PA18-180 4 blade Prop

We have a PA18-180 towplane with 2 blade metal prop at East Sussex Gliding Club, UK and we have a noise problem with the local residents. We'd like to fit a 4 blade prop, but another club fitted one to a PA18-180 and the pilots reported severe vibration - they thought the tail would fall off! So word has got around that it's impossible to do. That is obviously nonsense as Bert TW's club operate one and there are two in Switzerland operated by the Groupe des Pilots de Montagne at Aeroclub Geneve for a long time. These ones seem to have a crankshaft extension- the prop stands much further forward than the standard 2 blade. Is that of significance? Any views on this? And will it make it quieter? We have a large muffler already.

MIke Millar

Mike,

Be careful, one has heard that the resonance on the cub at
Booker was quite exciting, but this story may have been
elongated through time.

Mike Barnett (UK Hoffman dealer) would have been involved and
should be able to give you the definitive answers:

Skycraft Services Ltd.
Albany House
GB-Litlington,
Cambridgeshire SG8 0QE
Fon: 01763 852150
Fax: 01763 852593
www.skycraft.co.uk


The prop sits further forward as the 4 blader requires a spacer
between it and the crank hub.

For what its worth 4 blades can shift the noise into a more
annoying band for some people (I'm at CGC and we know a
thing or two about keeping peace with the neighbours)

GG


At 22:25 13 July 2012, Mike Millar wrote:

We have a PA18-180 towplane with 2 blade metal prop at East
Sussex
Gliding Club, UK and we have a noise problem with the local
residents.
We'd like to fit a 4 blade prop, but another club fitted one to a
PA18-180 and the pilots reported severe vibration - they
thought the
tail would fall off! So word has got around that it's impossible
to do.
That is obviously nonsense as Bert TW's club operate one and
there are
two in Switzerland operated by the Groupe des Pilots de
Montagne at
Aeroclub Geneve for a long time. These ones seem to have a
crankshaft
extension- the prop stands much further forward than the
standard 2
blade. Is that of significance? Any views on this? And will it
make it
quieter? We have a large muffler already.

MIke Millar




--
Mike Millar

It might help you to get in touch with Hugh Woodsend. He did some test
flying of Supercubs with 2 and 4 blade props. IIRC, he identified a
sensitivity between the longitudinal location and performance, and that
might tie in to the thing heard about a crankshaft extension.

Chris N

Thanks very much, Gav and Chris for your most useful info. I've also been in contact directly with Dave Bullock who says there is a significant reduction in performance with 4 blades. Our Super Cub came from Booker a few years ago. Unfortunately at Ringmer we had to borrow Nympsfield's Super Decathlon recently and the locals noted that it was significantly quieter. Of course the performance was not as good. We also had a trial of the Eurofox, which they also cottoned on to and are now expecting that we can do something about the noise. Although we have 800m at Ringmer there is a significant slope. The Eurofox had acceptable takeoff performance downhill, although the tow times were doubled - in fact one student pulled off at 1500ft thinking they were at 2500ft! But it would definitely be out uphill in a north easterly. It's a difficult problem and I suppose if anyone had found a good solution we'd all be using it.

Solution for slow climbs, Pawnee 250HP, straight pipes, no muffler, 2 blade fixed pitch.
Yea, it's noisy, but of short duration.

I know of people using the 4 blade noise reduction prop on Pawnees, but not Super Cubs.
Are you using 150HP SCubs, or converted to180 HP?

T

Originally Posted by T[_2_]

Solution for slow climbs, Pawnee 250HP, straight pipes, no muffler, 2 blade fixed pitch.
Yea, it's noisy, but of short duration.

I know of people using the 4 blade noise reduction prop on Pawnees, but not Super Cubs.
Are you using 150HP SCubs, or converted to180 HP?

T

It's a 180 HP Super Cub. I'm no expert on the Supercub genealogy - were any 180HP factory built or were they all converted 150's?

Thanks

Mike

Check with Mile High Gliding in Boulder Colorado. They have a pawnee with a 4 blad prop. I visited them a few weeks ago and I was amazed how quiet their tow plane is. You can hear the engine but it seems that there is no noise coming out of the prop.

On Jul 15, 1:33*pm, Bastoune wrote:
Check with Mile High Gliding in Boulder Colorado. They have a pawnee with a 4 blad prop. I visited them a few weeks ago and I was amazed how quiet their tow plane is. You can hear the engine but it seems that there is no noise coming out of the prop.

After being exposed to US Pawnees for years I was amazed at how quiet
the Pawnee was at Challock (Kent U.K) when I visited a couple of
years ago. The combination of a 4 blade prop and a good muffler made
the tug inaudible from the launch point before it was halfway through
the takeoff roll. Of course that could mean the takeoff roll was
really long but I don't remember that it was.

Andy

On Sunday, July 15, 2012 5:50:18 PM UTC-5, Andy wrote:
On Jul 15, 1:33*pm, Bastoune > wrote:
> Check with Mile High Gliding in Boulder Colorado. They have a pawnee with a 4 blad prop. I visited them a few weeks ago and I was amazed how quiet their tow plane is. You can hear the engine but it seems that there is no noise coming out of the prop.

After being exposed to US Pawnees for years I was amazed at how quiet
the Pawnee was at Challock (Kent U.K) when I visited a couple of
years ago. The combination of a 4 blade prop and a good muffler made
the tug inaudible from the launch point before it was halfway through
the takeoff roll. Of course that could mean the takeoff roll was
really long but I don't remember that it was.

Andy

Actually the Pawnee is with the Soaring Society of Boulder and we are being pulled by it all week at the SSB's Dalhart, Texas XC Camp.

I am not sure which engine size it has (don't think it'd be the 180hp, probably the 235 or 260 version) but I'll ask tomorrow. Will also try to get a few pics if you're interested. The folks from Boulder reported the prop has about a 30% reduction in power/efficiency...but that sucker sure is quiet. I can be on the ramp ~50-60 feet away from it when it taxi's up and maintain a normal level of conversation with someone standing next to me...not like the 2-bladed Pawnee back at home. The N-number is N8808L.

Regards,

Rob S.
ZAP

On Monday, July 16, 2012 9:20:59 PM UTC-7, RAS56 wrote:
The folks from Boulder reported the prop has about a 30% reduction in power/efficiency...but that sucker sure is quiet. Rob S.
ZAP


There used to be one on a Pawnee at the now defunct "Soar Minden", that is until it departed the Pawnee like a frisbee in flight. (Seems it really IS important to retorque those prop bolts after a few hours operating in a dry climate.)

Likewise, while quiet, the big complaint was poor climb rate, especially at higher altitude. I wasn't towing back then, so have no first hand experience.

bumper