What's a better name for a "wing" scientifically

[Wish]

What's a scientific (hydodinamic) name for the "wing". Daughter may do a sci project on the drag affect of varying set degrees and "wing" size. Looking to the engineers out there. JTH... The wings you sent me are perfect and the inspiration behind the project. Thank you.

[MCskiFreak]

Foil, Hydrofoil, wing also is applicable. Thats a pretty heavy duty science project! there is a cool little calculator that nasa has where you can mess with the chord lenths and aspect ratios of a foil to find the drag coeff., lift, etc.

[Wish]

Simple: pull a ski, just below tip, (no skier) behind ski boat with cruise engaged at 15mph with 100ft of 20lb fish line. Fish scale between fish line and tow bar. Set ski up with dif wing/foil degrees and or size and mesure resistance of each. Done. Up for any suggestions though. But keep it simple please.

[MCskiFreak]

Your going to need something alot more sensitive than a fish scale (unless its digital and is acurate to 1/100th) to be able to record the change in load. even with radical with angles the drag will be pretty small.

[Wish]

Hmmm ? Valid point. So what can we use instead or make that might work?

[kfennell]

digital luggage scale?

 

[MCskiFreak]

Youre going to need something like a small inline load cell, or inline scale.

[MCskiFreak]

http://www.digitalscalesaz.com/Jennings-J-Ultra-Sport-Digital-Scale-30kg This may work its accurate to 3.2 oz and is only $25.

[Wish]

Other thought was giving the ski a push and seeing how long it takes to travel a fixed distance. Problem: how do you get the exact same push every time? Keep the ideas comn. Still like the pull and scale idea. Just don't want to spend big bucks on some fancy scientific scale.

[kfennell]

I figured it out.

go out and try to see how much pull you are getting roughly with what you have. 

If it is less then ~ 2 lbs then you can use a kitchen ingredient weight machine. Or if it more, some other type of small spring scale. They are pretty accurate or at least repeatable so they will show the difference between wing angles. You could just mount it on the front of the pylon somehow, maybe just hold it there, and have the rope pull on what is normally the top of the scale to compress it. 

[HO 410]

If you don't have to measure drag in terms of weight simplify the tests and just go ski.

 

Do some sweet math to help form a hypothesis, define your testing scenarios, and write up a skier response card

with scaled response questions (1-5 with 3 being about normal). Ask lots of questions about skier effort and fatigue

over the course of a set. Once the ski is on the turning edge, wing angle will affect the ski's attitude in the water so

you might as well ask questions about how the ski turns.

 

You won't be able to find out that X degrees of wing makes Y pound of drag, but you should be able to show trends

in what various setting do to the ski.

 

 

 

 

[Wish]

Has to be more quantitative.

[skibug]

For a consistent push; you could use a larger or stronger rubber band in a slingshot type fixture with a given pull back distance attached to a real simple trigger mechanism.  You might have to fix something on the tail of the ski as a good contact point with the rubber band.  Then you can measure distance of travel.  If you got a little more fancy you could also measure time from trigger release to ski coming to rest. 

[DW]

You could look at angular displacement. Use a laser level attached to the ski, attach to a rope and pull with the boat and have the level aim at a board standing vertical on the transom. Mark each of the spots and do the calcs for angular displacement. You might even then be able to do some calculations to determine hydrodynamic drag. Actually to measure drag, you could set up a rope that has a flexible bar at 90 degrees attached a couple of feet over so that the load will flex the bar and use the same approach (measure displacement) to determine drag. I would do big incremental changes to see some results (wing on/off, zero angle v.15 degree angle). If you could find a water tank tester (local University might be a source), you could set up a test to measure the drag that way. They would/should have all the measurement equipment handy. Great project, good luck!

[eleeski]

DW is on the right track. I'm not sure you will be able to measure drag effects of a wing against the background variations in load. But ski attitude might change measurably. Photographic comparisons might be able to measure the variations. At least she will learn to superimpose photos on the computer and a bunch of other useful analytical skills.

 

I did a similar drag measuring test in college on trick ski loads and couldn't resolve differences between skis in the data that I could certainly feel on the water. The loads were too variable and too skier dependant (as opposed to ski dependant).

 

Perhaps having the skier put a constant load on the rope and measuring the ski attitude would tease data out of the background uncertainty. That could be a very interesting project!

 

Regardless, make sure she publishes her report here. We are intrigued!

 

Eric

[Wish]

What if we use a pendulum system to push the ski and measure time of travel between 2 fixed points. A weighted pendulum with a fixed high point and trigger release pushing on a small vertical plate attached to the topside of the ski just infront of center. Anyone think there would be any difference in wing size and angles for time of travel?

[wlrottge]

I'd suggest looking at the speed variable as well.

 

Lift and drag vary as the sqare of the velocity. Do X degrees at speed 1, 2,3,4,5 then do Y degrees at speed 1, 2, 3, 4.... and so on for several foil angles of attack.

 

I know quite a bit a/b this stuff as I also race high end super light sail boats.

[MCskiFreak]

How advanced of a class is this for? If its a high school physics class than the calcs for hydrodynamic drag and other calcs are gonig to be beyond the scope of the class.

[HO 410]

Yeah, probably best not to subvert a science class with sociology/psychology inspired design. Similar conclusions, but almost completely different data sets.

[Wish]

7th grade but from my understanding she will have to expand on the experiment for several years if not through highschool. So simple stuff now to get used to the experimental process then more in-depth for each passing year. That's why I think this may be a good idea. As you all have pointed out (above my head admittedly) this project has great potential for expansion. So for now, simple. But later more complexed and in-depth. So don't be shy with ideas. Heck, I'm learning just with the thread. Thanks so much.

[DW]

An excellent idea on the pendulum method, the challenge becomes the water as it will only allow level travel rather than the arc of a pendulum. The effects of a wing on a fin in air will certainly be very negligible. As noted, the white noise of your system (in my case as an example) will be quite large, therefore you will need to make many runs and/or make large adjustments as I noted. You also might consider the project as a how to test project as part one, part 2 could be the wing effect.

 

Another option, but a little more challenging would be to look at streamlines or water flow effects of the wing. Your would need a video camera and some dye or short strings to either dye the water and visualize the flow or attach the string on the surface of the fin and wing and look at effects when making changes. A water tank would be an ideal test setup for that type of test (bathtub with a wet/dry vacuum cleaner? or electric trolling motor? (and lots of towels)).

[MCskiFreak]

@Wish where are you located at. The Dye and streamliners is a great idea, if you are near a university that has access to a tow tank or a tank that will generate a current.

[Horton]

To answer the original question. “Vortex Generator”

 

@DW am so sick of that German kid.

[DW]

JTH, bummer since he seems to be able to drive reasonably well and has the best car by a mile!! He sure put the whammy on them at Spa, the old guy did well too, very impressive drive. Your red boys need to get the hard tire figured out, car does not work the tires enough that is why it is not good on the hards.

 

Awesome JTH: "Vortex Generator"

 

Wish: Here is another idea, one we use in race cars all the time, not sure how it will work in water, but oil drops on the surface. Will give you a great visualization of the flow field. (When "dad's" car shows up with a bunch of oil streamlines on it don't blame me!!). If you make a really quick short run, the oil may not get all scrubbed off, but you will need to get good speed for it to work. The oil stays on the surface and creates the streamlines. You might want to use a slightly heavier oil (we use light motor oil with a grape dye) like thread cutting oil.

[eleeski]

While a slalom wing may look like an aircraft vortex generator, the function is quite different. Aircraft VGs affect the transition boundary from laminar to turbulent flow. A slalom wing is placed at the aft end of the ski so whatever vortex generated will have minimal effect downstream. Now wallboard texture (or fish scales) may behave more like aircraft VGs. Admittedly any wing will generate vortices but that should be a mimimal effect lost in background drag.

 

The slalom wing should add lift (perhaps negative lift) and drag (maybe net negative drag?). There are lots of unknowns (which is why Wish's daughter's project is so interesting).

 

Eric

[The_MS]

Wings are free and Ventral wings are 60.00. Whats up with that?