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About car body materials...

Discussion in 'Ask The Pros' started by Roadrunner, Aug 18, 2020.

  1. Roadrunner

    Roadrunner Pinewood Ninja

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    I’ve got a question... I’ve been looking at the rules. Every class rules ( with the exception of MCR ) contain this line :

    Car Body ( the wooden/material structure that holds the weight, axles and other add ons)

    I’m interpreting this to mean that wood isn’t specifically required. It can be made of wood or some other material...

    Can I get a ruling on this before I dive too deeply into yet another rabbit hole? Thanks.
     
  2. DerbyDad4Hire

    DerbyDad4Hire Administrator Staff Member 25+ Pro Race Wins! National Champion

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    Any material is allowed.
     
  3. Roadrunner

    Roadrunner Pinewood Ninja

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    Thanks for the clarification. That could lead to some outside of the box thinking. But I’m probably not thinking of anything that hasn’t been done before.

    I’m curious to know if anyone else here has tried anything using materials or techniques not commonly used in pwd? Success or failure, it’s all good. I enjoy the process. It’s about the journey, not the destination...
     
  4. Jupiter 2.9

    Jupiter 2.9 Workshop Leader Pro Racer

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    3-D printed bodies are becoming common in bearing classes but I haven't noticed any in BASX or Fender classes.
    No reason it wouldn't work.
    Saw one out of clear lexan but it was heavy.
     
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  5. Roadrunner

    Roadrunner Pinewood Ninja

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    Yeah, bearing classes - razr or unlimited are very interesting. Not that I’d be competitive, but it’s something I’ve been thinking about for a while.
     
  6. Brian Stanley

    Brian Stanley Council Champion Pro Racer

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    I've experimented around a bit with different materials. Honestly, it's hard to beat wood for weight and strength, a least for our purposes.
     
  7. Roadrunner

    Roadrunner Pinewood Ninja

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    I agree with that. Strength to weight ratio is very good. My problem has been that thin sections tend to twist or bend. I’m a believer in alignment as the foundation of a fast car. Hard to get good alignment when my chassis won’t lay flat.
     
  8. Eric Scheid

    Eric Scheid Pack Champion

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    Try routing channels. Thinking along the lines of I beam mechanics. Might be less twisting but as things get thinner and smaller easier said than done.
     
  9. xtremethings

    xtremethings Pinewood Ninja

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    I’m not an expert by any means, but I get my sides down to 1/16” and leave 1/4” at the very front and both axle locations. Then I add two balsa beams between the axle locations. What makes mine crazy rigid is the fact I laminate some proprietary carbon fiber to the top and bottom. I’m sure you could have good success with 1/64 birch ply though. As for weight, my skinned frames come out to just under 12 grams. I’m sure you could get lighter, but I could get my front weight way down there.

    Skinned Body
    3B51B8DD-5E63-4104-8F0D-4B7515800F1F.jpeg

    With Areo
    237013E0-7039-47E3-AB47-A680572F9D90.jpeg
     
  10. Roadrunner

    Roadrunner Pinewood Ninja

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    Nice looking car. I thought carbon fiber veneer would be heavier than that. What gauge are you using? .008 is the thinnest that I’ve seen.
     
  11. xtremethings

    xtremethings Pinewood Ninja

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    That’s very close to what I’ve got, but just don’t get the adhesive backed stuff and CA it to a body that was extremely lightened by taking as much material off as possible.

    Here’s a picture of one that hasn’t been lightened completely. The completed one ended up at 4.6 grams with the two balsa ribs installed. C63461AE-CCBF-496D-A5C7-65A23E2873D7.jpeg
     
  12. Roadrunner

    Roadrunner Pinewood Ninja

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    And you apply the veneer with the fibers running diagonally,the two sides opposite directions? After another look I see it’s not diagonal...
     
  13. xtremethings

    xtremethings Pinewood Ninja

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    I tried it diagonal one time with no noticeable difference in rigidity. Plus you’ll get a lot more cars per sheet if you run the fibers square to the body.
     
  14. Mojo Racing

    Mojo Racing National Contender Pro Racer

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    I have tried it in multiple configurations. I haven't seen a noticeable difference in speed running the grains one way or another. I have noticed that my cars are more rigid and run better with at least a full top cover (more than just monokote or tape).
     
  15. Roadrunner

    Roadrunner Pinewood Ninja

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    I haven’t seen much written here about carbon fiber veneer. Is this material commonly used by the fast guys? Probably not in fender classes as the fenders are structural and add stiffness...
     
  16. Mojo Racing

    Mojo Racing National Contender Pro Racer

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    I know a few people who use carbon fiber. Most people will cover with 1/64" plywood (sanded) because of ease and price
     
  17. Roadrunner

    Roadrunner Pinewood Ninja

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    Using the published weight of .008 carbon fiber veneer for comparison, the 1/64 plywood panel is lighter too... but there are probably other factors to consider
     
  18. Mojo Racing

    Mojo Racing National Contender Pro Racer

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    yeahhhhh… you don't want to sand carbon fiber. The dust particles are hazardous to your health.
     
  19. OneSpartan

    OneSpartan Pinewood Ninja

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    I'm very interested in the idea of completely covering the top of the car with carbon fiber or 1/64 ply. I've only covered the weight pocket to date but I'm also struggling with cars losing their alignment somewhere in the build process. My guess is the car gets the slightest bit of twist somehow, maybe when the glue dries (no longer using CA for this reason), maybe when I work an axle in/out to size the axle holes (which I admittedly do too late in the build). My next round of builds I plan on trying to add something to the top to take any flex out of the body.

    Maybe beyond the scope of this thread, but curious about the increased weight of the carbon fiber or ply on top. With the availability of the super heavy bars for the rear, my guess is one could still achieve their desired weight on each wheel even with the heavier body. I've tried quite unsuccessfully to use the 70g bars and had to move a cube forward to get more than 8g on the DFW. Maybe a heavier body would work better in this case and definitely going to go this route for the next round of builds.
     
  20. Mojo Racing

    Mojo Racing National Contender Pro Racer

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    Even if you reach the desired weight on your DFW, the idea is to move the weight as far back as possible and keep your car stable.

    The longer your weight stays on the hill, the more "engine" your car has. As soon as your weight hits the flat, it no longer speeds up. So, any weight, as miniscule as it may be, that is unnecessarily forward will take away from the potential speed your car has.

    You want the lightest STABLE body possible.
     

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