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RE: Designing a new pattern model
Hi Claude,
I would love to send you a kit, but first i want to make sure i can produce something that you will be happy with. There's a lot left to do, even before finishing the prototype, and i also have a small list of modifications that will make the building easier. I played racing sims since Grand Prix Legends was released, and of course rFactor too. I usually play CART/Indycar or LM prototype mods, but unfortunately i didn't have time for this lately. I know the virtualr web site and i check it almost daily. Thanks. |
RE: Designing a new pattern model
GO ALEX !
This is really nice !! Elias |
RE: Designing a new pattern model
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It finally starts to look like a plane...
I started working on the rudder, but it's not finished yet. The fin was glued to the fuselage using a laser level tool for alignment. I added the stringers on the top and bottom of the fuselage and took a few pictures with the cowling and canopy mold plugs to get an idea of the general shape and dimensions. |
RE: Designing a new pattern model
That is just TOO KEWL!!!!!!:D:D Very nice!:D
Bill Holsten Advantage Hobby Fliton Field Rep./Custom Airframes of America/Dragon Fire Custom Graphics/Duralite/Guardian America. |
RE: Designing a new pattern model
Excellent job !!!!
Mike |
RE: Designing a new pattern model
looks awesome....:D
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RE: Designing a new pattern model
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After a 2 weeks forced break, i finally found a couple of days to work on the model. I added the balsa skin to the top of the fuselage and took a few pictures to show the progress.
The wing tube, adjustable stab kit and incidence adjusters arrived yesterday but the stab tube is aluminium and seems very heavy. I'll replace it with a carbon tube but i need to make some sleeves for it. Fortunately the wing carbon tube and incidence adjusters are a perfect fit. |
RE: Designing a new pattern model
Wish I have your skill, can't wait to see the finished masterpiece ...
Adrian |
RE: Designing a new pattern model
Hi Alex
Have you some news about your awesome building ? Please what is the largest dimension of wideness of fuse ? Claude |
RE: Designing a new pattern model
Hi Claude,
At the moment i am only able to work during weekends, which makes the progress a little bit slow. Anyway, sheeting the fuselage with balsa is a tedious job and i think it took longer then assembling all the lasecut parts. I tried different techniques, like planking (covering with narrow balsa strips) and bending balsa with water just to see which one works best. Pictures will follow in a week or two. The fuselage is 160mm wide and 345mm tall, but i've been playing with a slightly different canopy shape that will reduce the height of the fuselage to 338mm. The rudder is about 400mm tall. |
RE: Designing a new pattern model
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It's finally time for some progress shots.
I added the battery tray and some balsa reinforcements for the main gear support. There's enough room in the front compartment even for 12s 5000 mAh batteries and i attached a few images showing the inside of the front section. I'm not sure how many G's our pattern models are pulling, but at -10g there will be almost 15 Kg pulling the battery tray, so i added lots of balsa reinforcements underneath. I decided to use Radiosouth 1/4 scale CA hinges and they arrived a few days ago, so i took a couple of evenings to finish the rudder. I also attached a picture showing the new canopy shape. It's a little less tall and more integrated into the shape of the fuselage. |
RE: Designing a new pattern model
any more news, I'm very interested in this
Rich |
RE: Designing a new pattern model
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I was just going to post an update today.
I've been busy working on the cowling lately and it took some time, but with some help from a good friend everything went well. First i had to finish the CAD model of the cowling by adding the lateral air intakes and making sure their shape will help extraction from the mold. The mold plug plywood structure was filled with depron blocks, sanded to shape and glassed. The next step was adding the lateral air intakes and smooth the edges with automotive body filler. Everything was finally sprayed with gelcoat and sanded again. The mold construction is classic, so i won't go into details. I attached a few pictures showing the main steps for the mold plug, the finished mold and the final part as extracted from the mold. |
RE: Designing a new pattern model
Magnificent work!
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RE: Designing a new pattern model
Amazing work, makes me want to get back into 3D design.
could you recommend any programs to start out with your model really reminds me of the Hyperion Helios but with more grunt and sexiness behind it. L |
RE: Designing a new pattern model
Subscribed!
I,d love to see you kit this design. Dave |
RE: Designing a new pattern model
Wow, big thumbs-up.
Adrian |
RE: Designing a new pattern model
ORIGINAL: lojik Amazing work, makes me want to get back into 3D design. could you recommend any programs to start out with |
RE: Designing a new pattern model
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Work on the model continues, and the canopy mold is finally done. I also designed and lasercut a frame and attached it to the fiberglass canopy. It still needs some work to make sure it fits perfectly, but it's not bad so far. I'm waiting for the CF landing gear to arrive and i also ordered 25g/m2 fiberglass cloth for glassing the fuselage.
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RE: Designing a new pattern model
beautiful job.....
but why did you select the airfoil you used?? |
RE: Designing a new pattern model
This really impressed me, Keep up the great work!!!!!!
I know I am interested! Ernie |
RE: Designing a new pattern model
Yea I can't wait for the next post....
Oh yea. I want one........!!!!! |
RE: Designing a new pattern model
what aerofoil did you use?
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RE: Designing a new pattern model
I used a NACA 64 A 012, which is a laminar airfoil. As far as i know, it is used on many pattern models these days. I'm not sure about the reasons why it was initially introduced, but i can take a guess why it is so popular.
If you look at the pressure distribution of a regular airfoil (like NACA 0012 for example), you will see that the pressure is very high close to the leading edge and drops quickly towards the trailing edge. This means that the resultant lift force is located closer to the leading edge and far away from the center of gravity, meaning that the stab needs to generate more lift to counter the moment created by the wing lift force. For a laminar airfoil the pressure is more equally distributed along the chord, meaning that the resultant lift force will be placed closer to the center of gravity and the moment created by the wing will be smaller. This way the stab needs to generate less lift and can be set close to 0 deg. incidence; the model will behave more "neutral" and probably won't need too much trim over a large speed envelope. |
RE: Designing a new pattern model
The lift center of a symmetric foil is always on 25 % of chord, with NACA 0012 and 64A012 too. The difference in pressure distribution affects on profil drag.
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RE: Designing a new pattern model
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The lift center position is not set in stone and it changes not only from one airfoil to another, but also with the angle of attack. I attached 2 images showing the pressure distribution for NACA 0012 and NACA 64012 and even if the difference is not as big as i remembered, obviously the position of the lift center is not identical.
Anyway, i could be right or i could be wrong about this - it doesn't matter too much. The airfoil has been used and it works well and according to other designers, the wing shape is a lot more important than the airfoil. |
RE: Designing a new pattern model
Hi Alex
You do awesome job. I agree with your choice about airfoil. Oxalys, Integral, mines and others have NACA64012 Regards |
RE: Designing a new pattern model
Hi Alex,
I hope you are well and may I wish you a happy new year. Looking good so far. It's a lot of work isn't it. What weight is the Fuz at this stage ? Brian |
RE: Designing a new pattern model
ORIGINAL: Alex Voicu The lift center position is not set in stone and it changes not only from one airfoil to another, but also with the angle of attack. I attached 2 images showing the pressure distribution for NACA 0012 and NACA 64012 and even if the difference is not as big as i remembered, obviously the position of the lift center is not identical. Anyway, i could be right or i could be wrong about this - it doesn't matter too much. The airfoil has been used and it works well and according to other designers, the wing shape is a lot more important than the airfoil. |
RE: Designing a new pattern model
The wing is 212mm wide at the tip (measured at the tip of the aileron) and 460mm at the root (measured along the side of the fuselage), which gives a ratio of 2.16.
I think 3:1 would probably be too much. The weight of the fuselage including the rudder, canopy and cowling is 1250g. I know it's probably on the heavy side, but it's the best i could do with regular balsa sheets. The canopy and cowling are a little bit heavier than i expected (110 and 115g ) but i'm going to use them anyway. Since it's my first 2m model, i have no idea about the final weight at this stage. There are a lot of experienced builders here, so i'm looking forward to hear your opinions about this. |
RE: Designing a new pattern model
I've heard on here that with an electric setup you need to aim for a fuselage and wing weight of under 2500grms, this should allow you enough room for batt's esc motor and radio gear.
I also read on another thread that wolfgang matt's Amethyst is over the weight limit with 5000mah batts so they have them for practicing and 4350 for competition |
RE: Designing a new pattern model
ORIGINAL: Alex Voicu I used a NACA 64 A 012, which is a laminar airfoil. As far as i know, it is used on many pattern models these days. I'm not sure about the reasons why it was initially introduced, but i can take a guess why it is so popular. If you look at the pressure distribution of a regular airfoil (like NACA 0012 for example), you will see that the pressure is very high close to the leading edge and drops quickly towards the trailing edge. This means that the resultant lift force is located closer to the leading edge and far away from the center of gravity, meaning that the stab needs to generate more lift to counter the moment created by the wing lift force. For a laminar airfoil the pressure is more equally distributed along the chord, meaning that the resultant lift force will be placed closer to the center of gravity and the moment created by the wing will be smaller. This way the stab needs to generate less lift and can be set close to 0 deg. incidence; the model will behave more ''neutral'' and probably won't need too much trim over a large speed envelope. It's called laminar because the flow is laminar in most of its surface, upper and lower. The reason ,well the center of pressure is located backwards, so the point of maximun speed fo the air is backwards too, and the turbulent flow that is generated after de C of P affects the wing in a smaller area than the non laminar airfoils, where the turbulent flow is generated nearer to the leading edge. |
RE: Designing a new pattern model
Hi Alex,
Yes getting on the heavy side. 1100 to 1250 glassed and painted would be good. My Oxai Ventura is 1120g painted inc the rudder. You mentioned waiting for glass cloth @25g for finishing. That will take a lot of resin to fill. I would sand & seal the balsa first, get 15g cloth and use lots of microballons. See BM3 threads here. If that gets much heavier you will not have a model that reflects the potential in your design. Also go to extremes to get light wings and tails to compensate some. |
RE: Designing a new pattern model
Hi Brian,
Thanks for the advice. I'll do my best to keep the wings and tails as light as possible, but the fiberglass cloth is already ordered and 25g is the lightest i could find at a reasonable price. Anyway, it's meant to be a cheap model and competing with Oxai models regarding weight would be too much to ask. |
RE: Designing a new pattern model
Hey Alex....
I just finished a [link=http://www.rcuniverse.com/forum/m_6875170/mpage_22/key_/tm.htm]SebArt AngelS 50[/link] and she has lightning holes in the fuselage. And an air dam located at the bulkhead near the trailing edge of the wing. Also 2 exit holes in the bottom. http://i459.photobucket.com/albums/q...r/DSC00753.jpg http://i459.photobucket.com/albums/q...r/DSC00754.jpg http://i459.photobucket.com/albums/q...r/DSC00755.jpg http://i459.photobucket.com/albums/q...r/DSC00757.jpg |
RE: Designing a new pattern model
Lightening holes would only work for a film covered fuselage, not a glassed one. The air dam is already installed inside the fuselage and i think it's visible in some of the photos. I will cut the exit holes later.
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RE: Designing a new pattern model
how much did the laser cutting cost?
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RE: Designing a new pattern model
Hi Alex
Just to share with you my little experience. On my wooden fuse (similar volume as your own), before putting glasscloth I put dope on balsa. Then I put 25 g glasscloth with resin. Weight with resin after sanding is about 100 g. But to get good finishing it's need to put primer. So primer is a litlle heavy 60 g. Paint is 40 g and clear coat is 40 g. 240 g total weight of finishing. I think to get lighter is to replace glasscloth and resin by "japan paper" with dope. It's less resistant but you 'll have no problem with electric motor because less vibrations than thermic motor. In this link see pages 25 to 27, finishing with silk, talc and dope (very long to do) : http://translate.google.com/translate?u=http%3A%2F%2Ff3a.sakura.ne.jp%2Fradioc ontroll%2Fspecial%2Fmake%2Faddction%2Faddction_01. html&langpair=ja|en&hl=en&ie=UTF-8 Claude |
RE: Designing a new pattern model
Thanks Claude.
It looks like the Addiction is about 125g lighter than my model at this stage. It's not too bad, but i have to consider the fact that the electric setup is heavier. I put dope and talc on the rudder this morning to see how it goes and it turned out fine, but the mixture was a little too thick and sanding it took some time. What was the dope : talc ratio for your mixture? I don't know exactly what dope is, so i used nitro laquer instead. I would also like to know if i can use this mixture for things like canopy fitting, where the layer needs to be a little thicker or is it better to use epoxy+ microbaloons? I will look for "japan paper" here, but if i won't be able to find it i'll have to use the 25g fiberglass cloth. The approximate weights for each finishing step is very useful. Foofydoo, the cost of laser cutting was about 200$. |
RE: Designing a new pattern model
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Hello Alex
Dope with talc is a mixture of "cellulosic liquid" with talc http://www.aeromodeles90.com/product...roducts_id=505 For getting thickness I use a very light mastic easy to sand like that http://www.topmodel.fr/product_detail.php?id=7418 See pictures for example. I bought in "material shop" because it is cheaper |
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