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6mm Depron FT Simple Storch... The journey begins.

#1
Hi All,

Well, having had some issues with UK foam board and weight, I decided to take the plunge and get 10 sheets of Depron. I was so pleased to hear, on the podcast, about Peters idea/plan to adapt some of the FT designs, and I figured I'd have a go and start the ball rolling. So this is the beginning of a build thread where I'll be trying out my adapted design and sharing how I get along. I'm not sure if the sheet sizes for Depron are a standard, but the stuff I bought is 1000 x 700mm and so I've taken the plans and re-layed them to fit onto 2 sheets, £6 worth of foam!

I'm hoping that it's okay to post the plans here, but someone do please let me know if that's not ok. I've not included the notes and stuff from the full plans. These are full and tiled, with the tiled ones intended to be printed on A4 paper (hope it's not too UK centric) and a grid to make it easier.

WARNING: I have not yet built from these plans so I'm yet to discover if I've made any errors in increasing the slots to account for the extra 2mm thickness, and also the A and B folds, where inside or outside dimension of the final part is the main factor. I've also made some of the parts separate due to the fact that I don't have the paper to worry about. Use at your own risk.

My first question to anyone here using Depron is: What would you recommend for covering? I have bought some Fablon (sticky back plastic) but I don't know if this'll be too heavy. I may just try clear packing tape for this first prototype. I did like the look of the way they did it in the waterproofing episode, and even better that I don't need to remove paper.
 

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#2
After a week of building, I have a plane!

I think that the modified plans seem to have worked out pretty well. I looked around for tips on cutting out the Depron with the plans and went with pins to hold the plans in place, and also as a stop for my ruler during long cuts, to prevent it slipping.
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With the spars and power pod, I taped the outer side of the foam and then cut it in the same way as foam board and removed the section. With the large parts of the fuselage though, I taped them together with a scrap piece of foam as a spacer.
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For the wing, decided to cover the parts flat with the fablon. I didn't get pictures of this but I did it by taping down the vinyl with the peal off back facing up. I pealed back the corners a little bit and used blue tape to stick it to the bench. I was then able to fully peal of the backing, without it curling up, and place the wing part on it. I then flipped it over and smoothed it gently out with a gift card. The result was really nice and when I folded the wing up it wend really taught and looks really solid!
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I did have a couple of problems with the wing, and the thickness of the Depron.

After doing the double bevel on the leading edge at 45˚ there was no way the Depron was going to crush down enough to fold the wing over. I needed to go over and take a much heavier cut to about 20˚, or less, before I could get it to happily fold over and go down. I think the covering was also fighting me a little here too, by not wanting to stretch around the leading edge.

The second problem with the wing, is the dihedral. I think due to the thickness of the Depron, the outer top surface of the wing surface is 2mm higher, and that meant that when the wing tip was bent up with the guage, it hit the other side and didn't have a large enough gap to create the correct dihedral. I only found this after I glued it up :( When I removed the gauge (ignore the spelling errors on my gauge), it dropped down to about 2/3 the total. I not sure, how much will this affect the flight characteristics?
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I didn't end up covering the entire plane with the vinyl as I was worried about weight. I did one side on the tail parts so that I had a hinge and then use the hot glue to reinforce. I also decide to use a couple of bits of 2mm CF rod I had to reinforce the horizontal stabiliser and elevator as they seemed too floppy and curved slightly from the covering.
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I used my 3D printer to make the FT control horns. Had another slight problem here, where I put the control horns on while the parts were flat and then realised that once put together, the rudder one was on the wrong side! Whoops.

I also 3D printed the reinforcements for the power pod and added them for the wing dowels as it started to pull through the depron as soon as I tried to put the wing on.
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I think that's most of the build covered. I followed the landing gear to the letter but started out with 16" not 15.5" wire so my landing gear is swept forward a little more.
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And here's the final thing with the wheels on! 3" foam wheels.
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This is my first build of a plane like this, I've only done the FT Flyer before. I hope that the info is useful to other people starting out and looking to use the FT plans with Depron.

Cheers
 
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#3
Won't balance!

So now I have it all built I have one problem. I cant seem to get it to balance out! I'm following the 2" (51mm) back from the leading edge, but with a 3S 2200 xthin battery, I just can't put it far enough forward to get it to balance out the tail. I'm worried that the reinforcements on the tail have added too much weight. Even trying with a 3S 3300 it needs to be sticking out under the motor before it'll balance.

The weight of the plane without the battery is 825g (~29oz).

The motor is Turnigy D2830-11 1000Kv (https://www.hobbyking.com/hobbyking..._11_1000kv_Brushless_Motor_UK_Warehouse_.html). Maybe the motor isn't heavy enough?

Does anyone have any advice for when the balance is this far out?

Cheers
 

Winglet

Active member
#4
It's gotta balance. Move everything as far forward as you possibly can. (sounds like you already have) If that doesn't work, add some lead to the nose. That is all you can do. I don't think a little extra weight way forward on the nose is going to hurt this airplane? Flying it with an aft CG certainly will.
 
#5
Winglet, thanks for the reply. Yes I've tried moving the battery so far forward it's nearly hitting the prop. I think I'm going to try moving the entire power pod forward 1/2 - 1 inch and see if that helps. I'm a little reluctant to add dead weight but I may try with the 3300 if I cant get the 2200 far enough forward with the power pod moved.

Would moving the power pod (and therefore the prop as well) forwards have any detrimental affect on air flow over the surfaces?

Cheers
 
#8
you can move the wing backwards a little to help compensate. I made a 5mm spacer, that sits on the very front of the wing saddle, to move the wing back 5mm, this means i had to use less weight to balance out the plane.
 
#9
Finally a maiden!!

Hey,

Sorry for the abandoned thread. I only got a chance to go back to this build and take it out this week!! Got it to balance out with a standard size 2200 zippy battery, which is much shorter so all it's weight is far forward. I didn't realise just how much the battery being long would take its weight back and the 3300 I tried was about the same length.

The very first flight was SO good and it flew really nicely and slow. Surprised me just how well it lifted off straight and climbed out. Did a circle and brought it in for a landing with only a little bounce!!! First 4ch take off AND landing.

Second flight (the one my daughter was filming doh) went less well. I'd already pushed it later than I should have and the light was failing but I wanted some more time for this first outing. Again, took off really well and tried to climb and attempted to trim out the slight left turn (not sure but think I trimmed the aileron rather than the rudder oops)). Then it went a little too far, and at just the wrong angle, and seemed to disappear!! I then lost orientation and tried to pull up to get it back in sight. Trying to pull it around and not judging the distance, it flew into a tree :( I was too low to be trimming.

I was very lucky that it came crashing down to the ground on it's own. Elevator torn on the other side to the horn, wing bands pinged off, wing detached and the wing servo extensions torn out. Otherwise quite minor damage. Phew!! Could have been a lot worse.

All repaired the same night and back in the air today. This time with a Mobius onboard! (no risk, no reward)

I'm still very new and learning. I've joined a club but there's been no good weather time that coincides with non-work days. I've built another plane for indoor but ended up taking it out on a still evening. Design based on the FreeAir FreeBee (EPP LazyBee inspired)

One strange thing I've had twice now, is that I go to the park in the evening, when it's really quiet, and twice, first with the Bee and tonight with the Storch I've had the issue where it seems to really struggle to get lift. Even opening full throttle it seems like gravity is determined to have it's way and I end up ditching it back down. Batteries all charged and taking off into the wind. I took the Bee back out for a third time after the first great flight and the second crash and repair and it flew like a dream again. Tonight the Storch just didn't seem to want to stay in the air so after a few, shall we say "heavy" landings I decided to call it a day while she was still in one piece and before it got too dark.

Any ideas? Could it be a big area of sink? Cold air crashing down over it? It put me ind mind of salmon swimming up a waterfall.
 
#11
Thanks for the idea. I did check that and the writing was facing forward. I did notice that my motor was kind of "springy" and the can was able to move out from the mounting by 2mm ish. I thought maybe in the tree encounter that the shaft had been pushed back. So I took it off and will try another motor. Odd thing, when I took the motor off the firewall it seemed to stop pulling apart and be fine.

Also I picked up a non balanced new prop (in a hurry) so maybe that.
 
#12
Did you set up your ESC to get full throttle? Usually done by turning on Tx, setting throttle at full, plugging in battery, and then dropping throttle to zero after initial beeps. Check ESC docs to double check.

Another thought, with a heavier Depron build, maybe not enough takeoff speed for your weight?
 
#14
Well I had some very funny noises from the motor on the last outing and I decided to swap the 10x5 APC prop for the 9x4.7 SlowFly prop. And that seems to have worked a treat. The motor is now the NTM 28-26 1200Kv.

Here's a video:
https://youtu.be/ne47fNsXCNA

Because on the takeoff she seemed to always want to veer hard to the left while still on the ground, I decided to fabricate a steerable tail wheel. Looking at some pics online I ended up with this:

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The hub was 3d printed then the hole drilled out to 4mm. I glued on 2 rough circles of 6mm depron to give 12mm thick. I then put an M4 bolt up through with a nut and spun it in the drill press and sanded it to a nice shape. Finally I used a 4mm carbon tube with 2mm ID to allow the wire to fit.

The mounting block is 3 bits of balsa laminated together with the centre bit at 90 degrees to the other bits (balsa-ply). It's all glued up with CA and there are two 3mm CF rods going up into the fuselage. The yellow is some kevlar roving covered in CA to prevent the back tearing out, which it did at one point while building it. There's also a carbon tube in there for the wire pivot to bear on. The arm and the rubber band idea were gathered from some pics on the forums. The screw is hot glued in. I was really trying to keep the weight down, for fear of it not balancing out again, and it came in at 5g for the whole thing.

It probably should have a spring in the wire but this was all I had. I'll update on how well it stands up to beginner "landings" (or controlled crashes)

I took it out to fly yesterday, but it turned out too windy when I got there and there was an event on nearby so all I did was taxi about a little bit, but it made a HUGE difference to the control on the ground. Can't wait to take it up again.