I also found a very good aluminum spar at Carlson Aircraft supply. I used Foilsim and plotted one that is a very good match to the CB-1 plans. I found these same airfoils in several on line data bases. The Hatz Bantam uses the smoothed version. There are several Clark_ airfoils in the database that are completely different than the Y and all of the Y foils are basically the same (how's that for muddying the water). I plotted all three airfoils with AutoCad and this one came out very close to the plans version. The SM stands for smoothed (the ordinates show 11.7 percent smoothed). I found three ClarkY airfoils in the UIUC database referenced in "Airfoil Optimizer". Chuck Brownlow, pres., American Hatz Assn. The beauty of this forum is that we learn about aircraft building on so many different levels, from the most basic and practical to the most technical and mathematical! Thanks for the great question and for the great answers. no abrupt changes in curvature continuity). This will ensure two things, the curves pass through the points specified and secondly the curve will be smooth (i.e. Long story short, you want the person to use Non-Uniform Rational B-Splines (NURBS). Also adding to the confusion, not all CAD applications have the same name for a given mathematical definition. Unfortunately, most CAD users don't understand the mathematics behind the curves they are creating.
You can almost bet that no two were ever created exactly the same. Instead, they created the coordinate tables so draftsmen could lay out the points and fit a curve through them using a French Curve, spline or other drafting tool. That way, every point would have been defined. If they had, they would have given us the equation for the curves and not just the points. NACA didn't envision CAD programs when they created the coordinate tables for the airfoils. You may be seeing different profile shapes due to the type of curve your CAD person is using. I am having our CADD people plot the plan drawing into Autocad. Given the flight proven results of the profile in the plans, I'd disregard your CADD profile, and model the plans.Īnd as for building out of aluminum, I'm sure you're about to hear from Randy Brooks. I imagine you've latched on to a different version. I have not determined "which" Clark-Y the Hatz plans is, to be able to use the profile data from the NACA for loads analyses. They reference different profiles, with different pressure and moment data. I found a similar problem when researching the NACA TN's and TR's. Is the Hatz airfoil a true Clark Y or has it been modified? If it has been modified why? Also if any one has built their wings with aluminum components can you share your experience with me. Prior to getting my plans I ran a CADD dseign for a Clark Y airfoil with a 50" chord.The CADD design appears to have more angle at the trailing edge than the drawing with the plans. I am considering making the wing ribs and maybe the spars from aluminum or an aluminum composite material (see - Reynobond). We can laser cut, water jet cut and weld all types of shapes and material. I am in the architectural metals business. I plan on using the best features of both. I have purchased both the CB-1 plans and the classic. Printer-friendly copy Email this topic to a friendīuilding the Biplanes Building the Hatz CB-1 Topic #152 American Hatz Association Forum - Clark Y AirfoilĪmerican Hatz Association Forum Subject: "Clark Y Airfoil"
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