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Old Feb 10, 2012, 06:44 PM
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Doug W's Avatar
United States, WA, Seattle
Joined Jul 2010
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Originally Posted by bamaguy View Post
Derek;

I can appreciate the fact that you are a structural engineer, but IMHO, you are "over engineering" just a bit here. Based on my experience with my 737, items #1 and #2 are not necessary.

In regards to #1, EPO will flex MUCH more than the other types of foam before breaking. As I will eventually mod mine for flaps, I did install a 5/16 dia CF tube just ahead of where I intend to cut out the wing for flaps. I extended it to about the mid area of the aileron hinge line. Got about 9 flights on it. The wing flex looks pretty much "scale", as the full size wing flex.

As for #2, a good glue line of the ply/EPO "sandwich" will yield a very strong pylon assembly.

I totally agree with #3. I installed some stainless steel 3mm rods. But I still managed to bend them slightly. (I need to make better landings!)

Anyway, good luck with your build and whatever mods you choose to do. You'll love this model!
I agree with Bama on number 2- don't reinforce the pylons- the epoxy/ply sandwich will do it fine. You actually want them to snap in a crash, otherwise the whole wing structure is ruined. I made an "off airport landing" with mine (a kid cut in front of me on short final and I felt it best not to hit him in the head with a 9lb model going 30 mph- so I ditched it into the grass next to the runway) this past fall and snaped the wood- it was an easy fix: Cut into the foam, sister it with ply on both sides- four mini lock screws, and done.

As for number 1, again, I'd only reinforce if you are adding flaps- because you do lose a lot of wing strength. No flaps, no need for reinforcement.

As for the landing gear- that is my only gripe on the model. Flights 14 and 15 that I posted were smooth landings with two of three NEW landing gear- nose and right main. Two landings later, both grub screws are very loose both gears now wobble. Again, a very minor shortfall considering the incredible engineering Ming put into this beauty.
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Old Feb 10, 2012, 06:49 PM
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Originally Posted by jakob k View Post
Still no thoughts on this matter?

Doug you also use HET does your houing have scrape marks on the inside?
Sorry jakob k- I missed the question. Yes, I am HET 6904 with 2W-20 power and 75A ESC. I do have a couple smallish rub marks on the inside of the fan housing but I am truly not gifted enough of an RC pilot to tell any difference in performance. I haven't tried it but I am convinced I have enough power to to take off and fly at 50% power with the motor/fan combo.

I am building a second WIndrider 737 and will add the exact same power set up as my Alaska -700.
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Old Feb 11, 2012, 12:55 AM
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Cape Coral, FL
Joined Nov 2001
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Originally Posted by pulsery2k1 View Post
reinforcing is a good thing , but a lighter model will fly better
Agree. Lighter is better. The carbon rods to reinforce both pylons will add 6 grams total plus glue, so I'm OK with that.

Quote:
Originally Posted by bamaguy View Post
As for #2, a good glue line of the ply/EPO "sandwich" will yield a very strong pylon assembly.
Quote:
Originally Posted by Doug W View Post
I agree with Bama on number 2- don't reinforce the pylons- the epoxy/ply sandwich will do it fine. You actually want them to snap in a crash, otherwise the whole wing structure is ruined.
Well, at least my prediction of the pylon failure point was just about right . A clean snap is obvious to deal with. I'm more concerned with hidden damage like a minor facture - you will never hear a slight "crack" during a mishap. I still think I'm going to add the carbon on mine. That's the fun of this stuff - just try it and see what happens. If my wings shred off and all that's left is the nacelle, it'll be like a Star Wars Pod Racer..... There's different degrees of crash - if I crash bad, then I'll take my lumps. But if I have to ditch land in the grass, it should still hang together and have confidence there is no hidden fractures in the plywood.

My Precision Aerobatics Addiction had a "beautiful" engine mount, but way too fragile. It could not hold up to what I call minor mishap. I botched a landing and cartwheeled it. Keep in mind, this airplane needs like 4 feet of runway to "land", so there is almost no speed. The engine mount fractured in several places, but otherwise seemed intact. There was absolutely no other damage to the airplane. To repair the mount, I applied generous amounts of CA all over and it looked good and "felt" strong. Then I did a test run up in the garage. I checked the motor and new prop for vibration and it was perfect. I did a burst to 3/4 throttle, and the whole thing exploded - instantly - there was no time to react. Luckily my whole body was behind the prop. I'm guessing the motor bounced off the concrete floor and I heard it hit the far wall and felt the prop blade fly past my face.

My homemade replacement motor mount is "Rambo" and the little extra weight is not even noticed.

I know this 737 is "just a ducted fan", but hidden damage to the plywood from a minor mishap will not be possible to detect. If I'm going down, I don't want my engine to be the first thing heading for the Exit door .

And lastly, the dreaded cut finger photo . A separate incident. Failed motor mount. 10 stitches. Severed nerve. Surgery to repair nerve. 2 years later and still partial numbness in my fingertip.

From now on, I like a stout motor mount. That's only 2 incidents over many years, but that's enough. You never think it can happen to you - it's just a toy. Yes, those were both props, but hmmm, EDF turns 35,000 rpm.
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Old Feb 11, 2012, 06:27 AM
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Danmark, Midtjylland, Horsens
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Originally Posted by Doug W View Post
Sorry jakob k- I missed the question. Yes, I am HET 6904 with 2W-20 power and 75A ESC. I do have a couple smallish rub marks on the inside of the fan housing but I am truly not gifted enough of an RC pilot to tell any difference in performance. I haven't tried it but I am convinced I have enough power to to take off and fly at 50% power with the motor/fan combo.

I am building a second WIndrider 737 and will add the exact same power set up as my Alaska -700.
Thanks Doug.

By the way I love looking at your videos, it almost makes my eyes water up. I Was an exchange student in 99/00 in Ketchikan, AK and I have always been a swimmer and I got to travel a lot so I have been on a lot of those Alaska Airlines planes.(When I have been to alaska with my wife in recent years she has already started to hate "The milk run" I think its flight 63 or 64:-) thats plane which has half a passengers compartment and half a freight compartment. And it stops atleast three times between Seattle and Anchorage )

And on the third note. I am currently writting my bachelordegree project(Mechanical engineering, double majoring ind product design and innovation, and Intelligent mechanics), and believe it or not but it is actually for a company called Flamingo which is danish company and they are actually one of the co-inventores of EPO(The true inventor is BASF in Germany). So if you would like me to, then I have a completely different insight to this material, so I can do a FEM analysis on a wing if somebody have a 3d-cad file of the wing, then I will tell you if you would need to reinforce, and how much.

-Jakob
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Old Feb 11, 2012, 08:40 AM
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Cape Coral, FL
Joined Nov 2001
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Originally Posted by jakob k View Post
I can do a FEM analysis on a wing if somebody have a 3d-cad file of the wing, then I will tell you if you would need to reinforce, and how much.

-Jakob
Jakob,

It sounds like you have quite a few interesting projects.

For a 3D model, I would say the best person to contact is Mr. Ming directly at Windrider. Go to their website and use the contact email. He has responded to a few I sent. Based on the drawings Mr. Ming posted, I'm quite sure he developed a 3D computer model. But I also guess he would be quite reluctant to release the computer files to anybody.

The next best thing, you can try contacting some people on the Realflight simulator Knife Edge forum swap pages. The guys that contribute "models" have to generate a full 3D mesh. There are some airliners, no 737's buy several 777 and 787. They use the "KEmax" Knife Edge Content Creation Toolkit. I never messed around with it. The wings for the 777 and 787 are probably close enough for your investigation.

Then there's the old fashioned way. Try it and fly it.
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Old Feb 11, 2012, 12:55 PM
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United States, WA, Seattle
Joined Jul 2010
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Originally Posted by DerekB View Post
Agree. Lighter is better. The carbon rods to reinforce both pylons will add 6 grams total plus glue, so I'm OK with that.





Well, at least my prediction of the pylon failure point was just about right . A clean snap is obvious to deal with. I'm more concerned with hidden damage like a minor facture - you will never hear a slight "crack" during a mishap. I still think I'm going to add the carbon on mine. That's the fun of this stuff - just try it and see what happens. If my wings shred off and all that's left is the nacelle, it'll be like a Star Wars Pod Racer..... There's different degrees of crash - if I crash bad, then I'll take my lumps. But if I have to ditch land in the grass, it should still hang together and have confidence there is no hidden fractures in the plywood.

My Precision Aerobatics Addiction had a "beautiful" engine mount, but way too fragile. It could not hold up to what I call minor mishap. I botched a landing and cartwheeled it. Keep in mind, this airplane needs like 4 feet of runway to "land", so there is almost no speed. The engine mount fractured in several places, but otherwise seemed intact. There was absolutely no other damage to the airplane. To repair the mount, I applied generous amounts of CA all over and it looked good and "felt" strong. Then I did a test run up in the garage. I checked the motor and new prop for vibration and it was perfect. I did a burst to 3/4 throttle, and the whole thing exploded - instantly - there was no time to react. Luckily my whole body was behind the prop. I'm guessing the motor bounced off the concrete floor and I heard it hit the far wall and felt the prop blade fly past my face.

My homemade replacement motor mount is "Rambo" and the little extra weight is not even noticed.

I know this 737 is "just a ducted fan", but hidden damage to the plywood from a minor mishap will not be possible to detect. If I'm going down, I don't want my engine to be the first thing heading for the Exit door .

And lastly, the dreaded cut finger photo . A separate incident. Failed motor mount. 10 stitches. Severed nerve. Surgery to repair nerve. 2 years later and still partial numbness in my fingertip.

From now on, I like a stout motor mount. That's only 2 incidents over many years, but that's enough. You never think it can happen to you - it's just a toy. Yes, those were both props, but hmmm, EDF turns 35,000 rpm.

OK, I'll give in- that cut is just nasty. I think each of our individual experiences color or reactions to things, and man- if I cut my finger like that, I'd probably walk away from RC flying (or maybe wear a suit of armor while flying!) I've heard of expolding EDFs before too (uncontained catastophic engine failures) and they can get ugly and dangerous too. For a "nerdy" hobby (as I have heard it called by the dissenters), it requires many safety considerations.

And the RAMBO motor mount rocks- I need that for my old Eflite PT-19 which has the same engine mount issues. I'll post a pic of my engine mount repair- I've got a couple flights on the 737 since the repair and it seems to hold well.
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Old Feb 11, 2012, 01:36 PM
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kulula flying 101 engine 2 almost complete first time covering any type of model not bad for the 3rd time trying to cover it lol thanks to all u guys who posted how to's on here this being my first major build would not be possible thank youName: DSC00811.jpg
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Old Feb 11, 2012, 02:48 PM
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Originally Posted by DerekB View Post
Jakob,

It sounds like you have quite a few interesting projects.

For a 3D model, I would say the best person to contact is Mr. Ming directly at Windrider. Go to their website and use the contact email. He has responded to a few I sent. Based on the drawings Mr. Ming posted, I'm quite sure he developed a 3D computer model. But I also guess he would be quite reluctant to release the computer files to anybody.

The next best thing, you can try contacting some people on the Realflight simulator Knife Edge forum swap pages. The guys that contribute "models" have to generate a full 3D mesh. There are some airliners, no 737's buy several 777 and 787. They use the "KEmax" Knife Edge Content Creation Toolkit. I never messed around with it. The wings for the 777 and 787 are probably close enough for your investigation.

Then there's the old fashioned way. Try it and fly it.
Well If I have the time then I could just 3d-scan a wing and generate a mesh from that.
BUT I would only do this if somebody reeeeeaaaallly need this information about reinforcement,since 3d.scanning plus 3d modelling and then a FEM... Hm I would say about 10-15 hours of HARD work. And the company I currently work with at the moment "only" charges about 450$ US for one hour of my labor :-)

And in about 3-4 months when Im done with my bachelordegree it would be close to the double of that since FEM or FEA is very hardcore theory and calculation.


-Jakob
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Old Feb 11, 2012, 11:59 PM
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Originally Posted by markyb13 View Post
kulula flying 101 engine 2 almost complete first time covering any type of model not bad for the 3rd time trying to cover it lol thanks to all u guys who posted how to's on here this being my first major build would not be possible thank youAttachment 4625038
Looks awesome- can't wait to see the model all done!
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Old Feb 12, 2012, 08:15 AM
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hey doug thanks was wondering what amp bec you were using in youre plane if youre using one.also if u needed 1 for each esc or if just using one is good thanks
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Old Feb 12, 2012, 09:47 AM
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Originally Posted by markyb13 View Post
hey doug thanks was wondering what amp bec you were using in youre plane if youre using one.also if u needed 1 for each esc or if just using one is good thanks
I use a Castle Creations 10amp, which is an overkill....you only need 1. Mine is connected to its own battery...(a 2 cell LiFe, 1100mAh)......there is plenty of space and a few ounces of "extra" weight is not a problem in the 737.
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Old Feb 12, 2012, 12:59 PM
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Originally Posted by markyb13 View Post
hey doug thanks was wondering what amp bec you were using in youre plane if youre using one.also if u needed 1 for each esc or if just using one is good thanks
Quote:
Originally Posted by bamaguy View Post
I use a Castle Creations 10amp, which is an overkill....you only need 1. Mine is connected to its own battery...(a 2 cell LiFe, 1100mAh)......there is plenty of space and a few ounces of "extra" weight is not a problem in the 737.
Funny, that's the exact thing I'm trying to figure out right now. Trying to decide between these 3 from Hobbypartz:
Exceed RC UBEC-3A (2-6S Lipo Input)
UBEC-5A-HV (High Voltage Ultimate BEC)
UBEC-8A (Ultimate BEC)

I will have Nine 9 gram servos and 3 retracts, so I guess that's like 12 servos.
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Old Feb 12, 2012, 01:01 PM
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Joined Dec 2010
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get the 8A UBEC more amps availible to your servos meaning you can easily run lots of servos
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Old Feb 12, 2012, 01:09 PM
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Originally Posted by jakob k View Post
BUT I would only do this if somebody reeeeeaaaallly need this information about reinforcement...

-Jakob
I think most of us are in the "try it and fly it" club. It would be up to your personal curiosity and love of the hobby and maybe excitement of exploring your FEM skills. You would also have to know the mechanical properties of the carbon tubes and the glue itself. I studied FEM in college also, enough to know it is quite complex.
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Old Feb 12, 2012, 10:16 PM
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Originally Posted by DerekB View Post
Funny, that's the exact thing I'm trying to figure out right now. Trying to decide between these 3 from Hobbypartz:
Exceed RC UBEC-3A (2-6S Lipo Input)
UBEC-5A-HV (High Voltage Ultimate BEC)
UBEC-8A (Ultimate BEC)

I will have Nine 9 gram servos and 3 retracts, so I guess that's like 12 servos.
I'm running a Catle 10A BEC, programmed to 4.8V as all my servos are 4.8V (as opposed to 6V)
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