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Thread: Build time/difficulty--Sonex, RV-7, CH 601. What separates 'em?

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    Red face Build time/difficulty--Sonex, RV-7, CH 601. What separates 'em?

    Okay, here's a basic question from someone who knows very little about metal acft construction.

    - It's very difficult to quantify the differences between the time/effort needed to build particular aircraft from kits. The hours published by manufacturers are very "squishy" (as they usually admit). But, at the risk of quantifying the unquantifiable, my perception is that these three acft would rate about like this (higher number = more time/difficulty). All from the "standard" kit:

    RV-7A: 8
    CH 601HD: 5
    Sonex: 4

    First--I'd very much like feedback on this assessment. Am I way off? Will an RV-7 take twice as many hours as a Sonex? It just seems that folks accept that it takes most builders 2-4+ years to finish an RV-7, and that builders are getting their Sonex's up in the air in much less time.

    Second--why the differences? By most gross measures the planes don't differ that much.

    Wing area: RV-7a = 121sft, CH 601HD = 130sft, Sonex = 98sft
    Length: RV-7a = 20'4", CH 601HD = 19' 0", Sonex = 18' 1"
    Empty weight: RV-7a = 1100 lbs, CH601HD = 590 lbs, Sonex = 620 lbs
    (RV-7a: subtract 150 lbs for heavier engine/prop/tires/wheels/brakes/canopy/etc (folks aren't building those things) = RV-7A metal airframe within 35% of weight of Sonex)

    Maybe the difference is in the complexity of the structure? The CH 601 doesn't have flaps, so that surely reduces build time somewhat. But the Sonex has all the same components as a RV-7, just 35% smaller. And the installation of instruments, upholstery, etc is going to require the same amount of time for all these planes, given similar levels of finish. And maybe "similar levels of finish" is part of the answer: The Sonex's are flying with basic VFR instruments and the RV-7s have this plus full glass and autopilot.

    I've heard good things about customer support from all these companies, and the kits are reportedly well put together (many of the parts have matched-hole construction, etc) and the instructions are relatively clear. It's not like an RV builder is working from a single faded blueprint written in French while the Sonex guys put on virtual reality goggles that lead them through every step--I get the impression that the information is equally clear in all cases.

    So, I'd welcome any:
    - Input on my wag regarding relative difficulty/time required for these kits?
    - Basic explanations for the time differences?
    -- Pulled vs solid rivets?
    -- "designed for easy building" vs "designed for most refined finished product"?

    Thanks in advance.
    Last edited by Vigilant1; January 25th, 2011 at 11:50 PM.

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    Re: Build time/difficulty--Sonex, RV-7, CH 601. What separates 'em?

    I can't address these designs. I can give general comments. The devil really is in the details. This is a great website:
    Lancair IV-P (Kit #600) N144RT Builder Log

    for getting some feel for it. While you certainly spend some more work on riveting and the like, most of the work is in iffy details, like the canopy, cables or other subsystems. Sticking to the standard plans (especially from the well established designs you mention) saves a lot of time. Gauge size is barely a factor up to a certain limit (many 4-seaters need an extra hand), but a Cri-Cri is just as much work as a scratch-build RV would be.

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    Re: Build time/difficulty--Sonex, RV-7, CH 601. What separates 'em?

    Quote Originally Posted by autoreply View Post
    a Cri-Cri is just as much work as a scratch-build RV would be.
    I can't imagine where anyone would get a crazy idea like that

    Having a kit available that is pre-punched (or pre-drilled) can speed things up a huge amount if its manufactured properly (so the holes DO line up). I don't think a larger wing area changes things much but the rib count and number of smaller parts to make a structure certainly do. A larger simpler wing will assemble much faster than a smaller one with higher parts count.

    My WAG would be that each of these aircraft would take a similar amount of time. I have found that once you get into it the time taken can take a backseat to actually enjoying the build progress. I would recommend that you do you homework well and build the plane you like the best (looks included)

    Shannon.
    Building CriCri #706

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    Registered User rheuschele's Avatar
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    Re: Build time/difficulty--Sonex, RV-7, CH 601. What separates 'em?

    I agree, it would be very hard to answer these difference without building all three. However you also have to look at differences in final expectations. The RV7 is designed to go 180-200 mph while the 601 and Sonex are designed to be an LSA and only go 138 mph. This is going to add more structure supports and ways to fasten them. It's also my understanding that the RV uses solid rivets that are either hammered into place or uses a rivet squeezer, while the 601 uses pulled rivets. In many cases that's the difference between 1 or 2 people. The RV and the 601 where designed to use a few different engines, while the Sonex was designed around a VW engine. Frankly, if I was 5'6 and 150lbs and my wife even smaller, I would build a Sonex for my first plane. But I'm not, and I've dry fitted a Sonex and it is just too small for me.
    Ron

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    Re: Build time/difficulty--Sonex, RV-7, CH 601. What separates 'em?

    Thanks to all for the opinions and input so far. I'll need to get out there and lay eyes on some kits and plans to get a more solid idea of the relative work involved with each of these designs. Unfortunately, I'm sure much of the things that slow the process down become most apparent only once construction has begun.

    Quote Originally Posted by rheuschele View Post
    Frankly, if I was 5'6 and 150lbs and my wife even smaller, I would build a Sonex for my first plane. But I'm not, and I've dry fitted a Sonex and it is just too small for me.
    Ron
    This is what I consistently read about this airframe. Everybody loves them, but the small size is a dealbreaker. I know about the "Monnett Philosophy," but there's a point where, maybe, "philosophy" verges into "dogma." Would adding a couple inches to the width of this airframe ruin it? Would raising the canopy an inch cause lighting bolts to rain on the Sonex headquarters? Yes, the plane will fly 5 knots slower. I'll bet it would add less than 25 lbs to the empty weight.
    Anyway, my DW and I will need to sit in a Sonex (and probably a CH601HD) to see how we fit.

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    Re: Build time/difficulty--Sonex, RV-7, CH 601. What separates 'em?

    With equal building skill I bet the RV7 would be faster to build. I have seen a lot of RVs go together and they have true step by step instructions. I say even though it is a more complicated airplane, it is though out so your mom can build it and I am not joking. There is also the army of other builders that can help you too. The Sonex in reality is a much smaller airplane; same size as the RV3 one seater.

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    Re: Build time/difficulty--Sonex, RV-7, CH 601. What separates 'em?

    My first thought (before I saw it mentioned at the bottom of your post): Pop rivets. Gotta save so much time.

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    Re: Build time/difficulty--Sonex, RV-7, CH 601. What separates 'em?

    Quote Originally Posted by rheuschele View Post
    I agree, it would be very hard to answer these difference without building all three. However you also have to look at differences in final expectations. The RV7 is designed to go 180-200 mph while the 601 and Sonex are designed to be an LSA and only go 138 mph. This is going to add more structure supports and ways to fasten them. It's also my understanding that the RV uses solid rivets that are either hammered into place or uses a rivet squeezer, while the 601 uses pulled rivets. In many cases that's the difference between 1 or 2 people. The RV and the 601 where designed to use a few different engines, while the Sonex was designed around a VW engine. Frankly, if I was 5'6 and 150lbs and my wife even smaller, I would build a Sonex for my first plane. But I'm not, and I've dry fitted a Sonex and it is just too small for me.
    Ron
    The Sonex can do much more than 138 mph. They comply with the LSA rule if you are a sport pilot and are bound by that rule. However if you have a PPL and so choose, you can go faster than the LSA speed limit in a Sonex. When I went to the Sonex plant for their workshop last year,after the demonstration flight, I overheard Jeremy Monet commenting to someone on how on his last pass over the crowd, he was doing 180, and this was with the VW Engined powered unit. The Sonex is also designed to accept the 6 cylinder Jabiru engines.

    I also tried on a Sonex and I will agree with you on the fact that they are small. I'm 6' and 235lbs and it was not a horribly tight fit but it was a tight fit nonetheless. I doubt I'd be able to comfortably take myself and a passenger in a Sonex. But, I'd build a Sonex before I'd build an RV(due to cost), and I won't even consider a Zenith aircraft, not after their last fiasco with wings coming off in flight. They're tarnished goods in my book. I don't care that they may have fixed the problems.

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    Re: Build time/difficulty--Sonex, RV-7, CH 601. What separates 'em?

    Sonex VNE is 197 mph. I've had mine to 190 in a dive. Sonex :: 190 mph video by radfordc - Photobucket

    My buddy took his to over 200.

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    Re: Build time/difficulty--Sonex, RV-7, CH 601. What separates 'em?

    I remember, before LSA, that the Sonex advertised such numbers. But after, everyones numbers dropped to qualify. I'm building mine from plans (scratch), however if I was looking for a kit type, (not a sonex because of my size,5'10, 200) I would also look into the older Zodiac kits. They are still on the website for $12-13g and advertise some match holed design. Again, there is no reason that you couldn't be flying for $25g with a corvair engine, and basic instruments. You might even consider swapping most instruments for a Dynon. Compare the cost of a Dynon with buying all the instruments that it replaces. Also compare the weight.
    If you are considering re-engineering a Sonex, you might just want to look at the Zodiac 601HD. Just my opinion
    Ron

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    Re: Build time/difficulty--Sonex, RV-7, CH 601. What separates 'em?

    Quote Originally Posted by rheuschele View Post
    If you are considering re-engineering a Sonex, you might just want to look at the Zodiac 601HD. Just my opinion
    Ron
    Ron,
    That's exactly where I'm at. It deserves a new thread (coming), but I've narrowed things down to a RV-7, a Sonex, or a CH 601 HD. The 601HD offers good value, I'm glad Zenair is still offering the kit (it was supposed to be phased out in favor of the CH 650B). Apparently the HDS wing kits aren't being sold anymore, but I'm sure one could get plans.

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    Re: Build time/difficulty--Sonex, RV-7, CH 601. What separates 'em?


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    Re: Build time/difficulty--Sonex, RV-7, CH 601. What separates 'em?

    Quote Originally Posted by Vigilant1 View Post
    Ron,
    That's exactly where I'm at. It deserves a new thread (coming), but I've narrowed things down to a RV-7, a Sonex, or a CH 601 HD. The 601HD offers good value, I'm glad Zenair is still offering the kit (it was supposed to be phased out in favor of the CH 650B). Apparently the HDS wing kits aren't being sold anymore, but I'm sure one could get plans.
    At the time of this posting, there is a 601 HDS like 85% complete with a 100HP Corvair powerplant for less than $20k on Barnstormers.com. It probably won't be there for much longer.

    BARNSTORMERS.COM
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    Re: Build time/difficulty--Sonex, RV-7, CH 601. What separates 'em?

    I have a unique perspective on this one as I have built the tail and wings for an RV-9A before selling due to overall cost, am building a Sonex/Aerovee which is nearing completion, and have watched my father build a 601XL and now a CH750. I can tell you absolutely that all three are fantastic kits with excellent support from the factories and the communities. The differences are indeed significant though.

    * The best "kit" going is the RV without question. Fully matched hole alclad aluminum with only the best in terms of bearings/assemblies/weldments etc. but it WILL cost you. Slapping everything together right out of the box is very nice, but there are a LOT more parts than a Sonex and solid rivets do take quite a bit more time. In real hours out there, most builders are logging in the mid-1000 to 2200ish hours for a standard build kit and, even going cheap, are usually well north of the $40k mark when done.

    * The best plan set and value for dollar is absolutely the Sonex. Having just about finished building a Sonex at about 800 hours I would expect the finished product to come in just shy of 1000 hours and between $27K to $30K. That is with a brand new AeroVee and fairly well stocked panel. Both of these numbers can be cut down with a strict adherence to the plans and cheaper avionics. I can tell you that compared to the other two, the Sonex is a TANK in its construction! Everything on it is over engineered and over the top in it's strength. The parts are generally crude compared to the other two and every effort is made to cut costs and keep it simple a-la John Monnett. Some times it can be a bit too much (like using bushings instead of bearings) but for the most part it is appreciated by this builder. Also, you can build the entire plane (or only the easy parts) from the plans if you wanted to get airborne for the price of a Yugo!

    * The Zenith kit is really nice and refined, however I was always a little concerned about the overall strength of the materials used in it's construction. The wing spars were like paper compared to the Sonex and, like the RV are only bolted to the fuselage (the Sonex spars overlap each other inside the fuse and bolt together to form a single spar). The plans were quite good, but given the recent folding wings that came standard due to a refusal to counterweight the ailerons and an overuse of lightweight materials, I would avoid them right now. The 701/750 is a completely different animal and is VERY nice, but totally different in mission and not what you seem to want so I will leave that alone.

    As for your other questions... pulled rivets are by far easier to pick up and felt like cheating after working on the RV, but solid rivets are not complicated and are pretty quickly mastered. They are, however, harder to drill out and will more likely cause you to enlarge the hole when doing so as opposed to the pulled rivet. Pulled rivets obviously are uglier and dirtier to the airstream and will be more likely to allow moisture in, but are a HUGE time saver...the final trade off is cost. Pulled rivets cost quite a bit more than solid rivets for obvious reasons.

    Difficulty... all three present their own challenges, sealing the wing tanks on an RV, assembling the spar on a Sonex, trying to escape the Zenith in freefall (just kidding). That is a tough one, but the Sonex WILL be the quickest standard kit to assemble, followed by the Zenith then the RV although the RV will pretty much be guaranteed straight with the matched hole construction.

    I hope that helps and feel free to contact me if you have any other questions!

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    Re: Build time/difficulty--Sonex, RV-7, CH 601. What separates 'em?

    Quote Originally Posted by Cruiser565 View Post

    * The Zenith kit is really nice and refined, however I was always a little concerned about the overall strength of the materials used in it's construction. The wing spars were like paper compared to the Sonex and, like the RV are only bolted to the fuselage (the Sonex spars overlap each other inside the fuse and bolt together to form a single spar).
    You're comparing strut braced wings with cantilever wings here - apples and oranges. The whole point of using strut braced wings is make a lighter wing spar. You can be assured that the designer had at least an inkling of what he was doing with these designs and it's not a relevant comparison.
    "Aeronautical engineering is highly educated guessing, worked out to five decimal places. Fred Lindsley, Airspeed."

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