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Old Jun 02, 2010, 08:04 AM
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NickM91's Avatar
Australia, WA, Perth
Joined Jan 2009
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Boeing 777-200LR Twin 90mm project

G'day,

I've long had an appreciation for the 777, especially the stubbier variants, and since picking up EDF fever I've wanted to build one out of depron.

The last few weeks i've set about figuring out exactly how i'm going to build the thing and after much research, headscratching, sketches and simple models ihave come up with an uncomplete set of plans, the wing design is mostly done, but the fuse has plenty more to do, something I'm considering designing as i go along.

The size is scaled to suit 2 x 90mm fans. That equates to a 200cm Span, 196cm Length and 60cm height

Anyway i thought i'd break down my construction plan per each section:

*Wing*
Main structure built from 3mm Depron laminated to balsa with resin. As for the Airfoil I've chosen a rather generic lifty section which i've seen in plans used on other depron airliners before. I plan to cut these sections out and again laminate them with balsa and resin. Then the wing will be sheeted in depron.

Check out the pictures of the 3d model i made, its not completely accurate, nor is it very pretty (i only have about 5 hours of experience with google sketchup), but it atleast shows that by using the plans and some simple calculations it would be quite easy to cut out all the pieces accurately and such that they form a scale looking wing.

I have enlarged the size of the ailerons, and intend to have working flaps with internal linkages and a low hinge/pivot point so as to achieve that slotted/fowler flap action.

*Fuselage*

My fuselage design is somewhat lacking, I have worked out the profiles of the fuselage sections, I'm aware they won't be totally accurate as there is only so much you can gather from a three view, but it should suit my needs appropriately.

I intend to build the fuse off of a flat sheet (the top down view), and cut out the cross sections i've drawn up to get the circular shape. Then rectangles of depron will be added inbetween sections to strengthen the structure up and also give the sheeting something extra to stick to. I will attempt to show this in a 3d model if i get the time, otherwise i think i'll just launch straight into it and build a practice section, I know exactly how i want to do it, just whether or not it will work is the question

*Engines*

Two x 90mm fans.

I want to keep the weight of the model as low as possible so as to achieve a scale look in flight, and because of this i don't need to be putting out 3000w and 4kg of thrust per engine.

My aim is to keep the flying weight below 2.5kg, so nearing 1kg of thrust per engine would be more than adequate. I'm not sure what sort of set up could achieve this, but i was leaning something along the lines of a HC fan, 1800-2000kv motor and either 3s or 4s lipo's. As you can probably tell i'm not too knowledgable on choosing an appropriate setup, so could some of you in the know with this sort of stuff help me out?

Anyway thats probably enough waffling for one night. Check out the pics of the model and plans below (note plans are done in photoshop to actual model size), constructive criticism would be appreciated.

Cheers

Nick
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Old Jun 06, 2010, 07:16 PM
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St.Catharines, Ontario
Joined Jan 2009
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check out the 707, 767 threads by demondriver (Chris) and also check out the A380 thread by Airbuzz (Olle). they may give you some inspiration for your build and may help you get some ideas that may not have thought about. may I also suggest the DC9 build by JB. the plane is amazing and above the skill level of most builders, but worth a look at. interstingly, Chris is using mayannaise jars as nacelles for his 90mm fans on the 767, so there's ideas there that you could possibly use in your 777 build. one area you might want to look into, is if the fuselage is a true tube shape. most airliners are what is loosely called a "double bubble" design, in that it has a cross section of an "8" rather than a "O". check into that before you cut your former templates. good luck.

Rich
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Old Jun 06, 2010, 07:28 PM
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St.Catharines, Ontario
Joined Jan 2009
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also, for the wingtips, I wouldn't use the undercambered airfoils. because of the undercamber chord line, it actually adds to the positive AoA of the wing, when you are flying at higher AoA angles, which is opposite of what you really need in those situations. for that reason, it would make more sense to use a semi-symmetrical airfoil of the same thickness percentage, with washout (twist) built into the tip. you want the majority of lift to be produced closer to the foils to allow those to stall first and allow the tips to remain flying. so that is the reason why I would change the foil at that location. a Clark Y or something similar would be a good compromise to use and noone will notice the difference at the same thickness as scale. the root airfoils will work awesome for RC. people tend to think that they don't, but they do quite well. look at the Mibo A-10 as an example..............it uses the same undercambered wing, just like the full size one does. if you need any help, ask away and myself and others will help you out when needed.

Rich
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Old Jun 06, 2010, 07:29 PM
2014 EDF JET JAM We be Jamming
Kevin Cox's Avatar
St. Louis Intl, Missouri, United States
Joined Jan 1997
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Interesting project.

Keep us informed and good luck!
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Old Jul 18, 2010, 07:51 PM
Go FASST or go home...
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Bergen, Norway
Joined Nov 2002
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Nice project! Will be following closely!

Ben_E
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Old Jul 22, 2010, 04:33 PM
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Corelli's Avatar
United States, NM, Farmington
Joined Jun 2008
840 Posts
90 mm fans generally use 5-6s lipos . With a 1900kv-1600kv motor . Im no expert so dont take my word for it .

Looks like an interesting build , looking forward to your progress.
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Old Jul 22, 2010, 09:56 PM
441
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Hong Kong
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Are there any implications in calling it a Boeing 777 from a licensing point of view? I'm all for the idea but trying to eliminate any potential pitfalls. From what I've heard Airbus seem to have a far more 'blind eye' approach to these issues.
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Old Jul 22, 2010, 10:26 PM
Avoid The Ground!
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United States, FL, Tampa
Joined Sep 2008
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Why the 777? E-Flite already did it. However, it looks like your getting very organized.
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Old Jul 22, 2010, 10:43 PM
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Hong Kong
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I think using Depron as material it will be very light ! With 2.5 kg RTF weight you only need 2 x 64 mm edf units and that will be enough. The freewing 64mm EDFs puts out 0.9 - 1.1 kg thrust at 4s each.
My experience with our composite A-330 gives a good indication that should be ok.
Our A-330 weighs in at 4.9 kg. 2 M long and 1.97 M span, with scale struts and air spring retracts. Flies with 2 X 70mm HET fans and motors on 60A ESCs and 3600 up to 5000 Mah 4s1P batteries per side. We fly on 60 % throttle once the airplane is on step and cruises around at scale speeds. By the way, we did the A-330 also for our Australian friend and customer.
Good Luck with your project !
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Old Jul 22, 2010, 11:15 PM
EDF rules... :)
AirX's Avatar
Joined Nov 1999
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To make a model of anything for your own personal use there should not be any problem. It is only when you are mass producing a model that companies like Beoing want thier share of the money.

Eric B.
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Old Jul 23, 2010, 02:24 AM
Go FASST or go home...
Ben_E's Avatar
Bergen, Norway
Joined Nov 2002
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Quote:
Originally Posted by wilerbee View Post
I think using Depron as material it will be very light ! With 2.5 kg RTF weight you only need 2 x 64 mm edf units and that will be enough. The freewing 64mm EDFs puts out 0.9 - 1.1 kg thrust at 4s each.
My experience with our composite A-330 gives a good indication that should be ok.
Our A-330 weighs in at 4.9 kg. 2 M long and 1.97 M span, with scale struts and air spring retracts. Flies with 2 X 70mm HET fans and motors on 60A ESCs and 3600 up to 5000 Mah 4s1P batteries per side. We fly on 60 % throttle once the airplane is on step and cruises around at scale speeds. By the way, we did the A-330 also for our Australian friend and customer.
Good Luck with your project !
Not going ti hijack this thread, but where can I find more info on these airliners?
Ben_E
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Old Jul 23, 2010, 02:25 AM
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Canada, ON, Mississauga
Joined Feb 2006
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Quote:
Originally Posted by AirX View Post
To make a model of anything for your own personal use there should not be any problem. It is only when you are mass producing a model that companies like Beoing want thier share of the money.

Eric B.

Very true, it's not just Boeing doing this, it's Lockheed also going after companies who made models of there aircrafts and have been selling them all along. I also heard Lockheed have gone after lil guys building models of there aircrafts in past but how far that is true, i don't know.
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Old Jul 23, 2010, 02:26 AM
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Canada, ON, Mississauga
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Originally Posted by Ben_E View Post
Not going ti hijack this thread, but where can I find more info on these airliners?
Ben_E

I'll 2nd that....
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Old Jul 23, 2010, 03:28 AM
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Australia, WA, Perth
Joined Jan 2009
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Gosh there's been a bit of interest in my thread of late..

I should say this is on hold for the moment, not long after planning this i discovered windrider are releasing a 737 EDF of almost the same size, and wouldn't mind picking that up. Also i planned it at a rather busy time in my life so i don't actually have any time to work on it at the moment.

To cover a few things.

1* I realise you can get sufficient thrust from a 64mm fan, but then those huge Engines wouldn't be scale, hence 90mm (which the scale was based around) Surely you can run 90mm fans to put out a max of 1kg of thrust, that would mean i could get a solid endurance out of it wouldn't it?

2* Eflite have already done one, yes, so why is that a reason for me not to build my own of a larger scale? I also just don't like the semi scale look of the eflite model, and its totally unrealistic high speed characteristics

3* Name/Licensing issues... This is for my own use so i did not thing there was an issue at all. I have no intentions of making this into a kit and making profit from it, so i didn't think there was an issue, if so I'll change the name...

It is my intention to build it eventually but to be honest i can't see that happening soon. For the meantime i'll continue to plan it and post updates on my design as i continue

Cheers

Nick
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Old Jul 23, 2010, 05:20 AM
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Hi Nick, I love airliners, shame theres so little on our market in these as kits or ARF. I curently fly 777 with 64mm fans on 2x 3S. I think you are bit over optimistik about 2.5kg. I think you are looking more like 4kg AUW. For 90mm fans I suggest min. 6S each which still gives you more then enough power at some 4.5-5kg th. Joe.
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