Use of Kevlar

[Tim Reed]

Is it legal to use a Kevlar diffuser? I thought I remember someone saying something about using Kevlar and Carbon for safety purposes, and in places that "didn't lick the wind".

TDR

[Mike B]

Tim,
In the GCR, in the FC/F2 section:
Under chassis, the use of composites using carbon and/or kevlar reinforcement is prohibited.
Under bodywork and airfoils, the use of composites using carbon reinforcement is prohibited. I take this to imply that kevlar is permitted.
Carbon is not allowed anywhere, but Kevlar can be used in non-stressed applications.

[Tim Reed]

Mike-Thanks for the info. I will assume that a diffuser is "non-stressed" component... I wonder why you can't use carbon?

TDR

[Richard Pare]

Kevlar in bodywork was legalised about 6 years ago after I requested the legalisation of composit nosecones - strange how they are now in use and considered to be in compliance with the rules never reworded!

Carbon still has the stigma, rightly or wrongly, of being too expensive for club racing in these cars. That may change eventually, but don't hold your breath!

[Mike B]

I suppose a diffuser could be considered stressed if you bolted or riveted it every 6 inches and bonded it
I think Richard is right about the only reason Carbon is illegal. Those who have worked with Kevlar or bought Kevlar components know that it isn't much less cost than Carbon.
p.s. let me know if you need a diffuser...

[robbie ferstl]

mike, do you make diffusers, or do you have an extra one laying around?

[Mike B]

We do (see the Gyrodynamics banner ad above.) All the ones I have are spoken for, but we are making more as we speak. Let me know what you think.

[Matt M.]

I made a kevlar/glass one 2 years - It was almost bullit proof
You don't have to worry about dragging it around - it will take a season to wear it out - The problem is cutting the stuff!! Its almost easier to cut it with a saw blade after it has cured!!

I would think the problem with the carbon is the shards it creates when "reformed"...Kind of creates havoc for other people....Nasty splinters too!

[montfort]

Mike B,
Do you guys make them for the older cars,i.e. 88 Reynards?

[butchcfc01]

MKIE B. would also like to know if you have one for 88 Reynard and do you have a photo as one is not shown on your GYRO site.
Butch CFC 01

[Kris P.]

Ditto what Butch said! For some odd reason, the pics of the jack and the diffuser won't open on the web site. Thanks!

Kris
FC #77

[Mike B]

I'm not sure what's going on with the website. The pics open on my pc but they do open slowly. That's what I get for trying to make my own website
If anyone has questions or needs more info, contact me either through the website e-mail, or the e-mail in my profile. I'd like to respect Doug's request to limit the retail-type dealings in this forum.
Based on all the questions I've received, I will probably expand the website with more detailed info in the near future.
Thanks to everyone that has inquired so far!

[BrooksHall]

Mike I would like to know if you have one for a '88/89 Reynard also.

MH

[Phulkrum]

Mike,

I had no problems with the pics on your website. Great idea on the camber blocks. I usually don't mess with the camber too much trackside (unless tire temps are way off) only because checking toe after every adjustment is impractical on a busy weekend.
Van Diemen should have made it possible to make the camber adjustment on the bottom of the upright like my old Reynard, thus eliminating the change in toe. Question, are the shims slotted so they can slide down into place or do the allen head bolts (that can be seen in the photo) have to be completely removed before placing the shims in?

[Mike B]

The shims used are the standard Van Diemen rear camber shims so yes, they are slotted. You only need to loosen the allen bolts and drop in the shims. I agree that Van Diemen kinda screwed up on that but they figured it out in '97. There were too many times that I didn't adjust camber when I really needed to because I didn't have time to re-set the toe. Not anymore! Now it takes a minute or two to change camber with no change in toe.

[Steve J.]

Kevlar really is a great product, and it works very well for abrasion resistance. Using it for an entire diffuser would about triple the price over fiberglass, and most of that money would be wasted in areas that don't need the benefits of Kevlar.

As far as diffusers are concerned, you are probably thinking of the same areas that wear out as I am; those being the part right under the front of the gearbox, and the bottom of the fences.

Probably the best thing to do is to place about a 12"x12" square of Kevlar into the gearbox area of the diffuser when molding it, and possibly making the fences out of Kevlar entirely. This should give the intended results and keep the cost low. Remember, no matter what type of core material you use (foam, aluminum honeycomb, etc.) if you go sliding off sideways into the pasture, the core and resin will probably give way even if the Kevlar stays intact, so repairs will be needed.

A guess on added cost for the 12" square and fences of Kevlar over fiberglass would be about another $100, or something like that.

[ December 17, 2001: Message edited by: Steve J. ]

[Mike B]

The design of our diffuser lends itself well to making the fences out of a different material. After some discussion, we might offer a "kevlar option" that would consist of kevlar inner and outer fences to resist abrasion. If there is enough interest, we could offer this for around $75. Send private e-mail to my profile or through the Gyrodynamics website.

p.s. Doug, sorry about the plug, it won't happen again. Promise.

[kspencer]

Ditto Mike, I have an 89 Reynard that is also in bad need of a new diffuser. Sounds like there are 3-4 guys here w/ Reynards that are interested in your diffuser. Enough to do a run of them for us CFC guys? Thanks-Keith

[dc]

Just to set the record straight, I don't have any problem with site advertisers and/or supporters who discuss or answer product-related questions on the site directly. This forum is intended to be a two-way street. It should benefit everyone involved.

As long as you have a banner ad, feel free to plug away. We just frown on companies using these free forums as advertising for their company without some return for the audience that is provided. For many companies, small and large, this is about as specific of a targeted audience as you can get. And I think that our past and existing advertisers can substantiate, that the support shown here goes a long way in the minds of the racing community.


Cheers,

doug


(Mike, we'll have to work on that site of yours with all of this increased traffic )

[Mike B]

Keith,
Due to the interest in the Reynard diffuser, we have started work on a version for that car. It will be very similar to the one on the website. If you're interested, send me an e-mail and we'll add it to the production.

Doug is right. For the money, advertising on this website CANNOT be beat. We fit the description of the small companies that Doug mentioned, being only a two "man" outfit, but that awesome banner ad that Doug created for us that you see in the upper right corner has far exceeded our expectations. Even with my crappy website .
If you own or are associated with a company that sells products even remotely racing-related, I encourage you to talk to Doug about doing a banner ad. If you're not associated with a potential advertiser, I encourage you to click on the banner ads (not just mine) and support the people who support "our" website.
And, once again, thanks to Doug for providing our corner on the web.

[BrooksHall]

I would like to add that without this thread I would have never known I could get a diffuser for a Reynard. Even though I am on the list to buy one I never felt like Mike was trying to sell me anything. I do aggree that a vendor should not use this board as a sales tool without supporting the website.

Having said that I have some wonderful lake front land for sale.......

[kspencer]

I want to apologize for any rif I may have caused with my question to Mike and using this forum to gain insight into my own personal needs. I sometimes (like all of us busy people) have a tendacy to not read every thread response which lead to my question re: diffusors for these old Reynards. In retrospect, I read the entire string and missed the part about contacting Mike directly. Sorry guys, won't happen again

Keith

[dc]

Don't sweat it, the forum s out there for stuff like this.

Glad it could help.

[Dave]

So is this diffuser something that would work on an '84 Reynard? From what I know about the new Reynard I can't think of a reason that it wouldn't work. The back fairing are the same aren't they?

[Mike B]

Dave,
Maybe Purple Frog can help us on this one. If I'm not mistaken, the '84 didn't have a diffuser. However, with a little ingenuity and maybe some angle brackets, ours could probably fit. What I would recommend is making a rough sketch with a few reference points (ie. back of the gearbox, wing mounts, etc,) and general areas on the diffuser that you would mount to. Ideally, we would like to deliver a product that doesn't require any cutting or grinding and all the associated problems with needing to re-seal any exposed core material. It would be best if all that's needed is to drill holes and mount it.
I'm surprised that the interest in Reynard diffusers has almost rivaled that of the Van Diemen. I believe that our diffuser may be adaptable to just about any car, with varying levels of "fitting." We're even doing one for an S2000!

[Purple Frog]

Oh yeah, I thought about a diffuser on an '84 Reynard. Why anyone would consider me a source of expertise is a complete surprise to my Tequila pickled brain. Some real engineering thought would have to be put into an endeavor of this type. My thoughts developed mostly late a night, in the shop, on Tuesdays after races at high speed tracks.

For one, if the diffuser is to be really effective the car would need to sit low. Two, roll would need to be controlled better than stock to prevent the loss of "contact" between the ground and the diffuser. Three, the rear wing would need to be downsized, otherwise one would have too much downforce, and too much drag.

My preliminary design sketches called for stiffer springs to enable a lower ride. Then a lowering of the radiators to be flush with the bottom of the car. Followed by substituting in a low drag rear wing from a newer car.

One obstacle may be determining how stiff to go before you shorten the life of the rockers. Two, determining the fore/aft placement of the newer wing.

Because one can't lower the car too far without hosing the original suspension geometry, I gave thought to fabricating a lightweight (AL.) lower body to attach to and hang 1" +/- under the complete car from the leading edges of the radiators back into the diffuser. (ed. note: that would also serve as the nitros tank)

It is sort of like putting a diffuser on my 97 Expedition. When its all said and done it would still be a 97 Expedition.

Then there are the rules... In the SE it would go unnoticed. I think in other divisions with CFC somebody may say something.

[Dave]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Purple Frog:
Oh yeah, I thought about a diffuser on an '84 Reynard. Why anyone would consider me a source of expertise is a complete surprise to my Tequila pickled brain. Some real engineering thought would have to be put into an endeavor of this type. My thoughts developed mostly late a night, in the shop, on Tuesdays after races at high speed tracks.

For one, if the diffuser is to be really effective the car would need to sit low. Two, roll would need to be controlled better than stock to prevent the loss of "contact" between the ground and the diffuser. Three, the rear wing would need to be downsized, otherwise one would have too much downforce, and too much drag.

My preliminary design sketches called for stiffer springs to enable a lower ride. Then a lowering of the radiators to be flush with the bottom of the car. Followed by substituting in a low drag rear wing from a newer car.

One obstacle may be determining how stiff to go before you shorten the life of the rockers. Two, determining the fore/aft placement of the newer wing.

Because one can't lower the car too far without hosing the original suspension geometry, I gave thought to fabricating a lightweight (AL.) lower body to attach to and hang 1" +/- under the complete car from the leading edges of the radiators back into the diffuser. (ed. note: that would also serve as the nitros tank)

It is sort of like putting a diffuser on my 97 Expedition. When its all said and done it would still be a 97 Expedition.

Then there are the rules... In the SE it would go unnoticed. I think in other divisions with CFC somebody may say something.<HR></BLOCKQUOTE>

Holy cow, this sounds like work. Count me out for now.

One question though, what is the failure mode for the rockers? Do they crack or bend?

[butchcfc01]

Haven't had one fail (crack/bend).Obviously a wreck or two have caused some re-buildable
moments.But they've held together very well.
butchcfc01

[Purple Frog]

When a rocker starts to fail on an '84, it will usually do so on the longer half. What you will see is a slight concave dimple starting to form on the top flat surface a few inches out from the pivot.

If you aren't looking for dimples, then you may notice that the corner weights keep changing every session, as the rocker bends a little more.

If you are real brain dead like me, you'll notice that the car bottoms real bad coming out of turn 1, then going up the hill you see that one front wheel isn't touching the track. [img]smile.gif[/img] Of course I went 3 more laps to finish the race, but that is another story.

[Mike B]

Gosh, all I wanted to do was hang a diffuser under it!
Seriously, PF is right about everything he mentioned...
BUT...
Yes, the diffuser would be more effective when it's closer to the ground, but I believe you would get some benefit adding it to the car as is, albeit not as much as you would if it was lower.
Yes, the wing should be downsized, but not because you would have too much downforce. Remember that a diffuser offers more balanced downforce because it acts closer to the CG of the car. Yea, it's hanging off the back, but the area where the air is accelerating most is ahead of the diffuser (higher velocity=lower pressure.) Drag is the main consideration in downsizing your wing, at least on the older Reynard. You have no doubt noticed the rear wing elements getting smaller over the years, even my '95 wings are bigger than the '98's and newer cars. This is the next area of development for GYROdynamics but the results are a few months away (stay tuned.)

[butchcfc01]

I,stand corrected!P.F.is right,when i've had repairs made PRINCE (PAT) has made them stiffer from stock,however the dimples do show up but,never has a rocker failed except under heavy crash (OOP'S)damage.
butchcfc01

[Rex Burkheimer]

Dave, responding to your original post: "So is this diffuser something that would work on an '84 Reynard? From what I know about the new Reynard I can't think of a reason that it wouldn't work. The back fairing are the same aren't they?"

I believe after '84 Reynards did not have the enclosing bodywork under the rear wing, but rather had a bolt-on rear wing assembly attached to the gearbox, as most other designs did. The rear bodywork is a bit wider than later chassis also, which typically have been narrowed and tapered as much as possible to free up airflow past the aero elements, upper and lower and diffuser.
For the diffuser to work, you would need to be able to stretch a line at a 7-degree angle up and back from a point approximately below the flywheel. My recollection is that that would take some surgery.

[Purple Frog]

Rex,
Maybe I can test out that 7 degree rule. My 84 has the fully stock enclosed rear body. From across the shop, it almost looks like one could follow the contour of the original bodywork underneath. It starts rising right under the flywheel.

[Steve J.]

I believe you have an error in the interpretation of the seven degree rule. That rule applies to the maximum angle from mean air flow that will not introduce separation from the surface. The rule also applies to a single sharp bend (until the air flow reaches a new localized "mean" direction) and a certain limit of Reynolds numbers. The radius at the bend is also critical.

If you have less than seven degrees, that's fine, but the diffuser will be less effective. In other words, get as much angle out of it as you can while still keeping the flow attached. You need to take into account some of the flow characteristics of the underbody, including some transverse flow. The absolute best profile is a (correctly chosen) airfoil section.

If you had more than seven degrees to work with, there are some tricks that can be used to keep the flow attached. But that's a story for another day.