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Anyone used an adjustable pitch prop?


Hann__
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I fly a Moster-engined machine, in level flight i`m doing about ~6000rpm - sometimes slightly more, sometimes slightly less, i think that`s too high.

I`m sure that a relatively large PPG motor like the Moster doesn`t need to spin at over two-thirds engine speed to maintain level flight - surely there`s not that much power required to spin the prop at the speed needed for just cruising, i would think that the prop doesn`t provide a massive load to the engine?

I only do gentle XC flying of about two - 2 1/2 hours, not much full throttle after take-offs (except when going for mile-high altitudes).

A bit less fuel burn would be nice, too.

My flying would be much more relaxed if i could reduce revs nearer the 5000rpm mark - there`s a huge difference to the feel even when i fly at 5500rpm, i`d also like to have plenty of fuel in reserve in case of a slow slog back to the field such as if the wind changes direction - or if i get carried away and venture too far on the outward leg!

I know from motorcycle experience that messing around with sprocket sizes/drive ratios does not necessarily give the results you are hoping for, the manufacturers tend to get it right, and the gearing they choose is the best allround combination for power delivery, flexibility and economy.

I get the impression that PPG makers tend to go for the most power they can from any particular motor/prop combination ( so choose props with smaller AOA and faster engine speeds), i would like to trade some of my excess power for reduced engine speed.

Being able to alter the AOA of the prop blades would give me infinite possibilities for making changes.

Do you think an adjustable pitch prop would be a worthwhile investment, anyone ever used one?

Don`t tell me to buy a V5, i`d love one, but i`m not changing motors just yet!

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I have the 185 Moster in my Zenith as well. I can't help with reducing your RPM other than buying a slower wing. You don't mention what you're flying under.

I'd like to know what your fuel consumption is ? I'm 83kg and under my Roadster 1, 26m I get about 4.5 lits per hour.

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For what you want to do providing you have the correct to fitted now is to change the drive ratio

Hi Pete,

I have thought of this too.

I expect the large pulley is bespoke and made by/for Vittorazi, but if the small pulley is an `off the shelf` item there is a chance that there are alternatve sizes...

The Moster seems to have two reduction ratios, i already have the larger small pulley and the smaller large pulley.

Rob,

My fuel consumpton is the same as you - i average about 4.5l/hr give or take flying at 25/26 mph neutral trim.

I fly an Apco Lift EZ medum 27.5M (100 - 165kg) and am right in the middle at my weight.

I deffo don`t want to fly slower..

As i mentioned above, if i could get the engine speed down to 5500`ish the flights would be a lot quieter, calmer and more relaxed, the engine tends to `shout` at 6000+.

This is only fine-tuning my flying, if nothing can be done then so be it, i`m happy with my set-up overall.

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I fly an Apco Lift EZ medum 27.5M (100 - 165kg) and am right in the middle at my weight.

I deffo don`t want to fly slower..

As i mentioned above, if i could get the engine speed down to 5500`ish the flights would be a lot quieter, calmer and more relaxed, the engine tends to `shout` at 6000+.

This is only fine-tuning my flying, if nothing can be done then so be it, i`m happy with my set-up overall.

If you alter the prop pitch you will overload the engine as in driving uphill in top gear

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If you alter the prop pitch you will overload the engine as in driving uphill in top gear

Yes, i know what you mean and that`s a possibility if you go too far, as i alluded to above sometmes altering things doesn`t get the results you want and can go the other way..

The trouble is, as a tinkerer, footerer, and manic mechanic i`ve always got the `what if` question floating around in my head, and am never satisfied until i try things myself.

Maybe this time i should just forget about it and enjoy the flying.

Rob, what sort of engine speeds do you see with your Moster?

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  • 2 weeks later...

I run an E props NG_D 1.3m 3 blade.. awesome prop... Can be set for MAX POWER or best Eco.. faster spool up than say a Helix HF40 1.3m as the E props weigh allot less. E props are also FULL carbon unlike helix that just have nice Carbon laminated outer shell.. 

  • Upvote 2
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Or any other of the 'Carbon' props for that matter (as not to pick on Helix) which are 1x 200g layer of 2x2 plain hand lay with polyester resin, backed up with 2 oz chop strand fibreglass mat (same as a garden pond) and then filled with Polyurethane balls mixed with cheap resin. :-) 

SW :D

  

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