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157" Discus Glider

Old 06-19-2006, 02:58 PM
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Default RE: 157" Discus Glider

For those guys who are running an electric power system, are you running a BEC setup or is everyone using a separate receiver pack? I like the idea of not having yet another battery onboard and am leaning toward a UBEC or similar to power the radio gear.
Old 06-19-2006, 06:56 PM
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Default RE: 157" Discus Glider

Flyfalcons:

NO BEC. Here's the issue:
You lose the ESC, you lose the plane.

With my power set up I had to move the receiver battery to the tail of the aircraft (6v 1800nimh)I would prefer to have the little bit of added weight than take the chance that the ESC will fry and cost me the entire plane, because the BEC killed off the use of all of my servos.

I will only run BEC in the smallest of my electrics, or in an aircraft where the added 4 ounces will make a big difference in how it flies.

My 92" Twin will have 4 battery packs to insure I don't lose power to the servos if something goes wrong with the ESC's.

This is one airframe that 4 oz will not make or break how it flies.

Dave
Old 06-19-2006, 07:42 PM
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Default RE: 157" Discus Glider

Good point Dave, I was thinking that a 4.8V 2700mah Nimh pack should power four minis and two standard servos for quite a long time. If that doesn't do it then I can add another one in parallel.
Old 06-22-2006, 07:36 AM
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Default RE: 157" Discus Glider

Sad news for me:

Didn't have room for the Glider in the transport, so we had to leave it in Phoenix [&o] (along with 3 other aircraft)

But, there is always next saturday. [8D]

Hopefully, we will get some other reports from others here on how they fly this week.

Dave
Old 06-22-2006, 09:45 AM
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Default RE: 157" Discus Glider

Yeah, let's hear some more flight reports or see some pics and video! Also, has anyone installed a retract? I found one at icare-rc that should work well. I know it'll add a little weight but for the cool-factor, it might be too tempting to resist.
Old 06-23-2006, 03:07 PM
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Default RE: 157" Discus Glider

My glider arrived today, and it looks to be in great condition! The fuse has a few waves in it but nothing that will bother me when I'm out flying it. The spoilers work freely, and I don't feel there will be a problem with a mini servo driving them. Looking forward to getting this in the air!
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Old 07-21-2006, 01:02 PM
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Default RE: 157" Discus Glider

Well after seeing all the post on this bird I thought I would jump in on it. Well to be honest I couldn't pass on it at $110.00 = shipping and insurance = $158.00 to my door....... bring it on!

Has anyone dumped on and broke a wing to see whats inside?

Thanks
Bill
Old 07-21-2006, 01:36 PM
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Default RE: 157" Discus Glider

Bill, I'm pretty sure the wing is all foam with some fiberglass reinforcement, sheeted with 1/16" balsa. That was a pretty good deal you got on yours.
Old 07-21-2006, 01:59 PM
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Default RE: 157" Discus Glider

I can not imagine it getting much lower than that. I figured well jeezzz .... how much can I lose?

I was just wondering what kind of spar it had in the wings. Has anyone folded one yet, if so, what were they doing when it happened?

At this price I might get another and try to turn it into something a lot better than it is. I realize that I am NOT getting the highest quality but then again, I can work wonders on a disaster. Like I said ....... how much can I loose! I could spend $158.00 on taking the wife out for the evening or get a glider. Sorry babe ,,, at least it didn't cost half as much as the dress you bought last week! [:@]

Bill
Old 07-23-2006, 12:25 PM
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Default RE: 157" Discus Glider

For those that have flown this bird, what control throws are you using? The instruction sheet that came with it does not mention it. I found some other instructions on the web that (supplied by a different vendor) that specify 36mm total throw for horz stab, 70mm for rudder and 35mm for ailerons. The illustration indicates this is measured from one extreme of travel to the other.

What works well?

Bud
Old 08-02-2006, 02:57 PM
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Default RE: 157" Discus Glider

OK who's flown, and how did it fly?

Had to wait for more $$ to buy another ESC (it doesn't grow on Cactii you know!)
We hope to fly in a couple of weeks here.

Anyone else flown yet???

Come on Guys, let's hear about it.

I know that as soon as I fly I will get home and post it here and a tie to a video (I hope) - If I can get it posted properly.

Dave
Old 08-02-2006, 03:28 PM
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Default RE: 157" Discus Glider

I plan on a maiden flight this saturday. I'll post pictures of the results.
Old 08-05-2006, 02:38 PM
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Default RE: 157" Discus Glider

Maiden flight took place as planned today. Used a PVC dolly modeled after the one Tom in Cincy detailed in this thread earlier.

Some details on the plane:

Weight : 10 1/2lb
Motor: AXI 4120/18
ESC: JETI 70 opto
Prop: Folding CAM 13x8
Battery: Hecell brand LIPOs, two 3s2p 4000mah connected in series to create a 6s2p pack.
CG at 80mm from wing LE.
Control throws: Ail and elev - 36mm total throw, rudder 70mm. Spoilers fully deploy or retract.
With everything in the nose except the elevator servo I needed to add 10oz of lead in the nose behind the motor to balance.

Kit modifications:
Clipped nose back to provide 2" dia firewall for motor. 1/8 ply motor mount.
Servo tray in nose removed.
Nose from firewall to area below wing LE fiberglassed with 6oz cloth and epoxy finishing resin.
Landgear wheel installed with 1/8" box to support it and glassed to belly.
Belly center line and fuselage canopy area glassed with 3 layers of 6oz cloth on top of previous layer.
Used 3/16 wood dowls at wing LE and TE for antirotation function.
Added 8/32 blind nuts to wing root ribs and bolts through fuselage to attach wing to fuselage.

Flight notes:

85 deg, very humid, dead air.

1st Launch from the dolly took a long roll (about 180') because I had too much negative angle in the supports that the wing rests on. I modified it with some extra padding to take out most of the negative and the 2nd launch was pretty short, maybe 70 feet.

Only needed a couple of clicks ail elev trim.

Max sustainable climbout angle was about 50-55 deg. Got this 4m plane up to a small size in about 30 seconds.

Spoilers work well at killing lift. Generate about 5-10 deg nose down when deployed.

Noted a cool whistle while flying low enough to be heard.

First flight was about 15 minutes with 5 or 6 climbs back up to altitude. Did several high speed passes that consumed the altitude. Decided to cut the flight short to conserve batteries in case I needed to go around. Turns out I still had 1/2 the battery capacity left.

2nd flight went well until landing and during rollout I caught a wing tip near the end that spun the plane around and caught the nose. I landed a little too hot and was trying to turn to prevent overrun onto out road. Bad idea. Caused some cracks to the fuselage in the area of the fuselage of the wing LE on the left and right sides as well as a crack below the wing area on the right side. Repairable minor damage, but it cracked where I had not re-enforced it during the build. One other notable thing on the 2nd flight, I was diving for a pass and thought I would pull out and try a loop and heard a pop. Nothing else happened and nothing external could be noted wrong with the wing. I did not pull that hard on the elevator, so beware!

Overall - well worth the $127 I paid on ebay. Gotta be gentle with it though.

Bud


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Old 08-05-2006, 05:57 PM
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Default RE: 157" Discus Glider

Thanks for the flight report! I like the white wingtips too.
Old 08-05-2006, 08:11 PM
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Default RE: 157" Discus Glider

If you go to this link

http://www.putfile.com/gehrbox

You can see a few small videos of the first flight(under 7MB). They are unedited, so please ignore my wifes thumb in frame here and there, shots of the ground...etc.
Old 08-05-2006, 08:32 PM
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Default RE: 157" Discus Glider

Love the whistling on the high speed pass. It looks like the 4120 has plenty of power for this glider; I was considering going bigger but I think I'll stick with the 4120 now.
Old 08-05-2006, 10:37 PM
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Default RE: 157" Discus Glider

It's pretty tight in the nose with two 3s2p 4000mah batteries side by side. I have the ESC on top of one of the packs.
Old 08-07-2006, 10:05 AM
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Default RE: 157" Discus Glider

Just a qiuck note. My glider is still alive and flying well. Gehr2box looks like you got everything cooking. Glad your having fun, I really enjoy flying mine. If there is any lift out there at all the Discus seems to fly forever. I have not tried to do any aerobatics with it. I am too leary of the wings failing. With these long wings, making a tight radius turn always results in the inboard wing stalling and falling.. It still amazes me how gracefull it looks slicing through the air. The electric power makes it hassle free.
Cya
Tp
Old 08-17-2006, 01:50 PM
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Default RE: 157" Discus Glider

FYI on wing construction weakness noted.

As I reported previously I noted a loud "pop" during a mild pull out to a high speed pass on the maiden flight. Read that as a GENTLE pull out during a high speed descent. Nothing external was noted and the plane flew fine on a second flight. I caused some minor damage to the fuselage during the 2nd landing when I attempted to turn slightly to prevent overrun onto a road. After careful consideration I decided to trash my plane rather then repair the minor damage because I placed a higher value on the lipo's, motor, servo's and esc then on the $127 airframe.

I did some destructive inspection of the wing and found the source of the pop. Each wing panel is constructed of 2 panels that are stitched together about 2/3 of the way to the tip. if you look closely you can see a sawtooth joint on the top and bottom of the wing panel. This joint is not staggered. When I attempted to bend the wings both broke at this joint pretty easily. I noted that the main wing spar ended on both wings about 1" past this joint. The spar appeared to be laser cut 1/8 plywood. There was no glue or scab materal on the spar to attach it to the structure on the second part of the panel. The only thing keeping the wing intact was the 1/16 balsa sheeting that was sawtooth stitched together. The pop I heard was the sheeting beginning to fail.

If you have one of these planes I would advise glassing this area of the wing.

I enjoyed the flights and found the plane to handle well, just too boring for my taste.
Old 08-17-2006, 02:24 PM
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Default RE: 157" Discus Glider

My retract from icare-rc just came in. It's a very nice unit! I also have a motor and some radio gear coming in soon so I'm looking forward to get this project going. It might be boring to fly but I think it'll be fun to chase thermals with it. The retract and spoilers will just be a little added fun.
Old 08-17-2006, 04:25 PM
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Default RE: 157" Discus Glider

I thought the plane looked majestic in the air. Everyone thought the low passes were awesome, cool whistle and all. I had fun tooling around, but need to be able to loop and roll. An AXI 4120/18 had more then enough power to make it a tiny speck in the sky over and over again.

I bumped into a few thermals. It looked like it was pretty responsive to light lift. The wings REALLY flex in even a light breeze.
Old 08-17-2006, 07:28 PM
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Default RE: 157" Discus Glider

If you want to electrify another glider about the same size, you might want to check out the 4M Lunak. You can get it at espritmodel.com and soaringusa.com. Each site has a separate video of this glider flying and doing aerobatics, and the one on Espritmodel is electrified.
Old 08-18-2006, 06:31 AM
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Default RE: 157" Discus Glider

Thanks for the info. I have a U-Can-Do 46 that I'm planting the stuff in for now.
Old 08-18-2006, 08:51 AM
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Default RE: 157" Discus Glider

Sorry to hear the glider is kaPutz. I do appreciate the report on the wings construction. I agree with you on every point Bud.
Lots of wing flex, No aerobatics, Flys well, Looks great, ect.
I don't know it I would ever by a second either. Its a lazy day flyer---- right up till the landing !!
Tp
Old 08-18-2006, 04:35 PM
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Default RE: 157" Discus Glider

Ya it was a tough decision, but my field has some pretty inaccessable areas. My fear was that I'd fold the wing over one of them and lose all my equipment. If it had not been for the loud audible pop I'd be flying it tomorrow... oh well.

I appreciate the help you provided on the setup and launch dolly. It worked like a charm and the performance exceeded my expectations in the power dept.


Bud

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