2nd Chuck - Lunchbox

Started by K K Iyer, October 08, 2020, 08:54:06 PM

Previous topic - Next topic

0 Members and 2 Guests are viewing this topic.

Free Flight

#100
So all said and done this how it all looks: Turns gently to the left at a distance of 30 feet from your launch.
If it turns to the left to sharp, remove clay from left wing tip that you put to create the turn. Not enough left turn, put a pin head amount of clay more at the wing tip lower part.

K K Iyer

CLARIFICATION- TEST GLIDE

Getting complicated? Let's simplify.

Freeflight is helping you set up for circling flight, which is the ultimate objective. Else it'll fly away.

However, one of my objectives is to introduce newcomers to setting up a model for straight flight, before anything else. Because many of them are building electric powered depron models with RC and having problems due to not getting the fundamentals right.

Let's get to the test glide.
What is it for?
To ensure that it flies straight down the glide slope, neither climbing nor diving, neither turning left nor right.

Glide slope? What's that?
My prototype Lunchbox, launched from eye level (5' or 1.5m) goes about 22'/7m before landing on the sofa (1.5'/0.5m)
So it goes 7m for 1m drop in height, or L/D of 7.

If all is well, from an eye level launch, it'll go 30-35 feet.

Hold it under the wing a bit behind the CG, or a bit ahead of the wing trailing edge.
Point it at a point on the ground about 30-35 ft away.
And launch it.

But at what speed?
Slightly less than what you'd use to throw a marble (kuncha) the same distance.

If you have balanced it fore and aft at 1.75" behind the wing LE, this is what will happen:

1. It climbs above eye level. Either launched nose up or speed too high
2. Dives and lands too soon. Launch too slow
3. Correct launch speed is when it doesn't dive, and doesn't climb above eye level

4. If it still dives, reduce nose weight
5. If it noses up, and then dives, add nose weight
6. Adjust nose weight till it flies down the glide slope.

Meanwhile it may turn left or right, due to slight misalignment of fin, or because the wing is not centered on or square to the fuselage.

If the turn is drastic, you'll have to recheck the alignment of the fin and/or wing

If the turn is mild, let it be, for now.

At this stage you should get a 3-4 second flight going straight or a bit to one side, for 30-40 ft

I'll tell you more when you cross this stage.





K K Iyer

@freeflight

Please delay catapult launch techniques till I'm done with test glide and hand launch.

Only 4 have received kits.
5 more being despatched tomorrow, so they won't be ready to fly till the Sunday after this.

So a week of lull, perhaps

Regards

Free Flight

Mr. Iyer, Will do.

I am busy till next Tuesday anyways, so this helps.


SI74

Iyer sir , let him complete it in a stretch . All basic lessons in one thread ! And I'll bookmark this page forever ! I think I'll carry my training  with this glider even after this competition is over . So we will read his posts and yours and go forward . I missed my chance for the stab tilt this time because I had glued mine before reading his post on that .

K K Iyer

@Freeflight,

1. I'll try to make a short video on test glide trimming. That will conclude the test glide phase.

2. After seeing your catapult launches, I doubt if there'd be much interest in hand launch. So I'll defer that.

3. Rest of the kits sent, and should arrive in 2-3 days.

So it would be great if you can continue with the catapult launch guidance during this weekend if you have the time.

Regards



Free Flight

Dear Iyer sir,

Definitely will do. Seeing both my kids who have come home after a very long time, so busy this weekend. Will start again as soon as my Sunday evening comes along.

Thanks for making the glide test video.

Best Regards,

SI74

@Freeflight , please post a video of hand launch of your glider and the trimming you do . Thanks.

Free Flight

@ S174. Will make a video of my test glide and the launch. Will show the launch angle and bank very close. This week it is very cold and extremely windy (gust up to 25 mph) . So the first chance to make a video is Friday or Saturday this week.

Regarding your request for hand launch the glider. Since a few years I am launching with rubber band only as my arm gets pain after a few flights. But you youngsters should definitely try it. Before that, go to the gym and work up your arms. You need to give it a massive power launch to get the glider up about 100 feet.

Free Flight

#109
 Ok , before we go for the first launch, re check that a) Glide test is correct , in the sense when you point the glider a bit down and do a hard push, your glider will raise it nose and then go into a nice (not sharp) left circle. b) CG is correct c) no warp has developed in the wing , stab and rudder.

Preliminary rubber pull test : Before you actually catapult the glider (for a right handed person), hold the glider by its tail, hook the rubber at the nose, holding the launch stick in your left hand. Then assure that  the nose is  level to the horizon/ground  and assure that the wings are horizontal, not banked. Pull back only about 1 to 2 inches and let go. You should observe the glider at first raise its nose and turn gently (not sharp) to the the left.  It should not stall, dive or spiral in. If it does any of the the stall/dive/etc, go back and restart the glide test. DO NOT PROCEED WITH A FULL BLOWN LAUNCH  TILL YOU SEE A PERFECT GLIDE FROM THE HORIZONTAL LAUNCH.

Finally : The CLG Launch: there are three parts to this flight:
1) The Launch phase, will take around 2 seconds to reach the top maximum height. Here you launch with the nose high (about 70 degrees from the ground/horizon) and the right wing banked towards the ground.  
2) The Transition : You are launching the glider nose up (called the launch angle) and the right wing banked to the ground (called the bank angle). It is banked to compensate all the things you have built-in  to turn gently left, stab-tilt or small clay on the left wing, rudder off-set tab to the left and the washin-in wedge on the left wing. Once the glider reaches the top, it will do a half roll (meaning, the left wing will drop to level) and the glider should not loose any height.
The transition is fast, blink of an eye, shortest of all three phases. (you colored the bottom of your wings black, yes?).
3) The glide phase to the left. All your glide test hard work should pay-off now. This is the longest phase. (you colored the top of the wing red or orange, yes? to help you find it on the ground)

Analysis: So from your 20 second flight, you have about 2 seconds to reach the top, fraction of a second to transition, then the rest 18 seconds are in the glide phase. If you luckily happen to "pick the air" (means you launched it in a thermal) the glide phase will be much longer and maybe perhaps loose it out of sight (OOS) or your offering to the Thermal Gods (Hoong).  

See the diagrams below.

Free Flight

The Flight:

Free Flight

#111
A Video Paints a Thousand Words:

I am posting a link to J&H  trimming video. Best trimming video I have seen ( though many good ones out there).  Couple thing: Your launch hook is behind the stab not below, he talks about lead, you have clay. See his analysis : Hand glide, then horizontal rubber pull, then the banked launch. He shows transition very well and what to do when it is not exact. You did put sandpaper at the tail for consistent launch, yes? Consistent launch is the key. Once your glider is flying correctly, write down on the wing the launch angle and bank angle.

Observe his launch angle and bank angle. Yours will be similar not exact same, but not too far either. You need to experiment with both the launch angle and bank angle. If you build 2 gliders at the same time, their angles will be slightly different.

He also shows you how to make and attach trim tabs (Remember: matchsticks, blade, glue stick etc.)


Free Flight

#112
Next thing I will do is post my video of the Lunchbox. We will go through trimming situations there. After that I can post cause & effect table : If the glider does this look for that etc.

Please let me know if all of you are in the build phase, and ready for the glide phase.

Build light, but enough glue to be strong and build it accurate.

Take your time, please ask questions that you may have.

Please remind me later to go through the discussion as to things like :
a) Do I adjust CG or give more elevator?
B) Should I give less rudder or more washin ?
c) My favorite (took me a while to understand), my glider launches great, great transition but always flies straight, no turns. I have a rudder off set. What gives?  

SI74


Free Flight

#114
 I feel there is a slight stab tilt correctly on the left side (right side of photo). If so, then it is good.  Looks like a slight gap between the wing and fuse. May want to assure you have enough CA there so it does not come off. What is the weight in grams?

Looks good for sure.

Free Flight

PS: Looking forward to see everyone's initial photo.

SI74

@Freeflight , initial weight ( without clay ) 7.6 gms. There's not much tilt , even if ; it's meagre :( . There was a minimal gap bw fuse & wings , but applied enough CA and it's well bound now .

Free Flight

@S174: My first one weighs 7.2 grams that includes clay nose weight. Your glider will have good penetration in the breeze, it will not be easily blown away. However it will glider much faster. As the glider spends most of its  time  in the glide phase, your challenge is to get the glider as high as possible with a good transition, that is no loss in height at transition.

A meager stab tilt to the left  (left stab higher) when viewed from back is better than more. The plan calls for only 1/32" of tilt, very small.

How is everyone else doing? Any photos to share, please? weights?

K K Iyer


Free Flight

@S174: contacted a couple of my free flight friends. They clearly recall loosing the Lunchbox a few years ago at 8 grams flying weight. Catches thermals well at that weight too. You should be ok.

SI74

Ok, thanks for the comforting words .

K K Iyer

Since Freeflight is providing most of the input, what can I contribute?

Instructions in HINDI, as preferred by some!

TERMS
1. LE, leading edge, wing ke aage ka kinara
2. TE, trailing edge, wing ke peeche ka kinara
3. Fin, poonch ke oopar ka hissa
4. Stab, stabilizer, poonch ke neeche ka hissa
5. CG, centre of gravity. Jahaan balance karna hai
6. Trim tab. Tikoni dandi ka 1-2cm tukda. Flight ki disha modne ke liye. Aur mudhe samay andar wale wing ko sahaara dene ke liye
7. Trim. Ichcha anusaar udne ke liye adjust karna.

TEST GLIDE
1. Model ko CG aur TE ke beech neeche se pakdain
2. Model ko aankh ki level pe rakhain.
3. Fursh par lagbhag 30 ft ki doori pe nishana lagayen
4. Yaad rahe ki model ki naak uupar ki aur na ho, thodi neeche.
5. Ek kanche ko 30 ft phenkna ho to jidna dum lagega, usse thoda kum dum lagayain.

Seedha 25-30 ft gaya?

Nahin gaya to batayen ki kya hua.
Phir elaj bataunga...

K K Iyer

Can't understand why Dreamliner has not received his kit, sent on Monday morning.

Everyone else has received.

Since assembly needs only 5 minutes, hope everyone has assembled their models.

So far, only seen SI74's pic.

Look forward to build pics and testflight videos. Over the weekend perhaps?

hiteshkher

Very good sir i like, i hope also some one like in hindi  :hatsoff:

Aapne bahot sahi tarike se samjaya he
Thank you sir

WeekendFlyer

@Freeflight:  Your efforts are appreciable.  {:)} I didn't knew that a chuck glider needs so much trimming. 
Good that I haven't started assembling my glider.  I am totally new as far as chuck glider is concern.
Thank you for your guidance and keep it up.

Will post pictures of my "Lunchbox" soon.