combatpigg

My Feedback: (3)

A single HS65 servo to control both ailerons is a good way to go if you are just after basic roll control and limit the ailerons to an easily managed size. The torque rods can be made from 2-56 threaded pushrods. Grease the pushrods, mix up a batch of epoxy and fine sawdust and inbed the torque rods in "ditches" that you cut into the wing's trailing edge stock.
I use clear packing tape to cover the epoxy slurry until it dries, so that it looks like a "finished product" after it cures.
It doesn't take much aileron throw to get the job done, so set up the mechanical linkage so that it gives the servo maximum advantage / leverage.

Japanman

Hey Rick,
I'm really glad to see you are persevering with this, after all the work you have put in.
I think it is timely to remind you, that you're out there pushing the boundaries of what is possible with your project.
Now would be a good time to go over everything and see if you can lighten any of it. If the spinner is heavy, maybe it could be lightened? Could you make a snub balsa one, or run it without it?
Is the fan itself heavy? If you give me it's dimensions, I could check it against the fans I have for a match, for something lighter.

I think a good rule of thumb might be to consider that everything in the plane will need to be about half the weight of a "sport" plane to fly well.
See what you can do to lighten up the construction- I get the impression that the plans are a bit chunky- could you use thinner wood for parts yet unbuilt?
I think you should approach this like you are trying to place in the free flight national championships.
I like C.Ps ideas about servo size and setup- I'd go for about 9gm servos and a light rec and battery.

Stefan

RickP

My Feedback: (2)

Thanks guys,
I ordered three servos. I can't do strip ailerons in the traditional sense because the DF unit is right under the wing root and I don't have room for it. The original plans show flex rods through the wing, but am afraid that's going to be too sloppy. I just ordered from tower, and now I am wishing I added in golden rods just in case. Well, I can always order again.
RP

RickP

My Feedback: (2)

Hello Stephan,
Thank you for your comments and encouragement! I still owe the list here a weight on my motor, I keep forgetting to bring it to work. Under the spinner is an adapter, it is made from steel and quite large and heavy. No reason for it. It could probably be aluminum. Maybe I can try to find a replacement for it. The spinner itself I don't want to touch. It's pretty close to perfectly machined and I also think the shape is important for air flow into the fan based upon all of the archived design data I could find. If I do anything it will be just to replace that nut. I don't have a lathe so any turning work for me is difficult to come by. If I could find a way turn down the nut I already have and reduce some of the extra mass that might be fine.
RP

Mr Cox

One servo for the ailerons is certainly enough, having two would just add extra weight. The current draw from the battery goes up too (in a two channel plane it makes quite a difference on the battery time). I've used similar designs as the one CP shows above, but there are many ways to do it.

Here is another way that works if there is not enough space for the pushrod solution;

airraptor

My Feedback: (66)

Rick,

I am sorry to tell you but your inlet ring is killing your thrust. That ring needs to be a bell shape not a thick airfoil cross section like you have.
Also at a minium the exhaust tube needs to be 90% less than the fan rotor size.

Stop building now! Go over to the dark side and read all the Electric ducted fan threads on intake and exhaust ducting. Like I said your intake ring is a restrictor not a flow "helper".

Follow CP's stuff o nthe 09 as fans need rpm.

Also you may have great thrust with that now but as with all planes static thrust on the ground doesnt mean anything except on an air boat.

If I was doing your project I would use my specktum telemetry airspeed to measure your Efflux speed of the ducting. I think most of the guys say you want around 40-70% more than your flying speed. I would trim the width of the blades down till you at least have 20,000 rpm.

Also another mith in this thread is that the engine will not unload in a ducted fan. also sometimes on these ducted fans the once the plane gets to flying it may actually load the engine more which makes since. Airplanes with over square props do this also as they will have a higher rpm on the ground than in the air.

Go buy some thin pva or plastic sheets from hobby store and wrap them in different exit diameters till you have a good amount of airspeed. Fix the inlet bell.

And one last thing most EDF planes loose some thrust when its installed in the plane. Very few high end EDF planes dont loose thruse installed in the plane.

I wishI seen this earlier so I could have helped you out.

combatpigg

My Feedback: (3)

raptor, it sounds like you have really done your homework..!
I had no idea that the EDF community had advanced this science to such a fine degree that you could pick up so much info from "tuning into" those forums..
It looks to me like Rick has a lot of time invested in a really nice project that can be fine tuned at this stage to make all his work pay higher dividends.
I don't think it is ever too late to make changes like you mentioned.
The basic .09 engine should respond to the usual TD .049 mods without sacrificing any torque.

Jaspur_x

My Feedback: (1)

I havn`t even started my 1/2A ducted fan project yet, but I`m dtill reading up on your project and glad you are sticking with it

airraptor

My Feedback: (66)

I just dont want him to give up.

I bought a Kyosho F-18 15 size DF. The stock engine that came with that plane had less power than a LA 15. So I ordered a OS 18 car engine and converted it to this set up. On the supplied pipe it would spin a APC 6.5x6 pylon prop at just over 25,500 and it spun that fan at 26,000. once it was installed in the plane it had a ton of thrust almost three pounds. by the way it was a 90 mm rotor. well I taxied out to take off. this the accelerated so fast it was crazy but soon as it reached 19-20 mph it wouldnt accel anymore. So I got on the net researched this plane and they made a thrust tube for this plane that came out as a mod from Kyosho. I tried to make my own thrust tube and after a a couple of weeks I gave up. This plane doesnt have any intake ducting or anything. I have started working the ducting but very hard on this plane as the servos, fuel tank and all are in the intake. I have been reading a lot since then.


So Guys dont give up keep trying. make the changes I suggested. Keep it light also.

RickP

My Feedback: (2)

Dear Airraptor,
I have to admit, this comment made me LOL. Have you seen how long this thread has been ongoing for???? Like yelling at a snale crossing the road!!

Much thanks for your input. You are absolutley correct - I went over to the EDF forums but they just didn't get the jist of this project and the 1/2a guys have been tolerating me so I've set up camp here.

I shouldn't neglect things like the inlet design you guys are using - however, realize I am only running at a fraction of the RPM you guys are turning so I'm not sure how effective the designs you guys are using will work for me. Back in the day these guys tested all sorts of inlet shapes and came up with these things. That said, I'm not convinced I understood it right so I'll take a look at the whole picture again and reconsider the inlet. The inlet is not really fitting well in my fusealage anyway.

The tail pipe I am confident I have nailed correctly though. The literature I have read makes it purely a geometric calculation. Fan blade swept area is equal to the exit area plus a little. Any contraction at this RPM is a thrust killer. This I am pretty sure I have correct.

I'm not going to give up. It's really all down hill from here anyway and I appreciate all of those who have stayed on board and helped with comments.
RickP

airraptor

My Feedback: (66)

rick are you saying your exit dia is larger than your fan blade dia? if so this the oposite of what you need. Yes you will lose thrust some on the ground but it more than makes up for it at flying speeds.

My fear is that you will make great thrust on the ground and maybe get it in the air but it will not accelerate any. Kinda like a boat with not enough power and it will not ever plane out.

IE: 90mm fan will have around a 70-80mm exit.

Now I know this one is limited on power so you cant go to small on the exit asd the engine cant compress the air some.

I would like to try this one day but I think I would go with one of the super expensive fora type engines that can turn up to 35,000-40,000 rpm and run a smaller 55-60 mm fan and then use two of them.

Anyway good luck and I hope you guys succeed with this.

RickP

My Feedback: (2)

I am finding that all EDF inlets are zero entry constriction on the inlet side. It's been so long I am not sure how I wound up this way. I spent some time at the HIMAX booth at the WRAM show this weekend looking at them. I'll put in some study time on the EDF forums and the old plans I was studying and see what I can come up with.

I bought more balsa blocks and am going to carve a new inlet (also one which fits my fuse better!)

Getting closer LOL.
RickP

Max_Power

I wonder if anyone has tried to use one of these fan units http://www.horizonhobby.com/products...ed-fan-EFLDF15 and tried to convert to glow? I saw them at my LHS a few months back, there are several sizes and they are pretty affordable. I'd like to have one in my hands to investigate further. they are just the fan and do not come with the motor as pictured. Not trying to sidetrack the thread, just though it might be the place to see some thoughts on this. Rick, I do understand where you are going and what you have is definitely a cooler project. I admire all the hard work you have in this thing. I'm sure you'll nail it in the end! Have you considered putting your fan on top of a foam hand launch glider to field test it a bit? Poke a few servos in the foam and see what it can do, then use the data to finish your airframe? One thing for sure, when you get this thing flying EVERYONE here is gonna wish they had one! Lol. Todd

RickP

My Feedback: (2)

Hi Gang,
I figured it's time for an update. Here are some construction photos - I've been doing alot of sanding. Kind of holding back a slight bit. I really need to get around this inlet issue. I mail ordered new blocks so I am waiting for those to arrive so I can start carving them out. I reviewed the previous literature I used and indeed I found the reference that inlet area should be equal to fan blade swept area. However everywhere I look I really see fans that don't choke the inlet. I'll study some more this weekend and make up my mind. In reality we are talking about such little thrust I don't think it's going to have a huge impact anyway.
I decided agains running a pushrod back to the elevator. The HS-65 is light enough to just mount under the stab.
I weighed the motor finally. 238g (8.4oz) complete. The adapter nut under the spinner is 15.5g alone. I figure I can easily cut that in half and get the overall weight down to 230g. Either way I have to come in under 2lbs final flying weight (gulp). I'll do my best...
RP

juanjulian

My Feedback: (9)

Think you will be fine with hs55 servos, save money and weight. They use them in low powere edf.

In EDF the intakes needs to be same or more as fan blade area, and the aft ducting reduces to a max 85% of fan blades area.

I recomend to, to shoke the aft ducting to at least a 90-95% to start with.

When running a edf with and with out a inlet ring is a huge diference in thrust. The inlet ring that come with new 70mm edf have a radius of about 5mm. The shape si not round but a elipse. I really don´t think your inlet ring is wrong.

Your don´t loose nothing trying other shapes.

Cheers

Juan

RickP

My Feedback: (2)

Sorry, for some reason uploading pics is not working today. I'll try next week?
RP

airraptor

My Feedback: (66)

max there is a lot working against ducted fans with glow power.. you need high rpm engines or really big fans to run lower rpm to get thrust but then you loose efflux speed and it doesnt go very fast. then you have a 70 MM duct with an engine that is 30-35mm wide and not streamlined at all.

max I would waste your money on that fan at all. if going to try this still go to Hobby king and buy 5-10 different fans for the same price as that fan and then play around with them. I am not trying to keep you from trying as with anything in this hobby many things can be done, just dont hap-hazardly jump into it as many MFG's with big money have already tried and didnt succeed.

here is something to think about...

that 69-70 mm fan needs to spin around 35-40 rpm to work well. to get there you will need some power. since our engines dont rev that high and make power you will need to gear an engine up. So take a 40-46 sized bushing engine and use a belt drive to get it at 2.5-1 ratio. have the engine outside the duct. this will get the engine out of the ductiing improving thrust. the engine will need a bigger carb and some port and crank timing work. then run a Jett 25-35 size tuned muffler. I know I said 25-35 for a 4046 sized engine but trust me here.

anyway food for thought.

MJD

My Feedback: (1)

But this is not an EDF, it has a glow engine. Due to the vibration that is much more likely with a glow DF versus electric, I suggest using servos with a bit better gear train - HS65's perhaps. Of all the Hitec servos I have used in 1/2A size models, the HS-55 has the easiest gear train to strip of any of them. Total weight penalty is about 21g for four servos.

HS-55's may be fine, but I would be wary. I don't use them in 1/2A glow models anymore after stripping a couple of them on lekkie park fliers.

Max_Power

Don't worry about me wasting any money air raptor, I'm not planning on buying one of those fans....I'd just like to look at one to "investigate" out of curiosity. As it has a aluminum hub and there are a few sizes of these guys on lhs hobby store shelves everywhere for a few 20$ bills But you say you can buy 5-10 different fans from HK for the price of the one $30 eflite one? (Not even considering shipping and trying 10 setups and a few bucks each for hardware,etc. Honestly I personally think the idea of a 46 with a 25 muffler belt driven to a fan like this is a lot more of a fantasy than throwing the picture fan unit on a ASP.12 with no muffler on a venturi and seeing what it cranked out....even if it did only hit a 20ishK rpm? Sorry for getting your thread off course Rick, Im keeping my eyes peeled for your further tests on the Cox/kress based setups! Todd

juanjulian

My Feedback: (9)

I had them in a 1/2 stealth kit from house of balsa and a cox 0.49 with no problems for years of abuse. For sure this servo has not the strongest drive gears,but thisjet with the glow fan is only going to be cruising.

I really believe this project is going to work after all the fan only needs fine tunig.

I like this forum since is were the real builders are left in mostly all rcuniverse.

will post some pictures of my edf inlets rings.

juan

juanjulian

My Feedback: (9)

The fans from left to right are: Change sum (china),het europe, wemotec europe.
change sum 10 blades more load on motor and a a jet sound.
Het fan 4 blades, higher pitch but less load compared to change sum, sound like hair drier.
wemotec 5 blades, similar load as het fan, sounds like hair drier. The edf comunity says is the most eficient.




Here is a picture of my jet intake, this inlet is really eficient.

Exhaust picture shoked to aprox 85 %


Think the only design concern for inlet is to be round, and light.

Here is almost the complete build of jethttp://www.rcuniverse.com/forum/m_10...m.htm#10372036











aviation cartonjet

airraptor

My Feedback: (66)

all of those inlets dont not drop down in inlet size like the pictures of the guy in here. His inlet cross section is an airfoil shape. The dia at the fan is the correct but the dia mid span of the intake is smaller in Dia.

Also he said with the engine running the fan sucked the intake into place. not good.


MJD is correct also DO NOT use the 55 here. yes they may be cheap but how much is your time and effort in this plane.

As CP said the Hitec HS-65 is a very very good 1/2A servo. I prefer the HS-65HB as the gear train on it is strong enough to tip the servo horn off and not strip the gears. I have had a Saito 91 held on to a plane just by this servo and the engine was still running between mid rpm and idle and it moved around in the air.

max power yes you could throw a asp 12 on it and you might be able to get a light weight large wing plane to fly and that would be cool but but i would mess with it.

Oh and by the way the Kysho fan unit for the 15 size engines was 89-90mm size on the rotor itself.

MJD

My Feedback: (1)

They may be fine.. I am just cautious. I have used a lot of them, but I did have a couple go bad.

Japanman

Hi Rick,
I took a look at your pics of the inlet on the previous page.
I think the plans for your plane are wrong in this respect, like airrapter is saying, you don't want the inlet diameter to be smaller than the fan diameter if you can at all avoid it.
But a bigger issue here is actually how the inlet is setup. The plans showing the inlet in the fuse is a bad idea, the whole purpose of the inlet is to get air into the the beginning of your intake pipe smoothly. As you plane is, this is the beginning of the D shaped inlet on the fuselage.
From here you just need a blend to the front of the fan.

S

RickP

My Feedback: (2)

Hi All,
Okay, finally was able to get the pictures to upload.

I hear you all on the fan inlet. I got new blocks and will carve a straight as possible inlet for the fuse.

Just realized I have 30 days till the flying season starts, so I put all of this on the shelf to get my aerobatic planes ready. Hopefully it won't take too long. I hope to be done by the end of the week.
RickP