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Rktman

Eric
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How about some modeling clay (non-hardening) on the tip of the light wing? If you like it, seal it in with some c-a or replace it with small slugs of lead solder (cold; drill holes, press the solder in and c-a in place). Removing weight is most desirable, but adding weight where you want it is often easier. This also lets you zero in on the problem by eliminating lateral imbalance as a contributor.
If you've built a warped, or twisted, wing, then it can take some work to get it straight. Ya, maybe cut or break it and re-glue. Then fill and balance again.
Thanks for the suggestion but I already added all my trimming weight to the lighter wing to get the CG where it has to be for a stable glide...I can't add any more weight without throwing off the CG.
 
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Rktman

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Eric,

This might be a "crazy idea" to help adjust the necessary angle on your flap . . .

Insert a loose-fitting rod ( a 3/8" - 1/2" dowel ) into the aft end of the airframe . . . Use an electric fan to simulate "glide speed airflow" . . . Point the glider into the air-stream and adjust the flap angle until the glider is behaving as desired.

Not a "perfect solution", but it does give you a "working theory. A "real" Wind Tunnel would have a cluster of tube to smooth out the airflow from the fan.

https://apogeerockets.com/education/downloads/Newsletter252.pdf

Read TR-5, at link below . . .

https://estesrockets.com/wp-content/uploads/Educator/2845_Classic_Collection_TR-TN.pdf

Alternate idea : ( Maybe consider a pair of deploy-able Ailerons, one on each wing, to correct problem. )


Dave F.

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Thanks Dave, the alternate idea (flap/aileron) is the one I'm working on. Spent the day thinking about it and I think I've ironed out the details for flap retention, actuation, and angle control.
 

Rktman

Eric
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Eric,

This might be a "crazy idea" to help adjust the necessary angle on your flap . . .

Insert a loose-fitting rod ( a 3/8" - 1/2" dowel ) into the aft end of the airframe . . . Use an electric fan to simulate "glide speed airflow" . . . Point the glider into the air-stream and adjust the flap angle until the glider is behaving as desired.

Not a "perfect solution", but it does give you a "working theory. A "real" Wind Tunnel would have a cluster of tube to smooth out the airflow from the fan
Too bad I can't just use the swing test -- or hang it out the car window haha. :p
 

Ez2cDave

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Too bad I can't just use the swing test -- or hang it out the car window haha. :p
LOL !

However, that did give me another idea . . .

If there is a day with enough wind, it might be possible to "fly it on a tether", like a towline glider. You could temporarily attach a hook ( paperclip ? ) . . . It would only require a few feet of "towline" ( fishing line ? ).

That would let you get the flap angle "in the ballpark" . . . Thoughts ?

Dave F.
 

mikec

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At any rate, some roll imbalance is a good thing.
I also had to add weight to one side to get mine to turn, and even with the amount I have, it doesn't turn very well (see the video I posted before.)

Built stock, anyway, the design appears to be very forgiving. On one flight, I had the canard break completely off on one side and it didn't fly that badly even then.

At some point you may have to just fly it and see what happens.
 

Rktman

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LOL !

However, that did give me another idea . . .

If there is a day with enough wind, it might be possible to "fly it on a tether", like a towline glider. You could temporarily attach a hook ( paperclip ? ) . . . It would only require a few feet of "towline" ( fishing line ? ).

That would let you get the flap angle "in the ballpark" . . . Thoughts ?

Dave F.
Good idea and wish I could but at almost10 oz it would probably take 30+ mph winds to get it airborne like a kite. Of course, I could wait till next hurricane season to try...:rolleyes:

Cool hard hat btw. Were you an NAR official at some point? I may have to try tossing the glider to see what it does (1st and only time I tried it I had to hold it with both hands and try to throw it like a javelin because it's so big and unwieldy. That must've been a sight. Went all of 12 feet before denting the nose on something hard in the grass (fortunately easily fixed).
 

Rktman

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I also had to add weight to one side to get mine to turn, and even with the amount I have, it doesn't turn very well (see the video I posted before.)

Built stock, anyway, the design appears to be very forgiving. On one flight, I had the canard break completely off on one side and it didn't fly that badly even then.

At some point you may have to just fly it and see what happens.
I'm going to try hand-tossing it one last time first. You probably know how difficult lobbing that big glider is. The one time I did try I couldn't give it enough forward speed to get an idea how it flew. At any rate, I'll do what I can to fix the imbalance but in the end, the only way to see how it behaves is to fly it. I've been reluctant only because it's an original kit and no longer available--kinda like not wanting a 350 lb guy to sit in an antique chair to see if it'll collapse or not.:eek:
 
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Saluki

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Try hand lunch from a tall step ladder or from the back end of a truck.
 

Ez2cDave

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Good idea and wish I could but at almost10 oz it would probably take 30+ mph winds to get it airborne like a kite. Of course, I could wait till next hurricane season to try...:rolleyes:

Cool hard hat btw. Were you an NAR official at some point? I may have to try tossing the glider to see what it does (1st and only time I tried it I had to hold it with both hands and try to throw it like a javelin because it's so big and unwieldy. That must've been a sight. Went all of 12 feet before denting the nose on something hard in the grass (fortunately easily fixed).
Eric,

I don't think that much wind velocity is needed, but you would definitely need to be above Stall Speed for the glider . . . With that said, March tends to be quite windy.

That hardhat is from "back in the day". I have often served as RSO ( Range Safety Officer ) over the years . . . The hardhat was sort of a "tongue in cheek" way of poking fun at flyers. I have seen other hardhats with rocket parts glued to them to simulate a "through & through" penetration, like Steve Martin with his famous "Arrow"

Dave F.

 
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Rktman

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Eric,

I don't think that much wind velocity is needed, but you would definitely need to be above Stall Speed for the glider . . . With that said, March tends to be quite windy.

That hardhat is from "back in the day". I have often served as RSO ( Range Safety Officer ) over the years . . . The hardhat was sort of a "tongue in cheek" way of poking fun at flyers. I have seen other hardhats with rocket parts glued to them to simulate a "through & through" penetration, like Steve Martin with his famous "Arrow"

Dave F.

Gotta love it, it's classic. Really like visual puns that need no explanation.
 

Rktman

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Nope.JPG
Glad I slept on this because I relented and went back to a simpler solution than a pop-up flap: move the trim weight out to the starboard (lighter) wingtip edge and add some nose weight to compensate for the rearward CG shift. Because of the swept wings, I found I could reduce the amount of aft weight required so that far less nose weight than I expected was needed to keep the CG in the right spot (only about a gram).

Although the Thunder still has a roll bias toward the port side, it's nowhere near as bad as before. Judging by previous comments on the thread that the Thunder is somewhat forgiving of roll imbalance unless it's really severe, I'm more comfortable now that it'll do tight turns vs a death spiral. Have to admit that sometimes my solutions can be overly complex.:rolleyes: Simpler solutions tend to be the best, and in this case I lucked out since there was virtually no change in weight (278g with an expended E15 vs 277.8g with an empty D12).
 
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Ez2cDave

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Eric.

Sounds like you may be ready for a test flight . . . fingers crossed !

Dave
 

TDSapp

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I'm going to try hand-tossing it one last time first. You probably know how difficult lobbing that big glider is. The one time I did try I couldn't give it enough forward speed to get an idea how it flew. At any rate, I'll do what I can to fix the imbalance but in the end, the only way to see how it behaves is to fly it. I've been reluctant only because it's an original kit and no longer available--kinda like not wanting a 350 lb guy to sit in an antique chair to see if it'll collapse or not.:eek:

Rktman, I am not sure what area you are from but do like the guys just learning to Hang Glide. Find a nice big field with a long sloping hill in it. You can get a much better glide out of it and if it does take a nose dive it is not as bad as tossing it off a cliff or launching it without knowing.

Tim
 

Rktman

Eric
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Rktman, I am not sure what area you are from but do like the guys just learning to Hang Glide. Find a nice big field with a long sloping hill in it. You can get a much better glide out of it and if it does take a nose dive it is not as bad as tossing it off a cliff or launching it without knowing.

Tim
Still considering it. There's only one park with a long grassy slope I know of...though it ends in a large reservoir or pond at the bottom.
 

TDSapp

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Still considering it. There's only one park with a long grassy slope I know of...though it ends in a large reservoir or pond at the bottom.

Here is hoping that you did not build it so well it glides into the lake. :)



Tim
 

Ez2cDave

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Eric,

I have been giving this a LOT of thought . . .

NOTE : Just because the glider may behave okay in a carefully-controlled hand-toss, there is no guarantee that it will do so, when launched !

Let me clarify . . .

I am concerned that, at speeds below Stall Speed ( Apogee, for example ), that the Glider might "fall off on a wing" and go into a Death Spiral, before it gains sufficient airspeed to glide normally. I don't believe that the ECEE THUNDER has sufficient "recovery characteristics", following a Stall, particularly with a strong Left-Right imbalance.

Just my thoughts . . .

Dave F.
 

Rktman

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Eric,

I have been giving this a LOT of thought . . .

NOTE : Just because the glider may behave okay in a carefully-controlled hand-toss, there is no guarantee that it will do so, when launched !

Let me clarify . . .

I am concerned that, at speeds below Stall Speed ( Apogee, for example ), that the Glider might "fall off on a wing" and go into a Death Spiral, before it gains sufficient airspeed to glide normally. I don't believe that the ECEE THUNDER has sufficient "recovery characteristics", following a Stall, particularly with a strong Left-Right imbalance.

Just my thoughts . . .

Dave F.
Thanks Dave, appreciate the concern. Coincidentally the issue was still on my mind this morning so I spent some time adding more weight to the lighter wing (3 grams). Now the imbalance is barely discernable, but hopefully it favors its port wing just enough to get it to turn in a wide circle.
 

Ez2cDave

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Thanks Dave, appreciate the concern. Coincidentally the issue was still on my mind this morning so I spent some time adding more weight to the lighter wing (3 grams). Now the imbalance is barely discernable, but hopefully it favors its port wing just enough to get it to turn in a wide circle.
Eric,

It sounds like you have things well in hand, now . . . Hand-toss testing should be uneventful ( Just be sure to avoid a Stall - not enough time to recover ).

Dave F.
 

bobdog

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Am building this glider using hand-cut balsa components based on the templates. Am ready to install the canard, but want to check on the deflection of the canard "elevator" before gluing it in.

I have a maximum deflection of 17/32" at the trailing edge (less than what is allowed by the deflection clearance notch in the fuselage side pieces - Parts L and M). Is this sufficient? or do I need to relieve the "elevator actuator" (Part X) to allow more deflection?
 

Rktman

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Am building this glider using hand-cut balsa components based on the templates. Am ready to install the canard, but want to check on the deflection of the canard "elevator" before gluing it in.

I have a maximum deflection of 17/32" at the trailing edge (less than what is allowed by the deflection clearance notch in the fuselage side pieces - Parts L and M). Is this sufficient? or do I need to relieve the "elevator actuator" (Part X) to allow more deflection?
Due to uncooperative weather, I haven't been able to fly my Thunder yet to see how it behaves.
When I manually slide my piston forward, it tends to slide back a bit, probably due to the hinge's resistance, so that my deflection is 11/16" (or 22/32") measuring from the top of the fuselage to the bottom of the elevator's trailing edge. So it doesn't reach the bottom of the clearance notch on mine either.

Since my balsa piston fits loosely, I'm not certain how far forward it'll hold the canard flap. Judging from other piston-activated gliders I've flown, the ejection heat and crud tends to "lock" the piston in place at its furthest point of travel (which in my case is 12/16" max flap deflection). That's not much of a difference, so I intend to fly it, see how it performs, and make adjustments accordingly. Hopefully I'll get to fly it this Jan. 18th, weather permitting, and will post the results here.

If you get to fly yours before then, I'd appreciate knowing how it performed at your canard angle. Oh, and my compliments on hand fabricating everything. That's some mighty thick balsa and critical angles to have to cut through with a hobby knife.
 
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bobdog

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Lots of trimming, fussy sanding, shimming, and fitting to make it all work.

Thanks for the input. Don't see it flying until March or April due to the Wyoming weather.

Looking forward to hearing your results.
 

Rktman

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Am building this glider using hand-cut balsa components based on the templates. Am ready to install the canard, but want to check on the deflection of the canard "elevator" before gluing it in.

I have a maximum deflection of 17/32" at the trailing edge (less than what is allowed by the deflection clearance notch in the fuselage side pieces - Parts L and M). Is this sufficient? or do I need to relieve the "elevator actuator" (Part X) to allow more deflection?
Followup: If you haven't flown your Ecee yet, I'd suggest you make sure your canard flaps drop down as close to the bottom of the deflection cutout in the fuselage as possible without actually slamming down on it. I managed to get in a flight in February on an E15W-4 and my canard angle wasn't enough to keep the glider's nose up. It did a couple of dips and recoveries that resembled stalling but wasn't. It lost so much speed that it then came in nose down and vertical and ended up lawn darting hard. I've seen this kind of behavior before in my canard gliders and adding nose weight isn't the answer. Instead, you have to increase the flap's downward deflection.

My flaps fall short of the cutout. The "elevator actuator" that moves the flap down is a bit too thick so it contacts the bulkhead too soon, keeping the flap from dropping as low as it should. Had I known, I would have sanded the lever's forward edge before I glued the fuselage closed. The maximum deflection angle possible when I measure my model is 13.25° (approximately 11/16" from the flap top surface to the top surface of the fuselage).

If you've buttoned up your glider and can't make adjustments to the actuator lever, the only solution I can think of is to add trim tabs. It's worked on the gliders I've had this problem with. In this case, I sandwiched a thin piece of aluminum between two 1/64" pieces of ply to form the trim tab and glued the other end of the aluminum to the flap trailing edge. It allows me to bend the trim tab down incrementally until the problem is solved. Once the angle is right I just lock the trim tab in place with some thick CA between the flap TE and the trim tab.

I made a small slip-on angle gauge so I'll know the exact angle at which the trim tabs work as I try out different angles. Not strictly necessary, but I can tell at a glance what it is and jot it down in my build notes (helps avoid making mistakes if you rebuild the same model later). Oh, and a 4-second delay is a bit too long. I'd suggest a max delay of 3 seconds on whatever motor you use. Hope this helps.

Trim tabs-1.JPG
Trim tab angle guage.JPG
 
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bobdog

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Haven't flown it yet due to uncooperative weather. Sorry about the lawn dart.

Your suggestions are excellent. I will check to see if I can increase my canard deflection. Otherwise will try the trim tabs.

Thank you.
 

Rktman

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Haven't flown it yet due to uncooperative weather. Sorry about the lawn dart.

Your suggestions are excellent. I will check to see if I can increase my canard deflection. Otherwise will try the trim tabs.

Thank you.
Have a great flight 👍(or at least a better one than I did). It's a pretty impressive sight when it launches.
 
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