I get asked a lot where I get the plastic parts I use in my multicopters; so here is a little snapshot of some of my builds using these parts.
The problem with fabricating anything from plastic is that when you bend it, it fatigues as well as springs back to a certain degree.
A cheap way to make very lightweight, strong, and customized plastic parts for multirotors is to use a plastic crate which has pre-formed angles all over it, you just need to visualize the parts that can be cut out of it. I got one from Staples that had various angles and dimensions that would work well for my applications.
I cut legs for my multicopters because the standard plywood legs are wide and don't fit truly snug against the arm (these have a narrow profile instead, have a 90 degree angle built in and do not wobble when taking off or landing). Also, in a crash, or way too hard of a landing, they break at the perfect place thereby leaving the zip tied head intact (one issue with a simple plywood leg is that when it rips the zip ties off, it displaces adjacent wires, etc. as well)
I even put one under the frame by cutting the vertical leg off and mounting it flat to the bottom so that if I land to hard (or crash) it will hit first and keep the battery safe (as you can see from the dirt on it, it definitely has helped on hard landings). This extra leg also allows the Tricopter to sit when folded.
You can create really any kind of item needed quickly. Here is a protector I made for the Naza using the pre-molded 90 degree angles, it is super strong.
I use the plastic crate parts for protecting all of my flight control boards. Sometimes a template makes it easier to evaluate what part of the crate will work best.
Notice on the Tricopter, the pieces work great in order to still let you reach the KK2 board buttons, as well as on the mini quad.
Also on the quad you can see several other parts used for LED placement as well as for propeller protection.
The prop guard (or body) is simlpy 2 sheets of Elmers posterboard laminated together with spray adhesive. It's held on with rubber bands so it can be removed if i need to put 8" slowfly props on to carry heavier things (GoPro, water balloons, etc.). The typical props I use with the guard on are HD 7x3.5 which make this quad crazy fast (these are 20 gram 2000kv motors).
I've learned when using a body to protect the props, that you have to put the front green lights above the body so that when your pitching forward the light is seen from above, similar on the rear LEDs, that they be under the body so that when flying away from yourself (pitching forward) they can be seen and not covered up by the angle of the body.
I've snapped multicopter booms before (even on a 650mm) and used two small plastics angles and a couple of zip ties to splint it back together again, and allowed me to fly the rest of the day without having to go home and do an hour long boom replacement (which i eventually did the next day for the long term of course)
Zip ties are your best friend. Always keep a bag of various sized zip ties, a pair of needle nose pliers and a pair of cutters in your flying bag that goes with you when you fly.
Other uses for these plastic items include my FPV pod. My fpv pod looks overly complicated, but the reason i have every component on different brackets is so they can be swapped out with different components easily without affecting the overall structure of the pod. For example, I can swap out the CCD camera for the GoPro, or swap out a different transmitter for a more powerful one by just cutting the two zip ties that hold it's bracket to the pod, or even just snip the zip ties that hold it to the bracket and leave the bracket to mount the new one. Or swapping out antennas, same idea, i even have a pan/tilt bracket that uses the same holes that the camera bracket currently uses that can be swapped with just 2 zip ties. Notice the larger , removable, zip tie (along with velcro ) that holds the pod securely to the camera/battery tray. This also allows me to instantly remove the FPV pod and stick it on another copter/plane in seconds.
Zip ties really are your best friend! If you hadn't noticed, I zip tie everything in place, or at least so no items are dangling or wobbling at all. I've learned my lessons over the years that when something goes wrong, it usually snowballs because other items get torn off. case in point, I had a tricopter arm slightly fold back a few inches, while in flight, which by itself was fine and the copter was able to be flown back, until it folded a little bit more and pulled on one of the esc wires (which had excess that was hanging loose and flopping around) going to the board, which cut communication to the motor. you know what happened from there...
Nylon screws and nuts are great as well because they are much much lighter than metal and still very strong. They do not vibrate loose like metal. And heaven forbid you have a very bad crash, they may separate and take some of that energy, although i have had many crashes and have yet to break or strip one.
Also they are cheap at your local hardware store (i get mine at Busy Beaver) and the variety is huge, as well as the variety of standoffs, gaskets, tubes, wing nuts, washers, etc.
Here is my Naza H-quad (based on ycopter's YQ2 design, http://www.flitetest.com/articles/diy-quad-yq2) with various plastic parts used in many places; FC protector, legs, LED unit bracket, CCD camera bracket, receiver/antenna bracket, etc.
Other building tips to note;
When building DIY wood frames, the most important joint is the intersection of the booms at the center. Make sure you do a full lap joint and epoxy the joint fully ( i always mechanically fasten it as well), this will assure that the booms won't twist, causing you to lose yaw authority)
Bomb drop anyone...
Another couple issues I have in my RC life are; one, models getting damaged and destroyed during transport as well as being stored in the garage , and two, having minimal time to fly (usually only 15-25 minutes at a time, on the way to/from work/lunchtime) means setup and breakdown time must be minimized. My solution to all this is custom carriers that protect while storing all necessary items for quick setup.
I use computer boxes, zip ties, hot glue, pool noodles, and practical imagination!
Notice the props, prop savers, and install tool are instantly accessible and stored. I can pull into a parking lot/park/field and be flying in less than 2 minutes...
For the Large Quad/Tricopter box; I have different pool noodles setup to accept different multirotors and equipment. I simply choose what i will be flying that day, and swap -out equipment in the box. Now i only have one box to quickly put in the car in the morning and take out when i get home (believe me, when you have four kids under 8 yrs old, every extra minute you can save counts!)
The EPP planes take the most beating from the kids (but my 7 year old loves to fly them!)
Shout out to Robert Viskil (aka tallguysd, tallflyer) for plans for this awesome 3D plane, it's the most fun to fly of all my models!
I hope you've learned something new or at least taken away a few ideas to try yourself!