Rotax Propeller

Rotax 912 series discussion.

Rotax Propeller

Postby Paul Johnson » Sat Jul 15, 2017 12:45 pm

Good news that Sonex is now going to supply Rotax engine mounts for their legacy aircraft. The Sonex web site now list a Sensenich propeller for Rotax engines It's model number is WC64QR-81G, from this I take it to be 64" diameter, will longer gear legs be needed for this propeller and if so who will be supplying them as this would effect the B model as well?
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Re: Rotax Propeller

Postby Concorde » Sat Jul 15, 2017 3:09 pm

I spoke with Mark the other day and he said the 64" prop is fine with both tri gear and tail wheel ,but I forgot to ask if we need 3 blades or 2.
Ben
Sonex # 1684
Tri-Gear, Dual Control
Jabiru 3300 ?
N379BS reserved.
Winner of 2016 Prince propeller ( Crossville)
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Re: Rotax Propeller

Postby markschaible » Mon Jul 17, 2017 10:25 am

Hello SonexBuilders.net,

The Sensenich prop for Sonex/Rotax is a two blade, composite coated propeller. Longer gear legs are not needed.

Regards,
-Mark
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Re: Rotax Propeller

Postby Concorde » Mon Jul 17, 2017 3:52 pm

Mark,
I spoke with the Rockwood aviation tech today before seeing your post and he suggested to go with 3 blades. Can you please tell us the benefit of 2 vs 3 blades or it doesn't really matter which to get.
P.s. The person that I spoke to is thinking about ordering a Waiex.
Thanks
Ben
Ben
Sonex # 1684
Tri-Gear, Dual Control
Jabiru 3300 ?
N379BS reserved.
Winner of 2016 Prince propeller ( Crossville)
Concorde
 
Posts: 131
Joined: Sun Aug 10, 2014 2:11 pm
Location: North Carolina

Re: Rotax Propeller

Postby rk2436 » Mon Jul 17, 2017 9:42 pm

Most 2 blade Rotax props are 70". Probably no ground clearance at that length on the Sonex. Go with the 3 blade and don't leave torque on the ramp. You will like the 912uls it's far superior to all the other choices and no worries about Chinese parts holding your butt up in the air. Bob K
Bob K
Orig builder kit 1143
Now flying RV-12
Evergreen Park,Il
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Re: Rotax Propeller

Postby jeff0196 » Tue Jul 18, 2017 11:07 am

I have a 912 UL in my AVID MK4. It is a great little engine from my very limited experience of 50 hrs since October last year, with 320 total time on the engine. I just wanted to point out that the moment of inertia/rotational inertia is limited by Rotax for the 912's. Rotax installation manual limits the moment of inertia to 6000 kg cm2 (14.238 lb ft2) for the propeller. You can buy propellers that fit the Rotax and exceed this limit. Large diameter propellers can have high moment of inertia even if designed light. Small diameter 3 blades that are designed light are great compromise. I would personally make sure any propeller I put on my Rotax was within the moment of inertia limit. As long as I'm posting, Rotax also limits prop extensions to 120mm (4.72inches) or less.
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Re: Rotax Propeller

Postby markschaible » Tue Jul 18, 2017 5:23 pm

Hi Folks,

We always prefer to use 2-blade props to play to the strengths of our clean & fast airframes. 2 blade props minimize cost, maximize reliability, minimize balancing issues, and optimize the performance envelope at both ends of the spectrum with the superior flexibility performance characteristics of wood or wood-core props. You'll have plenty of torque for takeoff and climb performance with the Rotax and the recommended Sensenich prop, which will also help you to maximize the speedster characteristics of our airframe at the top end as-well. Sensenich has a ton of experience engineering propellers and they have a huge database of both Sonex Airframe and Rotax engine performance characteristics -- we put our trust in Sensenich fully to come-up with the best prop for the job that is best-suited to this engine and airframe combination.

Regards,
-Mark
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Re: Rotax Propeller

Postby Concorde » Tue Jul 18, 2017 7:40 pm

Thank you.
Ben
Sonex # 1684
Tri-Gear, Dual Control
Jabiru 3300 ?
N379BS reserved.
Winner of 2016 Prince propeller ( Crossville)
Concorde
 
Posts: 131
Joined: Sun Aug 10, 2014 2:11 pm
Location: North Carolina


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