Description from Charlie Pieroth

XCH-6 built by Dynamic Developments, the joint venture by Carl and Son, and Grumman.

The XCH-6 first flew in August/September time frame of 1959. Background in photo appears to be the Great South Bay of Long Island where Dynamic Developments had their facilities in an old seaplane hanger in Babylon. Boat driver looks like Chuck Tilgner (sp?), who was PE on the XCH-6 program and is probably the late fall/winter of 1959/60 time frame.

XCH-6 had a 19 foot aluminum hull built by Grumman with similar lines to the popular Grumman 16 foot runabout. The XCH-6 however had a step, which was a holdover from Grumman's experience on seaplanes. XCH-6 propulsion was a General Electric gas turbine greatly derated to about 250-300 HP. The hull had a 4 foot stern extension to accommodate the gas turbine. Main foils and struts were patterned after those eventually used on the MARAD Denison. If I remember correctly they were probably manufactured from aluminum billets by using straight line chord cuts with a hand router and hand filing. This is the process we used in mid 1960 to manufacture the foils and struts for the Great Expectation, a 1/5.5 scale flying model of the Denison. The XCH-6 used super cavitating propellers. The boat was very weight sensitive due to the shear limits on the transmission.

About the 1961/62 time frame Grumman began to market a hydrofoil kit for their 16 foot runabout, which was one the the pleasure boats manufactured along with canoes in upstate New York. The tradesman for the kit was also "Sea Wings". The foils and struts were basically a scale version of those on the XCH-6. Propulsion for the 16 foot runabout was a standard long shaft 35 HP Johnson/Evinrude, which was not connected to the rear foil assembly. (I would be interested if anyone has any info on the availability of a old 16 foot Grumman runabout with foils.) The runabout ran beautiful, as long as the foils and struts were retracted between use and kept clean.

I worked at Dynamic Development while in college during the summers of 1959 and 1960, doing a number of tasks; including occasional summer swims in the Great South Bay to engage the downlinks on the XCH-6. Hope this has been helpful. I will try to answer from recall any questions that folks may have.

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