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I had posted a link to a vid of a 701 weaving through the trees over
on .piloting. At some point down the line I expressed interest in a VW powered 701. One guy said he figured a VW would melt down in an aircraft cowling when producing no more that 50HP. He provided a link to Bob Hoover's blog, which had an entry "The Christmas Engine", in which he states pretty flatly that: 1) No way to get 80 (let alone 100) HP out of an aircooled VW for any extended period of time. 2) No way to cool an engine at those HP values if you could get them, so you either get meltdown or very low time between overhauls. Bob's blog looks as though he's talking direct drive. That pretty much lines up with what I've read on the Great Plains website. GP says you can only get higher HP from the VW by PSRU. That I can believe, on the general principle that any engine has higher HP at higher RPM. Since the VW wasn't designed to spin propellers, well, the best HP values vs RPM don't align nicely for a direct drive VW and a propeller, do they? That stands to reason. So I'm asking this: for you VW people builders, what about cooling, and is there some dyno data available from VWs spinning props with PSRUs and direct drive available? Something somebody has been willing to publish? What about meltdowns? Because if what Bob Hoover says is true then it seems to me there's no way Great Plains should be making a living -- unless their customers never have checked the numbers they GP claims. GP has a lot of customers. You'd think they'd be screaming bloody murder if they couldn't at least get close to 80 for takeoff. I'm more concerned with thrust and cooling, though, than some HP number. What gives? What's "the truth"? |
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