Science Buddies: "Ask an Expert"

Hi, I am following your instructions on how to build a subsonic open wind tunnel. However, I don't understand why the contraction cone has to be in oak. It is pretty hard and expensive to find oak boards in Sweden, and most of them are like 18 mm thick, so is it possible to make it out of ordinary 12 mm plywood instead, just like with the diffuser assembly? Thank you for a great site!

Hi,

I think you are following this guide:

https://www.sciencebuddies.org/science- ... -toc.shtml

I have no personal experience with this project so I can’t give you very authoritative advice. I suspect oak was specified to provide extra stiffness and strenght to a highly stressed section of the tunnel. I think you could substitute plywood successfully, but I would use a thickness that was very stiff and does not flex at all. I will pass your question onto the Science Buddies staff to see if they have a better answer.

Best regards,

Barrett L. Tomlinson

Okay thank you for that, barrettomlinson. I'm running a bit short on time since the whole thing has to be finished by the 11th of January, so do you know if anyone is able to provide an answer soon? Your help is greatly appreciated!

Hi Forman

Yes, Barrett is right. You can use plywood for this experiment but a thick one and not the cheap ones availabe in a craft store. I had done a similar experiment in eight grade and I had used a good quality plywood (1" thickness I believe) and it had worked successfully. Oak is definitely a stronger wood and you will be able to build a stronger wind tunnel with it. I hope it helps. The staff can shed more light on this.

Good Luck

I'm not familiar with the hardwoods commonly available in Sweeden. A fine grain dense hardwood such as a hard maple, hickory, poplar, walnut or 3/4 inch (18mm) solid plywood made from 15 to 17 thin laminates used for cabinets / furniture should be acceptable substitutes. Soft plywoods made from thick laminates will likely vibrate.

I went with 12 mm plywood anyway. I don't think it will be a problem, because it appears to me to be very solid, and I don't think it will vibrate. But we will see as soon as I test it. If you are interested in following my construction process, you can visit www.projectwindtunnel.blogspot.com Thanks everyone for helping out!