Online Community of Zenith Builders and Flyers
Dear Experienced Fellow Builders,
This will be my first build but I have been involved with aircraft restoration and maintenance a good deal of my life, principally on larger aircraft. I like the Zenith line and the company. I have looked at both aircraft designs and obviously the 701 is more affordable to build and to buy the engine. I have received the company information book and read all the material thoroughly. A STOL design is definitely my interest. I have two questions:
Any help would be appreciated before I buy the plan kit. I hate to wait until Oshkosh! Thanks.
Another consideration is time. The 750 can be completed in much less time...
Gerry, don't even bother with the 701. You are way too tall to fit without modifying the seating design. I'm 5'10" and I am bumping my head on the top window in my 701 with basically stock seating.
Additionally, after building both the 701 (from scratch) and the 750 (from kit) the 750 is a far more modern design. Zenith tried to address many of the complaints builders and pilots had about the 701 when they developed the 750. The 750 is not perfect but it shows the 20 plus year development of the 701 within its design. Many prospective builders are attracted to the 701's slightly cheaper list price but I still always recommend the 750 over the 701. A finished 750 will be worth nearly twice as much in re-sale than an equivalent 701, far more than the initial couple of thousand dollars difference in kit costs. The only reason I can see for going with the 701 is if you require the absolute shortest STOL capabilities from the plane. Most pilots can accommodate the additional fifty or so feet the 750 takes to get airborne over the 701 so STOL capabilities are not really that big of an issue. Personally, I fly my 701 primarily off of a paved runway so don't really use its STOL capabilities.
I love my 701 but if you want a plane you can fit in, one that will be worth far more when completed, and one that is easier (quicker) to build, go with the 750.
Doug and John
Thanks, that helps a lot. I was expecting the type response you folks gave, given what the book was telling me. I especially appreciate the fit comments, Doug.
Our Chapter President is building his second Kitfox. The first was totaled (he and his passenger not hurt, good emergency procedures, good flying!) when the engine starved due to movement and kinking of the fuel lines, actually on the way to Oshkosh. He is considering the Viking (Honda Fit based) Engine, previously used the 912. How do you folks feel about engines? The 912 is a great engine but pretty pricey, especially with the FFW kit.
I am 6'2" and own a CH701. Space is CRAMPED and I wouldn't think of a CH701 for anybody taller than I am.
As some people have done, I modified the top cabin to gain some headroom (Beanie mod - now standard on the CH750) and it is OK. Had the 750 been available when I started I would of chosen it.
Same engine, low end - 100HP , for both designs with the 750 being able to carry 150HP engines. More room and higher Gross Weight.
I like my 701 but the Gross Weight doesn't allow for much luggage if you carry a passenger and the baggage area is small also. It is the most STOL of the 2 designs but at what cost ???
Go with the 750, you won't regret it !
Thanks a lot, the messages from everyone are very consistent. Do you like the Rotax 912?
I can completely agree with Doug MacDonald's comments. At Can-Zac we build 3 CH750's in the time & effort it takes to build a single CH701. The CNC kit is just that good (and fun) to build. CH750 build is approx. 6 weeks (300 hrs).
Do not put instruments in dash or paint on the fuselage as a method of saving building costs...."BUT" invest in a real engine unless you place low value on your life. The engine is the last place to try to save money, and your resale value will reflect this. Unless your flying floats, the Rotax 912ULS (carb engine) is the perfect balance of weight to horsepower for the CH750 airframe. If flying floats the 0-320 150 hp is required.
My buddy Big Dave at 6 ft-7" 280 lbs fit in my CH750 version 1 cockpit without any of the new cabin roof modifications. So Big Dave & Ballast Bob (220 lbs) + 30 gal US fuel and the ROTAX 912ULS CH750 still hauls 800+ fpm climb.
I am 6'4" , most of it legs, and when I went to the factory In MO. I did not even consider riding in the 701 after I looked at it, I don't think I could get in it, even the 750 was a bit on the cramped side for my legs. When I bought my 750 and got it home I built a riser for my seat and set it back about 3" and up 2" where the original seat pan could mount on top, my head does not hit the roof and my legs are very comfortable, made a big difference, like going from coach to first class.
Bob and Randy,
Thanks to you both.
Bob, I agree on the engine side, power and reliability are everything. The President of our EAA Chapter is looking at the Viking for his Kitfox project which is based on the Honda Fit liquid cooled in-line four. Having worked with Honda and owned several of their motorcycles, mowers, gensets, etc. they consider themselves primarily engine makers and I'm sure the Viking will prove itself well, they also show a demo on the CH 750 on their web site. That said, the Rotax is the gold standard without question and with all the kit prep and build experience for a first time builder it is the logical choice. Paint won't be crazy (I'm a conservative guy) and would do it myself as I have on cars built before and some airplanes for friends. Avionics will be basic, my interest is turns around the patch, VFR flight in the extended area and up to my cabin in northern lower Michigan and points between with maybe an Oshkosh trip via the UP. Really glad to hear about the performance with you and your pal, both big guys, and the fuel, that is impressive!
Randy, thanks for that tip, I was surmising I would likely do some mods even beyond the adjustable seat. I have done similar things in cars before for the same reason. It would be horrible to love an airplane you can't get comfortable in!
Again, thanks to all for sharing your experience with me. I am anxious to get started, prepping half the garage now before the holidays and will order up the CH750 plans to study while doing so (the engineer in me!).
Another alternative engine for the 750 is the Jabiru 3300, with which I now have about 200 hrs experience. As I recall at the time I purchased mine a couple of years ago, the Jab seemed a little less expensive than the Rotax when the total cost (engine and FWF kit) was considered.
It's a true aircraft engine with 120 hp, air-cooled, 6 cylinders and a single Bing carb. Pretty much a dirt-simple aircraft engine. The Bing is altitude compensating, so no mixture to fool with and no complicated fuel system or electronics to rely on. Great for those adhering to the KISS principle!
Jab's have had a reputation for cooling and reliability problems in the past, but they've undergone continuous product improvement and new engines after serial #2331 are really an apples-to-oranges comparison to older engines ... they're quite different from earlier engines - much improved and easier to cool, etc. Since the 750 is a high drag, low speed airplane, it definitely takes some experimentation and tweaking to get the oil and air cooling dialed-in, but my experience has been a very reliable, easy to maintain engine that is exceptionally smooth and nothing sounds better!
The Viking shows promise and the cliche is that the Rotax is "bulletproof." However, it's been my observation (my hangarmate has a 912 in his RANS Coyote II) it requires a lot more maintenance relative to the Jab. Also this post on Rotax radiatiors seems to shoot-down the "bulletproof" argument.
The bottom line is that all engines have their good and bad points, their supporters and detractors. (I was biased to the Jab because I'm only about 30 minutes east of Shelbyville, TN, the home of Jabiru USA, so I can literally drop-in for advice or parts.) Define your "mission" for your plane, consider the alternatives, the costs including FWF kits, availabilty of parts and service, consider the amount and depth of mechanical maintenance on the engine that you're willing to perform and you'll find which engine "fits the bill!" (pun intended!)
Thanks very much. You are the first person I have come in contact with yet that has a Jabiru. I have seen their ads and vowed to dig further but haven't yet. The world seems to beating a path to the Rotax door and that is likely one reason they are generally more expensive. I believe you are quite correct, all engines have their strong and weak points to include the stalwarts from Continental, Lycoming and even P&W that I have had experience with in the "big iron". They all need and crave maintenance, maintenance and maintenance coupled with care and respect or they all can be turned into raft anchors or money pits or both!
What kind of fuel burn have you experienced in your 750 with the Jab and what fuel are you burning?
I have time and intend to do my homework but I do agree with Bob McDonald that the engine is not the place to skimp. Life is short, no point in making it shorter!
I burn about 6 gph with the Jab 3300, but I routinely cruise at 2900 rpm. If I rejetted the Bing, I could probably cruise at a lower rpm and get about 5 gph, but of course would go slower. I "think," however, the Jab likes a "fast cruise" since it is an air-cooled engine in a high drag airframe. My CHT's and EGT's are great at 2900, so I haven't had much impetus to tinker with it.
I run 93 octane, unleaded/no-ethanol auto gas (bought 200+ gal the other day for $3.86 vs $5.55 for 100LL). I initially ran 100LL as that's what I had in my storage tank on my airstrip, but since the autogas is approved by Jabiru, I switched and can't tell one bit of difference as far as engine performance. The unleaded does keep the engine cleaner! Jabiru actually also allows 93 oct. with ethanol, but recommends the Bing be overhauled every 2 years. However, I just as soon not use the ethanol if at all possible since I do store the fuel at the strip.
There are several active members of the forum with Jab 3300/750's, and Zenith had one in their demo 750. Most experience high CHT's initially, but this usually resolves with break-in and some cooling tweaks. Like I said, I believe the later model engines are easier to dial-in.
The Rotax shines in comparison because of the liquid cooling - I've never heard of cooling issues with Rotax. However, there's no such thing as a free lunch, and you pay for the easy cooling with the increased complexity and increased number of potential failure points, thus requiring more maintenance, mandatory hose change-outs, etc.
To be fair to Jabiru, however, any air-cooled engine is going to require some tweaking of the airflow/cowl pressure differential to get it right.
To each his own!
Thanks. You've given me a bunch to think about, just went on the Jabiru web site. The vagaries of air cooling and the two extra cylinders might account for the slightly higher burn.
Did the cooling issues get solved by both engine design changes and the Cowling/baffles as specified? Were the issues primarily in their airframes? I presume you have the Shroud for cabin heat. Does it stay comfortable in the winter in Tennessee, I will fly in Michigan!? Your point on the cooling system maintenance is a significant one.
Sorry for all the questions, sucking up information like a sponge!