Retro Grouch 

"How much do aerodynamics truly benefit the average bent rider?"

How do you define "benefit"?

If there is some kind of prize for finishing a ride a few minutes sooner, I guess that would be easy to define. If you're talking about satisfaction from being able to ride a little bit faster, I'd think that would vary from individual to individual.

Personally, within a range I don't care how fast I ride and my range includes a speed at which aerodynamics don't help very much. In my case I'd have to respond "little to none."

rydabent

retro +1

I like your reply. I feel the same. I ride at the speed that feels right at the moment, sometimes fast and sometimes slow.

Tractortom

I recently added a fairing to my long wheelbase Bacchetta Belladare recumbent for a couple of reasons. Down here in south Florida, in the summer, it rains about every afternoon, and I wanted a little bit of protection. But I was also curious about the improved aerodynamics of bike with the fairing. I have read that you will see a 1-2mph increase over 15mph with the fairing, and I find that to be a true statement. In my daily commute of right around 15.5 miles, my speed has increased over 1mph with the fairing in place. Now, the question is, was it worth the $400 it cost to add the fairing to the bike? For me, it probably was, as I never rode an unfaired motorcycle in the last 30 years that I rode, going way back to a BMW R80RT, which was one of the very first fully faired factory motorcycles. On a 50 mile ride yesterday with two friends, who ride a great deal more miles than I do, I found that I could keep up without trouble, until we got up around 20+ mph, and then I just hung back and let the big dogs run, they get tired after a while and slow down.... We completed our 50 mile ride Saturday in just a little over 3 hours, with an average speed of 15+ mph, which is pretty good for an old fat guy, like me, and with the wind behind us on the way back to the house we were averaging 18.5+ for the last 8 miles or so.

Just my $.02....

Tractor Tom in Okeechobee, FL

ystava

This is purely anecdotal. I am not much of a cyclist and certainly not fast. I showed up to a bike club ride when I moved to a new city with a borrowed SWB Vision; for all intents and purposes this was my first ride on the bike. The ride was just supposed to be 20 miles at 12-16 mph. Because of who showed up it wound up being 33 mi at an average 18 mph; I had no trouble keeping up, and I was barely sore.

The others' complaint was that they couldn't draft on me.

rydabent

john c +1

Your point is well taken because what you state is in the real world, not just opinion. It is indeed the air speed when riding that has to be taken into account. For instance yesterday on my ride, the wind was out of the south at 30mph with gust to over 40mph. I could only manage about 10 to 12mph ground speed, but at times the wind speed was probably over 50mph. I needed all the aero advantage that my bent has.

delcrossv

Well, I go a lot faster on this:




than I do on this:



and my 14 y.o. went over 55 mph on the flats in this:



so I'd say yes, it makes a big difference.

rydabent

Mechanical efficienties pale in the face of aero drag that goes up with the square of the the speed. Its actually pretty simple the less frontal area the less drag. Look at some of the pictures of a cyclist on a high racer bent riding next to a person on a DF. You can see that there is a huge difference in the fontal area of the two.

BlazingPedals

Despite the fact that some bents, especially the streamliners, can be extremely fast, the average bent rider averages more like 10-14 mph on a bent that is aerodynamically very little if any better than a hybrid upright. So bent aerodynamics don't mean a thing for most riders.

delcrossv

Really? Even the kids go faster on their Sunsets than that. I guess if you include trikes, maybe. But are most 'bent riders really that slow? I've ridden 'bents primarily for their speed potential.

yakmurph

Sample size and sample demographics will both influence any statistical data.
Apparently, Mr. B. Pedals and I both run into the same sort of recumbent riders, out in the wild.

The only relevant story I can share, is the comment a young D.F. rider made about me on my recumbent.
I was coasting downhill, wearing my usual flappy and loose Summer clothes.
The D.F. rider was my size and was wearing the same sort of high-drag clothing as I was.
He commented that he had to pedal to keep up with my downhill coasting... and that he was impressed.

Bottom line?
Of course aerodynamics makes a difference,
even for the, "average recumbent rider" -whatever that means!

-Steve

rydabent

Blazing---------yes while it is true that a lot of bent riders ride somewhere aroung 14mph or so, as mentioned dont forget the wind. Here lately I have been riding into a 30mph wind with gusts much higher.

I have noticed that DF riders that quite often crank up and show the old codger how much faster DF bikes are are not passing me as much, and if they do it is at a much slower rate.

RChung

That's true if the Cd part of CdA is the same but often it's not. It appears that for many recumbents the frontal area A is lower but since we (sometimes) know the total drag area CdA and it's not so low then the Cd must not be the same.

There are many different styles of recumbent bicycles and the CdA profiles of recumbents and DFs overlap over a wide range. I've measured DF's with CdA's ranging from just under .20 m^2 (for riders on TT bikes) up to around .65 m^2 (for a rider on a MTB -- I've never measured anyone on a "Dutch commuter" or a folding Brompton but I suspect the aero drag would be even higher). For normal-sized guys on a road bike without any other aero accoutrements I've measured CdA from about .28 m^2 up to just under .5 m^2. My data for recumbent riders is rather more limited but I got some data from a normal-sized guy riding a Bacchetta stick bike whose CdA was just above .3 m^2 (but I didn't get full information on what he was wearing so I don't know if that was high or low for that platform). OTOH, a guy on a Fujin low racer calculated his CdA at just under .18 m^2. I helped a guy calculate his CdA on a Metaphysic and he came in at right around .25 m^2 with tight clothing and no bags or other add-ons. I would expect that the stick bike and the Metaphysic are "relatively aero but not super aero examples" of unfaired recumbent bikes while the Fujin is on the lower-end. I was hoping to test a P-38 or a Morciglio at some point but that now seems unlikely. All of this ignores rolling resistance differences between tires of different sizes and types, and none of these bikes are faired. Fairings are a completely different ball park.

cplager

A good example of this are tail-boxes. They don't change the area (at least, they certainly aren't making it smaller), but do have a lower CdA.

RChung

Exactly. I've used tailboxes, disc wheels, helmets, and (for TT riders) arm position as examples of things that don't affect A but do affect CdA. You know those behind-the-seat water bottle cages used by triathletes? That's an interesting example because you can actually reduce A but the CdA can (in certain cases) increase.

Steamer

If you're referring to the Bacchetta guy that I am thinking of (Tim. T.), I am pretty sure he is closer to .20 m^2 (not .30).

Another data point: Ian H. (who is a fairly small guy) on his Velokraft VK2 lowracer with a tailbox was around .21-.22 m^2 IIRC. I have info on what kind of wheels he had too in my notes and I also have his test run files 'iffin yer interested.

RChung

That's interesting, but nope, I wasn't referrin' to Tim. But I'll add that to the mix.

I'm surprised the VK2 with tailbox has that much drag.

The two bottom lines from all of this are
1) the eyeball is a poor wind tunnel so if you really want to know you'll have to measure; and
2) there's a lot of range in aero drag even for the same platform -- more than many recumbent riders realize.

Steamer

Email Tim for his numbers. He's done a fair number of tests and he has pretty good agreement between them, so his numbers are reliable I think.

As for the bolded part above - yeah, this has been one of the bigger surprises for me so far. Details matter. Accessories and clothing matter. People can't hang all kinds of extra bags and lights and crap all over their bike and wear flappy clothes and big honking visors on their helmets and not expect those things to add drag. For those who don't give a damn about drag, they can keep on cluttering up the bike, but for those of us interested in speed and efficiency, the lesson is to not ignore the aero effect all of these little decisions have.

RChung

I cringed when I saw these photos.
https://www.bikeforums.net/showthread...-vs-saddle-bag

Steamer

Heh, yeah, there are some seriously cluttered rando bike setups out there. Mystifies me.

I carry extrodinary amounts of crap with me in my seat bag (60oz bladder, extensive toolkit, spare cables, three tubes, pump, large crash pack/first aid kit, spare front and rear lights and batteries, maps, and misc clothes and food), but its all packed away in a rear bag that doesn't have much aero penalty ( I don't think....). I try to keep the extra clutter off the bike itself to stay reasonably sleek. No need to make rando harder.

(by the way, I cut down on the list of crap for most routine rides. But for adventure rides, especially those in remote areas on gravel roads, I bring the whole damn kit.....)

rydabent

Steamer

Im pretty much with you on carrying what I think I need to get myself home. I have alway ridden with a trunk pack, it has my mini bike shop in it. The people that I dont understand are the ones that ride with exactly nothing. They are the ones that I have stopped countless times to fix flats and other simple mechanical problems. But they maybe they are the smart ones knowing that someone like us will come along and get them going again.

RChung

Hmmm. That should be in the thread "How much does carrying all that stuff truly benefit the average bent rider?"

delcrossv

Sooooo true. I'm not a Mies fan, but "Less is More" really applies here.

MikeWMass

Probably not much. BUT: it only takes one long walk when you are out of cellphone range to learn that you are suddenly no longer the average rider, and that carrying what you need to get going might not be a bad idea after all! (Within reason, a mangled rear wheel would still stop even the best-equipped rider I have ever seen.)

RChung

Yeah, it depends on the situation, much like the benefit of aero.

BTW, once (long ago, before cell phones) a buddy went off the road and mangled his front wheel. We stuck it into the crotch of a tree and banged on it with a hunk of wood to semi-straighten it, then rough trued it, then opened the brakes enough to ride to the next town with a bike shop. Not exactly Eugene Christophe fixing his own fork but we were pretty pleased with ourselves.

Steamer

Cool. Some of my best cycling memories have to do with overcoming some unexpected adversity with (reasonable) grace.

My current crash pack weighs 2 lbs on its own. My previous one weighed one-tenth as much. I upped the ante after crashing on a gravel road a few months ago and found my old one to be seriously lacking. When I went down, I was 18 miles from the nearest town, and 70 miles from the end of the ride. We cut it short and turned that 70 into 40, though. Bandaids don't stay stuck very long when you are sweating, and in a light rainfall.