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Omega

Omega Slope Model Build

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Omega

Well here goes.

I wish to share with you the build of my V-Tail slope model.

Its called the Omega. (3 View attached)

The build will be slow (I'm not fast), but I hope to share with you guys some of my build processes that I have used in the past, see if I'm doing it right or not.

I'm not going for an uber light build here, as the model is based on a 30 year old F3B/F type design/look.

Using techniques freely available in my garage and will be a complete labour of love.

Any questions/suggestions feel free to pop them over.

Aiming for around a 2.75Kg build weight, so should quite happily go off of a slope in a moderate to high blow. (Ballast tubes to be added when I have built the fuse, as the 8% wing is way to thin to put anything meaningful into it.)

Please excuse the 3 View, I only have visio 2010 and its a bit clunky for compound curves.

Omega-V1.pdf

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Omega

Sorry forgot to add this picture.

MH33 Foam cores and other bits and pieces from Foam wings (As I am utter rubbish at cutting cores) (Maybe someone could share there process ?)

FullSizeRender.jpg

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Brett82

Im very interested in seeing how you get on with this and how you do it. Thanks for sharing. :yes:

Brett

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Omega

Cheers Brett,

I haven't built any wings larger then 2 meters in the past, so a 3 meter wing will be interesting, especially one this thin.

Also the core are fairly fragile at the trailing edge, so I need to be very careful will its bagged.

I hope to make a bit of progress in making some tools to cut the spar caps this weekend and marking the cores out ready for adding the spar.

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Brett82

Sounds like some delicate work there. I've always liked the idea of making my own model but I was going to try do it the other way. I was thinking of forming a foam plug, covering it with a Pattern-Coat Primer and Hi-Gloss (see the link below) and then making some female fiberglass molds from the plug. There is a nice video on the process on that link too. Would then need to layup the model inside the mold for the normal "hollow" wings and fuzz (not sure on correct term)

http://www.easycomposites.co.uk/#!/patterns-moulds-and-tooling/pattern-making/composite-pattern-coat-hi-gloss.html

Its a lot of work for an untested design though, your way will be better for prototypes before going to all that effort so it will be good to see how you do it. 

This was my design, done in Wings3d, not the best program but its free. I would want to change the nose a bit though.

 

20160128_082110.png

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Omega

That's a whole load of dedication for like you said an untested design.

I'll stick with the old fashioned build, its not like I'm going to do any contest flying with it, just for fun and to see if I can make something.

If you decide to do it please share the process.

You still have to vac bag the wing skins into the mould.

New DLG's are cnc foam cores laminated into a mould like hollow moulded models.

Trouble with hollow moulding if you cack the spar up the wing will be like jello.

Especially over a span such as this.

Modern carbon models are so stiff of the span and light, how they do it I have no idea.

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Brett82

It would be a lot of work which is why I'm looking forward to seeing your build.

Im terms of stiffness on hollow molded wings I may be wrong but they get it from two things. A strong spar running down the wing made normally of balsa and unidirectional carbon and the normal way of getting strength in carbon, layers with a core material. So top skin carbon, layer of thin glass, core material (airex or 1mm balsa sheet) then another layer of carbon or glass. The core material gives thickness without using too many layers of carbon or glass and is less weight. Thickness helps with strength. 

Anyway I'm hijacking your thread, sorry mate. Looking forward to seeing how you do it. 

Brett 

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Omega

No worries. 

 

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Omega

I won't be building for lightness but if I can save weight I will try to. 

Im keen on accuracy first weight reduction later. 

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Omega

So progressing now. 

Marked out the spar cap on starb wing. 

Then used a steel rule as a straight edge. 

Made a tool from 3/8th's balsa with 180 grit sand paper and got to work. 

Smooth strokes and half an hour later you have a recess for the spar. 

Only three more sections to go, flip it over and do the bottom. Lol

 

ita going to take a while to do the rest so stand by. 

IMG_7535.JPG

IMG_7536.JPG

IMG_7537.JPG

IMG_7538.JPG

IMG_7539.JPG

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Omega

Had some grabbing with the tool but generally the spar caps have come out ok. 

Will back fill with carbon rovings and epoxy. 

IMG_7540.JPG

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wookman

I will always admire someone who is prepared to spend the time and effort to scratch build such a machine. Well done Omega. 

Weight really will not be an issue as you will most likely fly it ballasted anyway! :popcorn:

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Brett82
8 hours ago, wookman said:

I will always admire someone who is prepared to spend the time and effort to scratch build such a machine. Well done Omega. 

Weight really will not be an issue as you will most likely fly it ballasted anyway! :popcorn:

Me too, anyone who tries to put something back into the sport by doing something like this is ok in my books.

Hope to get some more updates soon, I know it's a slow project though so no pressure. 

Brett 

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Omega

A real labour of love. 

Which is taking its time. 

Just working some things out before cutting any more foam. 

 

The spar caps are all cut out but I need to work out the joiner before I cut into the foam. 

More details soon. 

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Omega

Sorry there hasn't been much progress seen in the build for the last week. 

I am now at a critical point in the build. 

Spr has been designed it's a bit of a rough calculation and then add on a % for error and the human 'err' factor. 

Joiner strength. 

My plan is to use a 3/8" steel bar to EN1A which will be around 350 mm long. 

The EN1A spec gives a tensile strength of 450Mpa which is around 65kgs per square inch. 

The cross sectional area is defined by pi * r squared. (Due to it being a circle)

3/8 = 0.375" x 25.4 = 9.25mm diameter. 

Radius is 4.625mm. 

(3.14 x 4.625)2 = 223.65mm2 which is around 7/8".

So tensile strength of joiner is

65kgs/sq.in x 0.875 = 56 kgs/sq.in  

 

now 1.1mm mono winch line is rated at around 80lbs tensile strength which is around 40kgs (by the time it has stretched a wee bit)  

thats gives me around 16kgs head room  

that will do me  

thoughts ?

 

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mikef

Oops - a few mistakes in there.  I'll correct it later.  Can I assume the joiner is on the centre line and takes bending loads?

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Omega

Typos. 

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Omega

Just realised I've used the wrong calculation. Oops. 

Ok if I'm using it as a link in the line. Lol

 

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mikef

Correct, If the joiner is on the centre line and takes bending loads, you need a bending strength calculation, not a tensile strength calculation.  You'll also be better off using the yield stress for the material and treating the bending limit as a 'plastic hinge' calculation.

Are you OK with that?

 

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Omega

Yeah just looking now. 

Lol

ta. 

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