I’m a little late to the party on this video, however, I have to say this is one of the best glider/winching videos i’ve seen. Such a simple design using parts most rc pilots cane easily acquire. I’m not sure it would be less work than a bungee set up, but cool enough I think I have to build one. Thank you and take care.
She flys great and the winch... well a great design as well. Man I wish I was there with you. I have a Dynaflite BOT in the box so maybe I'll get it out and build it. Thanks for the inspiration.
Hi Steven. Try your tow hook at about half way between CoG and leading edge. You will find it will track better. The closer to the CoG you get, the more input needed to keep it straight. Think of it like elevator and CoG. Tail heavy - almost impossible to keep control. Nose heavy - very stable!
Very nice work Stephen, though, I have to admit ... after the amazing work on the BOT and the precision winch design, I was almost let down by the simplicity of the return post. Wait! I spoke too soon. Your newly designed return pulley is more like I expected! Beautiful in flight. I expect you've had many hours of enjoyment out of that BOT. There's no chance you're and engineer, is there?
Had one of these built from a wood kit back in the 70's. Great flying, magestic plane but because of the construction materials and methods was very heavy. It was, essenrially, a lead sled. More modern molding techniques would eventually be a game changer.
I don't know why this popped in my sidebar but glad it did. I flew RC gliders back in the 90's and really enjoyed it. Back when I was a kid (we flew towline FF gliders, RC was completely unaffordable to us back then) there was a guy in town who had a BoT he was building. I remember him waxing eloquently about it. Learning to coordinate rudder and aileron with elevator for turns was key for smooth flying for me. I started with some rudder mixed in with aileron and then started manually adding in more rudder with the stick as I got more comfortable. FWIW, my first thought was that the hook could stand going back for higher launches (as long as you could control it). However it is possible to fold wings if you are too aggressive. One joy of a strong composite glider was less chance of doing that. (And I will add that I haven't flown in ~20 years, so likely much better sources of advice out there ;) ) And finally, thanks for this. Has me wanting to dust off my gliders and get back to it.
I have only just come across this video and if it is not too late i have a couple of suggestions. For a good winch launch the glider really needs to pull on the line and from watching your launches it seems that your hook may be a bit too far forward of the CG, as the climb slows towards the top and it does not come off the line easily. The only way to find the best position is to have a moveable hook - we used cup hooks straightened into a normal hook and screwed into a length of ply - 4.5mm min for this would be about right, with new holes being added to move the hook. this system was used on everything from floaters to fast and heavy F3b models and was very reliable.The other point I noticed is the lack of much rudder input on the launch - it will be far easier to control on the launch, and actually necessary with a rear hook position - to use a fair bit of rudder and the easiest way to do this is to couple the ailerons to the rudder - ie CAR. It will be necessary to use around 80% aileron into the rudder. It is easy enough to switch the coupling off with a dedicated switch if desired but I have flown all my gliders with CAR - from F3B to F5J and DLG with CAR active for the full flight, without a problem. i hope it is still flying and good luck with it.
Thanks. Some good advice. I did design the hook so it can be moved. I have also had suggestions to move it forward??? I will try the rudder/aileron mix. Thanks.
@@stephenhughcrisp Moving the hook forward of the CG will at first stabilise the model in yaw but will if taken further cause a periodic movement in yaw - very common in tow line FF models. Moving the hook closer to the CG increases the AOA. improving the climb but does require rudder input to control the flight. When trimmed the hook position on nearly all our models was almost directly under the CG. However move it back in small steps. Another point I noticed on reflection - I think you may be staying on the line for too long. The model should be flown off at angles to the ground of around 70-80 degrees, and this should result in a slight zoom. Cheers and good luck - it flies well.
Thanks John. I think you’re spot on regarding staying on the line too long. I think I need more practice and more rudder control before I start to move the hook. Appreciate your advice. Stephen
Nice to see an old design flying again. A friend of mine built a Bird of Time back when the design 1st came out (must have around been 78 or 79). Being a bit of an aerodynamicist, I thought the wing plan form poor, so I built my own design using the bird of time section. The two gliders performed similarly with a fast & exceptionally flat glide. This due to the thin low camber section afforded by the so-called Philips entry. In this respect the models performed as standard aero algorithms would predict. They were great on windy day as you had the speed and range to go search for lift. While a floater would struggle to get very far at all upwind. But on a still day, the floaters were pretty well assured to get better duration, especially if lift was scarce. While the floaters had a steeper glide angle, they were so much slower with their high camber wings, that their sink rate was less then the much faster bird of time, but the bird of time had much a better range to find lift if it was about. Your model surprised me a bit as I expected to see more polyhedral, believing the design to be rudder elevator & spoilers. Then I noticed you did an aileron version & then it all made sense. Now I’m unsure if my memory of the originally design being without ailerons is correct or not. Do you know?
Thanks for a very interesting insight to the Bird of time. Please have a look at the actual build video of my Bird of time and you will see that I added the ailerons which were not standard. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-2SF64ZTiPWE.htmlsi=ybJpvBXpfDHBA7wL I removed quite a lot of dihedral due to the addition of the ailerons
Well then you are using the extended chord of the outboard wing panels for that features original purpose, ailerons. In the early days of gliders, several designs initially had poor aileron response. The simplest fix was to replace the ailerons with broader ones, which resulted in the plan form that the bird of time has. By the time the bird of time was designed, the real reason for that feature had been largely forgotten & popular perception became that it somehow improves flight efficiency. It doesn't though, it's actually a small detriment compared to the 2 most efficient planform solutions by Prof Lidwig Prandtl. For subsonic flight: If the design constraint is the wing span, then the most efficient planform is elliptical, but if the constraint is the wing root bending moment, then the wing can be lengthened out to the zero-lift point by adopting geometric twist & taper that together results in what has been termed a "bell shaped lift curve". This rotates the whole reaction vector towards the tip to produce some thrust in a more efficient way than tiplets do. This solves the problem of adverse yaw & was greatly exploited by the Horton Brothers towards & then after the end of & after WW2 in their flying wing designs. Prof Ludwig Prandtl’s paper on this based on his lifting line theory was published just prior to the war. It was a double-sided single sheet paper that the world apparently missed the significance of. I came across all this in the 80s & it has been taught by NASSA in more recent decades though. There are several RU-vid videos on such model aircraft if you care to search. I say this to show that many people are mistaken about the Bird of Time plan form, including the designer apparently. It is a rather cool looking & recognised design though. @@stephenhughcrisp
Now that was realyl Cool!!!! I have flown rc since the mid ''70's but only messed around with one or two gliders. One was the "Windfree" and a "Schweitzer 126D" never got the hang of it for thermal flying. Just threw it off a hill and hoped for the best. But you made this look so relaxing.
Back in the early 80s the club built some winches using an old 50s Ford starter and a sewing machine peddle had some members make a frame from 1" steel square tubing another member turned the spools out of aluminum we used them for fun flights and contests I wouldn't be surprised if they are still in use they were bulletproof
I used stretchable silicon tubing. And it worked great. Had a parachute between the plane and the tubing. The wind would catch the parachute and lay the line back downwind once it detached.
Superb winch build and description. I've not flown off of winch, only highstart and hand-launch. I think possibly you may benefit from moving the winch hook slightly toward the nose- get it right and you should need little or no elevator input during a steady-wind launch.
Hi Matt. I think you are spot on. I was considering moving the tow hook forward slightly. I actually designed it so that I could do so. Try with 5 mm to start.
Enjoyed your builds and winch flying immensely. You are quite a talent. From my experience with full size sailplane winch launching, your winch speed is about 30 percent too fast, and the winch line is much too short. Cheers, keep up the good work!
Hi Yukon. Thanks for your comments. You are correct. In subsequent flights I have slowed down the retrieval speed (totally variable with the foot control) and achieved much higher launches. In addition, I also moved the return pulley further out (around 130 meters). I would imagine I achieved around 90 metres launch height on a windless day. I guess it could be more if there is wind. Still have a lot to learn about winch launching.
when you say the motor came from an electric bicycle, could you give me the brand, or a direction to get one and a foot pedal to actuate it. Great video, I would like to build one, thank you - Steve
Hi. I bought the motor off AliExpress. Here are the search specs: 24V 350W electric motor electric bike motor conversion Kit MY1016 MOTOR engine for electric bicycle/scooter/tricycle. Email me on shcrisp@gmail.com if you don’t have any success. Stephen
Hi From all the flights I can tell that you may look into the wings weights. It always wants to roll left which means that the left wing may be much heavier than the right one. Cheers from Poland
Hi 12-volt car long shaft starter motor, alum/ drum, car battery, metal frame on wheels that came into contract when lifted up, handle all worked with a key, I found people would turn up and start using it without asking first. Glider and builder of gliders 37 years
That's what our winches were ~25 years ago when I flew. Just a on/off foot switch to a solenoid. You tapped on/off to regulate speed. A bike hub used as the turnaround. I had a rubber 'high start' for when one of the club winches wasn't there.
Looks good. Remember that the line stretch is the main thing in launching. Ease off once climb angle is established and use the wind to get max height. Weaving will work to get max final height. Well done.
Thanks Andrew. This is the first time ever that I have used a winch, so I appreciate your advice. Yes the line stretch is what catapults it into it’s climb angle.
@@stephenhughcrisp As with a highstart you can actually further stretch or in your case with a winch take out more line as you get higher. Wind speed increases surprisingly much with height. (usually estimated at 10 knots for each 100 foot which seems a lot!) On a 5kt day with practice you can release behind the launch point. I use a captive hook so can turn with the wind and circle at height if I want. Rudder has best effect going up.
Excellent. Thanks Andrew. That’s really good information. I obviously need to become more confident and need a lot more practice. I had read that you can actually fly to glider like a kite to the full extent of the line.
@@stephenhughcrisp once you have enough speed off your hand-launch to safely recover should a pop-off occur (lots of pre-tension helps here), you can pull back on the elevator to maximize your height and speed off the launch. It's counterintuitive, but adding tension and pitching up actually increases your speed (and altitude) by increasing the arc of your flight path. Fullsize sailplane auto-tows and winch launches use the same technique... pull back to increase airspeed while on the line. A properly-executed launch will put the glider high, directly over the turnaround, with a fully-tensioned line (zoom launches can be attempted from this position, but that's another topic). I think you'll find you have much higher launches with this technique... just make sure you have enough speed to begin with! Good luck, beautiful build. I regularly fly my RES Bird of Time, it's a magnificent design.
Congrets Stephen, really nice work, both glider and winch! How about modifying the original plan to the bot you build? And offering for downloading? Thanks a lot and best wishes! Burt
Hi Stephen, its me again. How did you built the v-shape? In the middle ant the outer wing parts? Just straight in the middle and 5cm at the wingtips? Regards, Burt
Hi Burt. Actually I couldn’t remember so I just measured it. In fact I did build a dihedral in the central section. 2cm on either side. The outer sections have a further dihedral of 5cm each on top of this. Total dihedral of 7cm each side when fully assembled. But then you need the ailerons for stability.
@@stephenhughcrisp Thank you Stephen! I own a Graupner Mosquito and a Carrera Optimus, both Oldtimer of the 70‘s. Unfortunately I don‘t really like the look while flying because of the v-shape. Your BOT looks much better! Actually I‘m waiting for a rib-set (from Edinburgh/Scotland)😉 Regards, Stephen
@@bernhardkuppers5743 ha ha. Happens to the best of us. I also don’t like the “v” look. I also don’t think it’s very efficient and that’s why I reduced the dihedral so much.
@@stephenhughcrisp just in case it's not known to some, the dihedral is needed to be able to turn (roll) without ailerons. It's the dihedral that couples the rudder (yaw) to roll. Dihedral also helps with stability.
