Flight B/C

[pumptato-cat]

I'm back with yet another question.. D:
What do you guys use for o-rings? I somehow forgot to order them from FF(knew I was gonna forget something :/) and now I don't know where to get them from. I've heard of using nylon tubing and cutting them into little segments for rings, but I'm worried the sharp edges will cut the rubber or leave nicks. Opinions? (also, any places I can buy o-rings if there isn't another option? I really don't want to pay shipping again just to order 12 o-rings... and I don't think the FF kit provides o-rings. *sigh*)

[bjt4888]

I'm back with yet another question.. D:
What do you guys use for o-rings? I somehow forgot to order them from FF(knew I was gonna forget something :/) and now I don't know where to get them from. I've heard of using nylon tubing and cutting them into little segments for rings, but I'm worried the sharp edges will cut the rubber or leave nicks. Opinions? (also, any places I can buy o-rings if there isn't another option? I really don't want to pay shipping again just to order 12 o-rings... and I don't think the FF kit provides o-rings. *sigh*)

Cat,
Good questions. Freedom Flight sells the black hard rubber o-rings, but these are also a standard hardware item that can probably be found online in bulk. Sliced nylon tubing works well if you use “reverse-s” prop shaft hooks (sold by J&H and Indoor Free Flight Supply). Nylon o-rings do not work well on other hooks, in my experience (they get off center and try to climb off the hook). The main benefit of nylon rings is light weight. They weigh about 5-10 mg per pair and the black rubber rings are about 80-85 mg per pair. Also, the reverse-s hook automatically centers the plastic ring on the prop shaft rotational axis. For AMA events, I use only plastic. For my SO students, we use black rubber as they are easier to attach to the hook in the pressure of competition.

The Freedom Flight kit comes with 10 rings and the other company kits may come with them too. The rubber rings are sturdy and can be used repeatedly.

Keep up the good questions. Next comes the tricks and processes of flight trimming.

[bjt4888]

Cat,

Here’s a 50-pack for $9 plus shipping. Size 005 70-durameter Buna-N nitrile o rings are what you want 3/32” ID and 7/32” OD with 1/16” cross section. I didn’t shop around much so there might be better deals than this.

https://www.amazon.com/Standard-Buna-N- ... B0180EQGPU

Brian T

[pumptato-cat]

Thank you so much!!! I spent a while looking and just couldn't find any o-rings of the right size on Amazon, really appreciate your help!!
Yet another question(Sorry D:) :
1) how do you guys not break your planes? I just got my FF kit and it looks so fragile. . . terrified of breaking it on accident or snapping/denting a balsa piece. (if I do dent a piece, is that a major issue?)
2) Has anyone had issues with the motorstick bending? If you put in like 1800+ turns, wouldn't that put a huge amount of stress on the motorstick? It looks so thin and fragile... I'm not sure if it can hold that without snapping.

[jander14indoor]

You learn to be REAL careful. These planes ARE fragile, part of the skill you will have to learn is how to handle them, and frankly how to repair them as you WILL break them on occasion.
Some tips on handling.
- Common way to break them is when transferring from one person to another. You have to coordinate when one person holds and the other lets go or you will turn in different directions while still holding the plane and bad things happen.
- Once built, handle primarily by holding the motor stick. You shouldn't hold the plane by any other parts.
- Learn to move SLOWLY. Moving the plane fast is a good way to rip a wing off.
- Be careful where you set it down. A small wind will blow it off a table onto the floor where you can step on it.
- Don't grab it in mid air (until you become very experienced, and then remember to grab by the motor stick), don't chase it, don't run around it, don't let others do so.
- Frankly, don't let others handle it (unless they have built one with you and learned to handle it).
- Don't transport outside (or much at all) unless in a storage box and secure it in the box from movement. Don't put heavy things in that box.
- If you do drop it, don't try to grab it, let it fall, much less likely to get damaged.

The motor stick is typically the most robust part of the plane. That's why you handle the plane by the motor stick as recommended above. You can have issues with motor stick bending, which can make trimming a real challenge. Back some years ago there were kits with that problem.
But now most of the kit manufacturers know how to size them or reinforce them so it isn't much of a problem. One kit has Kevlar strings that act as trusses. Others might laminate Kevlar or carbon fiber on the stick to add strength. Still another might make it shorter and fatter.
Yes, a lot of turns are required, but the motors are so thin that they don't put an unmanageable amount of force on the motor stick.

Jeff Anderson
Livonia, MI

[bjt4888]

Thank you so much!!! I spent a while looking and just couldn't find any o-rings of the right size on Amazon, really appreciate your help!!
Yet another question(Sorry D:) :
1) how do you guys not break your planes? I just got my FF kit and it looks so fragile. . . terrified of breaking it on accident or snapping/denting a balsa piece. (if I do dent a piece, is that a major issue?)
2) Has anyone had issues with the motorstick bending? If you put in like 1800+ turns, wouldn't that put a huge amount of stress on the motorstick? It looks so thin and fragile... I'm not sure if it can hold that without snapping.

Cat,

Yes to everything Jeff wrote. I tell my teams that the locking lid plastic box is never to be opened unless we are practicing or they are t a competition. Anyone that wants to look at the airplanes can look through the closed box (so, yes, we’ll transport the “measurement box” inside of a locking lid plastic box this year). We role play telling parents, siblings, teammates, etc, “No, we can’t open the box for you to see. I’m the keeper and protector of the “scientific instrument” for the team”.

Also, don’t remove the airplane from the box when other people are too close. Ask for clear space around you, if necessary, in a competition.

Yes, they’re fragile, but when flying and when carefully handled, they do not break too often. We usually get through a whole season with zero breakage (with 18 students flying from 5 schools).

As for stick bending from rubber tension/torque; read my document linked in the earlier post carefully and watch the YouTube video of me winding a helicopter motor (see notes in the comments in the video about the difference between winding for helicopter and airplane). With airplanes, at typical gym ceiling height flying locations, you will wind the rubber motor fully and then “backoff” (reverse direction winding) to a desired launch torque. A .094” wide rubber motor can be wound conservatively to 1.2-1.4 inch ounces torque and a typical launch torque (after backing off around 150-225 turns) will be about 0.3-0.4 inch ounces. At this launch torque, a reasonable motor stick is very unlikely to bend to any significant degree. Reasonable motor stick would be 6.0 - 7.0 lb cu ft density and reasonable cross section like 3/16” width and 3/8” depth. As Jeff notes, longish motor sticks, like the Freedom Flight design, can be supported by a simple kevlar thread truss.

Good questions. Keep asking and keep researching. I tell my students to read the previous years forums to quickly build their knowledge base.

Brian T

[jander14indoor]

Slightly more technical discussion on motor stick bending.
- Really only relevant if you plan to get into designing your own plane. Most kits are designed to avoid any problems there.
- Or if you are building from a plan. Then you'll need to make sure that the balsa you select for you motor stick not just matches the size called out on the plan, but is also on the stiff side (balsa varies a LOT in its mechanical properties, like stiffness, see previous year forums for discussion on that, though we can cover it again if you have specific questions).

When you wind a motor, you build up TWO forces. The torque or turning force to spin the prop, and the lengthwise force that comes from the motor shortening as you build turns.
Remember Newton, forces always occur as equal and opposite reactions!
The torque force isn't really a problem in flight. It doesn't act between the ends of the of the motor stick, but between the freely spinning prop and the back motor hook. That force is then distributed along the motor stick ONLY to the wings, which have to react the torque to keep the plane level. That means the twisting force on the motor stick in flight only has a SHORT path and there is generally plenty of stiffness to deal with that.
More problematic is that axial force. It is always acting between the prop hanger and the rear hook. And the longer that distance, the higher the force and the less ability of the stick to deal with it. That is one reason indoor designs have motor sticks MUCH shorter than the loop length of the actual motor. It is problematic because it CAN strongly pull the nose and tail down, causing a plane that glides perfectly well, or even climbs on a partly wound motor, to dive into the ground with a fully wound motor.

Jeff Anderson
Livonia, MI

[pumptato-cat]

Thank you all for the help!! Really appreciate it :)))))
Another question(they just don't stop coming :/) :

I have no idea what glue to use--I don't see any local hobby stores where I live(searched everywhere) and I checked some of the bigger stores--nobody can tell me how old the glue is :( I have a bottle of 8mo old Loctite glue, and it's still watery. Is there any other indicator of glue age?
bjt4888, "We bought three 1/2 ounce bottles for that price. This is enough for construction and repair of the 18 airplanes my teams will build this year. Yes, fresh matters a lot."
Where did you get the bottles?.. Shipping on modelling websites is outrageous(11$ or more) and I'm genuinely confused now, absolutely no idea what to do :(

I've also built my torque meter from FF--the needle isn't pointing at 0 in resting position, though. Any ideas on fixing this? I've tried bending it w/ pliers and some other stuff and I'm afraid of breaking it.

[jander14indoor]

If the CA glue is very watery in the bottle, it should be fine. Especially for thin, and pretty much for medium viscosity. You shouldn't be using thick viscosity anyway. If it is watery thin when you tip the bottle around, don't sweat it.

Torque meter. I'm not too familiar personally with their meter, but looking at the picture, can you rotate the dial to align with the pointer? How is it anchored at the far end of the meter from the dial? Can the anchor be rotated in the tube? Nothing wrong with bending the pointer, you should be able to bend it a fair amount without danger. And of course you could also contact Dave Zigler, the owner. His e-mail is at the bottom of their web page and I have always found him very helpful. As a last resort, you could always write down the error at zero torque and use it as an offset for all other positions.

Comment on torque meters. They really don't have to be that accurate, in that the indicated numerical value is giving the true torque in whatever units the meter is labeled. What is important is consistency. If the needle points at 1.5 in-oz, for example, is it the same actual, but unknown, torque every time. These things are so simple, that you don't really need more than that. If 1.5 indicated gets you to the ceiling every time in a 25 ft gym, or whatever indicated torque and ceiling you need, you don't need more than that. AS LONG AS YOU ONLY USE ONE TORQUE METER! Accuracy, as in indicated torque equals true torque is only important in comparing results from different flyers using different torque meters.

Jeff Anderson
Livonia, MI

[bjt4888]

Thank you all for the help!! Really appreciate it ))))
Another question(they just don't stop coming :/) :

I have no idea what glue to use--I don't see any local hobby stores where I live(searched everywhere) and I checked some of the bigger stores--nobody can tell me how old the glue is I have a bottle of 8mo old Loctite glue, and it's still watery. Is there any other indicator of glue age?
bjt4888, "We bought three 1/2 ounce bottles for that price. This is enough for construction and repair of the 18 airplanes my teams will build this year. Yes, fresh matters a lot."
Where did you get the bottles?.. Shipping on modelling websites is outrageous(11$ or more) and I'm genuinely confused now, absolutely no idea what to do

I've also built my torque meter from FF--the needle isn't pointing at 0 in resting position, though. Any ideas on fixing this? I've tried bending it w/ pliers and some other stuff and I'm afraid of breaking it.

Cat,

My teams have several of these Freedom Flight torque meters, and yes, as Jeff suggests it's no problem to bend the pointer with pliers so that it rests at zero. I ordered Zap medium CA from StevensAero.com but the shipment got hung up (no fault to Stevens Aero; just logistics) so I also ordered from here and got fresh glue. If you have Amazon Prime the shipping is free: https://www.amazon.com/dp/B00L986E2U?ps ... ct_details

Here's a few pictures of one of my teams airplanes partly finished to hopefully get more discussions going:

https://drive.google.com/drive/folders/ ... sp=sharing

The design looks a little like the J&H Aero kit, but we started prototyping shortly after the Summer Institute and before the J&H kit was out. So, just a coincidence that airplanes look similar (there are differences though). I'm not showing the propeller as this, in my belief, is one of the keys to the event this year. Students should research possible propellers in this forum (look at previous years forums; maybe especially 2015; hint, hint) and on the NFFS website and other indoor free flight forums and web pages. And, test, test, test different solutions.

Enjoy,

Brian T