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Old Nov 22, 2012, 02:37 AM
Hot glue held together by foam
United States, WA, Vancouver
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Originally Posted by Dan_D View Post
While working on the NEKKID SE, having built the first one without much concern for weight, now I am shaving every gram.

In that mode, I had a thought... I can possibly save a few grams by replacing a solid balsa wood stick motor mount with a composite beam. My guess is that the greatest forces on this beam are going to be a vertical bending moment and torsion. With that in mind, I thought that a foam core faced with balsa would have the properties of a box beam with the added advantage that the foam would somewhat help to resist the dimensional constriction when the box torqued... although I don't hold out a lot of hope for huge strength gains because of that factor...

So, I made up such a box beam, and it seems rigid enough... but then again I haven't clamped it into a test stand and tested to destruction. So, I have no clue if this is a known solution, a Really Bad Idea , or a bloody waste of time.

I suspect I should just make a NEKKID SE base model, and then go on to rev 2, 3, 4, 5 once I can actually fly something.

Suggestions ?

And yes, I'm driving to Dayton... with planes, tools, hopes and fears. And a video cam.

Ad Astra, per SE
It sounds like your box beam will work alright - go for it ! NEKKID base model sounds good , too ; I suspect you're the kind of guy who's going to keep building planes for years to come ! I've built about a dozen SE's since the first one in July - some for friends and a few I've sold .

One of the first guys on RCG to make an SE is Nightstone . After his first one he went on to make rev 1 , 2 , 3 and so on . He's made an elevon version , an aerial photography version , etc. He's become a DTFB plane making maniac !

Hooray for the video cam ! Can't wait to see the video !

Have a great Thanksgiving , Dan !

Al
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Old Nov 22, 2012, 01:21 PM
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It sounds like your box beam will work alright - go for it !

Al
Well, I decided that one can't really know without testing, and since it only took me 15 minutes to make the foam core box girder out of foam and balsa, I could sacrifice the first one. Good thing I did.

Test 1 - resistance to torsional forces (such as forces arising due to rapid change of the rpm of the propeller) I clamped it lightly in a vice, and then clamped a lever arm (stick) on the beam 6 cm from the vice. I attached a soup can on a string, and loaded it with heavy 3/8" nuts until the beam showed a twist of approximately 10 degrees. The angle was not carefully measured as I was just going to compare it to a solid beam, and not obtain absolute d(angle)/d(weight) figures. The set up was repeated with a solid balsa beam, and the angular deflection was noticeably less. Conclusion - the box beam is more twisty.

Test 2 - resistance to bending forces. Since the balsa beam was still in the vice, I simply hung the can at the end of the beam (8 cm) and added weight until the beam showed signs of incipient failure, and then continued adding weight until it failed. The composite box beam was then placed in the apparatus and the experiment was repeated. The box beam failed suddenly at roughly 60% the total weight required to break the solid beam. The failure was also rapid and without showing any signs of incipient failure.

Conclusion - this first attempt at a foam cored box beam was a failure as far as resistance to torsion and bending failure. Considering the well known qualities of box beams this is a bit of a surprise. If one were to pursue this further, one might wish to examine the nature of the bonding between the facing elements, and the bonding of the facing elements to the foam core. Inadequate bonding would lead to localized stress at those points where the beam acted as several independent elements, each of which would be very weak. Future experiments might include strengthening with carbon fiber and CA, etc...

However, the NEKKID SE is getting a solid beam... tapered.
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Old Nov 22, 2012, 02:49 PM
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Hi there Dan I'm going down the same road you are. I quickly figured out I better build my own stuff to crash before buying any more expensive skyhawks. In my case 2 sky surfers virtually the same plane. Lucky me the dollartree is a mile from my house. I tried Ed's taping the paper but the planes are so heavy you need a heavy motor to run them. I'm now stripping the paper and using 24 gram motors getting the weight down to 12 oz or less. A couple neat planes you might try are a dart or a kesl wing. I'm having pretty good luck so far they are taking a beating but holding up ok
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Old Nov 22, 2012, 03:00 PM
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The nice thing about light planes is they fly slow enough you have more than a nanosecond before it lawn darts. I usually do something with my thumbs that puts my plane into the ground at about 400 mph. Now my crash speed is down to about a hundred. I'm getting good at cutting foam though.
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Old Nov 22, 2012, 06:10 PM
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Hi there Dan I'm going down the same road you are. I quickly figured out I better build my own stuff to crash before buying any more expensive skyhawks. In my case 2 sky surfers virtually the same plane. Lucky me the dollartree is a mile from my house. I tried Ed's taping the paper but the planes are so heavy you need a heavy motor to run them. I'm now stripping the paper and using 24 gram motors getting the weight down to 12 oz or less. A couple neat planes you might try are a dart or a kesl wing. I'm having pretty good luck so far they are taking a beating but holding up ok
I'm glad you understand. The Missus is not convinced of the wisdom of my approach - all she sees is the increasing number of planes without any really successful flights. I keep assuring her that "this time for sure". I feel like Bullwinkle J Moose trying to pull a rabbit out of a hat. Fortunately she's a fairly mellow and accepting type... but she does occasionally do things such as ask if I've paid the mortgage this month...

I found the KESL wing... I am somewhat ambivalent about the K-form aerofoils. (Ambivalent?? I'm too green to HAVE an opinion... *sheesh* ) I thought they seemed like an amazing idea when I first saw it, but further reading showed that NASA (NACAP?) had tested them and found bad lift/drag ratios. Maybe that's only important for higher speeds, or lower power/weight ratios... But following that I found the Armin wing which seems almost as simple, although a bit heavier because of the tape. Maybe one could make NEKKID Armin wings. Or just use a bigger motor. Anyway, I still have to get some flight time on the SE before I serious think about anything else... or the previously mentioned Missus (who is a molecular biologist) might develop some new bug that will leave her in possession of my life insurance.
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Old Nov 22, 2012, 11:39 PM
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Looking at my wing it doesn't look like it could fly at all but fly it does nice and slow and gentle if I wick up the throttle it gets kind of squirrely. After three battery packs of showing off for my grandkids I finally dumb thumbed it into the ground trying barrel rolls ouch totalled it. I'm out two bucks for foam. I will fish out my servos and parts and begin a new one less tape, less paper maybe a small wood dowel for reinforcement but its a sweetie. And it looks cool. Hey if your going to crash at least look cool for the kids. That se thing is well here it is, its ugly. Somebody had to say it.
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Old Nov 23, 2012, 01:47 AM
Hot glue held together by foam
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Sue

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That se thing is well here it is, its ugly. Somebody had to say it.
Ok , I'll go ahead and change the name to SUE - SUPER UGLY EASY !
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Old Nov 23, 2012, 02:47 AM
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It's 2:40 AM, and it's FINISHED

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Mine weighs 290 grams without battery , but I made it with just one elevator servo and a Y pushrod going to the elevators - stole that idea from FlyingW ! With a 1300mah 3s battery it's a nice , slow , floaty flyer .

Al
My NEKKID SE is finished in time for the drive up to Dayton tomorrow.

AUW - 305 grams without battery. Close, but heavier. I used an extra servo, so that explains 9 grams of difference.. so mine is 6 grams heavier. I used a little velcro here and there, bamboo pushrods instead of carbon fiber. ALSO, my only Y harness is too long, so I had to fold it back and forth and for appearance sake I stuffed it in a bit of un-shrunk heat shrink. Yeah, that's probably 3 or 4 grams right there. I suspect I might have used a bit more hot melt here and there.

Anyway, it's a LOT lighter than the 400+ grams that Lawn Dart weighed.

So, tomorrow... repaired Hawk Sky, Lawn Dart, and NEKKID SE are heading to Dayton... Weather is supposed to be good. Maybe we'll visit the AF Museum on Saturday and go oogle the XB-71, and dream and plan.

ALSO... rumor has it that there are SEVERAL local hobby shops up there AMAZULATING !!! ASTOUNDIFYING !!! I can buy a shorter Y harness. I can get a stronger motor for Lawn Dart. I can spend money !!! I have a credit card, I can spend money we don't have yet !!! Resistance is futile, the contents of your wallet will be assimilated.
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Old Nov 23, 2012, 02:48 AM
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Ok , I'll go ahead and change the name to SUE - SUPER UGLY EASY !
If I can fly it, I'll marry it.
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Old Nov 23, 2012, 10:11 AM
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I'm sorry Al I hope you know what I said was tongue in cheek. I actually like your plane with the dihedral and rudder I'm sure its a pussycat to fly. Any plane is fun if you build it yourself and it actually works its a blast. I guess I like building planes so I'm sure I'll get around to yours also I just don't have enough esc parts to go around yet.

I totaled my kesl yesterday after flying four batteries through it I started doing barrel rolls and corkscrewed it into a cartwheel crash into a big rock. I'll build a new airframe today and hopefully have it ready for tomorrow. Didn't even damage the prop.
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Old Nov 23, 2012, 01:36 PM
Hot glue held together by foam
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[QUOTE=Low and Slow;23341879]I'm sorry Al I hope you know what I said was tongue in cheek.

No worries ! Someone even said it looks like the head of Phineas ( and Ferb ) - might be fun to go with that and put on eyes , mouth , etc .

I recently made a 1/2 size SUE that's a blast to fly ! It'll do loops and rolls all day long .

1/2 size SUPER EASY RC paper airplane (1 min 48 sec)


Al
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Old Nov 23, 2012, 03:04 PM
Hot glue held together by foam
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Originally Posted by Dan_D View Post
My NEKKID SE is finished in time for the drive up to Dayton tomorrow.

AUW - 305 grams without battery. Close, but heavier. I used an extra servo, so that explains 9 grams of difference.. so mine is 6 grams heavier. I used a little velcro here and there, bamboo pushrods instead of carbon fiber. ALSO, my only Y harness is too long, so I had to fold it back and forth and for appearance sake I stuffed it in a bit of un-shrunk heat shrink. Yeah, that's probably 3 or 4 grams right there. I suspect I might have used a bit more hot melt here and there.

Anyway, it's a LOT lighter than the 400+ grams that Lawn Dart weighed.

So, tomorrow... repaired Hawk Sky, Lawn Dart, and NEKKID SE are heading to Dayton... Weather is supposed to be good. Maybe we'll visit the AF Museum on Saturday and go oogle the XB-71, and dream and plan.

ALSO... rumor has it that there are SEVERAL local hobby shops up there AMAZULATING !!! ASTOUNDIFYING !!! I can buy a shorter Y harness. I can get a stronger motor for Lawn Dart. I can spend money !!! I have a credit card, I can spend money we don't have yet !!! Resistance is futile, the contents of your wallet will be assimilated.

Good luck Dan ! Don't forget to start with a little up elevator ( 1/4" ) trimmed in . Keeps the nose slightly up , kind of like keeping the tips of water skiis slightly up .
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Old Nov 23, 2012, 10:06 PM
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Good luck Dan ! Don't forget to start with a little up elevator ( 1/4" ) trimmed in . Keeps the nose slightly up , kind of like keeping the tips of water skiis slightly up .
Dayton Nano Fly In... Day 1.

Wind 20 MPH, with gusts to 30 MPH. Flags standing straight out from flagpole with only 25% of top curled over. The opinion of the experts - HA HA !

Went to a hobby shop instead. Bought carbon fiber rods for control rods, and 1/4" carbon fiber for wing strengtheners, and a 2 oz tube of CA (I had been using 0.7 g tubes from Dollar Store)... Now I can REALLY stick myself together.

Bought Balsa to make second wing for Gentle Lady, this one with Ailerons. Also bought a little this, a little that... Credit card bill is between "quick explanation" and "how about a back rub for you, honey?".

Back at home of one of the experienced fliers, who looked at the SUE and said "You need to put in up elevator...". We then proceeded to rebuild the whole system of linkages, etc. By the way, he likes it. He insisted that I show him where to find the plans. He's going to make one, too.

We also repaired the Hawk Sky, which was then christened the "Sir Andrew Barton". He was either a patriot or a pirate depending if you ask the Scots or the English. His words were immortalized in song and verse:

"I am sore wounded but am not slain.
I'll lay me down and bleed awhile,
and then I'll rise and fight again."


That's my Hawk Sky... sore wounded but not slain... she'll rise again..

However, predicted wind tomorrow... 15 mph. So, maybe she don't rise again tommorow.

Well, Ad Astra... when the wind don't blow. If it does blow, there are MORE hobby shops and the Air Force Museum. The only problem... one more hobby shop on the credit carb bill and we go from "back rub" to dangerous territory... Oh look, there is CASH in my wallet !

Stay tuned.
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Old Nov 24, 2012, 04:48 PM
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Dayton Nano Fly In, Day 2

I looked out the window this morning... not too bad. The branches are swinging a little, but it's clear, bright and snowing ???

Okay, it's not a LOT of snow, you have to look carefully to see the snow, but there it is.

The experienced guys decide that it might get calmer later, and warmer... so, off to hobby shop #2. Fortunately, this was not a huge mistake... I had enough cash to hide the bill

Lunch, discussion of depron, motors, servos, and "yew call this wind? wail eye remember back in 190<whatever> when we flew our airplanes in a hurricane, uphill, both ways."

After that we went to the parking lot and held a small confab... estimates of wind speed of 10 to 15 MPH... consensus - Air Force Museum !!!

Okay, it's 4:40 PM... sun goes down in 45 minutes or so. Wind is still 10 MPH with sharp gusts... opinion is divided - some say "lets go find a warm spot and have a beer and a pizza", others are saying "lets go watch the newbie crack up his new plane!". Somehow that description doesn't fill me with confidence.

Ah... they seem to be reaching a consensus... pizza and beer... uphill, both ways. Well, I haven't done any flying, but I've been hanging around with a nice group of guys and learning stuff... Only problem, I figure I'm going to have to spend some time sorting between fact and "stretchers"...
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Old Nov 24, 2012, 06:48 PM
Hot glue held together by foam
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Sorry you didn't get a chance to fly yet , Dan ! The weather gets me here a lot , too ! Is one of the pros gonna be able to at least trim your planes for you before you head back home ?
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