Fenders-Friend or Foe

[Noskills]

I have recently seen alot of photos of league racer cars which use rear wheel aerofoil shaped fenders. Yet I dont see many on DT use them or even discuss them. Are fenders over-rated? They look cool but do they help with speed?

Thanks for the input,

Seth (Someskills)

[rkibby]

there is video from [no advertising for this vendor] just posted the other day about this topic.

sent from somewhere in the cornfields of mild earth

[rkibby]

http://www.youtube.com/watch?v=slbDbbi-5MI&sns=em" target="_blank

hope this link works. on my phone.

sent from somewhere in the cornfields of mild earth

[FatSebastian]

Are fenders over-rated? They look cool but do they help with speed?

The topic has seen discussion on DT, and fenders can help with speed, but this post by Sporty had left me with the impression that the gains are neither huge nor necessarily automatic, as it relates to kids' races.

[Noskills]

That John H is a hoot. Just be glad I don't make conclusions on medication safety the way he makes conclusions on the effects of fenders.
Noskills

[sporty]

Thoughts on the video.

As I said a few years ago, I did testing with fenders, pretty good testing with a proffessional wind tunnel tester and, track and timer.

I did not find the wind every reached the rear wheels, the tiny ait strips, did not even move. I only seen the tiny strips move at the frotn nose, front wheels and 3/4 to 1 inch past the front wheels.

The air is to weak. Plain and simple.


And john was right about one thing, it is very easy to go backwards with fenders, then improve. (very easy to go slower with them, then without).

Now, John is a great car builder and hes fast, When you do it for a living, you got to be good or you dont have a biz. This is all he does, he does not have another job that i am awhare off and well so you can imagine the hours and time and years into this. Hes good for a reason folks and he does deserve a fair amount of respect. he has earned it.

However, pre built cars, tuned cars for scout races is the reason he is banned here per the owner of the web-site. We will by pass the drama as i am just stating the information I am awhare of.


Now, the things I want to point out in regards to the video. I would have liked to see the car staging of the car with the fendors on, not just 1 shot of them off and the last run with the car at 4.80oz. there was only one run. three runs should have been done, in my view.


In summary, correct me if I am wrong here. but I see that much change in star staging and so thats why i feel the shot of the staging and release of the car with fenders should have been included.

My track and timer testing was done on a 32 foot track. So a 42 foot track may infact yield a plus.


My issue, is i feel you have to toss out a .01 deviation for staging differances. Because very few people are able to reset a car perfect on a track and not have some sort of deviation in time, even in the league racing. I seen allot of .01 and a few that do it darn near perfect. And i think John is clearly in that level. However, Im not understanding why not show that. i think its criticial to show that in a video to show its a plus to have them,


My testing was of scale speeds of 180 miles per hour to 270 miles per hour. I did not see air move the tiny air trips until over 320 scale miles per hour.

I also would like to have seen a check of the balance point, just cuz you put some tungsten putty under the car and close to where the finder might have been. It also changes the balance point. I test this and know this is true.

And when you are looking at changing a balance point just a tad, you are either speeding up a little or slowing down a little.

So i hope we will do another video, adding in those additional details and footage. If he did that, Then I'll be a true believer.

Because I am always open, that my testing had a fault some where.


I only found little gains with front fenders, newer seen a gain with rears. So thats why I am mentioning, what i felt was left out of the video and should be added.

And Im sure im coming of a bit criticial, Its just i spent some time testing and I tell ya, I wanted to to work, Cuz I liek fendors. I just could not get it to go with rears on, only with fronts and it was tricky.

Also I found my desing of car with the flaired sides, to push the air away. You notice the square sides, strait up and down. I taper mine and angle them. because i found this was a aero advantage of pushing the air away, not really pushing, but allowing it to flow away.


Now, a bit of additional review. I found that the front wheels, when the air dropped down it can bounce on the side of the car and cause dirty air and vortex and stir. but it also dropped over, before it reached the rears.

Now, if the scale speeds we set the wind tunnel were off some, then Im always open to say, that vortex, turbulance might reach the rear wheels. if my gauges were off some on the wind tunnel machine, as I said it was around 320 scale air speed, it did reach the rear wheels.

But there is a slight chance, that the track might be bouncing that air up and is slightly getting to the rear wheels.

But no fenders needs to resolve this, flaring and lowering and slanting the sides, resolves this issue also.


Now, I feel John and a few exsclusive people have the talent and ability to make it work. I feel the number is small and the risk of slowing the car down is far greater of a risk, then using them.

Unless you are racing the best of the best in your scout pack and are top league racers parents kids. I do not see it giving you the edge to win.

But fendors are cool looking and seth has a cool car, seth, chime in here pally.

Sporty

[Noskills]

Sporty,
As a scientist, I was also critical of his testing methology. I don't me to dis him as he knows his cars and I buy some of his stuff but he needs to beef up his scientific rigor. ( and filming/ editing skills ) I think there are a few things he could have done to show the difference such as show 3 rounds per race and provide averages. He should have found a way to account for loss of speed due to run number such as regraphite every x runs. Repeat the process few few time off camera and provide results-speaks to reproducibility the hallmark of good science.
Either way I have decided that they look cool but I will pass on using them. My daughter wants a new car for regionals as my sons was faster and I was trying to think of some cute add ons for her. Apart from less wood, a more agressive COM and more detailed prep (she is more patient than my son) I got nothing.
Seth

[sporty]

Seth, thanks for chiming in, I follow your Facebook, derby posts. if you know who I am, my real name, ect. I have mentioned on there.

I recall he said no lube, but not sure if he meant graphite or was using nothing, ect. I feel for me, not showing 6 runs or 9 runs and showing the staging. Because i see that much deviation in just in staging. and the last 1 run, with it at the same weight and no fenders. I do not understand why only 1 run was shown.


I'll also share with you the fenders i would recommend, would not be that style, the ones we made, and testing that showed a real impact, were of a different design, but this was also with the scale of the wind speed tunnel testing, exceeding that of race conditions.

Then as I also mentioned, I found flairing the sides down to a point, gave a simuliar effect.


Sporty

[5kidsracing]

He was performing a simple test to show that fenders when used right will make an impact on speed. He was not paid to do a complete scientific workup to please the masses.

The reality of the situation is that wind tunnel experiments do not account for all the variables associated with running cars with or without fenders. It may show the aerodynamics and air flow over the car, but it doesn’t take into account so many other variables when a car is actually running down the track or when a car is in a real race with others cars. I am sure there are real Engineers out there, like me, that have designed something using material or a design feature based on lab or test results only to find out that in the actual application it doesn’t work so well.

The fastest racers have proven over and over again that wide wheels cars with fenders win the majority of races over non fendered cars. This is based on real races on a real track against other real cars, not a hypothetical situation. These guys build and race every month and they offer this type of information to steer people away from all the incorrect, untested, unworthy and sometimes ridiculous pinewood derby information on the web today.

For scout racers such as yourselves you should probably not use fenders to try and gain speed. Use fenders for the look or to add to your theme, but not to gain speed. Fenders for speed is probably outside the scope and purpose of this website.

[Noskills]

5 kids,
Perhaps I was bit hard on John H. I mean no disrespect and like I said I buy his stuff. Because he knows his stuff.
Noskills

[5kidsracing]

I am not trying to stick up for John, he can do a fine job all by himself and he doesn't need any of my help.

I am just trying to shed some light that there is good information out there and bad and unfortunately it is up to people like you to sort it out. In my opinion trying to push methods and information based on little success or experience is disturbing. We need to be making this easier for our scouts, not harder. It seems if an easy method is brought up by a league racer it is automatically shot down here. Most of the league racers have moved away from posting on DT for that very reason. Maybe that mentality was brought on by issues years ago, but I don't see people trying to push product or vendors here now. It has left DT with the same information being recycled year after year. Every year I show many, many scouts how to easily build a pwd car. I show them many of the same methods that I use in league racing. They have fun and they learn from the experience. I understand what DerbyTalk is all about, I just think it could be better.

[chromegsx]

Personally, I'd rather see video on a fully prepped car (best of the best all the secrets incorporated) with fenders and then take them off (and adjust weight without changing either the vertical or horizontal COM) and compare the effects. Then do the same with other cars on the track that are either ahead or behind on either or both sides. But for a typical "above average scout built/kit level" car it does appear that there is some value. I definitely want to test for myself. I keep seeing/hearing they may hurt you if not done right but then nothing is said about what can be done wrong or right. Admittedly, I haven't taken the time to search yet, but....

[sporty]

I am not trying to stick up for John, he can do a fine job all by himself and he doesn't need any of my help.

I am just trying to shed some light that there is good information out there and bad and unfortunately it is up to people like you to sort it out. In my opinion trying to push methods and information based on little success or experience is disturbing. We need to be making this easier for our scouts, not harder. It seems if an easy method is brought up by a league racer it is automatically shot down here. Most of the league racers have moved away from posting on DT for that very reason. Maybe that mentality was brought on by issues years ago, but I don't see people trying to push product or vendors here now. It has left DT with the same information being recycled year after year. Every year I show many, many scouts how to easily build a pwd car. I show them many of the same methods that I use in league racing. They have fun and they learn from the experience. I understand what DerbyTalk is all about, I just think it could be better.

I think you know I proved my myself in 2010 in league racing and blue grass nationals. And i cna only speak for my testing on a track and the high end professional wind tunnel testing.

he league races I uses to stop in and see now and then, back then, fenders were a hit and miss, i seen wins with and without them. Just because i could not get it right, does not mean. Im against them. But it does mean, wityh my level and skill and ability, If I found it very hard. its not likely a average scout could ever do it.

I think the real reason many high end racers dont come here, is there is not much for them to learn here, usually they are at a higher level then many scouts. only a few of us remained to help the more typical scout.

So, yes, you are right allot of the same info, is repeated, yearly. because very few of them ask or want to learn or get to the type of level of a league racer gets to. it's just a totally different thinking process.

I'm glad you still come here and I enjoyed watching you develop and become a really good car builder and elite racer. So thats something I am all positive on.

I tried my best to Give a fair and true account of the video, after all, Im not out there selling the product, he is. and i think anyone selling a product is held to cristizm of the product. thats all, its normal.


When Top racers, said to me in fall of 2009, my stuff was junk and what I shared on here and helped people was junk and I was not fast. I was told to put up or shut up.

Well, as you know, with a wooden track and little fancy tools. I entered into the adult league racing, for the first time. with not even having the same track to test and tune on. Left to tune and guess my drifts on my kitchen floor. to send the cars in to race.

And team sporty won in two divisions that year for rookies into the adult league racing and i took personnally 3rd place in the blue grass national championships. and it was a feeling of great luck and gratitude, that what i share here and so forth, works and works good enough to compete at that level.

In fact, a few of the things I came up with on my own or as a team. was shared for free, and helped a great deal of other racers go faster. my design and idea of the pro hub tool and the now common mod to the hubs. It did not take long for my stuff to get out there and be used and still being used.

So I will stand by my testing and so forth, in regards to the results I found. As I mentioned, mine was on a 32 foot wooden track and never on a 42 foot track.

I think you will agree, the average scout, does not have access to a track or will buy one and a timer to be able to find out, if they are faster and it is very hard to get it to be a advantage and the marginal gain, out weighs the typical standard races through out scout america.


I have asked a few times for a new topc section for elite and advance pro racers, But it did not happen. I feel there should be, but thats not my call.

But i certainly, feel you you wanted to do a detailed and indepth article and so forth on it, here, how to, the shape and placement, so forth. Would be huge and well read by many, including me.

Id love to read a good article, post, that explains, the angle and shape and type of material used, how to place it and where not too and how to angle it or ect so that it does not make contact with the rail. I have not seen a post like that yet. and there maybe one someplace out there, if so, can you please link to me. I would enjoy reading.


And me, to, This is not about John at all. This is the same thoughts and process, most of us ask and go thru when a question is asked or information is sought. I've stated my findings and info and pictures there a few years ago. as indepth I could and so forth. I think the same has to be done to show the gain and it works. not just a video of it going down the track, that had some gaps, that I felt, why was it left out. hes selling the product, no me.

Sporty

[FatSebastian]

Very interesting discussion. Thanks to all.

...he needs to beef up his scientific rigor. ( and filming/ editing skills ) I think there are a few things he could have done to show the difference...

I appreciated that the referenced video was edited down somewhat; if an online video is longer than 3 to 5 minutes, I hesitate to play it. Too many times people post raw, unedited videos that drag out for a half-hour or more with a lot of unedited dead time. Like 5kidsracing, I presumed that the video was merely a demonstration of something that had probably been proven long before to the satisfaction of its producer, rather than a conclusive record of a scientific experiment.

With that said, this specific video really seems like a bit of marketing as much as it is for general information or education; therefore, if a viewer comes away with an unintended or incorrect impression (due to editing, or whatever), then the promotion has perhaps failed to serve its envisioned purpose, and the blame wouldn't necessarily reside with the viewer.

It seems if an easy method is brought up by a league racer it is automatically shot down here.

I have not gotten the impression from anyone on DT, or the video, that fenders are an easy method. The video said [6:39] "Get the right kind of fenders. Trust me: ya gotta cut 'em the right way, and ya gotta shape 'em the right way, or they will kill you."

If I learned nothing else from the video, it is that the benefit of fenders "done the right way" appears to be only measurable in milliseconds -- not hundreds or even tens of milliseconds -- and I think this explains why they may be low priority for kids’ cars.

[Ickabod]

I personally found the video and resulting commentary on this thread to be very helpful. The more knowledge I gain the better I will get. This is only my second year building derby cars and I can tell you that I am not at the point where adding fenders for .01 faster time is on my to-do list. I am at the point where I need to learn prep processes and alignment procedures and be able to IMPLEMENT them properly to gain speed. But I will file this thread in my subconscience and will hopefully recall it (like FS does) later in my building years when I am at that point. Just seeing cars by Sporty and 5kids run at the MAC derby was amazing and showed me that I have a lot to learn. And evenually I would love to be to the point where .01 seconds makes a differece for me.