Custom Motorcycle Fairing

General Composites Discussions Composites Talk
#1

The project:

I am making a custom fairing for my motorcycle.

The problems:

I have to make a mirror image of an oil reservoir found on the left side to be on the right side. I don’t want to make the fairing any wider. I need to keep it relatively cool, so I don’t want to cover it up. The stock fairing had vents near it, but that means even wider fairings, and I’m trying to keep the bike looking slim up front. My idea was to keep it completely exposed, surrounded around the edges with a new fairing. On the right side, I wanted to make a replica, mirror image, of the oil reservoir, and use it as the air intake for the engine. The problem here is that I’ve never made accurate mirror images of anything, so I have no idea how to transfer the same lines that are found on the left, to be on the right other than eyeballing it, and I want it to look good.

The other issue is the material. I don’t plan on dropping my bike any time soon, but if I do, I just want the new intake and fairing to flex just enough so that it can absorb some small impacts. I have tons of fiberglass from my childhood RC airplane exploits. I’ve heard that fiberglass/epoxy ends up being heavier than the stock material, (some sort of plastic) and epoxy would be quick to crack because it’s really brittle. I’m open to other materials (different resin, and/or some kind of plastic without fiber altogether) to make the fairings, because anything that cuts weight is a great bonus, but the main constraint on material is the price. I’m between jobs right now, and I’m using the motorcycle project as a stress relief outlet from all the interviews and stuff.

Any tips and techniques would be greatly appreciated.

PS anyone know where I could find an apprenticeship/job as a fabricator?

#2

To make a mirror image of a part… I’m interested to hear any ideas on that!
No easy way that I can think of, you’d have to create a new plug from scratch. Or depending on the shape you might want to replicate the part and modify it, to base the new plug on that.

What do you mean about fibreglass/epoxy being heavier than stock material? Heavier than the stock plastic fairings? I wouldn’t say that’s completely true… a lot will depend on how the composite part is produced. If you ask a boat builder to do the job, then yeah I wouldn’t count on any weight savings. Haha :stuck_out_tongue:
If you can be accurate and not over-use resin, then most likely your composite part would be much thinner than the stock plastic part.

Honestly if budget is a concern, I don’t see any problems with using woven glass and epoxy (with some kind of other material like Innegra if you’re so inclined)?

#3

Hey, thanks for the reply! Off the top of my head, the best solution I could come up with for creating a mirror image was to create a female mold of the left side, then slice it up into pieces and flip each slice horizontally. Although that gives me a good general shape (which may be enough) I would need to think about how to correctly sand the ridges of the inverted slices to have the correct depth and angles. I guess I haven’t given the details too much thought, I figured I’d listen to this community’s ideas first.

Re: weight, I figure my fairing will be lighter even if I fail to be completely optimal with my fiberglass/resin work simply because my fairing will be roughly 1/6 the surface area, if not even less, so this is one of the smallest concerns to be honest.

The main issue is epoxy as a resin, I don’t want the fairing to crack with a (relatively) small drop. The only two ways I can think of fixing that is making it thicker, or using a more flexible resin. A local store sells some sort of polyester resins which are supposedly more UV-tolerant than epoxy, but I don’t know if they are more flexible, or if there are any other alternatives. I think the sales rep said polyester is a little heavier than epoxy, but it doesn’t go yellow like epoxy does from aging.

#4

Ahhh… about the cracking concerns, I would just ask your supplier. They should be able to steer you in exactly the right direction. My preference is for a good epoxy resin and 2k clear coat (for UV protection) which should solve any yellowing problems, but there are other options. For example I believe that UV resistant polyester resin is probably one used a lot for surfboards, which you might prefer if you don’t want to have to paint the parts. (I think all resin will still yellow over time, but at least if you use 2k paint or a UV resistant resin, you’ve done all you can and it will not go as fast.)

I think generally good quality epoxy will be much more durable than a polyester resin. For example Thorsten Durbahn (he makes monocoque subframes & lightweight track/race parts) uses a plain black epoxy surface coat on his lightweight bodywork. He actually recommends this not be painted if you want maximum weight savings for a track bike. The epoxy surface is very durable and you don’t have to be as careful as you would with any painted fairing which would mark and scratch very easily.

Lots of options, it just depends on your personal preference and what kind of performance you want from the final part. Personally I am going to use a slightly less expensive epoxy resin for my bodywork, only because it was actually more flexible than the more expensive option. The shop had sample laminates using both resins and the difference in flexibility was impressive.

And just a note on flexibility, if that is your goal (resistance to cracking) then I don’t think a thicker laminate is the way you want to go. Thicker would mean a more stiff part… but stiff & flexible are at opposite ends of the scale…

Also were you planning to use any kind of aramid/polyester reinforcement in your parts?

Anyway what kind of bike are you working on? Sounds like you’re going from a full fairing to a bikini fairing or something like that?

#5

Thanks for the tips!

I agree, stiffness and flexibility are opposites, but it all comes down to how the energy is dissipated. A stiff part can slide and bounce to dissipate energy (and crack), a flexible part can deform to absorb it. I would prefer deformation, it’s usually the lightweight solution, but I’m keeping my options open.

I’m not sure what you mean about aramid/polyester reinforcement, could you tell me a little more please?

I’m working on a BMW f650gs. It’s got plenty of weight to lose, but I wouldn’t give up BMW reliability for a maintenance hungry KTM. Besides, I love the BMW community.

#6

Ahhh… f650… are you replacing all the body panels or just some?
KTM issues… I hope not! I’m working on a 380 EXC supermoto (2 stroke). Should be much more simple to maintain than a 4 stroke though.

Since it’s a dualsport and you may be doing a bit of offroad riding (and maybe more likely to have small drops) I think the aramid/reinforcement is even more important. What I mean by aramid/polyester is a product like Kevlar or Innegra. This is laminated in your parts and basically stops the parts from splintering and breaking into pieces. The parts can still crack and take that kind of damage, but you’re virtually guaranteed that it will remain in one piece. Which is a good thing on a bike, because carbon or fibreglass will splinter into very sharp pieces - not a good situation if you happen to get stabbed by those kinds of broken pieces while sliding along next to the bike!

Innegra is by far the less costly option, and many times easier to work with than Kevlar. Innegra does the job just as well though. My local supplier had a piece of laminate using Innegra and they kept it out the back for something to take out their anger on. Haha. They demonstrated smashing it over the edge of a bin and they were trying as hard as they could and it doesn’t break apart at all. It’s fairly impressive.

#7

Hey, Yeah from what I’ve read, KTM does more of a ‘high performance’ build than BMW, so you can expect much better performance at the cost of lower life expectancy and higher maintenance (maybe not cost, but higher frequency of services).

The reinforcement you speak of sounds like something I would want to do. Do you happen to have any good links for ‘tutorials’ or examples of reinforcing a fiberglass fairing with innegra? I don’t know Kevlar or Innegra properties that well, so I don’t know where it would be best to apply them.

#8

As for a mirror image plug. Have you looked at the use of Autodesk 123D Make softwarre to make a base of the plug and then shape it for your needs. The stacked sections look like the way to go. Change the material thickness and size to sheet foam and it will draw the sections for you.

http://www.123dapp.com/make

If you need to draw or design the part use the 123D Design Software first.

http://www.123dapp.com/design

#9

For using Innegra you just need to make sure that it’s in between your laminate (don’t put it on the surface). I’m using it over the entire area of my panels, the one I am using is 68g and there’s not that many panels on a supermoto so I’m not worried about a slight weight increase. I know that some people only reinforce the mounting points or likely impact points, corners etc. but for peace of mind I would prefer to reinforce everything. Just one layer is all that’s needed.

I haven’t seen any tutorials, all I’ve done is a couple of small text pieces. It’s a bit harder to cut with a Dremel compared to a laminate that doesn’t use it, but you can have it to the edge of your part and it won’t give a fluffy edge like kevlar.

If you’re interested in learning about it I would recommend just making some test pieces, with & without Innegra for comparison. Then do some destruction testing, see it for yourself - that’s the best way to learn!