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Giant DF project on a tight budget

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Old 12-04-2008, 06:47 AM
  #1
jonastecknare
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Default Giant DF project on a tight budget

Hello, I have just started the building of a new project which have been on my drawingboard (computer) a few weeks now. The thing will be built at a scale of 1/5 and will be 125 inches long. The plan is to scratchbuild everything exept radio and engines. Oh yeah, its a Ductedfan!
I will also try to use a little different (and cheap) materials. Retracts will be homemade, but but rather different as they will be electrical.
The plan is to post some info on the build as i go. At times i have a rather high workload so building may take a pause now an then. But hopefully it will be airborne sometime next year (2009).
OK so what is it?
I can tell you its a single engine, deltawinged fighter.
Yeah right 125 inches DF single engine. No worry as i intend to stuff three of them (2 OS91 and 1 OS77) into the fuselage.

What is it this wierdo trying to do?
Well i want to make something totally avesome on a minimal budget, the engines i already have and Fans will be made.
Here is a pic of the fin. (The wheels in the background is 5 3/4 inches in diam)

Jonas
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Old 12-04-2008, 06:54 AM
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Default RE: Giant DF project on a tight budget

I have some trouble with the pic! It wont upload. maybe ill try a different computer.
Sorry
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Old 12-04-2008, 07:07 AM
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Default RE: Giant DF project on a tight budget

OK seems i need to use Exploder!
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Old 12-04-2008, 10:50 AM
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Default RE: Giant DF project on a tight budget

Hi Jonas,

Your Vampire in Laxå proved that a possitive attitude gives the best "lift"!

Good luck with your new, low budget project - looking forward to seeing what you come up with this time!

Pete
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Old 12-04-2008, 01:00 PM
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Default RE: Giant DF project on a tight budget


Quote:
ORIGINAL: petera38

Hi Jonas,

Your Vampire in Laxå proved that a possitive attitude gives the best "lift"!

Good luck with your new, low budget project - looking forward to seeing what you come up with this time!

Pete

Yeah man i was impressed by seeing it's video and reading about it, never imagined a 32pounder can be flown on single DF set up!!

Can't wait to see this new one from your hanger Jonas!...
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Old 12-04-2008, 01:00 PM
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Default RE: Giant DF project on a tight budget

Ducted FAn is still alive and kicking. Looking forwaard to your project
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Old 12-04-2008, 01:13 PM
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Default RE: Giant DF project on a tight budget

That looks like a Viggen vertical fin to me![:-]

Tailwinds,

John
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Old 12-05-2008, 08:18 AM
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Default RE: Giant DF project on a tight budget

Oh yes! Its a viggen! I think this is the only jet that looks as cool on the ground as in the air! (which means it will still look cool if it wont get of the ground! god forbid!)
The Vampire is covered in fibreglass, a method that works fine but is disgusting to work with. So i have been looking around for alternatives. Chris golds used brown paper on his giant machines in the 90s, i have tried that and it flew well but was heavy. Then last summer i rebuilt a kitchen and used some stuff on the walls that has shown to be really promising in tests. It looks like a mix of paper and fine fibreglassmatt, but it is a mix of polyester and cellulosa i think. I have to check again.
Anyway, you apply this stuff with wallpaperglue ( not the sort you mix with water) I will use 2-3 layers, then you sand it to remove joints and apply waterbased floorwarnish. Let it dry and sand again,then paint it with again waterbased woodprimer. Then wetsand to finish. Then im gonna paint it with acrylics.
On my tests this surface weighs 4gr / dm2 and is very strong. It seems to work best on pink or blue foam, but this foam is a bit heavy at 40gr/dm3 so what to do?
Well, i will try to make cores of whitefoam and then plank it with thin sheets of pinkfoam. Worked really well on the fin.

The engine setup is one i have never heard of! Which is why i had to try it of course.
There will be three engines with home made fans based on the byronfan but not pushers, I think it is better to have the engine behind the fan, Better for cooling and the glow clip wont jump in to the fan!
The two top engines (OS91) will sitt between the canards and use the real airinlets. The lower OS77 sitts sits in the bottom of the fuselage just behind where the wings leading edge meets the fuse.It uses two big cheater holes between the permanent hardpoints in front of the wing. All engines in front of the CG, very important to me as i had to fill the Vampires nose with iron plates. Dont wanna do that again!

Im gonna try to take photos and write about the build.

Jonas
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Old 12-06-2008, 11:00 AM
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Default RE: Giant DF project on a tight budget

Hello, I´ve had some qualitytime in my shop.
First pic is the bulkheadsthat will make up the joint between the forward and middle part of the fuselage. The thing is you dont need CNC machines to do this! I made these in 20 minutes with the tools in the pic. I find this work rather enjoyable.
Pic2 I started with the fin and now the nosecone, hopefully things will meet in the middle.
Made a lathe sort of for the pink foam. Inside is a carbontube from a scrapped tent.
he right bearng is simply a pianowire stuck into the carbontube. Cant use to much speed as it will oscillate to much. I use the sandpaper from a big floor beltsander .
Pic3 The shape is getting there.
Pic4 Not good enough, have to sand away more in the middle.
Pic5 Ok shape is good!
Pic6 Cut it apart and hollow it out.
Pic7 This is so i can stuff batteries and things in the nose. A M4 treaded wirte will hold the nosecone in place.
Pic8 Glued back into one piece with polyurethane glue.
Time to eat!

is this to many pics?
Have never done this before! (a building thread that is)
Jonas
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Old 12-06-2008, 11:41 AM
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Default RE: Giant DF project on a tight budget

Hello Jonas,

At mine opinion, Viggen is one of the most impressive jet ever.

Looking forward to see your Viggen build, for shure I would keep my eye on this one ! [sm=wink_smile.gif]

This would be a great project, and Viggen is quite complex aircraft, I know that from the first hand.

A while ago I also started to build it as smaller EDF version, I still working on a plug for mold:


http://www.flyfreak-hr.org/phpBB2/viewtopic.php?t=641

http://www.rcgroups.com/forums/showthread.php?t=494672


John,
Your Viggen is outstanding !
Did you also scratch build it ?



Very best regards,
Kristijan Kljucaric

.
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Old 12-06-2008, 01:33 PM
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Default RE: Giant DF project on a tight budget

Looks like your tight budget even carries over to your lathe
[sm=thumbup.gif][sm=thumbup.gif]
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Old 12-06-2008, 02:43 PM
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Default RE: Giant DF project on a tight budget

Jonas, The pictures and detail description of the work in each frame is VERY helpful. I intend to follow you on this build. I want to learn the techniques. My dream is to build a Boeing 757 with a 10 foot wingspan. Perfect scale is very important to me as I know every detail of the real one. I hope to find something substantially better than 3 views but so far not much luck. I have several other projects so the 757 is a ways off.
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Old 12-07-2008, 11:13 AM
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Default RE: Giant DF project on a tight budget

The idea is to get things done even if it means using a bit unusual tools and technices.
Havent managed to fget to the shop today yet, but i think i will dismount the byronfan in my vamp and measure it.
Then im gonna start making impellers and fibreglasstubes and stuff. I think i will hold of the really big things a while because my shop will be quite cramped when the fuse starts to emerge. I draw on this thing all the time trying out different solutions. Mostly i use an old verion of adobe illustrator,and sometimes Form-z.
I will try to post some pieces of the drawings. I dont claim this will be an exact scalemodel. I have really good documentation, but it is very tedious to use.
So this will be big, quick and dirty!

jonas
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Old 12-07-2008, 11:27 AM
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Default RE: Giant DF project on a tight budget

Here is some small renderins of the drawings. They are not comlete building designs, more like sketches but i could upload them if there is interest.
I have to see if i can convert the format somehow.
Jonas
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Old 12-07-2008, 12:11 PM
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Default RE: Giant DF project on a tight budget

Keeping those three IC motors running might be your biggest problem...geez i hated those piston engines.
V..
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Old 12-07-2008, 01:48 PM
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Default RE: Giant DF project on a tight budget

Holy cow......I have the Byron F15 and keeping two running was a challenge. Will you have problems with airflow interference. Will the exhaust be seperated orwil it be a single tunnel?
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Old 12-08-2008, 07:19 AM
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Default RE: Giant DF project on a tight budget

The engines will have completly separate ducts, both in and out. The outlets will even be circular, all to keep strange interferense to a minimum.
I will use OS91 and one OS77 on straight 80/20 fuel, no nitro. These engines have been very kind to me before! I wouldnt do this with Rossis though.
Somehow i dont think this will be my everyday jet, the hassle and trouble will be a part of the fun, If you can see what i mean? ( am i really that perverted?)
Also on the drawings it looks like all engines are mounted upright. Not so, The upper two will be angled at between 60 and 45 degres. (hopefully 60 but im not sure this will be possible)
Jonas
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Old 12-08-2008, 10:21 AM
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Default RE: Giant DF project on a tight budget

Quote:
The upper two will be angled at between 60 and 45 degres
Similar to this?

Have you worked out how you are going to start all 3 of them? It's a very cool project
Twins sound better than singles....I can't imagine what triples will sound like....unique I'm sure!


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Old 12-08-2008, 04:03 PM
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Default RE: Giant DF project on a tight budget

I think i know how im gonna start them! How it will work out in the end... who knows? The upper two thru the airintakes and the lower one thru the cockpit. glow thru big hatch on topfor all engines.
Yeah, its similar. I need to avoid harmonious vibrations,so all engins angled as far from each other as possible 120 degres. same thing as the lower straight and the others angled 60 degres each way. At least i hope this works! Never heard of it!
Made a plug for the fanblades today! out of MDF saturated with CA. Worked well. hope the carbonfibre/epoxi moulding will work also.
Jonas
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Old 12-10-2008, 04:57 PM
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Default RE: Giant DF project on a tight budget

I have a tip for you people who live near water. Try to buy carbonfibrerod from the people who makes sails. They use a lot and pieces shorter than 3 feet is mostly useless to them. Got a bunch from a local factory. 10mm thick and strong as can be.
Guess what i will use as wingjoiners? Im thinkin about making undercarage of it also, well see if i can figure i out.
Jonas
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Old 12-18-2008, 07:13 AM
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Default RE: Giant DF project on a tight budget

Hello i´ve been workin some on the fans.
I carved the plugg in MDF board,sanded this smoth and saturated it with CA.
Then i wetsanded and polished it until i was happy with it.

Next i made a "skirt" of balsa.

Covered the whole lot in monocote

Glued it at the bottom of a cardboardbox which was lined with vinyl maskingtape.

Then i waxed it, and then i applied some gelcoat, in retrospect i should have used more gelcoat. When this had hardened i stuffed the box with polyester/fibreglassputty.

middlepic shows the first half of the mould. Needs some filling and polishing but looks ok. need to work some on this and then im gonna make the next half.

Last is some moulds ive done before.Its rotor and statorblades for the Boss fan
The best is the green/yellow variant. Its made of ureol resin.
Jonas
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Old 12-21-2008, 07:48 AM
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Default RE: Giant DF project on a tight budget

Making the mould didnt workout! I think it was to hard, so when i tried to split the two moulds they just broke into pieces.
Have to redo, this time in Ureol which i know works.
Will probably start on vingcenter and landing gear soon. After seven versions of design i think i have something that might work.
Not as lowtech as i had hoped, will mostly be in metal.
Jonas
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Old 12-21-2008, 08:56 AM
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Default RE: Giant DF project on a tight budget

I'm following this thread with great interest [:-]

Are you familiar with hi-revving fan blades molding ? Hope so, otherwise they'll kill you !
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Old 12-22-2008, 07:40 AM
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Default RE: Giant DF project on a tight budget

The ones im making will be much stronger than the byronfan which it is based on.
and yes i`ve done fans before. And i will be very carefull when testing them.
Actually, everybody should take care with any fan or prop on these engines!
Jonas
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Old 01-05-2009, 07:00 AM
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Default RE: Giant DF project on a tight budget

Hello! happy new year!
In between Christmas and NewYear, i had a fit and redesigned the whole engine setup.
It seemed to me i had to little material in the wingjoin. Also i didnt really like having a large cheater hole.
So now i have one engine on top and two ones in the bottom a bit further forward.
Also i have enlarged the intakes some and designed new ducts. A bit tricky that was.
I have also managed to mould five fanblades which i am happy with and turn a nice hub.
Next thing is to cut slots for the blades, this is probably the hardest part of the whole thing.
I have also managed to Cut most of the bulkheads so now i am comitted to this engine setup.
Sorry no pics as i forgot my camera, will take some tomorrow i hope.
Jonas
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