Myself and 3 of my co CH750 builders have been planning to install the Rotax 912iS in our CH750s since the day that Rotax announced the release of the iS. Up to this point, there has been little information available so all of us have searched for scraps of info that can feed our hungary appetite for information.

We talked to our (Canadian) Rotax distributor at Oshkosh and as luck would have it, they had bought a CH750 kit to install a 912iS and use as a demonstrator. That was great news for us, so since then we have been waiting for the 750 to be built and flown. Rotech Research have contracted the newest Zenair Build Centre in Vernon BC which is right across the field from them to the build the airplane. The project is progressing, but no airplane goes together by itself so we somewhat impatiently wait to see a 912iS installed in a 750.

Today there was another tidbit of info released. Their build is a feature on the Rotax-Owner.com forum/information site. The site has many videos on Rotax tips, product information and reviews, etc and today they released a new series called "Rotax Builder Series". The video released today has an introduction to the series with a first look at the CH750 airframe and some of the issues with installing a 912iS in that airframe. The video is at www.rotax-owner.com. If you wish to look at the video, this site is user pay site and has annual fee of $29.95.

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Well, it’s high time I post another update on my 912iS installation on the 750. As mentioned in my last post above, I attended an accredited “Rotax Aircraft Engine Service Course for 912iS Sport” course at Rotech Research Canada in early October. The course was 3 full days and was taught by Michael M who is the face in many of the earlier Rotax-Owner videos. Mike was assisted by Rob S who has been instrumental in helping design the 912iS firewall forward for the 750 and can be seen in many of the One Week Wonder photos and vids. I could write several pages on what I learned during the course but suffice to say, the course was absolutely worth taking and I come away thoroughly impressed with the engine.

Spending the three days in Vernon, BC reinforced my belief that we are SO FORTUNATE that Rotech chose a CH750 for their first 912iS installation and contracted Skytech, who is across the field from them, to build it for them. These two companies teaming up has made things so much better for those of us that are choosing to go with the 912iS. When I read my original post from this thread, it is very apparent how naive that I was and how much Rotech and Skytek’s effort has benefitted my installation. The latest example of my installation evolution is I have decided to scrap my fuel system and go with the Rotech/Skytek design. I had designed a fuel system I thought should work fine and had already fabricated and installed it in my 750 but after talking to Mark (owner of Rotech), I decided to rip it all out and throw it in the garbage. The thoroughness of their design and testing cannot be discounted. My design may have worked. I KNOW their design works...!

Beyond all the technical stuff around this, it is fun being at both Rotech and Skytek. Mark and every one of his staff are “good people” and I thoroughly enjoy being there. Skytek is the same. Keith and Darian are the BEST. When I go visit them, I always feel guilty that I am taking up too much of their time but every time that I have been there, I stay far longer than I should. They seem genuinely happy that I am there. It is obvious that they are passionate about building airplanes.

Currently, I have the engine on the firewall and I am mostly done installing Skytek’s firewall forward REIP (Rotax Engine Installation Package). Today I was working on the cowl. I will try to update this thread occasionally in hopes that it may help some that come along later.

Joe, 

That certainly looks like a neat, professional installation! Thanks for the update and keep'em coming!

John

N750A

Looking great Joe!

Joe looking real good. Question: who provided the engine mount?
I'm installing the 912is in a CH750 CruZer but am contemplating an Airmaster prop:
http://www.airmasterpropellers.com
This adds 26 pounds and I will need to ensure the W&B is correct and that the engine mount takes this weight into account. I've been trying to get the One Week Wonder W&B info from the EAA, no luck to date.
After reading Victor Menkal's pirep ( http://www.zenith.aero/group/stolch750/forum/topics/pirep-catto-cus...) on the Catto prop with a 912 uls I may go this route with the prop, need to do more homework.
Lastly, where can I get information on the course you took?
Thanks...Don

Don, I bought the engine mount from Zenith in Mexico, MO. I believe they fabricated it there. I have been led to believe that the engine mount is a little short for the iS and a normal config’ed aircraft/load will have the w&b near the rear of the c of g. The weight of the Airmaster should work to your benefit. Not sure if you will be out the front of the c of g if you have no baggage, though. I suspect as all these configurations mature, ZAC will have more tangible info available.

The course that I took was the Rotax accredited 912iS Sport Service course which is the most basic course for this engine. I think many of the Rotax Service Centres are set up to teach courses which give participants an “Independent Rotax Maintenance Technician” (iRMT) designation. I think the course that I took was the first, or at least one of the first, iS service courses to be held for someone other than a Rotax dealer. Even though I took it at Rotech Research (North and South American distributor for Rotax Certified Aircraft Engines), I think you may be able to receive the same course at Service Centres like Lockwood. You can find more info here: http://www.rotax-owner.com/education-5/4-stroke-training

Regards,

Joe

Joe thx for the info on the course.

What are your plans to overcome the Engine mount/W&B issue? Doesn't soumd like you're going with a heavy prop so your issue would be useful load??

This could prove to be a big issue for builders...it's amazing how, what should be a minor calculation/fabrication issue can have such impact on the planes we build...also not exactly in your control.

In my case Roger has indicated that Charlie Becker at the EAA, has the OWW W&B info and I have asked Charlie to provide it since that is exactly what I'm building with the exception of the Airmaster prop. All things being equal I'd probably prefer the Catto prop if it is as good as advertised and save myself $5000. I'll share the OWW, W&B info as soon as I get it.
I agree 100% with Joe, Skytek are fantastic to work with and everything fits as advertised! Keith and Darian are great to talk to and a mine of information. I am something like the same state of installation as Joe. I have also received an Airmaster propeller which is so beautiful I want to hang it on the wall as a work of art. Keith reckons the standard 750 will just balance at the rear of the CG with the fixed pitch prop and full load. The airmaster should help - thats also what the Three washers on each engine mount bolt are for.

I'mm using the SKytek fuel system from the wing roots down. My wings are finished with 3/8 braided ss and teflon lines and I cant replace the vent line without reskinning but I am replacing he fuel inlet line with bigger stuff and following the skytek design in braided Stainless and teflon Goodridge convoluted hose which is delightfully easy to work with and flows well too and with a very small minimum bend radius.

A few words, I have spent a month on the cowl and I still haven't got a straight join between top and bottom. I am using the quarter turn quick release fittings and it all has to be "tuned" just right to make it neat - I've given up. I've also added the twp 3 inch vents on top of the nose that now seem to be deleted. Keith says that they cool the electronics at taxi speeds but aren't needed in flight. Anyway they are cheap to buy and fit which I've done and also the engine air filter intake is easy when you use West System epoxy like me.

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I just received the W&B info for the OWW...definitely out of the aft range at full load...I have no idea if the STOL version suffers the same problem.  Posted here:http://www.zenith.aero/group/750-cruzer/forum/topics/one-week-wonde...

 

I would say that for those wanting a CruZer/912is combination that Zenith has to come up with a different engine mount....this is clearly well out of range even using 170 lbs for pilot and passenger.

 

A heavy prop up front would definitely help but assuming an extra 12 pounds or so on an Airmaster, still leaves an issue with the aft range.  An additional 16 pounds would be needed on the nosewheel to get within range and then we'd have to get down to 170 lbs to make that work.

The W&B for the OWW is not the best news (and is probably driving Zenair and Skytek crazy...). It might not be such a big deal if it was only the engine to worry about, but it affects many other things such as the cowl, fuel and oil lines, etc. The cowl is just barely long enough as it is so if an inch is added to the mount , the cowl may have to be extended. I am using a 60 mm prop extension, so maybe the engine could come forward some and not interfere with the cowl.

I still have the hope that I might be okay. I  have been mounting everything that I can as far forward as possible such as the elt which I mounted under the seat. I have auto pilot servos which are mounted much further forward than the OWW. Just looking at the Cruzer, to me it looks like the tail pieces are heavier than the STOL. I am also planning to use an 8.00 X 6 aircraft tire on the nosewheel (a la Walt Snyder) which should help quite a bit. Another idea that I have is fabricating a tool box and installing it forward of the firewall. I always fly with some tools and the way I have configured my fwf, I will have the room to rivet a box onto the firewall shelf (stiffener).

And Geoff, if I understand correctly, they (Zenair/Skytek) were going to supply us with the eyebrow NACA ducts at some point in the near future and we could install them ourselves if we are so inclined. I think will install them but living in the great white north means they might not be so critical. And yes, I have worked a bit to get my cowl to fit together. The left (pilot) side requires the most work. I sanded about 5 mm off the edge of the top cowl near the centre.

Building airplanes is not for the impatient...

Joe, I think overall the CruZer is a heavier airplane than the STOL.  That's an interesting point about how a 1" engine mount extension affects so much else...the proverbial consequential damages.  The problem here is we have the tail wagging the dog.  ALL the FWF components were fabricated to fit an engine mount that is too short, so we're trying to fix the symptoms and not the problem.  I think Zenith and Skytek need to get out in front of this thing....by all accounts the combination of the STOL and/or CruZer with a Rotax 912is, is showing to be very popular.  Better to bite the bullet and get it done right.  Maybe there's another solution but I'm not smart enough to know what it is.

If I understand you correctly on the prop extension, you are adding a spacer of approximately 2 1/4" between the engine and the prop so it sounds like there is room in the cowl to accommodate this extension??  Why do you need the extension?  The heavier tire and tool box are also creative ways to get more nose heavy.  I guess if all else failed some lead weights could be added to the tip of the cowl??  Just thinking out loud here.  The overriding question though is when does the real problem get solved??

Joe, don't worry too much, the STOL bird is not as tail heavy. I'm out of Australia at the moment so I can't send you the spreadsheet or a copy of the email from Keith.

The mount may be a fraction short for the STOL 750 but Keith told me it's OK provided you are mindful to keep weight forward including adding the Three washers to push the engine forward a little. He said that a fully primed and painted aircraft, with autopilot servos, that he built was right on the rear limit at MTOW. My calculation showed that adding the airmaster puts an extra ten pounds in front and brings the CG about an inch in under those conditions.

The CRUZER? Thats a different kettle of fish...

Well, it's been more than a year since I have made the last update on the engine installation. I have got to be one of the world's slowest builders. I work on the plane almost everyday but just got to point of the first engine start. The 912iS Sport started right up as expected with zero issues (so far). I have posted the first start video here: https://www.youtube.com/watch?v=GwMD272MB7U

Dave, one of our group of six, has had his iS powered 750 up and flying for a few months already, and it runs beautifully without any issues. Dave says the 912iS is his most favourite part of his CH750. That is saying "something" considering he has a dual screen G3X with autopilot and many other bells and whistles on the great flying CH750. I am expecting the same with mine. The engine is just great and the firewall forward kit is very nicely designed. Rotech Research Canada (Canadian Rotax distributor) and Skytek Aircraft Services who developed the firewall forward kit both have proven to be premium quality vendors. If you are considering working with them, you will not go wrong.

I pretty much have the fuselage completed so the main job that I have to do now is to finish up a few details inside the wings and then install them. The doors and tail have been fitted (and removed to save space) so it should fly sometime next spring or early summer (I hope!) 

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