Notices
Electric RC Jets Discuss rc electric ducted fan or radio control prop jets here.

Not a happy camper!

Old 08-12-2011, 04:31 AM
  #1  
Avaiojet
Thread Starter
 
Join Date: Sep 2002
Location: Jupiter , FL
Posts: 3,157
Likes: 0
Received 6 Likes on 6 Posts
Default Not a happy camper!

Who ever thought choosing a "contemporary" fan set up, for a particular airframe, would be as complicated as it is? Does it have to be?

Fans. They ain't rocket science. 35 years ago we played around with Duane Johnson's "Jet Pump" and had fairly good results with it.

35 years ago!

From an engineering standpoint, that is, the design factor, Duane already did it! He did it with wood blades and frickin coffee cans and managed to get airplanes to fly.

From my point of view, maximum thrust efficiency would be the goal! Anyone disagree with that?

One would think, that in the design process, once you get it ya got it!

So, why so many different options, AND, different options from TOO many manufacturers?

Some of these blade designs are so different, you can't possibly achieve the same results.

Yea, I'm not a happy camper!

Somebody cheer me up.



Old 08-12-2011, 08:27 AM
  #2  
MaxThrottle
Senior Member
 
Join Date: Jan 2003
Location: Barrie, ON, CANADA
Posts: 281
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Not a happy camper!

What is in constant change is the Batteries, Motor and ESC technology. They constantly improve and have different characteristics that one setup vs another can play to.
Also some setups are for high thrust, others higher efflux while other efficiency. You can't get in all in one.

You are correct though that the variences shouldn't be that great when one look at a Wemo for example. If has far exceeded the life cycle of the rest of its drive train counter parts. Bigger motor higher rpm.... it just hums along and gives good results regardless.
But Wemo is expensive and with models complete RTF, PNP, ARF models trying to stay in the $100-$200 price point.... a wemo just eats up all of that bottom line. So people come up with other that won't infringe on some one elses patent.
The question is the equal to why are there so many smartphones and tablets and PCs and TVs and......
Old 08-12-2011, 12:56 PM
  #3  
Avaiojet
Thread Starter
 
Join Date: Sep 2002
Location: Jupiter , FL
Posts: 3,157
Likes: 0
Received 6 Likes on 6 Posts
Default RE: Not a happy camper!

MaxT,

Hey Max!!

Shame on you for replying to this Thread. I had 44 views and not one single comment.

I lost my bet, I said their would be at least 75 views before I received a single reply. You cost me 10 bucks!

Well, just goes to show you there's at least one Jethead that has something to offer out of 44.

Not too shabby compared to other less interesting threads. Well, this thread is far from interesting.

OK Max, that TV thing, that's all about money, and it's geared towards a large audience. How many Jetheads are there?

So the marketplace is really competitive.

OK, who doesn't want THRUST! The more the better. What I don't want is exaggeration, either by a Jethead or a provider.

I'd doing my homework, and it's taken a while because, as you have proven, one reply out of 44 views, doesn't give me much to go on.

The slower the information, probably the more accurate it will be.

I'm in no hurry.

Charles
Old 08-12-2011, 08:50 PM
  #4  
MaxThrottle
Senior Member
 
Join Date: Jan 2003
Location: Barrie, ON, CANADA
Posts: 281
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Not a happy camper!

That kind of sounds like you have an actual question! Cause I'm not sure if you are asking about something specific or just wanted to share your unhappiness
Or concerned with posted vendor numbers. Thats why certain forums have guys that level the playing field and actually test an apples with apples comparison.

But there still remains what you decided to purchase. You may have got different batteries, ESC, added more wiring than you should, used insufficient connectors for your applications and thus from many possiblilities you come up with something a little less, sometime more.

Considering my last comment, while Wemos do very well, the new Efflux/Mach has come up with a all alloy fan that with certain motors have increased the magnitude of thrust by more than a full kilogram. The amp draw though is high. So that setup is not for all applications. So there isn't a one size fits all.

Are you asking about details on the different approaches and which performs better or are you seeking to answer an actual applicaton?

Just saw your post on RCG. Still not sure what you're looking for though. RCG has extensive discussions and theory of the various fan concepts. Some of the posts in that Forum already point to the idea that there is a reason why there isn't a one size fits all but also that some may not perform as well as others and if you are aware of the theories you'ld generally have an idea why. But some designs do last , the small GWS 64 on a Alfa setup with the right motor can be very lite, low amp draw needing less battery. But its not easy to balance to get the numbers. Its usually better to have a Vendor do it for you. For those who don't want that route, they by something that's relatively easy for anyone to setup but has other disadvantages.
There's loads to consider one setup in one model over another setup in another.
Old 08-13-2011, 12:47 AM
  #5  
Extreme_RC
 
Extreme_RC's Avatar
 
Join Date: Oct 2008
Location: , AUSTRALIA
Posts: 424
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Not a happy camper!



ORIGINAL: MaxThrottle
Considering my last comment, while Wemos do very well, the new Efflux/Mach has come up with a all alloy fan that with certain motors have increased the magnitude of thrust by more than a full kilogram. The amp draw though is high. So that setup is not for all applications. So there isn't a one size fits all.
Not quite, the 70mm Mach fan has been run to 2.95kg thrust peak at 120 amps, the Extreme Wemo hit 2.73kg thrust peak at only 90A, settling to to 2.55kg thrust at 86.7A. This means 30A increase for only 265grams thrust, thats a lot of amps in a 70mm model no matter what the size.

Avaiojet:
End of the day you need to set parameters, what is your model size, weight, wing area, what do you want it to do, and how much room do you have to fit fans and batteries. I have been building fans commercially for over 5 years, I have tested dozens and dozens of setups and my products revolve around efficiency and cost effectiveness.

Wemotec rotors are universally accepted as about the best out there in a conventional fan. Even stumax praises them, their numbers are consistent and they are the most efficient I have tested, and when you compare figures of the chinese fans against the wemos you will find they use less amps to do the same work. For me its all about the best efficiency, second comes price. This is why I have not gotten involved with these alloy fans, I dont see the benefit, they are a little less efficient and they are extremely expensive, $240.00 for a fan compared to $55.00 for a wemo, big difference especially when the wemo is more efficient.

A wemo Minifan PRO and the best ARC motor and some heatsinks = $170.00, a complete 6 cell 2.5kg sustained thrust package thats proven, we have flown it in 2 models and hammered it around, no 3 second fast passes then tool around with my jets, I like to fly WOT for at least 70% of the time.

Old 08-13-2011, 01:03 AM
  #6  
Extreme_RC
 
Extreme_RC's Avatar
 
Join Date: Oct 2008
Location: , AUSTRALIA
Posts: 424
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Not a happy camper!

If you are talking about 90mm fans then you have to look at the overall picture, the mach 90mm was being run on 12s...5.6kg thrust at 115 amps, thatsway highamps and cell size even for a 90mm fan. The Wemo Midifan PRO pushes 4.4kg thrust on 8 cells at 100A with the ARC3675-1 motor, with the 3675-1.5 motor on 12 cells its at 5kg thrust, only 85A though and this was tested over a year ago with old 30c packs.

A 5000mah 12s pack is gonna weigh a LOT, and will get barely 2-2.5mins of flight at 23c on the 115A load.

A 4200mah 12s pack is considerably lighter and also has better run time at only 20c on the 85A load.

Its all relative, but what doesnt change is the models ability to lift the weight, it doesnt matter if you gain 600g thrust and only add 250g in weight, the point is you have still added weight to a wing of fixed size and lift, once you go past a certain point the model flies like crap, take the Sapac viperjet, all the videos I have seen of them over 2kg shows a model that flies heavy, lands super hot, and is not enjoyable to fly. We built one on 6s at 2.1kg and it was a pig in the air, the frame just wasnt capable of carrying that much weight well and this was a bungee model, the ones with retracts are even heavier.
Old 08-13-2011, 04:40 AM
  #7  
Avaiojet
Thread Starter
 
Join Date: Sep 2002
Location: Jupiter , FL
Posts: 3,157
Likes: 0
Received 6 Likes on 6 Posts
Default RE: Not a happy camper!


I want all 12 blades baby!!

Damn I love saying that!

I want all 12 blades baby!!

And I probably won't settle for anything less. Can you blame me?

OK, let's start from scratch. I've posted many photos of my airframe, in a couple of Threads, and the information I receive is all over the place! You can find these Threads easily. Here's some photos.

Specks, here goes.

Span, 48", fuselage length 56". Empty weight naked, at the moment, 3.25 lbs. Plenty of room for a "unneeded" 6" Fan!
Intake area. Haven't done the math, but they measure, 4.25" in height by 2.125" wide. Yes, ovals. The airfoil is not by any means thin and I have washout. The model will have electric retracts, and flaps.

I'm thinking the Stumax 100MM. At least that's where I'm headed. Maybe the Stumax 90MM, but that may fall a bit short.

Hey! If you don't mind, What's the Thrust in lbs?

OK, please, do the Tech. Weight, batteries, thrust? Equals= what should my setup be? Shouldn't be hard for you guys.

I'm counting on your expertise.

I want all 12 blades baby!!

Thanks

Attached Thumbnails Click image for larger version

Name:	Jg14386.jpg
Views:	31
Size:	174.8 KB
ID:	1648265   Click image for larger version

Name:	Vq51713.jpg
Views:	29
Size:	91.0 KB
ID:	1648266   Click image for larger version

Name:	Pu52365.jpg
Views:	34
Size:	131.1 KB
ID:	1648267   Click image for larger version

Name:	Ey70797.jpg
Views:	44
Size:	134.4 KB
ID:	1648268   Click image for larger version

Name:	Yk66427.jpg
Views:	38
Size:	207.8 KB
ID:	1648269   Click image for larger version

Name:	Wn87684.jpg
Views:	32
Size:	118.7 KB
ID:	1648270   Click image for larger version

Name:	Ce69803.jpg
Views:	37
Size:	215.7 KB
ID:	1648271   Click image for larger version

Name:	Vu68676.jpg
Views:	36
Size:	146.8 KB
ID:	1648272  

Old 08-13-2011, 11:09 AM
  #8  
speed is life
 
speed is life's Avatar
 
Join Date: May 2006
Location: Redstone, CO, USA
Posts: 390
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Not a happy camper!

Charles,
Before you get too wrapped up in choosing a fan you need to calculate the EXACT total intake area. Measure it from the point of the ellipse on the leading edge of the intake (catchment area) and not the inside of the duct.
Once you know the intake area THEN you can get an educated guess as to acceptable fan size.

Your intake ducts will be a big factor in performance as well, keep the area constant all the way, no converging or diverging area from intake face to fan face, smooth curves, no sharp edges.

With most of the current multi blade fans (like the Stumax) you can get away with intakes as small as 85% of Fan Swept Area ie: "FSA" without any serious penalty in performance in flight. Yes, small intakes will lower your static thrust, but static thrust doesn't fly the model.

An email to Stuart Maxwell can get you the FSA of his SM89-45 and SM100-45

Cheers,
Mike Warren
Old 08-13-2011, 12:45 PM
  #9  
Avaiojet
Thread Starter
 
Join Date: Sep 2002
Location: Jupiter , FL
Posts: 3,157
Likes: 0
Received 6 Likes on 6 Posts
Default RE: Not a happy camper!

Speed,

Thanks for the reply.

Yes, small intakes will lower your static thrust, but static thrust doesn't fly the model.
Wow! That has me thinking. I thought it was the amount of "thrust" that propelled the model forward? What am I missing here? I could use some help understanding that, cuz that's a schocker.
Also,

Measure it from the point of the ellipse on the leading edge of the intake (catchment area) and not the inside of the duct.
I don't think I ever heard the term, "catchment area." Are you saying the openining isn't the area measured? I can add a bit with the "lip" of the intake?

I must say, all good and interesting news.

Here's the thing. When I designed this model, it was originally set up for a Rossi 61, prop. Because of this set up, I deliberately decreased the size of the intake openings. What you see in the photos are smaller than what scale openings would be.

I'm drawing that area not and will make the changes. Actually not as easy as it might appear.

Please, don't forget to school me on the information in your reply.

Thanks again for that.

Yes, Stu has beem gracious with responding to my questions.

"Gimmie the whole 12 blades baby!"
Old 08-13-2011, 01:32 PM
  #10  
speed is life
 
speed is life's Avatar
 
Join Date: May 2006
Location: Redstone, CO, USA
Posts: 390
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Not a happy camper!

Static thrust is just that.......static, as in not moving...... and can fall off drastically in flight. Static thrust is a sucker hole for those who believe advertising copy is the holy grail of truths. Tells you nothing of performance in flight which is, properly, dynamic thrust.
You can achieve eye popping "static thrust" on a test stand with a trumpet style intake adapter and straight tube exhaust duct (or even no exhaust duct) but you will get very low efflux velocity which will handicap in flight performance. This is why we choke the exhaust tube down to some smaller % of FSA (or sometimes % of intake area).......to get better efflux speed. This reduces the static thrust but gives better thrust and speed while in flight where it counts.

With properly done intake lips and ducting you can get by with what looks like marginal static thrust but in reality the model will perform better in flight due to decent dynamic thrust that begins to occur after the plane accelerates.



Yes, you can use the lip of the intake. Whatever the stagnation point of the intake radius happens to be. Look at it as if it were a funnel to direct air down the intake, where the intake lip will divide the airflow between flowing into the intake -vs- flowing outside the intake.
There are some older threads (from back around 2003-2006 ?) by guys like Klaus Scharnhorst as well as "clausxpf" rom Denmark over at RCG's on EDF design theory that can be searched out. Lots of no BS info on intake, duct, fan design, etc. Hard to find with their search function tho........

Cheers,
Mike



Old 08-13-2011, 03:15 PM
  #11  
Extreme_RC
 
Extreme_RC's Avatar
 
Join Date: Oct 2008
Location: , AUSTRALIA
Posts: 424
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Not a happy camper!

It is the amount of thrust that propels the model forward combined with exit velocity, until an aircraftvelocity is reached where the thrust equals the drag and it goes no faster. Yes perfectly designed ducts are preferable, are they absolutely necessary? no, I have seen plenty of models with poor ducting or even no ducting perform extremely well, even draggy airframes with barely 1:1 power to weight.

Good example is the abomination sold on ebay as an F16 with glider wings, an awful fuse design full of formers, and a sharp lipped intake leading into a huge void filled with crap. A friend fited a 70mm fan to one (it could take a 90 easy) and set it up on 6s with the ARC2858 motor, pushed 2.4kg thrust and weighed 2.5 all up, the thing flew superbly, clocked at 125mph. Yes it would have likely picked up some speed with a duct added to the front, but its a draggy model and the increase would not have been worth the effort. The same fan in a Sapac viperjet did around 135-140mph in a much smaller lighter sleeker airframe with full ducting. It was a good real life experiment.

Bench testing is needed, its about the only way to get a good baseline across the setups and get some idea of what you are getting.

Testing without an inlet lip is a waste of time, the disruption to flow a sharp edge right at the front of the fan makes deems testing pointless, not just because of the large variations in thrust recorded, but also in amps. A stumax will pull a LOT less amps without an inlet lip, pretty pointless to set up your power system this way then find when you drop the fan into a model the amp draw is15-20 higher than you set up your batteries for. Example, my JTMHawk, tested the fan on the bench with inlet lip, then fitted into the fuse and the test results were within a couple % of each other.

Testing with an exhaust nozzle is also an interesting scenario, I have done quite a lot of testing of the same fans both with and without thrust tubes. The end result so far has been static thrust has remained the same, efflux velocity has risen (obviously) as has amp draw when the correct exhaust nozzle is fitted.

The FSA of the SM89equals approx 77mm dia. for the SM100 its approx 89mm dia.

As for running below FSA intakes, I have done that as well and experienced a drop in speed as the fan chokes, its funny all the theory in the world doesnt make up for real life experimentation. In my experience the more rpm you get from a particular fan the more volume it wants to consume (fairly logical) and the better it peforms with the intakes slightly enlarged. I tested this out in an F16 and flew it with barely 100% FSA with poor performance, lack of vertical power and speed. Opened the intakes up around 20% and the thing hammered and climbed out of a hover strongly.

And dont forget, these are my personal opinions, its not up for flaming or arguement, I go via what I experience during the course of testing/experimentation.

Charles, so things like metric to imperial conversion should be simple, google will give it to you instantly. 2.2lb = 1kg. 1oz = 28.35g. You are asking the same question over and over, its like you need to be told what to buy rather than advised what to buy.

The SM100 sounds the most logical choice as bigger is always going to be better for the same power consumption. The SM100 with a good HET motor on 10s puts out 5.2kg thrust, same fan on 12s pushes 6.6kg thrust. Oh and its 11 blades
Old 08-13-2011, 03:44 PM
  #12  
Avaiojet
Thread Starter
 
Join Date: Sep 2002
Location: Jupiter , FL
Posts: 3,157
Likes: 0
Received 6 Likes on 6 Posts
Default RE: Not a happy camper!

"Gimmie all eleven blades baby!"

I have to say, the information above has helped me greatly. Thank you so much.

Sure, I lack confidence, and it's obvious, I have absolutely no EDF experience.

With this kind of interest and this generous information, hopefully, and eventually, I'll be able to make my own decisions.

Thanks again guys!

"Gimmie all eleven blades baby!"


Old 08-13-2011, 11:51 PM
  #13  
Extreme_RC
 
Extreme_RC's Avatar
 
Join Date: Oct 2008
Location: , AUSTRALIA
Posts: 424
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Not a happy camper!

LOL fair enough you will get there, end of the day you want a setup that pulls the least amps for the most power out the back, its that simple and its what I have based all my own setups on, and those that I supply to other modellers.

Idid all the testing of HET motors in the stumax fans last year when the fans first came out, I have guys who fly locally running stumax 90's in foamies! Starmax F16 that one guy built is so quiet you dont even notice it coming at you until its right on top of you, its quite bizarre actually, must be the thick foam fuse damping out the fan even more than usual. I have video of it but need a new vid card in this PC so I can start rendering again, ongoing issues with computers that I just dont have time for has seen a lack of video posted in the last 5-6 months.
Old 08-14-2011, 07:54 AM
  #14  
Avaiojet
Thread Starter
 
Join Date: Sep 2002
Location: Jupiter , FL
Posts: 3,157
Likes: 0
Received 6 Likes on 6 Posts
Default RE: Not a happy camper!

you will get there, end of the day you want a setup that pulls the least amps for the most power out the back, its that simple and its what I have based all my own setups on, and those that I supply to other modellers.
OK!

Works for me mate!

Now, to progress with my airframe I need a bit of information?

Thrust tubes. Different but similar?

Through the help of others, I've determined that an average length for my airframe would be a comfortable 14" in length. or there about.

Any modeler, who may be using the 100MM fan, if this sounds incorrect, be sure to let me know.

Now using the Stumax 100mm Fan, "Gimmie all eleven blades baby!" The measurement I'm looking for, would be the size of the rear opening on the thrust tube? The diameter.

I'm altering the fuselage, and this measurement is important, for me to continue with building progress.

Thanks

Charles

"Gimmie all eleven blades baby!"

Old 08-14-2011, 01:52 PM
  #15  
speed is life
 
speed is life's Avatar
 
Join Date: May 2006
Location: Redstone, CO, USA
Posts: 390
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Not a happy camper!

Charles,
Happy to help here but you are asking us for hard numbers when you are doing a custom project......

The exhaust tube specs have to be determined AFTER you have figured the fan install. The fan install is based upon where there is room for fan and batteries -vs- C of G.

The length of the tube can be anything you want; diameter of the exhaust is up to the preference/experience of the builder. Usually the exhaust diameter is whatever allows ~80-85% of FSA. In the case of a 100mm Stumax this varies from say 77mm to 83mm depending upon builder preference.
Don't get all caught up in the Stumax100 idea 'till you no kidding figure out your inlet area then arrive at a fan to match.

As a new EDF interest I think it would be time well spent for you to spend a few hours looking thru old threads on RCG's on Stumax fans, as well as any discussion to do with FSA, intake areas, and exhaust areas. No amount of well intentioned advise given here is going to make up for serious research and self education.

Cheers,
Mike

Old 08-14-2011, 04:59 PM
  #16  
Avaiojet
Thread Starter
 
Join Date: Sep 2002
Location: Jupiter , FL
Posts: 3,157
Likes: 0
Received 6 Likes on 6 Posts
Default RE: Not a happy camper!

No amount of well intentioned advise given here is going to make up for serious research and self education.
The only research I have is right here. Same guys write that stuff!

I should just do a Q & A, but it doesn't work.

But here's the thing. Where are the scratch built projects that are apples to apples, as is my project? Why do you think I'm asking questions. Not for my good looks that's for sure.

99.5% of what I see in Threads, most are old, and I've been through many; That's why I started this one, the airframes come right "out of a box."

Also, what I read in Threads, that information I can also get first hand from the individual that placed or Posted it, as I stated, AND here's the plus, we could hold a conversation. Yes, I know, that part is difficult.

So What's the difference. I'm not asking difficult questions for someone to answer that has been involved with jets.

You'd be surprised what I could do with a good solid answer that is correct.

Also, most Threads are loaded with information about smaller fans in Foamies, and 90MM fiberglass airframes which come right "out of the box," my project, and I'm not building it up to be greater than what it is, is not quite that. Apples and oranges?

This is why I inquired and asked for information on the L-39. That airframe has similar moments and areas. Having information about that airframe can be useful. The info is hardly coming in and there's dozen of those jets flying around. Dozens!

Incidentally, sure the 100MM Stumax fan may or may not work, and I'm considering this, but I hope it does. I believe the 90mm
Stumax Fan only puts out about 6lb of thrust? I read that in a Thread. True or false?

BTW, the CG is easy, that's all aerodynamics 101, I've already done this. Placing stuff so the model balances on the CG, that I've been doing for a long long time also, with other scratch built projects. However, and as I said, I've been asking for info on the L-39.
Learning is having information, correct information.

Look no harm in asking for information, and I can't control how fast or how slow it arives.

OK. QUESTION.

For those that have the Stumax 100MM fan. Could you please tell me the fan measurements? Also the length of your thrust tube, the diameter of the rear opening and the airframe you have it in?

As I said, you'd be surprised how this information will help me. Four really simple questions, just read the inches of a yard stick, how difficult is that? Now, let's hope I get it.

Thanks,

Charles

"Gimmie all eleven blades baby!"

Attached Thumbnails Click image for larger version

Name:	Zx71244.jpg
Views:	32
Size:	70.6 KB
ID:	1648894  
Old 08-14-2011, 08:45 PM
  #17  
MaxThrottle
Senior Member
 
Join Date: Jan 2003
Location: Barrie, ON, CANADA
Posts: 281
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Not a happy camper!

You know an expression old shaman often reply with, "But you are asking the wrong question". Until you go and read you may ask and get an answer even build the wrong thing but may have asked a question that doesn't suit the model you have sitting there. What's your EDF position from the tail. What EDF suites the model or will even fit. What batteries and fan will you be using on what motor. The answers to these can change the thrust tube.

You asked and received replies, "you seem to need to be told", another directed you to sources that covered very clearly understood known principles regardless how old (there hasn't been a change in the laws of physics) via "Klaus Scharnhorst as well as "clausxpf".
This is important because what you are asking has been asked and answered before from both theory and real world. Asking the same questions all over again, how do you know you are getting any credible answers? Klaus and Claus spoke to a wide range of the EDF community and many derived a set understanding from their discussions.
But you're back to asking about conditions for a Stumax 100mm without answering if it actually suites the inlet catchment that you have already in place on the model. To optomize you need to know that before you ask what shape your thrust tube should be because the first answer could alter your question.

If your inlets was designed for a 61 and are smaller than usual, while you may get a results from stuffing a 100, something else may have been better suited for the inlets that could entirely change the dia of the fan and thus the thrust tube.

Take a quick glance at the Velocity site that shows simple diagrams on duct design [link=http://www.velocity-rc.com/cgi-bin/vrc/tech/list.cgi?action=det&tid=2&cid=&idx=1]Ducts for EDFs[/link]. This would be one of Claus's commentaries on duct design. Its not an absolute because at times we have to yield to the scale design and make some exceptions.

Mark/ExtremeRC is a good source for real world performance. I touch stone most of my purchases off of his commentaries and Data; But he'll still need to know your actual duct design.
Old 08-14-2011, 11:05 PM
  #18  
Avaiojet
Thread Starter
 
Join Date: Sep 2002
Location: Jupiter , FL
Posts: 3,157
Likes: 0
Received 6 Likes on 6 Posts
Default RE: Not a happy camper!

But you're back to asking about conditions for a Stumax 100mm without answering if it actually suites the inlet catchment that you have already in place on the model. To optomize you need to know that before you ask what shape your thrust tube should be because the first answer could alter your question.
Max,

Take a look at Post #7.(Edited, I had Post #6.) Here, I'll repeat it.

Haven't done the math, but they measure, 4.25" in height by 2.125" wide. Yes, ovals.
What were you saying?

Also, I've been told that the length of the thrust tube can be a "number of given lengths" depending on where the fan is mounted.

For those individuals that have never designed a scale model airplane before, I'll give you, some information.

First, I'm altering and redesigning parts of this model. If you followed my other Threads, you will know that this model was originally designed for a prop. Well, things have changed. I can now take advantage of the actual aircraft's lines and scale them.

With this said, the "scale openings" are listed above. However, I still have control over them, that is, I can increase the size a bit without destroying the scale appearence.

Now get this, and I know this is hard to grasp because, based on the replies I'm getting "instead" of the information I'm asking for,

IF THE MODEL WAS COMPLETED, I'D HAVE TO DO WITH WHAT I HAVE. This you have to understand because any model "Out of the box" falls into this catagory. It is what it is!

Well hey! I'm the designer, I can still make any change I want because the model is still under construction. "Still under construction."

The information I'm asking for is just "general information" so I can continue with the progress of completing my airframe. Again, not hard to understand, even for someone who has never designed a model airplane.

My suggestion would be, especially if you really want to help, to simply answer my questions.

This would allow me to make judgments, form conclusions and continue building my airframe.

Once the airframe is completed, kinda like "out of the box" choices for the fan and other needed accessories can then be made. Not hard to grasp that either.

So, as I said, you wanna help, then just answer my questions.

Hey! You guys having fun with me by not giving me the straight simple answers I'm asking for?

Charles

"Gimmie all eleven blades baby!"

Attached Thumbnails Click image for larger version

Name:	Rp44757.jpg
Views:	35
Size:	36.6 KB
ID:	1648947  
Old 08-15-2011, 08:28 AM
  #19  
speed is life
 
speed is life's Avatar
 
Join Date: May 2006
Location: Redstone, CO, USA
Posts: 390
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Not a happy camper!



[X(][X(][X(]
Old 08-15-2011, 09:25 AM
  #20  
Avaiojet
Thread Starter
 
Join Date: Sep 2002
Location: Jupiter , FL
Posts: 3,157
Likes: 0
Received 6 Likes on 6 Posts
Default RE: Not a happy camper!

Speed is life,

Sorry I struck a nerve!

Let's take your reply a step at a time.

(I dont think you know just who has or hasnt the experience......)
Of course I don't know who has "scratch building" experience, or who does.

(umm....what is hard to grasp is you talking down to this group of people that have real EDF experience)
I'm not talking down to anyone. And you're editing my context. I was referring to those individuals that have none or little scratch building experience. Nothing wrong with that. EDF experience has nothing to do with scratch building experience.

(you are not asking "questions" you are asking for hard answers... and sometimes there arent any?)
Well, sorry you find the following difficult to answer: I'll repeat my question, "For those that have the Stumax 100MM fan. Could you please tell me the fan measurements? Also the length of your thrust tube, the diameter of the rear opening and the airframe you have it in?" There ya go!

Possibly I should have phrased it differently so the question could be more easily understood?

"wanna help"? .... this isnt a "hot stove gossip session" most guys here dont have time to hold somebodys hand and just tell them how to do something that has 101 ways to get it accomplished - there are not any "straight simple answers" to the questions that you have posed ie:"14" tailpipe" - for one instance.
"gossip?" Where does that come from? I'm asking spicific questions. And that 14" length thing was a "statement" and not a "question."

Sorry Charles, you are coming across as someone you likes to lecture a student..........or maybe a frustrated retired drill instructor.........realise now that YOU are the student and your demeanor is no way to encourage guys to want to "help".
Get yourself to the forums and READ.....a lot........your answers are there to be found and you will increase your knowledge base far more that simply getting led by the hand thru the process.

BTW, I never figured out how you thought I had a small L-39.........
and drop the "58 years of modeling" thing, we have all been at this awhile. This gig isnt our first rodeo.
The only issue I see with Rodeos. is that it's all compitition. I see no team effort. My 58 years of modeling has taught me the importance of team effort.

I do appreciate your involved reply, and thanks for your help.

BTW. Do you have a Stumax 100MM Fan?



Attached Thumbnails Click image for larger version

Name:	Qo41331.jpg
Views:	35
Size:	307.6 KB
ID:	1649082  
Old 08-15-2011, 10:22 AM
  #21  
MaxThrottle
Senior Member
 
Join Date: Jan 2003
Location: Barrie, ON, CANADA
Posts: 281
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Not a happy camper!

If each inlet is 4.25" X 2.125" that works out to an area of about 4576.201921196805 sq millimeters (just do a google search type in calculate area of an oval or circle etc and enter your figures). Times this by two inlets and you have a inlet area of 9152.4 sq mm. The area of a 100mm is 7853.98 sq mm. So your 100mm stu is 85% of your catchment. When you measured that oval was that in the duct or at the lip of the intake?
Either way you may be better suited to use the [link=http://www.stumaxaircraft.com/pages/SM110.htm?t=739147]Stumax 110-52[/link]. A 120 may also work if you duct is straight and long enough. Asking dimensions etc... check the manufacturers website can answer that for yourself. AND YES you'll be happy to know it has 12 blades.

To your thrust tube question, only you know how long your tail is from the EDF placement, which is your choice, but if you use the 110mm, then 85% of the 110mm is 93.5mm. But you may not need the added efflux and could use more thrust and thus could do this as 90% or about 99mm since that model isn't intended for speed. Still you're the builder so its your choice. From the link and your model you can deside if its better suited for 10, 11 or 12S and how many Kilos of thrust you actually need and the type of performance you are looking for to determine how many horses you intend to put under the hood.

Note what I put in this answer was already answered to begin with, I just did the calculating for you. And a model is what it is, absolutely. I could get a 90mm model but if I start asking questions about a 70mm or 80mm or 100mm EDFs without calculating for myself the paticulars of the model in hand, you may be setting something up that is not ideal? Hopefully this helps you with why you may be getting odd answers. Only you know your model and it seems you're looking for us to do the calculating for you or you are asking something that we thought we already answered. ???????

Hope this points you in the direction you're asking.

Oh and if you want more intel on the Stumax 110 the link I provided has links to the RCG thread discussing the unit.
Old 08-15-2011, 10:32 AM
  #22  
harralk
My Feedback: (22)
 
Join Date: Sep 2004
Location: Ft Collins, CO
Posts: 127
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Not a happy camper!

Charles,

I hate to be a kill-joy but this may be one of those times where you just have to give it a try.  Are you trying to maximize the speed of an aircraft that hasn't been built yet by pre-selecting ideal components, which by the way have inconsistent performance specs, or just trying to get it off the ground to see if the hand-built structure is solid?  You can always change the fan out later if you don't like your first choice.

Also, not to sound like a lecturer myself, but it seems to me that if your questions haven't been answered there may not be any answers available.  Just buy a fan and hope it works with the understanding that if it doesn't work for this project there are plenty of other planes out there it will be ideally suited for.  You can always sell it as an almost new part and get some of your money back.  I haven't even started building anything yet for my project and I've already purchased two different fans.  There are just too many variables involved with this type of project. 

if nothing else, I can refer you to some of my engineering textbooks which discuss the theory behind things like fluid flow and how it relates to propulsion and with a post-doctorate level understanding of the subject you'll know exactly what you'll need to do. 
Old 08-15-2011, 11:28 AM
  #23  
speed is life
 
speed is life's Avatar
 
Join Date: May 2006
Location: Redstone, CO, USA
Posts: 390
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Not a happy camper!

The Stumax SM100-45 is $450.00 and this is fan alone. Yes, I have them in stock.

They are not "plug & play". I don't encourage beginners to try to go with such an advanced deal.


Old 08-15-2011, 12:39 PM
  #24  
Avaiojet
Thread Starter
 
Join Date: Sep 2002
Location: Jupiter , FL
Posts: 3,157
Likes: 0
Received 6 Likes on 6 Posts
Default RE: Not a happy camper!

Speed,

With all due respect.

You don't even know me or know what I'm all about. Click on Avaiojet. Take a good look at my participation with other modelers asking for advice. I answer all questions and don't beat around the bush. If I cannot answer a question, I'm not in there. I also have strong interest in other modeler's projects. Honest interest.

EDF's. I'm not the kind of guy that tries to reinvent the wheel. I'm asking really simple questions, all of which relates to a scratch built airframe.

As you can see by the replies, there are many modelers that answer my questions. I'm thankful for that.

RCU, and other sites like RCU, are comprised of Q&A. I see beginners and advanced modelers, asking and answering questions each and every day.

That's a good thing, and much can be accomplished by this. Can you imagine questions that go unanswered?

Experience. Nothing wrong with myself having little or no EDF experience. One must start someplace, it's that way with every endever imaginable.

Unfortunately, I cannot afford to start at the bottom with a series of small EDF projects, and I cannot afford to make mistakes.

That's the way it is and there's nothing I can do about that. Certainly I could put this project on hold, but it's been on hold for over 20 years.

Sure, I know it's not an entry level Jet. So what. That's why there's guys like you. Hopefully to assist guys like me.

OK, the signature thing. For years and years and years, I never had a CFC Graphics signature. I had no signature at all. I don't remember who, but I was kindly asked to place this information in a signature, by someone at RCU.

My guess is someone thought I was a Vendor hiding, and didn't have to take responsibility for my words. I've only had the signature in place for less than a year. When did I join?

Speaking of words. An interesting yet complicated way of communicating. The lack of corresponding in person, words can and sometimes are read incorrectly.

I'm not beyond criticism and wouldn't want to be. I try my best to live my life with humor and I introduce humor, in conversation, whenever I have the opportunity. RCU, is a great place for seriousness and a great place for humor.

Look, I appreciate whatever help and advice anyone is gracious enough to give. I've proven that with each and every thank you, I've said, over the years.

And Speed, thank you also for just taking the time to reply. That, in itself, is a good thing.

Charles
Attached Thumbnails Click image for larger version

Name:	Nl30017.jpg
Views:	34
Size:	44.8 KB
ID:	1649126  
Old 08-15-2011, 03:35 PM
  #25  
Avaiojet
Thread Starter
 
Join Date: Sep 2002
Location: Jupiter , FL
Posts: 3,157
Likes: 0
Received 6 Likes on 6 Posts
Default RE: Not a happy camper!

OK, Here's the latest update on my airframe and some conclusions.

Thrust tube length. 14" to 16" long.

Fuselage rear opening. 3.125"

Wingspan. 48.5"

Wing area. 424 sq inches.

Wing lifting area. 384 sq. inches.

Length. 56"

Fuselage thickness at widest point. 7.75"

"Out of the box" empty weight. 3.4 lbs. This weight will decrease some as construction continues.

Retracts. Electric only. Brand, undecided, to be determined.

Nose wheel size. 2"

Main wheel size. 2.5" to 2.75"

Fan weight. Undetermined, depends on Fan and setup, but placement is well aft of the CG.

Fan. Airframe will except 90MM to 110MM easily without installation issues. The 110MM is probably larger than needed and a bit excessive in weight.

The 90MM is probably a bit small but may be adequate.

The 100MM appears to be a good choice.

Leaning towards the Stumax 100MM Fan. If I use a 10 cell pack of 40C lipos with the Stumax 100MM fan/motor combination, set up by the supplier, my guess is I'll get about 4,5kW of power from it. A guess.

Other operational accessories, to be determined.

Well there you have what I've come up with. All conclusions were formed from information received from generous modelers and Vendors!

Obviously, my effort has been focused on completing a generic airframe, of a given size and dimensions, that will adapt itself to a variety of Fan and motor combinations.

If there's something here that doesn't sound right, please let me know.

Few photos that will tell, some of the story, as to where the construction is currently at.

Thanks for your help.



Attached Thumbnails Click image for larger version

Name:	Jh15760.jpg
Views:	40
Size:	131.1 KB
ID:	1649195   Click image for larger version

Name:	Yt62308.jpg
Views:	39
Size:	91.0 KB
ID:	1649196   Click image for larger version

Name:	Kp35181.jpg
Views:	37
Size:	174.8 KB
ID:	1649197   Click image for larger version

Name:	Ex68906.jpg
Views:	34
Size:	215.7 KB
ID:	1649198   Click image for larger version

Name:	Do81098.jpg
Views:	27
Size:	135.9 KB
ID:	1649199   Click image for larger version

Name:	Ri70286.jpg
Views:	41
Size:	118.7 KB
ID:	1649200   Click image for larger version

Name:	Ik91401.jpg
Views:	29
Size:	207.8 KB
ID:	1649201   Click image for larger version

Name:	Xv63654.jpg
Views:	39
Size:	99.5 KB
ID:	1649202  


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.