Wright Stuff C

jander14indoor
Member
Member
Posts: 1559
Joined: April 30th, 2007, 7:54 am

Re: Wright Stuff C

Postby jander14indoor » November 4th, 2019, 12:34 pm

What are the best or necessary materials?
Structural parts of plane, balsa, carefully selected, is all you NEED to build a VERY good airplane. The trick is in 'carefully selected'.
Selective use of small amounts of carbon fiber can reduce how carefully you need to select your balsa. It can make the plane a little tougher, particularly carbon fiber wing spars. But frankly, this is NOT the part of the plane I generally break.
It can be useful in stiffening the motor stick, but there are other ways to get there with balsa (hollow motor sticks).
Wire is about the only choice for your propeller shaft and motor hook. But you don't need massive diameter. I typically use 0.020 to 0.025 diameter music wire.
Propellers, balsa allows light blades, is fragile. Sheet plastic will work for these planes for the blades, read back up this string to see discussion thereon.
Covering. I have used dry cleaner bags, produce bags, grocery bags. The trick is to get a collection of these from local stores, weigh and select the material that is lightest per square cm, inch, foot, whatever. You do NOT need specialized indoor mylar films for these planes. It's not hard to find a material that costs less than 0.5 gm of your 8.0 gm budget for this years rules. I used dry cleaner bags this year and it still allowed me to use what I consider incredibly dense/strong balsa (7-10 lb/ft3) for my structural parts. And my plane came in at 7.5 gm before ballast.

I've updated my Bill of Materials for this years plane if someone can show me how to load the excel file or a snapshot to the site.

Jeff Anderson
Livonia, MI

paschw30
Member
Member
Posts: 2
Joined: October 24th, 2019, 6:57 pm
Division: C

Re: Wright Stuff C

Postby paschw30 » November 6th, 2019, 7:44 am

I have a few questions regarding propellers:
Is it worth getting the Ray Harlan pigtail bearings for SO or are the Ikara prop assemblies that come with the FF kit okay?
I am looking at making my own prop, what do you use for the hub and spar? How do you attach the blade to the spars?

Thanks,
Patrick

bjt4888
Member
Member
Posts: 551
Joined: June 16th, 2013, 12:35 pm
Division: C
State: MI

Re: Wright Stuff C

Postby bjt4888 » November 6th, 2019, 3:27 pm

Patrick,

Congrats on planning your own propellers. Ikara prop hangars and nose bearings are workable and successful airplanes use them. That being said, my teams use the Harlan bearing. This bearing has built in 1/4” stick clearance for the motor and is Probably a lower shaft friction coupling. We use tiny Teflon thrust bearings (2 of them) sliced from tubing. Prop spars can be made from 1/16” basswood stick or basswood and carbon rod in combination. Blades can be balsa (probably 10 - 12 lb cu ft) or cut from plastic bottles or cups or cut from the blades of larger Ikara props. Glue blades with CA using a jig to hold them at the desired pitch angle.

Good luck,

Brian T

paschw30
Member
Member
Posts: 2
Joined: October 24th, 2019, 6:57 pm
Division: C

Re: Wright Stuff C

Postby paschw30 » November 7th, 2019, 8:58 am

Thanks a lot! I have a few more questions:
Where is the best/cheapest place to get teflon tubing and .20" piano wire? What size of teflon tubing? If possible could you send the links to these websites? How much will I need of each in order to have enough for multiple props for testing and experimentation? Why do you need two bearings? Could you maybe send a picture of this setup(or a similar one) so I can have a better idea of what I'm doing?
On the bucket prop spreadsheet, there is pitch and angle (such as tip angle) both listed, what is the difference? How do you measure each?
What would you recommend, making the prop out of balsa or the plastic of the container(like a yogurt container)? Either way I am planning to sand/shape similarly to the double trouble model from Chris Goins in order to get a little bit of a flare, but I am definitely going to experiment with different things.
On another note, I noticed that some people are using 3 bladed props, what is better 2 or 3 blades?

Thank you so much for your help!
Patrick

bjt4888
Member
Member
Posts: 551
Joined: June 16th, 2013, 12:35 pm
Division: C
State: MI

Re: Wright Stuff C

Postby bjt4888 » November 7th, 2019, 10:32 am

Patrick,

https://www.hach.com/ptfe-tubing-020-in ... allback=qs

This tubing is sold by the foot and is a little small in inside diameter (exactly .020”). You can ream out the inside with a .022” or .024” drill bit and then slice 1/32” thick or less little o-ring/washer “bearings. Two thin Teflon washers because one will rub against the other and give a nice low friction setup. There is a picture of our propeller (for 2015), Harlan Bearing and Teflon bearing in the 2015 Wright Stuff archive under the “Design” thread.

.020” wire is available from a number of model airplane hobby websites and hardware websites. Use K&S Precision Metals wire (google it exactly) to get good quality wire. Order from a known entity, not a generic “supplier” to be sure you get the real stuff.

Good luck and have fun,

Brian T

jander14indoor
Member
Member
Posts: 1559
Joined: April 30th, 2007, 7:54 am

Re: Wright Stuff C

Postby jander14indoor » November 7th, 2019, 1:52 pm

Thanks a lot! I have a few more questions:
<SNIP>
On the bucket prop spreadsheet, there is pitch and angle (such as tip angle) both listed, what is the difference? How do you measure each?
What would you recommend, making the prop out of balsa or the plastic of the container(like a yogurt container)? Either way I am planning to sand/shape similarly to the double trouble model from Chris Goins in order to get a little bit of a flare, but I am definitely going to experiment with different things.
On another note, I noticed that some people are using 3 bladed props, what is better 2 or 3 blades?

Thank you so much for your help!
Patrick
Pitch is the theoretical distance the propeller will move forward in a single rotation, treating it a screw going through a 'solid' medium. Pitch/Diameter is a common way to describe a prop because its importance stays RELATIVELY the same over a wide range of prop sizes. It also allows you to lay out the helical shape of the prop.

Angle, as in tip angle, is the angle of the tip of the blade relative to the plane the blade spins in. It is used to set the blade angle when you attach it to the hub to give the propeller blade a specific pitch over its whole length. Assuming the has a helical twist, which is what the bucket props spreadsheet is trying to approximate.

3 or more vs 2 blades. The idea is with these small diameter props to get more power out of them. Each blade adds to the thrust at a given rpm. Not in a linear fashion as each blade interferes with the other, to a degree. Example, directional only. For same speed, 1 blade gives one unit of thrust, 2 blades gives 1.95 units of thrust, 3 blades gives 2.85 units of thrust, 4 blades gives 3.75 units of thrust, and so on. Each added blade means all the blades are slightly less effective. Why do you care? Well, with these small diameter props, two blades dictates thin motors, and are marginal for providing sufficient thrust. Three has more thrust, can turn slower, needs fatter rubber, probably less sensitive to small variations in rubber thickness. MAY provide better use of rubber energy, longer flights. Answer to be determined by the students from their experimental data (in other words, I don't know, need DATA to tell). What we do know from past experience (data), is large diameter (%50+/- of wingspan), slow turning props are better for long flights. The goal of fat bladed, multi bladed props is to emulate these large diameter props.

Hope that helps a little.

Jeff Anderson
Livonia, MI

lechassin
Member
Member
Posts: 62
Joined: September 11th, 2019, 9:49 am

Re: Wright Stuff C

Postby lechassin » November 7th, 2019, 3:55 pm

I settled on three blades for the reasons listed, but I'm anxious to hear what others will achieve with two blades. It looks like I'll need to wait for competition results ;) .

As of now, I don't see how a two-bladed prop is going to run longer than 90 seconds this year unless the rubber is so thin that it won't have enough umph to pull 10-11 grams around, especially if it's a monoplane with twice the wing loading and the inevitably higher decalage that results (drag)

We'll have to wait and see!

lechassin
Member
Member
Posts: 62
Joined: September 11th, 2019, 9:49 am

Re: Wright Stuff C

Postby lechassin » November 10th, 2019, 1:38 pm

We spent today learning a new space with HVAC in it, and had our best flight time yet, 1'50" to the right:
https://www.youtube.com/watch?v=yju4a7r ... e=youtu.be
I didn't crouch down because we were just trying to figure out the best launch location to avoid touches and air handlers.

1'45" to the left:
https://www.youtube.com/watch?v=rt8HQGQ ... e=youtu.be
We should have launched with a bit more torque, but mid flight it recovers well from an HVAC draft.

The big relief was confirming that the planes can recover from flying under an air handler, which they can, but they do lose altitude. As for our increasing times (a few seconds each week), it really is rubber and props at this point.

Luke is basically rehearsing techniques in anticipation of the first meet in three weeks. His best flight today was only 1'20" because he winds conservatively, not stressing the motors and not courting the rafters. Hopefully as he gets more experience his times will inch up. Frankly the biggest obstacle for him is not relying on me to troubleshoot, but that problem is solving itself because I need to get working on elastic launch glider for the younger boy, a whole other challenge.

Edit: we got a PM wanting a video explaining the 30:1 winder:
https://www.youtube.com/watch?v=DxaID_o ... e=youtu.be
I'm sure our way isn't the best, but it hasn't given us any trouble at all (jinx...) and speed is adequate. We haven't tried modifying our 20:1 winder but if someone else does, it'd be great to see how that works out.

User avatar
xiangyu
Member
Member
Posts: 82
Joined: April 6th, 2019, 8:32 pm
Division: C
State: MI
Location: East Grand Rapids, Michigan

Re: Wright Stuff C

Postby xiangyu » November 10th, 2019, 5:10 pm

We spent today learning a new space with HVAC in it, and had our best flight time yet, 1'50" to the right:
https://www.youtube.com/watch?v=yju4a7r ... e=youtu.be
I didn't crouch down because we were just trying to figure out the best launch location to avoid touches and air handlers.

1'45" to the left:
https://www.youtube.com/watch?v=rt8HQGQ ... e=youtu.be
We should have launched with a bit more torque, but mid flight it recovers well from an HVAC draft.

The big relief was confirming that the planes can recover from flying under an air handler, which they can, but they do lose altitude. As for our increasing times (a few seconds each week), it really is rubber and props at this point.

Luke is basically rehearsing techniques in anticipation of the first meet in three weeks. His best flight today was only 1'20" because he winds conservatively, not stressing the motors and not courting the rafters. Hopefully as he gets more experience his times will inch up. Frankly the biggest obstacle for him is not relying on me to troubleshoot, but that problem is solving itself because I need to get working on elastic launch glider for the younger boy, a whole other challenge.

Edit: we got a PM wanting a video explaining the 30:1 winder:
https://www.youtube.com/watch?v=DxaID_o ... e=youtu.be
I'm sure our way isn't the best, but it hasn't given us any trouble at all (jinx...) and speed is adequate. We haven't tried modifying our 20:1 winder but if someone else does, it'd be great to see how that works out.
Wow, that awesome! It's great to see your progress as you get closer and closer to 2 min.

Updates on our progress over the past couple of weeks. We continued to test our mono wing plane but didn't have too much success. We were able to tweak it and consistanly maintain our 1:20, but just can't increase much further. Thus, I decided to build a bi plane and see if it would work better.Today was our first test of the bi plane and honestly it didn't go too well. There seem to be some problem with the plane in that it doesn't climb at all. The thing is, if I increase wing angle even by a little bit, the plane would start to climb then stall out. Increasing torque results in the same result. We played around with CG and wing placement and nothing seems to work. I built from the freedom flight kit and I'm pretty sure I followed all the steps correctly. Does anyone have any suggestions on what I should change/try next weekend to get my bi plane in the air?

Xiangyu
2020 Events

Wright Stuff, Gravity Vehicle. Machines, Circuit Lab, Boomilever, Ping-Pong Parachute

Medal Count: 2
East Grand Rapids High School, Michigan

bjt4888
Member
Member
Posts: 551
Joined: June 16th, 2013, 12:35 pm
Division: C
State: MI

Re: Wright Stuff C

Postby bjt4888 » November 10th, 2019, 5:59 pm

Xiangyu,

Congrats on building the biplane. Did you have the following all exactly per plan: CG, wing incidence and wing washin? Did you install the carbon diagonal struts connecting the wing LE and TE to the wing posts exactly per the plan? If not, what does each of these specs measure and what is your diagonal strut arrangement? What is your circle size? When you changed the CG during testing, how much did you move it between each test flight (this is the key question).

Brian T


Return to “Wright Stuff C”

Who is online

Users browsing this forum: No registered users and 0 guests