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Oct 28, 2020, 05:00 PM
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Build Log

Full fuse ~1m MiniExtra


It's been long time since I've scratch built anything from foam. However, I sold my Skywing 38" Mini Edge last spring and as weather is getting worse and sunlight is limited I find myself missing some simple aerobatic plane that I can use for quick flights on the nearby farm field.

I also went through my parts stock and found that I have something like 4-5 sheets of foam and four 9g servos and miscellaneous other bits and pieces. The size of the plane was also mandated by the fact that I wanted to be able to use my existing 1000mAh 3S batteries with it.

For a long time I have admired the full fuse Extra build by Arm1s. To me the original design had almost all that simple foam plane needs.

As I wanted a bit smaller plane I took the (really great) plans drawn by Dreamcatcher, scaled them to 85% to end up with plane approximately 1m wingspan. The plan is to try to build the wings from Depron instead of hot wire cut. And to make plane a bit more durable & tidy I will try to put normal chinacote (in my case from HobbyKing) on the plane.

The power line will be similar to those Skywing & FutureModel 38" planes. Meaning ~75g ~1200kv brushless motor with ~10x5 prop for about 300W. If I can keep the weight down, it should be plenty.
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Oct 28, 2020, 05:05 PM
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First sessions with the build...


The work started by printing the plans. I scaled the original plan to 85%, taped all the printed A4 sheets together and started to cut parts.

Cutting parts was relative quick task that I did in two batches during two evenings. First evening was spent to cut fuselage parts and second to finalize with wings. Just remember to use really sharp knife, use some tape to fix the drawing on foam sheet and cutting will be easy!

Fuselage panels were longer than my foam sheets so I had to cut them from two different pieces. This shouldn't be a problem, just cut the sheets diagonally to have as long glue joint as possible.
Oct 29, 2020, 04:47 PM
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Woodworking


Well, this is a foamie forum, but I had an urge to try hybrid build. So the idea is to make plane a bit stronger and more rigid by building a wooden internal frame. This frame will also hold the battery try nicely.

Anyways, the work continued first with rudder & elevator. They were strengthened with balsa strips and a bit bigger balsa piece as elevator joiner. Then the work started with first phases of internal frame build. Nothing fancy and I'm basically just hacking this together as I go.

I also cut the wing profiles from balsa and motor firewall from 3mm ply.
Oct 29, 2020, 05:00 PM
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Electronics testing...


As I already mentioned, the powerline for this size plane is more or less proven by all the good 38" Skywing & Future Models plane we have. Typically the recommendation is ~70g motor with around 1200kv with 10-11" prop and 3S batteries.

In my case I got hold of new Joker J3530-11-V3 motor affordably. This motor is manufactured by Dualsky, but just labeled with Joker brand (for Lindinger & some other resellers).

To verify that it performs to expected level I mounted it on woodblock and put a powermeter on it. I only had a flimsy GWS 10x6 prop to test with it, but that should give me some comparable numbers even though I don't like that prop too much. I've tested my ex. Skywing 38" EPP MiniEdge with the same prop.

The tested numbers were just on the expected ball park.

Peak measures:
29,9 A
333 Watts
Around 1kg (of push power against normal kitchen scale, not very accurate)

I used Castle Creations ESC in the tests with logging enabled and logs gave similar numbers:
28,9 A
323 Watts

The motor didn't get too hot in the tests, so from this perspective everything looks ok. Just need to get better prop and also I would like to get a suitable ESC as I don't have any extra "small" 30-40A ESCs available at the moment.
Nov 01, 2020, 03:46 PM
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Finalizing internal frame


I continued to glue couple of sticks at the time to get the internal frame structure strong enough (hopefully).

Wing will be attached with 6mm carbon fiber tube and I drilled the wing profile and the balsa panel that will be glued to internal frame on top of each other. Unfortunately forgot to take pictures of this page.

Then I continued by gluing the balsa panels to the frame - used some carbon rods to ensure the alignment.

Then I cut firewall, landing gear plate and battery tray. Firewall and battery tray was drilled to clear the motor shaft and to lighten parts. Then it was just matter of gluing them into place with epoxy. For all other glue joints I had used just normal white wood glue.

The internal frame ended up weighting 39 grams.
Nov 01, 2020, 03:54 PM
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Fuselage


As the internal frame was ready the time was for quicker progress. Aligned and glued the side panel in place and then continued with top & bottom panels. Plenty of tape was used and the fuselage ended up looking like a zebra.

The curve of the foam panels in front of the plane was easily achieved by just rolling the parts against table edge. The foam will curve easily as these are not radical angles.

For this phase I used Uhu Por.
Nov 05, 2020, 04:43 PM
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Fuselage finishing...


To finalize main tasks with the fuse I needed to glue another ply plate for landing gear and also tail gear. Then it was matter of sanding the edges and starting to build the canopy...
Nov 05, 2020, 04:57 PM
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Wing construction


Well, how to say it... I just don't like doing wings. I don't know whether it is because of me lacking technique or just the detail you need to put into them to get them good.

First I bend the main wing panels against table edge to get some curve on them before going any further.

I will have 6mm carbon fiber spar as main spar. I drilled small balsa blocks to be able to align that spar correctly inside wing. Some normal styrox foam strips were also glued to help align the spar and to distribute the stresses between wing panels and the spar. Couple of balsa spars were also glued into the wing. Some sanding was required for spars and also wing edge to provide adequate shape and gluing surface.

Then I glued the panels together, used lot of tape to get edges tight and put the wings under pressure to dry.

After a night of drying it was time to pefrom a quick test assembly to see whether wings fit nicely. No problems there, fortunately. Then it was matter of cutting ailerons loose. I had aligned one of the balsa spars in the aileron joint and it was matter of cutting them out carefully.
Nov 10, 2020, 03:21 PM
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Details and more details...


The fuse is more or less ready for covering now. Landing gear ply strengthening turned out ok. I've been also working on the canopy, should still decide how the canopy locking will be made. I'll create now a temporary "canopy" from normal styrox foam, but later I'll create proper wood plug to make a clear plastic one. Anyways probably worth first to see how the plane flies.

I also continued with wings. Small balsa strips were glued on wing trailing edge to make it resistant for dings. I also needed to add balsa to the aileron leading edge to ensure that proper deflection can be achieved. Not the cleanest solution this way, but should work fine. Finally balsa profile was glued to inside of wings. Wing is glued from this to fuse eventually. I also cut aileron servo slots.
Nov 12, 2020, 04:40 PM
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Fuselage covering


Ok, two covering sessions later I'm ready with the fuselage. This is just as labor intensive as doing a bigger plane. Or actually more, as the covering iron temp needs to be relative low and thus covering just is slow.

I used oracover depron "primer" on edges and critical places to ensure that covering sticks. Didn't use it everywhere, though. I got this bottle cheap, so I thought it's worth to try.

Otherwise this is totally same process as with balsa planes, just a bit more slower and you can't shrink covering quite that much on these iron temperatures. Haven't used hot air gun, too worried about ruining the foam.

The covering I use is a blend of HobbyKing covering (red & white) and real oracover (black & purple). Both work just fine... And to get shapes even somehow similar on both sides I use paper templates to cut covering. On this plane I try to avoid multiple layers as much as possible as on this small plane you really don't want any extra weight.

The motivation for the scheme was gotten from Hangar 9 Extra 330SC 60e... Just simplified a bit and bottom will be different.
Nov 12, 2020, 04:52 PM
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Looks very nice.
How is the weight coming on?
Nov 12, 2020, 05:30 PM
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I'm also impatiently waiting on how much the covering will add... If I can stay within the weights of Skywing & Future Model 38" planes, then I should be safe.
Nov 14, 2020, 11:35 AM
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Outstanding job Late99. Looking forward to seeing the Extra ready to fly.

I also am a big fan of smaller grab and go type airplanes for quick flying sessions when the winter weather deteriorates. I typically always have a couple smaller foamies for this type of flying. I’ve found they can actually tolerate a fair amount of wind too.
Nov 14, 2020, 02:56 PM
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Wings...


Thanks guys!

... Two covering sessions later....

I have to say that this has been one exhausting plane to cover. The iron temps are required to be kept low and it really slows down covering job. And basically doing small pieces is not any easier than doing the same thing for a bigger plane.

Nothing special with the wing progress... Went pretty smoothly (just slow).

The current weights:

Covered airframe: 325g
Battery: 99g
Electronics & horns & etc: 220g (estimated)
Main landing gear: 40g (max, estimated)
Total: 684g (estimated)

I'm hoping to save some weight on some small items, but let's see how it goes. Covering added approximately 85g. Quite a lot, but it also give much better look and brings a lot of strength. The difference in strength is really considerable.

Now we have an ARF.
Nov 14, 2020, 04:21 PM
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Very impressive work.


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