Mini Fun Jet build

[Hell2Go]

Mini Fun Jet by kpl72



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Rating: 4.25 16 ratings


Posted: February 15, 2015 | 1,816 views


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Overview

This project was a scale up of little foam gliders I got the kids at the drugstore. They are called Zrang and are just a really cool, well-flying little jet. I thought, what if I scaled it up 400%, used DT foam, and powered it with a Park 250? I just started cutting, folding and gluing, and along the way came up with some cool features.



Construction

Of course, I forgot to take pictures during construction, but it was so simple, I'm not sure they are needed. Here is a really rough sketch of the dimensions, I'll try to move into CAD and make them printable in a pdf. Measurements are in inches, and probably only works for folks with some experience with FT models. Click to make them readable.





Wing:

I started with the wing:



The wing is a basic flitetest style folder wing. Since it's swept, I cut two pieces, left and right. I taped and glued the bottom panels, scored the top panels and beveled the leading edge where it folds. There is a tapered "spar" consisting of a larger and small triangle so that it is 2 layers thick at the root, tapering to one layer at the end of the bottom panel. I then scored the top panel, folded and glued it back in flitetest fashion. I then cut and tapered the ailerons and installed servos. Servo leads were fed along the spar to the access hole in the center section. They are just long enough.

Fuselage & Tailfeathers


Next I built the fuselage which is just a basic rectangle tube to fit a standard FT motor mount. I folded the fuselage (B folds) and I glued and taped the mount on the back. Next I cut the horizontal stab, beveled the elevators (FT style glue-hinge) and then glued it on to the fuselage. Following that, I glued on the two vertical stabs at about 15 degrees from vertical. The motor was then screwed on and the servos slid and glued in place. I use one servo for each elevator so they can be tailerons. This is import so that I have roll control because the wing has flaperons and I wanted positive control with the flaps lowered.





Nose & Wing Hold Down


The final step was to build the nose. I wanted a slip on nose similiar to the FT Mini Guinea which I had build the week before. I liked the idea of the internal battery - good for cold weather - and the ability to have a sacrificial nose for the inevitable oops. I glued in a small battery platform like the MG, but then realized if I put the upper portion in, it would be too narrow for my battery. Hmmm.. This became a happy accident, because I then decided to have the nose just slip over the entire front of the fuse, which then solved my wing hold down decision. I was going to use rubber bands, but then realized if I tabbed the back of the wing to slide under the fuse/tail, the nose could slide over the front of the wing and hold it in place. COOL! It not only gave real shape to the design, but it kept the wing solidly in place. I used popsicle stick to sandwich the foam board with a zip tie to keep it strong. The nose section slides over top of the fuselage and the wing cutout holds the leading edge in place. Right now it is a friction fit, but if it loosens up, I'll use a skewer to hold it in place.



Nose section







Assembly Video:






Waterproof and Paint

Next step was to seal all the edges with hot glue/squeegee method, then the entire plane was polyurethaned to water proof it. Next I sprayed the color with Testor's acrylic.



I ran out of yellow and blue, so the underside of the horizontal stab is red. It should help with orientation anyway... I then applied clear 2" packing tape to the leading edge of the wing and the nose. The cockpit is black monokote trim.

Electronics:

I used a PowerUp 250 sport 2300kv for power with a 10A Hurc esc, 4 5G towerpro servos and an Orange RX from HobbyKing. Battery is a 800mah2S, although a 1000mah3S will fit, but I'll need to swap to an emax 1804 or similiar, I don't think the PowerUp will handle the 3S. Oh yeah, I had to make an extension on the power for the esc. I just did an JST extension on the battery side, but you could also extend the motor leads if you wanted to move the weight of the esc forward.

Radio Setup:

I wanted flaps to enable the plane to slow down for a steeper approach in my back yard. I have lots of airspace over a nice little valley, but the yard has trees and requires a pretty tight approach. I've used flaperons before, but I don't like the reduction in roll control as they approach full down. To help with this, I incorporated tailerons that I can turn off/on. I wanted traditional ailerons, because I've use just tailerons on the F22 and other prop in slot, but I was looking for more axial rolls. So, in typical flight this is a aileron/elevator yank and bank, but if I want blistering roll, I can use ailerons and tail together. For landing, tailerons automatically mix in when full flap is selected (3Pos Switch). See video for details:









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Comments


RacerX February 17, 2015

Nice build! The removable nose is ingenious as well as the control mixing.
Reply



sailorJohn February 17, 2015

Really like it. PLS add general measurements length of main fuse, wing span and cord. 5*
Reply


kpl72 February 17, 2015

I took most of the photos on the measuring board, squares are 1/2" Wingspan is 23" and fuse is about the same. If I get a chance, I'll sketch up some rough plans. Check back in a day or two... I'll get some flight videos once we get past these -30 windchills.....
Reply


Christopher14 February 17, 2015

Please get the plans up. I really would like to build one. (I have a small motor that will take this thing over 100mph). Call it stress testing.
Reply



kpl72 February 17, 2015

OK - I added the plans, sketched out on paper - really rough, it will take some intepretation of my chicken scratching. If someone can recommend an easy browser based CAD program, I'll clean them up. I use tinkerCAD for 3D, and recommendations for 2D CAD?
Reply


sailorJohn February 18, 2015

Thank you this give me a good stating point.
Reply



nicktutttle February 18, 2015

You might give autocad360 a try. It's still in beta, but might get you going!

https://www.autocad360.com/
Reply



Hell2Go February 26, 2015

Sketchup is pretty easy to use if you have CAD experience, plus there is a FT article on it with tutorials and a link to download it for free. This is what I love about this community. If you make up a printable plan I'd build it in a heartbeat, looks fun!
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Hell2Go February 27, 2015

KLP72 - I used your drawing and drew the plans in Sketchup to make a printable version. I'm still tweeking it a little and want to fold up a wing to make sure its good, then I'll post it somewhere for everyone to use. You should start a thread in the forums on this build as I think there will be a lot of interest in this plane.
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- See more at: http://flitetest.com/articles/mini-fun-jet#sthash.Nmzp2tco.dpuf

 

[Hell2Go]

I tried to copy and paste the article to the forum but it didn't work right so you'll have to refer to the article for the pictures and videos that go with this build. Anyone who knows how to do it right, feel free to fix the thread for me. thanks

 

[Hell2Go]

I drew up most of the parts to build this plane in SketchUp, its one page so far in 20 x 30 inch format. I haven't figured out how to convert it to a pdf yet so if you want to print it out, just download SketchUp for free and download this file https://docs.google.com/file/d/0B6O-NULkxGtVRzRFbW02RlhDSzg/edit and you should be good. when I get it into PDF format, I'll post that too.

SketchUp Maker free download: http://www.sketchup.com/products/sketchup-make

funjet page 1: https://docs.google.com/file/d/0B6O-NULkxGtVRzRFbW02RlhDSzg/edit
funjet page 2: https://docs.google.com/file/d/0B6O-NULkxGtVS3MxNlk2MGRPVG8/edit

 

[JohnRambozo]

I tried to copy and paste the article to the forum but it didn't work right so you'll have to refer to the article for the pictures and videos that go with this build. Anyone who knows how to do it right, feel free to fix the thread for me. thanks

This Article was merely recreated as a forum post. I made no contributions to the actual content.

Mini Fun Jet by kpl72

Overview

This project was a scale up of little foam gliders I got the kids at the drugstore. They are called Zrang and are just a really cool, well-flying little jet. I thought, what if I scaled it up 400%, used DT foam, and powered it with a Park 250? I just started cutting, folding and gluing, and along the way came up with some cool features.

​

Construction

Of course, I forgot to take pictures during construction, but it was so simple, I'm not sure they are needed. Here is a really rough sketch of the dimensions, I'll try to move into CAD and make them printable in a pdf. Measurements are in inches, and probably only works for folks with some experience with FT models. Click to make them readable.

​

Wing:

I started with the wing:

​

The wing is a basic flitetest style folder wing. Since it's swept, I cut two pieces, left and right. I taped and glued the bottom panels, scored the top panels and beveled the leading edge where it folds. There is a tapered "spar" consisting of a larger and small triangle so that it is 2 layers thick at the root, tapering to one layer at the end of the bottom panel. I then scored the top panel, folded and glued it back in flitetest fashion. I then cut and tapered the ailerons and installed servos. Servo leads were fed along the spar to the access hole in the center section. They are just long enough.

Fuselage & Tailfeathers

Next I built the fuselage which is just a basic rectangle tube to fit a standard FT motor mount. I folded the fuselage (B folds) and I glued and taped the mount on the back. Next I cut the horizontal stab, beveled the elevators (FT style glue-hinge) and then glued it on to the fuselage. Following that, I glued on the two vertical stabs at about 15 degrees from vertical. The motor was then screwed on and the servos slid and glued in place. I use one servo for each elevator so they can be tailerons. This is import so that I have roll control because the wing has flaperons and I wanted positive control with the flaps lowered.

​

Nose & Wing Hold Down

The final step was to build the nose. I wanted a slip on nose similiar to the FT Mini Guinea which I had build the week before. I liked the idea of the internal battery - good for cold weather - and the ability to have a sacrificial nose for the inevitable oops. I glued in a small battery platform like the MG, but then realized if I put the upper portion in, it would be too narrow for my battery. Hmmm.. This became a happy accident, because I then decided to have the nose just slip over the entire front of the fuse, which then solved my wing hold down decision. I was going to use rubber bands, but then realized if I tabbed the back of the wing to slide under the fuse/tail, the nose could slide over the front of the wing and hold it in place. COOL! It not only gave real shape to the design, but it kept the wing solidly in place. I used popsicle stick to sandwhich the foam board with a zip tie to keep it strong. The nose section slides over top of the fuselage and the wing cutout holds the leading edge in place. Right now it is a friction fit, but if it loosens up, I'll use a skewer to hold it in place.

​

Assembly Video:

Waterproof and Paint
Next step was to seal all the edges with hot glue/squeegee method, then the entire plane was polyurethaned to water proof it. Next I sprayed the color with Testor's acrylic.

​

I ran out of yellow and blue, so the underside of the horizontal stab is red. It should help with orientation anyway... I then applied clear 2" packing tape to the leading edge of the wing and the nose. The cockpit is black monokote trim.

Electronics:

I used a PowerUp 250 sport 2300kv for power with a 10A Hurc esc, 4 5G towerpro servos and an Orange RX from HobbyKing. Battery is a 800mah2S, although a 1000mah3S will fit, but I'll need to swap to an emax 1804 or similiar, I don't think the PowerUp will handle the 3S. Oh yeah, I had to make an extension on the power for the esc. I just did an JST extension on the battery side, but you could also extend the motor leads if you wanted to move the weight of the esc forward.

Radio Setup:

I wanted flaps to enable the plane to slow down for a steeper approach in my back yard. I have lots of airspace over a nice little valley, but the yard has trees and requires a pretty tight approach. I've used flaperons before, but I don't like the reduction in roll control as they approach full down. To help with this, I incorporated tailerons that I can turn off/on. I wanted traditional ailerons, because I've use just tailerons on the F22 and other prop in slot, but I was looking for more axial rolls. So, in typical flight this is a aileron/elevator yank and bank, but if I want blistering roll, I can use ailerons and tail together. For landing, tailerons automatically mix in when full flap is selected (3Pos Switch). See video for details:

This Article was merely recreated as a forum post. I made no contributions to the actual content.

 

[Hell2Go]

Thanks John, I was hoping to get the whole article here with the videos included, how do you do that for future reference?

 

[JohnRambozo]

Thanks John, I was hoping to get the whole article here with the videos included, how do you do that for future reference?

I reassembled the entire article manually by copying the text up to each image, then clicking the image and adding it as if I were posting it myself. I used the Insert Image button in the toolbar, chose "From URL", then unchecked "Retrieve remote file and reference locally" because its already hosted on flite test so there's no need to copy it again.

For the videos, I'd click the YouTube icon in the bottom right of the video to view it on youtube, then copy the link out of the address bar then use the Insert Video button in the toolbar and paste the link there.

Its a little tedious but really only took about 5 minutes altogether.

I may be a little faster since this is very much like what I do as part of my daily job.

 

[Hell2Go]

Thanks again, you make it sound easier than it is... I started to build the funjet and am taking lots of picture to post for build instructions as soon as I find time to do it.

 

[BanditJacksRC]

This is a pretty cool design man, good job.
I especially like the thought put into the slip-on nose.
This would make a cool little FPV rocket!

 

[Christopher14]

My FT Scout just died. I imagine that the electronics will go into this.

 

[Hell2Go]

This is a pretty cool design man, good job.
I especially like the thought put into the slip-on nose.
This would make a cool little FPV rocket!

You might wanna scale it up to about 175-200% for an FPV ship as its pretty small, that would slow down the responsiveness that comes with a small plane. I'm building the first one at 100% to see how I like its flight characteristics then I'll scale one up to 200% for about a 42 inch wingspan and a beastly motor.

 

[JohnRambozo]

Thanks again, you make it sound easier than it is... I started to build the funjet and am taking lots of picture to post for build instructions as soon as I find time to do it.

No problem. Happy to help. I can't wait to see your build log.

 

[Hell2Go]

After taping my tiled plan together I lay it on my DTFB and use a metal scribe to poke a small hole at all line corners and intersections then using plan as a guide to connect the dots.


the top portion is the bottom of the wing, the first line from the top is the leading edge, the next line down is for the airfoil which I do a 50% cut then run a point of a skewer down it to develop a crease.


double 45deg v-cut


texst fold looks good, the edges come together nicely


transcribing location of aileron to bottom to cut out, leave 1/16 clearance when cutting


cut the aileron hinges

 

[Hell2Go]

I squish the foam a little along leading edge to get it to fold all the way without too much pressure


squish the crease cut to get wing to fold well and make room for glue (the glue in here will give the wing its strength)


reinforce the hinge line with some scotch tape. start with 1/8 inch on top of the step and the rest overhanging


with a card, start working the tape down the step to the hinge line for the full length of hinge line before working past the hinge line to avoid wrinkles


then work it down the rest of the way keeping the tape tight to surface throughout the hinge (practice on scrap pieces first to get the technique down, as this is a needed skill if you plan to cover your plane in packing tape and don't want wrinkles)


pick your spot for the servos right here. you want the servo horn 90deg to the hinge line or close as long as both sides are equal trace around servo and don't move it


I put a small piece of double sided scotch tape on top of the servo, folded wing and opened then traced servo on other side of wing


cut out the top layer of paper and pluck out the foam (I use a small flat tip screwdriver) don't damage the bottom paper


fold wing and mark it here


and here then unfold and...


draw a line and trim close to line but leave a little for sanding


make sure servo fits when folded and wire goes the right way (to centerline) and cut a little notch in each half in bottom portion for servo wires to go thru and don't forget the little rectangle hole for the servo horn to poke thru.

****** make sure you hook your servos up to the radio to center them before you glue them in place!!!! ********


your parts should look like this, halves are NOT glued together yet! This is the time to flip the pieces over and put on your colored packing tape, don't forget the bottom of the aileron and the under camber wingtip


OK point of no return! Gluing... glue servo to the lower half of wing, go easy on the glue you don't wanna add too much weight from glue, let dry, then glue crease line only and fold til dry to get shape then open up, wrap servo wire past notch and tape down out of the way. Now glue leading edge, trailing edge and corner in front of aileron and fold quickly and gently hold til dry.


Use a triangle or some reference of 90deg and sand just till the edges are even and square

if your unsure about this technique refer to the FT Versawing build video here: http://flitetest.com/articles/ft-versa-wing-build


OK... it should look like this... this is where I'm at so far... cut out the rest of your parts and stop back soon for more building on this
ok

 

[kpl72]

Hell2G0 - Awesome job. Wow, this is fun to watch... Weather still has been stinky (as you know - I'm only about 2 hours east of you). I'm hoping maybe to get it in the air tomorrow indoor, otherwise I'll need to wait a week as I'm traveling next week...

You servo install sure looks a lot cleaner than mine.
Kevin

 

[Hell2Go]

I just folded up the fuse and it is wrong... I have to make adjustments, so DON'T PRINT THE PLAN YET! I gotta fix it first, working on it now.

 

[Hell2Go]

Hell2G0 - Awesome job. Wow, this is fun to watch... Weather still has been stinky (as you know - I'm only about 2 hours east of you). I'm hoping maybe to get it in the air tomorrow indoor, otherwise I'll need to wait a week as I'm traveling next week...

You servo install sure looks a lot cleaner than mine.
Kevin

Its cool that you are close, maybe you can come over this summer to fly in my private flying field!

 

[Hell2Go]

OK! I fixed the plan and added a page 2 that has the top and bottom sections of the nose. the length is over a tiny bit so you can trim to fit as you assemble the nose. fold and glue the fuse before you cut out the top and bottom of the nose so you can measure the width of the fuse. then make sure that the width of the foam in the top and bottom sections for the nose is just a hair wider than the fuse so you get a snug fit but not too tight.

 

[JohnRambozo]

OK! I fixed the plan and added a page 2 that has the top and bottom sections of the nose. the length is over a tiny bit so you can trim to fit as you assemble the nose. fold and glue the fuse before you cut out the top and bottom of the nose so you can measure the width of the fuse. then make sure that the width of the foam in the top and bottom sections for the nose is just a hair wider than the fuse so you get a snug fit but not too tight.

That's a cool little design. Nice buildlog and it looks like its going to be a lot of fun to fly.

 

[Hell2Go]

its a lot smaller than I though from looking at the pictures from the article... Kevin said it was a 22inch span but I guess it just didn't register, my rewound blue wonder will turn this little plane into a rocket. Once I get this in the air and see how it flys, I'll probly do another at 150%, I like the way a bigger plane flys, and I'm sure that will apply to all designs.

 

[JohnRambozo]

its a lot smaller than I though from looking at the pictures from the article... Kevin said it was a 22inch span but I guess it just didn't register, my rewound blue wonder will turn this little plane into a rocket. Once I get this in the air and see how it flys, I'll probly do another at 150%, I like the way a bigger plane flys, and I'm sure that will apply to all designs.

I'm with you on that. Somewhere around a 30 - 50 in wingspan is comfortable for me. I have a pretty good-sized park as my flying field. I like to use all of it and then some. Maybe I'm getting old, but I sometimes have trouble seeing the orientation when it gets far away.

That thing is definitely going to be a rocket!