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What to build, 701 or 750 STOL?
Dear builders,
I'm thinking of building another airplane and I'm looking for advice.
I want to have the best STOL performance possible.
My first build, a 701/912uls [450kg mtow] is still flying fine after 13 years and 500 hours. I'd like it to have the latest upgrades though, such as the 500kg mtow, the engine ring mount, new struts, new flap lever, beanie roof and a header tank and new avionics. It might be easier to build a whole new airplane than do all those modifications.
At first glance the 750 STOL seemed to be the one to build, but looking through the forum I'm not sure that it will perform as well as the 701 with the Rotax 912uls engine fitted. My 701 leaps off the ground, cruises at 90mph at 5000 rpm and lands short too.
In a head to head competition with 912uls engine, just pilot on board and half tanks say, which airplane do you think will perform better the 701 or the 750 STOL?
All advice appreciated.
Shay.
Replies to This Discussion
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Permalink Reply by Ari Hulkkonen on
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Apart from the ring mount, which is an improvement but not really needed + the new avionics (why to do that?) the other mods are just a few tens or maybe hundreds of hours. This year the flap lever, the next year the beanie and so on.. I did that and in about a few years we have it all :)
However, the 450kg --> 500kg mod is a different story, I did some research and discussed with the authorities here and it's a big deal. The mods on the airframe could be done e.g. the new landing gear + reinforced tail + cabin rear parts but you need to build new wings. Then, to get the permission, you need to get the complete list of modifications and get the plans approved. Is this available from the kit manufacturer or the designer? If not, you need to do a lot of mathwork to prove it.. So maybe easier to build a new airframe... On the other hand, in EU, the MTOW for UL-planes is 450kg for land and 495kg for sea planes. 500kg won't help you much. I do not know about Canada or the States.
Then about 701 vs 750. 750 is bigger and probably better but heavier too. if you're going for floats you can ask for builder's experience about the the 750 on floats in this forum. How well it performs? I know based on personal experience that the 701 is light and you have plenty of reserves. I can also tell the 701 carries loads well over 250kg on floats, but of course that's above the legal limit here so we cannot use this capability.
The only thing I wish the 701 was a bit faster... Other than that, it's close to perfection as a small bush plane. I'm sure the 750 is too.
BR, Ari
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Permalink Reply by kenneth capenter on
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Built a 750 four years ago and happy with it. I have a O-200 engine and cruise about 2400 rpm at about 80. It will do the 90 if I use more throttle but usually just up messing around . haven't made any trips in it. uses bout 5.5 gallon/hr. Gets off in 200-300 feet and lands in that distance or less if i pushed the issue. Have 260 hours and just had to replace the bungee on nose gear. Sure is nice the have all the extra space compared to the 701. I think 750 is slightly heavier than 701. I'm 6'4". That influences my opinion about the space. I would build the Cruiser if I had it to do over. It was not designed when I did the 750. I am not into landing in little fields though I operate from a 1800' grass strip easily. I think the Cruiser will do better on cruise speed and still has the interior space.
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Permalink Reply by Brian Unruh on
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I agree, unless you decide to go with a larger engine, performance is gonna drop with the 750.
I have been flying my 701 7 years now with a 912 ul 80 hp mostly at sea level and its performance is terrific! I loved building and am currently working on an RV-6. I will never sell my 701 I just love it. If I was going to build another Zenith though I'd go with a 750. It looks like all upgrades are part of the kit and where Zenith is putting all its research and development efforts into. It would depend if your selling your 701 or if you're going to use parts/engine from your current one towards your new build. Either way you'll need input from 750 fliers to decide. Good luck either way.
Brian
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Permalink Reply by Jonathan Porter on
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Hi Shay,
The 701 is a real performer.... and if you look at the same power on a different weight (ie 750) you will see a difference in performance. That is something that those pesky laws of physics have tethered us with. However, it is not a simple comparison... The 750 is a much roomier machine, with a different handling. If you put more horses in it (as you can) you can balance some of the variations out - however, for comfort (sliding seats, not sitting hip to hip with the passenger, etc) speed of build, baggage capacity (in both litres and kilos) and STILL have ability to use the shorter runways, as well as residual value, visibility (the 750 STOL has brilliant visibility), the the CH750 is really a winner...
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Permalink Reply by Wayne Woloshin on
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Hi Shay, You could do all the Mods and end up with a CH701 and in a short time that will do everything you have come to expect and desire. That being said the CH701 is by far the Best of The Best for STOL and BANG FOR YOUR BUCK HANDS DOWN. IF You want the best of STOL not even the CH750 no matter how configured and powered can match the Ch701 with all the mods and enhancements and a Rotax 100HP for Fuel Economy and Performance,on Wheels or Floats.Tks Wayne
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Permalink Reply by Chuck Kyle on
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Hello Shay,
I am currently biilding a 701 (85% done, 85% to go) and very much enjoy the build. As you probably know, the 701 uses pre-drilled holes to position parts for drilling to final size. My understanding is that the 750 holes are almost all match drilled so all you do is cleco parts together for assembly; no additional drilling is needed. After drilling the first few thousand 701 holes, match drilled assembly became very appealing.
As a really crude engineering guess, I would say that the 701 at 500 kilos should outperform the 750 at 600 kilos assuming similar power, say 100 horsepower. But my understanding of the 750 is that it is still a good STOL airplane, and doesn't yield much to the 701.
Finally, if you are going to keep the 701, you mght find the 750 Cruzer fun. You'd still have a STOL aircraft and a new rocket in the Cruzer...
Best of luck with your decision and fly safe!
Chuck Kyle
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Permalink Reply by J. Davis on
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Built and flew a 701/912UL in the late 90's for about 300 hours. Loved it. Now got about 150 hours on my CH750 with a Jabiru 3300 (120hp) engine. LOVE it. Unless you're on a budget, my vote is the 750.
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Permalink Reply by Normand Lambert on
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Hi Shay,
For pure STOL performance the CH701 hands down ! But, if like me (6foot2) you need the CH750 BAD !
Same power, the CH750 is HEAVIER so STOL performance is adversely affected (CH701 wins) but since
you can upgrade the engine package, the CH750 might be a better choice. Both are STOL designs but for same power the lighter machine always wins. I would say top speed pretty much the same (same wing ribs/design) BUT the CH750 is roomier and can lift more weight (2 persons, luggage, more fuel)...
Construction techniques for the CH750 are better, for example rear wing spar 2 parts instead of 5, thicker material...
How STOL does your machine need to be ???
Anyway, have FUN with your build ...Whatever is will be !!!
Regards,
Norm
CH701, CH701SP, CH750
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I'm 188cm (got only two feet and elbows, no idea about those units ;)) and have no trouble with the leg room with the 701. Sure it could be better but you can live with it.
I've flown many UL aircrafts and there is not such a big difference in the leg room. However, the cabin width is an issue, though, if flying with another big guy.. Most modern designs are maybe 20cm wider than the 701. With the beanie mod you can raise the seats about 5cm even if you tall, which gives much more leg room but the width is still an issue. Bubble doors will give some extra room but that's only a partial solution.
I'm sure both the 701 and 750 are a great choice!
However, they fall into different aircraft category and should not be compared directly. For example, in the EU the 701 can be flown with the national ultralight pilot's license but the 750 requires PPL or LAPL. At least for now.... There's a process on-going to raise the MTOW of UL-planes up to 600kg to meet the current demand and real-life situation. If that happened I'm sure the 750 would become much much more interesting choice for European ultra/microlight pilots too.
BR, Ari
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Permalink Reply by Shay King on
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Many thanks guys for your considered replies.
I will have to get a demo. flight in a 750 before making the final decision.
I'm not that big and my strip is quite short, so at the moment I'm leaning towards another 701.
I'm glad to see that ZAC still have an interest in the 701 with the new wing struts and new flap lever. Hopefully they might produce a new raised [beanie] roof mod. for it too.
Thanks for the advice,
Safe flying,
Shay.
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Hi, we can offer you a demo flight, we hope from April onwards, all things being equal.... http://metalseagulls.co.uk/
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