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May 27, 2019, 02:57 AM
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Exxon - A 3m SynerJ based sailplane


Hey all,
My name is Joseph, and I am currently studying year 12 Systems Engineering in Australia. (year before graduation)
As I am doing this subject, I have to create a project which includes both mechanical and electronic aspects. It is very open ended. I also have to complete a folio, the link to which I will be sharing on here for people to read over.

For my project, I decided to make a sailplane which is based off the SynerJ wing which is in one of the forums online here.
I am currently 16 years old, and have been flying R/C planes with my Dad for the last 4 or so years.
I learnt on a Radian-based plane which had a homemade fuselage. (called Scrappy. I'm sure you can find the build log on here somewhere)
This project is one that I was unfamiliar with, as I have never really made a plane from scratch. So if you're explaining something to me, please be patient if I do not understand some of the complexities of the hobby. (such as reynolds number. Can someone please explain what they are??)

As stated above, Exxon (my plane) will be made with a SynerJ wing, which will be 3m long. The wing cores will be CNC cut out of blue foam, then covered with fiberglass and a carbon strip down the middle, much like the Geronimo glider. They will be vacuum sealed using a food sealer and a homemade vacuum pump. Each wing has ailerons as well as a flap in the centre section. Against the advice of a lot of people on this forum, Exxon will have a flat centre section. This is mainly because I have limited skills in creating these kind of planes. It is also because it will make the mounting system on my fuselage a hell of a lot easier, which will save me a lot of time.
The fuselage is moulded fiberglass (unless i figure out how to use carbon fiber) with a carbon fiber boom that is currently 1m long. (this will be cut down to size) I am currently in the process of making the mould for the fuselage, and expect to have it finished pretty soon.

I am using the Graupner MZ-24 Telemetry system with a GR-16L receiver. The motor I will be using is a Sunnysky X2220-iii 980kv, which can be seen here: http://www.rcsunnysky.com/index.php?...tml&lang=en-us .

With the 12 x 8 Aeronaut propellor I am using, this produces 1971g of thrust with a thrust-weight of 2.32. (using propcalc) It uses 363.8W at max throttle, drawing 36.9A and using 9.9V. Unfortunately, this means that I have to use a 40A ESC, which will just add more weight to my plane. I am using a Hyperion 3S 1200mAh battery as well as metal geared hyperion servos. (DS-11 and DS-09 servos)

I wanted to start this thread to share pictures of my progress, as well as getting advice from the community about the creation of my plane.
I am creating a folio as part of my project, which has to be submitted on the 14th June.

https://docs.google.com/document/d/1...it?usp=sharing

Above is the URL to access my folio. It is view only. Comments are welcome in this thread.

Also note: my folio is a work in progress.

I look forward to hearing people's opinions on my project. Hopefully I will be able to keep this thread updated week-to-week.

Cheers

Edit: sorry for previous colorful aussie language.
Last edited by jroshier; May 27, 2019 at 06:38 AM.
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May 27, 2019, 03:00 AM
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Photos:


Photos:
Last edited by jroshier; May 27, 2019 at 03:12 AM.
May 27, 2019, 03:29 AM
Everything's A Compromise
Larrikin's Avatar
G'day Joseph, I'm David.

So, to get a better understanding of your project target, what do you intend to do with the completed project?
Is it for later use in competition or is this just something to get a grade and never fly again?

This will offer some intel has to how many corners we ... ahem ... I mean, you ... can cut.

June 16 is a really tight deadline because there's a lot time spent waiting for epoxy to cure.

D.
May 27, 2019, 06:08 AM
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Quote:
Originally Posted by Larrikin
G'day Joseph, I'm David.

So, to get a better understanding of your project target, what do you intend to do with the completed project?
Is it for later use in competition or is this just something to get a grade and never fly again?

This will offer some intel has to how many corners we ... ahem ... I mean, you ... can cut.

June 16 is a really tight deadline because there's a lot time spent waiting for epoxy to cure.

D.
Hey David,
Thanks for your reply.
Yes this is for later use in competition. I want a good grade, but i'm really into flying, so it isn't intended to be made to only look pretty.

I entered in the NEFR at Coota earlier this year, but was restricted to flying my altered Radian in the F5J, so I wanted something bigger. I did come 2nd in the Radian comp, and got two 3rds in old timer comps, but I really prefer F5J.

The June 14 deadline is for my folio only, not the actual project.
The final submission date for the plane is Aug 30th, then I need to do testing. I need to submit before I test because I don't want to try and test my plane, crash it, and then have to submit a crashed plane.
I have given myself until the 9th June to finish the fuselage, which is going to be hard because my mid-year exams are next week.
I have also given myself a deadline for Aug 3rd to finish the wings and tail plane. This gives me three weeks to connect, program and submit the plane before the deadline. Then onto the testing phase!!

Thanks again for your reply! (and for your offer of help )

Cheers,
J

P.S. I actually get marks for not sticking to my timeline (don't ask why) so the deadline's aren't really strict
May 31, 2019, 11:41 PM
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Update:


Just an update:
My teacher has given the due date for my folio to be the 4th June, instead of the 14th.
I am currently rushing through it to try and finish it right now because I have exams next week.

If some of you could read through it and give me some comments on this thread, that would be really appreciated.

Thanks,
J
Jun 04, 2019, 12:53 AM
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Folio Update:


My folio is now completed.
On to the building stage!!!!! xD
Jun 04, 2019, 02:27 AM
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More photos:


Some pictures of my (very) basic design for the rudder and elevator, as well as pictures of post curing the resin on the mould.
Jun 04, 2019, 08:16 AM
Sagitta Fanboy
I'd suggest going to a tail set with a more consistent chord, those rounded designs will lose effectiveness as compared to a constant-chord design because the efficiency drops off fast (as the reynolds number drops).

I'd also think you have way too little control surface, especially on the elevator, but even the rudder is small. Take a look at the Bubble Dancer design for a well sorted set of control surfaces for an aircraft of similar size.


PS, this is an awesome project. Very much looking forward to seeing the final project.
Jun 04, 2019, 05:06 PM
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Quote:
Originally Posted by mawz
I'd suggest going to a tail set with a more consistent chord, those rounded designs will lose effectiveness as compared to a constant-chord design because the efficiency drops off fast (as the reynolds number drops).

I'd also think you have way too little control surface, especially on the elevator, but even the rudder is small. Take a look at the Bubble Dancer design for a well sorted set of control surfaces for an aircraft of similar size.


PS, this is an awesome project. Very much looking forward to seeing the final project.
Thank you so much for your reply and feedback.
I really made those designs just to stick in my folio, as I was running out of time. They're very basic.
I've seen videos of a bubble dancer, and will probably go with your suggestions to make a tailplane similar to it.
I've tried to get a simple answer from people at myc club, but no one really explains it well. What is a reynolds number? Why is it important? What use does it have? Is it a never ending number like pi, or is it like e?

Thanks again for your reply,

J
Jun 04, 2019, 07:42 PM
Sagitta Fanboy
Quote:
Originally Posted by jroshier
Thank you so much for your reply and feedback.
I really made those designs just to stick in my folio, as I was running out of time. They're very basic.
I've seen videos of a bubble dancer, and will probably go with your suggestions to make a tailplane similar to it.
I've tried to get a simple answer from people at myc club, but no one really explains it well. What is a reynolds number? Why is it important? What use does it have? Is it a never ending number like pi, or is it like e?

Thanks again for your reply,

J
https://en.wikipedia.org/wiki/Reynolds_number

We use it largely as an assist in predicting wing efficiency, as well as in combination with a polar graph for an airfoil to predict performance.
Jun 04, 2019, 08:30 PM
Brett
bjaffee's Avatar
I don't see why the flat center section would be an issue, especially if you have some tip dihedral and ailerons anyway. I'd agree that the elevator and rudder look really small (the elevator especially).
Jun 04, 2019, 11:43 PM
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Quote:
Originally Posted by mawz
https://en.wikipedia.org/wiki/Reynolds_number

We use it largely as an assist in predicting wing efficiency, as well as in combination with a polar graph for an airfoil to predict performance.
Okay. But why does it matter? What does it measure? Is a higher or lower number bettor or worse?

Thanks for the feedback and help.

J
Jun 05, 2019, 12:04 AM
Brett
bjaffee's Avatar
I believe what Re would tell you would be what airfoil would be best for a given wing chord. I think higher numbers are more efficient, as the airflow transitions from smooth to turbulent later then it would with smaller numbers. But, the only way to really vary the Re in your case is by changing the chord of the wing. Since you've pretty much already defined the size (roughly at least), that might mean picking an airfoil that's best for that Reynolds number/chord.

OTOH, since your glider seems comparable in size to many existing sailplanes, you might just want to investigate the different airfoils already in use, and pick one of those.
Jun 05, 2019, 12:14 AM
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Quote:
Originally Posted by bjaffee
I believe what Re would tell you would be what airfoil would be best for a given wing chord. I think higher numbers are more efficient, as the airflow transitions from smooth to turbulent later then it would with smaller numbers. But, the only way to really vary the Re in your case is by changing the chord of the wing. Since you've pretty much already defined the size (roughly at least), that might mean picking an airfoil that's best for that Reynolds number/chord.

OTOH, since your glider seems comparable in size to many existing sailplanes, you might just want to investigate the different airfoils already in use, and pick one of those.
Thanks for your reply.
I have already chosen the SynerJ airfoil. My dad made up the design for my wing on the DevWingFoam program, so it could be CNC cut out of a hot wire cutter. I'll try to do more research on Re. If I have a thinner airfoil, would it increase or decrease the Re? Will it make a huge difference if surfaces on my plane aren't fully sanded, so they're fairly rough? By huge difference, i really mean noticable when i'm thermalling about 80ish m off the ground.

Thanks again for your reply.

J
Jun 05, 2019, 12:17 AM
Brett
bjaffee's Avatar
I don't think thickness has an effect on Re...

Quote:
Fluid dynamicists define the chord Reynolds number R like this: R =
Vc/ν, where V is the flight speed, c is the chord length, and ν is the kinematic viscosity of the fluid in which the airfoil operates
So, you can control the chord length, and presumably you know what speed this thing will probably at. But that's all you can really change.


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