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Old Feb 10, 2008, 02:59 AM
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thats cause most times they travel faster than the plane itself goes so they have to limit the air that goes in. jets inlets have zero applicable principles to slow moving ducted fans. if you make the inlet with big curved edges slow moving air wont get in fast enough, and with slow fans speed is key. and dont want to make it fan diameter size all the way back to get rid of curve cause then fan is limited in speed cause it now gets too much air in the duct. ideal inlet is opening the exact size the fan can process and process fast, which is FSA, right to each and every rotor blade. trust me I've tried every duct under the sun for over a decade, the air does not see spinner or deviation in wall matching spinner.

Barry
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Old Feb 10, 2008, 05:51 AM
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Quote:
Originally Posted by monkamarm2000
thats cause most times they travel faster than the plane itself goes so they have to limit the air that goes in. jets inlets have zero applicable principles to slow moving ducted fans. if you make the inlet with big curved edges slow moving air wont get in fast enough, and with slow fans speed is key. and dont want to make it fan diameter size all the way back to get rid of curve cause then fan is limited in speed cause it now gets too much air in the duct. ideal inlet is opening the exact size the fan can process and process fast, which is FSA, right to each and every rotor blade. trust me I've tried every duct under the sun for over a decade, the air does not see spinner or deviation in wall matching spinner.

Barry

Barry
I'm not discussing your experience with fan,but I' have to say that you are not entirely in in what phisics principle really are.
I have some problem understanding your english so ,maybe it's my fault too.
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Old Feb 10, 2008, 11:44 AM
smug in granny panties
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hey dont sweat it! thats why were here right? have fun discuss things and trade points of view. sometimes just takes longer to discuss with language and text barrier! haha

As for fan and physics I think I'm right where real workd EDF physics are. Through the years I have gone same route as you looking at jets and such then finding out none of the rules apply at our level. And this is from real world testing from compu flo and actual laminar testing(strings and all). hardest lessons to learn in EDF are, Air acts like a fluid, and air does not come from inlet to fan, it is drawn from fan to inlet. so where jets have gobs of extra power and multi stages out back to process more air than is in front of them, and velocity out back faster than it can even process, then you have different needs than edf will ever see.
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Old Feb 10, 2008, 04:56 PM
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Hey nem -

I dropped plans for the molded fiberglass fuse, on my Raptor, and am going with the wood construction technique, like you. I figure there will be many changes to the airplane as time goes on, and wood lends itself to easy modification. Your ducts look good to me, I am sure they will work just fine.

Ron
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Old Feb 11, 2008, 09:57 AM
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For those of you who are currently working on F22's. I would like to share my plans with you at this time. This way we can compare notes. You are not required to share yours with me. But I would like comments and suggestions on where I am going wrong and what can be done better. Please let me know if any of you would be interested in this.

Thanks, Nick
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Old Feb 11, 2008, 12:08 PM
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Quote:
Originally Posted by nem3
For those of you who are currently working on F22's. I would like to share my plans with you at this time. This way we can compare notes. You are not required to share yours with me. But I would like comments and suggestions on where I am going wrong and what can be done better. Please let me know if any of you would be interested in this.

Thanks, Nick
You betcha
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Old Feb 11, 2008, 12:25 PM
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Please pm me you email info and what format/version you prefer.
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Old Feb 11, 2008, 12:56 PM
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Hi nem -
Your version of the Raptor looks pretty good, but not perfect. I think
I have seen enough to venture a little advice.

Warning - I like to stick to the very basics, and I hate big words.

Most Basic;
This is an EDF airplane, and we want it to be a good flier. Therefore the
center-of-gravity must be correct. Since heavy batteries are a necessary
part of the payload, battery placement is a primary consideration. Do you
have the room to put the battery where it needs to be to make the right
C of G?

Along the same lines is the size of the airplane. A smaller airframe
is lighter (always a good thing), but get it to small and there is not
enough room to fit everything in there. Easy to change size with CAD


Power loading, and wing loading must be in the ballpark; check the numbers
on good flying, commercially available airplanes to get a sense of what
works.

At least that's my take on the situation.

Ron
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Old Feb 29, 2008, 04:42 PM
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Update Number 3

For those of you following this thread. I have good news. The plans are progressing nicely and I think for the first time I can see an end in sight. I now have all the servos placed, bulkheads cutout, wing attachment mostly figured, and the bulkhead supports. Next up is continuing on with the canopy section. I had already attempted this section but got discouraged with it because it was not coming out the way I wanted it to be. But I don't have much of a choice now. Well maybe I can get the rudder fins done first. Nothing wrong with a little more procrastination. Anyways here are some more pics for you guys. Thanks for the support.
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Last edited by nem3; Feb 29, 2008 at 05:12 PM.
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Old Feb 29, 2008, 05:00 PM
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Quote:
Originally Posted by Ron Pogue
Hi nem -
Your version of the Raptor looks pretty good, but not perfect. I think
I have seen enough to venture a little advice.

Warning - I like to stick to the very basics, and I hate big words.

Most Basic;
This is an EDF airplane, and we want it to be a good flier. Therefore the
center-of-gravity must be correct. Since heavy batteries are a necessary
part of the payload, battery placement is a primary consideration. Do you
have the room to put the battery where it needs to be to make the right
C of G?

Along the same lines is the size of the airplane. A smaller airframe
is lighter (always a good thing), but get it to small and there is not
enough room to fit everything in there. Easy to change size with CAD


Power loading, and wing loading must be in the ballpark; check the numbers
on good flying, commercially available airplanes to get a sense of what
works.

At least that's my take on the situation.

Ron
I think so
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Last edited by nem3; Jan 16, 2012 at 01:20 AM.
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Old Feb 29, 2008, 07:57 PM
smug in granny panties
monkamarm2000's Avatar
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looks good! I dig it! had a thought looking at it too. I wonder if the bearings for tail surfaces could be extended to catch a center rod for swinging exhaust's? just thinking out loud here. cause if top and bottom plates were connected on single frame maybe they could pivot on this from a single servo? make it easier to setup for sure, less linkage and wires and stuff. I did similar with my test setup and it worked quite well.

Barry
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Old Feb 29, 2008, 07:58 PM
smug in granny panties
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oh and i think you'll be fine cg wise. you got plenty of servo's and fans back there to even it all out.

Barry
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Old Feb 29, 2008, 08:57 PM
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very, very nice
I wish I could think that far ahead
Bill Lowe
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Old Mar 01, 2008, 11:29 AM
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Thanks Bill and Barry. Words of encouragement are always greatly appreciated.

As for the servos, it would be easier that way, but my goal is to also have variable area exhaust. Now this is only a test type of thing. Because I have no idea if it will help, hurt or do nothing. But I think its worth a try. Funny thing is that the 4 S3114's I plan to use weigh as much as one of the S9650's for the elevon's. So the added weight is not that big. But if it works it will be well worth it. Not to mention being able to do this.
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Old Mar 01, 2008, 12:51 PM
smug in granny panties
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well i think it could help in the opening part. closeing down can get sticky cause it will raise the load on the motors. So I'd set them as small as you plan to go and set kv to motor and load from there, then mess with opening them for more static, if you go the other way it might go into over amp zone if theres not enough overhead. Dig that pic though, I had messed with the idea on mine as using that as an airbrake. On bench testing though I found anything past 100% of the exhaust duct size made no diff cause they can go as open as they want cause at the base of them the tube is what size the tube is so that'll be your exit FSA. But there is a tad bit of coanda effect as it clings, but it was barely enough to blow a string.

Barry
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