Flight B/C

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Re: Flight B/C

Post by bjt4888 »

Frost0125 wrote: December 5th, 2022, 10:29 am Hi!

I'm new to build events, and ordered a J and H Aerospace kit for flight. Since it is supposed to arrive in the next few days, I looked at the extra items necessary for build, and it mentioned a winder. Is there anyway to get a winder at a brick and mortar store (preferred) , or fairly quickly (within next week)? Or even DIY
I’ve seen people build winders using Lego gears and a little thin plywood and wire from a craft or hobby store.
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Re: Flight B/C

Post by jander14indoor »

There is no need to panic on the winder. It isn't used to build the plane, but to wind the motors when you start flying. If you don't have the kit in hand, you have time to order one on-line. It will take you a couple of sessions to build the plane.

If you don't want to get the winder through J&H where you got your kit, search on KP Aero winders Or Knight & Pridham winders. Many on-line sources. There are other winders available, but in that price range, nothing touches the K&P winders (in my experience anyway).

Note, you want the winder that looks like this: https://lasercutplanes.com/product/kp-aero-151-winder/ in either 10 or 15 to 1 ratio. They make a similar looking one in same ratios for larger outdoor planes. You don't want that, more expensive and heavy, overkill for these planes.

Note on why you want/need a winder if not clear. Fully wound motors for these planes take well over 1000 turns. You can get there winding with your finger, but it will take forever. Winders make winding practical within the 10 minute contest limit.

Jeff Anderson
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Re: Flight B/C

Post by poonda »

Maxout wrote: December 2nd, 2022, 10:28 am
poonda wrote: December 2nd, 2022, 7:01 am tested a high aspect ratio design and i'm not sure how to fix some weird behaviors;

upon launch the plane starts circling left but then straightens itself out by a weird dutch roll process that eventually results in a right turn
after this weird launch, the plane climbs about 5ft and then maintains altitude for roughly a minute
there aren't any issues in the glide and nothing is loose or broken

anybody know how to fix this? i've never seen this before
Post photos if you can. High aspect designs make me nervous and don't seem to be the best solution this year. They tend to be very aeroelastic in any year, but last year we didn't have a choice. This year we do. Fun fact in spite of that: last year's designs do appear to be legal for Div B, or at least some of them.

Verify that you have both left thrust and left rudder trim, and also that your stab isn't tilted so the right side is higher than the left, as that can also cause problems. the stab also must be warp-free, or it will twist the tailboom at high speeds, causing the stab tilt to change, sometimes dramatically.
oop thanks sorry i didnt see this
i dont have pictures right now but the plane dimensions are:
40cm x 6cm for the wing
20cm x 6cm for the stabilizer
plane is like 50cm ish long

i did actually get it working, kind of
the plane now climbs really really slowly and flies somewhat smoothly, only it turns right despite having everything trimmed to turn left
honestly im done man i dont wanna work on this plane anymore lol
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Re: Flight B/C

Post by randomdogonapc »

This is my first post on the SciOly forums, so sorry if there are any mistakes.
I have had a few questions with some different aspects of aircraft design. I would say that I’m pretty far in the aircraft research process. But for some subjects, I can’t find many resources that relate to the indoor free flight, or even model aircraft category. Here are some of my questions:
1. I’m stumped on what the length of the motorstick changes. My initial hypothesis was that the length of the motorstick relied on the length of the motor, but that quickly was found to be wrong. How long should the motorstick be, and what would that change? Any ratios for motorstick to tailboom length?
2. I’ve heard about something called “propeller vibration.” I don’t know what this is or if I should worry about it. Could someone please explain to me what it is.
3. Another question relating to propellers, what is the “optimum operating condition” for a propeller? Is it something that can be tested? Or is it a calculation?
Those were just a few of my questions. Thanks to anyone who will respond! :D
Last edited by randomdogonapc on December 8th, 2022, 3:49 am, edited 1 time in total.
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Re: Flight B/C

Post by BrianZ »

Hey Poonda, where in Missouri are you? I live in Springfield, and if you are in that area I would be happy to take a look at your plane and offer some advice. I've been flying our plane in McDonald Arena at Missouri State, which is where my regionals and state competition will be.
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Re: Flight B/C

Post by jander14indoor »

Motorstick length. It doesn't really affect much. IF you get it too short, you can run into problems towards the end of the flight with the motor either dropping off the stick, or spitting knots out sideways. Too short depends a little on experience, but I'd keep the motor stick at least as long as the unwound, looped motor.
Oh, too long adds unnecessary weight. Too long is any longer than that unwound loop.
There is probably an ideal weight from an energy release point of view, but frankly the difference is so small that it is seldom, if ever considered in designing these indoor planes.

"Propeller vibration", I can make a guess, but can you give us some context or an example? I'm guessing it is the result of an unbalanced propeller, either mass or aerodynamic. Tends to waste energy, and if it gets bad enough can cause control problems.

"Optimum Operating Condition" RPM, airspeed, atmosphere conditions (temp/pressure) where the propellor is providing maximum thrust with minimum drag/input. With sufficient computing power and lots of graduate level equations, it can be calculated, sort of. It will depend a lot on the assumptions you make around it. In a sense you are trying to figure out the factors that give you this condition (or close to it) over the flight of your aircraft. But you won't get there with equations. Instead, you will be testing combinations of rubber, prop design factors (typically diameter, pitch and blade shape, perhaps number of blades) that give you the longest flight.
Oh, and the nature of rubber power and planes is such that you want a propellor that operates well over a range of conditions (high rpm early in flight, low towards end), not just a single 'optimum' condition.

Read back up this chain for hints/tips and ideas about how you go about finding that best plane, propeller and rubber combination.

Jeff Anderson
Livonia, MI
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Re: Flight B/C

Post by randomdogonapc »

Thanks a lot. I’ve done a bit of research on prop vibration and I’ve determined that it is because of an unbalanced propeller. Is there anything important for tailboom length? Also, I’ve received advice to experiment with tandem wings and biplanes instead of lower the aspect ratio to grant more wing area. Should I try this out?
Last edited by randomdogonapc on December 9th, 2022, 2:45 pm, edited 1 time in total.
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Re: Flight B/C

Post by pumptato-cat »

I'm not the most qualified to answer your question, but if you're new to this event, you should probably not be experimenting with biplanes and tandem wings(yet ;)). From what I've seen, biplanes are rather hard to build, and it's better to get flying with something simple. You'll probably gain more experience that way, and the monoplanes I've seen so far fly well.
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Re: Flight B/C

Post by randomdogonapc »

Ok, thanks for the feedback!
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Re: Flight B/C

Post by bjt4888 »

randomdogonapc wrote: December 9th, 2022, 4:12 am Thanks a lot. I’ve done a bit of research on prop vibration and I’ve determined that it is because of an unbalanced propeller. Is there anything important for tailboom length? Also, I’ve received advice to experiment with tandem wings and biplanes instead of lower the aspect ratio to grant more wing area. Should I try this out?

I agree with Cat. If you’re new to the event, buy one of the good kits and learn to fly it well. If you can get 2:45 to three minute flights in a 25-30 ft gym, then you’re ready to experiment with different propellers on your kit.

Brian T
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