Prop Pitch

[rv3flier]

Thanks jetguy - since the pitot is installed the spinner will go back on.

[rvbuilder2002]

Actually, if you have the old version of the prop hub (the one with the white plastic indexing barrel in the center) you can run the engine with the spinner removed.
If you have the new style hub that uses the indexing pins for pitch adjustment, the spinner should be installed for ground runs.

[rv3flier]

I think I have the old style prop hub as there's a white plastic bushing in the center and there're no indexing marks that I can see. The prop hub and blades were replaced by Sensenich in June 2011.

As a follow up, the static rpm went from 4700 to 4850 but a remeasurement of the prop blade angles indicated a change of a tenth degree toward a flatter pitch. I did run the motor for 5 minutes at 2450 rpm and retorqued the bolts before doing the static test. In any case it looks like another 2 tenths of a degree (66.5) should get me close to 4950.

[Sink]

When working on a project with Sensenich a few years back they even said they set their blades by hand. They said that the pins looked like a good idea on paper, but even with the white plastic indexer in the center by hand is more accurate and easier to be exact over the pins. Pins are a good way to get in the ballpark. The pin indexing doesn't always get you the exact rpm result you may be shooting for too.

[rv3flier]

I can move one blade quite a bit before the other one will move - hard to believe that mine has indexing pins. I was able to get 66.5* but only gained 30 rpm static so I'm now at 4880 at 13* C. I'm going to leave it alone until I see how much the static rpm changes with OAT and normal operating oil temps. I'm getting 5150 rpm at 75 kts on climb out.

Thanks for the feedback.

[Phantom30]

Originally Posted by roger lee

Nothing personal with me.
I love to swap ideas, training methods, shortcuts and especially new information just out hot off the press from MFG's like Rotax and of course cat skinning. It is just like debate class was back in school. It would be a dull world if we all thought alike and then nothing would ever get done. If you can't be opened minded and learn why live.

I have heard from several friends with RV's that Scott and I are entertaining and we don't even get paid for it.

p.s
Just an FYI
I just had an RV12 owner call this afternoon from northern AZ. with overheating problems. He was using Evans coolant. It is not recommended by Rotax any longer and carries a 20F-30F temp penalty. Better to stay with the now more conventional recommended 50/50 mix with more heat absorbing properties.

Roger....that guy from AZ would'nt possible be "first name Bob" by any chance?

[Harvey rv12]

I recently purchased a built rv-12. I've been
Reading about setting prop pitch using
a home made digital protractor using
a sears digital level. I believe Tony T.
and rv3flier have made them. Could you
share the design so I can build one?.
I have an E-LSA built rv-12 with
sensenich adjustable prop, and want to
check the pitch and maximize the
usefulness of the prop.

Thanks in advance
Tom O.

[Sink]

Hi Tom,

You can certainly use a nice prop protractor like this one;

http://www.aircraft-spruce.com/catal...clickkey=29175

You can also just use a 12" digital torpedo level like the one you may have from Sears with a rubberband and or use both. I use both.

You already have a flying aircraft so static is probably already close and it flys so you need to just fine tune the pitch for the best all around balanced performance since we use ground adjustable props. After a few years of testing for different companies the best all around Rotax WOT rpm at your average altitude is around 5600-5650 rpm at WOT in flat and level flight.
If you live in Los Angeles and never fly over 3K then set it for that. If you live in Mammoth, CA with a field elevation of 7100+' and always fly at 11K-13K then the pitch should be set for that.
Never have the prop adjusted so it is below 5500 rpm at WOT.

Mark each blade with a mark approximately 8"-9" back from the tip on each blade. Always loosen the larger 8mm hub bolts first and no need to loosen them any more than you can turn them by hand when loose. Face the plane and rotate the first blade around so it is on your right. Place the level on the blade so it is level with the ground. If we do this for each blade they will all be equal. Now place the level on the back side of the blade so one end points to the floor. Put the rubberband around the tips of the level around the blade and it will hold it in place. Look at the pitch on the level. It really doesn't matter at this point what the exact number reading is. If you need 1/2 degree adjustment to a finer pitch then loosen the other prop bolts until you can turn the blade so it is 1/2 degree flatter than the original reading. Snug the blade bolts back up, but don't worry about torquing them until you are done. Now remove the level and do the same for the other blade(s). Once done double check each blade before you torque the bolts up. Always torque the large 8mm bolts first. These are first to loosen and first to tighten. If you needed a different degree adjustment then that is what you would have done. Now go fly and see if your WOT rpm in level flight is around 5600-5650 rpm. This tends to give you the best climb, cruise, top end speed and fuel economy.


Here is a good article on prop pitch:

http://ctflier.com/index.php?/blog/6...justable-prop/


Hope this helps some.

[Gagarin737]

Originally Posted by Harvey rv12

I believe Tony T.
and rv3flier have made them. Could you
share the design so I can build one?.

Thanks in advance
Tom O.

Tony's Tools&Work Fixtures



My fixture hangs on the prop flange (only picture I could find). The tripod with the aluminium angle is to have the blade in the exact same position each time you measure:

[rv3flier]

After several more attempts to get my prop pitched to get to the 4960-5020 recommended static rpm, I've got it to 5030 with 68.4* on each blade -- (note that the degrees I measured would be different for someone else with differences in the fixture mounted to the digital level, etc.). Unfortunately, I haven't been able to get to fly at altitude as yet due to weather and an intervening trip, but I'll report in a week or so when I get the chance to fly again.