I was given this plane by a guy who had bought it but didn't know what it was. I thought someone here might be able to identify it. Wingspan is 57".

Carl,

That looks like a Maxi, Robbe, Germany.
Look for dimensions:
Wingspan 1460 mm
Length of Fuselage 1275 mm

Did fly pattern with one of these in the past, modified, shorter nose and retracts

Cees.

Hi,

Yes, it sure looks like a Robbe Mäxi (Maexi).
It was a rather popular model in the first half of 1970th. Was avaliable as an all balsa kit, glass fuselage+built up wing+stab and glass fuselage+foam wing+stab. Is available as ARF today (glow or electric). I like Robbe Mäxi outline and it flies rather good as far as I know.
Images below from Robbe catalog (in German but pictures will show orginal model rather fine I think).
I have been looking rather long time for an unbuilt Robbe Mäxi with glass fuselage+foam wing+stab and actually had one in reach on ebay once but the seller withdraw the kit for some reason from the auction (I did bid on it). They are rather rare but can be built from plans of course (I have Robbe Mäxi all wood balsa kit plans so it would be possible to build one that way). Nice plane You have by the way. It seems You have the Mäxi FH version (glass fuselage with conventional built up wing+stab). Mäxi has a wingspan of 57.5 inch (1460 millimeter). Images below is from Robbe catalog 1970 (the first image to the left) and 1977 (rest, except Mäxi ARFpictures and kit box pictures).

/Bo

Thanks for all the help. Looks like I've come into a great plane. What engine size would you recommend?

Hi,

In Robbe 1970 catalog theyhave Enya 60 II RC as recommended engine. In 1977 Robbe catalog they have Enya 60 III B RC-G 8 and Enya 60 XF RC listed as recommended engines.

Mäxi was designed by Heinz Elsässer. I believe he was German F3A (then named RC1) champion with Mäxi in 1968. He competed in World championship 1969 with Mäxi (I do not know his exact place) and then he used Enya 60 II RC (also Phil Kraft from US that placed 2nd used Enya 60 II RC).

Today if you plan to use a modern 2-stroke I would probably select OS 55AX or similar http://www.osengines.com/engines/osmg0556.html

Take care of the model, it is a true classic pattern plane. And is capable, if built light and straight and in hands of a good pilot, to perform very well (by the standards it was designed for in end of 1960th and beginning 1970th.

/Bo

Carl,

Most important for the choice of engine is weight I think.
(I did fly the plane with a Merco 61 twin plug in the past.)

You can balance the plane on position of center of gravity and determine the needed weight of the engine.
Differences are a lot between the old engines and the modern ones, for example modern OS Max 61 FX is 534 gram.
Old engine, HB 10 cc 415 gram and OS Max H 60 417 gram.

When you have to ad weight in the tail to have the CG on right position the differences will be more than differences between the engines alone.
I did not weight the mufflers, only engines.

Second point is mounting holes if there are wooden bearers. Maybe you can find an engine that will fit in place.
Recommended power, 0.60, 10 cc as in the documents.
I do have a lot of engines, when you can give distances between the mounting holes I (we?) can look for engines that will fit in place.


Cees

Carl,

I have some interesting historical facts about the Mäxi and 1969 World F3A Championship. I have the orginal official program brochure from that event.
For example:
- Front cover of the program below.
- On one of the pages Robbe had an ad and guess what plane they had choosen to show - yes a Mäxi.
- The event was held in Germany, Lemwerder Bremen, July 23-27 1969 with competition days July 25-27. See the schedule below from the brochure.
- Start order was as below (yellow pictures), Elsässer had start nr 14 (the poor guy from Sweden, Jesper von Segebaden had the not so nice start nr 1, must be the worst start number to have in a WC).
- The manuvers they flew was as pictures below. When you can fly those manuvers with your Mäxi then you should be happy and remember that exactly this flying schedule was Mäxi designed for.

/Bo

7th

Ray

I asked about the engine size because this plane looks to be a little large for a .46 size engine and too big for a .60. I'm not positive but the position of the engine mounting holes is a little bit rearward which makes me think that the original owner might have had a 4 stroke engine in it.

The only engines I have on hand that would be suitable are a Fox .50, a K&B .65, or a Thunder Tigre .60. I really want to put the Fox in it but I think it might not be powerful enough. The 60s look too big and heavy as well.

Thanks for the help and attached files.

Hi,

Try to estimate a total weight:

- Plane as it is now
- Radio in plane you intend to use
- Engine incl muffler weight

The orginal Robbe Mäxi FH according to Robbe catalog had a recommended weight (except fuel) of 2800-2900 gram / 6.17 -6.39 lbs.
With a 60 engine.

What specifications is it for the engines you have? (like weight and hp)
How old are they and do they run well?

/Bo

Carl,

I did remember this picture to compare and I show you.
The Mäxi is of the period of the Kwik Fli MKIII of Phil Kraft.

Latest world champs victory plane of the USA (1967) for more than 20 years after that.
Phi Kraft was second place on the list of world champioships in 1969.

(Look for the MAN magazine Februari 1968)

The span of the Kwik Fli was 60”and that were the dimensions in that period.
The Taurus was 70” with 0.45 Cubic Inch.

About a four stroke? I do not think so, it did have a front mounted carburetor when I look at your picture.
Maybe it was a Schnuerle ported engine.

Cees

Could you give me some more information on this plane? I can't read it off the plans. I need the following:

Wing incidence

stab incidence

center of gravity (looks like it is balanced directly under the wing spar)

engine right thrust and/or downthrust

I am going to use a Fox .50 engine.


Thanks,

Carl

carl,

Mäxi is interesting for these values.
There is a "Bezuchlinie" drawn in the side view beneath the engine, this is reference line.

Related with this line the wing incidence is 1.5 degrees
Related with this line the stab incidence is +0,5 degrees (positive but no taildragger!)

Second value written for the wing "1 degrees eff". this is related to the stab.
So the decalage is 1.5 - 0.5 = "1 effective"

Balance point for CG under the wingspar.

Engine side thrust 0 degrees:
Engine downthrust written as -2,5 eff.
This 2,5 degrees downthrust is related with the wing.
Not written the downthrust related with the "Buzuchslinie"/ reference line, this is 2.5 - 1.5 = 1 degrees.

The German designes of the past are much more informatieve as the "other".
This has to do with longitudinally neutralization of mayor flight forces, the thrust line related with the center of resistance.
More about these on this moment and in the near future (Caravelle, Graupner) in my own thread: Redesign an reconstruction of the Oldest Taurus on Earth and the subjet "downwash".
http://www.rcuniverse.com/forum/fb.asp?m=10122372


I do not know the Fox 0.50 but that will be fine, ENYA 45 BB and ENYA 60 II / RC I do find on the plans.


If it is not clear, please ask!


Cees

I flew my Maxi for the first time yesterday. It flew very well with the Fox .50. Thankfully, it was not nearly as fast as I expected it to be. I initially had too much aileron control in it and not enough elevator. I'm going to really like this plane.

carlgrover,

Nice to hear it is airborne again. I would very much like to see some in flight pictures or a video if you can get it in future of this legendary pattern plane.

/Bo