In the Whatsapp videos sent by Hitesh Kher and Karthick, the models dived downwards despite being balanced at the specified position. Subsequently cured by adding a small tab/wedge for up elevator.

The culprit is (lack of) decalage.

Decalage is difference between the angles of incidence of the wing and stab.

1. Zero zero when both are parallel (pic 1)
2. Positive when wing is at higher incidence than stab (pic 2)
3. Negative when wing is at lower incidence than stab (pic 3)

Negative decalage is like down elevator and makes the model dive despite correct CG. Reducing nose weight will not cure it. This is what had been happening with your models.

My experience is that a small amount (< 1 degree) of positive decalage is required for longitudinal stability.

Freeflight once mentioned to me that he uses zero zero setup. Probably adds a small up elevator wedge.

@WeekendFlyer : "The glider was flying well and am getting flight time of 2-3 seconds but its banking right.

Will try out after warping the rudder / fin a little bit in the opposite direction."

Very Good. Now that is a step in the right direction. I am glad that you made a decision to fly later when the breeze is not there. Very good.

Notes:
1) the photographs posted above by Mr. Iyer are terrific. Clearly shows the concept . Please ask questions that you may have.
2) Yes, i do build Zero-Zero. Then I adjust with tabs see photos below. See my video on trimming in the previous page the first full minute where I show my tabs.
3) i used to bend stab, rudder etc. but gave up on it as these bends are not permanent. They can change in as little as few minutes or the next time you go out to fly.
4) I use small pieces of matchstick to make the stab. I glue them on with a glue stick, as it is easy to remove and adjust if needed. Usually i just sand it at the field, if it too big a tab, with a nail file. This becomes a more dependable and permanent adjustment.
5) I have shown examples of my jet glider Canberra. It came out exactly zero zero and need more left rudder. So I put the tabs on the stab to prevent it from diving and a left rudder tab to make it glide to the left. These are very small tabs, about two playing cards thick. The second photo shows tabs at the bottom of my Lunchbox as I had too much positive decalage (Mr. Iyer photo #2).It used to loop so I had to put it on the bottom. If it is diving, put it on top .
6) Please see the video again on reply #111. He shows very clearly as to how he makes the tab and attaches it to the glider. He is an expert, so he uses CA right away. I use glue stick so if I made an error, I can remove it and put a new one.

Kindly requesting again: Can one of you make a WhatsApp group so I too can enjoy seeing you trim and fly. Would very much like to see your videos. Else as I suggested, put it on YouTube.

So much looking forward to your flying videos.

Found some good articles in my box Hopefully it will help you understand trimming better. What to do when ...?
This was for paper glider so he talks about bending. In your case, attaching tabs will be more consistent!

@Freeflight,

I have a small Whatsapp group 'Iyer's Young Aero Friends' but members seem to prefer interacting with me personally rather than in the group.

The problem with putting this Lunchbox build and contest in a Whatsapp group is that it becomes private and is no longer available to others on RCINDIA.

On the other hand, if everyone posts all their test flight on RCINDIA via YouTube, we will be swamped, and end up confusing onlookers.

Here's a suggestion for a via media:

1. Participants can post Youtube videos here selectively
2. They can send all their videos via Whatsapp to you and/or me.
3. My wife, the RC AUNT, has a Youtube channel - 'andiyerlko' where we post all our videos. (Her name is Anandi, and LKO is for Lucknow, where we stayed for many years. Hence andiyerlko)
4. From the Whatsapp videos I receive, I can select the relevant ones, post them on YouTube, and post the link here on RCINDIA.
5. You could do the same, selecting some to illustrate your point.

I'll try tonight/tomorrow

Regards

Hitesh Kher intial flight, and flight after trimming.

Karthick Ashwath, initial flight and flight after trimming

Dear All,
Wonderful guys. great job. So happy and enjoying seeing these. Thanks so much Mr. Iyer for posting.

@Hitesh, terrific glide test. You are ready for the catapult launch. Others: See his video, very nice and try for that glide. Hard push and nice glide. I am not sure if you pushed the glider to right. Try again, but this time push it a little bit to the left. It should turn left.

Also in your first video, it appears that you launched it too high. Keep the same bank angle and launch a little lower. That perhaps will get rid of the stall. Try again and let us see your video. See hand sketch, upper one on reply # 110.
Looks like you are trying hand launch. Work on your launch angle and I am sure you will get a very long flight.

@Karthick: Congratulations. Perfect lunch and bank angle. Very Very good transition You got it. You will hit a minute on this. Couple of recommendations, if I may please. After transition, now is the time to start tuning the glide phase. What it appears to me is that it is diving fast, and too the right. Based on the video , you need to put a small tab on your rudder, left side, you had called it correct. Then try again, as it should make the glider turn left after transition. You want right climb, you got it, left glide. Try it and give us another video. After you get the left glide, if it is still gliding fast, then remove a bit of clay, about the size of a pin head. Keep removing such small amount of clay every time, until your glider is gliding with the nose slightly up in glide phase. I am sure your glider will float.

So happy to see your progress. Enjoy!

Others, looking forward to see your trim videos.
Best Regards,

Quote from: K K Iyer on November 15, 2020, 10:11:19 PM

Hitesh Kher intial flight, and flight after trimming.

Wow! Cool ! Congrats Hitesh .

Just got a few videos from SI74.

Will upload on YouTube and post here tomorrow

@S174. Looking forward to your video too.

Quote from Mr Iyer's message:

"Here's a suggestion:

1. Participants can post YouTube videos here selectively
2. They can send all their videos via WhatsApp to you and/or me.
3. My wife, the RC AUNT, has a YouTube channel - 'andiyerlko' where we post all our videos. (Her name is Anandi, and LKO is for Lucknow, where we stayed for many years. Hence andiyerlko)
4. From the WhatsApp videos I receive, I can select the relevant ones, post them on YouTube, and post the link here on RCINDIA.
5. You could do the same, selecting some to illustrate your point."

Like your suggestion. Contestants, please send me a PM and I will give you my cell number to send the videos. Then we do as Mr. Iyer suggests.

SI74's test flight progress:

Initial flights - diving




Next. Launch too high. Still diving.




Then. Correct launch for test glide. Still a bit nose heavy.

Yes sir , I corrected it .

@Glidiator sir,

I know you're watching   

Await comments

Regards

Found two cans of this stuff while rummaging in the garage. Actually used for sealing watercolor or charcoal paintings. Can be used for crafts also . More important- water repellant.
Used it on trial on a piece of balsa 3sq cms. Original weight  0.10 GM's - after one coat - 0.16 GM's.
Will try it on the lunchbox - parts ready - will be assembled tomorrow.

@S174 : "Yes sir , I corrected it ." yes you did very well. Yes diving a bit.  But good throw and curves to the left.

So for everyone : In his case should he start moving CG back or put just a little more tab on the stab?

You have to think about it. If your CG is at the correct location, I would put a slight more "up" tab on the elevator. See if it cures diving and if it stalls very slightly at that time. If that slight stall is there, go for your horizontal catapult and then full launch up .

your goal now is to dial in the exact launch and bank angle to give you a smooth transition to glide. Then work on the glide.

As mentioned before, you will have to experiment with a good launch angle and bank angle. I would start where Karthick did in his second video.

This is so enjoyable to see you guys succeeding so well right away. You are doing well and you have an excellent kit from Mr. Iyer who did all the sanding and roughing part.

@KK
My connectivity is on  almost 24x7 either thru wifi or direct data connection
Yes have been watching the progress of various participants.
Free Flight and you are doing a great mentoring job.
Too many cooks will spoil the broth.
Moreover my practical experience in CLG is limited.
Will be fun to see how well Iam able to fly the model.
Anant

Something I should share that everyone experts agree.

To get the correct launch and transition, just adjust Stab incidence and rudder left stab, Leave every thing else alone.

Then work on the glide by ONLY adjusting the CG and tail tilt. In the case you did not add the tail tilt, put clay on the left wing to make a smaller (30 to 40 foot) circle. if the circle is too small, put a little clay at the right wing tip, it will open up the circle.

If it spirals (going in tighter circles) to the left in glide, increase the washin tab.

All adjustments made very small. Remember the free flight will develop your patience, not rush hurriedly and make mistakes. Also now is the time to recall that you do not make an adjustment based on one flight. Fly it 4 or 5 times, if it does the same thing, go ahead and adjust.

"Will be fun to see how well I am able to fly the model." looking forward to your flights .

"Remember the free flight will develop your patience, not rush hurriedly and make mistakes"

This is the most important lesson learnt through free flight.
Also one correction at a time so you are sure what change caused what difference in flight.

Free Flight -- Can stab tilt be created by giving a slight twist to the tail end of the fuselage. This is done in indoor rubber where ofcourse the tail boom is very thin and flexible. Though this correction won't be permanent.
Regards

@Freeflight, thanks for the encouraging words .  I was referring to the excess nose weight of my glider, which I corrected. When I sent my test flight videos to Iyer sir , he had pointed out the same . Now I think, will have to do more trimming  ,for a near perfect glide as Hitesh , by your suggestions. Thanks.

@S174: your last video is quite good. I am of the opinion that you need more up stab not CG. Your glider rises a bit when thrown and turn very good left.

Experiment and you will be your own teacher as you gain experience.

All three of you have done very well for the first glider ever in your career of model airplanes.

"Free Flight -- Can stab tilt be created by giving a slight twist to the tail end of the fuselage. This is done in indoor rubber where ofcourse the tail boom is very thin and flexible. Though this correction won't be permanent."

yes most definitely, but your keyword is : not permanent.

But the rest of you guys can experiment what Glidiator suggest. Experiment!

Quote from: Free Flight on November 16, 2020, 09:59:29 PM
@S174: your last video is quite good. I am of the opinion that you need more up stab not CG. .

Yes , I am gonna do that .

All has been quite for a while. Eagerly awaiting to hear of your experiences and video ,though videos are a lot of work for Mr. Iyer. Thanks so much, Mr. Iyer. Meanwhile, Perhaps contestants can posts photos, yes?