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carolina
human power supergeek

USA
1031 Posts

Posted - 04/03/2019 :  10:08:10  Show Profile  Visit carolina's Homepage  Reply with Quote
I post for trike snd two wheeler builders. Very detailed.

https://pin.it/oteofnqfk4jadd
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velosRus.com

Toecutter
New Member

USA
57 Posts

Posted - 04/03/2019 :  12:39:37  Show Profile  Reply with Quote
The Facet V1's CdA leaves a bit to be desired. It's far better than the naked trike, but given that the builder could only reach about 50 km/h, it's nothing compared to a Quest or WAW.

Nonetheless, years ago I read the build instructions for ideas, and found the information to be quite useful, and used some of the techniques for my first coroplast body shell.

Lately, I have been fond of the idea of using coroplast to get a working and practical velo made, set up to have the body easily removable as 3-4 pieces without having to take the coroplast pieces themselves apart, and refining the shape to cut drag down as low as possible. Once the results are satisfactory, one would then use the coroplast pieces as templates and re-do the body out of corrugated cardboard, wrapping it in fiberglass/epoxy on each side to build a collision-resistant and extremely durable yet not-too-heavy structure.

Edited by - Toecutter on 04/03/2019 12:41:19
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carolina
human power supergeek

USA
1031 Posts

Posted - 04/03/2019 :  16:06:10  Show Profile  Visit carolina's Homepage  Reply with Quote
Use carbon, ain’t but around 10$ 12$ per yard more. Get couple yrds of innegra to add in. I use black pigment in resin before stirring in hardner for better looks inside. Compositeenvisions.com. Best prices on carbon, ask jake for seconds or close-outs. Plain weave and couple yards of uni. You could use polyester resin from Home Depot. I heard a guy made ultralight plane one time from cardboard and covered with fglass.

Great idea toecutter you have. You can contour some areas with 3/4” foam from your free aircraft spruce dot com catalogue. Tell em to cut in haf, save on shipping. 24x24”.


You like 3 pieces one like this one from uk. Kinda like waw too, 3 pieces. Pinterest has alot of ideas and google images.



Notice how wheel house up frt is bolted to support on trike frame.
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velosRus.com

Edited by - carolina on 04/03/2019 16:14:19
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carolina
human power supergeek

USA
1031 Posts

Posted - 04/03/2019 :  16:18:46  Show Profile  Visit carolina's Homepage  Reply with Quote
I like how OBrien made these aluminum mounts for the body. But that red one is outside the box thinking.


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velosRus.com

Edited by - carolina on 04/03/2019 16:19:50
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estoudz
Starting Member

USA
19 Posts

Posted - 04/03/2019 :  16:24:46  Show Profile  Reply with Quote
This guy built a trailer for his recumbent using cardboard composite construction. The bulkhead between my boom and my body on my electric recumbent used cardboard as a core material and wrapped with eight layers of carbon fiber to form a honeycomb plate.

https://microship.com/cardboard-core-composite-fabrication



eric stoudemire
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Toecutter
New Member

USA
57 Posts

Posted - 04/03/2019 :  18:05:24  Show Profile  Reply with Quote
quote:
Originally posted by carolina

Use carbon, ain’t but around 10$ 12$ per yard more. Get couple yrds of innegra to add in. I use black pigment in resin before stirring in hardner for better looks inside. Compositeenvisions.com. Best prices on carbon, ask jake for seconds or close-outs. Plain weave and couple yards of uni. You could use polyester resin from Home Depot. I heard a guy made ultralight plane one time from cardboard and covered with fglass.

Great idea toecutter you have. You can contour some areas with 3/4” foam from your free aircraft spruce dot com catalogue. Tell em to cut in haf, save on shipping. 24x24”.


You like 3 pieces one like this one from uk. Kinda like waw too, 3 pieces. Pinterest has alot of ideas and google images.

Notice how wheel house up frt is bolted to support on trike frame.
———-

velosRus.com



So the process for carbon fiber would be similar then? I want to avoid expensive tools or having to learn vacuum molding.

The body would have to be three or four pieces so that it could be fit to the trike without the pieces themselves having to be damaged in the process of removal.

I'm thinking along the lines of a nose-cone section, a main section that is comprised of most of the the floor/sides and the rear bulkhead, a tailbox section with included trunk space, and the hood/roof piece.

The main section would attach to the frame on both left and right frame cross members along with the rear of the frame plus the seatstay posts. You would basically lower the assembled trike onto the floor of the main section.

The nose piece would attach to the front of the frame just aft of the telescoping boom as well as the main section.

The tailbox would attach to the rear of the frame, the seatstay posts, and the main section, sliding underneath the rear wheel and onto the main section.

The hood/roof piece would have mounts/hinges to the main section and be removable.

This would allow collision protection without the body coming off and dismembering the rider in the event of a horrific wreck. The main section would have to be stronger than the other pieces and could even act as an integrated roll cage if designed correctly.

There would be separate pieces for odds and ends as well. In the case of an outboard-wheeled design like the 1930s/40s grand prix cars, I would have added wheel fairings attach to my suspension around the wheels. I could make front fairings for the mirrors to cut drag as well.

quote:


I like how OBrien made these aluminum mounts for the body. But that red one is outside the box thinking.



The red one has been called "The Red Zeppelin" around the internet(such as bentrideronline.com). Very little info pertaining to it remains. It also looks like a real hassel to get that sort of design to work correctly, given the difficulty of making perfectly straight cuts by hand.

Both the red and yellow one still suffered from a short usable life because of the coroplast itself doesn't maintain its rigidity for more than a year or two. My first coroplast body had that same problem.

You can see me riding my first coroplast prototype, built to fit a KMX with aftermarket front suspension, in the videos below:

https://vimeo.com/284616898

https://vimeo.com/284616919

About a month or so after that video, the body developed a dangerous wobble at 40+ mph. It was nearly a year old by that point. Whenever it would wobble at 40-50 mph, the entire trike would be pushed left and right due to the fluctuating vectors of drag force imposed. Eventually, I had to remove the shell, not just for that reason, but also because a crank became seized to the bottom bracket and stripped its threading when I tried to replace it and I needed a power saw to get the seized crank off.

I didn't plan on using that body long term anyway and it was mostly an experiment. Its drag left a lot to be desired. I could top out at 33-35 mph on the flat on any given day, cruising speed was more like 21 mph. I got it up to 51 mph downhill once. Coast down testing showed a CdA of 0.25 m^2. The fully assembled trike with shell was around 70 lbs. The bottom scraped over speed bumps because the ground clearance in the front was too low. Considering I could top out around 29 mph on the naked trike, and considering commercial velomobiles like the Quest or WAW have a CdA slightly under 0.1 m^2, this shape is not good enough as a final template to make a shell out of another material. It is a great test mule though to copy from with few changes other than the exterior shape because I got the ergonomics correct on the first try, which was the main goal. It was very comfortable to use and ingress/egress was easy and didn't require strange gymnastics, AND it could be carried through a doorway into a house or an apartment if desired. I could also work on ANYTHING it needed without having to remove the shell(the one exception being that if the crankset hadn't seized to the bottom bracket and required a non-bike-specific tool to remove.). I need to do another design iteration or two or three in coroplast until I've got the aerodynamics and clearances right though.

I'm more fond of Jerry's approach to coroplast than the approaches of the Spearhead or Led Zeppelin. It's far less complicated, faster build time, easier to modify, requires less planning, requires less material, and still has about the same usable life duration.

Coroplast is a great material for getting something working, but it will not be a permanent solution. However, once the body is built and the ergonomics and shape are correct for one's needs, one has a template with which to use a more durable material to make a functioning duplicate with!

quote:
Originally posted by estoudz

This guy built a trailer for his recumbent using cardboard composite construction.


That same website, when I came across it two years ago, is what gave me the idea! Coroplast and corrugated cardboard both have similar properties with regard to shaping them. You can make curves in one direction bending the grain lengthwise, but it doesn't do compound curves under normal circumstances. So any shape done up in one transfers to the other quite readily.

With a coroplast template, one can make the cardboard body off of all the individual coroplast pieces, to be wrapped in fiberglass or carbon fiber, and end up with a lightweight, tough, rigid, durable, and aesthetically pleasing structure. One must be careful not to get the cardboard wet before all of the work is finished though!

quote:
The bulkhead between my boom and my body on my electric recumbent used cardboard as a core material and wrapped with eight layers of carbon fiber to form a honeycomb plate.



Do you have any photos or a description of the process you used to form it? I'm curious.

If carbon fiber is now cheap enough and is a superior material for the application, I may as well use it instead.


Eventually, once all of this is figured out with a design iteration or two, the possibility exists afterwards to move onto designing a monocoque using the same technique and getting rid of the heavy steel frame.

Edited by - Toecutter on 04/03/2019 18:42:30
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estoudz
Starting Member

USA
19 Posts

Posted - 04/03/2019 :  19:01:22  Show Profile  Reply with Quote
Sorry, I do not have any photos of the layup but I used four layers of 1/8" cardboard interleaved with aluminum flashing to increase stiffness. I first waterproofed the cardboard by painting it with diluted epoxy. Once dry I wet sanded with epoxy the cardboard and the flashing to improve the bond between the flashing/cardboard interface. The outer surfaces were left cardboard to prevent galvanic corrosion from the carbon fiber. I wrapped the plate with carbon fiber then applied the epoxy then wrapped in plastic wrap and then clamped the plate between two boards. Once dry I sanded the plate and repeated the process.

eric stoudemire
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carolina
human power supergeek

USA
1031 Posts

Posted - 04/03/2019 :  20:37:39  Show Profile  Visit carolina's Homepage  Reply with Quote
Yes toecutter carbon an fglass lay up the same. I never do vaccum bagging. Your idea with cardboard & carbon is great, last forever, look good painted. You can cover the foam with carbon too as u know. You can create nice shapes. Put up pics.

velosRus.com
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carolina
human power supergeek

USA
1031 Posts

Posted - 04/03/2019 :  22:18:18  Show Profile  Visit carolina's Homepage  Reply with Quote
Is this same guy with red one, red again??????

https://pin.it/q7oyhfmdgr3pyd

____________

velosRus.com
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estoudz
Starting Member

USA
19 Posts

Posted - 04/04/2019 :  01:13:45  Show Profile  Reply with Quote
Once I finish my electric recumbent I will build a tail fairing using this process to house my range extender genset. I hope to go on some long distance tours.

eric stoudemire
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Joel DIckman
recumbent enthusiast

USA
157 Posts

Posted - 04/04/2019 :  10:17:37  Show Profile  Visit Joel DIckman's Homepage  Reply with Quote
quote:
Originally posted by Toecutter

The Facet V1's CdA leaves a bit to be desired. It's far better than the naked trike, but given that the builder could only reach about 50 km/h, it's nothing compared to a Quest or WAW...



I have been playing around with fairings on recumbent bikes (not trikes) for a long time. On the basis of my personal experience, I think that you are exaggerating the aerodynamic difference between a compound-curved fairing professionally made, and a home-brew coroplast fairing that has been designed and executed with care. Such as Lee Wakefield's fairings. Are the compound curved professional fairings superior aerodynamically? Yes, of course. Are they greatly superior? No.

Remember the advantages of the home-brew fairing:

1) It is cheaper. MUCH cheaper than a Quest or something comparable.
2) It is cheaper than building your own composite fairing, and much less time consuming. You do not have to breathe in the fumes from epoxy resin and hardener. The polyester stuff is much worse.
3) If you crash your home-brew fairing and damage it, no big deal. You can fix it yourself without too much hassle or expense. If you put in big miles, sooner or later you will crash. (Ask Jerry about this.)
4) For ordinary riders of ordinary athletic ability, it is fast enough.

If you are a hedge fund guy or someone else with deep pockets, by all means, buy a Quest. Money is no object. Suppose you are a gifted athlete shooting for a speed record. You need the very best equipment available. But for most people of limited financial means and ordinary athletic ability, the home-brew coroplast fairing is a better way to go.

The REAL benefit of the professionally made compound curved faired recumbent bike or trike is not superior aerodynamics. It is superior looks. Those shiny compound curved surfaces caress your eyeballs. Even the best home-brew coroplast fairing cannot compare.

To say that the carefully made homebrew fairing is "nothing" aerodynamically compared to a Quest is exaggerating the real aero difference.

Safe riding,
Joel Dickman
http://lightningriders.com

These three prevent most accidents: seeing, being seen, & (usually) common sense.

Edited by - Joel DIckman on 04/04/2019 10:31:14
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jjackstone
recumbent enthusiast

USA
266 Posts

Posted - 04/04/2019 :  10:58:54  Show Profile  Reply with Quote
Hey. I like my epoxy fumes.

JJ
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Toecutter
New Member

USA
57 Posts

Posted - 04/04/2019 :  16:54:20  Show Profile  Reply with Quote
quote:
I have been playing around with fairings on recumbent bikes (not trikes) for a long time. On the basis of my personal experience, I think that you are exaggerating the aerodynamic difference between a compound-curved fairing professionally made, and a home-brew coroplast fairing that has been designed and executed with care. Such as Lee Wakefield's fairings. Are the compound curved professional fairings superior aerodynamically? Yes, of course. Are they greatly superior? No.


My understanding is that for a given frontal area, drag coefficients of two similar fairings, one made of panels only curved in one direction with sharp vertices approximating a compound curved shape, and the actual curved shape being compared, the drag coefficient of the two should be within 20-25% of each other. Does that seem exaggerated to you?

Unlike a velomobile designed to be such from the ground up, building a shell over a trike not originally designed to have one imposes design constraints that a velomobile built as a monocoque from the ground up will not have. One of them often is a larger width, which will effect the frontal area of the velomobile design.

I ran into this problem with my KMX. Best case scenario, I could get frontal area down to around 0.55 m^2 keeping the KMX steering stock(it's direct steering), due to the clearance issues imposed by the steering bars. This requires the use of spandex boots that stretch outward as I steer, allowing the steering bars to move passed the outer dimensions of the shell with holes cut in the sides, and the spandex helping to keep the airflow as clean as possible. With a rack and pinion or a tiller steering setup, which would necessitate removing the mounting tubes for the steering bars from the steering knuckles, this could feasibly be cut to 0.45 m^2 with the width of the steering bars no longer dictating the minimum width of the possible body designs at their widest point(instead, my shoulders would dictate that), and I would be able to do away with the spandex. Both cases require outboard wheels(such as the LeMans or Velayo), which imposes a significant drag penalty including drag from the spinning wheels, drag from the brakes, drag from the suspension, as well as interference drag with the shell. I am currently designing wheel fairings that will attach to my front suspension that will cover the front wheels and brakes, which should help a bit with drag, while also keeping road spray from hitting me with no top installed or hitting the windshield with a top installed. If I wanted to have inboard wheels with the outer disc covers exposed to the airflow at the side of the body(WAW, Strada, or Alleweder A2), this increases best case frontal area to around 0.6 m^2, and if I wanted enclosed inboard wheels(Quest, Milan), to accommodate steering without wheel scrub, this increases it to around 0.75 m^2. Compare these best case possible frontal areas to the standard Quest which has an area of 0.46 m^2 or the Milan with an area 0.41 m^2, both with enclosed inboard wheels PLUS all the aero advantages these commercial velos have because of their enclosed inboard wheels for such comparatively small frontal areas. THEN consider the slight aero advantage gained by having compound curves on top of that.

It's kind of hard to compete with that, and it has much less to do with the properties of coroplast than it does the fact that one is designing a body to fit a trike as well as the rider, instead of just the rider. It's not that I'm exaggerating the differences based on material, but pointing out a major difference that exists in the possible CdA values between homebrew fairings on most trikes versus commercial velomobiles. This is because of the limitations in body design imposed by the geometry of the trikes used to build off of versus being able to construct an optimized monocoque from the ground up to fit the rider that isn't built around an existing platform.

quote:
Remember the advantages of the home-brew fairing:

1) It is cheaper. MUCH cheaper than a Quest or something comparable.
2) It is cheaper than building your own composite fairing, and much less time consuming. You do not have to breathe in the fumes from epoxy resin and hardener. The polyester stuff is much worse.
3) If you crash your home-brew fairing and damage it, no big deal. You can fix it yourself without too much hassle or expense. If you put in big miles, sooner or later you will crash. (Ask Jerry about this.)
4) For ordinary riders of ordinary athletic ability, it is fast enough.


I agree 100% with all of the above points. That's why my first successful build was a coroplast velomobile off of my KMX trike. I did start working on a fiberglass shell for a Thunderbolt trike before that, but it never saw completion as the plug was destroyed during an attempted home invasion and ensuing brawl. The coroplast shell took a LOT less time, was a lot less messy, and it worked, whereas with the fiberglass, being my first effort with the material, there was no guarantee it would have even worked.

quote:
If you are a hedge fund guy or someone else with deep pockets, by all means, buy a Quest. Money is no object. Suppose you are a gifted athlete shooting for a speed record. You need the very best equipment available. But for most people of limited financial means and ordinary athletic ability, the home-brew coroplast fairing is a better way to go.


I fit in the latter category most closely myself. I'm quite fast, but probably not at the level of a professional athlete. I don't have much in the way of money, otherwise I'd have a DF or a Milan right now.

quote:
The REAL benefit of the professionally made compound curved faired recumbent bike or trike is not superior aerodynamics. It is superior looks. Those shiny compound curved surfaces caress your eyeballs. Even the best home-brew coroplast fairing cannot compare.


And also collision protection. Personally, I could care less about looks. I seek a practical machine that is fast, comfortable, stable, and safe. Coroplast can do fast, comfortable, and stable on its own with the right design and right choice of trike, and with a sufficiently strong roll cage made out of another material, it can be safe as well.

My trike of choice wasn't chosen for efficiency/speed, but for sturdiness. I plan to put an overpowered electric drive system in it and haul ass. If I wasn't concerned with either that or ride comfort, and wanted to keep it entirely human power, a Greenspeed Aero would have been a much better choice and could have possibly allowed me to build something with a drag coefficient comparable to or even better than many of the commercial velomobiles while still using coroplast, but I would have given up suspension in the process. Another good choice would have been an Ice Trice FS, but that was beyond my budget, and the KMX plus the front suspension kit was relatively cheap to put together(a tiny bit over $2k for everything). For a human powered vehicle with no electric assist at all and looking at it from a standpoint of drag/efficiency, my choice of KMX trike platform was about the worst that could have been made from the tadpole trikes available, and I still don't have a motor in it yet, but I enjoy the hell out of it anyway and look forward to getting it as slippery as I can using coroplast.

As soon as I made my first coroplast wheel discs and noticed a major difference in both cruising speed and top speed, I was hooked.

quote:
To say that the carefully made homebrew fairing is "nothing" aerodynamically compared to a Quest is exaggerating the real aero difference.


The Facet V1 will not only have the 20-25% drag coefficient penalty versus a Quest due to its edges, but it looks as if its frontal area is about 30-50% higher than that of a Quest. Putting those two factors together would mean it has 50-90% more drag than a Quest, assuming the numbers are within the correct range. That makes quite a difference when it comes to both flat ground cruising speeds lazily pedaling along with 100W as well as top speeds during sprints.

Assuming the same mass(32 kg) and rolling resistance(Crr 0.006) and driveline efficiency(95%), that would also be a 2-3 mph difference in flat ground cruising speed at 100W, and a 5-7 mph difference in top speed with a 400W sprint(This is using 0.2 Cd and 0.46 m^2 area for the Quest). In a long commute in traffic or in a race, this extra drag makes a significant difference. This extra drag also requires more effort and time to accelerate up to cruising speed for a given amount of power. In a commute, this reduced speed/acceleration greatly increases the number of cars that are going to have to pass you during a ride by lengthening your commute time and increasing the difference between your speed and that of automobile traffic, as well as making sprints more difficult and sustainable for shorter distances. This also means slightly more red lights hit at the wrong time where you will have to stop instead of transferring that momentum you built up. This in turn will affect your rolling average even more than the difference in 100W flat ground cruising speed between the two.

That's almost as much of a difference between my admittedly crappy homebrew fairing and the naked trike without the fairing. The difference in usability with traffic was huge, even if it doesn't seem like much. I intend to correct its subpar aero and I'm trying to get the aerodynamics right with my next one now that I got the ergonomics and practical issues worked out(for the most part) on my first attempt. And the next one is being made out of coroplast, my current material of choice due to all the reasons that you listed.

Efficiency has a sort of cascading effect of impacts on rider effort and vehicle usability through a variety of factors. The faster the velomobile, generally the more usable it is on roads populated by automobiles, although it must be stable as well(among other practical constraints), which is why I chose a trike instead of a two-wheeler.

The air really doesn't care what material it's pushing up against, as long as the shape is correct for the application and rigid.

If the 20-25% difference in drag between the body with sharp edges versus the smooth body was all there was to worry about, the possible differences in cruising speed, top speed, and usability between the the Facet and a commercial velo like the Quest would be much more minor and closer to the differences between the various weight-weenie road bikes on the market, but frontal area is a real drag. Most commercial trikes are not conducive to getting an area comparable to the decent commercial velomobiles on the market.

Edited by - Toecutter on 04/05/2019 02:40:00
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warren
human power expert

USA
6424 Posts

Posted - 04/04/2019 :  17:28:01  Show Profile  Visit warren's Homepage  Reply with Quote
The toughest thing to make out of coroplast is the nose cone. Somebody needs to make a trike nose cone that starts out nice and round and then transitions to flat panels.
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Toecutter
New Member

USA
57 Posts

Posted - 04/04/2019 :  17:30:52  Show Profile  Reply with Quote
quote:
Originally posted by warren

The toughest thing to make out of coroplast is the nose cone. Somebody needs to make a trike nose cone that starts out nice and round and then transitions to flat panels.



Would it be feasible to make a template out of plywood sheets, the layers cut and bonded together, then the whole thing sanded to shape, only to then wrap coroplast around it while using a heat gun and melt it into shape? Maybe foam instead of wood?

Another idea could be to take a bunch of sheets of free election signs and cut a series of layers and make a nosecone shape from them, and then wrap it in mylar or some other material to covr the outer edges of the layers? Coroplast is made to resist bonding, so is there anything that could be made to bond to such a shape and neatly fit around it and fill in any imperfections?

I'd love to have a nosecone like Jerry's, without having to pay for one.

Edited by - Toecutter on 04/04/2019 17:37:02
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Terry
New Member

Canada
57 Posts

Posted - 04/04/2019 :  23:31:57  Show Profile  Reply with Quote
quote:
Originally posted by warren

The toughest thing to make out of coroplast is the nose cone. Somebody needs to make a trike nose cone that starts out nice and round and then transitions to flat panels.


How about using foam , shape it how you want , then fiberglass it.
Remove the foam and glue the the nose onto the panel body !
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Joel DIckman
recumbent enthusiast

USA
157 Posts

Posted - 04/05/2019 :  09:23:13  Show Profile  Visit Joel DIckman's Homepage  Reply with Quote
Hello toe-

1) I have only fooled around with bike fairings, not trikes. You clearly have lots of experience with trikes. How do the coro fairings - usually with a more faceted shape - compare numerically with compound curved fairings? I would not hazard a guess, being mostly innumerate. My seat-of-the-pants guesstimate is that IF the coro fairing is creatively made, it does not give that much up. There are tricks you can do - like using "darts" as a tailor does - to improve the shape and make it somewhat more rounded. More like a zeppelin, and less geometric.

2) The idea of incorporating some sort of roll bar structure in a velomobile strikes me as smart. My impression is that velomobiles have a rolling over problem that can lead to serious head injuries, since your head sticks up and out of the top. Even if you pay a weight penalty for a roll bar, it is likely still well worth doing. A bad head injury can ruin your whole day.

I am less optimistic about designing a velo to be safe in a crash with a motor vehicle. The disparity in kinetic energy between the motor vehicle and the human powered vehicle is just too great. If a car or truck hits you at speed, you are probably f*cked.

3) I am not certain, but the fiberglass nose cone Jerry recently adapted to his trike fairing reminds me of the Kingcycle recumbent bike nose cone used by Miles Kingsbury some twenty five years ago. I think Jerry imported these things from the UK.

Hey Warren - wasn't there some talk years ago about WISIL HPVers building and selling a compound curved fiberglass front fairing that could be combined with coroplast middle and tail fairings for a low cost F40-ish bike? I suppose there just wasn't enough interest to make the project economically feasible. Oh well... it was a good idea. Maybe it can be revived if and when the next wave of interest in HPVs happens.

Safe riding,
Joel Dickman
http://lightningriders.com

These three prevent most accidents: seeing, being seen, & (usually) common sense.
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warren
human power expert

USA
6424 Posts

Posted - 04/05/2019 :  14:09:07  Show Profile  Visit warren's Homepage  Reply with Quote
Yes, I remember seeing a cool CAD image with a composite nosecone in front and coro all the way back from there, but I can't remember who made it, and apparently I didn't snag a copy. Ollinger? Wianecki? Hill?
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Garrie L Hill
human power supergeek

USA
1785 Posts

Posted - 04/05/2019 :  20:40:02  Show Profile  Reply with Quote
Guilty. On my computer at work. Let me see what I can dig up.

Garrie "carbon based lifeform" Hill
HPRA Co-Dictator of the East
for pics of some of my time and money sucking projects
http://s58.photobucket.com/albums/g277/cfbb/
and videos
http://vimeo.com/5513519



Edited by - Garrie L Hill on 04/05/2019 20:40:30
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Toecutter
New Member

USA
57 Posts

Posted - 04/06/2019 :  01:37:48  Show Profile  Reply with Quote
quote:
Originally posted by Joel DIckman

Hello toe-

1) I have only fooled around with bike fairings, not trikes. You clearly have lots of experience with trikes. How do the coro fairings - usually with a more faceted shape - compare numerically with compound curved fairings? I would not hazard a guess, being mostly innumerate. My seat-of-the-pants guesstimate is that IF the coro fairing is creatively made, it does not give that much up. There are tricks you can do - like using "darts" as a tailor does - to improve the shape and make it somewhat more rounded. More like a zeppelin, and less geometric.


My experience with trikes isn't exactly "lots", but I have restored one trike and built up another from a kit where I went on to make my coroplast fairing. That is as far as my personal experience with trikes and even recumbents in general goes. I've never had a chance to ride a two-wheeled bent, and have never ridden in a commercially-produced velomobile. I used to work as an engineer though so I know a few things about design.

Making a bulbous shape is possible with coroplast using darts. The more darts used/higher the resolution of the shape, the lower the drag will be. The Spearhead coroplast velomobile seems to have had its drag quite high because the angles forming around its edges were too steep, and it very likely generates turbulence right at the tip of its nose that grows all along the front of the velomobile, where you'd ideally have laminar flow. Having more sides to the cross section and thereby reducing the angles between them would go a long way to killing turbulence generated in the front. The Spearhead has a 6-sided cross section.

That said, I'd hazard a guess that the Spearhead's aerodynamics are a fair bit better than my first design. Mine kind of sucked in this regard, which is why I want to improve upon it so badly. My first shell did get the practical details worked out quite well though, so it served its purpose in that regard. If it isn't practical or pleasurable to use, no matter how low it's drag, it will become a garage ornament. I use mine as a daily rider and it has to work, it has to be comfortable, and it has to be practical. I can transfer all of the traits that made mine practical and comfortable as well as remove its problems, and fit a more aerodynamic design around it now that I have had the experience of building it and riding it and now have an understanding of the needed parameters for the next design iteration.

If I were to make a similarly bulbous shape to the Spearhead, I'd try to make it a cross section of 17-sides, a flat bottom with the sides at 90 degrees to the floor and 12 degree angle between edges of the upper half of the cross section, which would probably require a CNC machine to cut the coroplast precisely so that it lines up(the Spearhead did exactly this in fact, except with less pieces). The upper portion of the cross section would approximate 180 degrees worth of a solid of revolution of whatever airfoil was used to plan the floorpan. The very front would be cut off so a rounded nosecone could be attached. I bet such a thing would also be lovely in crosswinds and it would probably be within a few percentage points of the drag of a compound curve. Depending upon the geometry of the trike frame this idea could be taken a step further to provide a slight frontal area reduction by going to a 19-sided cross section, with 45 degree angles between the floor and added bevels at the bottom of the sides, and 45 degree angles between the sides and the bottom bevels, but otherwise keeping 12 degrees between each edge on the upper portion of the cross section. In fact, such a shape would translate almost perfectly to a carbon fiber or fiberglass design with compound curves later on by merely removing all the edges and rounding the bevels at the bottom.

quote:
I am less optimistic about designing a velo to be safe in a crash with a motor vehicle. The disparity in kinetic energy between the motor vehicle and the human powered vehicle is just too great. If a car or truck hits you at speed, you are probably f*cked.


You'd be surprised how much of the impact a body will absorb to reduce the impulse suffered by the rider. Take a look at the following horrific crashes of automobiles with velomobiles where the velomobile riders actually survived:

Milan sideswiped by Ford Fusion at 35 mph:

http://www.bentrideronline.com/messageboard/showpost.php?p=1564017&postcount=21

Alleweder A2 T-boned by a car:

http://www.velomobiles.co.uk/2012/09/velomobile-crash-safety/

Quest hit by truck at highway speeds:

https://www.bentrideronline.com/messageboard/showthread.php?t=113466

Quest hit by driver at intersection:

http://www.bentrideronline.com/messageboard/showpost.php?p=1395402&postcount=28

Without these body shells covering the riders, it is doubtful they'd have survived the collisions.

One is much better off if the shell can protect the rider, than if it isn't there at all. For all practical purposes, a coroplast shell would be worthless in such a wreck because it would behave like a liquid and fold effortlessly under significant stress, but not aluminum, carbon, or fiberglass as the above articles have demonstrated.

However, with a steel or chrome-moly roll cage, coroplast may not be all that bad... The Pedal Prix racers in Australia use it with great success and minimal injuries, albeit they are hitting walls and each other, and not being hit by automobiles weighing 10-20x as much moving at 2-3x their rate of speed.

This all said, coroplast can still provide decent rollover protection even without a roll cage if the shell is designed for it, as well as absorb the road abrasions if it tips on its side, versus the rider being subjected to the road in an unfaired trike. In spite of its structural weaknesses under high and abrupt side loads and terrible puncture resistance, coroplast is some very tough stuff otherwise.

Edited by - Toecutter on 04/06/2019 02:57:43
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jjackstone
recumbent enthusiast

USA
266 Posts

Posted - 04/06/2019 :  09:12:37  Show Profile  Reply with Quote
http://www.recumbents.com/forums/topic.asp?TOPIC_ID=2341&SearchTerms=coroplast,template

Gary Hill's artwork.

JJ
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carolina
human power supergeek

USA
1031 Posts

Posted - 04/06/2019 :  14:39:13  Show Profile  Visit carolina's Homepage  Reply with Quote
TC:

Putting wings on rear chain wheel house. Set in place and cover w/carbon then bond whole unit in/custom fitted to rear floor. Your covering cardboard and this white foam from Walmart (5piece pack) weighs nothing. Might be great for certain areas in your new machine. This is a one off piece for this velo.

Sit 2 pieces in few dabs of bondo, then put cap strip across the bow of top. Add more scrap diviny-cell foam to back and front and sand to shape/cover w/twill carbon.




In the hobby crafting area at Walmart
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velosRus.com

Edited by - carolina on 04/06/2019 16:05:49
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estoudz
Starting Member

USA
19 Posts

Posted - 04/07/2019 :  00:12:35  Show Profile  Reply with Quote
Maybe this will help in building a monocoque body from honeycomb panels.

http://www.autospeed.com/cms/A_110989/article.html

eric stoudemire
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Toecutter
New Member

USA
57 Posts

Posted - 04/07/2019 :  14:26:39  Show Profile  Reply with Quote
quote:
Originally posted by carolina
Your covering cardboard and this white foam from Walmart (5piece pack) weighs nothing. Might be great for certain areas in your new machine. This is a one off piece for this velo.

Sit 2 pieces in few dabs of bondo, then put cap strip across the bow of top. Add more scrap diviny-cell foam to back and front and sand to shape/cover w/twill carbon.


Is it possible to bond carbon fiber to coroplast as well? I know coroplast is made to resist bonding to other materials, but using light/thin 2mm coroplast sandwiched between carbon fiber layers, if it could be made to bond, would be incredibly strong, and the 2mm coroplast sheet would be more forgiving with regard to the shapes that can be made with it.

My new machine is not ready yet. I have some pieces made, and for others, I've gone back to making drawings. The current drawing I'm working on looks something like an Aptera without compound curves. I really want the drag to be low for this one. The floorpan looking at it from the top down view is a NACA0023 with a 620mm width and 2696mm length. The side profile of the body uses a NACA2820 with a 2.113 degree camber at 87% of the length with a shell width from top to bottom of 620mm, with this shape cut off at 87%, the end of it being where the NACA0023 tapers to a fine point. It will also have outboard wheels, but with wheel covers.

Reconciling these two shapes into a 6-sided cross section is the plan.

I still have to design the turtledeck and hood pieces.

This design would allow me to use the stock KMX steering, and I'd end up with a frontal area around 0.55 m^2.

I'm thinking if pulled off right, this could have similar to or better CdA than velomobiles like the Strada, Quest, or WAW, without any compound curves.

The design iteration after that would entail figuring out compound curves and switching to cut drag further, and possibly going to a rack and pinion steering to shrink frontal area to around 0.45 m^2.

quote:
Originally posted by estoudz

Maybe this will help in building a monocoque body from honeycomb panels.

http://www.autospeed.com/cms/A_110989/article.html



I've come across that link years ago. I don't yet have the money to justify this degree of experimentation. That material is not cheap and I will probably make errors along the way. That said, it has enormous potential with regard to the type of vehicle I want to build. I estimate I could make a strong monocoque trike base out of it that weighs in under 15 lbs, use about 15 lbs of chrome-moly or steel pieces for the front/rear wheel mounts and roll bar, add moped wheels/solar car tires/suspension/brakes/steering/bicycle parts/ect, and I'd have a rolling chassis that only needs body and motor weighing under 50 lbs that's already strong enough to handle 100+ mph speeds.

With a well designed base and a roll cage, choice of body material won't matter much as everything would already be strong enough for collisions and daily use on rough roads. So a 15 lb coroplast frame and a 30 lb electric drive system could have me rolling around in this thing at under 100 lbs, and batteries/controllers/motors today are such that I could feasibly have 1-1.5 kWh of battery on board and 10 peak horsepower from the electric motor at the same time.

With the right body design(with drag comparable to a Milan), such a thing could do 60 mph on 1 horsepower needing around 10 wh/mi if the rider pedals with 150W, top out at over 120 mph(you'd want a Schlumpf high speed drive to allow human power to be added at all possible speed ranges), and do 0-60 mph acceleration in around 8 seconds. With the motor off, the rider would be able to pedal such a thing like a velomobile and be much faster than a normal bicycle, even with the electric drivetrain being lugged around plus overcoming the cogging losses of the hubmotor.

Just an idea at this point, but I think such a vehicle can be done. It would be about the most efficient highway capable vehicle possible, and as technology improves, the possible range and performance will only get better. Imagine having 30-50 horsepower in such a thing...
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estoudz
Starting Member

USA
19 Posts

Posted - 04/07/2019 :  15:03:39  Show Profile  Reply with Quote
You can flame treat coroplast to improve bonding but I do not know if the bond would be strong enough for laminating. Basic cardboard when impregnated with epoxy is strengthened considerably as well as waterproof and has a strong bond to carbon fiber. I prefer electric middle drives with the weight being removed from the wheel and the motor is isolated by the wheel's freehub.

eric stoudemire
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estoudz
Starting Member

USA
19 Posts

Posted - 05/04/2019 :  19:50:03  Show Profile  Reply with Quote
I found a video on you tube of a guy laminating coroplast with carbon fiber to build a rear splitter for his race car. He did not talk about surface treating the coroplast though.

https://www.youtube.com/watch?v=6QCpnvhKkl8

eric stoudemire
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