[Ultralajt]

Hi!

Last winter I design and build CNC router to help me with building RC aeroplanes.

With this machine I finnaly can afford some design features of my models that previous was not possible (doing just by hand tools).

My latest RC model project is a 1:5 scale vintage glider from 1953.

Here are some of the photos, that show, many parts made on my CNC machine. They connect one by another, and assembly of the model goes pretty fast. It is also acurate and I am very satisfied with this machine.

[Glidergider]

Beautiful airplane. What is the wingspan? Parts look great and the assy is looking fine.

[Ultralajt]

Beautiful airplane. What is the wingspan? Parts look great and the assy is looking fine.

It is 1:5 scale glider and it will have 3,2m (~126")wingspan. Fuselage length is 175 cm (~69").
RTF weight (planned) somwhere between 3,7 and 4 kg (~8-9 lb).

[One of Many]

126" span is quite impressive. Very nicely done!

Was this just from the 3 view drawing or did you have more plans?

Is this for slope soaring, high-start or tow line?


Don't be shy, I'd sure like to see it in a flight video posted here or at least linked.

Have you considered a geared motor and folding prop? I know it wouldn't be scale realism and all, but it sure would open up the opportunity to fly it more.

The wing seems to have a high angle of attack in the side view. Or is that just the tips shown?

Congrats on the CNC build too!

DC

[Ultralajt]

Was this just from the 3 view drawing or did you have more plans?

I made plans by myself.

Is this for slope soaring, high-start or tow line?

First just aerotowing on flatlands, but if model show nice flight (and landing) performance, I will go on the slope also.

Don't be shy, I'd sure like to see it in a flight video posted here or at least linked.

Maybe at end of august or early in september....

Have you considered a geared motor and folding prop? I know it wouldn't be scale realism and all, but it sure would open up the opportunity to fly it more.

No way. It is a scale sailplane. Propeller, even folding one, will spoil the apearance of the model.

The wing seems to have a high angle of attack in the side view. Or is that just the tips shown?

Wings have really high angle off attack regarding the fuselage, and fuselage will have nose down atitude in flight. It will look very scale. The wing twist is 3° and that minimize for some degree the main chord angle of attack. I think, for such a slow flying scale sailplane, I cant afford 1,5°-2° difference between wing and elevator AOA.
Now the AOA diference is 3°at root. Wee will see how it will fly and made corrections on the plans if necessarry.

Congrats on the CNC build too!
DC

Thanks. MCNC helps me a lot to build this model. So many formers with so many holes.. it would be a nightmare to cut all that with a handsaw (like on my previous modells...I always avoid to design exotic formers..but now all is possible).

I open this thread about my newest RC model just to show what is possible to achieve with home build, cheap, easy to build and rather primitive CNC machine.
I hope that this will give courage to those who would like to build CNC, but still hesitating....

Mitja
P.S.: model building threads on RC modeller forums:
RETROPLANE (reserved for vintage models): http://www.retroplane.net/forum/viewtopic.php?t=2613
RC.groups (largest RC forum): http://www.rcgroups.com/forums/showthread.php?t=1076984

[One of Many]

Thanks for the detailed response Mitja.

I have several R/C planes myself. Just not as much time to fly as I used to. My Glider is electric. It is a Goldberg Electra, if you have seen those in the mag's. Basically a Gentle Lady with a motor in the nose. Only 78" span, but quite a nice flyer for just rudder and elevator controls. I have thought about buying a new wing kit to modify to an aileron wing. Too many other projects I guess.

Looking forward to the video and keep the progress pictures coming.

DC

[Kroko]

Great looking plane. I'm sure it will be a masterpiece like all your planes.

Andrej

[Ultralajt]

Great looking plane. I'm sure it will be a masterpiece like all your planes.

Andrej

Thanks Andrej!

A short relaxing video... walkaround my (unfinished at the moment) model :

[ame="http://www.youtube.com/watch?v=Bnt_DUebhgk"]YouTube - walkaround-unfinished RC scale model SZD-10 Czapla[/ame]


Mitja

[Ultralajt]

Current status of the model... Almost Ready to Cover:

[Ultralajt]

Model is now almost ready to fly:



I am looking forward to have maiden flight this weekend.

Mitja

[Glidergider]

Wow, great looking covering.

[gumush]

that looks good, which software did you used for ?

plan to cad ? Cad to cam ?

[Ultralajt]

that looks good, which software did you used for ?

plan to cad ? Cad to cam ?

I design model in CAD. So, no transfer from drawing to cad needed....
Machine is driven by Mach program: http://www.machsupport.com/downloads.php

You can download free Mach program, but there is a !drawback" as Mach2 is limited to 1000 lines of Gcode until licensed.
Anyway, 1000 lines of G-code can be used for simple parts and low parts count.... and for discovering of the machine possibilities.

[Atomic_Sheep]

Are the slots for the spars using a CNC router method square? Or did you have to sand them square for the spars to fit in nicely?

[Ultralajt]

Are the slots for the spars using a CNC router method square? Or did you have to sand them square for the spars to fit in nicely?

Insisde corners of the slots for spars are rounded. Radius is half diameter of the mill bit. I use 1,5 and 2 diameter mm milling bit (depending of the material), so radius in the corners is 0,75 or 1mm. (~0.03-0.04")

On the balsa ribs I left corners as they are. When you press spruce spars in balsa these small radius in corners gives up and dont represent any problem at all.

On the plywood, I use a fine small rasp (file) and one or two strokes at each corner is enough to clean it and prepare for glueing.

You cant avoid that! I saw fellows that arrange cuting path in such way that in the very corner of the part mill goes into a corner for about half od the mill bit diameter. Then corner is non need to clean but I dont like that cut as it can weaken the part (stress rising detail)

Mitja

[Atomic_Sheep]

Just as I had suspected... thanks.

[Ernie34]

VERY NICE..... I am hoping that once my machine is done I will be able to do the same.


Ernie

[dpuch]

An alternative for the corner, plunge 20% of the tool diameter 45° into the corner.
So a 2mm dia. tool go 0.4mm at a 45° into the corner. This would leave a 0.3mm (15%) deep by 1.4mm (70%) long cut on both sides of the corner. Stress wise as long as you have more material than that along both sides it is probably a better option than 50% in on one side only.