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Old Aug 27, 2010, 08:23 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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Quote:
Originally Posted by grem62483 View Post
Mr Jack,

Thanks for all your help. I really appreciate it. I never really understood the "C" rating before but now it makes alot more sense. I just saved that info to my word program on my computer so I can go back and look at the formula just in case I forget it. (which is very likely.) I think your right about flight time also because I had this little motor on Ewo's GotAmit bipe that I built with a 1000 mah battery and I could fly for a good while. I'm not looking to fly full throttle anyway. Just slow and steady. Ill let you know how it goes. Dad is gonna get a kick outta this thing. Hes been wanting to see this plane fly for a while. My 7yr old son has already claimed that its his plane so we might have to build another one. Or two! Thanks again, Bradley.
You're more than welcome. One final check for keeping your batteries alive is that when you check them after a flight then should not be down around 3.0V per cell or even 3.3V per cell (9-10V for a 3S pack). They should be at about 3.7-3.8V per cell (11.1-11.4V for a 3S pack) after you have finished flying and they have rested for a while.

Some will argue that you are not getting full use of your cells when you do that but the reality is that you are only "giving up" about 15 to 30 seconds or so of flying time compared to taking them down to 3.3V. And the time you are giving up is the time where the battery temp starts to rise, the battery gets too hot, and the battery is permanently damaged. You are right on the threshold of a "puffed cell" where the pack becomes soft and rounded because of the pressure buildup for the heat and gases inside the pack. One flight like that and a battery can be history.

You and the BigOleDude have fun!

Jack
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Old Oct 08, 2010, 02:25 PM
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Ilford,Essex, UK
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72 incher

Hi Jack

Just a quick post to let you know how the XXXL project is going.

A bit slow due to other comittments ect. Had some mishaps bringing home the correx it got hit buy a loose strap from a hay lorry going the other way on a narrow road then the wind folded it up

Anyway we used polystyrene on the top step 25 mmm at centre to 14 at the tips & inserted some fglass kite rods and two old firework rocket sticks let into the foam. Holding it in the middle there is no droop I was a bit surprised how "stiff" the poly and sticks made the correx. weight so far = 580 gram.

I did intend to WBPU and "stocking net" and tape the poly but I may just WBPU it and tape

Still deciding on a motor and cockpit design.

Regards Jeff
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Old Oct 08, 2010, 03:50 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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Looking good there Jeff!

You plan sounds good. I was apprehensive about the flexibility as I built the first one but it all felt better as the build progressed.

And full sheets of coro can be a challenge to transport, the stuff can get a minds of it's own without any external help.

I can see the "hay lorry" in my minds eye because I visited Scarborough, Yorkshire for a couple of weeks in the mid 1970's. I learned more than a little spoken English while I was there. When we were going somewhere in a car we occasionally encountered a lorry.

And I learned that we were two nations separated by a common language. But I had a wonderful time there. I liked the country much better than London.

Jack
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Old Oct 15, 2010, 10:02 AM
Me a long time ago
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London N.E. UK
Joined Jan 2007
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The progress so far on our six foot Spafffnutz wing.
The step was built from styrofoan. It was covered with the legs of a pair of womans tights and stuck down with a coat of water based (light oak) varnish. Thinned down with water.
This is to protect the styrofoan from disintergrating on a bad landing. (We hope)
A short video of a test type glide with just some lead taped to the nose.

http://exposureroom.com/98e4e77da594...cf5fb96ca758c/
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Old Oct 15, 2010, 02:16 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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Looking good there guys!

That will fly! I can tell because I've been there before. When I was there for test glides and had a motor too, a few hundred RPM of power and and that would have turned into a maiden flight.

Looking forward to the rest of the story, best of luck with it!

Jack
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Old Dec 19, 2010, 05:40 AM
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London N.E. UK
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I just thought that I had better report on the results of my SpaFFFnutz or what ever you want to call it.
The 6ft version was not working out so well. So I had to strip it down and vurtualy start again.
I cut off the tips and made it 4ft. (48") this worked out better.
So the KF wing was Corroplast with styrofoam as the step. This was covered with a thinner type 'Duck' tape.
Some thin ply strips top and bottom.
Here are links to videos of the result. Yes it flys OK.
The Big Wing Maiden (2 min 42 sec)

The made from scrap 48" flying wing. (3 min 51 sec)
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Old Dec 19, 2010, 08:13 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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Congrats Flypopa!

I think that your were bedeviled by a tail heavy condition on that first video. That pitching up and down and wanting to climb or dive but not fly level is very characteristic of that. You may be lucky that you got it back relatively undamaged. There is a saying, "Nose heavy planes fly poorly, tail heavy planes fly once" and your experience proved that.

The second flight looked good, a classic example of the majestic and a graceful flight of a KFm flying wing!

Congrats again!

Jack
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Old Dec 19, 2010, 08:45 AM
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Thanks Jack for your reply. Jeff is going ahead with the 6 footer.
This should be interesting to see the results.
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Old Dec 30, 2010, 01:33 PM
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Ilford,Essex, UK
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Hi Jack

Hope you had a nice Christmas I have finaly got the wing in the air . she ran away with herself and put on a few ounces over the holiday and ended up @ 48 without the battery.

After the runs with Malcomes cut down version I decide the motor was not up to the job so I slapped in a bigger lump reserved for my 48" mustang.

I have yet to fit the FPV gear not sure to put in a nose cam or a rotating turret on the top and I am debating if it is all to heavy but hey it flys

I need to put some more throw on the elevon which will make it more interesting

Regards and a happy new year Jeff


BIG WING 72" MAIDEN (5 min 19 sec)
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Old Dec 30, 2010, 05:45 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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Looking good there, Jeff!

I have had the material for a big wing build since last summer and have just not gotten around to it. More a case of lazy then busy...

Is the FPV stuff going to be housed in the tube or more riding on top? And did have to use the tube much to get stuff forward to make the CG right?

Congrats again! And thanks for the kind words.

Jack
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Old Dec 31, 2010, 05:09 AM
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Hi Jack

The fpv is going to be in the tube as a nose cam ( May still go for a rotating turett through the top????) with the VTX on one wing tip batt on the other, to get the cog OK I had to put the back of the battery just infront of the leading edge 2200 mh so the "nose" was badly needed. there is a 2 inch soft bumper inside the tube on the nose plus a inch or so wiggle room so it could have come back a little.

You probably noticed the "tube" is made from soda bottles (3) and sprayed black on the inside

The other changes were half inch off the elevons ( I dont think they needed to be scaled up with the rest of the wing ) and I made the motor cut out a little deeper to help with getting the weight forward

As I said in the video I would not like to get hit in the head by it!!!!!

Regards Jeff
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Old Mar 21, 2011, 10:32 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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I was recently talking to bsfixit (he's building a SpaFFFnutz now) about the power requirements for this plane. The attached image gives a good idea as to typical power requirements in flight.

That graph represents about four and a half minutes of flight, most of it at mid throttle and then some full throttle flying at the end. The green line is the RPM, the purple (maroon?) is the power in Watts. So that long flatter section is a period of time where I was flying at a constant throttle setting and just drilling holes in the sky, maybe flying big lazy loops, making orbits around the field using ailerons only and just flying around. That was all done at about 5,000 RPM and using about 45-60 Watts of power. At that throttle setting the SpaFFFnutz will do almost any maneuver she can do at what I consider her cruising speed. If I go vertical at that throttle setting she will eventually lose speed and not be able to maintain a climb.

It is not seen there, but if I throttle back even further and reduce control inputs to just keep the plane comfortably above a stall speed, the RPM would be down around 3,000 to 3,500 or so. And at about 1,500-1,800 RPM she is still flying comfortably like on a long slowly descending final approach.

At the end of the graph I throttled up, probably to full or nearly full throttle and you can see the Watts are pushing 200 and the RPM up around 7,000. At that point I am getting uncomfortable with the plane's speed and if I go into a steep dive I know that I can encounter problems like fluttering of the wing or control surfaces. So I don't use full throttle much at all and you can see where I throttle back some.

So how much power does the SpaFFFnutz need to fly? I'd say that my build, at about 28 oz. and with up to 200 Watts available, would fly nicely with 100 Watt power system. But if you want to fly in higher winds having more power available really adds to the plane's ability to handle more wind.

I'm flying now with a 10 x 4.5 prop, I could get more speed out it with a 10 x 7 and that motor could handle the load. I'm flying now at pitch speeds of 15 to 30 MPH, my true airspeed at probably about 15-25% less than that. And the SpaFFFnutz is very comfortable and stable at those speeds.

If SpaFFFnutz has one unresolved flaw it would have to be that of the fluttering of the control surfaces and the back of the wing at high speeds. That is not an issue for me because I am already flying faster than I want to when that happens. And it is the kind of thing that could destroy servos, over stress linkages, and do horrible things like that.

Jack
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Old Apr 20, 2011, 02:40 PM
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Sarasota, FL
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I recently got my SpaFFFnutz in the air and I just love it. It's very strong for someone who is still learning like me. I am already set my mind on putting a camera on the plane. After my back gets a little better. I will post a cell phone video when I can..
Thanks Jack! I really like this wing!
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Old Apr 20, 2011, 02:45 PM
Jack
USA, ME, Ellsworth
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Congratulations on the successful maiden!

And get well soon too!

Jack
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Old Apr 20, 2011, 09:12 PM
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Here is the 1 minute or so video, turn your sound down, the wind noise overpowers the sound of the electric motor. This flight used a GWS HD1080 due to the 10-15 MPH winds on this hill built on top of an old landfill. The only hill for perhaps a hundred miles, not including the newly built Lifeflight landing pad 5-6 miles away. At the end I didn't crash but rather it stalled then dropped into the tall grass.
spaFFFnutz.mp4 (1 min 18 sec)
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