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HOWTO: Building a deep front wheel fairing
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In a Slowtwitch post about 2 years ago, I wrote I'd try to build a deep fairing out of polyester/fiberglass for my not-so-aero front wheel. Oh well, I finished that fairing last automn, and rode it for about 1500km so far.

But this is Slowtwitch, so let's start with some pictures ...or nothing I will be saying has actually ever happened ;-)
Here you see the front wheel and the finished fairing, before installation:



The wheel is a Mavic Ksyrium SSC anno 2000, with the original stickers removed / replaced with reflective tape.

The fairing is composed of two rings that are posed onto the left and right side of the rim, then fastened together using 9 small screws. The fairing can be removed & re-installed in a matter of minutes.

The cross-section of the 'tyre + brake surface + fairing' approximates a teardrop shape.



I chose that shape because I trust the birds when it comes to aerodynamics of something of similar size and speed-range. After all, they have successfully used and refined that shape over the past 150 million years or so!
(In all that time however, birds do not appear to have figured out dimples yet! I'm confident they will when they learn to play golf.)

This is how it looks after installation on the bike:





People usually do not realize or believe they are looking at a fairing until they are told so, or until I point out the recessed attachment screws and some of the, ehr, 'production defects' to them.

Now the gory bit - how was it built?


Dear Slowtwitcher, be warned! You'd better skip the following lengthy post if you do not fit into the maniac wrench-it-yourself category.

You may however still comment about stuff like seat height or tilt, the wussy triple groupo, the bike pictures not meeting ST standards because the chain is not on the big ring, the Bento box, the SPD pedals, the shabby appearance of my garage...


The first step, and also the most difficult one, was to construct a mold for laying out the fiber. The mold would have to be ring-shaped, and provide a negative imprint of the desired teardrop shape.

I decided to use plaster for the mold, because plaster is resistant to the polyester resin's aggressive chemicals. It is also non-toxic, and a cheap and easy material to work with. You can make it thicker/more fluid by adding more plaster/water, and form it to your desired shape while it has not yet set. And you can still file and sand it afterwards. That gives you a comfortable margin for errors.


A mold for the mold

But first, I had to build a mold for the mold, something to pour the liquid plaster into:



The first picture in the series shows the materials: The greenish stuff are styrofoam sheets which are normally used for thermal/noise insulation. You also see a stick of wood, tape, steel wire and pliers - used to assemble a makeshift compass (...the one I had left from highschool was too small!) - and a cutter knife.

I measured the distance from just below the rim's braking surface to the wheel's axis, and added about 15mm to it - that would be outer radius of the disk I'd cut from the foam. Subtract the depth of the fairing plus about 30mm, and you've got the inner radius of the ring.
Then I cut 30mm wide stripes of the foam and taped them to the outer and inner circumferences of the ring, ending up with the U-cross section mold shown in the second picture.
I tried to work as accurately as possible with the ring's outer circumference, as that would serve as a reference guide for the fairing's outer diameter.


The plaster mold

See that yellow thingy on the third picture!
It's a bit of plastic I cut to the teardrop cross section shape I wanted to give to my fairing, with a notch that fits snugly against the outer edge of the foam mold.
With that stencil, the plaster was then formed, scraped, pulled, forced into the shape shown in pictures 3 & 4.

And that's where, in retrospect, I made two significant mistakes:
  1. Working with plaster in the kitchen is admittedly a bad idea!
    My wife gave me hell about it, and I was banned into the garage for all subsequent work.

  2. The foam wasn't rigid enough! It deformed a bit while manipulating the plaster with the stencil. That resulted in imperfections (slightly undulating surface) that I could not entirely remove by sanding. The slightest imperfection in the plaster mold would later show up in the finished fairing.
    Therefore, if I were crazy enough to attempt something like that again, I would probably first build some kind of oversized potter's wheel, with a robust fixture for the stencil - for producing a more accurate mold.


Laying out the fiber

Another mistake seen in the other pictures is to use household items like enamel paint (that yellow stuff), vinyl glue or wax as mold release agents, and hoping that it will work out. It won't!

I used the same mold for both fairing halves, and had to do a lot of plaster repair work after struggling to separate the first fairing from the mold. Further I had to scrape/sand a lot of paint and plaster remains from the cured fairings ...next time I'll get a mold release agent specifically designed for the task.

In the remaining pictures of the first series you see the messy, stinky, but really the most fun part of the process: Laying out the fiber and wetting it with polyester resin.

I've used two layers of fiber. First a layer of light, woven fiberglass cloth for a better surface finish, then a heavier layer of chopped fiber strand for strength.

On the last two pictures in the series, you see small rectangular bits of fiber that I applied at specific markings, between every second spoke. The purpose was to make the fairing thicker at those spots, so I could countersink the attachment screw heads, to make them flush with the fairing's surface.

I'd like to add a few remarks concerning polyester resin, for those who have never messed with that stuff before:
  • Always remember that polyester resin, acetone and especially the MEKP hardener (methyl ethyl ketone peroxide) are nasty, flammable, unhealthy stuff! Avoid contact with skin and eyes, avoid inhaling the fumes, and keep your work area well aerated!

  • It is better to mix 'a little too much' hardener into the polyester resin, rather then not enough! More hardener will make polyester resin gel and cure faster ...meaning that you will have to work faster!
    Not enough hardener however and the resin will never fully cure. It will stay tacky, and you won't be able to sand or paint it afterwards, meaning that you will most probably have to ditch the part.

  • Prepare small quantities of resin at a time (I used half a cup). Resin always gels faster than you think!

  • When mixing resin with hardener, mix thoroughly but slowly, to avoid formation of air bubbles.

  • Stains of resin can be removed with acetone.
    You can also add a bit of acetone (use common sense!) to the resin to make it more liquid, so it is easier to wet the fiberglass. It won't interfere with the curing process, but the resulting part will be of lesser quality / less strong. For a non-structural part such as this fairing however, this is a non-issue.

Finishing the cured fairings

The next series of pictures shows some work done on the cured fairings:



Pic 1: cutting away the excess fiber.
Pic 2: filing the slots for the spokes and the valve stem.
Pic 3: checking the fit on the rim
Pic 4: cutting and filing small, wedge shaped pieces of wood that are glued to the inner side of one of the fairing rings, facing the holes for the screws on the other fairing. The wooden wedges not only serve as an anchor for the screws, they also center the fairing onto the rim.

I've used the same polyester resin to glue the wood to the fairing, which results in a very strong bond! (...got that great idea from an article about boat construction, where it was mentioned that resin is used for bonding wooden masts to fiberglass hulls)

On the remaining pics the fairing is almost finished. I didn't make pictures of the rather boring & repetitive 'apply bondo / sand' procedure, neither of the airbrush painting process.

The only worthy remark concerning the 'apply bondo' bit is how to make a smooth rim/fairing joint:

Apply vinyl tape (electrical tape) to the rim's whole circumference, where the fairing contacts the rim. Fasten the fairings to the wheel, then apply bondo to the rim/fairing contact patch and smooth it out. Remove the fairings after the bondo has cured (fiberglass bondo won't stick to vinyl tape), lightly sand the fairing's circumference - et voila, you've got a perfectly smooth rim/fairing joint!

I've used matte black paint for the fairing, as glossy paint would emphasize too much any surface imperfections :->
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Re: HOWTO: Building a deep front wheel fairing [sardus] [ In reply to ]
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pretty cool, are you going to sell them?

How long did you spend on this? Would it have been easier/cheaper to have gotten a second job at 7/11 and saved for an 808?
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Re: HOWTO: Building a deep front wheel fairing [sardus] [ In reply to ]
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That is awesome! Kudos to you for taking the time to do that yourself. I would never have the patience.

------------------
My business-eBodyboarding.com
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Re: HOWTO: Building a deep front wheel fairing [sardus] [ In reply to ]
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that is so cool man. Good for you.

I'm curious how it worked out from a cost perspective when compared to just buying a new front wheel. how much did building your own faring cost in terms of buying materials, tools etc?

That issue is, of course, secondary because it looks like you had fun doing this.

___________________________________________________
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Re: HOWTO: Building a deep front wheel fairing [Chris G] [ In reply to ]
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In Reply To:
pretty cool, are you going to sell them?

How long did you spend on this? Would it have been easier/cheaper to have gotten a second job at 7/11 and saved for an 808?

I spent way too much time on this ...count over 30 hours, spread over two months and mostly during weekends!
Selling these kind of fairings might make sense if I figured out how to build them in one hour, but that was not the point ;-)
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Re: HOWTO: Building a deep front wheel fairing [sardus] [ In reply to ]
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Kudos on a very impressive DIY project! I'm curious how much the fairing weighs? And does it disrupt the balance of the wheel?

------------------------------------------------
Ann Arbor Triathlon Club

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Re: HOWTO: Building a deep front wheel fairing [sardus] [ In reply to ]
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very impressive.

reminds me of the time i thought i'd make a bullet proof bike transport case out of 4 layers of laminated cardboard, including some rolling wheels and who knows what else. i thought it would save me a ton of money. in short, it took me a lot of hours, so in the end, i saved nothing ... but it was (painfullly) fun ...





Where would you want to swim ?
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Re: HOWTO: Building a deep front wheel fairing [mtlrunner] [ In reply to ]
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In Reply To:
that is so cool man. Good for you.

I'm curious how it worked out from a cost perspective when compared to just buying a new front wheel. how much did building your own faring cost in terms of buying materials, tools etc?

That issue is, of course, secondary because it looks like you had fun doing this.

Thanks! And yes, it was fun!

From a purely materials perspective: I had to buy the styrofoam sheets, 5kg of plaster, a 400gr pot of resin, bondo, a couple of fiberglass mats and a bottle of acetone - that's about 70 EUR.

The other stuff I already had available - sanding paper, paint, tools like files, drill, airbrush pistol & compressor, etc., and not to forget: a front Ksyrium wheel (which was not exactly cheap, 8 years ago), and a lot of weekend time.
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Re: HOWTO: Building a deep front wheel fairing [sardus] [ In reply to ]
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That is awesome! But is it race legal? "Fairings" must be structural with the exception being a wheel cover. So does this fall into the realm of covers, even though it does not cover the whole wheel?


Steve
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Re: HOWTO: Building a deep front wheel fairing [DaveV] [ In reply to ]
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In Reply To:
Kudos on a very impressive DIY project! I'm curious how much the fairing weighs? And does it disrupt the balance of the wheel?

The fairing adds exactly 382 grams to the front wheel, and at the rim of course, where it matters most :->

Wheel balance is definitely affected by it - the bike is now as nimble as an oil tanker: Sluggish to accelerate and sluggish to turn!

The former is bad, but the latter is actually a good thing, especially when you're in the aerobars: The bike not only is generally sluggish to turn, but it reacts just as sluggishly when hit by sudden gusts of wind or by strong sidewinds, giving you a lot of time to brace against the wind!

I also find the faired front handles more predictably than the unfaired Ksyrium: A stronger sidewind simply means that a stronger force is trying to tip me over, but the wheel keeps pointed straight. That's unlike the unfaired Ksyrium which has a tendency to twitch around in sidewinds.
I'm not quite sure if that's an aerodynamic effect or just an effect of additional mass, but I suspect the Ksyrium's boxy rim profile to be the culprit.
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Re: HOWTO: Building a deep front wheel fairing [sardus] [ In reply to ]
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you got to do all that in the house? nice pimp hand
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Re: HOWTO: Building a deep front wheel fairing [sestivers] [ In reply to ]
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In Reply To:
That is awesome! But is it race legal? "Fairings" must be structural with the exception being a wheel cover. So does this fall into the realm of covers, even though it does not cover the whole wheel?

AFAIK, according to UCI rules, wheel covers and non-structural fairings of any kind are not allowed.
Most Triathlon bodies however relax that rule a bit and allow the use of rear wheel covers only.

My front fairing is definitely not race legal, and that's why I went to some lengths to make it:
1. look like the real thing
2. easily removable (just in case 1 fails ;-)

I've actually participated to one IM distance event with the depicted setup (Bodensee Triathlon 2007 in Rorschach, Switzerland)

But I did not want to argue, or risk being DQed, so on bike check-in I pointed out right away to the race official that both the rear and front were covers, and if it was OK to race with them, otherwise I would take them off and be back in 5 minutes.

He took a very dubious look at the wheels, then at me, and then he asked in a very serious tone: "Das ist egal! Aber Sie haben ja keine zusätzliche Gewichte darin versteckt, oder? Das ist nämlich verboten!". (In English: 'That doesn't matter! But you have not hidden any additional weights in them, have you? Because that's forbidden!')

I kid you not!

My puzzled look and my answer "Was? Gewichte?!?" ('Huh? Weights?!?') were apparently convincing enough, and I could pass.


So I guess it depends on the particular race, and on how picky race officials are on one aspect of the rulebook or the other.
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Re: HOWTO: Building a deep front wheel fairing [sardus] [ In reply to ]
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Two questions:

1) Why not use foam for the spacers instead of wood. Or use balsa wood instead. Would make the setup lighter.

2) Did you vacuumed bag it? It might be lighter if you did.
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Re: HOWTO: Building a deep front wheel fairing [Raptor] [ In reply to ]
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In Reply To:
Two questions:

1) Why not use foam for the spacers instead of wood. Or use balsa wood instead. Would make the setup lighter.

2) Did you vacuumed bag it? It might be lighter if you did.

I considered other materials, including foam, but guessed the screw threads would strip after only a few installations/de-installations on the wheel. Also, I had this bit of fir wood lying around in my garage...

I removed the excess resin by dabbing the wetted fibers with paper towels, as I don't have the required equipment for vacuum bagging.

Other ways for reducing weight would be to reduce the number of spacers (using only 5 instead of 9), using carbon instead of glass fiber and only one layer of it instead of two ...but then, the fairing would become so flimsy that hanging the bike by its front wheel to my garage's ceiling would be out of question.
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Re: HOWTO: Building a deep front wheel fairing [sardus] [ In reply to ]
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Nice project very well executed and they look very professional. I also thank you for proving to the rest of us, that it is probably a better idea to buy a used race wheel (much lighter, cheaper if you consider both cost and time) than attempt a project like this;)

*********************
"When I first had the opportunity to compete in triathlon, it was the chicks and their skimpy race clothing that drew me in. Everyone was so welcoming and the lifestyle so obviously narcissistic. I fed off of that vain energy. To me it is what the sport is all about."
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Re: HOWTO: Building a deep front wheel fairing [sardus] [ In reply to ]
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Great work! good write up and pics - - -- and the finished bike looks good too. You should get some kind of ST award for doing what it takes to get what you want.
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Re: HOWTO: Building a deep front wheel fairing [sardus] [ In reply to ]
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I like it!

Too bad a company like wheelbuilder will NOT make one (because of UCI and all that), which means all of us will either have to DIY, or just purchase an aero front wheel (new or used).

But, I'm saving this page and showing it to a local fiberglass maker to see if he can make one for me. Eat your heart out, 1080! :)



----------------------------------------------------------

keep it simple , keep it real .
--Brett Sutton

But i dont really know that much about bikes. I just sit on em and do as i am told. peddle. hard and fast.
--Chrissie Wellington

I think the best way to get faster is to enjoy it, the more you do the better you get, so go out and enjoy swim, biking and running, and don't feel to constrained and just do lots.
--Stephen Bayliss
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Re: HOWTO: Building a deep front wheel fairing [Russ Brandt] [ In reply to ]
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In Reply To:
you got to do all that in the house? nice pimp hand

My urban English is not that good. I had to look up what the expression 'nice pimp hand' means ;-)
Nice thing about ST, you learn something new every day!

I have to add that my wife made me vacuum-clean the whole house after my brilliant idea of building the plaster mold in our kitchen.
To further restore good karma, I also cleaned all the windows, all our furniture and other stuff I'd never thought of cleaning before - because every speck of dust in the house would be ascribed to my plaster work during the following weeks :-/

Good karma then took a hit again, when I started to mess around with polyester resin in the garage!

That stuff stinks to high heaven but I knew that beforehand. So I had carefully stuffed damp rags around the door-slits and opened the garage entry door and windows to let those noxious fumes escape, with moderate success. You could still faintly smell that stuff in the house for a day or so.

But I was able to put forth my stubborn will and not being kicked out of my house for the polyester work (it was cold and rainy outside!)
I therefore can still wear my 'pimp hand' title with pride, do I?
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Re: HOWTO: Building a deep front wheel fairing [sardus] [ In reply to ]
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Thanks for the how to. I tried it. Here it is.
I did it for the looks mainly. I like it.
Mine has a foam gasket and I later added more foam on the
wood blocks where its close to the rim for added support.
Trying to achieve noise free operation takes a few attempts.

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Last edited by: Dman531: Nov 3, 11 23:44
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Re: HOWTO: Building a deep front wheel fairing [Alfalfameister] [ In reply to ]
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Alfalfameister wrote:
I like it!

Too bad a company like wheelbuilder will NOT make one (because of UCI and all that), which means all of us will either have to DIY, or just purchase an aero front wheel (new or used).

But, I'm saving this page and showing it to a local fiberglass maker to see if he can make one for me. Eat your heart out, 1080! :)

Why? Its going to cost a lot to have a custom one made. You really have no idea if its going to be any faster, just adding a fairing onto the front wheel doesn't mean faster necessarily. Also you can get a used SRAM 80 or Jet 90 etc for under 500 for the front and you know its fast. I'm just not seeing the point in having someone build something custom like that. Its a cool diy at home project but to pay someone to do is most likely a huge waste of money.
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Re: HOWTO: Building a deep front wheel fairing [Grant.Reuter] [ In reply to ]
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Third world country. Cheap labor. Probably can offer someone US$20 (labor only), and that guy will offer to make me two for that price.

Addendum: I never did it. And this thread (and that post) is two years old. :)

[edit] as Grant pointed out, "...three+ years old." :)
Last edited by: Alfalfameister: Nov 3, 11 23:16
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Re: HOWTO: Building a deep front wheel fairing [Alfalfameister] [ In reply to ]
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Son of a biscut. people need to stop bumping 3+ year old threads...
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Re: HOWTO: Building a deep front wheel fairing [Grant.Reuter] [ In reply to ]
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Sorry guys for the bump on the old thread. My pictures are not coming out right. Being rotated by imageshack. I don't know whats wrong. Oh well. I tried.
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Re: HOWTO: Building a deep front wheel fairing [Dman531] [ In reply to ]
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Use photobucket and increase the size of it.
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Re: HOWTO: Building a deep front wheel fairing [Dman531] [ In reply to ]
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A few more pictures above if anyone cares. I got it straighted out.
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