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Author Topic: Trimming TLG  (Read 386 times)
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Sailaway
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« on: August 17, 2020, 09:57:04 AM »

Coming back to TLG after a very long time with the SB's Dynamo. I have his fuse (built in 1.5 degree incidence) and the plans from my original model.

My launches are flat and about 10 to 15 degrees up from horizon. The model wants to go up, very high, very slight turn to the right , stops at the high point then heads  back dart to the ground.

In CLG or old HLG, straight up and down meant give it a little incidence and the problem went away. Is it same for TLG?  I kept turning the screw out  and add small amounts of nose weight, the glider reached higher but then a lawn dart again.

In the hand glide phase, the model raises its nose and turns right. Just in full launch it the lawn dart appears.

I have made sure by sticking a tape to the pod that the boom is not moving (up or down) in launch, no DT.

Is there an easy way to measure boom incidence? And what angle / degree should i expect? I do have the specified up sweep on the the bottom of wing LE

Moreover, I do have a right rudder bent in  very close  near the the fuse, about 1/16" now.

I am guessing at the Right side washin. About 1.5 inch long, half inch wide, and 1/16" thick.

Thanks for guiding me,
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BG
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« Reply #1 on: August 18, 2020, 10:23:56 AM »

Where is your CG? it should be at around 50% ... your flight pattern sounds like it is under elevated with CG too far back .... add declage and nose weight to move the CG forward. This should result in a steep spiral climb with a transition at the top.

BG
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Olbill
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« Reply #2 on: August 18, 2020, 12:33:46 PM »

Are you right handed? If so the glider should climb to the left and glide to the right. When my indoor gliders were climbing to the right Kurt Krempetz told me that I was releasing too early. Holding on for another split second gave a left turn in the climb with an S turn at the top into a right glide.

I'm not an expert at TLG but all the launches I've watched follow this pattern.
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« Reply #3 on: August 18, 2020, 03:56:05 PM »

Bill makes a good point your spiral should be to the left if right handed or to the right if left handed (like me). Glide turn should be opposite.

BG
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Sailaway
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« Reply #4 on: August 18, 2020, 04:13:19 PM »

Thank you BG and Bill.

Will implement the changes later this week and report back.

CG is as defined on the plans. Kept that as constant and played with incidence only.

Bill, yes, will now deliberately hold a second more and assure definite launch to the left.

So the question is how does one determine the angle of incidence? If i consider the bottom of the pod as the datum , straight line, I find the the wing LE and TE are exactly the same height. So with that as a datum, I can measure the "up" in the boom at the the end of the stab from the reference straight line. So then tan theta would be the "up" distance divided by the length from datum. Now if that be correct, what is a good initial incidence that I should shoot for? 2 degrees, more for initial flights?

Once again, thanks for the guidance.
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dosco
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« Reply #5 on: August 18, 2020, 04:33:26 PM »

If I may throw a monkey wrench into your plans ... I noted with the Zweibox design, I found the CG location per the plan to be unsatisfactory. It results in a very nose-heavy condition. Of course it is possible my crappy building skills resulted in some sort of funny/unintentional decelage that required a different trim CG ...

Not sure that would be the case with your bird - I imagine it's a more modern design, and analyzed with more modern methods(?).

Cheers-
Dave
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Tmat
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« Reply #6 on: August 18, 2020, 06:09:13 PM »

It's very difficult to measure the decalage. So don't bother. You adjust the decalage until the CLIMB and recovery is the way it is supposed to be. Then you adjust the CG to make the plane glide correctly.
Same for TLG as CLG or old time HLG.

Tmat
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dosco
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« Reply #7 on: August 18, 2020, 08:53:14 PM »

It's very difficult to measure the decalage. So don't bother. You adjust the decalage until the CLIMB and recovery is the way it is supposed to be. Then you adjust the CG to make the plane glide correctly.
Same for TLG as CLG or old time HLG.

Tmat

Agree, 100%.
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Sailaway
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« Reply #8 on: August 18, 2020, 11:03:08 PM »

TMat, thanks for the tip. Will not spend time to measure the decalage.

So will go by the firm hand glide and assure that the glider raises its nose and lands like a floating graceful  landing going towards the right.

 Two questions here: Next if I glide it again but with a very hard yet a level throw,  the nose now raise very high, really climbs and comes down abruptly, not a graceful floating landing.(stall).  Second, the issue for me was that if I misinterpreted the glide to be "nice"  and then decide to maiden launch it with a full throw, it crashes and I am repairing.

Hence I was trying to measure the incidence, compare it to some empirical  benchmark for TLG to get a decent enough, non crashing maiden flight.

Is there a technique in the initial hand glides that can give me an assurance that it is OK for the first flight?

Dave, no problem about throwing a wrench. You are correct. However, this is Dynomite , a Stan B's design .The CG on his plans is usually within an 1/8 inch away.
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Olbill
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« Reply #9 on: August 19, 2020, 01:14:37 AM »

I have frequently been in indoor venues where it was necessary to have a right-right pattern for my catapult gliders. I've had some good results BUT trimming for a right-right pattern is very tricky. I don't think I'd want to try it with anything but a flapper glider.

The point of this is that when you have a left-right pattern the S turn at the top of the launch gives the glider time to slow down before it's starting to turn. I think the whole V-tail system was/is based on that type of flight profile. If you get your glide trimmed with the decalage setup that you currently have and can accomplish the left turn climb then the transition is going to have a much better chance of success.

At any rate the fact that the model is stalling from a hard level throw indicates to me that you have enough decalage.

If any of you TLG masters disagree with any of this then be sure to speak up.
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Sailaway
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« Reply #10 on: August 19, 2020, 07:16:30 AM »

" At any rate the fact that the model is stalling from a hard level throw indicates to me that you have enough decalage."

Thank you Bill. That was the confirmation I was hoping for.

Will test again tomorrow. Am now excited equipped with these fundamental knowledge.
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Olbill
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« Reply #11 on: August 19, 2020, 04:38:19 PM »

I need to back up a little about the decalage. I would trim the glide with the CG where you have it and THEN do the hard level throw. If the CG and the decalage are both out of whack then you could have a stall in the level throw even with inadequate decalage.

Do you have Stan's instruction sheet for the Dynomite? I may have it somewhere if you need it.
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Sailaway
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« Reply #12 on: August 19, 2020, 07:50:38 PM »

Hi Bill ,

I only have his plans. No instructions, so that would be great if you can share it.

I have the CG exactly where he recommends on the plan. Then i adjusted incidence to get a good glide. Glider floats well, raises its nose then with a slight right turn gracefully lands about 100 feet away. After that only, a very hard level glide the model goes very high followed  by a stall.  It is not way out whack situation. on the CG or decalage. 

Thanks again.
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Sailaway
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« Reply #13 on: August 20, 2020, 08:17:52 PM »

Good news.

Bill Thank you so much. Holding the glider just a second more to assure it is launched towards the left, did it. Was launching it flat (Right wing tip parallel to ground) and the nose up about say 20 degrees. The glider came "Alive" and shows a lot of potential.

Have to practice the TLG swing, just like golf. Quite a few throws were total washout, but now I learnt why they were a washout so I can learn what to practice.

BG, yes the CG was slightly off. In further trimming the CG came up just a bit forward to what was recommended on the plans. and a tiny bit more incidence (half turn)

TLG seem to like forward CG and hence a bit of incidence. But what is the function of the rudder bend to the right in TLG? For example, in CLG you glue in a bit left  in the rudder. Then perhaps a tiny more tweak for the CLG launch phase. So in the TLG is the right rudder turn for the launch phase or the glide phase?
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Olbill
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« Reply #14 on: August 20, 2020, 08:44:08 PM »

It was a lucky guess.
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Tmat
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« Reply #15 on: August 20, 2020, 09:20:03 PM »

But what is the function of the rudder bend to the right in TLG? For example, in CLG you glue in a bit left  in the rudder. Then perhaps a tiny more tweak for the CLG launch phase. So in the TLG is the right rudder turn for the launch phase or the glide phase?
Sailaway, for a right hander, the TLG is launched to the left and it glides to the right. So the rudder offset is to offset the left launch and to provide the glide turn.

Tmat
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« Reply #16 on: August 21, 2020, 07:45:30 AM »

TMatt,

Thanks for clearing the concept of the rudder tweak. So a teeny bit  of rudder bend goes a long way, just like in CLG, and the circle is closed in by adding weight to the the right tip.
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