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Old Aug 20, 2007, 01:08 AM
Perpetual RC Newbie
Shazbot996's Avatar
Powell, OH
Joined Aug 2007
96 Posts
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My First Wing, and My First Scratch Build

I am trying out my first scratch build and my first wing all in one go! I have been poking around on this forum for quite a bit, and am trying out a design loosely based on another one I found on this forum. I'd appreciate any advice or feedback anyone may have on my design.

Overall wingspan is 36" with geometry as such:



I think it'll be a bit on the heavy side, but we'll see. I don't have a way of measuring it, so I'll not be sure. I wonder what the best way to weigh it is?

Quick pic of what it looks like now, mid-build:


I've also been thinking about the CG, and have found a couple of online tools that have been recommended to me. But they seem to assume that I know what %MAC I am going for... and I have no clue, except for reading on another forum to begin with 20-25%, and go from there. So I'll start with that, so we'll see.

I haven't even started thinking about a batt/esc/motor/prop setup for this. I don't have an extra, save a brushed 450 out of another Parkzone Spitfire I used to have. I will probably buy new for all of that, but I'd love it if I could run my existing 3-cell LiPo 2100A batteries... but I believe those are too much for this application.

Any advice would be appreciated... looking to get the airframe completed tomorrow, and then start shopping the electronics and such.

Thanks!
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Old Aug 23, 2007, 01:02 PM
Perpetual RC Newbie
Shazbot996's Avatar
Powell, OH
Joined Aug 2007
96 Posts
Another update, in case anyone is interested!

If anyone is interested in seeing another scratch build project update - see here:

http://www.badmotorfinger.com/wiki/RcFoamWing1


I am about ready to maiden this, my first ever wing build... and my first ever scratch build! I think it will fly!

I have some numbers in now... My AUW is 18.2 Oz., and if I run the numbers on the wing loading, that comes in at 9.05 Oz./Sqft, if you include the whole wing area... or conservatively, 12.07 Oz./Sqft (using 75% of the wing surface). I can't tell if this is good or bad, but I have seen heavier wing loadings thats's for sure. So hopefully the funky shape of this thing won't prohibit it flying! We'll see... glide test coming up once I get the winglets on!

I marked the front of a roughly 1" range between 25%MAC and 35%MAC - I hope that the true stable CG is in this area. I can play with it by moving the battery around, and it seems very effective in letting me tune it!

Here's a quick pic of what she looks like now!




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Old Aug 23, 2007, 01:24 PM
Fatboys can fly
Mark Mc's Avatar
Greeneville TN
Joined Apr 2007
74 Posts
Nice looking first wing build.What motor did you choose? It looks like an E-Flite six to me,if it is I think you will be pleased with the power.Be sure to get the cg dialed in before you go WOT in case it climbs or dives under power the thrust angle might need to be adjusted.Good luck with the maiden.
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Old Aug 23, 2007, 02:30 PM
Perpetual RC Newbie
Shazbot996's Avatar
Powell, OH
Joined Aug 2007
96 Posts
Thanks! Yeah it's a six series... I guessed on it... was hoping for mad power as long as I get it all balanced and aligned happily.

I almost killed myself with that mad power last night. I had the motor power leads reversed as I had not yet run the motor. When I powered up the plane and was testing out control surfaces etc., I accidentally reversed the throttle servo causing it to go to WOT instantly. Well, like an idiot, I had the screw in, and it took of loudly directly into the radio that was in my hands. It broke the prop, and bunged up the back of my radio, but didn't even touch me. I can't believe it. I could have been severely torn up. *sweats bullets*
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Old Aug 23, 2007, 08:03 PM
Gone to far to come back
dan.k's Avatar
FBGA
Joined Jul 2007
29 Posts
great job! checked our your website. Good stuff! GL on ur maiden!
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Old Aug 23, 2007, 10:36 PM
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cytochrom's Avatar
Phoenix Deer Vally, Arizona, United States
Joined Sep 2004
148 Posts
Congrats!!!
That wing looks teriffic! I second the need to be properly C G' ed.
I cant till if there is any wing flex of If you'll need a spar . That wing looks so good Ill bet that you did all the needed preparation
Good luck on your maiden.
Ed.
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Last edited by cytochrom; Aug 23, 2007 at 10:50 PM.
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Old Aug 24, 2007, 08:37 AM
Perpetual RC Newbie
Shazbot996's Avatar
Powell, OH
Joined Aug 2007
96 Posts
Thanks guys. Well, I had my maiden flight last night, and it flies great! But a lot different from my regular planes, so I had to get used to it. I thought at first that it had a tail-heavy problem, but then I realized I had my reflex set way too high... so I dialed that back, and she turned into a very predictable rocket ship. With that six series motor... omfg I think it is too much! This thing seriously motors! 3D at 1/3 throttle.

I realized also that I need to beef up my elevon surfaces & controls. They are too "flexy", and with the speed this thing achieves... literally the control surfaces become dangerously unresponsive at WOT. I had a few near-misses with this...

But this thing sure can take a beating! I managed to lodge it in the top of a tall tree before I got the hang of it
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Old Aug 24, 2007, 12:06 PM
Fatboys can fly
Mark Mc's Avatar
Greeneville TN
Joined Apr 2007
74 Posts
Congrats on a successful first flight,I hope the tree did'nt keep it lol. I knew you'd like the Six. My son and I have one each on 2 different small wings,the 34in Mini-Bee my son flys on 3s has been radared at 119 mph so yes rigidity of both the wing body and the control surfaces are a must.I think this motor is underrated or maybe just underused,but we've had nothing but success with ours. By the way do you have the 2700kv or the 2000kv?
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Old Aug 24, 2007, 01:02 PM
Perpetual RC Newbie
Shazbot996's Avatar
Powell, OH
Joined Aug 2007
96 Posts
I have the 2700Kv version. 110 mph! Wow... I wish I knew where to find my own radar gun... how cool. I'm not sure how fast mine is, but it definitley amazed me. I had a small crowd gathered oohing and aahing over it... and I was only at 1/2 throttle... then I pointed it straight up, and gave it WOT. They all gasped. So did I.

Yeah the wing rigidity is not a problem - I have a stout carbon spar in it... but the elevons need some serious help. I made the most gimpy hinges for it ever, and I put the control attachment too far to one end. So I have to figure something out that's better. The material is pretty stiff... but I'd need to attach my control horn closer to the center. Less leverage that way.
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Old Aug 25, 2007, 05:33 AM
Slowly Approaching 1,000
Detroit (area), MI
Joined Mar 2004
923 Posts
Wow, nice little flyer thingy you got thar. ;-)

I especially like the compound miter cut you have where the 2 top pieces are joined. Very nice job.
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