a couple of thin ply dihedral braces that need to be glued into a slot on the bottom. I had to sand these to fit first, and then I used wood glue to glue them in place. I've found that wood glue works well to bond wood to foam. Any excess glue that gets squeezed out of the slot can easily be cleaned up using a damp rag. After the braces are glued in place, a flat piece of precut ply (sort of a spar cap) is glued over the slot. I used epoxy for this step.
The Habicht's wing has a squared off leading and trailing edge, but I decided to round off former. I doubt this has much aerodynamic effect, but it looks nicer.
Next, the instructions show how the wing fairing, which was cut out in the very first step, is to be glued to the top of the wing. The wing is then supposed to be glued to the fuselage. When I trial fit the wing to the fuselage, though, I found a problem…the fairing did not sit flush with the top of the rest of the fuselage. The problem is that the wing saddle is not cut with the dihedral angle of the wing accounted for. I had to sand the edge of the saddle to an angle that matched the dihedral, so the wing would sit flat, and thus a bit lower. I also had to sand out a notch for clearance of the ply spar cap on the bottom of the wing This allowed the upper fairing to fit flush.
I was about ready to glue the wing to the fuselage, but I was somewhat concerned about getting the center of gravity correct. I began to suspect that I might have to place either the receiver or the battery under the wing to get the plane to balance properly. Just in case that was necessary (and it was), I placed a small balsa bulkhead behind the main former. That way, I could place the battery or the receiver in the space under the wing without worrying about it sliding backwards into the tail.
I added this small balsa bulkhead below the wing saddle.
I glued the wing to the fuselage with five-minute epoxy. Once that was done, I checked the fit of the wing fairing again. I did a bit of sanding along the bottom of the fairing to get it to fit flush, and then glued it in place with epoxy.
The Habicht comes with some self-adhesive decals, which are easily applied, and add a nice finishing touch. It also comes with a small clear plastic windshield. Unfortunately, I did a bit of a bad job installing this. My suggestion for installing it is to first remove the small "spikes" that are included at the bottom of the windshield (I attempted to use the spikes to anchor the windshield into the foam before gluing it, which did not work out too well). Just tape the windshield in place at the corners to hold it down temporarily, and then apply a thin bead of medium foam-safe CA around the base. Finally, remove the tape, and apply a bit of glue underneath the corners.
I set the elevator for the recommended throws, and set the rudder for as much throw as I could get, which is my standard practice for rudder-elevator controlled planes.
My intention was to use a very small 150MaH NiMh battery pack for the Habicht. This would be compact enough to fit easily in the nose, and hopefully not cause the plane to be too nose heavy. Unfortunately, the pack took a bit longer then expected to arrive, so I decided on a temporary compromise, and used a physically larger 110MaH NiCad pack for the initial flights. This pack was large and heavy enough that I had to place it under the wing in order for the plane to CG correctly. I placed the Great Planes ElectriFly park flyer receiver in the nose. The plane was a touch tail heavy, but placing a couple pennies up in the nose fixed that.
110mAh NiCad in place under the wing. Balsa stick glued to the former is a temporary measure to keep the battery in place. Looking forward into the nose from behind the cockpit. The tow release pushrod can be seen to the left, and the receiver to the right. There is not a lot of room, but it does fit.
Final flying weight with the large battery was still less then 4.2 ounces, a touch under the 120 gram specified weight. Wing loading at this weight is 3.90 oz/sq foot.
A while after the first couple flights, the little NiMh square battery pack arrived. It turns out that I still had to place the smaller pack underneath the wing to get the plane to balance out. I also had to remove a small portion of the leading edge where it passed through the fuselage to get the battery to fit through the opening in the former (in retrospect, a flat pack would have worked better). Overall, it shaved off a few grams of total weight.
The 110mAh NiCad (below), and 150mAh NiMh pack(above).
The NiMh pack, under the wing. Tissue paper holds it in place.
I did not want to aerotow the Habicht on its maiden flight for obvious reason. Instead, I figured I'd either look for a really small slope to test it out on, or else fly it at one of my normal slope sites when the wind was really light.
An overcast afternoon without much wind arrived, so I figured it was a good time to test the Habicht. Turns out that the wind at the top of the slope was a bit more then I would have liked for this (5-10mph, I'd guess), but I still figured it wouldn't be too bad.
A gentle toss and off she went. The CG appeared to be just right, and it required just a tad of down elevator trim. I must say there were no surprises. The Habicht behaved exactly as I would expect a lightweight rudder-elevator sailplane to fly. It flew quite smoothly at first, cruising back and forth across the slope, and seemingly right at home in the light lift (it looked quite nice too). Rudder authority seemed good, though I did find myself using a lot of it, especially when I was flying fairly close to the slope.
The wind started to pick up and get a bit gustier. There was no problem controlling the little glider, but I started noticing the wings flexing up and down quite a bit more then they had been, so I decided to bring it in. I ended up landing in a patch of wildflowers. I'd definitely advise landing the Habicht on something soft. Although the plane's light weight probably makes it unlikely that it will break outright too easily, it would still be easy to puncture the thin fuselage should it land on a sharp stick.
On another light-wind day, I flew the Habicht at a different slope to wring it out a bit more. This time, I removed the pennies from the nose to move the CG back a tiny bit. Starting off in 3-4mph wind, the Habicht again had no problems. The wind increased a bit, so I decided to try a few aerobatics. Rudder rolls are pretty much impossible...the plane is so light that it just can't pick up enough speed in a dive to complete a roll. Loops are possible, though they tend to be very tight and not too scale looking, again because of the almost non-existent weight. I had the most fun just cruising it low, skimming the flowers and brush on the face of the slope. I had to laugh when the occasional bee or insect would chase the plane as it flew by.
One thing that surprised me was the penetration this little plane has on the slope. Now, obviously this thing is no speed demon, and the wind was still relatively light. Still, I had halfway expected to be flying backwards most of the time. This was not the case. I don't think that flying on large slopes is what the Habicht is really intended for, though. It would probably be much more at home above a small grassy hill or sand dune in a gentle breeze.
Now I felt I was ready to do what I had originally had in mind for the Habicht: aerotow! Before I begin, I should say that this was definitely a learning experience. Neither my friend Ken (the tow plane pilot), nor myself had any experience aerotowing. Consequently, we did lots of stuff wrong, despite my efforts to read up on the subject beforehand.
The tow plane we used was Ken's Hobby Lobby Speed 400 Super Cub. I was a bit worried that the tug might not be able to fly at a slow enough speed that would be safe for the Habicht. The Habicht has no spar beyond the inner section of the wing, so flutter and/or structural failure was a concern if the tug flew too fast. As a bit of additional insurance, I put a length of fiber tape on of the bottom of each wing, from root to tip, hoping this would give a bit more strength.
Belly view. Fiber tape reinforcement can be seen on the bottom of the wing.
The Cub was converted into a tug by adding a tall towing mast on top of the wing, right at the center of gravity (which is, as it turns out is WRONG). The hollow carbon fiber mast had a notch on the top to accept the towline. A servo-actuated music wire rod running through the tube engaged the towline. If an emergency release was required, the rod moved downward, disengaging the line. The mast itself was so tall because my friend was worried that the towline might foul the balanced rudder of the Cub. That extra height and the mast's position would prove to be an issue later.
Hobby Lobby Super Cub tow plane. Note large towing mast above the wing: It's way too tall and in the wrong position.
The final preparation was to build a dolly to use for the initial ground roll of the glider. Taking a clue from the Hobby Lobby website, I made a small two wheel dolly, using scrap blue foam, a carbon fiber rod for an axle, popsicle sticks, and some light foam wheels.
With everything ready, we had only to wait for the wind to die down before our first aerotow attempt. When conditions were good, we set up on a small, rough, asphalt service road in the middle of the field. Following the Habicht's instructions, we used about 15 feet of monofilament line as our tow cable.
The Habicht rests on its dolly, waiting for the next tow..
The first aerotow was a semi-success. We set the Habicht and Cub up on the runway. Ken eased the throttle forward on the Cub, and the Habicht/dolly began rolling forward. Ken added a tiny bit more power. The Habicht tilted forward as if it were a wheelbarrow, then promptly pulled itself off the dolly and skidded onto the ground. Good thing it had that plywood skid! The little glider was now being dragged across the asphalt, but doing so in a pretty stable fashion, so I told Ken to just keep going. A few seconds later the glider lifted gracefully off the ground and assumed the classic high tow position behind the tug.
The tug lifted off smoothly and accelerated, while the Habicht remained stable, without any substantial wing flex showing. Tug and glider continued to climb out, and Ken began a slow turn to the left. At this point, there was a break down in tug/glider pilot communication. I expected Ken to complete a 180-degree turn, and then fly parallel to the runway for a bit before turning back the other way. Instead, he continued his turn, intending to circle continuously. At some point, the tug turned a bit too steeply, and the towline must have gone slack. When the slack was taken up again, the Habicht was yanked violently nose down, and then rolled inverted. In the meantime, the tug, being attached to the towline by a huge lever at the c.g. (that tall mast), got yanked nose up. I hit the tow release...it worked! The Habicht almost immediately flipped upright and assumed a slow glide, as if nothing at all dramatic had just happened. The tug immediately recovered as well, and both airplanes landed without harm. Okay, chalk that one up to experience.
Did I say both planes landed without harm? Well, not quite. The glider yanked the tug hard enough that the tow mast was nearly ripped from it's mooring on top of the wing. So, w e make a few changes for the second day of aerotowing. The tug's tow mast was cut down to a little less then and inch high. On the dolly, I added some "stoppers" toward the front of the cradle to block the leading edge of the glider's wing and prevent it from pulling itself off too early. Finally, we extended the towline from 15 feet to about 25 feet.
Sailplane and tug on the runway.
Weather conditions on the second day were not quite ideal. It was overcast and there was a slight and variable breeze. We tested the air out first with our electric gliders, and it seemed smooth, with the occasional patch of very weak lift, and little or no sink. The problem was that the breeze was blowing across our little runway.
As light as the crosswind was, it proved to be a problem for our tug. The Cub, while a good flier in its own right, has no ailerons, and it is not an ideal glider tug...but it was all we had. We set up the planes on the runway, and waited for a lull in the wind. When it arrived, my friend powered up the tug and we were off. The glider rolled forward on the dolly about 5 feet, at which point the glider and dolly "wheelbarrowed" again. This time, instead of the falling off the dolly and getting dragged across the pavement, the glider jumped into the air. Not exactly a smooth liftoff, but it worked. Unfortunately, a gust of wind arrived just as the tug was leaving the ground, picking up one of its wing tips and sending it veering off the runway. It appeared the Cub wasn't going to make it, so I hit the release switch, and the Habicht immediately let go of the towline. Of course, hitting the release also gives full up elevator, and the Habicht ended up pointing it's nose straight up into the air, stalled, and went straight down into the dirt. In the meantime, the tow plane continued into the air successfully. The nose of the Habicht was a bit creased, but there was no other damage (later on, I followed the instructions, and removed the creases with careful application of heat from a sealing iron and a bit of light sanding).
Once the Cub had returned, we hooked it up again and waited for another lull. This time, we decided that the Cub should use more power on take off. We had been worried about overstressing the glider's wing, but it appeared pretty solid in the previous days' aerotow. We figured it would be safer to take off with a bit more airspeed, given the prevailing conditions. Another lull arrived, and the tug powered up quickly. The Habicht leapt from its dolly again, just as the tug once again veered off to the left. This time, though, the tug got off the ground cleanly and I remained on tow. Ken established a stable climb and we were off.
As Ken began the first turn to the left, I applied a bit of right rudder to keep the glider on the outside of the turn and keep the towline taut. This, in combination with the increased line length, smoothed things out quite a bit compared to our first aerotow flight. We continued parallel to the runway for a while, and then Ken started another left turn, which again went smoothly. This was fun! The tug and glider continued upwards in one more racetrack pattern before I toggled the release.
The Habicht released cleanly. As you might expect, the sink rate of the Habicht is pretty low, and it smoothly floated around up there for good amount of time, especially considering there was little if any lift to be found. As I got low enough to start think about a landing, I encountered some very small patches of lift. I was already a bit too far downwind to really work the lift, and I was worried I might not make it back (the wind was picking up at this point). However, based on the amount of vertical movement I was seeing as I flew through it, I'd say it wouldn't take very much of a thermal to quickly get the Habicht to speck-out height. The main limitations would be the plane's small size and the lack of visibility this imposes, not too mention the light weight and not exactly slick wing profile, which would prevent it from penetrating upwind very far. Despite the headwind, though, I made progress, skimming across the access road and landing almost right in the spot where I had started. Finally, a fully successful aerotow!
The next flight was pretty similar to the first, including the rather sketchy takeoff. When we got to a good height, I waited to release until the planes were almost overhead, going upwind. It looked like they were going fairly slowly, but I didn't really take the increased wind speed into the equation. Consequently, when I released, the glider had quite a bit of airspeed. Since hitting the release also results in full up elevator, the glider immediately did a complete loop. Oops! Must remember to slow down the tug a bit before release next time. The actual gliding flight went very smoothly again, and ended with a landing on the runway.
When we were done flying, Ken commented on how hard it was to control the tug while towing the glider. The Cub had a tendency to go nose up when the power was increased. Also the rudder was over controlling the Cub, to the point where it would turn much to steeply when even a small amount was applied. I took a look at some aerotowing information on the Internet and in some magazines, and realized that the tug had the tow release mounted in the wrong place. It should have been at or near the trailing edge of the wing, not on the center of gravity. This was probably the reason for the Cub's weird behavior. We decided it would be a good idea to move the towline mounting point back, but unfortunately, we did not have time to try it out before this article was finished.
In the mean time, here are a few things we learned about aerotowing. 1). It's lots of fun. Actually, the towing part can be more fun then the gliding part. 2). Mount the towline release on the tug near or behind the trailing edge. 3). A longer towline is better then a shorter one. 4). Finally, if you use a dolly, don't cut corners: use four wheels, not two. Although we were unable to try it, I'm fairly confident that if you are taking off from short grass, you may not even need a dolly.
I definitely got a lot of enjoyment out of the little Habicht. It's a neat-looking glider that flies quite well, especially for such a tiny plane, and a scale one at that. If you want a scale airplane for a very small slope, you'll want to take a look at the Habicht for sure.
The whole electric aerotowing thing was quite a lot of fun. It was a bit challenging at first, but the Habicht performed wonderfully. I think if you are into both gliders and park fliers, and you have a suitable field, you owe it to yourself to give park-aerotowing a try!
For more information on aerotowing, check these sites:
Aerotowing primer: www.scalesoaring.net/tow.html
Aerotow releases: www.sailplanes.com/asher.htm
Aerotow links: www.scalesoaring.net/aerotowsheet.htm
|Jun 27, 2003, 10:56 PM|
They were areo towing it with a Fatty Sparrow biplane last weekend at SEFF. It was so cute I had to land to watch it.
If your into building there is a similar size plane called the Mini Kestral. About 1/2 the weight
|Jul 02, 2003, 12:46 PM|
Great article Brett!
I think I will have to try this Aero-Towing indoors in a gym, no thermals, but I find the walls much more challenging anyways. I was pleased to hear that it would do well on a small slope in light lift too. Texas is too flat for most slopers, maybe not this one though.
Excellent review, I enjoyed it!
|Jul 02, 2003, 05:20 PM|
I want a thermal follow-up
Enjoyed your article very much. I had a Lo 100 which was also very cute small foam glider. I could get it to slope and could "High start it" with someone running with the tow line hooked under the wing and also enjoyed the fun of aerotow using a New Timer with the line secured around the wing riser. Worked very well. Release was the same as your Habicht. The Lo 100 was a dog on hand toss and on any type of flat line flying. I usually beat the tow plane to the ground while I was trying to thermal and he was trying to land. I am interested if you actually get yours to thermal and in what type of thermal activity.
Again, very nice review and very informative but I hope you post a follow-up here when you get some more time on it. I have two Habichts now. One is 1.5 meters wing span and the other is 2.2 meters wingspan. The large one aerotows and features a pilot with a head that rotates from side to side with the rudder (Seperate servos on a y harness.) Keep up the good reporting. Mike Heer
|Jul 03, 2003, 03:08 AM|
I haven't had a chance to aerotow it again, though hopefully Thrusday I will. I'm not quite sure how it will work as a pure thermal airplane, if only because it can't range very far, being so light and small. I suspect that if you get into a thermal it will go up very fast, but if you stumble into sink, it will come down very fast.
We are also toying with the idea of using the Cub to aerotow a 60" HLG size plane, and if that works, maybe of creating a semi-scale glider to tow up. Something that would look reasonably scale, yet have the wing loading of an older HLG.
|Jul 03, 2003, 02:42 PM|
Yeah, problem is there's not really a place to put it, as the servos and pushrods are right there in the cockpit. I thought about adding a foam profile figure, but then it'd just be in the way when I need to turn the Rx on and off.
|Jul 04, 2003, 02:17 AM|
Another update. We flew again today, this time with the towline mounted in the correct place on the Cub. My friend reported that the handling was much improved, though it still tended to turn too steeply to the left. We are thinking that maybe the Cub needs more right thrust.
We've got the take-off technique pretty much down. Starting with more power is better, as it tend to pull the dolly much straighter. When try a very gradual start the dolly tends to follow the grain of the asphalt and wanderer around a lot more.
We again flew in the evening, so thermals were not exactly abundant. We have been just too lazy to fly in the morning when thermals would be all over the place. Based on how the Habicht flew today, I'd still stand by my original statements regarding it's thermaling ability.
|Jul 04, 2003, 09:13 AM|
I enjoyed your detailed accounts of trying to tow the Habicht. All I kept thinking to myself was maybe they should change the name...just re-arrange some letters at the end.
|Sep 02, 2003, 01:16 AM|
Joined Jan 2003
Wonderful article and thanks for the tips! I've been towing a LO-100 for a few months now. The LO-100 is made by the same people who make the Habicht, just a little bit bigger. I'm comtemplating picking up the Habicht as well.
Just for comparision, I'll explain my towing scheme. I use regular thread as a towline. It seems plenty strong enough and is cheap. My tow-plane is a homemade styrofoam cub with a GWS IPS drive. The cub's wingspan is about 30". I can tow with the regular IPS B drive but towing is easier with the dual B. We've been towing with the thread just taped to the towplane on top of the wing at CG. From your recommendations, I'll try it at trailing edge next. I don't use a dolly or anything. I just let the glider drag! It works just fine. The glider will stay on the ground and just drag behind the towplane. Once I feel there is sufficient speed, I pop the elevator up and the glider pops in the air. I let the glider build up airspeed skimming the ground and then let it rise above the towplane. This seems to work well. I guess I have to do this because my towplane has very little power. Because of this lack of power, the position of the glider very much CONTROLS the towplane! Both pilots have to talk to each other and let each other know precisley what they are doing. We also figured out that slight opposite rudder on the glider helps smoothen the tow in turns (as you figured out too).
One little trick I did:
I have a computer radio. I programmed the end points for the elevator less than maximum. Then I programmed the snap roll switch with maximum elevator throw and zero throw for rudder. So when being towed up, I can give full deflection on elevator (helps when I pop the plane off the ground) and not worry about releasing the towline. When I want to release, I just tap the snap roll switch!
|Sep 02, 2003, 01:33 AM|
Joined Jan 2003
With my LO-100, I have succesfully thermaled many times, Thermal activity has to be good though. I would have thought that it would thermal better than it does. However, I have thermaled the LO-100 for a flight that lasted over ten minutes. Came down early as my 80mah batteries started to worry me! Need to look at lithiums for this plane!
And slope is fun with this little plane! I have slope soared at real slope sights with REAL wind. The only thing I have done is added about a buck in quarters as ballast when the wind really blows. The plane penetrated better than expected.
|Sep 02, 2003, 01:33 AM|
|Sep 14, 2003, 06:21 AM|
I bought a Habicht from Hobby Lobby on the strength of the pics and info in the catalogue because I too had built a Lo 100.
It was pretty obvious thet both planes were from the same Mfg, and I found the Lo 100 easy to build using ZAP O foam freindly CA.
I have found this is the only Foam CA which will set without using Zip Kicker, but it takes about 2 mins, and is then very strong.
I didn't use the air tow bits as I bought the plane for those "Almost no wind" days on the slope.
I glued four 150mah NiMh cells together with hot melt glue in a lozenge shaped block and glued them into the curve of the nose with double sided foam tape, after wrapping in paper masking tape. When it was in place and the CG was confirmed I dribbled some HMG around it for good measure.
I used a GWS Pico 4 RX with two CS micro -10 servos and NO RX switch---the battery being pluged straight into the RX before flight.
The C G was right on with no further ballasting needed.
With this experience behind me and being very pleased indeed with the Lo 100, I am looking forward to the Habicht when it arrives next week.
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