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Old 02-09-2013, 09:51 PM   #201
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Got it all finished for the first Miata Challenge event of the 2013 season which is tomorrow -


The finished uprights are drilled in a way that allows adjusting AOA (duhh..), height and tilt back on the uprights themselves (leverage) -

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Old 02-09-2013, 10:54 PM   #202
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Wow... Looks great. Great freaking car. I like the mount brackets.
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Old 02-09-2013, 11:27 PM   #203
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Moti - I like the mounts, especially for the experimentation they'll let you do. Did you do anything about front aero? There's nothing obvious in the pics, do you have something sneaky going on? Especially with the wing so far back, it seems that could be a problem.
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Old 02-09-2013, 11:53 PM   #204
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Thanks.
Haven't had time to work on the splitter, I'll have it on for the next event, maybe some sneaky stuff too ...
For the time being, I set the wing @ 0 AOA.
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Old 02-10-2013, 12:46 AM   #205
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Quote:
Originally Posted by Mobius View Post
Rockin.

Edit: are you going to run the mounts into the bumper supports through the bumper cover ala 949's Crusher, or ... what?
Yes I am as I feel that is the best overal way.
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Old 02-10-2013, 03:52 PM   #206
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Car looks great moti. Do you have a gallery anywhere with more pictures? Especially the cage/windshield chop stuff.
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Old 02-10-2013, 05:29 PM   #207
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Default An Alternative for the DYI

Pick an airfoil from:
Theory of Wing Sections: Including a Summary of Airfoil Data - Ira H. A. Abbott, Albert Edward Von Doenhoff - Google Books
Make a plot using a CAD program and print on paper.
Cut the paper and glue on aluminum (.032 is just fine) and then cut aluminum to size. Do this twice.

Decide if you want male buck or female mold (if I have to explain, you fail at Google 101).

For Male buck, buy some blue foam insulation.

Cut foam to desired width.

Epoxy the aluminum templates to the ends, maintaining alignment.

Make a hot wire cutter and cut foam to match the aluminum endplates + some 6" of overlap at each end.

Buy some carbon bi-directional CF mat from:
ACP Composites -Carbon Fiber Woven Fabrics

Lay up the carbon cloth to overlap at the trailing edge (if you do not know what that is, read up on it).

Vacuum bag it using the epoxy of choice and autoclave it if you have friends with access to one.

Voila! Wing for a few hundred bucks.

You can remove the foam core if you want lighter weight or room for electronics (to measure down-force and such, or to actuate a Gurney type flap using servos). You can even make a main spar before you do your lay-up and insert it into the foam core and rivet it to the end plates for additional strength.

I did this type of work when designing and building a winning aircraft for the Aerodesign competition while in college and George Sparr of ACP is an alumnus of my school and he helped quite a bit. ACP (Aerospace Composites at that time) and Pan Am were the main sponsors.

Regardless if you use this method or not, best L/D (lift over drag) at the critical velocity is what you are after (or maybe L/D over mean Velocity during a race but that gives you less than optimal when you want max.G) unless you optimize for critical corners where you can beat your opponents in lateral G's.

For Miata race cars, glider wing sections seem to work best.

For Formula 1 cars, they need to get into performance aircraft aerodynamics.

Either way, the complete vehicle aerodynamics need to be worked out as a whole and the first person to do this will win big. Do you have a college with an aeronautical engineering program and a decent low speed wind-tunnel in your area? Maybe you can bribe a teacher or some students into taking the Miata Aero as a project.

The Reynolds number scaling is not too bad for these little cars. Not like testing a wing for a 777 in a wind-tunnel with a 10x10" cross-section.

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Old 02-10-2013, 07:27 PM   #208
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Quote:
Originally Posted by danny2747 View Post
Pick an airfoil from:
Theory of Wing Sections: Including a Summary of Airfoil Data - Ira H. A. Abbott, Albert Edward Von Doenhoff - Google Books
Make a plot using a CAD program and print on paper.
Cut the paper and glue on aluminum (.032 is just fine) and then cut aluminum to size. Do this twice.

Decide if you want male buck or female mold (if I have to explain, you fail at Google 101).

For Male buck, buy some blue foam insulation.

Cut foam to desired width.

Epoxy the aluminum templates to the ends, maintaining alignment.

Make a hot wire cutter and cut foam to match the aluminum endplates + some 6" of overlap at each end.

Buy some carbon bi-directional CF mat from:
ACP Composites -Carbon Fiber Woven Fabrics

Lay up the carbon cloth to overlap at the trailing edge (if you do not know what that is, read up on it).

Vacuum bag it using the epoxy of choice and autoclave it if you have friends with access to one.

Voila! Wing for a few hundred bucks.

You can remove the foam core if you want lighter weight or room for electronics (to measure down-force and such, or to actuate a Gurney type flap using servos). You can even make a main spar before you do your lay-up and insert it into the foam core and rivet it to the end plates for additional strength.

I did this type of work when designing and building a winning aircraft for the Aerodesign competition while in college and George Sparr of ACP is an alumnus of my school and he helped quite a bit. ACP (Aerospace Composites at that time) and Pan Am were the main sponsors.

Regardless if you use this method or not, best L/D (lift over drag) at the critical velocity is what you are after (or maybe L/D over mean Velocity during a race but that gives you less than optimal when you want max.G) unless you optimize for critical corners where you can beat your opponents in lateral G's.

For Miata race cars, glider wing sections seem to work best.

For Formula 1 cars, they need to get into performance aircraft aerodynamics.

Either way, the complete vehicle aerodynamics need to be worked out as a whole and the first person to do this will win big. Do you have a college with an aeronautical engineering program and a decent low speed wind-tunnel in your area? Maybe you can bribe a teacher or some students into taking the Miata Aero as a project.

The Reynolds number scaling is not too bad for these little cars. Not like testing a wing for a 777 in a wind-tunnel with a 10x10" cross-section.

OK now I want to see it done...just kidding
I wish the sanctioning bodies would allow us to run a drs type systems

Hey Moti do you know the down force yours wing creates
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Old 02-11-2013, 01:59 AM   #209
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Quote:
Originally Posted by 1993ka24det View Post
OK now I want to see it done...just kidding
It has been done. Just not by someone with a miata. I would link to to an example, but the time attack forums seem to be down right now.

It's easier said than done though - most home-built airfoils are crude, even with the best efforts, care, and time spent. Expect a decent airfoil on probably your third go at it.

Fabricating your own wing is a really cool, labor intensive, project. But, seeing as how this is a thread about the COT wing, it's noteworthy that the materials alone to build one wing will easily total the same cost as many of us have gotten COT airfoils for. I'd rather save the 60 hours or so to make one.

** Just got back from Streets of Willow with my shakedown of the COT wing. Will take some time to write down my impressions once I've had some rest. Long story short:
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Old 02-11-2013, 09:49 AM   #210
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Quote:
Originally Posted by ThePass View Post
Fabricating your own wing is a really cool, labor intensive, project.
Yeah. I keep thinking I'm done, finding some pin holes or places the gel coat didn't set and having to sand, patch, re-spray. I've used twice as much gel coat as I should have needed, thankfully its not adding to the weight since most of it gets sanded off.
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Old 02-11-2013, 10:21 AM   #211
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Quote:
Originally Posted by Blackbird View Post
...The finished uprights are drilled in a way that allows adjusting... height and tilt back on the uprights themselves (leverage)...
Planning my mounts - I'm trying to find the NASA TT/PT rule regarding how far rearward the wing can be and I can't find it on nasaforums and don't see anything about it in the up-classing rules.

Is it open? Figured someone here would know??
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Old 02-11-2013, 11:14 AM   #212
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About DIY wings: I actually was looking in this direction before starting to play with the COT wing. I've got an HPM wing here (as used in World Challenge circa 2002 or so) and it's made like a home-built airplane wing: machined aluminum ribs, a central spar and a riveted skin. The ribs are the tough part, I was trying to figure how to make them from laser-cut aluminum sheet, but got sidetracked...
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Old 02-11-2013, 09:00 PM   #213
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I would not make a wing to mount on my car that did not have at least a couple of spars running the width and that the mounts tied into.

Foam core wings are great and easy but they have no inherent strength; this has to be added. Since all of the forces generated by the wing will be acting on the mounting points, reinforcing those and making sure that load is distributed throughout the wing is critical. I was considering a traditional built up wing for those reasons. CoT wing and FM's mounts made this moot.

Edit: Keith, there are companies that will laser-cut wooden parts for R/C aircraft. This wing is fundamentally no different from such wings and the forces & speeds it is involved with are typical of high-speed R/C aircraft. Especially considering that the transient ramp-up rate for the forces is so much lower on a car than on the aircraft (no 10-g pullouts). There is no reason you need aluminum ribs. If wood is felt to be insufficiently strong, put a layer of CF on the ribs. Laminate sandwiches are extremely strong.

Aluminum is a lot harder to burn, though.
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Old 02-11-2013, 09:28 PM   #214
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Quote:
Originally Posted by Mobius View Post
I would not make a wing to mount on my car that did not have at least a couple of spars running the width and that the mounts tied into.

Foam core wings are great and easy but they have no inherent strength; this has to be added. Since all of the forces generated by the wing will be acting on the mounting points, reinforcing those and making sure that load is distributed throughout the wing is critical. I was considering a traditional built up wing for those reasons. CoT wing and FM's mounts made this moot.

Edit: Keith, there are companies that will laser-cut wooden parts for R/C aircraft. This wing is fundamentally no different from such wings and the forces & speeds it is involved with are typical of high-speed R/C aircraft. Especially considering that the transient ramp-up rate for the forces is so much lower on a car than on the aircraft (no 10-g pullouts). There is no reason you need aluminum ribs. If wood is felt to be insufficiently strong, put a layer of CF on the ribs. Laminate sandwiches are extremely strong.

Aluminum is a lot harder to burn, though.
Not that your comment applies to it but, just for reference, the APR GT-250 foil has a carbon core. This is the very foil that ended up on Crusher. Bored Asian not included.

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Old 02-11-2013, 09:28 PM   #215
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My wing is foam core with spars. I realize the foam is going to be compressed and will eventually fail. At that point I should be in a position to make iteration 2 of the wing with hopefully improved aero and more lightness.
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Old 02-12-2013, 01:28 PM   #216
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Shakedown at Streets of Willow went successfully. Started at a low angle of attack in fear of the front washing out if I cranked the rear up too much, but I went out and felt like the car had good balance, just tons more rear grip than previously.

The difference is jaw dropping for me. Because I run on street tires (RS-3), I'm especially working hard to maintain rear traction on corner exits. At the last event at Auto Club Speedway for example, in many corners I had to wait nearly until the car was pointed completely straight to get back on full power. With the wing, I was foot-down all the way through 3rd gear corners, all the while thinking inside my helmet "this is fantastic!!!"

When I switched to high boost in the second half of the day, I started cranking the angle of attack up on the wing, and it did a great job of providing all the rear grip I needed and I didn't feel like I was drastically sacrificing front grip. I do have front aero though, I think without front aero you wouldn't want to run this at any angle at all. Even at 0* it was definitely working.

I can definitely back up Keith's findings of time shaved on a small circuit. Although I hadn't ever driven this direction of rotation for this track before, I have run a lot with the same competitors and where I am usually on-par or slightly faster than a couple of those other guys, this event ended with me being 3.5 seconds ahead of 2nd place.



Here's Moti with his COT airfoil:

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Old 02-12-2013, 02:11 PM   #217
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Aero is fun!
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Old 02-12-2013, 03:29 PM   #218
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Did a lot of playing with the wing @ SOW.

I was expecting it to understeer from jacking forces but it really didn't, mind you, I wanted to have the ability to tell the difference from mounting positions alone so I kept the wing @ 0 AOA all day and didn't touch shock settings even though I know I could tune the suspension better...

First session out it was about 2/3rds of the way up, felt stable but the track was very cold so it was hard to gauge.
Tried lowering it to the lowest setting for the second session, now the car was all over the place but I did set my FTD, a new PB @ 1:26.9 .
This left me a bit confused, so for the next session I took the wing off the car and ran it without.
The difference was evident very quickly, as in some of the transitions you could hear the wheel spin... the car was also much more lively to drive, a lot of fun but a bit slower, so yeah, no front aero and a rear wing was still faster.
Wing went back on the car for session #4 and this time I went straight to the highest position that you can see in the pic that Ryan posted.
Stability was back on the menu and the wheel spin was gone, though at that high position you can see the wing moving side to side quite a bit.. couldn't get a clean lap the whole session so no improvement on lap times
Dropped it back to the 2/3rds up position for session #5 and once again got nothing but laps with traffic so no improvement there either..

So, in conclusion, there's lap time to shaved with the wing even w/o front aero as long as you don't get greedy with AOA.
SOW is not a great track to test it in a car that relies on momentum alone.
In Ryan's car the ability to just power by slower cars makes it easier to see the difference in lap time, in my car any driver that wasn't watching his mirrors enough can kill the momentum with one suspicious move.


"Back at COT wing headquarters.."


Wing at 2/3rds of the way up


Wing at bottom position


Wing at top position


Moti
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Old 02-14-2013, 09:04 PM   #219
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Wing arrived today. It was packed with the Left Turn Only endplates attached, and the Hey I Like to Go Straight and Turn Right Also endplates packed separately.

Question about the tethers - what have others done with them? Are they removable if I take the mounting plate off of the wing itself?

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Old 02-14-2013, 10:20 PM   #220
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The tethers are easy enough to remove - pull off the end plates and remove the anchors for the tethers. Then just pull the tethers out. Interestingly, they cross inside the wing so the left tether is attached to the right end of the wing.
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