Prop Choice

[kitfox2009]

Hi Steves
A friend of mine recently installed an IFA IVO Medium on his gyro and then took it for balancing. He ended up putting quite a few grams of weight on before it was balanced properly. This may be something to look at.

I fly a Vixen with 912UL and 72" IVO IFA UL and find it made a whole new a/c out of it. I now get full 5800 on climb out and much better cruise,
The only issue I have had is the small pinion in the center of the planetary carrier wears out quite frequently if you "adjust" too much. Big improvement over the GSC it replaced.
Cheers
Don

[DesertFox4]

I like the UL or Patriot Ivo for the 912uls. Mediums have been used with success. Yes the UL's prop in-flight pitch drive motor is a little under designed if used frequently on every take off and landing. I've killed a couple motors over the years and usually it's the cluster gears that go first. My current prop has been stuck in cruise mode for 1.5 years now but flying in southern Arizona I haven't had to do many really high density take offs where I'd need the flat pitch and full power or short runways with obstructions. I can still cruise at 120 -125 mph and it tops out at 132 mph in this setting. Static run ups yield about 5050 to 5100 rpms.

The Rotax 912uls will induce some cavitation with the UL Ivo if you advance the throttle extra quick from a complete stop. It only lasts a second or maybe two before the prop bites fully. The UL Ivo seems to be pretty much maxed out at 100 hp.

No cavitation with the Med. though. The Medium 3 blade is on the verge of being heavy for the gearbox. A good dynamic balancing may help a great deal with some of your vibration issue regardless.

** During shut down if you will try this little procedure you may greatly reduce gearbox stress and avoid the violent compression stop from just shutting off the ignitions.

It takes a few times to get the timing just right so give it a chance.

When ready to shut down, set rpms to about 2,000 or 2,200 but keep your hand on the throttle. At the same time you are quickly shutting off both ignitions be pulling the throttle to idle stop. The prop should slow down smoothly like a Lycoming or Continental with no abrupt compression stop. Again it takes a little practice and I still mess it up once in a while but even then the stop is much smoother. Give it a go next shut down.

[Slyfox]

I first had the patriot prop inflight adjust on my 912ul. It was a good prop, but the motor always blew out the gears. When I went to the Uls motor I used the same prop. yes it did cavitate if I put too much power to it. I went and bought the medium prop, wow what a difference. no more cavitation and no more problems with the gears. just pure enjoyment. if you have the money, get the right prop for the uls.

[Steves142]

Thanks guys for the suggestions.
Does this make any sense? An IVO medium 3 blade @ 14.2 lbs is on the verge of being heavy, changing it to a two blade @ 11.2 lbs shouldn't be a problem for the gear box and any vibration problems could most likely be a balance issue.
I have access to a ul 3 blade so I could make the change if necessary but like I said, I really like the performance of the med 2 blade. That and the blades on the ul remind me of the strings on a weed wacker.
I just don't want any problems with the gear box down the road.
I'll try your shut down method D.F. before I do anything and see if that helps.
Thanks again

[Slyfox]

Yes I did balance my prop, I own a dynovibe. It did take a little bit to get it balanced. My answer to the vibration on shut down is to back off my idle screws about 1/2 turn, this makes the idle about 500rpm. I don't run it there, it's mainly for those real short approach to landing I so much love. and when shutting down I pull the throttle all the way off and kill the mags at the same time, nice smooth shut down. I use the inflight adjustments on my prop all the time, makes for a nice leap off the runway and a predictable landing. many times on landing I will pull the throttle all the way off(see my rpm above) combined low rpm and flat prop, wow, nice short landing without using flaps. down in about 300ft. the way I have my airplane set up, I couldn't emagine anything different.

[jrevens]

Slyfox,

Do you have the small "cap" spinner on your Ivo, & if so how do you add weights for balancing?

[Slyfox]

I actually put the fiberglass spinner on mine. I went and used auto weights for balancing with the stick um on the back(first put them on the ouside). after balancing I put the weight on the inside and than used pop rivets to secure them. I would use aluminum rivets and the small washers on the inside, keeps the rivet from pulling through the weight. I've had mine on for almost 3 years and about 400hrs. still like I just put them on. but like any weight you put it as one of your precheck on the aircraft to make sure they stay in place.