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Old 08-27-2012, 10:53 PM   #1
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Default It ain't pretty, but...

I'm reluctant to show this before it actually flies, but what the heck . After the abject failure of my first foamie scratch build (the 24" J3 Cub) I decided to go with something which I hope is much more likely to succeed (certainly less likely to break props):









It's got a 36" wingspan and weighs in at 9.5 oz (without a battery pack). The battery will go out on that "snout" on a long strip of velcro so it can be moved around to adjust the CG. I've got some bigger batteries on the way - all I've got now are little 230 mA jobs that I use in the Cox Sky Cruiser...

Next time I'll think out the routing of rudder and elevator control rods in a more "elegant" manner

With any luck tomorrow I'll find a nice high grass meadow and do some glide tests with weights stuck in the battery position to find the preliminary CG.

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Old 08-27-2012, 11:01 PM   #2
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Originally Posted by dgjessing View Post
I'm reluctant to show this before it actually flies, but what the heck . After the abject failure of my first foamie scratch build (the 24" J3 Cub) I decided to go with something which I hope is much more likely to succeed (certainly less likely to break props):









It's got a 36" wingspan and weighs in at 9.5 oz (without a battery pack). The battery will go out on that "snout" on a long strip of velcro so it can be moved around to adjust the CG. I've got some bigger batteries on the way - all I've got now are little 230 mA jobs that I use in the Cox Sky Cruiser...

Next time I'll think out the routing of rudder and elevator control rods in a more "elegant" manner

With any luck tomorrow I'll find a nice high grass meadow and do some glide tests with weights stuck in the battery position to find the preliminary CG.

Quite interesting!

Let us know how it works out. My son might be inclined to build this thing if it works OK. I'd also need to know the motor size and battery pack size.

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Old 08-28-2012, 01:59 AM   #3
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I'm in definitely has me curious. Very interesting design

Happy flying may your crashes be limited and if they are not limited let them be cool.
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Old 08-28-2012, 02:24 AM   #4
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Looks cool to me!

All of my landings are three point landings if you count the spinner, too
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Old 08-28-2012, 05:06 AM   #5
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Looks like a great FPV/aerial photography platform.

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Old 08-28-2012, 02:46 PM   #6
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I congratulate you for your ingenuity, we need more like you. Whether it works well or not, let us know the outcome and, if you make changes, what are they. Please keep us informed.
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Old 08-29-2012, 12:26 AM   #7
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Thanks you guys!

I don't want to get ahead of myself, but I *am* hoping it will be a good video platform. Need to get it flying first though

Assuming it does fly, this will be my first time flying an RC model with ailerons. I've been at the controls of *real* planes a few times (which of course had ailerons) but never a model, so I hope it's a decent trainer as well!

Right now it has a "Firepower 250 Sport Outrunner Brushless Electric Motor" and a "HURC 10 Amp Brushless Motor ESC", both from Heads Up RC. Like I said, I don't have suitable batteries yet but static testing with a 7.4v 300mAh it seems to me like it's got plenty of thrust. I can get about 5 minutes of mostly 1/2 throttle, some full, and wiggling the servos all the time out of that battery. I've got some 7.4v 1000mAh batteries on the way - is it correct to assume that I'll get about 15 minutes out of those?

Didn't get a chance to glide test today... maybe tomorrow

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Old 08-29-2012, 04:39 PM   #8
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Glide tests went well this morning - nice straight path, no up & down, went quite a ways . This with a dummy battery same weight as the ones I've got on order. Can't wait for the real batteries to arrive!

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Old 08-29-2012, 08:24 PM   #9
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I like it, very creative design. That's what the hobby is supposed to be about anyway.

The TRUTH is not always what it seems.
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Old 08-29-2012, 09:07 PM   #10
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Great design, but how are you going to land it? My fear is that it will immediately tip over to the side and cartwheel. Are you planning on adding landing gear to it?

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Old 08-29-2012, 09:18 PM   #11
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I think you will find the ailerons very insensitive due to the large amount of dihedral and their inboard location. Really, with that much dihedral, the rudder/roll coupling will be more than adequate, you could dump the ailerons. Still an interesting project, keep us informed.
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Old 08-29-2012, 10:29 PM   #12
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Originally Posted by NJSwede View Post
Great design, but how are you going to land it?
I dunno - I figure it will do as well as any other with no landing gear... But now that you mention it, might be a problem . I was thinking about putting a strip of plastic or something on the "skid" portion so it will slide better on the grass (better than just the raw foam core edges). The concern being that it would catch on the grass and nose over... We'll see, I guess.

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Old 08-30-2012, 03:30 AM   #13
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Just my .02 cents but I think landing will be fine. It seems that it will glide down fairly well. Dgjessing when you performed your glide test how well did it belly land? I think if you dead stick glide and land I think you will be fine. However NJS may be right if you come in to fast. Also I think if you land in tall grass area will help as well. Good luck looking forward to your maiden report.

Happy flying may your crashes be limited and if they are not limited let them be cool.
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Old 08-30-2012, 04:05 AM   #14
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Originally Posted by Fishbonez View Post
Just my .02 cents but I think landing will be fine.
Well, there's only one way to find out... Go fly it!

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Old 08-31-2012, 11:14 PM   #15
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Fishbonez, the glide tests were in knee high grass, so the landings really didn't tell me anything about whether or not it will cartwheel on shorter stuff.

I've got batteries! At the giant scale event at the USAF museum today I bought a couple 800 mAh units, knowing that doing so would make it so my Hobby King order would be here when I got home. It worked, so now I've got those two plus four 1000 mAh packs. The 800's weigh 50 g, the 1000's weigh 62 g, and my test weight weighed 50 g and was placed about in the middle of the "snout". So I'm thinking I should be able make things work with all this stuff.

Weather report looks ~OK tomorrow - wind less than 5 mph but a 60% chance of rain. If The Wife doesn't need me for a couple hours and there is no soccer game going on at the park we may be able to try it out

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Old 09-06-2012, 12:54 AM   #16
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It lives!

http://www.youtube.com/watch?v=S6uQS...ature=youtu.be

Could definitely use a bit more power, but it flies well .

Whoever predicted that the ailerons wouldn't have much "authority" was right - aileron only turns are pretty leisurely. It's under powered - gaining altitude is a long process. But all in all I'm pleased, and encouraged to do more

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Old 09-06-2012, 02:06 AM   #17
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Congrats!

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Old 09-06-2012, 02:32 AM   #18
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That's what I call a flawless success! Congrats!

You should post the plans here. It looks like a great easy, lazy flyer. I think a lot of people would enjoy a model like that!

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Old 09-06-2012, 03:40 AM   #19
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Originally Posted by NJSwede View Post
That's what I call a flawless success! Congrats!

You should post the plans here. It looks like a great easy, lazy flyer. I think a lot of people would enjoy a model like that!
Thanks!

I'll draw up the plans as time allows (the originals are in pencil ).

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Old 09-06-2012, 03:49 AM   #20
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Yup you did a great job with it kinda reminds me of my super solution that I bought as a foam kit. Get a key chain camera on this plane bet you can get some good videos with it.
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Old 09-06-2012, 06:00 AM   #21
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Congrats. I think it is going to make a great platform for FPV. May even be a great beginner FPV plane. Congrats again its very cool

Happy flying may your crashes be limited and if they are not limited let them be cool.
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Old 09-06-2012, 11:43 AM   #22
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Well done it flies and from the video pretty nicely too!

Building and flying a plane of your own design is quite an achievement but rather than immediately think about building something else why not see if you can make it fly better? If you can it will teach you a lot about what works well and what doesn't.

You could of course just add a bigger motor but there are several things you could do to make better use of the power you have.

1. Personally I am not a great fan of KF air foils but I am sure some work thinning down the trailing edges would pay. It wont fly that much better but it will use less power doing it. The tail surfaces can be treated the same, drag created of a square leading or trailing edge is power wasted.
2. The extreme dihedral tips won't add that much lift but have the same drag per unit length as the wing itself. So take them off! (or re-fix them with no dihedral)
3. The motor mount is a quite a big plate and its doing a pretty job as an air brake. Reduce it to the minimum required by the motor mount.

Of course your design is never going to be a 3D hot ship but get the simple aerodynamic improvements right and the results can be quite significant. Any weight you can save also has equal benefit.
Better performance, longer duration and all with the same motor and battery.

If you can get it to fly 'better' the satisfaction gained is immense and you will also have some valuable knowledge to take on to your next design.
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Old 09-20-2012, 01:38 AM   #23
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Took it out for the second time today. This time I put the heavier of the two types of batteries back further on the nose, which helped a lot with attaining decent altitude. The thing is a bit heavy and/or underpowered - gliding with the motor off it comes down pretty quick. It takes perhaps 75% throttle to maintain a steady altitude. I may make another one using all of quorneng's excellent suggestions.

I suppose it didn't help to have two key chain cameras on board most of the time . It was also pretty windy - 10 to 20 mph, I would guess. I'm not very good at judging that, but some of the guys at the field with much bigger gas powered planes were reluctant to fly 'cause of the wind. The wind sock was straight out some of the time...

But we've got video!

http://youtu.be/51dwqyG81Rc

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Old 09-20-2012, 03:43 AM   #24
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Looks sweet.

I'm a big fan of way over powering setups. You can always throttle back, and most electrics use quite a bit less draw at lower rpm's. Above half throttle on my motors, the amps just about double.
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Old 10-18-2012, 11:28 PM   #25
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Starting on version 2:



I've dropped the "pod" down 1" to allow an 8" prop, and am using a HobbyKing 1550kv "Donkey" motor (quite a bit bigger than the first one). Since it's essentially just a video platform I want to be able to get some altitude quickly . I'm going to increase the wingspan a bit, from 36" to 42", and have just a tiny bit of dihedral (no more polyhedral stuff).

More as things progress!

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