Japanman

Hi..
those of you who have been hanging around here looong enough will remember that I am actually making a mig. Well. very slowly

Recently I actually started it. (the final version, that is) After mucking around with a bit of D.F stuff and engine stuff, I am confident that I can now put together a decent 1/2A D.FMig. (I have changed my mind and decided to make a Mig15- better wing configuration for models)

Well, naturally I started at the engine and have been slowely working from there. It will be powered by a V.AmkIIR/C (checkout kittingitogether.com if you want one) And myown D.F unit.

I made the Fan for the unit a few days ago- it is a 5 pitch and is moulded out of carbonfibre and epoxy resin. I discovered a quick way to do this using high density foam for the moulds- the shapes are all hot wired in so the pitch etc are reasonably accurate. Surprisingly I can get quite a good start point for the airfoil too. see the pics!

Japanman

Oh no... I can`t get the band width to upload the images [:@]

I`ll have to do it tommorrow.

J.M

Japanman

Here are some photos of the fan molding process. I managed to get quit a lot of fibre into the blades- four layers of carbon that compresses down to 0.3mm per layer in an ideal world, so in my crude molds getting the total thickness to 1.5mm is not to bad for fibre to resin ratio. As it stands, carbon fibres are so strong (approx 6times the strength of std glass fibres per volume) that this SHOULD be overkill. We`ll see if I`m right at 30000rpms

J.M

Japanman

O.K...
this is really a construction article. sorry if I bore you all.

Next I made the 'spinner' (lovely appropriate term). I was going to make the mould from chopstrand /polyester over a balsa male... but as it turned out my poly-wally had gone hard in the tin. Good riddence, horrible smelly stuff! I went out and got some plaster of paris- cost me about $3US for enough for 10 moulds!
I love this stuff for making quick, disposable moulds.

Japanman

You can see that the spinner has a few surface imperfections etc.. but it is easily good enough for what I want. I filled a few of them last night- all looking o.k.
You may also notice that the top of the spinner is grey- Thats because I lay two layers of glass cloth impregnated with aluminium loaded resin. This is supposed to improve wear resistance... we`ll see! I will be starting the engine via the nose cone so it is going to get a bit of stick.

J.M

scubyfan

Two questions:

First: Why didn't you buy a pre-made DF from some place like Kress Jets?
Second: I want to get started in using carbon fiber to make stuff. Can you recommend books, sites, materials, etc.? I have absolutely no experience!

Thanks for this thread: I will be following it closely.

combatpigg

My Feedback: (3)

Hey JAPANMAN, You are totally boring me with all the details of your work, I wish you would just find some place else to display this toy airplane of yours.[:'(].

Be serious, and I will be serious too, I am blown away by the genious of your work! I can keep a secret if you can. I won't tell anybody that you have started next years' 1/2A contest plane a little bit too soon if you give me a dollar! As far as I know, you are attempting to do something that has not been done, because the smallest commercially produced fan unit that I can think of was a KRESS .09 size fan. The percentage of CF to resin in the 1/2A props that I have seen is way below what you are doing, so yours should be plenty strong.. Have you been able to gather ideas about DF design from internet resources? You have a magazine level project going on, and I think you could make this hobby pay for itself a little bit if you submit an article to the RC magazines! Keep up the great work, this is going to be toooo cooool!

Japanman

Hi SF
Because I have not ever read any good things about the kress 1/2A unit (which I don`t think is being sold anymore). I have tried two comercially made units- the kyosho edf unit and the electric jet factory 709.

Both had their problems- and It took me a bit of experimentation to get a reasonable amount of thrust to fly with. Of the two the kyosho unit had the more appropiate fan... except of course that it was made of a non fibre re-inforced plastic[X(] I broke mine trying to start the engine one time and it came loose and too of the blades snapped clean off!!! No I DO NOT recommend it- it is just too weak.

The 709 unit had a whole raft of problems- so much so that I felt a bit dissapointed with it. The plastic used to mould the stators and engine mount (this is for electric engines) was really weak. And the fan, while strong, had too many blades- I was using a norvel .074 with modified porting and it was just too much for it. In the end I cut it down to three blades and got some goot thrust... but then the spinner developed hairline cracks. It may have been non resistant to the fuel- but I could not use it anymore.
So I ended up with quite a few odd bits!

After quite a bit of experimentation I made a four blade fan and ran it in the kyosho housing- still lots of issues, but with my norvel 0.061 and a pipe I was getting good thrust so I built a plane around it to go flying.

Have you checked out the composites area on RCU?
Get a bit of good epoxy and get into it! My only caution would be do a bit of a read about health and safety- I always wear gloves and never leave stuff to cure in a room where I`ll be.
It is also good to make a heat box- this can just be a cardboard box with a hair dryer (you can see mine in one of the photos) This does three things- it speeds up the cure, reduces the viscosity of the resin (lets you squish more out to get to get more fibres per resin- this is a good thing) And importantly it produces in my experience a much better (more complete polymerisation) cure- the cured part will be noticably stronger and harder. If you use west systems it makes a big difference- this is a good resin to start with, IMO.



Aw shucks, C.P, your are too kind about a rough guy like me. You are just being fooled by the low res photos!

J.M

scubyfan

Thanks for the info!

Japanman

Wow! this is cool!
Hot dang, I just got it on the motor!... After quite a bit of mucking around...

I was a bit concerned about the strength of the spinner, and its centrality of it and the fan- it`s all very well to balance the snot out of something, but if it is running .5mm off centre.. whats the point?
That is the main problem I had with my vampire d.f setup- a standard machine thread has about .1mm clearance built in- this makes it a bit wobbly in the crankshaft, and the X degrees it is out relates to 0.Xmm out of trueness. To get around this I am going to try buying a really long caps screw with enough unthreaded portion of the shank to cut a thread onto- then I`ll open up my die and cut a 'big' thread. hope it works.
Actually with the V.A I have a bit of a head start- the end of the crankshaft is slightly proud of the thrust plate- I have drilled a step into the face of the fan to accept it- hope it works before I have to do the the above

Today I managed to add an extra layer of carbon weave into the area weakened buy the cutouts to accept the fan blades- I also lay in a 'lip' of rovings at the edge of the spinner to really stiffen it up- it may only be 40mm but at 30 odd K the Gforces really start to add up.

Here are some photos of it all balanced and ready to go! Wahoo![8D]

J.M

Japanman

Hmmm...
I have had the day off today so I have had quite a bit of time to work on this..
Getting it ready to go on the engine was just not enough! I had to give it a run. So I set it up onto the engine on a test 'stand' (A block of wood that I hold on to)
In the setup I noticed two things.

1)
The fan hub where it comes into contact with the prop drive plate is out by about 1/2 a degree.

2) the engine prop drive plate is out by about 1/2 a degree.

This probably sounds like stuff all- It is, with a prop it is not noticable- however the spinner is two inches long from the prop driver, so a little out there makes it wobble enough vibrate quite a lot.

I was able to find a place where the two cancelled each other out. This is not good enough for a perfectionist like me- I could get it 'quite' central, but there was still a little vibration-..... read above posts[:@]....

I can easily trueup the fan hub to near perfect, but the prop driver is a more tricky matter....

At this stage I am thinking of how I could do it on the crankshaft I don`t have the measuring equipment to test if it is the splines on the crankshaft of the splines in the prop driver... so my best be I figure is to at first try it in a few other positions on the crank splines- they may both be out and I may find a sweet spot-

holy smokes! in writing this I have had an idea! Maybee a T.D prop driver would fit! I have one and it is definately straight... watch this space!


Anyway the good news is that the engine was very happy with the fan- That V.A is a beautiful engine.

J.M

Tim Wiltse-RCU

J.M.,


All I can say is WOW! You are working on something really neat here. I am looking forward to reading as you go forward with your project.

LAter,
Tim

combatpigg

My Feedback: (3)

It sounds like one of those deals where once you get everything together perfectly, you don't ever want to take it apart again. Ideally a DF crank would have a snout on the front end that acted as a pilot for the fan unit to mount to. I'm sure you will get it figured out, JM, it just takes more time and patience. When it's running real smooth you will be able to see your reflection in the spinner!

Japanman

Tim,
Thanks! I am afraid it is a bit too interesting- right now it is about all I can think about!.. know the feeling?
Actually my next D.F project will have a 'POWERED BY COX' sticker on it... What is cooler than that???

C.P
Thats what I have been DREAMING about[:-]- A crankshaft with an threaded end as part of the crank would be perfect. I believe the AP wasp 061 has a crank like this- Does anyone know if it is interchangable with the norvel crank? My norvel .061 has a crank pin that is nu nu`d and I need a new one....

Well, The good news is I put the V.A, fan and spinner, and 709 tube and stator onto the kitchen scales and it is 100g exactly- thats 25g lighter than the unit from the Vampire. Great! I am determined to finnish the MiG 100g lighter than the Vampire- It`s wing loading was too high- Mind you, 1/4 of the wing was taken up by the intakes, and I think they caused this section to stall at low speed... so if I can trim off 100g and I have this extra 1/4 wing to play with, I figure it should fly very much better at low speeds[8D]

J.M

ajcoholic

My Feedback: (10)

Hey JM, this is bloody marvelous! I cant wait to hear about the run tests...

AJC

Japanman

Update.
Got up at 6 this morning.. had a bit of time so I had a look at a few things.
Well, the bad news was that the splines of the V.A crank are different from that of a cox.
The good news was that I found that the slight runout from the V.A prop driver was from the knurling- so I took it off and carefully ground them down a bit on a cool diamond flat steel I have till there was no high spot. Then I slightly deepened the grooves with a diamond file. Put it back together- looks pretty dang flat and true now... With no DTI I can`t say for sure though. I`ll have to get my BTW (BenT Wire) gauge onto it. nothing but high tech here, man.

I trued up the back of the fan.. Well, it was pretty flat actually. Hmmmm

I am going to try to get to the model shop today. Hopefully they`ll have my 40% nitro fuel that I`ll use for blending up some 20% nitro fuel. I`ll get a long caps screw too.

J.M

ptulmer

My Feedback: (5)

JM,

Looks like your becoming an expert on the 1/2a fans! Really nice job. Now that I've given the compliment I have a question. Where there specific reasons for not using the kamdax unit? I was looking at the one on Tower and it can be bought with or without engine. Just wondering because I've been thinking about scratching something out with one.

http://www2.towerhobbies.com/cgi-bin...?&I=LXFHE8&P=V

Japanman

Pt,
There is nothing like doing it yourself!
I did think about it for a while, but myown experiments with different fans etc seemed to show less blades are better..
It is also a fairly pricey unit- For me, in the end I`d rather try to make something myself with a few of my own ideas to try to get as much out of the power the engine is putting out.
That said I see that the kamdax unit works very well in their models, so I see no reason why you shouldn`t get one and scratch build something around it.
..................................
Wasn`t Andy W making a pipe for someone with a kamdax MiG? How did it turn out?

... The model shop had no fuel for me.[].. MAN! getting some castor of even mostly castor fuel here seems impossible!! Maybee I`ll have to switch too 0% nitro homebrew SOCHU and castor!!

J.M

combatpigg

My Feedback: (3)

HI JM! If you have any circle track or drag racing going on overthere, it might be a good idea to buy raw fuel ingredients from one of the racers or suppliers. I think even high end go carts run nitro/methanol/klotz/caster oil. I was able to get pure nitro for $33/gallon and methanol for $6.50/gallon[I thought the methanol price was kind of high]. As far as the interesting projects are concerned, this one is right up there with AJ's SENECA and you are doing a great job of keeping everybody filled in as to how you are doing! Once you have led the way with this DF project it is going to create a lot of interest to duplicate what you have done, and those DF units should become pretty fancy "trade bait"around this forum! [8D][Hey buddy, need someone to clean that plane when you're done with it?] I would love to have a 1/2AF86. My old ACE RC GLH looked like a F86 from a distance, and sounded pretty good with a 24K ground rpm TD! I used to look at those KRESS ads and wish they had a 049 model! Once you get the power package sorted out, the airplane part becomes almost secondary. I would like to think that it is possible to do a design where the wing does NOT pass through the fan housing?

Japanman

C.P,
I thought Kress made a 1/2A unit? I read somewhere about someone sticking in a T.D and getting lots and lots of noise but not much else! (what, noise from a T.D?) Maybee it was a TD09.

Yeah, I really like the look of sabres too- to be honest I was very tempted to make this a sabre- mostly because kamdax have'done' the MiG... But I figure I can do it better[8D] Besides, I think the Mig15 was one of thise genius designs of it`s time (I`ve been wanting to make one for years)- not that it was strictly orgional or anything -from what I read there were several planes of similar configurations on the drawing board before MiG.
So by all means make a sabre- then tootle over to Japan and lets do some streamer 'hoovering' No need to worry about prop damage!
... Japans a funny place for stuff like nitro- I have the castor and methanol... I have ONE more lead to follow up to get some nitro before I ask you to bring it over in your drink bottle!

For designs where the wing misses the ducting, how about a corsair? They are powered by a turbofan (I think if my 8yearold memory is to be trusted) so the intakes etc are of more appropriate size.

J.M

ptulmer

My Feedback: (5)

JM

I know what you mean about doing it yourself. I think I would need yourself to do this one first. Are you really only 8 years old?

CP
The A-7 Corsair II is the one I was looking at. Check out the line drawings offered by Vought for free. http://www.vought.com/heritage/ The F-8 Crusader is another high wing. My favorite was the XC-142A. A four engined Osprey!?

combatpigg

My Feedback: (3)

HEY PTULMER! That's a gold mine of stuff there! I like the looks of the early jets. It's amazing how well preserved some of them are, they are restoring a SKYRAY at a local museum and the anti corrosive paint did quite a job through the years. What a job to unbuild a plane rivet by rivet, then rebuild it. I think CHANCE VOUGHT gets overlooked somewhat by modelers but they have some very worthwhile looking designs to model. BTW, JM is 8 years old, but he got held back in the 3rd grade []because this science project he is working on here didn't have the 30:1 power to weight ratio that was required to move on into the 4th grade!

Japanman

Pt.. thanks for the great link... I was also meaning the A7- But there are a bunch of obscure ones there that would be fun too. (there would be nothing like turning up to your field with not only a 1/2A jet but one that no-one knows!)

I have found the bogey stopping me from getting the fan on straight- the thread in the crankshaft to take the prop screw was out by a tiny bit- so I made a screw with a 2mm neck right by the thread to let it flex- other wise it was fighting the fan and pushing it off to one side-

I also replaced the phenolic thrust washer with a paperthin teflon one- this lets the prop driver sit down further onto the splines, making them come through further. I deepened the hole that accepts them on the back of the an and now almost everytime it sets up very true. I gave it another test run and it was MUCH better- almost no vibration to speak of... even on the pipe[sm=thumbup.gif]

J.M

Japanman

Update... Wahoo #2

Our little boy kindly woke us up at 4.30 this morning... so after he and my wife went back to sleep, what else was there to do but work on a 1/2A ducted fan plane... I mean, who reads books anyway? Thats for nerds right?

Well, to cut a long story short, I now have the complete unit - tank, engine, pipe, throttle rah-de-rah all plumbed and shoehorned in.
I finished the tank yesterday- it is actually one I made for the .074 so it is a bit big= good in my books. I don`t like to run out of juice just when I am starting to enjoy the flight!

AND....(drum roll)...
I have just test run it. All I can say is that it ran very well- no vibration to speak of, excellent needle, decent thrust.. all in all looks good enough to start throwing together a plane to stick it in!

The only odd thig was the engine was running quite hot- it wanted a 1/3 extra turn of the needle to stay cool- lucky I have that big tank
I unfortunatly discovered this the bad way of having the engine overheat and stop once. Dam. I was a bit caught out because it was a bit on the rich side anyway.

Other little detail is I got to use some of the cool 2mm silicon I got in Osaka... look at it bend... no worries with inverted stuff for this baby[8D]

J.M

scubyfan

That looks great!

Quick question: why do you have both the engine and the muffler (?) terminate in a smooth cone-like shape? If you don't have the ends that way, will you see a reduction in thrust? Is it worth the extra weight?

I hope I'm not upsetting you with my questions. I figured this would be the perfect opportunity to ask a question...or four.