hooker53

My Feedback: (106)

OK Guys. I know some of you have been around the soaring skies for awhile, so I will call on your Mems to help me here. I have an oldie here that I would love to find out more about. It's a Robbe Diamant with the words, D-Keda under the first name. It's about 125" WS. T-Tail Comp fuselage. It has a slight undercamber wing as well. When I got it, it had a Eflite 15 in the nose. Any ideas, photo's vid links?? Not gonna hurt my feelings if you tell me it was a bad flyer. Ha. Ha. Thanks for all your help.

OzMo

My Feedback: (3)

Hi,
It stinks, you should mail it to me immediatly for propper disposal
http://www.rcgroups.com/forums/showthread.php?t=229070
here's a good place to start, Shredair knows his stuff.

hooker53

My Feedback: (106)

Thanks OZ. I will check that out. I'm very surprized with all the views here that more of the old timers has not heard about this bird. Nothing. Nodda. Must be mighty rare. Ha. I could not even find anything on youtube about it.

da Rock

It does seem to be pretty rare.

The advice given on the other forum also seems to be somewhat dated. MOF, it's dated 2004.

The idea that 10 cells are required shows that as well. There is also very little value in having a geared power system.

Nowadays, with LiPos and brushless, you'd look for any motor that'd simply fit into the nose as the first step. There are going to be hundreds that'd fit, so you look at the weight of the glider to decide on how powerful you'll need. Then pick an ESC to match the amp rating of the motor and a battery with the number of cells to match the motor rating.

There are so very many combinations possible today that there could be thousands of solutions. Have you weighed it to see what you're going to be dealing with? That's almost always the starting point for powering gliders that vanished from the shelves before brushless and LiPos showed up.

da Rock

BTW, any reason you don't want to try the motor it came with?

hooker53

My Feedback: (106)

No there's no reason. I think it would pull it ok. I don't want a rocket most of the time but just to get it above the tree line on the wing would be ok with me.

da Rock

That EFlite.15 is probably a good size for that old girl. It can give up to 575 watts and that'll work for a glider up to 1600g/57oz/3.6lbs.

A 45A ESC is recommended as is a 12x6 or 13x6. Using a 4S or 3S LiPo pack is also recommended.

da Rock

I'd go with a folding prop. Also, since there probably aren't any cool air intakes around the nose, you might consider an open nose spinner. I've had good service from these peopls and they've got the funny spinners.

http://www.espritmodel.com/spinners-...prop-nuts.aspx

hooker53

My Feedback: (106)

I agree with you Rock. It has a folding prop assy on it now with a shaft going thru a bushing. That will be changed to a bearing. Just wish I could find out more about this glider. I will check out your link and thanks for that.

UStik

To find out more about this glider: [link=http://wiki.rc-network.de/index.php/Diamant_von_Robbe]German R/C Network[/link].

Built since 1980, weight 1700 g (60 oz), airfoil Eppler 193, wing loading about 8.5 oz/sqft, but is also intended as an electric motorglider. (That's why there is this registration, D- for Germany and K for motorgliders.)

Click on the pictures to enlarge them a bit.

[link=http://www.rc-network.de/forum/showthread.php/219003-Robbe-Diamant-brauche-Rat]Here[/link] you can see a Diamant (Diamond) in refurbishment, or better "upgrade".

[link=http://www.modelbouwforum.nl/forums/zweefvliegen/151939-bouwverslag-robbe-diamant.html]Here[/link] is a thread in a Dutch forum showing even the plans with the (ancient) electric drive.

Today, robbe calls a 3D funflyer Diamant.

hooker53

My Feedback: (106)

Ustik, Danke, Danke Danke. Now we are talking.

UStik

Glad if it helps. There's a review pictured in the Dutch forum (added the link to my post) which calls the Diamant a jewel of a sailplane. That's an allusion to diamond but it should be a positive review as well.

The plan shows an old geared drive with a strong brushed motor - that's what was available at that time. But even today gliders are equipped with geared drives, and not (only) because they fit in the nose but because slower turning props are more efficient. A good planetary gear (e.g. Maxon) costs only 5% of power, and a brushless inrunner is just as efficient as an outrunner. My 101" 60 oz glider spins a 14x8 CAMcarbon with only 4800 rpm and 70% efficiency.

An open nose spinner is a good thing (as well as cooling air intakes) but not needed. As you probably know, gliders are typically flown to thermal altitude where the motor is stopped (the prop folded) and thermalling started. There's plenty of time for the drive (remember the battery) to cool down. If there is any kind of cooling air intake there have to be air outlets twice as big as well or all you'll get is dynamic pressure in the fuse.

What I forgot: The fuse is tempered epoxi. robbe claims the model to be F3B capable.

hooker53

My Feedback: (106)

Thanks again Ustick. I was looking over the Dutch threads. I wish I could find out the overall length and dihedrial of that center spar they are showing. At present, mine is rigged in a flat wing config.

UStik

The 6th picture in the thread seems to show the wing joiner. I measure 4 degrees (each side)...

By the way, right thrust is 2 and down thrust 6 degrees.

hooker53

My Feedback: (106)

Yes-I was trying to scale it out myself someway. Ha. I will have to remake the motor craddle for it so will set the Deg. in when I do that. Thanks for your help

hooker53

My Feedback: (106)

I have contacted Robbe in hopes of finding the wing spar and spar inserts that goes into the wing. The one i have has had the spoilers sealed but don't think it would take much to open them back up. Looked for a stateside Robbe importer but don't think there is one. Ha.

Tarasdad

IIRC Hobby Lobby used to be the US source for Robbe products. Been a long time, though, so I could be wrong.

UStik

I'm afraid they no longer have this wing joiner system (it's called Imolink). But the aluminum parts (spar inserts) should still be in the wings so all you need would be the joiner itself which could be made from steel sheet metal. The "hooks at both ends seem to be snap-in hooks corresponding to the springs in the aluminum sleeves.

The spoilers are called rotary spoilers. I think they will turn 90 degrees and then be square to the wing chord.

hooker53

My Feedback: (106)

Yes-I miss typed that. Act, I was refering to the flaps of which I know I will need on this plane. As for spoilers if I go with them, I may use a pop up spoiler of some type. I really don't think the alum parts of the Imolink is still there. On the motor offsets you were talking about up post, I was looking at the front of the fus and it is a match to that. so all I would have to do is use that to set it with after I cut a new motor mount. This project gets more interesting with every post. Ha. Thanks guys.

_Dutchy_

Yes, that is correct.
4 degrees is stated in theoriginal manual.

It also states that the Imolinc was available in various degrees.
Too bad that it already was obsolete before the internet grew.
On the other hand; I've also had user info on the Imolinc and a bad habit of the Imolinc was that it could slide a little and in combination with one central servo made that it gave a, not wanted, offsetto the ailerons.

But a shortsummary of the Dutch tread.
That guy recently bought a 30 year old 'new / not build' kit and in the box 2 reviews of the plane were included.
They are dated May and June 1981.
In the sametread can be read that the writer of the review (Hein v.h. Laar)is still flying.
It was stated by one of the actual team members (mentioned in the review) who flewthe F3B-competition in Turin Italyback in the Eighties.
The TS has to finish some work on a Graupner Cirrus glider and if that's finished he'll start on the kit of the Diamant (in about a few weeks).

So in the end it all comes back together.

In case you need any info about this plane, just let me know.



PS.
Yes, I'm the sod who started the Dutch tread

hooker53

My Feedback: (106)

Hello Dutchy. Glad to have you aboard the RCU express. Thanks for all the info. I will work on this one that I have over the winter and fly it this spring. If it was a good one back in the 1980's than it will be a good one now. After all, A new one from the 1980's was a hoot compaired to the designs of the 1060's. Ha. Ha. I know that some designs are ageless but also know a lot of it is how it's set up and how it's flown. Thanks for posting.

_Dutchy_

Off course the moderncarbon F3B ships outclass this ol' lady by far but chance can be that it will outclass a lot of the modern ARF's
Theused wingprofile will give a good penetration and if you build light you can add some weight for windy conditions.
That doesn't work the other way around.

In the review it is also stated that you should / could use some carbon fibre to reinforce some areas around the canopy and in the edge between the hull and tail.
Perhaps you can keep that in mind when you are reconstructing the Diamant.

Funny though, until 2 weeks ago almost nothing could be found about this plane and now and after30 yearsit's actual on 2 sides of the world.

hooker53

My Feedback: (106)

Ha. Ha. Dutchy, I'v been told by more than one that I could dig up more skeletons than you can shake a stick at. Ha. When it comes to most of my flying, I tend to fly (save my turbine jets) moderate. As in not pushing the envelop so mabey it will stay together. I think the wings can be held on simply by threading two nylon screws/bolds from inside the Fuse connecting the wings and that would be lighter than the old system of the Alum stock parts.

_Dutchy_

Why all that rocket science ?
Just use 2 hooks and a rubber band

hooker53

My Feedback: (106)

Yep-that would work to. done that on a small glider one time. guess I been building to many 3d machines and jets lately. Ha. Ha.