Shiv bento box was above BB. With new Shiv, now in downtube, with water box doing big foil behind seat tube.

P5 disk, apparantly, will go with bento box above BB (same as P5X). Hopefully same for P3 disk.

Not sure what is better in wind tunnel and real life, probably depending the way you implement it, and if you use disk wheel or not, and other aero parameters...

I've heard second hand that the Specialized engineers say the Shiv is significantly faster with the rear reservoir than without. I can't remember exactly but it was in the range of 7-11 watts.

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Ed O'Malley
www.VeloVetta.com
Founder of VeloVetta Cycling Shoes
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Yes, of course, faster

(Watts gain depending on speed, and specific case)

for the same width, a long Naca shape is better than a basic nearly round shape. Intrinsically faster, and also in this specific case stabilizing turbulence around, from the legs.

Same way a disk wheel is faster than non disk wheel. Same principle, mostly.

We tested storage in a number of areas and there was no penalty or gain placing a storage unit (the same width of the frame) above the BB.

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Dan Kennison

facebook: @triPremierBike
http://www.PremierBike.com
http://www.PositionOneSports.com

Relating to the latter, I recall someone saying they've tested the Felt IA frame with the draft box (As with the orbea image posted, sits behind the seat tube but above the wheel) and it saved some watts. It wasn't on the IA thread so it'll be hard to find but hopefully who ever said that chimes in instead.

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808 > NYC > PDX > YVR
2024 Races: Taupo

It is nice to have 1 or 2 bottles down in your main triangle for training rides. With my P4 bottle in place as a storage unit, I have no space down there for hydration.

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Alex Arman

Strava

assuminmg that the storage would be smaller tha a bottle - like just enough for CO2, Tube, Lever, Tool, 20 bucks and a gel - could the 2 bottle braise ons stay in the same place?

Im trying to think of that guys name that made a goodlooking custom carbon one - was it @galdren?

Good point. Something like the Spec Diverge SWAT box.

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Alex Arman

Strava

Exactly this... It would blend right in if the frame was foiled carbon and the box is the same color... Maybe even a slightly curved top for aesthetic

I was thinking that too... a malfunctioning drink reservoir is still a legal aero fairing

A fluid container can be made thinner and any contour to extend the foil rather than a container that needs to fit supplies .... Plus it fulfils the first scenario of filling the void between wheel and frame

My understanding is that placing a large storage box (when I say large, I mean tall but still quite narrow) above the BB that eliminates a significant portion of the frame 'triangle' by "filling it in" is aerodynamically problematic. So, that means:

Yes, IIRC, such a storage box typically tests well on a bike alone.

However, when a rider is added, the box harms the aerodynamics of the complete system.

A small (narrow and short) storage box above the BB is, when well-designed, generally aero neutral. But as soon as such a box gets fairly tall, then it typically adds drag to a rider+bike system.

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Advanced Aero TopTube Storage for Road, Gravel, & Tri...ZeroSlip & Direct-mount, made in the USA.
DarkSpeedWorks.com.....Reviews.....Insta.....Facebook
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That's interesting, I wonder how tall that has to be?

It seems like it would be quite easy to adapt a frame design like this...Link

But one even smaller/lower could satisfy the need

Did yiu consider making a prosthetic neoprene one?

While that is a cool-looking frame, I would guess that even that frame might have an aero penalty because of that large above-BB filler. Many elements of that frame appear to be designed more for aesthetics than aerodynamics.

The general problem is, to the best of my understanding, is that the more an aero bike frame's triangle is "filled-up", that the more the 'filler' starts interfering with the air flow around the moving rider's legs. And that is where the aero penalty lies.

And that is why, I think, specialized chose to put the big honkin' storage unit on the new shiv behind the seat tube vs inside the main triangle.

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Advanced Aero TopTube Storage for Road, Gravel, & Tri...ZeroSlip & Direct-mount, made in the USA.
DarkSpeedWorks.com.....Reviews.....Insta.....Facebook
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I agree the cube looks clunky. I wonder which tests yiu are referring too... I remember when that closed Trimble frame came out they tested badly

The specialised box is for fluids which can be perfect thin aero shape but an amateur would still need a storage solution for repairs right?

Sure, of course.

To best solve the problem, you gotta look at the whole system. Is the bike set up going to be for training or for racing? If it were me, I would use one set up for racing and another set up for training. How long is the target event? How much nutrition do you need to carry? What will be the total flat kit? Where and how much water is going to be stored? Is the space behind the saddle available? What size bento will be used? etc. When all those are answered, I think nearly every bike set up can be optimized fairly well within the constraints of the system.

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Advanced Aero TopTube Storage for Road, Gravel, & Tri...ZeroSlip & Direct-mount, made in the USA.
DarkSpeedWorks.com.....Reviews.....Insta.....Facebook
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The Scott plasma and p5 already look like they have space for one... Link

If yiu made this shape wider then it wouldn't need to be as high.

One advantage of a detachable is that yiu can unclip it, and turn it upside down to shake it empty... Which means you can make it a tighter fit. With a BBbox yiu could make an insert that you pull out... Instead of a door or a rubber seal design

Most things I’ve read about the fuel cell for the shiv (excluding the most recent model I guess) was that it was “aero neutral.” Do you know if those tests were conducted with or without a rider? Just curious since in your other post you talked about the effect on the entire rider/bike system if the space above the BB was filled.

The new shiv also has a compartment inside the frame for tool storage. I think this is where things will go, rather than any external location. You can see it on the dimond marquis, the andean, the shiv, and several specialized mountain bikes as well.

Thanks, those are great examples!



Dimond... This looks perfect size... No higher than chainring

Andean Plenty of space in that frame... Soft pouches to reduce rattle

Shiv
Larger with easy access silent seal, but might let water in

Shiv disc... Can't find that picture of the clear demo frame with m&m's

No, I do not know how specialized tested the new or the old shiv. I do know that few companies (there are some, but not many) test their bikes reliably with a rider. Typically, one can use a dummy or a real person. A dummy is expensive and it usually does not pedal (but, again, there are exceptions), so a new data problem is introduced. Testing with a real person is easy, but people tend to move so getting good repeatable data with a real person when one is teasing out very very smalll aero differences is also extremely difficult.

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Advanced Aero TopTube Storage for Road, Gravel, & Tri...ZeroSlip & Direct-mount, made in the USA.
DarkSpeedWorks.com.....Reviews.....Insta.....Facebook
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Dimond toolbox was designed in specific response to learned lessons from the wind tunnel.

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Dimond Bikes Superfan

Hello ericlambi and All,

This box may be a bit high above the BB as mentioned in Cervélo white paper but it is quite narrow matching tube size .... and very light weight.

https://forum.slowtwitch.com/...ost=6038977#p6038977

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Cheers, Neal

+1 mph Faster

That looks so clean!

If manufacturers started making that integral then maybe it could be made lower? Maybe there's a limiter due to internal cable routing? Or possibly structural strength? Like that is a key area for the carbon layup to be multidirectional?

I made something similar for my Kestrel Talon using a Specialized Fuel Cell! I just hacked off the front part with a saw to line up with the Elite Crono Bottle and used spacers to get the tilt of the cell to fit right with the lower triangle.

I'd like to see a frame that incorporates this style of BB storage with a standard water bottle cage (for on course replacements). I'm thinking of something similar to the sort of "widened/recessed" downtube as shown in this picture of a Pinarello Bolide TT.




This flared out design would smoothen the airflow around the bottle, then just underneath the bottle cage is the storage box that completes the airflow to the seattube. Then maybe have an option where if you don't want to use the bottle, you can bolt down a sort of cover that matches the shape of the widened downtube to the bottom bracket storage box. On paper it might not be AS fast as a traditional "blade" airfoil shape, but I'm thinking about a balance of aerodynamics and versatility for those who would rather use reusable/replaceable standard bottles instead of aero bottles.