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Wind Tunnel Model Molds

Wind Tunnel Model Molds

(OP)
Hi,

I am currently researching methods available for manufacturing a half-span wing model (approx 0.5m span, low sweep delta wing of varying cross section) to be used in wind tunnel experiments. A recent paper suggested the use of epoxy and micro glass beads injected into an aluminium mold for manufacturing the wing - do you know of any UK companies who provide this service or any other possible methods for producing a mold suitable for wind tunnel application? Any help or advice is much appreciated.

James

RE: Wind Tunnel Model Molds

How many identical airfoils do you need?

If it's only one, ask a CNC house to machine the part from the prototyping board they sometimes use for checking CNC programs. ... or any material that meets your requirements.

Milling a mold for an airfoil is very much more difficult than just machining the airfoil itself from a billet.

Mike Halloran
Pembroke Pines, FL, USA

RE: Wind Tunnel Model Molds

I spent some time working as an engineer for a company that designed and built wind tunnel models. Every single model the company built while I was there was CNC machined from stainless steel or aluminum, and I never saw one molded from plastic or composite laminate. The small-scale, high-speed models were usually made from 17-4 cres due to temperature and stress levels the model experienced in the tunnel. The larger scale, subsonic models were made from aluminum.

There were three main reasons for CNC machining the models from metal. First, the smaller the scale of the model, the more critical the accuracy of the OML becomes. And directly CNC machining the OML surface using metal is the most accurate method. Second, most of the models required various test configurations with different positions for flaps, slats, landing gear, rudder, elevator, etc. It is much easier to build a metal model where different flaps, slats, rudders, etc. can be bolted on. Third, many models required large arrays of tiny surface ports so that local surface pressures can be measured. Some models had dozens of these tiny (<1.0mm) surface ports, and each one was connected to common pressure transducer interface using a tiny stainless steel tube. The model had to be machined in pieces so that the tiny tubes could be brazed to each port at the underside of the OML, and then routed internally through the model body, down through the balance strut, and to the pressure transducer interface.

As others noted, for a one-off model 0.5M in size, it would seem to make sense to have it CNC machined in aluminum.

Regards,
Terry

RE: Wind Tunnel Model Molds

(OP)
Many thanks for the help!

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