Plywood frame

[Charles Kaneb]

Has anyone built a FSAE car with a chassis structure fabricated primarily from plywood?

It seems that a fairly high stiffness-to-weight ratio could be achieved, with very few thin sections requiring precision cutting and assembly. Downsides appear to include needing additional structures to spread out point loads and the additional overall width of the car due to needing adequate EI in the side impact panels.

[PatClarke]

I don't know of any wooden FSAE cars, but in the late 1960s, the Costin Protos F2 car was pretty competitive with a laminated marine plywood chassis.

Picture of the car in action http://www.ultimatecarpage.com...Protos-Cosworth.html (http://www.ultimatecarpage.com/gallery/25921/Costin-Protos-Cosworth.html)

Picture of the chassis whilst under restoration
http://www.ultimatecarpage.com...Protos-Cosworth.html (http://www.ultimatecarpage.com/gallery/25922/Costin-Protos-Cosworth.html)

Pat

[PatClarke]

However,
This happened to Pedro Rodriguez when he had a chassis failure in 1967.

http://www.maranellomerchandis...wheel_enna_09_mm.jpg (http://www.maranellomerchandise.com/contents/media/01_pedro_rodriguez_proton_f2_crash_steering_wheel_ enna_09_mm.jpg)

Maybe it was woodworm or dry rot? http://fsae.com/groupee_common/emoticons/icon_wink.gif

Pat

[Bemo]

Your car would definitely be a legend in the FSAE community like the V8 from Washington http://fsae.com/groupee_common/emoticons/icon_wink.gif

You would have to invest some thoughts on how to properly attach the main hoop and bracings (which still have to be steel) to your plywood chassis and some other stuff concerning the SEF. But I guess this wouldn't be more complex than doing that stuff for a carbon chassis. Someone please do it and bring the car to Europe. I would love to see that!

[Will M]

From an earlier post:

*
I’m not sure if you’re familiar with it but there was one car built at my uni call the “Splinter Car”.
It used a wooden monocoque chassis by weaving thin strips of wood together to make a sheet and then epoxy just like carbon fiber.
This is the build blog. June 2008 has most of the good stuff.
http://joeharmon.blogspot.com/2008_06_01_archive.html
Real interesting but I don’t think it ever ran.
*

-William

[Drew Price]

That Splinter is badass....

[AxelRipper]

I believe my boss (was involved in the 80s) told me that at one point back then someone had done a wooden car. In the early days of Formula it wouldn't have surprised me.

[Luniz]

Plywood Chassis? DO IT!!! Oh I'd love seeing someone do that!

[Shebert]

I've seen picture of a plywood/fiberglass chassis from ETS. I think it was the first FSAE from ETS, but I'm not sure if it competed.

Maybe some of the new guys can post the picture, it must be somewhere in the office.

[Kirk Feldkamp]

Saw this today: http://orangecounty.craigslist.../rvs/3739068923.html (http://orangecounty.craigslist.org/rvs/3739068923.html)

Look fast, it won't last forever!

[Rodiman]

I have loved the idea of a plywood monocoque for a while! It could be so light, strong, cheap, and easy to manufacture. It would just be impossible to simulate, and judges would destroy you in design. But on the plus side, the shop would smell so good during manufacturing...

[PatClarke]

judges would destroy you in design.

Why would you say that Stephen? The judges are never critical of what you have done (within reason), but why you did it!

Pat

[Z]

Kirk's link above has a relevant comment, namely "... like a skateboard deck". This gives a good idea of the loads a 10 mm (3/8") thick strip of plywood can handle. Also suggests that the size of the "reinforcing patches" to carry major loads (suspension, engine, etc.) only has to be similar to the 5 or 6 cm square attachment of the skateboard's wheels, which use four x 5 or 6 mm diameter screws.

I was also in a McFine-food restaurant (???http://fsae.com/groupee_common/emoticons/icon_smile.gif) recently and the chairs there have a four legged steel base with a one-piece moulded plywood seat-and-back. This seat+back is formed from seven layers of ply, plus two outer layers of laminate (which are just paper + glue at high pressure, so just more wood really), at a total thickness of about 11 or 12 mm. Considering the supersized loadings these chairs take shows just how strong plywood can be.

So, since strength doesn't seem to be a problem for a plywood FSAE chassis, I reckon the main question is what sort of manufacturing process would you use?

Should you do a moulded, curvy, all-one-piece tub, a bit like those seat-and-backs above (and similar to conventional CF tubs)?

Or could you do it like many old-fashioned boats that use ribs (eg. the main roll-hoops), longitudinal stringers (= the side-impact structures), and multiple, initially flat, sheets of plywood joined together at the stringers?

Z

[Racer-X]

The biggest issue I see is ensuring that its uniformly stiff (is even that the right way to say that?). The imperfections that make wood so nice looking would undoubtedly get in the way of making a predictably stiff chassis. You've got grains, knots, rot, soft spots, and any laminating issues to worry about.

I'd guess that a wood car would need a higher FOS than with steel or carbon and as a result be much heavier. I mean there is no way you could ever predict the strength of plant fiber to the same accuracy as other man made materials.

Have you ever seen an old wooden rowing shell? Beautiful boats but they weigh a ton and aren't nearly as stiff as the carbon boats available now.

[Charles Kaneb]

Originally posted by Z:


So, since strength doesn't seem to be a problem for a plywood FSAE chassis, I reckon the main question is what sort of manufacturing process would you use?

Should you do a moulded, curvy, all-one-piece tub, a bit like those seat-and-backs above (and similar to conventional CF tubs)?

Or could you do it like many old-fashioned boats that use ribs (eg. the main roll-hoops), longitudinal stringers (= the side-impact structures), and multiple, initially flat, sheets of plywood joined together at the stringers?

Z

Laser-cut everything from flat sheets of plywood. Significantly cheaper than any other process - each piece takes minutes rather than hours.

I'd build it like an airplane, with circumfrential exterior panels and bulkheads. From front to rear, the bulkheads would be: the impact attenuator mounting plate which is a substantial piece of aluminum by rule, a wooden bulkhead 2-4" behind the surface of the pedals (allowed under the template rule), the front roll hoop, the main roll hoop, and the rear engine mount. I'd probably go with a 3-link live rear axle to avoid another bulkhead at the far rear of the car.

The roll hoop braces would run from the main hoop to the front hoop and help with the side impact rules. There might have to be a honeycomb core between two panels to meet side impact and torsional stiffness requirements in the center of the car.

You can get away with a lot of material volume if you're using something with a specific gravity of under 1 g/cc. The mandatory hoops and braces are 8-10 kg; for a 35 kg frame-and-body that leaves 27 kg, which is over 27 liters of material.