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RE: Designing a new pattern model - 1/11/2010 8:15 PM   
Rhilluk



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Status: offline 		Just been wondering. I see you made the fuse out of laser cut liteply, sheeted over with balsa.

What size liteply did you use and what size balsa sheeting?

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RE: Designing a new pattern model - 1/11/2010 11:17 PM   
Alex Voicu


 

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Status: offline 		It's not liteply, it's 1.5 mm regular plywood. Liteply usually comes in thicker sheets; minimum thickness of liteply available here is 4mm, with the same weight as the plywood i used.
Balsa sheeting is also 1.5 mm.

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RE: Designing a new pattern model - 1/14/2010 4:37 AM   
mithrandir



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Status: offline 		the expected problem with an airfoil designed for full size aircraft... particularly one with intended extensive laminar flow is
that the flow can remain laminar beyound the onset of the adverse pressure gradient... and will seperate more easily... then
after seperation, will transition to turbulant and reattach... the so called "Laminar Bubble"..... Excessive drag and even a hysteresis can result.....
it is possible, that the vibration of the motor is enuff to cause transition... all it takes is like a .004" thick edge of
tape or a monocote seam to cause transition...

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RE: Designing a new pattern model - 2/5/2010 11:16 PM   
RemsiuX


 

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RE: Designing a new pattern model - 2/6/2010 8:09 PM   
Alex Voicu


 

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Status: offline 		I made some progress, but i don't think it's going to be visible in the screenshots. The fuselage went through many filling and sanding sessions, the wing and stab sleeves were positioned using the laser level tool and glued inside the fuselage, the canopy and cowl fitting is done so what's left to do is glassing the fuselage and painting it. Are there any good tutorials about glassing a fuselage? I made some tests on a piece of balsa but i just can't replicate what is described in the Black Magic build thread. I was very careful with the microbaloons, but i couldn't apply them evenly and they seem to create "lumps" here and there.

Unfortunately the progress will have to stop here for a while. My job requires a 2 months trip to France, so i won't be able to work on the model until i get back (around early April). Too bad, because i was planning to have the maiden flight around that date and this trip will set me back considerably.
Anyway, in the last couple of weeks i've been working on a new version of the wooden structure, which should be almost 200g lighter and easier to build. I hope to be able to finish the 3D design before going to France because a friend of mine is very anxious to start building it.

< Message edited by Alex Voicu -- 2/6/2010 9:21 PM >

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RE: Designing a new pattern model - 2/6/2010 9:00 PM   
papaone



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Status: offline 		Hi Alex

If you want some informations as RC planes fields, RC shops near the place you will go in France ? don't hesitate to ask me. I live in the south of France near Marseille.
Claude


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RE: Designing a new pattern model - 2/6/2010 9:21 PM   
Alex Voicu


 

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Status: offline 		Thanks Claude, i will PM you once i find out more details about my trip. If the weather allows and you guys go to the flying field, maybe i'll come visit some week-ends.

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RE: Designing a new pattern model - 2/7/2010 11:09 PM   
Shahid



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Status: offline 		Hi Alex really nice work.

I use Solidworks also, but am intrigued as to how you have modelled the aircraft with so few sketches! Would I be correct in saying you start with a solid lump and then chop it up to get the required parts?

My main question to you is this, when modelling fuselage sides that are curved, how do you transfer these curved surfaces to a flat shape for CNC cutting?

Many thanks!

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RE: Designing a new pattern model - 2/8/2010 12:04 PM   
Alex Voicu


 

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quote:

ORIGINAL: Shahid

Hi Alex really nice work.

I use Solidworks also, but am intrigued as to how you have modelled the aircraft with so few sketches! Would I be correct in saying you start with a solid lump and then chop it up to get the required parts?

My main question to you is this, when modelling fuselage sides that are curved, how do you transfer these curved surfaces to a flat shape for CNC cutting?

Many thanks!


I prefer to work with surfaces and i don't use solids for the external shape of the model. I usually start by creating sketches of the side and top view of the fuselage and continue with the transversal sections, as you can see on page 1 of this thread. The lower part of the cowling is a little more difficult and i have to come up with a specific modelling technique each time i design one.

Once the external shape is finished, i start working on the internal structure using solids. All curved faces that need to be flattened later for lasercutting are modelled using the sheet metal module from Solidworks. It's a little tricky as sometimes it refuses to flatten the curved plates for no aparent reason, but with a little work and a little bit of luck, it is possible.

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RE: Designing a new pattern model - 2/8/2010 3:43 PM   
Shahid



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Status: offline 		Thanks for the info, so is the "shell" model purely for visual inspection, and you derive the structural parts from the sketches?

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RE: Designing a new pattern model - 2/8/2010 4:26 PM   
Alex Voicu


 

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Status: offline 		Actually the sketches used for the modelling of the "shell" have nothing to do with the structural frames. When creating a new transversal frame, i simply create a new sketch by intersecting the "shell" with the plane of the sketch.

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RE: Designing a new pattern model - 2/8/2010 5:08 PM   
Shahid



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Status: offline 		Haha, that's a smart way to do it. I've doing a similar thing when making shockies but my "proper" model experience extends only a funfly:




Your method defines the plane in which you wish to draw your former for example, but can you use the shell to determine the "outline"? One last thing for now, though I find your work is of excellent quality and well thought out so no doubt I will be back for more, the curved fuselage sides are determined through what method? As I cannot see how the shell can play a role here?

This is all helping me to get my 120mm EDF project finished, I've got a solid fuse just need to model the wings/empennages!

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RE: Designing a new pattern model - 4/24/2010 7:06 PM   
Alex Voicu


 

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Status: offline 		I recently returned from my trip to France and started working on the model again so i'm back with an update. I have both bad and good news so here we go:

- The bad news: I really messed up the finishing process for the wood fuselage. Trying to fill all the gaps and seal the balsa surface, i covered the fuselage with a layer of dope and talc mixture. This worked perfectly for the rudder so i thought it would also work nicely for the fuselage, but it turned out it to be a bad decision. The balsa skin was softened by the dope and created slightly concave shapes in all areas where the balsa was curved and forced to follow the shape of the formers. To make things worse, this also results in a lot of added weight because it's difficult to sand the excess mixture in the concave areas.

The only solution would be to strip all the balsa sheeting and start over, but it would take too long and, as you will see, i have other plans. I won't give up on the wood version and the plan is to finish the fuselage as it is and get the model in the air as soon as possible. I mounted the landing gear and tailwheel and quickly fixed the canopy in place with a few screws:

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RE: Designing a new pattern model - 4/24/2010 7:09 PM   
Alex Voicu


 

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Status: offline 		- The good news: a full composite fuselage should be ready soon. The mold plug was made by me a long while ago and while i was away a good friend of mine finished the molds. The fuselages that came out from the mold so far are a little heavy (~900g), but we're working on it. We already bought better materials and everything we need for vacuum bagging, so i expect weight will soon improve.
I took a few pictures during the mold plug carving process, so maybe i'll post them here to show the main steps.

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RE: Designing a new pattern model - 5/31/2010 4:23 AM   
Shahid



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Status: offline 		Nice work, good to see you are still progressing with the model

Just a quick question, I notice you have curved fuselage sides. How did you draw these in Solidworks then transfer this to a "flat" template for the CNC machine?

Thank you!

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RE: Designing a new pattern model - 5/31/2010 8:44 AM   
Alex Voicu


 

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Status: offline 		I used the sheetmetal module in SW to create and flatten the curved fuselage sides. PM me if you have more CAD related questions.

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RE: Designing a new pattern model - 5/31/2010 10:38 PM   
Alex Voicu


 

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Status: offline 		Small update while we're back on the front page: i cut the air intake holes for the cowl, added some screws to hold the canopy and cowl in place and started working on the stabs.
I still need to add the hardpoints, hinges and servo support, but i'll do that later when i'll get the servos. I'm quite happy with the weight so far (76g each stab, incidence adjuster included). Anhedral angle is 5deg.

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RE: Designing a new pattern model - 5/31/2010 10:44 PM   
Alex Voicu


 

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Status: offline 		And some news from the composite front: popped another fuselage from the mold, but it's still not good enough. I couldn't get the vacuum installation to work without leaks, but we'll see about that later.

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RE: Designing a new pattern model - 6/1/2010 4:15 AM   
skywalllker



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Status: offline 		Very nice job Alex, looking forward for more updates from you.

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RE: Designing a new pattern model - 6/1/2010 8:40 AM   
highfly3D


 

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RE: Designing a new pattern model - 7/1/2010 10:06 PM   
Alex Voicu


 

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Status: offline 		Wings took a little longer to build, but they are almost done now. I thought i got used to the size of the fuselage, but now with the wings in place the plane seems huge and i can hardly find enough space for it in the room. I still have to add the servo supports and the aileron hardpoints, but i'll do that later when the materials for the control rods will arrive.

The incidence adjusters i bought were junk, so i had to manufacture them. It wasn't very easy but with the help of a few friends who let me use a lathe and a small CNC machine, the result seems airworthy.

I took some pictures during the building process and i thought i'd post them here.

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RE: Designing a new pattern model - 7/1/2010 10:08 PM   
Alex Voicu


 

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Status: offline 		More images:

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RE: Designing a new pattern model - 7/2/2010 4:30 AM   
dhal22


 

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RE: Designing a new pattern model - 7/2/2010 9:35 AM   
highfly3D


 

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Status: offline 		awesome job... great looking model

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RE: Designing a new pattern model - 7/21/2010 5:02 AM   
mithrandir



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Status: offline 		in the future, you will find it usefull to make the flanges of the mold a little wider....

if the plane has some peculiar stall qualities.... try adding Zig-Zag tape to the top and bottom leading edge say.. around 10 to 15 percent of the cord back from the leading edge.

Plane looks good.

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