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4 Metre Glider Scratch Build

What should I build next?


  • Total voters
    7
  • Poll closed .

Jackson T

Well-known member
Well done!

Get that brake turned on and you're gonna have trouble getting her down on a warm day!
Yep! Landing is probably the hardest part of the flight, she doesn't want to come down! I fly in a huge farm paddock that is like a kilometre long and half a kilometre wide, so at least I don't have to worry about hitting stuff. I didn't think about idling the prop as an airbrake before, good idea!
 

Craftydan

Hostage Taker of Quads
Staff member
Moderator
Mentor
Just be careful with that. If you do use it, brake to slow, but not to stall.

As the plane slows, that big draggy fan on the front starts acting like a forward fin, cutting into your yaw stability.

Poor yaw stability in stall is no fun . . . unless you like spins.

. . . and a spin a few feet off the ground can dig in that long wingtip. Hard. :(


Alternatively, spoilers can be added with minimal carpentry and covering rework, and reduces your lift EXACTLY where you need. Core a few thermals up to a speck, but when you get tired of the long approach, spoilers are a near-ideal way to instantly steepen your glideslope while retaining full control.
 

TooJung2Die

Well-known member
I decided to put some heat shrink over the joints.
That's a good idea. I often use wire Z-bends on the ends of pushrods made from carbon rod, bamboo or thin dowel. You hold the wire to the pushrod with a piece of heat shrink. The wire end will be tight after shrinking but you can slide the wire to fine tune the length of the pushrod. After it's just right a drop of thin CA glue on each end of the heat shrink locks it in place. The CA wicks in under the heat shrink a long way and makes a very strong joint. You can also do this to join two lengths of wire, one short with the Z-bend. I find it hard to make a Z-bend in exactly the right spot so being able to fine adjust the length is helpful.

I love flying gliders but like you and your 4-meter I find the hardest part is landing them. They don't like to come back to earth and are often flying faster next to the ground than they look way up in the air! My gliders have ailerons so it helps a lot to mix spoilerons on a switch to reduce the glide ratio. When you've had some fun flying it you might take Craftydan's suggestion and add spoilers.
 

Jackson T

Well-known member
Just be careful with that. If you do use it, brake to slow, but not to stall.

As the plane slows, that big draggy fan on the front starts acting like a forward fin, cutting into your yaw stability.

Poor yaw stability in stall is no fun . . . unless you like spins.

. . . and a spin a few feet off the ground can dig in that long wingtip. Hard. :(


Alternatively, spoilers can be added with minimal carpentry and covering rework, and reduces your lift EXACTLY where you need. Core a few thermals up to a speck, but when you get tired of the long approach, spoilers are a near-ideal way to instantly steepen your glideslope while retaining full control.
Thanks for pointing the yaw stability problem out, I didn't think of that. I may do some high altitude stall tests with the prop idling just to see how it goes, but I'll probably just land it normally. Thanks for your advice, I wouldn't want to find out the tip stall problem the hard way while coming in to land :). I really want to learn how to thermal, but I normally fly near sunset cause that's when I can find consistently low winds and bearable temperatures (good old Australia). Maybe I should build a more manageable sized glider with ailerons for thermalling.
 
Last edited:

Jackson T

Well-known member
That's a good idea. I often use wire Z-bends on the ends of pushrods made from carbon rod, bamboo or thin dowel. You hold the wire to the pushrod with a piece of heat shrink. The wire end will be tight after shrinking but you can slide the wire to fine tune the length of the pushrod. After it's just right a drop of thin CA glue on each end of the heat shrink locks it in place. The CA wicks in under the heat shrink a long way and makes a very strong joint. You can also do this to join two lengths of wire, one short with the Z-bend. I find it hard to make a Z-bend in exactly the right spot so being able to fine adjust the length is helpful.

I love flying gliders but like you and your 4-meter I find the hardest part is landing them. They don't like to come back to earth and are often flying faster next to the ground than they look way up in the air! My gliders have ailerons so it helps a lot to mix spoilerons on a switch to reduce the glide ratio. When you've had some fun flying it you might take Craftydan's suggestion and add spoilers.
That's a good idea with the pushrods. I connected the two pushrod pieces after doing the Z bend and putting it in the control horn just like you say, and it definitely made it easier. I may consider spoilers, but I'll probably just practice my landings for now :D.
 

Craftydan

Hostage Taker of Quads
Staff member
Moderator
Mentor
Thanks for pointing the yaw stability problem out, I didn't think of that. I may do some high altitude stall tests with the prop idling just to see how it goes, but I'll probably just land it normally. Thanks for your advice, I wouldn't want to find out the tip stall problem the hard way while coming in to land :). I really want to learn how to thermal, but I normally fly near sunset cause that's when I can find consistently low winds and bearable temperatures (good old Australia). Maybe I should build a more manageable sized glider with ailerons for thermalling.
Coming out of an unusually long, hot summer (100F/38C today :p ), I can relate . . . but the thermal machine thrives on heat. All of my best flying was done on blazing hot fields with LOTS of hydration. Occupational hazard for the serious thermal hunter.

For now, keep flying at dusk. Your floating time will be hampered by the dead air (well, a little), but it at least lets you get a feel for how she behaves -- what is a fast/slow glide, where does she stall, how tight you can turn (you will be surprised how far on that wingtip you can lean), and where your preferred CG is (balance between inefficient stability and getting overworked by an over-agile plane). Keep taking it easy on her, but feel her out.

When you've got a wild hair and feel ready to enjoy the day, bump the CG forward a touch, launch a couple hundred ft (75-100m), and hunt! Hunt upwind/crosswind, and keep a watch on your plane -- if a wingtip bumps up on it's own, it's likely passing through rising air -- pull rudder quickly and lean into it 20 degrees or so. Circle once, and if you pick up altitude, keep circling, if not, flatten out and keep hunting. Through the circle, RIDE THE ELEVATOR TO KEEP THE FUSELAGE "LEVEL". If you're in rising air, the last thing you want to do is porpoise or stall out of it. As you climb, let the plane drift with the wind (the thermal drifts with the wind as well). If one side of the circle dips and the other rises, nudge your center toward the rising side to better "core" the thermal.

There's WAY more to it than that, but if you've got a good field, that's a primer to blind hunting those invisible beasts. Follow that and you'll see when you've stumbled over one, then hook it properly all the way to the speck (come back before that ;) ).

Do that a few times and we can start talking about looking for signs to know when/where to hunt.
 

Wildthing

Well-known member
I ended up joining the pushrods with sewing thread and CA glue. It looked a bit rough and messy, so I decided to put some heat shrink over the joints. I used some more of the guide tube externally to make sure the pushrods don't flex.
I do that lots and never had one come apart, the only thing I did different was the glue, I used Foam Tac or UHU Por because they aren't as brittle as ca glue and once you put the heat shrink on you are good as gold.
 

Jackson T

Well-known member
Coming out of an unusually long, hot summer (100F/38C today :p ), I can relate . . . but the thermal machine thrives on heat. All of my best flying was done on blazing hot fields with LOTS of hydration. Occupational hazard for the serious thermal hunter.

For now, keep flying at dusk. Your floating time will be hampered by the dead air (well, a little), but it at least lets you get a feel for how she behaves -- what is a fast/slow glide, where does she stall, how tight you can turn (you will be surprised how far on that wingtip you can lean), and where your preferred CG is (balance between inefficient stability and getting overworked by an over-agile plane). Keep taking it easy on her, but feel her out.

When you've got a wild hair and feel ready to enjoy the day, bump the CG forward a touch, launch a couple hundred ft (75-100m), and hunt! Hunt upwind/crosswind, and keep a watch on your plane -- if a wingtip bumps up on it's own, it's likely passing through rising air -- pull rudder quickly and lean into it 20 degrees or so. Circle once, and if you pick up altitude, keep circling, if not, flatten out and keep hunting. Through the circle, RIDE THE ELEVATOR TO KEEP THE FUSELAGE "LEVEL". If you're in rising air, the last thing you want to do is porpoise or stall out of it. As you climb, let the plane drift with the wind (the thermal drifts with the wind as well). If one side of the circle dips and the other rises, nudge your center toward the rising side to better "core" the thermal.

There's WAY more to it than that, but if you've got a good field, that's a primer to blind hunting those invisible beasts. Follow that and you'll see when you've stumbled over one, then hook it properly all the way to the speck (come back before that ;) ).

Do that a few times and we can start talking about looking for signs to know when/where to hunt.
Thanks! I can't wait to catch a thermal now. My only concern is getting back down :LOL:.
 

TooJung2Die

Well-known member
I can't wait to catch a thermal now. My only concern is getting back down :LOL:.
Your concern can be justified. I haven't flown one but I've heard about "boomer" thermals that are like rip tide at the beach. They take your airplane where it wants it to go. You have an advantage with a motor, you can power your way out of one. I do most of my flying in the early morning before the wind picks up. As the sun rises the ground begins to warm and the thermals start forming. We have a chicken farm next to the field with large metal roofed barns. The metal roofs are consistent thermal producers. If there is a thermal close by there is going to be wind associated with it.

Don't worry too much about getting it down and out of a thermal. Like Craftydan says, they are elusive. When you do find one there is a thrill in climbing on free power. I am a rank beginner when it comes to thermal flying. Listen to Craftydan and I found some expert advice on YouTube. Your flying field looks like an excellent place to begin the hunt.
 

cranialrectosis

Faster than a speeding faceplant!
Mentor
Gorgeous build. I just saw the maiden and what an elegant craft you have built. That hand launch was perfect, the landing serene.

I think with all that green field and all the water in it, you will have no trouble finding thermals to dance with.

This has been an excellent thread and I applaud you and your build. Thank you for posting this on our forums @Jackson T .
 

Piotrsko

Well-known member
If it's stuck going up, use full up to stall it and spin it down with rudder. If that doesn't work (and sometimes it won't) you'll need to find the cold air "sink" that is feeding the thermal by hanging a turn right angle to current path and fly that for a while. Best is to not fly on days with low spotty puffy small clouds, or days that start cool in the morning then get hot or when you can smell the local dairy farm. Try to not fly after lunch or before dinner.
 

Jackson T

Well-known member
If it's stuck going up, use full up to stall it and spin it down with rudder. If that doesn't work (and sometimes it won't) you'll need to find the cold air "sink" that is feeding the thermal by hanging a turn right angle to current path and fly that for a while. Best is to not fly on days with low spotty puffy small clouds, or days that start cool in the morning then get hot or when you can smell the local dairy farm. Try to not fly after lunch or before dinner.
Yeah, I remember hearing that about spinning gliders out of thermals. One of my friend's friend nose dived his glider to get out of a thermal, but it didn't pull out of the dive :(. I'm a bit concerned of spinning mine, as I don't want to stress the airframe unless it's absolutely necessary. It should handle it, but I don't want to risk it if I don't have to. I read Matt Hall's (Australia's Red Bull Air Race pilot) biography, and on his first full scale glider solo, he went thermalling and then used the sink to get back down, while everyone on the ground was surprised that he could thermal. It's not normally taught before the first solo, so he wasn't expected to know how to, but he had flown with his dad since he was a little fella.