frcac

Hi guys!

I was wondering if any of you has any experience with Graupner Discus scale ships?

http://www.aero-model.com/planes/gra...iscus/main.htm

I have the smaller one still in the box. The problem is, that now I have an excellent chance to buy a bigger one with 4.5m span. Has anybody seen it fly, knows somebody who has it or has read a review somewhere? I like the idea of having such a large Discus because we don't have any problems with tow-models - it looks kinda funny when that Pawnee tows 2.5m Swift acro glider almost straight up to 400 m...

What do you think? Thanks

Sašo

brancolitw

I have flown it once and waiting for painting job by my friend.
Very cost-effective scale ship from Graupner. Can be made very scale (if youspend time).
I fly it at slope-side with great performance.

Anything want to know about it?

frcac

Anything I want to know?

You know how this is - you say yourself that you don't really need "another-one" and just keep searching the excuses to buy one. Then you browse all the magazine reviews you can find, and all they write about this Discus are all superlatives. As it seems it is an awesome bird, a great combination for of thermalling, slope-soaring, aerotowing, mild aerobatics...

I am still trying to find more pros/cons but I think I've made up my mind. Regardless to this I'd still like to know your general impression over this scale ship, what kind of RC components did you use and especially flying qualities. BtW - what diameter of retracting wheel do you need with this one (I think I have one retract left for wheels up to 90 mm diameter).

P.S.: I think my smaller still intact Graupner Discus 2B with 3.35 m span will be on sale...

Sašo

Daniel Gut

Hallo Sašo

I have been doing a little research into the big Discus too and have read and heard a few comments about it.

Positive: Flies very well, Is a pleasure to fly in thermic conditions, the kit quality is good.
Negative: It is quite heavy and therefore needs speed (flying weight starts at about 7.5 kg), airbrakes(spoilers) are not very effective and need the aelerons to be mixed in (crow)for tighter slope landings.

A 90mm Retract should be fine. Overal comments are very good value for money and a good peformer.

Regards

Daniel

frcac

Hi Daniel

The only review that I read in magazine is "Der weisse Riese" in FMT 8/2000. There is another one here in Slovenia, but that one is all up weight under 7kg. Then again - if you check the wing loading, you have a glider with 4.5m span comparing with smaller discus 3.35m span - both have identical wing loadings. Since the scale with the bigone is so much bigger the logic consequence is that it has superior flight capabilities comparing to the small one.

As far as aibrakes are concerned I agree, because if you check Graupner catalog the biggest brakes are the 350 mm long-ones, whic are stated to gliders up to 5m span. Of course combination with crow is in order, but then again I think that my Discus is going to be mainly aerotowed and flow on one exceptionally great slope site, which has a lot of landing clearance.

I checked the retract that I have, but it's too smal - just for wheels up to 80 mm. Do you know for some rectracts for wheels up to 100 mm with brakes and shock-absorber that are a good value for their money?

Sašo

Daniel Gut

Hallo Sašo

" Aufwind" magazine had a report about 2 years ago which I have at home, but I find that these reports are for the most part slightly biased, because the tester has been offered a good deal if he writes a nice report etc. If you want it, I can fax it to you tomorrow. I recently bought a vey nice retract in Ebay (Germany) for €59. I have a picture of it in another post here in RC Uni. called SHK from Aeronau. Have a look at it, if it interests you I can give you the email of the person who sold it to me, he has had a few in to sell recently. Mine is the smaller version, he has a larger one too.

Regards

Daniel

frcac

Hi!

I've checked your photo-albums. Nice models, very clean finish - you should be very proud on them.

That retract looks awesome - please give me the email of the person who you got it from. As I see this your "smaller" version would fit a wheel up to 100 mm diameter, which is ok.

As far as such an orchidees are concerned I would really like to have the big Graupner Ventus 2C with 5.5m span, which is also made here in Slovenia. I've seen it aertowed a couple of times and this ship really excells in the air with it's performance. The problem is that I haven't seen this Discus fly, I just read about it. It seems that either you like Discus or you don't because of the polyheidral wings. But that kind of wings give her superb thermal flying characteristics...

As far as Aufwind aritcle is concerned - you can fax it to me (to my dad's office) or if you are able to scan it and then send me the jpegs. Eitherway will do - thank you very much in advance.

Sašo

brancolitw

We seldom aerotow here due to site/land restriction.
We always fly at slope. But for scaling , I still install a
Multiplex retract with Dubro 100mm wheel.

If you want shock absorber retract, it may be hock.
It is true that airbrake is not so effective due to the heavy mass.
I fly it at about 18 lbs. Elev and Rudder servos at the tail.
Good for penetration and aerobatic.

Good value for money for its performance.
I get the kit at about 600 euros.

frcac

Thank you very much for your info - I've decided that I will purchase this soaring beauty. I am in the phase of gathering the equipment and making all the neccessary cleaning works in the basement so that I will make a room for this scale ship.

I can't wait for those warm summer and autmn days to come when I will be able to enjoy those thermals tow after tow after....

Sašo

mattebox

Hi, can you give more details about this? I've been thinking about getting the Icare 2.5M Discus 2B:

http://www2.jonction.net/~icare/discus2b.htm

and I'm planning to use it mainly at inland slopes that have a combination of slope and thermal lift. So good thermally characterisitics would be great, but I also want to do basic aerobatics like split-S and cuban 8's. I also generally prefer snappy roll response so do you thing the polydedral tips will adversely affect this? The last thing I want is a ship that rolls like a dog. Thanks!

frcac

Hi!

If you have a combination of slope and thermal lift, Discus is the right answer. With it's polyhedral wings it sits very nice in turns with minimal height loss. In combination with the right airfoil section - as it is case with both Graupner models which use undercambered HQ/W 3-13 you have a winner for thermal flying. This airfoil is a very good compromise for aerobatic performance also.

You can affect the aerobatic potential with higer mass and therefore penetration, speed and inertia of your model. Discus has two ailerons on each wing, so it helps a lot that the outer aileron has larger control throw than the inner one. Of course basic aerobatics are possible, don't worry.

Discus is a great all-rounder, but if you need something for that "snappy" response, than you should consider something like Swift, Fox, Pilatus B4 and other scale ships. But you need much stronger lift to fly them. Both gliders - Discus and Swift on the top of the hill is the right answer.

Sašo

brancolitw

Yes. Right, the discus can handle basic turning by just only the outer ailerons and little rudder coordination. In-board ailerons can be mixed for aerobatics.
BTW, the film provided can shrink greatly. Don't heat to much with heat gun. Iron and push gently for the camber. Otherwise, you will lose your undercamber and it is not HQ!

mattebox

Thanks for the replies guys! Unfortunately the smaller Discus that I'm interested in does not have inboard and outboard ailerons. It just has outboard ailerons that are about 1" in chord and half wingspan in length. Sounds like it should have decent roll response. What do you think?

mattebox

Oh, one other thing, the airfoil is S 3010. Kind of an outdated airfoil, no?

frcac

mattebox: your Discus should be very good model. But when the scale glider is so small in wingspan, there are some details omitted, like for instance polyhedrial wingtips (if they were scale, the aileron would have to be in two parts). Go for it and have fun - but they say "bigger is better" and this is true for gliding, soaring and thermalling also!

brancolitw: yes, sometimes it's tricky to cover the undercambered wings so that have your camber when you cover them. By the way - I noticed something that I didn't notice on the full-scale Discus: the airbrakes are not parallel to the leading or trailing edge of the wing, but tilted slightly backwards for two or maybe three degrees. Is this the case with your Discus also (this is not the case on smaller version)?

Sašo