RF-4 Phantom (Uwe Ralle / UR Modellbau)

[Berto]

I have already purchased a next project for when The RC Custom Jets F-18 is almost finished.

A RF-4 Phantom from UR Modellbau.

This was the picture in the advertisement:

The model is 'new'.

The specification are:
Wingspan: +/- 1590mm
Fuselage length: +/- 2510mm
Weight: +/- 16kg

I have read a few threads here and plan is to keep it light and install 2x a Kingtech K70 turbine.
Gives me a real trust of 14 Kg and the plan is to keep the flying weight with fuel around max. 16Kg.

Will see if this is possible.

Here some pictures when I just collected the model:

Fuselage details:

Tail:

A lot of space:

HeloooOOOO, a K70 will fit:

A lot of room under the canopy:

Inlets:

Exhaust:

Elevator connection:

Elevator control:

Mhh, the F-18 looks kinda small:

And safely stacked:

So far for weight saving, ordered a 'scale' gear + Electron wheels in the correct size:

 

[Herbert Klaus]

Very nice, and very rare these kits nowadays.

Lucky you

Question: from where did you get the "scale" struts ?

Bedankt

 

[Northwoodhornets]

Nice! Does anybody know the construction of the wings? How are they reinforced? I am still planning balsa/styrofoam wings for my F4 with almost same size. I have no idea how to support the foamcore. Thanks!

 

[Herbert Klaus]

Chris,
what I found in the net when approaching the same topic was the build-up similar to building glider wings: carbon joiner, rectangular section, with a spar made from carbon UD within the foam slot. I found this build-up would make sense and are actually preparing the same for my project. Would need to look in my files for the pics I saved, in case of interest.

 

[Berto]

Thanks all for your comments.

@ Herbert,
will send you a PM.

@ Chris,
Wings are completely from foam, covered with balsa and balsa leading edge.
Flaps and ailerons has to be cut out and a trailing edge has to be placed.
This will give enough strength to the wing.

The wing pipe is about 3cm in diameter and about 22cm into the wing.
Wingtips are the same and glued on the main wings.


The wing outline is pretty scale, but for scale gear location the wing tube is in the way.
Will not change that.

Will place the gear somewhat angled (instead of the mostly straight build ins) like the original but more forward.
Plan is to make a gear plate which will also be glued to the wing tube pipe for more strength.

 

[Berto]

Planning is to have it ready for season 2022, but have to finish the F-18 first (and some other projects......).
Will also glass the wings and try to add some details like wingpanels and rivets.

But still will have to keep it light.

Choice for 2x a K70 is just because it can.
Have a K70 which sits in my Eurofighter and is planned to also build a K70 in the F-18 if the weight is within limits.

It is cheaper to buy another early K70 then a new big turbine ;-)

 

[Northwoodhornets]

ok thanks. So it seems thats really enough, only to fit the wing spar into the foamcore and glue the outer wings simply to the main wing. I heard this one time but could not believe that this is enough. So thanksfully i didn´t throw my foam cutted wings into the wastebin. Maybe i will try to finish the wings. Thanks for your inputs!

 

[Herbert Klaus]

Nice! Does anybody know the construction of the wings? How are they reinforced? I am still planning balsa/styrofoam wings for my F4 with almost same size. I have no idea how to support the foamcore. Thanks!

Chris, bist Du weitergekommen ?
Ich schaue immer mal wieder in den Fred der Scale F4 in 1/8 in RCUniverse. "Zwar" ganz in Holz gebaut, aber um so mehr mit grösstem Respekt für das Können was dort gezeigt wird.
Vielleicht ja auch hilfreich für Dich und Dein Projekt.

 

[Northwoodhornets]

Ich hab noch nix gemacht. Irgendwie stehe ich Styro Balsa technisch auf der Leitung. Wenn dann, baue ich die Flügel aus Holz. Aber momentan fehlt mir ein wenig die Lust an den Jets (das ist immer wieder mal so und ändert sich auch wieder ) Bin halt mehr der Segelflieger...
Hast Du vielleicht den link zur F4 für mich? Danke!

 

[Herbert Klaus]

Zu Diensten:

https://www.rcuniverse.com/forum/rc-jets-120/11678916-f-4-phantom-1-8-scale-scratch-built.html

Damit müsste die Motivation eigentlich zurückkommen

 

[Northwoodhornets]

Vielen Dank Herbert für den Link

Natürlich ist die Motivation permanent am köcheln, ich habe halt ständig Bedenken über die Festigkeit der Tragflächen. Da habe ich halt etwas zu viel Respekt davor. Der Flieger hat vollgetankt 21kg. Da sind 4 Liter Kerosin an bord, da darf nix schiefgehen. Ich habe die Phantom zwar permanent im Langsamflug bewegt, aber ich denke, da treten schon ordentliche Kräfte auf wenn man den Gashebel mal etwas länger vorne lässt .

Wenn ich die originalen Flügel so ansehe, dann mache ich mir wahrscheinlich eh zu viele Gedanken über die Festigkeit. Die Originalflächen haben ein Sperrholzgerippe von 2mm in der Hauptfläche, sowie zwei 5mm Balsaholme die oben und unten mit Kohle verstärkt sind. Die Flügelschale ist aus dünnem GFK. Wie es in den Außenflügeln aussieht, kann ich nicht sagen.

Es gibt halt letztendlich zwei Möglichkeiten für mich:

1. ich baue meine originalverpackte Ersatzmaschine auf mit dem guten Gewissen dass das Ding fliegt wie ein Trainer
2. ich schei** mich nicht so an und baue die Flügel aus Holz nach meinem Plan von René Lempereur und bau die eine oder andere kleine Modifikation ein und hoffe, dass das auch hält

 

[Berto]

Der Flieger hat vollgetankt 21kg.

Will try to keep mine as light as possible, and hope to come nowhere near 21kg with full....

 

[Northwoodhornets]

My F4 had 21kg with 4liters of fuel plus 800cc collector tank. The cockpit was or is almost fullscale with both pilots.
But i was impressed how slow the plane can fly with its 21kg.
When i rebuilt the wings with the plans from Renè, i have to stretch the wingroot rib about 3-4cm. I also have to adjust the complete wing area from the plans compared to my Jetlegend wings. This all will be a huge project.
The foam cores are ready as i said, exactly like the original wings but i don't know how to continue.
The wood wing version needs to be adjusted from the plans almost everywhere. That's why i didn't continue the project for the time.

 

[Berto]

Biggest reason for the max weight for me is the use of 2x a Kingtech K70 as power.
With 14kg of thrust a weight of 16kg will be sufficient to have a nice power to weight ratio.

And I think this can be done, have made a weight calculations and comes to a dry weight just below 12kg.
With 4ltr of fuel I just will be over de 15kg.

 

[Northwoodhornets]

Sure, this will be enough power for nice scaleflying. The F4 isn't a sportjet which has to climb vertically. My F4 had more than enough power with a 170 turbine and 21kg. I flew most of the time with 50% powersetting and this was more than enough. I only used full power during takeoff on grassfields.

 

[Berto]

Sounds good.

I wish there were more hours in a day so I can start with this project.

 

[Northwoodhornets]

Sounds good.

I wish there were more hours in a day so I can start with this project.

I totally agree with you

 

[Berto]

Due to circumstances my F-4 is for sale.
If interested just send me a pm.

 

[Berto]

There nobody is interested in this UR F-4 and I have a little more time I started with picking up this project again.
The fuselage fits in my car is no issue any more (before this I had a company van).

Goal is still to make is as light as possible so I can fly it of normal grass runways of about 100mtr in length.

I start with trying to install the main gears.

 

[Berto]