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echristley(at)att.net
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 Posted: Tue May 20, 2014 9:18 am Post subject: New prospective builder |
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Hi, everyone. My name is Ernest Christley, and I like to build airplanes. Thank you for inviting me here to this meeting of ABA (Airplane Builders Anonymous).
I spent way to long building a Dyke Delta. I got it to the point of fast taxi, but for a host of reasons, I'll never fly it. I'm now looking for something cheap that fits into the LSA regime with a decent cruise and easy flying characteristics and doesn't take forever to build. The 650 with a corvair on the nose looks like it wins on all fronts.
I'm trying to get up to speed on the design, without asking a lot of redundant questions, or reading 100 megabytes of txt from previous posts (most of which will be irrelevant at this point). Does the list or someone else carry a FAQ that will get me jump started on the peculiarities and history of the design?
There is one question that I really can't find the answer to. The bulging shape of the fuselage in the wing root area interrupts airflow and causes the plane to loose significant performance. Several builders have resorted to designing and building wing root fairings and recorded the increased performance (higher cruise, lower stall). It was stated by one builder that this design detail is a well known principle that any mediocre aviation engineer should be aware of. My question is, "Why are kits still being sold with such an obvious design flaw? Why are wing root fairings not part of the kit?" I understand manufacturing inertia and all that, but the 650B was a new design. Could straightening the cockpit sides have been that much of a design change?
[quote][b]
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echristley(at)att.net
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| Posted: Tue May 20, 2014 11:17 am Post subject: New prospective builder |
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Thank you, Steve. I agree that it isn't designed for high performance, but that isn't an excuse for pointlessly sloppy design, now is it? Pulling the bulge in isn't the only answer. Expanding the firewall and baggage area is an equally acceptable solution. As I understand it, the requirement is simply that the fuselage be of constant width in the area of the wing. Throwing away even 1kt for such a seemingly small change seems a little counterintuitive. We don't stick our radiators out in the wind like was done in the 20s, and then say, "It's not supposed to be high performance!", do we? No, because we all know better.
FWIW, the information I had that raised the question in my mind is located at http://www.utdallas.edu/~klaus/Airplane/hidden_drag.pdf
The author indicates an 8kt reduction in stall speed for one test scenario, and a 5kts increase in cruise speed for another scenario. I can't vouch for your good friend for Mr. Klaus, but the data he has published does beg for questions.
On Tuesday, May 20, 2014 1:43 PM, Steve Freeman (SDS) <steve.freeman(at)syntaxds.com> wrote:
Here is the thing,The 650/601 (any version, XL/HD/HDS) is not meant to be a high performance airplane. If that is what you want, build and RV6, 7 or 8. I have a good friend who added the faring you mention and they allowed for marginal improvement that becomes imperceptible if there is any kind of wind.The “bulge” in the fuselage allows for a wider cabin that allows for much more comfortable seating for two people. There is a tradeoff here for the little bit of performance that might be achieved by slimming the fuselage. For me, for the 1 to 4 knots (you might gain in zero wind) I will opt for a more comfortable cabin.The 650 was not design for speed. The BIG, FAT wing will prevent any serious speed performance more than anything else.If you are looking for an airplane that is going to perform better than a consistent 125mph you need to look for a different plane. The 650 is not for you no matter what you do to shave a knot here and there.Steve
[quote][b]
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steve.freeman(at)syntaxds
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| Posted: Tue May 20, 2014 12:03 pm Post subject: New prospective builder |
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<< Expanding the firewall and baggage area is an equally acceptable solution. >>
Maybe, but this falls in to the much easier said than done category. Even minor changes to the airframe result in huge expansions to build time. I suppose making such a change at the design level would negate that reality but for what? Additionally, I think what you suggest would be fugly and you have zero proof it would provide your desired result.Â
<< Throwing away even 1kt for such a seemingly small change seems a little counterintuitive>>
Please – in this airplane…and in the LSA category. There are far bigger fish to fry. You are going to make many decisions as you build that will impact the airplane’s performance far more than this. Build it straight, build it true and build it light. There is your 5 knots.
 << The author indicates an 8kt reduction>>
OK – if he says so. Is that on a Standard Day at sea level in a zero wind condition?
<<5kts increase in cruise speed for another scenario.>>
Well… I have included Don in this conversation. I think he will attest to not getting a 5 knot increase in cruise or 8 knot reduction in stall. And, if I remember correctly he used Klaus’ design as his model. I have never personally piloted Don’s airplane as PIC but I have ridden shotgun many times and I did help build the fairings. With that said, he would be the best resource to discuss this. I think Don (please correct and forgive me if I am wrong) found the best boost to performance he received was by installing vortex generators. He told me the plane flew like a different airplane after installing VG’s. He has never made any such claim (to me) regarding the fuselage fairings, quite the opposite actually. However, they do look really nice!Â
Furthermore, the bulge you mention was far more prevalent in the HD/HDS models with the center wing section than in the XL or 650 model. I do not see this as nearly the issue it was in the past.
If you are that concerned about +/- 5 knots I think you are in the wrong airplane. But if you want to address some of these issues without redesigning the airplane you should take a hard look at the RV-12 which is Van’s answer to a very similar airplane. Have fun squeezing in though if you and passenger are both over 190lbs.
<< but that isn't an excuse for pointlessly sloppy design>>
On this list I think you will find people get a little touchy when you call designer (Chris Heintz) “intentionally sloppy” or insinuate he is somehow less than a “mediocre aviation engineer.”   Unless you are an above average Aviation Engineer you need to be very careful about making those kind of claims. Don’t get me wrong I have my issues with ZAC but I think the airplane itself is very well suited to the defined mission.Â
More than anything you need to remember you are not building the space shuttle. You should not micromanage this decision. If you want a fun to fly sport plane that is comfortable and performs reasonably well the 601 series is a nice plane. If you want something else, I think you need to look at other options. Seriously though, this is not your plane if you are concerned about +/- 5 knots. You will make yourself crazy chasing that unicorn.
Steve
[img]cid:image003.jpg(at)01CF742B.D39B74B0[/img]
From: owner-zenith650-list-server(at)matronics.com [mailto:owner-zenith650-list-server(at)matronics.com] On Behalf Of Ernest Christley
Sent: Tuesday, May 20, 2014 12:17 PM
To: zenith650-list(at)matronics.com
Subject: Re: Zenith650-List: New prospective builder
Thank you, Steve. I agree that it isn't designed for high performance, but that isn't an excuse for pointlessly sloppy design, now is it? Pulling the bulge in isn't the only answer. Expanding the firewall and baggage area is an equally acceptable solution. As I understand it, the requirement is simply that the fuselage be of constant width in the area of the wing. Throwing away even 1kt for such a seemingly small change seems a little counterintuitive. We don't stick our radiators out in the wind like was done in the 20s, and then say, "It's not supposed to be high performance!", do we? No, because we all know better.
FWIW, the information I had that raised the question in my mind is located at http://www.utdallas.edu/~klaus/Airplane/hidden_drag.pdf
The author indicates an 8kt reduction in stall speed for one test scenario, and a 5kts increase in cruise speed for another scenario. I can't vouch for your good friend for Mr. Klaus, but the data he has published does beg for questions.
On Tuesday, May 20, 2014 1:43 PM, Steve Freeman (SDS) <steve.freeman(at)syntaxds.com (steve.freeman(at)syntaxds.com)> wrote:
Here is the thing,
The 650/601 (any version, XL/HD/HDS) is not meant to be a high performance airplane. If that is what you want, build and RV6, 7 or 8. I have a good friend who added the faring you mention and they allowed for marginal improvement that becomes imperceptible if there is any kind of wind.
The “bulge” in the fuselage allows for a wider cabin that allows for much more comfortable seating for two people. There is a tradeoff here for the little bit of performance that might be achieved by slimming the fuselage. For me, for the 1 to 4 knots (you might gain in zero wind) I will opt for a more comfortable cabin.
The 650 was not design for speed. The BIG, FAT wing will prevent any serious speed performance more than anything else.
If you are looking for an airplane that is going to perform better than a consistent 125mph you need to look for a different plane. The 650 is not for you no matter what you do to shave a knot here and there.
Steve
| Quote: | | _-============================================================_-=Â Â Â Â Â Â Â Â Â - The Zenith650-List Email Forum -_-= Use the Matronics List Features Navigator to browse_-= the many List utilities such as List Un/Subscription,_-= Archive Search & Download, 7-Day Browse, Chat, FAQ,_-= Photoshare, and much much more:_-=_-=Â Â --> http://www.matronics.com/Navigator?Zenith650-List |
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echristley(at)att.net
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| Posted: Tue May 20, 2014 1:23 pm Post subject: New prospective builder |
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On Tuesday, May 20, 2014 4:02 PM, Steve Freeman (SDS) <steve.freeman(at)syntaxds.com> wrote:
>> I suppose making such a change at the design level would negate that reality but for what? Additionally, I think what you suggest would be fugly and you have zero proof it would provide your desired result.
The link I provided documented a 16% decrease in stall speed after providing a clear explanation of why it works.
<< Throwing away even 1kt for such a seemingly small change seems a little counterintuitive>>
| Quote: | >You are going to make many decisions as you build that will impact the airplane’s performance far more than this. Build it straight, build it true and build it light. There is your 5 knots.
|
Why not add the wing fairing and get another 5 knots? They are not mutually exclusive.
<< The author indicates an 8kt reduction>>
| Quote: | >OK – if he says so. Is that on a Standard Day at sea level in a zero wind condition?
|
Didn't bother to look at it, huh? If you're not going to look at the proof offered, how can you say there is no proof?
| Quote: | >Furthermore, the bulge you mention was far more prevalent in the HD/HDS models with the center wing section than in the XL or 650 model. I do not see this as nearly the issue it was in the past.
|
Thank you, Steve. That is a VERY useful tidbit. If the bulge has been reduced, it may be an indication that Zenith DID correct the problem. These sort of airflow issues are not linear, so reducing it a little may make it immeasurable.
| Quote: | >If you are that concerned about +/- 5 knots I think you are in the wrong airplane. But if you want to address some of these issues without redesigning the airplane you should take a hard look at the RV-12 which is Van’s answer to a very similar airplane. Have fun squeezing in though if you and passenger are both over 190lbs.
|
What I hear you saying here is that if I'm not going to drink the koolaid, I should go away? Really? The Zodiac designs are perfect airplanes and a person has to buy in completely, no questions asked, or go away? I think you do the Zodiac community a disservice, Mr. Freeman. The RV12 is extremely expensive compared to a 650B, and as you insinuate does not have the shoulder room.
<< but that isn't an excuse for pointlessly sloppy design>>
| Quote: | >On this list I think you will find people get a little touchy when you call designer (Chris Heintz) “intentionally sloppy” or insinuate he is somehow less than a “mediocre aviation engineer.” Unless you are an above average Aviation Engineer you need to be very careful about making those kind of claims. Don’t get me wrong I have my issues with ZAC but I think the airplane itself is very well suited to the defined mission.
|
A quote from the article I linked to: "So, don't expect anything new to be reported here. Any aeronautical engineer is well aware of what I am writing about. But, equally true, the simple facts I will describe have been ignored in some of yesterday's designs and are still being ignored in some of today's designs."
Your defense of Mr. Heintz is endearing, but I'm not into hero worship. I am an engineer, and I'm well aware that many times subtle design decisions are made without being fully cognizant of their ramifications. Sometimes out of ignorance, but more often from expediency. There's a lot of conflicting issues to sort out when designing a complex object like an airplane. Mr Heintz did a good job, else I wouldn't be considering a 650B. Doesn't mean that he shouldn't be second guessed to the best of my ability before I lay out $15,000 of my money for a stack of aluminum. It's all simple physics. Between adults, "Why did you design it that way?" should never be answered with, "Just trust me." (Though, "I had to pick SOMETHING!" is perfectly adequate.)
| Quote: | >More than anything you need to remember you are not building the space shuttle. You should not micromanage this decision. If you want a fun to fly sport plane that is comfortable and performs reasonably well the 601 series is a nice plane. If you want something else, I think you need to look at other options. Seriously though, this is not your plane if you are concerned about +/- 5 knots. You will make yourself crazy chasing that unicorn.
|
Are you taking yourself seriously? The whole experimental community is out chasing 5kts. Isn't that about what you can expect to get for the cost of a set of wheel pants? But I think you've answered my original question. The fuselage has been modified in the 650B to reduce the bulge to the point that the interference drag is all but eliminated, negating the need for significant root fairings.
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steve.freeman(at)syntaxds
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| Posted: Tue May 20, 2014 2:45 pm Post subject: New prospective builder |
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<< Didn't bother to look at it, huh? , >>
I have read this article in the past.
The article you reference is about a different airplane and the results from that article cannot be applied to the 650 airframe. Reading or presenting this now does not add value to this conversation. The 650 and the 601HDS have an entirely different center wing section. Any results obtained on that airframe cannot be applied to the 650.Â
<< how can you say there is no proof?>>
I have no idea if this mod would offer any results on the 650, it might. But no such proof is brought to this conversation in the article you are referencing. That is how, I can say “there is no proof.” At least not in this article.
<< The link I provided documented a 16% decrease in stall speed>>
Talk to Don H about this. Let me know if he concurs. But if you are not building a 601HDS I am not sure there is a point.
<< Why not add the wing fairing and get another 5 knots?>>
Talk to Don…I don’t think he would support this.  And, since he has helped me a lot with my 650 build (I also built an HDS but sold it just prior to first flight) ask him if he thinks this mod would make any sense on the 650 airframe.
<< What I hear you saying here is that if I'm not going to drink the koolaid, I should go away? >>
I didn’t say that at all. I am just telling you there are better areas to focus your energies.
<< I think you do the Zodiac community a disservice, Mr. Freeman. >>
Really? I just (potentially) saved you a lot of time and money. The mod is not easy to do, it takes a great deal of time, the materials are not inexpensive and the results are marginal. AND – the mod isn’t even for this airplane. If you feel I have done you a disservice by pointing this out then, fine. You came to the list for advice and I offered it. If you don’t want to take my advice because you think I have no experience in the matter I am OK with that.
<< The RV12 is extremely expensive compared to the 650NB>>
I looked at the RV-12 when I decided to build again and I don’t remember there being a significant difference in the kit prices. Maybe I am wrong here but it seems like you are just looking for an argument.   When I figured the final price tag (engine, instruments, trim and paint) for the RV-12 it was essentially the exact same.
<< Your defense of Mr. Heintz is endearing, but I'm not into hero worship>>
Is it in your nature to be intentionally abrasive? I do not worship the ground CH walks on and anyone who follows this list will let you know I have been vocal about some ZAC issues. What you say in private is your own business. But to flame the guy in a public forum when you don’t bring equal credentials to the table is a dicey proposition. Especially (especially) when you talk about the virtues of a modification designed for a different airplane. I don’t think I need to add anything to that. It speaks for itself. Have you ever seen a 601HDS and a 601XL (or 650) side by side? They are very different airframes.
<< before I lay out $15,000>>
Back in the Day ZAC sold the Airframe Kits complete. That is no longer the case. Now they have  what they call the Finishing Kit, just like Van’s. You will need the finishing kit unless you have the ability to scratch build the canopy and main landing gear (good luck!), etc. This pushes the kit price much closer to $20k than  $15k.  When you leave out important facts it undermines your credibility.Â
I would not normally take offense at (some of) your comments but if you are going to tell me I offer a disservice to the building community then you are equally obligated to know what you are talking about.
<< The whole experimental community is out chasing 5kts.>>
Chasing 5kts in this airframe is a fool’s errand unless you are doing it purely for the fun of the chase. If that is the case, knock yourself out and have fun.Â
<<Are you taking yourself seriously?>>
I take my building very seriously. I told you what I think you need to do to shave 5 knots. Build straight, build true and build light  (build safe too!)Â
Good luck with your build.
Steve Freeman
CH650B
N902AL
Lycoming 20235-N2C
98% complete.Â
FAA Paperwork is in process. All that is left is finish work, rig the ailerons, W&B and a date with a DAR. I am looking for first flight in the next 60 to 90 days.Â
See you all in Osh Kosh next summer!
From: owner-zenith650-list-server(at)matronics.com [mailto:owner-zenith650-list-server(at)matronics.com] On Behalf Of Ernest Christley
Sent: Tuesday, May 20, 2014 2:23 PM
To: zenith650-list(at)matronics.com
Subject: Re: Zenith650-List: New prospective builder
On Tuesday, May 20, 2014 4:02 PM, Steve Freeman (SDS) <steve.freeman(at)syntaxds.com (steve.freeman(at)syntaxds.com)> wrote:
| Quote: | > I suppose making such a change at the design level would negate that reality but for what? Additionally, I think what you suggest would be fugly and you have zero proof it would provide your desired result.
|
The link I provided documented a 16% decrease in stall speed after providing a clear explanation of why it works.
<< Throwing away even 1kt for such a seemingly small change seems a little counterintuitive>>
| Quote: | >You are going to make many decisions as you build that will impact the airplane’s performance far more than this. Build it straight, build it true and build it light. There is your 5 knots.
|
Why not add the wing fairing and get another 5 knots? They are not mutually exclusive.
<< The author indicates an 8kt reduction>>
| Quote: | >OK – if he says so. Is that on a Standard Day at sea level in a zero wind condition?
|
Didn't bother to look at it, huh? If you're not going to look at the proof offered, how can you say there is no proof?
| Quote: | >Furthermore, the bulge you mention was far more prevalent in the HD/HDS models with the center wing section than in the XL or 650 model. I do not see this as nearly the issue it was in the past.
|
Thank you, Steve. That is a VERY useful tidbit. If the bulge has been reduced, it may be an indication that Zenith DID correct the problem. These sort of airflow issues are not linear, so reducing it a little may make it immeasurable.
| Quote: | >If you are that concerned about +/- 5 knots I think you are in the wrong airplane. But if you want to address some of these issues without redesigning the airplane you should take a hard look at the RV-12 which is Van’s answer to a very similar airplane. Have fun squeezing in though if you and passenger are both over 190lbs.
|
What I hear you saying here is that if I'm not going to drink the koolaid, I should go away? Really? The Zodiac designs are perfect airplanes and a person has to buy in completely, no questions asked, or go away? I think you do the Zodiac community a disservice, Mr. Freeman. The RV12 is extremely expensive compared to a 650B, and as you insinuate does not have the shoulder room.
<< but that isn't an excuse for pointlessly sloppy design>>
| Quote: | >On this list I think you will find people get a little touchy when you call designer (Chris Heintz) “intentionally sloppy” or insinuate he is somehow less than a “mediocre aviation engineer.” Unless you are an above average Aviation Engineer you need to be very careful about making those kind of claims. Don’t get me wrong I have my issues with ZAC but I think the airplane itself is very well suited to the defined mission.
|
A quote from the article I linked to: "So, don't expect anything new to be reported here. Any aeronautical engineer is well aware of what I am writing about. But, equally true, the simple facts I will describe have been ignored in some of yesterday's designs and are still being ignored in some of today's designs."
Your defense of Mr. Heintz is endearing, but I'm not into hero worship. I am an engineer, and I'm well aware that many times subtle design decisions are made without being fully cognizant of their ramifications. Sometimes out of ignorance, but more often from expediency. There's a lot of conflicting issues to sort out when designing a complex object like an airplane. Mr Heintz did a good job, else I wouldn't be considering a 650B. Doesn't mean that he shouldn't be second guessed to the best of my ability before I lay out $15,000 of my money for a stack of aluminum. It's all simple physics. Between adults, "Why did you design it that way?" should never be answered with, "Just trust me." (Though, "I had to pick SOMETHING!" is perfectly adequate.)
| Quote: | >More than anything you need to remember you are not building the space shuttle. You should not micromanage this decision. If you want a fun to fly sport plane that is comfortable and performs reasonably well the 601 series is a nice plane. If you want something else, I think you need to look at other options. Seriously though, this is not your plane if you are concerned about +/- 5 knots. You will make yourself crazy chasing that unicorn.
|
Are you taking yourself seriously? The whole experimental community is out chasing 5kts. Isn't that about what you can expect to get for the cost of a set of wheel pants? But I think you've answered my original question. The fuselage has been modified in the 650B to reduce the bulge to the point that the interference drag is all but eliminated, negating the need for significant root fairings.
| Quote: | | _-============================================================_-=Â Â Â Â Â Â Â Â Â - The Zenith650-List Email Forum -_-= Use the Matronics List Features Navigator to browse_-= the many List utilities such as List Un/Subscription,_-= Archive Search & Download, 7-Day Browse, Chat, FAQ,_-= Photoshare, and much much more:_-=_-=Â Â --> http://www.matronics.com/Navigator?Zenith650-List |
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