gyandras

Hello!

These are my first words in this forum....
I need help, I've got a Speed 400 and a Jeti JES 020 controller and I want to build an electric glider with this stuff. The demands are the followings:
- Wing: The wingspan maximum 1.5 metres, becouse I want to carry it on public transport (I make the wing from two pieces)
- If I don't want LiPo accumulators which is tthe best choice for power supply? I imagined 7-8 cell of NiMh AA batteries, 2400 mah.
- I think I should buy a gearbox, but which size? 1:3?
- I want to build it with 4 micro servos, so I want that the plane can do all the MIXes like aileron differential, ?bird brake? (I dont now this word in English)

So, can You help me with plans or links where I can find similar planes? Please!

Thanks and sorry for my English!

gyandras

jester1a

My Feedback: (1)

Watch the batteries that you suggested. I had great plans to use 10 AA Nimh with a 30 amp AXI and they wouldn't provide the current needed. Seemed ( going from memory here) they quit at about 20-22 amp causing the motor to cycle on and off at something like 1/2 power.

JESTER

gyandras

Hy!

Thanks the reply!
I think that wont be a problem becouse the Speed 400 uses maximum 5 ampers... but thanks, I will try it!

kwmtrubrit

I can't help you with your questions, but would like to say that your English is probably a lot better than the Hungarian spoken by most of the individuals reading your questions. Good luck.

Keith

gyandras

Hy!

I blushed when I read your reply... I have done an intermediate state examination in English last year, and in this year I will try the highest exam.

About the plane :

I have look around on the net and collect the gliders with speed 400 and with a maximum 70" (1778 mm) wingspan.

The most frequent profiles are the followings:
- SD 7080
- E 205
- SD 3021 ( S 3021 is the same??)

Do You know anything about these profiles? Which do You recommend for me, if I want to bild a plane with good thermal abelities?

I think the best power system will be the Speed 400 with an 4:1 gearbox and 7 cell 2/3AA KAN 1700 mah accumulator pack and with an 11*8 folding prop.

The wing will be a polihedral wing with removable wingtips, it's the best wing type I think becouse in the center of the wing there are the rubbers which press the wing to the fuselage. Oh that's a pretty complicated sentence

That's all what I figured out yet. Please help!

BMatthews

First off welcome to RCUniverse.

As to your project how are you going to build the wing? If it's going to be molded from foam then any of the sections you mentioned will be fine. If it's going to be built up from balsa and then covered I suggest you use the Mark Drela AG34. It's intended for open frame design that is then covered with plastic or tissue and dope.

Mark also designed the Allegro Lite and the E-lite. The E-lite being powered by a Speed 400 on 7 to 8 cells. But it is a polyhedral model that uses 4 channels, rudder, elevator, spoilers and throttle. The way it is designed it is made so the wing can easily come apart in 3 pieces for the wing. The fuselage would still be quite long unless you designed it so it breaks into two pieces. The plans show a carbon fiber boom. If you can't find one then a regular fuselage would work for an electric glider. Dr Drela uses a direct drive prop on his electric but he is very good at trimming the model so that it flies uphill at a good speed. It would be very easy to try to climb too fast and end up with the model mushing around with a direct drive. A gear drive prop would be better for someone that has trouble being able to tell if the model is flying efficiently or not.

You can read much more about Dr Drela's Allegro Lite on this page....

http://www.charlesriverrc.org/articl...egrolite2m.htm

If you are going to use all four channels with mixes for advanced control then you don't need a polyhedral wing on such a small model. The ailerons will provide you with lots of control. But it is still a good idea to use about 3 degrees of simple V dihedral to provide some basic stability for when the model is just a speck in the sky in a thermal. For such a small model I would not bother with flaps. But if you want you could use the mixes and separate servos for the ailerons and reflex them up to act as Spoilerons.

Or if you are a new pilot then I would suggest you forget about the ailerons for now and make the wing with polyhedral and just rudder, elevator and throttle control. It'll be a simpler project and easier to fly.

The "bird brake" you are wondering about is called crow, crow brakes or crow flaps. It's all the same thing. It's when the flaps go down and the ailerons both go up. It's named after the black bird called the crow.

And some more hints. The KAN1700's are still too big and heavy for a Speed 400 model. You would be far better to lighten the battery weight by using something like the 2/3A KAN1100 or even the lighter 650 or 750 cells. These cells would still provide you with enough power to climb high enough to hunt thermals 2 or 3 times on one charge. The 1100's would easily give you 3 very high climbs and maybe even 4 climbs on one charge. Or about 5 to 7 minutes of flying around doing fast passes and some mild stunts.

I like the idea of a 1.5 meter model for a Speed 400. That size will ensure some quick flying, mild stunts but it will still be large enough to thermal easily if the pilot is up to the task. Good luck and be sure to post pictures as you do this project. And if you need any design hints feel free to offer up your plans.

gyandras

Hy!

I want to build up the wing from balsa with an carbon tube boom. It's hard to explain how I planed the wing so I will draw a scratch.
I have got the program called "Profili" but I can't find Drela's AG34...
The fuselage will be a simple carbon tube. I know the plane Allegro, thanks for the link but it's too big.
I don't want to build an "only 2 chanel plane" becouse I built 3 plane with elevator and rudder and I want to build a plane with aillerons.
That's it! Crow flap! In Hungarian this bird called "varju".
OOps I had done a mistake when i wrote "7 cell 2/3AA KAN 1700 mah " of course it will be a pack with 1100maH cells and it will be 140g ( 5oz.).

Thanks everything, I will post first of all a scratch, and after pictures from the building.

I have got a strange ask: Can You correct my mistakes?

Andrew

BMatthews

A carbon tube spar is easy to use but it is not the best use of the material for best strength to weight. For an electric model where there is no real heavy launch pull from a towline you can use it but remember that if you pull up HARD at high speeds it may be too much for the tube unless it's quite heavy so that it gives you the extra strength. The best spar design is an I beam with carbon caps top and bottom and some form of full width webbing between like shown in the Allegro Lite article.

But if you choose to use the tube for ease of construction then that's your choice. At least you have chosen to do it that way for a reason and will live with the outcome if there is any problems.

If you're going full controls then I suggest you stick to the flat wings as mentioned in my last post.

Good luck with the project and be sure to get some pictures up. It's always a proud moment when an original design flies.

As for the spelling and language correction. Sure, I'll just change what you posted directly. Save a copy of all your posts first and I'll do the corrections later today or tomorrow. That way you can see the grammar and word changes.

Your english has a number of mistakes but the meaning comes through just fine. You're actually doing very well at it.

gyandras

Hy!

Thanks!
If it's problem to correct it please forget my ask!

gyandras

Ohh...
And where can I find Drela's AG34 for profili?

jester1a

My Feedback: (1)

Here you go: [link=http://www.charlesriverrc.org/articles/drela-airfoilshop/markdrela-ag-ht-airfoils.htm]Dr. Drela airfoils[/link] It has a bunch of them.

JESTER

gyandras

Thanks!

BMatthews

OK Andrew, I got out the dreaded red pencil and you can see my own try at correcting your grammar and spelling in the quotes in your posts. Hope that helps. You'll see that I also tried to suggest a more common use of phrase in some cases. As I'm sure you already know some of the phrases just do not translate very clearly as there is a lot of culture in some of the common sayings that is impossible to pass on with simple words.

Reading over this again reminded me of a sketch of my own I did about two years ago. It is for a 60 inch (very close to 1.5 meters) Speed 400 model that would be used with a direct drive prop for best speed. If you've seen the Hotliner style of model you know that they are smaller sailplane like models but with big motors on them to climb and fly very fast. With only a Speed 400 you could hardly call this a "hot" liner so I came up with the term "warmliner".... It was intended to use a two piece plug on wing. No flaps but it does have full controls with a V tail. With care I think it could be built down to a total weight of 16 to 18 ounces (450 to 500 gms) and would fly fast but still be able to thermal. If this helps you in any way feel free to use what you like about it. The one wing needs more separate ribs to be cut and that's why I came up with the second concept on the left side with mostly constant chord wings and just a few different ribs in the tips. There's a third rounded option inset on the left as well. This curved option would require some careful molding of the balsa sheeting but only requires a few special ribs to be cut out. The rest of the constant chord ribs can be cut out using a single template.

The airfoil is a very low camber type as you can see. The intent being to let the model fly fast and not slow it down very often. The AG34 would offer up better thermalling but perhaps at the slight expense of speed that you would get from a thin section with lower camber than the AG34. From all accounts the AG34 is quick but not really fast in a racing sense but it'll fly slow much better than some of the faster options. You need to decide how you want to fly and then chose your airfoil.

If you see anything you like feel free to use it and if you would like the CAD file (you need to have a CAD program or a CAD file viewer to look at the file) PM me with your regular email adress that will accept small attachments.

gyandras

Hi!

Now I've got the scratch the only thing I need is a scanner...
Thank You very much!

BMatthews

Not "scratch", it's SKETCH... Scratch is what you do if you have an itch. Or in scratch building where you start with no plan. Or to "start from scratch" meaning start from the beginning....

If you like my sketch I can send you a larger picture file or a CAD drawing file. Just PM (Private Message) me through this site with an email adress that takes attachments.

As shown the model is as much a zippy racer as it is a soaring design. If you want to enhance the soaring then it could easily use a shorter and slimer fuselage so it looks a little more like a sailplane.

gyandras

Hi!

So, here is the SKETCH :



Please tell me everything You think about it!

BMatthews

We only got the tiny thumbnail. At 496kB you'll need to resize a copy for the net and then you can load it directly here. Use a photo editor program to cut down on the pixel count. You want to set the version for posting at RCU to 150 pixels per inch and set the overall size to about 8 x 6 to 7 inches or whatever it comes out to when you make it 8 inches wide. That's about 15 cm.

But from what I can see of this very small sketch it seems OK in an overall basis.

gyandras

BMatthews

Ah, that's much better.

First off the wing angle of 3 degrees is far too much. If you're using the sort of airfoil you show then reduce it so that the flat lower surface is level. The true angle of incidence will then be about 1.5 to 2 degrees. If this is a true rendition then your airfoil looks a bit thick for a speedy model. And you have enough dihedral in the wings that you won't need ailerons. But it looks like you have flaps on the inner panel and I don't see any ailerons on the outer panel. Have you changed your mind about the ailerons? And finally if the V tail shape is the flat true shape then I think it needs to be a little bit bigger. Increase the span of it to 260 mm for the flat layout. And last of all you may want to reshape the fuselage pod with more of a droop in the nose.

gyandras

Hi!

OK, I will increase the span to 260mm. I didn't draw the aillerons on the sketch becouse I don't know where should I put them! Please help! The wing angle will be 2 degrees.
And how thick should be the fuselage carbon tube? 6mm? Is the 6mm Carbon tube enough in the wing?

Andrew

BMatthews

I don't know why I didn't see this before but with your wing sheeting and the web spar as shown I think you are going to find that all your wing's loading will be taken up by the D tube that is formed by the sheeting and web. The carbon tube won't have to do anything with the rest of the wing built as you've shown it there. If you're going to use that sort of wing structure then you may as well leave out the tube and just add in some spruce spars under the rear edges of the sheeting. It'll be lighter, easier to build and more rigid and just as strong to the point of failure.

The last thing you want with a sensitive model is a boom that flexes very much. So I would suggest that for a model of this size you want at least a thin wall 8 mm tube and a thin wall 10 mm or 12 mm would be even better.

On a larger electric glider that I have I tried to use a 7 mm carbon arrow shaft for a boom and put a T tail on the end. The drag from the high mounted tail was enough that when I gave it up elevator to recover from a dive on my second trim flight the drag from the T bent the tail boom far enough that even with full up on the servo the tail had down elevator in it. I was lucky that I had gotten a thermal and was VERY high when I tried to see how fast it would go and had the time to realize that if UP was not working that DOWN was my only other option. The model was in a very fast vertical dive and I pushed full DOWN and the model outside looped to level but inverted flight. I then let the nose come up slightly and used full rudder to roll out of the inverted attitude. The nose dropped a bit and I thought it was going to flex and go into a dive again but it juuuuuuuust caught in time and the nose came back up. I finished the flight using VERY slow flying speeds and took the model home for some modification.

So do not make your tail boom TOO flexible. Discus launch gliders are the only real exception to this. On those the tail surfaces are centered on the boom so the boom see even drag pressures and any flex is sort of cancelled out... or near enough to it so that it is effective.

In your case with it being an electric glider and the V tail being all above the boom the drag at high speeds could flex the boom downwards. To control that bending you need to use a stiff tail boom. The best way to have stifness is to increase the diameter.

gyandras

Hi BMatthews!

"The carbon tube won't have to do anything with the rest of the wing built as you've shown it there."
OK I understand it, it's logical but If You take a look at the Allegro plan You can see a composite (wood and carbon) main lath under the shafting! That's what I want to replace with the tube. And I don't think that the 0,8 mm balsa shafting is strong enough... and I want to use the carbon tube a wing joiner also. But I really don't know what should I do... I want to make the wing strong and light.

Where should I put the aillerons?

Andrew

gyandras

Hi!

I have started to build the wing. Now it's lieing on my table, I'm stucking the shafting. I've done several changes, the shafting is from 1 mm light balsa, the ribs too, I left out the carbon tube from the wing. Here are some pictures:

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Now it's about 80 gramms.

Andrew

gyandras

Nobody likes it? I think it's not bad... What do You think? Any ideas?
I've got a question: I want to use a gearbox... but which size shoul I use?
3.7:1, 4:1? And which prop?

Please!

Andrew

BMatthews

I think you mean "glueing on the sheeting" where the glue sticks the balsa sheeting to the wing ribs. The sheeting being the skins of the forward part of your wing.

Looking nice. I see you decided to go with conventional wood spars. Looking forward to seeing more. The quality of workmanship in the pictures looks to be very good.