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$1 swappable trainer

rcspaceflight

creator of virtual planes
#1
I want to eventually turn this project into an article, but I thought I'd give everyone a preview with this thread.

This the fourth plane I've build with this concept. Technically it's the third version but it feels like the second version because I didn't like the first one I built and I never flew it.

The concept was simple. I wanted to build a good 3channel trainer out of a single sheet of foam board. I wanted it like a high wing noob tube. I also want to be able to modify the wings so it could be a 4channel. Something easy to build, easy to fly, and cheap.

That earlier version that I built two of looked and flew great, but I kept folding the wings. I had a 40" wingspan with a 6" chord and that was just too long and thin for Dollar Tree Foam Board to handle. So I opted to shorten the wings, but add a bottom plate of foam to strengthen the wing. I originally had 10" long wing tips with dihedral, but I brought them down to only 5". I loose looks, but I add strength to the wings.

Well, I don't want this thread to be too long. So here are some pictures of the final version.

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I flew it a few times today. The plane did bob around in the air but it was a little breezy. The shallow dihedral with the small wing tips seems to do the job though. The airfoil does provide a great slope rate. I flew with a 2.2amp 3cell battery with an 8x4 prop. It provided plenty of speed but the plane still could go slow and fly great.

I didn't record any video of it yet. I want to eventually record a bunch, edit a good video showing off the plane, and then build another one to either get a build video or just a build log, and then put that all together into an article.

If you want the plans now I can provide them. If the tail of this plane looks familiar, it's because the rudder and elevator are exactly the same as the FT Flyer. I knew by coping existing plans for parts it would be easier to build and to print off and transfer the plans.
 

rcspaceflight

creator of virtual planes
#3
Thanks. It did look better, IMO, with the longer wing tips. But this plane isn't about it's looks. It's by no means ugly though.

I think I have to change my plans a bit. I flew the plane again when it was too windy out, plus I think I moved my CG too far foward, and I don't think I had enough throws. Basically, I cut the throttle and tried to bring the plane down from high up and it came down too fast with it's nose too far down. Now it's all beat up. I think I'll do the build log and then record video of the new one. I think with how big and flat the elevator is, the CG got pushed back to a spot that I didn't expect it to be. I should have just leaved the CG alone because it flew great where I first had it. My plane pulled up when I would have full throttle, but I think my trim was off. Live and learn. I'll stop rambling.
 

Foam Addict

Squirrel member
#4
I love planes like that!
My first scratchbuild that flew well, (if at all) was a plane with a kfm-2 airfoil. other than that, it was a dead ringer for that plane.
 

triwia

Junior Member
#5
rcspaceflight, I definitely think your design has merit.

I would love, love, love, if there were swappable, quick build, RET and/or aileron trainer that were in the 40" range. Where I fly there is a constant 3-7mph wind. I know the old fogey and smash drone exist, but there needs to be middle ground between them and the bloody wonder. Maybe a bloody wonder with twice the wingspan and undercamber??
 

rcspaceflight

creator of virtual planes
#6
rcspaceflight, I definitely think your design has merit.

I would love, love, love, if there were swappable, quick build, RET and/or aileron trainer that were in the 40" range. Where I fly there is a constant 3-7mph wind. I know the old fogey and smash drone exist, but there needs to be middle ground between them and the bloody wonder. Maybe a bloody wonder with twice the wingspan and undercamber??
I'm still working on some stuff to get the article written. I'd hate to half do an article, that's what the forum is for. But this plane could easily be altered to have a 40" wingspan and ailerons instead of only a 30" wingspan. You'd need more than one sheet of foam board, but foam board is cheap enough.

I guess I do have a picture of the 40" wingspan version that I folded the wings on. This version was bad for multiple reasons. Like that I have too much dihedral on the wing tips. But mostly the wings were too weak.
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I actually duct taped the plane (first pictures) back together today and flew it. But one of my wing tips got loose (from a crash) and folded during a right turn. This plane does fly great and I need to actually work on building a second one, take plenty of photos for a build log, and then start recording some video of it. But I think the video will have to be of it flying in the wind with the way the weather has be lately.
 

rcspaceflight

creator of virtual planes
#7
Okay, so today I built another one so I could do a build log. I didn't install the electronics yet and I think the weather will be too bad to fly for a while so it might be another week or two before I get some flying footage.

This picture is to show how to lay out the pieces to get the plane out of a single sheet of foam. I do use pretty much the whole sheet. Pictured here is the power pod, elevator, and rudder which are all from the FT Flyer plans. The two squares are 6" x 5" and are the wing tips.
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This picture is to show the rest of the sheet of Dollar Tree Foam Board. The fuselage is 5" x 20" and the wings are 11" x 20".
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After cutting out all of those pieces, I worked on the fuselage fist. I used the power pod plans to mark out the pieces you remove for the fold. To get ahead of myself, the reason why I am copying the cuts exactly from the power pod is because the power pod is an "A" style fold and the fuselage will be a "B" style fold. This means that the "B" folded fuselage will be bigger than the "A" folded pod and the pod will fit perfectly into the fuselage.
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This is to show how the different ways of folding the two pieces that are cut the exact same way will fit together perfectly.
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After the power pod is glued, but before the fuselage is glued, you want to cut out all of the notches. First is for the tabs of the pod. I just used the pod to measure where to cut out the slots.
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Always test fit!
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Next is to cut out a slot for the rudder. Draw a center line at the tail and make the cut foam board thick.
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I made mine about two and a half inches into the fuselage. This will leave plenty of rudder and elevator sticking out to make the plane longer than just 20". Yet it has enough contact between the rudder and fuselage for a strong connection.
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Now the fuselage is all cut out and ready to glue that "B" fold!
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Mostly to double check that these posts turn out well, I'm breaking the different pieces up into different posts. I'd also hate to do all of the work writing it up and have a problem with my internet, that I tend to have.
 
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rcspaceflight

creator of virtual planes
#8
Okay, so the fuselage is done. Next is to finish off the rudder and elevator so they can be glued to the fuselage. Since this plane has the exact same rudder and elevator as the FT Flyer, and because they are mounted the exact same way, I didn't bother to show how to finish them off. You should know how to cut the bevels and the hole to slide the rudder into the elevator. I also didn't show any steps with the power pod because Flite Test explains that better than I could.

Now that I actually look at my pictures, I probably should have put these two along with the post about the fuselage. Oh well.

I want to note that this fuselage is taller than the FT Flyer fuselage so there is a gap between the rudder and the elevator. You can either remove some foam from the rudder, or you can just have a little bit of a gap. I just left a gap. It's not that big of a gap. I should note that because of this, you don't glue the rudder and elevator together and then glue that to the fuselage. I just glued the rudder to the fuselage and then glued the elevator onto it. It made it easier to align everything up. But if you did glue the rudder and elevator together first, then it's just a matter of removing some foam from the rudder.

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rcspaceflight

creator of virtual planes
#10
Onto the wings. The wings are rather simple, so don't worry.

First we take our 11" x 20" piece and split the 11" up into three pieces. 5", 2", and 4" segments divided up with score cuts.
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The wings are folded up like this. I added lengths to the picture just because I could. I do want to note that the flat bottom of the wing and the tail edge of the top of the wing both touch the table. At least it's really close to touching the table.
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The wing should be about an inch tall total. When glueing the wing up, start with the top crack first. Fill it with glue, hold the wing so the bottom is flat on a table, and then squeegee off the extra glue. Then glue the tail edge so the flat bottom doesn't flop around. Then I glued the leading edge. Just like when you glue a hindge of a control surface, add a little bit of hot glue and then squeegee it into the foam. Not really necessary for the leading edge, but it'll make it stronger for when you crash into stuff.
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Next is the wing tips. These are those two 5" x 6" pieces I made you cut out. You start by cutting a score cut to split the tips into a 2" and a 4" segment to match the main center wing you just made.
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I don't know how well these photos show it, but you measure 1/4" into the edge of the wing tip. The line goes straight down to the score cut, and then goes to the edge of the wing tip.
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Now cut off those pieces you marked off.
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Now tape the wing tips to the center wing. Tape the flat part of the wing tip to the wing...
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...then move the angle cut piece so it is also flat along the center wing. This creates the dihedral of the wing tips. :)
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When glueing the wing tips be sure to use plenty of glue between the center wing and the wing tips, squeegee off the excess. Also be sure to fill in the crack at the top of the wing tips. I forgot to do that once.

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Mark the center of the wings and the center of the fuselage.
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I put the wings almost 5" back from the nose. This is how far I had them back for the plane I built before this one. This put the CG almost spot on without the battery. Of course that depends on the motor and where you put the servos and Rx and ESC and such.
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Glue on the wings and you're almost all done.
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rcspaceflight

creator of virtual planes
#11
To make life easier I just used two BBQ skewers to hold the power pod into place. Nothing wrong with Flite Test's way of doing it, but I like this way better. Another tip, do this before you tape up the power pod. It's hard to push a skewer through the tape. Where as taping the firewall on after this step, you can use a knife to cut out the holes for the skewers.
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There are multiple ways to mount the servos. It's really up to you.

I think this is the best way to mount the servos. This way they aren't exposed to the elements and don't produce any drag. The hard part is to thread the control rods through.
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This way is just like the FT Flyer. A much easier way to go and I might do it this way. (I haven't mounted my servos yet.)
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All that's left is the electronics and such. Stuff I have yet to do and you should already know this stuff. :D
 

rcspaceflight

creator of virtual planes
#12
Nice! Do you think you'd make downloadable plans for this? That would be amazing! :)
Probably not. Three of the pieces (the power pod, rudder, and elevator) are from the FT Flyer. You can download those plans to get those pieces. And then the rest of the pieces are just rectangles. I purposely designed this plane so you don't need any plans... other than the FT Flyer plans.
 

rcspaceflight

creator of virtual planes
#13
I probably shouldn't share this video because it makes the plane look bad, but the crash is worth watching.

I decided that I wanted to cover the plane with chrome duct tape. Which turned out to be a huge mistake because it left the plane too heavy. At least with the motor I'm using. With my bigger motor it probably would have been fine, but I'd have to fly fast. Another issue was that by making all of the foam heavy with duct tape, it made the plane tail heavy. I didn't want to add weight to an already over weight plane, so I tried it as is. Mistake.
 

rcspaceflight

creator of virtual planes
#15
cool can you make printable plans? is it a good trainer does the new wing fold easily? can it loop?
I'll look into making printable plans. I'm not sure how I should go about that, but I should figure something out.

I think it should be a good trainer. That's at least what I was after doing.

The wings hold up really well as long as the wing tips are glued on real good. But sometimes the wing tip will hit the ground and loosen the wing tip.

I built another one today and tried to get some footage. It didn't turn out very well because I have the bad habit of accidentally making a thrust angle and flying anyways. I tried to loop it, but I didn't have the plane lined up right but I'll say that it can.


I know the plane sounds horrible. And no, it's not my prop. It's the motor. ... I guess I have a motor to either try to fix or to replace.

It's supposed to be nice out tomorrow too. So I plan on fixing it tomorrow and trying to get some more footage.
 

ofiesens2

Professional noob
#18
Ok. Im starting to freak out about this year's science fair. I am testing which airfoil generates more lift: a conventional rounded airfoil or a KFm airfoil. So I built one Baby blender wing and a KFm wing to the same dimensions, along with a home built wing tunnel.
Which ended in an epic failure. I think my plan B is to build a fuselage and swap out the wings, chuck them off a ledge, and see how far they fly as a glider. My wings are both 24 inches long. Do you think those wings will work with this basic fuse and tail assembly?
 

rcspaceflight

creator of virtual planes
#19
Ok. Im starting to freak out about this year's science fair. I am testing which airfoil generates more lift: a conventional rounded airfoil or a KFm airfoil. So I built one Baby blender wing and a KFm wing to the same dimensions, along with a home built wing tunnel.
Which ended in an epic failure. I think my plan B is to build a fuselage and swap out the wings, chuck them off a ledge, and see how far they fly as a glider. My wings are both 24 inches long. Do you think those wings will work with this basic fuse and tail assembly?
They should. This plane is very, very similar to the FT Flyer. The fuselage is a little different to make it easier to mount wings on to.

It may not be the best glider, but will certainly work for a comparison for your science fair.

I used the FT Flyer plans for the rudder and elevator, so print off those plans, copy the fuselage I made, and then either make a power pod to stiffen up the fuselage or add a bottom to it. Of course you'll need to add nose weight to get the CG right. And then glue on a couple of popsicle sticks to the bottom of the fuselage and mount the wings on with rubber bands. You shouldn't need any tabs or anything to hold the wings in place. The friction from rubber bands should be enough and will allow for the wings to shift if it hits the floor too hard.

Good luck with the project and the science fair.

Oh, and I used a 30" wingspan with polyhedral on the wing tips. 24" wingspan should be fine since you're just comparing them. However, to keep the plane from tip stalling you really, really, really should add polyhedral to your wings. Just make wing tips to add to your current wings and set them at about 10* - 15* angle. You could probably try it without the wing tips, but don't chuck it off of a ledge. Hopefully you'll have a measurable difference just throwing them from 5 feet off of the ground. The higher up you throw it, the worse the crash will be. Without the stability of polyhedral, don't risk an epic crash from high up.
 

ofiesens2

Professional noob
#20
Thank you. Also, I have a couple questions. Where is the CG located on the plane? Would simple dihedral have the same effect as polyhedral? Would I be able to put in polyhedral by cutting off a 4 or 5 inch piece of the the end of each wing tip, sanding a slight bevel to it, and reattaching it with hot glue?
Thanks again.