Hawkjet?

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HawkJET

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May 18, 2010
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Santa Rosa, CA
Unknown,

If someone calls another person's work unrealistic, "pie in the sky", and ungainly (among other things). How is it that pointing out that those comments are not constructive and insulting is considered attacking?????????

Yes, that is a critique of your project. That's how critiques work.
NO, it is NOT a critique! It is name calling! A critique is constructive.

If you really do think your project is worth it, defend it; explain how it's realistic, and explain how it has a firm grip on reality.
I did. It's all in the 9000 words of the web site that was posted by the OP. If there are any other questions that anyone has after that, I will entertain any and all of them. None of those that are supposedly critiquing the HawkJET have read the site.

How about providing some of the evidence behind all those CAD drawings?
I don't know what you mean by this.

Perhaps some airfoil data, design analysis, etc?
See web site.

Maybe even some information on how you plan to purchase your chosen engine for such an amazingly low price?
I have had conversations with an aircraft salvage company. I didn't know it was an "amazingly" low price.

Not hard to defend your concept if it's worth defending, rather than getting angry and attacking the individual who's simply saying that he doesn't believe what you're doing will work.
As I said, he hasn't read the web site. He is insulting my design. He is not asking any specific questions (he can't because he hasn't read the site). He is not "simply" saying he doesn't believe, he is ridiculing. Who's attacking????
 

HawkJET

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Santa Rosa, CA
Have you been able to purchase an engine yet? How about engineering support? Have you talked to Williams about engineering support with respect to technical details related to installing and operating one of their engines?
I have done preliminary investigations as to the price and where to purchase a salvage engine and have determined it is doable. I don't expect any support from Williams whatsoever. I have discussed engine installation with some mechanics and don't see it as a significant problem.
 

HawkJET

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Santa Rosa, CA
The explicit concerns that have been brought up for this particular project are (a) engine availability, price, and integration and (b) realism of empty weight. The standard concerns for generic jet projects are (c) fuel capacity and associated range and (d) structural analysis with focus on flutter (which is particularly interesting with your forward swept wing).
What concerns about fuel capacity and range? I have a fairly elaborate spreadsheet that includes fuel specifics, etc. Is that what you mean?
When discussing empty weight, it seems that others are shooting from the hip based on some standard or average airframe. This may be considered similar to comparing a Chevy to an indycar. Most people that build airplanes do NOT try to build light. To the contrary, most homebuilts are porkers. Even so, if you consider the weight of a six cylinder with cs prop, it is easily more than the FJ-44. There are a few piston aircraft that are "comparable" to the HawkJET (except for the engine). I used these examples as a place to start in my estimates. Also, I was one of the builders of one of the lightest Vari-ezes flying. There is a mindset it takes to build light. Yes you are correct, it is a low weight, but it should be doable (but it may not be easy).
The forward swept wing is only moderately swept forward. A Mooney wing is similar. In conversations with John Roncz, he comments that a small amount of forward sweep is easily handled structurally - no different than flying in a slip. The Questair Venture wing is similar. But it is thinner and not swept. The Venture wing is quite stiff and has a very high flutter speed. The HawkJET, having a thicker wing will be easier to make stiff. Flutter should not be a problem.

The comments about the web page are more along the lines of it being unclear what analysis has been done to justify the specification claims or design choices. For example, you show a close-up of a wing cuff; but you don't explain why that's the best way to accomplish (presumably) tip stall reduction in this case, nor why you think it's either necessary or sufficient. You also claim that "adhesive bonding methods" will be used instead of riveting, without explaining how you're going to handle the pitfalls in this approach.
I attempted to explain the cuff. If I didn't succeed, what do you think is missing? All wing design involves stall considerations. The cuff is how I chose to tailor the stall. Are you questioning if it will work as planned?

The web site is 9000 words as it is. I don't necessarily know what people want information about. I will be using standard industry bonding methods. Are you asking what that is? What pitfalls are you referring to?

But surely you can see why it's not terribly more exciting - to us, with the information we have - than the dozens of similar projects that have gone nowhere.
Well, really, I don't. This is the first instance of anyone saying my web site is lacking in information. The overwhelming feedback I get is antithetical to your comments. So I am surprised, really.

I don't often run into such doomsayers. The folks I tend to be around are more likely to give everyone the benefit of the doubt. Yes, I am not so naive to say it's easy. But going to the moon wasn't easy. It was however a great accomplishment. Besides, I'd rather try and fail than sit on my couch watching tv while someone else is out flying a jet.
 
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Inverted Vantage

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...But going to the moon wasn't easy. It was however a great accomplishment.
I know this is probably going to throw fuel on the fire, but does a comment like this raise a red flag to anyone else? Not just on your project HawkJET, but on any of them. This one is right there with "well they laughed at the Wright Brothers".

Anyway, that's my two cents. I guess my only comment towards your specific project is just to be careful saying stuff like that, it tends to generate eyebrow raises I think.
 

addaon

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800 lbs fuel... 114 gallons. At 1900 lbs thrust, you'll be sipping 866 lbs/hour at 0.456 lbs/lb*hour (published number; a bit efficient). If you're running at 50%, you'll be getting no better than 0.46 lbs/lb*hour (published 80% number); probably closer to 0.5. So that's 475 lbs/hour. 45 minute reserve is 127 lbs, so you're looking at 85 minutes of 50% cruise w/ reserve, assuming no use of full power. Your 2.9 hours / 3.7 hours of endurance are a big puzzling; 30 gallons/hour is 420 lbs thrust at 0.5 lbs/lb*hour, but efficiency starts to drop dramatically by the time you get to 22% thrust.

Cuffs are relatively uncommon in initial designs (as opposed to as an after-the-fact fix). Wondering why you think that's a better solution that (geometric or aerodynamic) washout, which can have a lower drag penalty. Again, this is just an example of you presenting "solutions", without making it clear what tradeoffs were considered and why they were selected.

Industry standard bonding methods for aluminum, from my (third hand) understanding, are so focused on surface preparation that you end up with effectively a clean room environment. Having worked in a clean room environment before, it doesn't seem particularly amenable to a one-off airplane.
 

HawkJET

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Anyway, that's my two cents.
The sign on the shop wall:

"The difficult we do immediately. The impossible takes a little longer"


There is a mindset to this joke. I appears you don't have it. I have been accomplishing things all my life that the skeptics didn't think I could do. Eventually I learned to ignore them.
 

HawkJET

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Okay, I understand your question about fuel.

I used a fuel specifics chart for the FJ-44. Your synopsis is oversimplified and doesn't include many factors that the chart does. It is possible my calculations are optimistic, but I did spend a lot of time refining the spread sheet.

Cuffs are relatively uncommon in initial designs (as opposed to as an after-the-fact fix).
From my conversations with Jim Grizwold and reading elsewhere, I disagree with this statement.

Industry standard bonding methods for aluminum, from my (third hand) understanding, are so focused on surface preparation that you end up with effectively a clean room environment. Having worked in a clean room environment before, it doesn't seem particularly amenable to a one-off airplane.
You are correct. The surface prep is critical and expensive. Assembly is not as critical except for jigs and fixtures for controlling the glue joint. I have a friend that has built an airplane this way with great success. A clean room is not needed for assembly and the surface prep is durable after completed.

Boeing patented a process in the '70s (I believe) that involves a phosphoric anodize followed by (within 1 hour) an epoxy primer. Once the primer is cured, a clean room environment is no longer needed. I don't think Boeing uses one at that point either.
 

orion

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OK, I've got a few minutes so I'll jump back into the fray for a bit. In looking at this as an experienced configurator and someone that has been in this business for some time, there are several comments I can add to my initial off the cuff evaluation. First off, the general. If we look at the history of this market and specifically that of the private jet sector, we can see that although many have tried to develop something along these lines, none have succeeded to any real degree. A small handful have made it as far as a prototype and fewer yet have managed a small pittance of sales, but even those are hardly enough to be called a success. As such, simply looking at history and the typical approach at the solution, the odds are not in your favor, especially since by your own admission you do not have the resources to turn your idea into reality. That makes you a dreamer (welcome to the group - there's many of us here, and yes, I'm one too) but that's not really a winning resume. True, it's a start but statistics have a way of revealing the truth, especially when combined with a sizable history of various failed approaches. But enough of that, let me get to a few specifics.

You seem dismayed at the doomsayers here - well, personally I'd prefer to listen to one or two doomsayers who have experience in a particular field rather to a room full of people who pat me on the back. You just might learn something from the doomsayers whereas those who espouse good feelings generally have no useful contributions to offer. I'm assuming that none of those who are impressed with your work are throwing money at you, are they?

There is a vast difference between those who are impressed with pretty pictures and those who really understand the technology, the road to success and the market. Just ask anyone who has ever undertaken a market survey of this industry (I've done two) - at first glance some numbers are great and a project's future looks bright but, if you really ask the right questions and look beyond the good intentions, things suddenly turn much grayer.

And this is really where my pie-in-the-sky comment comes from. Anyone can develop pretty pictures and type over 9,000 words at a web site (words that virtually no one is willing to sift through at any level of detail) yet if all this is without a foundation, the idea wont come across. Simply said, if you can't sell your idea in 20 seconds, all the rest of the work will make little difference. Then, couple that with a design that brings up some very basic questions and you really have an uphill battle, especially with those folks who are represented by someone like me who is hired to do a detailed evaluation of your concept.

Those questions will also include subjects regarding your own experience as a designer and project manager and having been through several of these "interviews" myself, I can pretty much assure you that if you don't have just the answer the potential funding partners are looking for, you're again just dreaming.

As far as the airplane is concerned, the brief look I took immediately brought forth a few points worth examining so I'll list them here, in no particular order. First off, the fuel. This will be one of the most basic issues to address and it is one of the most common problems just about every private jet development has had - in short, people try to design a small airplane but in their pursuit of that small plane they forget that if it is to be useful, it needs sufficient fuel to actually go somewhere. Every project I can think of has had to increase the size of their plane at some point in the program in order to simply get more fuel in. But the problem with that is that it is relatively difficult to do so once you tooled up so the investors end up spending a lot of money doing a second time what they should've done right in the first place. And of course this then leads to secondary problems: the increased fuel and larger volume adds weight, which has to be addressed in everything from the flight structure to the landing gear. This too adds weight so often times they have to go to a bigger engine. But then this is thirstier so again they need more volume.... and on and on. How much do you need? I've found a good ballpark to use is defined by the product of the sea level static thrust rating of the engine and the average cruise sfc. For the Williams FJ44-1 at Mach .5 at 28,000 feet the sfc is about .740 (at full throttle). At that altitude the sfc varies a little so even if you plan on cruising faster the number can still be used for this approximation. This means that ideally, your airplane should be able to hold about 1,400 pounds of fuel. Personally in this case I think that might be a bit too high but realistically, I would probably recommend to not go below about 1,200 pounds.

The next issue is your body loft - it looks like a jet version of the Cri-Cri. Simply said, you have a flat belly combined with a very pronounced cockpit and turtle-deck. From an aerodynamic standpoint you have a very low aspect ratio body with a very substantial camber line. I would think you'll have some interesting interplay between the body generated lift and moment, and the flight surfaces' control/trim capabilities.

Staying with the body, the inlets look sizable but assuming they're correct scale-wise to the engine, looking aft it does not seem like you have much provision back there for the engine itself - in other words, the cross section seems rather small to house the engine properly. If I look at your exhaust nozzle geometry and your inlets, I have a hard time imagining how you plan to fit the engine back there - on a turbofan the diameter of the exit cone nozzle is substantially smaller than the fan diameter - if your exit nozzle size is correct, the aft fuselage simply looks too small. Furthermore, given the sizable accessory case hanging below the FJ44 and the cooling air volume it needs, I simply do not see any mechanism in your loft for a proper installation envelope.

Moving to your wing, like it or not, cuffs are either fixes or an up front admission that you are unable to design a proper wing. Even if a few technical papers say otherwise, looking at industry history, all cuff use is to fix a problem and that's simply how they're perceived. The problem with perception though is that all the technical papers you throw at folks will not change their minds and the wing will continue to look like you're fixing something that was not designed right the first time.

And then we come to the tail - it is interesting that with the amount of data and pireps we have out there regarding "V" tails, even with modern designs, the configuration continues to be plagued by issues that make for problematic handling or flight characteristics. Yet despite the evidence, designers still think that they're somehow achieving something with their use. Yes, the plane looks unique and yes, maybe even better, but there's other way to do that without unnecessarily increasing the development risk. But on a personal note, in your case I don't think the tail does a good job blending the aesthetic value of the rest of the plane - it almost looks like a simple afterthought.

Anyway, those are a few basic highlights. I have not read the rest of the web site but quite frankly, given what you present I don't really need to. Like I said, you need to be able to sell the design in 20 seconds. After that, all the extra words can only sink you. But of course that's my opinion - you can use it or ignore it. Prove me wrong - build it and build a company around it. Good luck.
 

HawkJET

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Santa Rosa, CA
Thank you Bill for your civil comments about the HawkJET.

My purpose for joining this forum stemmed from a few posters "dissing" the HawkJET without knowing what they were talking about.

It is a human trait to put down someone or something in an effort to elevate ourselves and look good to others. Everybody does it to one degree or another. I am certainly not immune.

I noticed that the HawkJET and myself were targeted in this basic human behavior and so I stepped in to let people know I didn't appreciate it.

In the process I had the opportunity to learn that there is a lot of misinformation and ignorance in regard to aircraft design. I see an opportunity to broaden the view of these design elements but alas, it is clear that a wider understanding is not desired. It is even abhorred.

I would like to hear reasonable arguments in support of many statements made here as I am eager to understand more about airplanes. Many statements are made as a-matter-of-fact as if no support is needed. However I can easily find references and/or people that contradict these supposed facts (such as your fuel specifics and comments on cuffs and V-tails). I won't do that here and now because it is obvious nobody is listening nor cares.

Bill, you seem to have built yourself a nice little fiefdom here and your words are taken without question. I agree you are knowledgeable and probably right most of the time. But you don't know as much as you think, and you are unwilling to listen to opposing ideas. As I said in a previous post, a track record gives you tunnel vision. I learned from such teachers as Burt Rutan, John Roncz, Jim Grizwold, Roy Lopresti, Jim Lopresti, etc. etc. All these people have been a part of designing, building, testing, and flying a number of successful aircraft. I have broken bread with all of them on several occasions. I am not the fool you think I am.

The exercise of designing an airplane is great for teaching one how little one knew about designing an airplane beforehand. Many comments and concerns voiced here remind me of how little I knew before this exercise (and what I thought I knew). Like them I would ask the kinds of questions they ask. Now I have an understanding that would have me asking completely different questions. Don't get me wrong here, I'm not putting them down - they haven't designed an airplane yet. But you have (at least I think you have). I am a little dismayed by your tunnel vision.

There is so much learned when you jump in and "get your hands dirty up to your elbows". I encourage all that are interested to do it. Likewise, the people I learned about airplanes from, learned this way. They made the mistakes and breakthroughs. AND THEY MADE SUCCESSFUL AIRPLANES! Sorry Bill, their words carry A LOT more weight than yours.

I will bow to your expertise on "pie in the sky" however. A brief perusal of your web site reveals that you have personally been involved in numerous examples. You are clearly expert in identifying them. However, you seem to be as inexperienced as I am when it comes to actually building an airplane. Given your desire and requirement for track records from others before you give them the time of day, I understand why you consider me so inept. It is interesting to notice your reaction when I treat you the way you treat me.

It is clear there is no audience for me here. You are not listening now, and I see nothing to indicate that will change. You are not interested in what I have done with the HawkJET nor why. It is clear the HawkJET and I are merely something for you to put down in an effort to elevate yourself.

Since there are two sides to every story, I am sure that you will likely say that I am doing that with you. Fine. I don't care, just as you don't care (isn't it funny how that works). Others will make their own observations. Mostly though, they will side with you mainly because I am the interloper not you (you see it has nothing to do with reality).

My only hope is that somewhere in the recesses of your mind, you may think twice before "dissing" someone or something because you never know who may be lurking.

I thank Mac790, skeeter, addaon, mike t 12, and others for their genuine interest in the HawkJET and it's design considerations.

Goodbye.

P.S. If any of you are ACTUALLY interested in a different perspective, you can email me through my website. I am happy to answer your questions.
 

PTAirco

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Anyway, those are a few basic highlights. I have not read the rest of the web site but quite frankly, given what you present I don't really need to. Like I said, you need to be able to sell the design in 20 seconds. After that, all the extra words can only sink you. But of course that's my opinion - you can use it or ignore it. Prove me wrong - build it and build a company around it. Good luck.
I really don't care to get embroiled in this, but when it comes to evaluating ("selling") a design in twenty seconds - well, that may apply to products such as air fresheners, dish mops, a ballpoint pen, or perhaps a new type of dog leash - but a jet? I think being able to evaluate a new aircraft design in the first 20 seconds is stretching credulity more than just a little.
 

orion

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I really don't care to get embroiled in this, but when it comes to evaluating ("selling") a design in twenty seconds - well, that may apply to products such as air fresheners, dish mops, a ballpoint pen, or perhaps a new type of dog leash - but a jet? I think being able to evaluate a new aircraft design in the first 20 seconds is stretching credulity more than just a little.
If you're talking a marketing program then you're right however, here we're talking about presenting an idea or concept and "marketing" said concept not to the airplane buying public but more so to a knowledgeable group of individuals who will have a tendency to evaluate said idea at a glance. If the concept makes technical sense then those who have the ability to do so will pretty much judge its potential in a very short period of time. If there's red flags, many can be identified just as fast.

You've been here long enough to know that many ides and concepts presented by the membership are accepted for what they are and generally encouraged or helped if it's feasible to do so. And yes, there is at times blunt criticism also but with only one or two exceptions within the last several years, even that criticism is usually taken for what it is and accepted, often times leading to better designs or more realistic directions.

Two things I learned from those who taught me - One, "never fall too much in love with your idea" because someone will pretty much always come along with something different and/or better, and if you invest yourself too much in your own work you'll end up pretty frustrated and disillusioned. And the second is a corollary to the first: "Learn to love your eraser".
 

orion

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You are clearly expert in identifying them. However, you seem to be as inexperienced as I am when it comes to actually building an airplane.
The statistical nature of this business is pretty poor when it comes to demonstrating flight hardware. Years ago an article (in Kitplanes I think it was) published some rough data that suggested that less than ten percent of "real" airplane ideas (concepts that are slated for a business model and production) ever make it past the conceptual stage and of those, less than ten percent ever make it to a prototype and first flight. I haven't kept real track of this but having been in the "experimental" industry for so many years I'd suggest that even those percentages may be a bit on the optimistic side.

Our web site is not a complete listing of our work and you're right, many of the design programs listed on the gallery page have never made it beyond mockup. Out of the 18 programs pictured, only eight were completed through hardware and flight and of those, only four were complete vehicle programs. Given the time line those represent, the statistics do hold out.

The site also fails to list our current work - we operate on a simple business model (as do our customers) which simply states that we will make no public announcement of any program until that program is well into the hardware stage or nearing first flight. This industry is at times plagued by meaningless hype of new designs and products, the vast majority of which never reach fruition. Most of the airplane buying public seems to be getting pretty tired of the the endless hype and lost investments and like you saw here, takes a very jaundiced view of pretty pictures and somewhat premature advertising.

Of the five currently active programs I have now, two are well into the prototype stage and both should be rolling out by Spring of 2011. One was formally announced at Sun-n-Fun (a bit early I thought but it's well on its way to assembly - www.privateerindustries.com); the other (an Unlimited Class racing plane) is actually a bit further along and should be rolling out by the end of this year.

Regarding jet projects, in the last three or four years I've had four. The smallest was the jet engine integration into a Caproni glider (completed and certified), the most complex (sort of a civilian version of a U-2 type mission profile) is currently nearing completion of the Preliminary Design stage and is slated for the start of the prototype by the end of this year. And we're also assisting with the redesign of the SportJet program in Colorado.

In short, our customers are quite happy with our track record, reputation and our expertise. Is this a guarantee of future work? Of course not - in this business there is no such thing. But we do take a very realistic approach to this business and as you see, are quite leery of certain presentations and/or presentation formats. But then that's what our customers like about us.
 

mcmurphy

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Welcome to the forums Hawkjet. I and many others looked at your design and came to the conclusion that while it looks nice on paper it isn't going to fly (both figuratively and literally).

I questioned how you were going to put all of the needed equipment into an airframe with an empty weight of 1500 lbs. As an example take a look at a small jet that is already in production- the Viper Fanjet. It uses a Pratt & Whitney JT15 turbofan with a dry weight of 516 pounds. Pretty close to your engine weight, if I remember correctly. Empty weight for this aircraft is 3,100 lbs. with a gross weight of 5650 lbs. What I wonder is how you are going to produce a similar, although much lighter aircraft.

On the other end of the spectrum we have a work in progress in the Sub-Sonex, a kit-built single engine jet. It is a bare-bones design using an over-sized model airplane jet engine. It has a projected empty weight of 330 lbs. and a gross of 750 lbs. These numbers will almost surely rise as the design matures.

What I (and others I'm sure) think is that it will be impossible to build an aircraft with Viper Fanjet performance, but with specs closer to a Sub-Sonex. Your design goals seem to be unrealistic. Please feel free to prove us wrong.
 

K-Rigg

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I see it this way.

I could find a second hand two seat military trainer jet for the price of your "engine".
 

BoKu

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Meh. The website shows no progress since 2009. I think Bill called this one.
 

Retroflyer_S

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I never saw this thread before.

Interesting a small Fouga Magister.

Foil stuff was cool. But the compressibility was it addressed at all ?
 

Chlomo

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Meh. The website shows no progress since 2009. I think Bill called this one.
And Bill is no longer with us as well.
Has peace finally arrived?
Who will be the next to take us all by storm?
 

autopilot

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An airplane does not necessarily need to be built larger if it's required to carry more fuel! It may be required to be built stronger though.
The simple addition of Tip-tanks can give an aircraft more fuel, hence range. It won't necessarily need a bigger engine either, but perhaps a longer take-off. See Lear, Hansa, etc., there are many examples of jets with "tip-tanks".
 
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