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Thread: Replacement engines for a Lazair III?

  1. #1

    Join Date
    Jan 2020
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    2

    Replacement engines for a Lazair III?

    Currently equipped with twin Rotax 185's - 9hp (7kW) at 5000 RPM - approximately 60 lbs total. Factory option was twin JPX PUL 425's - 26hp (19kW) at 4600 RPM - 38 lbs each. Useful load with the twin Rotax setup is 240. I weigh 250. My thought is that if I increase thrust without substantially increasing weight, I can gain useful load, but I'm not an engineer. What are your thoughts? Am I thinking straight? And if so, what engine should I be looking at?

  2. #2
    Dana's Avatar
    Join Date
    Jul 2011
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    833
    Modern paramotor engines (20-30HP and under 30#) would be a good place to start.

    Useful load or gross weight could be limited by any one of a number of factors. If the limit is structural, adding power won't increase the safe useful load. If, OTOH, climb performance is the limiting factor, you gain useful load by adding power. What was the useful load with the optional JPX engines?

  3. #3

    Join Date
    Sep 2015
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    3
    Maybe the DLE430 engine may suit - claimed 42hp and 70lbs or 2 x DLE200 claimed 20hp at 27.5 lbs each

  4. #4

    Join Date
    Jan 2020
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    Not sure. I'm not having much luck with Google searches.

  5. #5
    Dana's Avatar
    Join Date
    Jul 2011
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    833
    According to LazairInfo.com, the Lazair I has a max takeoff weight of 400 lbs, but they give the load limits of +4/-2 at 310 lbs. That works out to load limits of +3.1/-1.55, which is comparable to normal category for certificated aircraft. Empty weight is quoted at 142lbs, so a useful load of 258. The III should be stronger but also heavier?

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