Book "Model Airplane Design," by Carlos Reyes

[Buzz_Man]

Disclaimer: I did a search but couldn't find a link with this book review on this forum - and - I'm not even sure if this is where this type of thread should be . . . anyway, read on . . .

I got this book two weeks ago and I really, really love it. For me, it was "just enough" technical information to keep my interest, while still making sense, without being "TMI." I believe the author does a superb job of explaining "the science" related issues of our hobby.

The book is really not what I thought it would be - I was expecting more examples of model airplane drawings showing what works, what doesn't and then explaining why. This does not make the book any less valuable to me, however, because there is lots of very useful information I enjoyed learning - and look forward to putting this new information to practice as I am planning on getting back into designing and building from scratch again. For example, the comments the author makes regarding propeller spinners - very interesting & useful - I'll do what the author says.

Mr. Reyes does not take the reader through a multiple step process such as "Step 1," then "Step 2." Instead, he fills your head with relevant information which all directly relates to the entire process of model airplane flight. This is accomplished in a way that's really explained well, enabling the reader to grasp concepts and get a feel for how this will impact their model airplane flight characteristics - I kept thinking, "Oh yeah, that makes sense," like a light bulb kept going off in my head as I absorbed this information.

I'd give this book 4 3/4 stars out of 5. The only nit-picking issue I'd suggest is showing some visuals - perhaps drawings of model airplanes and identify what's good, what's not - but I'm a visual learner, so go figure I'd have this comment. In any event, I'd highly recommend this book.

(link to Amazon.com for this book) (http://www.amazon.com/RCadvisors-Model-Airplane-Design-Made/dp/0982261322/ref=sr_1_1?ie=UTF8&s=books&qid=1244649637&sr=8-1)

[JetPlaneFlyer]

Looks like a quite comprehensive book judging by the contents list. A criticism based on the book preview is that his description of lift is, at best, oversimplified and missleading. His is description of induced drag is plain wrong..

I understand that he's trying to keep it simple and easy to follow but 'wrong' is still 'wrong' no matter how easy it is to digest.

Steve

[eflightray]

I agree 'wrong is still wrong', but some of us actually understand 'wrong' easier than 'right'.

Yes, that may sound sort of crazy, but if someone, even if wrong, (to some degree), explains something in such a way that it is understandable, and helps with the concept of understanding how something works, then to me it isn't all wrong.

What does lose me, (certainly looses my reading interest), is a long winded technical answer, (which even then sometimes gets argued by another 'expert').

Give me 'kiss' every time. (Please not the tongue sort, that definitely is the wrong sort of 'kiss'). :D

[JetPlaneFlyer]

H. L Mencken summed my feelings on this in a well known quote:
For every complex problem there is an answer that is clear, simple, and wrong
For me it does no one any favours to teach them an untruth regardless of how simple and appealing it may be. The lift theory described in the book has some elements of truth in it but is incomplete and misleading.. For instance it says the air going over a wing must travel further.. why is this so?... and why even if it does have further to go should this result in it moving faster?.. It just makes no sense.
The fact is Bernoulli does not explain how lift is generated.. An accurate explanation (that is actually very simple) can be found here: http://regenpress.com/

The induced drag story is just plain and simple wrong. The above link properly explains induced drag but it is a little harder to grasp as it required consideration of 3D airflow.

[Cap_n_Dave]

H. L Mencken summed my feelings on this in a well known quote:

For me it does no one any favours to teach them an untruth regardless of how simple and appealing it may be. The lift theory described in the book has some elements of truth in it but is incomplete and misleading.. For instance it says the air going over a wing must travel further.. why is this so?... and why even if it does have further to go should this result in it moving faster?.. It just makes no sense.
The fact is Bernoulli does not explain how lift is generated.. An accurate explanation (that is actually very simple) can be found here: http://regenpress.com/

The induced drag story is just plain and simple wrong. The above link properly explains induced drag but it is a little harder to grasp as it required consideration of 3D airflow.

Interesting link. I went to college and earned a BS in aerospace engineering in the late 80s/early 90s. I have spent quite a bit of time thinking about the cause-and-effect relationship of lift, as well as venturi flow. This topic was not discussed in class (that I can recall), and has caused me many headaches.

We were not instructed regarding circulation, and that particular explanation of lift still boggles my mind. From a math standpoint it makes sense, but in reality I find it to be absurd ... there is no air magically circulating around the wing to "add" and "subtract" to the flow velocity. BTW, the explanation about vortex shedding on your link is a bit problematic to me.

EDIT: the vortex shedding bit I am referring to is the example of flow off a cylinder.

I suppose I could learn more by experimenting ... perhaps someday I will have the time and money.

[Aphorism's Dream]

----------------//snip//-----------------------------
What does lose me, (certainly looses my reading interest), is a long winded technical answer, (which even then sometimes gets argued by another 'expert').

Give me 'kiss' every time. (Please not the tongue sort, that definitely is the wrong sort of 'kiss'). :D


Some things simply are not simple (oxymoron intended) to understand or explain.
We need to get over the concept that everything can be reduced to easily digested folk idioms.
However the practice of using the fewest, well chosen words to convey the concept is much to be desired. :o

[nmasters]

http://www.rcgroups.com/forums/showthread.php?t=983647&highlight=control+volume
http://www.rcgroups.com/forums/showthread.php?p=8260889

[Cap_n_Dave]

http://www.rcgroups.com/forums/showthread.php?t=983647&highlight=control+volume
http://www.rcgroups.com/forums/showthread.php?p=8260889

Good links, thanks for posting them.

I'm sure I will eat my words about circulation. The "bathtub example" is interesting but I think flawed ... although a cool piece of math I still have a hard time believing that in flight there is air rotating around the wing.

I like the High Lift paper and the sailboat stuff ... excellent. An interesting bit about the bathtub example is that it reminded me about paddling in a canoe. As a kid my dad and I would go fishing and he had a large canoe ... I recall staring at the water as I paddled. Good example of a starting vortex to be sure.

I also think that I got hosed at my college ... not sure if the profs were second-rate or I was an idiot (or both), but I am wondering if I should seek a refund.

[nmasters]

EDIT: the vortex shedding bit I am referring to is the example of flow off a cylinder.

Although a cylinder is typically used in demonstrations of the Kármán vortex street it's really the result of containing both sides of the flow around a bluff body between walls or very high aspect ratio. Here's a small street with colored ink in water (http://media.efluids.com/galleries/all?medium=136) Here'sa larger one viewed from space (http://media.efluids.com/galleries/all?medium=250) And here's a short bio of Dr von Kármán (http://www.centennialofflight.gov/essay/Dictionary/Von_Karman/DI123.htm). A google image search for "karman vortex street" returns 8650 hits. When there aren't walls you still get alternating vortex shedding but it's pretty messy and difficult (almost impossible) to photograph. You know the spiral wire that car antennae have now? That's a trip to push the vortex shedding to a higher frequency so the antennae don't vibrate as much as the old, smooth, ones. really :) it cuts down on body noise and delays metal fatigue. This is also what causes wing rock of a deep stalled sailplane

--Norm

ps The guy who explained this stuff to me has a masters so you probably just didn't have those classes yet

[Cap_n_Dave]

Although a cylinder is typically used in demonstrations of the Kármán vortex street it's really the result of containing both sides of the flow around a bluff body between walls or very high aspect ratio.

Thanks for the links ... the wikipedia page has some nice images: http://en.wikipedia.org/wiki/Von_Karman_vortex

Perhaps I should restate. My previous understanding of how the von Karman vortex street works was based on boundary layer theory and not circulation.

After thinking about it for a while, though, I can buy the circulation argument based on "equal and opposite" rules.

Looking at the von Karman vortices, you get vortex pairs that are essentially equal and opposite. After even more reflection, I would argue that this ties into the "bathtub experiement" in one of your earlier links/posts ... take the wing out of the flow and there will be an equal and opposite vortex that pairs with the starting vortex.

ps The guy who explained this stuff to me has a masters so you probably just didn't have those classes yet

Haha ... not sure how to interpret your statement.

1. I need post graduate education. I would agree with this.

2. The guys explaining it to me were overeducated. I would also buy this, my profs were PhD types ... a couple were even crackpots.

:)

[nmasters]

I was killing time watching youtube today and ran across a video that reminded me of this thread so bumping it up the page. It's not old enough to be a zombie, is it?
http://www.youtube.com/watch?v=_AJgEa2dbJU&NR=1

[dusty IV]

I was killing time watching youtube today and ran across a video that reminded me of this thread so bumping it up the page. It's not old enough to be a zombie, is it?
http://www.youtube.com/watch?v=_AJgEa2dbJU&NR=1

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Big deal. Seen it many times in my youth by standing on a bridge and watching muddy water past by. Same deal watching water past by a round rock. Sure didn't teach me anything that I was able to applied in a long life as an Engineer.

I think almost every thing I learned in School that was useful was acquired by the 3rd grade. But I admit I'm a bit limited as I was reminded once or twice by teachers.