Flight B/C

Locked
coachchuckaahs
Coach
Coach
Posts: 676
Joined: April 24th, 2017, 9:19 am
Division: B
State: NM
Has thanked: 1 time
Been thanked: 95 times

Re: Flight B/C

Post by coachchuckaahs »

CypherKat wrote: March 12th, 2023, 6:59 am https://drive.google.com/file/d/1BSGzer ... sp=sharing

https://drive.google.com/file/d/1uvC9tf ... sp=sharing

https://drive.google.com/file/d/1p-bK2U ... sp=sharing

hello! I am back after a round of test in my school gym.

For each of these flights we got the rubber to 100 winds, and dewinded 5 turns on the winder, we don't have a torque meter sadly so I cant speak for that. We used the same rubber on these which later snapped, but it came in on 1.90 g and around .63 g/in. we messed around on CG placement but I wanted some tips on hitting the 2:30 mark. States is this Thursday, so we'll try ot get one final testing in before comp.
Thanks
Another student pm'd me with a very similar description, so I will answer here to benefit many.

The issue they reported was that they got to 12 consecutive flights and rubber finally broke, but no torque meter. It appeared, as I am inferring here, that students are winding the same number of wind and unwind on a single price of rubber and expecting the same results. That does not happen. Up to a point, perhaps 6 flights or so, each wind will break in the rubber more, be and if you wind to the same torque you will get considerably more winds. Winding same number of winds will result in much reduced torque, and thus less climb and disappointing letdown. After that the rubber may get tired and start to lose performance, up until it breaks. If winding hard, we rarely see much more than 6 uses of a motor.

The only way to get consistency in performance would be with a torque meter. A simple wire one is available from J&H for $14. I believe Ray Harlan's site may have instructions on making your own.

The only other way to get predictable performance, though not necessarily optimum, would be to track flights and winds each flight on the motor, be and then make identical motors with identical wind history for your event. Probably easier to just make a torque meter.

Coach Chuck
Coach, Albuquerque Area Home Schoolers Flying Events
Nationals Results:
2016 C WS 8th place
2018 B WS 2nd place
2018 C Heli Champion
2019 B ELG 3rd place
2019 C WS Champion
AMA Results: 3 AAHS members qualify for US Jr Team in F1D, 4 new youth senior records
User avatar
randomdogonapc
Member
Member
Posts: 70
Joined: December 6th, 2022, 7:04 pm
Division: C
State: OH
Pronouns: He/Him/His
Has thanked: 27 times
Been thanked: 11 times
Contact:

Re: Flight B/C

Post by randomdogonapc »

Hi, I’m back.
So, I went flying today, and I noticed a large change in my flights. Without changing anything from the previous flights, the plane would climb at a normal rate to the same height as my previous flights, but then it would instantly descend rapidly without any cruise. What could’ve changed to cause this? Also, what should I do about it? I’ve checked every glue joint, and all is well there, but the propeller blade on one side had a little crack next to the spar. Thanks in advance.
just a random dog on a pc
coachchuckaahs
Coach
Coach
Posts: 676
Joined: April 24th, 2017, 9:19 am
Division: B
State: NM
Has thanked: 1 time
Been thanked: 95 times

Re: Flight B/C

Post by coachchuckaahs »

randomdogonapc wrote: March 16th, 2023, 4:03 pm Hi, I’m back.
So, I went flying today, and I noticed a large change in my flights. Without changing anything from the previous flights, the plane would climb at a normal rate to the same height as my previous flights, but then it would instantly descend rapidly without any cruise. What could’ve changed to cause this? Also, what should I do about it? I’ve checked every glue joint, and all is well there, but the propeller blade on one side had a little crack next to the spar. Thanks in advance.
Two things come to mind:

1. The crack in the prop is definitely a problem. The Ikara props do fatigue and crack, and once they crack they will not hold pitch. You may be able to reinforce it with a little CA glue
2. You do not discuss rubber at all. If the rubber is the same piece, depending how you wind, it could just be more "broken in" or even tired. If you are not winding with a torque meter you are not likely adjusting the winds for each usage of the rubber (more winds on each new flight

The rubber "width", or density (g/in) sets the letdown. A well used piece of rubber will act like a thinner piece of rubber. The launch torque determines to a large extent the initial climb. Climb can be accomplished on slightly thinner or thicker rubber because you can set launch torque appropriately to get climb.

It is also possible something else shifted on the plane, or more likely warped due to temperature or humidity changes, but typically such issues would be amplified at high torque.

So start with your prop blades.

And note my next post...

Coach Chuck
Coach, Albuquerque Area Home Schoolers Flying Events
Nationals Results:
2016 C WS 8th place
2018 B WS 2nd place
2018 C Heli Champion
2019 B ELG 3rd place
2019 C WS Champion
AMA Results: 3 AAHS members qualify for US Jr Team in F1D, 4 new youth senior records
User avatar
randomdogonapc
Member
Member
Posts: 70
Joined: December 6th, 2022, 7:04 pm
Division: C
State: OH
Pronouns: He/Him/His
Has thanked: 27 times
Been thanked: 11 times
Contact:

Re: Flight B/C

Post by randomdogonapc »

Sorry about that, my rubber is 13.5” loop of 0.068g/in density. It’s 0.094” width. It’s pretty much an exact replica of the rubber that I used on the flight that I PM’d to you. This was it’s first few uses, I used it 3 times today.
just a random dog on a pc
coachchuckaahs
Coach
Coach
Posts: 676
Joined: April 24th, 2017, 9:19 am
Division: B
State: NM
Has thanked: 1 time
Been thanked: 95 times

Re: Flight B/C

Post by coachchuckaahs »

SO Just posted a new FAQ. In this one a person asked if they could have a spare wing, or a spare prop, in lieu of a second plane, or swap parts between two planes as needed. The answer was No. The reasoning is that the plane is checked (in box) in its flight configuration, and changing parts violates this.

What does this mean? If you have a well-used Ikara prop (plastic blade on a plastic spar), I would be sure to go into a competition with a new prop, rather than a tired old one. Otherwise you risk a cracked prop, and would have to go to a backup plane since you cannot replace the prop.

If you are building your own props, be sure you are using a robust spar structure. Some spars we have used for soft flaring are susceptible to breakage.

I have seen events in less-than-ideal settings (auditorium overflying the seating (chairs); atriums with pillars and other odd shapes, ballrooms with chandeliers, etc)., This presents a new risk if you cannot change your prop. Know your venue (AC on or off, obstacles such as chairs, girders, etc.), and sometimes you will need to change your game plan, giving up some time for robustness or stability. Or have two planes complete and ready.

Coach Chuck
Coach, Albuquerque Area Home Schoolers Flying Events
Nationals Results:
2016 C WS 8th place
2018 B WS 2nd place
2018 C Heli Champion
2019 B ELG 3rd place
2019 C WS Champion
AMA Results: 3 AAHS members qualify for US Jr Team in F1D, 4 new youth senior records
bjt4888
Member
Member
Posts: 872
Joined: June 16th, 2013, 12:35 pm
Division: C
State: MI
Has thanked: 0
Been thanked: 51 times

Re: Flight B/C

Post by bjt4888 »

randomdogonapc wrote: March 16th, 2023, 4:27 pm Sorry about that, my rubber is 13.5” loop of 0.068g/in density. It’s 0.094” width. It’s pretty much an exact replica of the rubber that I used on the flight that I PM’d to you. This was it’s first few uses, I used it 3 times today.
Random,

Need more data. As Coach Chuck mentioned too. What are the winding specs (max turns, max torque, backoff turns, launch torque and turns remaining). And yes, use CA glue to repair the prop.

Brian T
Last edited by bjt4888 on March 17th, 2023, 12:12 pm, edited 1 time in total.
User avatar
randomdogonapc
Member
Member
Posts: 70
Joined: December 6th, 2022, 7:04 pm
Division: C
State: OH
Pronouns: He/Him/His
Has thanked: 27 times
Been thanked: 11 times
Contact:

Re: Flight B/C

Post by randomdogonapc »

Winding specs:
1.2in/oz max torque
0.5in/oz launch torque
60 back off turns
200 turns remaining(yikes)
Breaking turns for this particular motor is about 1,880
1425 turns

This is the thickest rubber that I have so I’m fairly sure that there’s a problem with trim or joints that can’t be changed by just changing the rubber.
just a random dog on a pc
CypherKat
Member
Member
Posts: 16
Joined: January 8th, 2023, 4:24 pm
Has thanked: 1 time
Been thanked: 1 time

Re: Flight B/C

Post by CypherKat »

Second Place at States!!

Thanks everyone here for all the help and I've had a blast for the last 5 years. So many awesome memories I will never ever forget!
These users thanked the author CypherKat for the post:
pumptato-cat (March 17th, 2023, 4:43 pm)
User avatar
pumptato-cat
Exalted Member
Exalted Member
Posts: 340
Joined: June 15th, 2022, 11:04 am
Division: C
Pronouns: She/Her/Hers
Has thanked: 103 times
Been thanked: 77 times
Contact:

Re: Flight B/C

Post by pumptato-cat »

Okay... Everything securely glued down, I decided to do some glide tests. Was very confident that everything would work out.
Nope. If I reduce wash-in to nearly nothing, it'll turn very sharply to the left. If I move the shim by 2mm to increase wash-in, it starts going very um VIOLENTLY to the right. I don't know what else to do at this point. Nothing's broken-I'm sure of it.

If I reduce wash-in to nearly nothing, that's the only way I get left turns. Except the plane refuses to climb(no matter how much I increase incidence by--and if I go too far with incidence, the wing joints begin to crack), and the turn is very sharp, resulting in a tiny circle. No matter how much ballast is added to the nose, the circle will not widen. If I increase wash-in, the plane turns sharply to the right. Flight results in a wobbly straight line, and the plane turns to the left or to the right indecisively.

This is without the propeller--I don't really know what to do at this point. I'll switch wings with my old plane and see if that helps some, but I'm just about ready to give up with this one...
anything'll fly if you throw it hard enough
bjt4888
Member
Member
Posts: 872
Joined: June 16th, 2013, 12:35 pm
Division: C
State: MI
Has thanked: 0
Been thanked: 51 times

Re: Flight B/C

Post by bjt4888 »

randomdogonapc wrote: March 17th, 2023, 1:21 pm Winding specs:
1.2in/oz max torque
0.5in/oz launch torque
60 back off turns
200 turns remaining(yikes)
Breaking turns for this particular motor is about 1,880
1425 turns

This is the thickest rubber that I have so I’m fairly sure that there’s a problem with trim or joints that can’t be changed by just changing the rubber.
Random,

Another possibility is the propeller shaft. Very rarely, something happens to the plastic bead or plastic bearing surface. Try a little powdered graphite on the bead and bearing surface. Powdered graphite is a standard hardware item used to lubricate locks. Even better, use the stuff the they sell for pinewood derby racing.

If this is the problem, replacing the bearing and plastic nose button is a good idea.

Brian T
Locked

Return to “Flight B/C”

Who is online

Users browsing this forum: No registered users and 0 guests