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Thread: Best Climb Prop for PA16 108HP? Will it Help?

  1. #1

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    Default Best Climb Prop for PA16 108HP? Will it Help?

    Currently have a wood Sensenich W74FM-49 propeller. I've had some very slow climb moments, of course more in the summer, and wondering if installing a climb prop will help out my 108HP engine get up and out quicker and more safely?

    What is the absolute best and approved climb propeller for the PA-16 with 108HP engine? How much of a difference will I notice?

    I want added safety on shorter runways and more help on hot days. Thanks.

  2. #2
    Wag-builder's Avatar
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    Default Re: Best Climb Prop for PA16 108HP? Will it Help?

    I do not have a Clipper but looking at the recommenced Sensenich metal prop is the 76AM6-2-50 and the climb prop being the 76AM6-2-48. Those are 74" props because the -2 is the amount the diameter has been reduced and you are aalready close to the climb pitch, however the metal prop is more efficient than the wood prop. The metal prop is thinner and should turn-up better. You did not say where you are flying from or what kind of RPM you are getting from your current setup, but if you can find a prop from a Colt to try it might be the answer you seek.

    Steve

  3. #3
    Gilbert Pierce's Avatar
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    Default Re: Best Climb Prop for PA16 108HP? Will it Help?

    I had a metal Sensnich 48” on my Clipper when it had the O-235 108 hp engine. It climbed pretty well

  4. #4
    Administrator Steve Pierce's Avatar
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    Default Re: Best Climb Prop for PA16 108HP? Will it Help?

    I haven't flown the Clipper with a wood prop and O-235 but my 48" pitch metal prop climbed very well. A friend had a 50 or 51" prop and he was a hair faster but I spanked him on take-off and climb.

  5. #5
    Vagabondblues's Avatar
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    Default Re: Best Climb Prop for PA16 108HP? Will it Help?

    Did you ever consider that you have the wrong prop?

    The PA 16 TCDS originally lists the 74FM56.
    Sensenich in their 1955 application guide (on univair "resources" site) conflicts the TCDS and says 74FM50.
    The TCDS (yes props are made under TC) for the Sensenich says that the "W" Prefix was added to wood props made after 1968.

    I had a similar problem when I put a wood propeller on my Pacer. All the early data says 57 for the geometric pitch, but the current data says 54. At the time I asked Sensenich why the discrepancies and was told that they changed how they calculated the effective pitch about the time they added the "W" prefix, so about 1968. So same geometric pitch just different numbers.

    Hang with me, I am just getting started.

    The W74FM-49 installed on your PA-16 is actually the cruise prop for a 135HP PA18 per the current Sensenich application data. If you check the TCDS for that propeller you find that it is rated for the 135 HP application.

    Sensenich now lists the W76RM-2-44 as the climb prop for the PA-16 with the 108HP 235 engine. The TCDS for that propeller shows it is rated for the 110HP range.

    So did Sensenich change the application for the PA-16 somewhere around 1968 and the TCDS was never changed?

    Sorry its so convoluted, but I hope it makes sense.
    Last edited by Vagabondblues; 11-26-2018 at 06:45 PM.

  6. #6
    Vagabondblues's Avatar
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    Default Re: Best Climb Prop for PA16 108HP? Will it Help?

    Two other maintenance thoughts about the "slow climb moments"

    The 235 engine uses solid lifters. The lifters require adjustments every 100 hours. If the cold clearance exceeds the maximum the valves will open late and close early changing engine performance.

    Wood prop attach bolts should be re-torqued every 50 hours. More likely they should be re-torqued every season change. If you lost torque the hub will be charred and slip in the friction plates under load.

  7. #7

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    Default Re: Best Climb Prop for PA16 108HP? Will it Help?

    Have 76AM-2-42pitch for sale. On my experimental cub Would make 100 mph at 2500rpm. Definatly a climb prop fresh overhaul in like new condition. $800

  8. #8
    dhillier's Avatar
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    Default Re: Best Climb Prop for PA16 108HP? Will it Help?

    I recently re-pitched my Sensenich 76AM6-2 from 52 (cruise) to 48 (climb). It is fitted to my Clipper with an O-235.
    I am pleased with the change. With the 52, max rpm in the cruise was only about 2200 giving about 95-100 mph IAS. I felt the engine was “over propped” and just did not have the power to get the most from the prop. Now, with the 48, I see 2450 rpm and 110 mph. Fuel burn appears to have changed very little - I plan on 30 litres an hour (8 US gal) and usually get slightly better (~2000amsl ISA 2300 rpm 105mph full rich).

    Take off performance is great considering no flap and the O-235. Empty weight is 999lbs. No problems operating into and out of 1300 feet with 2 x 190 lb and full nose.

    Overall I am pleased with the change to the climb prop but sometimes wonder if the regular 50 inch prop would have been an ideal compromise.

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