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Scratch Built FUNJET contest #2

Old 06-09-2011, 05:33 PM
  #26  
AirmanAirhead
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Chellie,

OK, I got a question for you. As you might recall, my first build of this plane turned out to be a "FAT FunJet" due to an error I made in the fuse. I flew that version a lot and really enjoyed it. Hand launching was not a problem ever.

But getting a bit crazy I started flying it in more and more wind, it was a blast, and then.... I crashed it. OK, it's a foamy and the wings were fine, so I built a new fuse to your specs. Looked much better!

Problem: I have not changed the motor, the prop, or the battery set up. But now, I have a terrible time hand launching it. It climbs just a bit, and then turns straight to the ground to the right, every single time. I'm getting good at rebuilding the nose on this plane!

Question: I don't think this is a torque problem because it goes to the right not left. But I think it could be a CG problem. Does this sound like perhaps I need to move the battery more forward to compensate for the smaller, lighter fuse? My motor is square on the mount, with just a slight bit of "up thrust" I did this because the very first time I tried to launch it, it flew like a bullet to the ground. Perhaps I have really gummed things up related to the thrust angle and the CG

I've messed with a lot of planes over the last couple of years, but this is the first "FunJet" and it seems that it is even more crucial to get the CG/Thrust right. I'm thinking that on a hand launch it climbs but then loses lift and then stalls and whamo hits the ground. Of course this all happens to fast that it's hard for me to tell really what is going on. The first one flew so nice this is starting to get to me!!

Got any suggestions???

As always, thanks a lot!!

Jeff
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Old 06-09-2011, 11:16 PM
  #27  
CHELLIE
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Originally Posted by AirmanAirhead View Post
Chellie,

OK, I got a question for you. As you might recall, my first build of this plane turned out to be a "FAT FunJet" due to an error I made in the fuse. I flew that version a lot and really enjoyed it. Hand launching was not a problem ever.

But getting a bit crazy I started flying it in more and more wind, it was a blast, and then.... I crashed it. OK, it's a foamy and the wings were fine, so I built a new fuse to your specs. Looked much better!

Problem: I have not changed the motor, the prop, or the battery set up. But now, I have a terrible time hand launching it. It climbs just a bit, and then turns straight to the ground to the right, every single time. I'm getting good at rebuilding the nose on this plane!

Question: I don't think this is a torque problem because it goes to the right not left. But I think it could be a CG problem. Does this sound like perhaps I need to move the battery more forward to compensate for the smaller, lighter fuse? My motor is square on the mount, with just a slight bit of "up thrust" I did this because the very first time I tried to launch it, it flew like a bullet to the ground. Perhaps I have really gummed things up related to the thrust angle and the CG

I've messed with a lot of planes over the last couple of years, but this is the first "FunJet" and it seems that it is even more crucial to get the CG/Thrust right. I'm thinking that on a hand launch it climbs but then loses lift and then stalls and whamo hits the ground. Of course this all happens to fast that it's hard for me to tell really what is going on. The first one flew so nice this is starting to get to me!!

Got any suggestions???

As always, thanks a lot!!

Jeff
Hi Jeff it sounds like to me that the Fat Body Funjet was making up for a lack of thrust, this funjet needs at least 20 oz of thrust to fly right, and you could be tail heavy too, add some weight to the nose and try it again. give the plane a good hard toss at a 30 degree angle up, Hope that helps, Chellie


CG Location, on mine the CG is 17" back from the nose, or 1" behind the front leading edge of the wing where it starts to tappers/turn at going towards the fuselage.

check your prop to make sure that the numbers are pointing towards the front of the plane
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Old 06-09-2011, 11:20 PM
  #28  
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What motor, prop, esc and lipo are you using Jeff ?
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Old 06-10-2011, 01:42 AM
  #29  
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Chellie, I'm using the set up you recommened. The 2836-2350 motor with a 5x5 prop and a 4 cell . It has plenty of push, it was crazy fast with the "fat fuse" and I just had a blast with it. That's one reason I'm so flumaxed about this new issue that turned up. The only change is the right fuse, same length as you plans call for. I was very careful to keep everything the same. It even has the same wing.

That's why I think I need to move the battery a bit forward, I'm using the 17" / 1" back from LE that you suggested too. I even have a dowel set up I use in my shop to test the CG

Thanks,
Jeff
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Old 06-10-2011, 01:52 AM
  #30  
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Originally Posted by AirmanAirhead View Post
Chellie, I'm using the set up you recommened. The 2836-2350 motor with a 5x5 prop and a 4 cell . It has plenty of push, it was crazy fast with the "fat fuse" and I just had a blast with it. That's one reason I'm so flumaxed about this new issue that turned up. The only change is the right fuse, same length as you plans call for. I was very careful to keep everything the same. It even has the same wing.

That's why I think I need to move the battery a bit forward, I'm using the 17" / 1" back from LE that you suggested too. I even have a dowel set up I use in my shop to test the CG

Thanks,
Jeff
Hmmm Check the wing, it might have a twist in it, rolling down on the right side, maybe caused after the crash, I had a GWS Corsair do that to me too, it drove me crazy trying to find the problem, because the gull wing would hide the problem, only after setting the plane on a flat table and checking everything with rulers did i find the problem, might want to try that with your wing too, hope that helps, Chellie
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Old 06-10-2011, 01:56 AM
  #31  
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Thanks Chellie, Hmmmmm that has me curious now because indeed something had to change and I never thought of looking real close at the wing other than obvious cracks, etc. I'll check for a twist/warp as you have suggested.

Jeff
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Old 08-26-2011, 12:48 PM
  #32  
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Default Drawing of top and bottom view

In your drawing of the bottom view of the funjet, what is the distance in inches from the nose to the area labelled 2 3/4 inches? Thanx!
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Old 08-27-2011, 12:36 AM
  #33  
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Originally Posted by jasonpadre View Post
In your drawing of the bottom view of the funjet, what is the distance in inches from the nose to the area labelled 2 3/4 inches? Thanx!
Hi Jason Its the Same as the top, 7" and Welcome to Wattflyers, Take care and Have fun, Chellie
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Old 10-13-2012, 05:27 PM
  #34  
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Thumbs up Thank you!

I know this post isn't hot anymore, but I want to thank you for these plans! I just put this thing together with the electronics from my PZ T-28. I Used 6mm and 3mm depron. I sandwiched a fiberglass spar into the 6mm then bonded 3mm on both sides. The fins are 2 ply's of 6mm sanded down, and the body is 6mm with 6mm strips reinforcing the fuselage at all the joints.

I maiden'd it today, and it is so much different to fly than anything else! I'm probably going to put some expanding foam in some high stress areas and the nose. This thing needs the extra weight!

Again, thank you so much for an easy but fun build! (great way to save $21.78) lol
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Old 10-15-2012, 07:41 PM
  #35  
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I know it's not a scratch built version, but the HobbyKing Radjet 420 is a perfect Funjet miniature in every way, see pic. As a result I never did build one from the plan.
Sorry Chellie.
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Old 03-12-2013, 08:23 PM
  #36  
IAFoamie
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Hello Queen of RC
I'm interested in your Scratch Built FUNJET. Would there be a way to slow it down without stalling or messing the flight chartics up. Thicker airfoil? Maybe a bite larger like 40" wing?
I'm just flying a high wing so far but want and easy plane to build. Any help would be great.
IAFoamie
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Old 03-24-2013, 05:15 AM
  #37  
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Hello still trying to get and answer. Maybe another great simple plane. Have flown my high wing about 20 times I guess.
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Old 03-24-2013, 10:50 PM
  #38  
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Chellie hasn't been around nearly as much lately.

Very generally speaking, going slowly is about wing loading. If you make your current plane weigh, say, 75% as much, it'll fly more slowly.

Look at Strykers, for example, which are very similar to funjets. People build them to go fast fast fast. But - people also build them to go very slowly. The way you do that is by stripping off every bit of extra weight and equipping them with smaller batteries, motors, ESCs and servos.

A fast Stryker might weigh 30 ounces. A slow Stryker might weigh 10-12 ounces.
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Old 03-24-2013, 11:55 PM
  #39  
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Originally Posted by IAFoamie View Post
Hello still trying to get and answer. Maybe another great simple plane. Have flown my high wing about 20 times I guess.
Hi I Just saw your question this Funjet slows down real nice, it has some drag to it, no need to do anything to it but fly it and have fun Take care, Chellie
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Old 03-25-2013, 05:16 AM
  #40  
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But the lighter you make it, the slower it'll go.
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Old 03-25-2013, 07:00 AM
  #41  
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Here is a video of the Funjets maiden, I am doing the video and one of our club members is doing the flight, as you can see it slows down very nice.

http://www.youtube.com/watch?feature...&v=WLLQM7cXseM
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Old 03-25-2013, 09:47 PM
  #42  
IAFoamie
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Hello
Thanks mclarkson and Chellie for the info. I'll try for a light plane.
I'll try and laminate DT foam for wing and have a CF2812 to use or a smaller Grayson Hobby motor forget number. Thanks again for all the help.
IAFoamie

PS I only have 9 gram servos.
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Old 03-25-2013, 10:07 PM
  #43  
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9 gram servos are perfect.
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