S800 Sky Shadow fixed wing build log and impression – part 1

2016 will be marked down in history as ‘Year of the Miniquad’. Honestly, the amount of new kit that’s came out in 2016 was absolutely hideous. There isn’t a week without a new frame, new motor, new protocol, new cam and new hype.  But, just like your mini quad, what comes up – must come down. Forecasting in 2017 I see wings being massive, race wings specifically.

Like the small majority my first experience of RC flight was via quads. This turned out to be a fantastic gateway drug into anything RC that flies. After seing Trappy and TBS doing their thing with wings I knew I had to get a fixed wing. Flying up mountains, being in the air for more than 3mins while doing rolls and cruising down paths….yep I want that. Another great inspiration was the Youtube channel Adam G does FPV, this lad has some great long range and mountain diving videos. 100% inspiration to go out and play in unrestricted landscape.

Also, its fair to suggest that my left thumb loves the idea of having a break from time to time.

The problem was and still is the whole arts and crafts part of it. Don’t get me wrong, I love solder, bolts, nuts, CF etc but foam, tape, glue just remind me a bit of 1st year Uni glider challenge. Fixed wing rc plane building reminds me more of the difference between a Joiner and a Welder. Your either one of the other. (#yermawsawelder).

However, that’s a poor excuse for not getting involved. I mean, think of the amount of people who get stuck into the miniquads who will take a good 10mins to figure out what is wrong here:

Given that I wanted something more or less built, but not perfected (as I wanted to make it my own) I started to keep my ears to the ground. Mr Thrust (ie. Marty) was selling a TBS Capi he fell out of love with, a deal was struck and the learning process began (the added bonus that the wing came with IRC UHF gear). The TBS wing was great, but it has it downfalls- it’s a fairly old school design for 2S, it’s a heavy blunt nose and it was very prone to hyper stall when too heavy. The battery, esc etc are all exposed making the centre body quite inefficient as an airfoil. This, allied with a 3s set up made it quite a challenge (it now however flies great, just quite a struggle to get up in the air). Also just before this I bought a mini-Sky hunter for a steal with a decent FPV set up, it was good fun to fly, just not fast enough. And after about 10 crashes, it had to be retired.

So lets recap:

  • Love flying – Check
  • Want fixed wing for more flight time and cruise ability- Check
  • Bought basher plane (became basher) to learn the ins and outs- Check
  • Bought wing to learn about wings (along with some sweet long range gear)- Check

So all that was left now was to build something from scratch using all the above knowledge.

I wanted something clean and new to build that offered a solid fpv and HD recording platform without breaking the bank.

Enter the S800 Sky Shadow

I will skip some of the finer details about the kit, what is included, as there are great Youtube videos online (Bruce- RC model reviews has a great one) that go into more detail than I could ever have the energy for.

The S800 Sky Shadow wing is constructed from moulded EPP. Which is  extremely durable but expensive to make as moulds have to be machined first (the Ritewing Drak mould was rumoured to be $60,000) From my time with the TBS Capi I have learnt a lot in terms of what works/doesn’t work with this type of foam. The quality of the foam and the finish on the model is extremely good for the price. Some parts will need to be broken free of their mould tags but I gives you some spare bits as packing for FPV gear.

How you assemble these parts will ultimately determine durability, flight characteristic and  life span of the model.

The arts and crafts build

(Spars, left and right wing and main body)

For this build I will be using Gorilla Glue, Hot Glue and very low viscosity CA. Gorilla glue from my experience works well with EPP foam as it grabs the foam very well. It can be a bit of a pain to deal with as it expands exponentially which causes messy overspill if you are not careful. Important to note that the carbon fibre (CF) spars will not bond well with the gorilla glue so I am using the CA where the CF requires to be bonded. Hot Glue works great but can melt the foam so I use in small quantities where a semi instant bond is required. Hot glue is also adventitious from the point that it can be removed with alcohol.

(Low viscosity CA)

(Gorilla Glue)

The edges for the wings and winglets will need roughed up to promote full adhesion between the surfaces. I use P40 grit sand paper with a very light hand as too much has the chance of grabbing the foam and pulling part of the edge off (bad times). In hind sight P40 is way to rough so something like P200 may be better to key the surfaces.

Before:

After:

I also roughed up the CF spars to ensure they stick well with the CA.

Important also to watch CF dust, so please wear a suitable mask and gloves (or do it under running water).

I then used to Isopropyl Alcohol to clean the surfaces down. This also can be removed to remove hot glue- Bonus

 

With the surfaces clean I then bonded the wings to the main body using Gorilla glue.  Water is used to set off the glue so this is sprayed onto one side and pressed against the other with the glue. Then using masking tape I ensured the joint was tight and true. This was repeated on both sides and allowed to dry overnight.

In the learning process of this build it would have been better to push the carbon spars through at this point also. Fellow Propnut’s pilot Keiren did this and this helped keep the wing aligned and true during drying. I slid the spars in after drying and bonded them in with no negative side effects but in hind sight Kieren’s way makes more sense.

The CF spars were then test fitted, coated in CA and pushed into place. The infill pieces of foam for the spars were also fitted at this point and trimmed true to the wing surface.

As I am going to laminate the full wing I took the opportunity to laminate the winglets (vertical stabiliser) prior to bonding them to the wing.  Speaking about laminate. This is definitely not a required process. The EPP is very strong and crash resistant but this extra step I feel keeps the wing clean and gives it that little bit more protection. The laminate I am using is 3mil thick and using the iron at the lowest setting to try stop bobbling of the foam.

 

As I am going to laminate the full wing I took the opportunity to laminate the winglets (vertical stabiliser) prior to bonding them to the wing.

I bonded the winglets to the wing using black hot glue. I did this as I wanted to hold the pieces in the exact position and not have to tape them up. Also hot glue bonds can be broken easier than Gorilla glue while providing much more adhesion than CA. The means that if I severely damage a winglet I can replace by remove it (not clean or pretty but possible).

Once that is done you should have a complete wing superstructure solid and true.

(Finished S800 Sky Shadow wing frame)

(Full wing laminated- few wrinkles but overall OK)

Electronics

After this the hard work is pretty much done. The rest of the job simply involves mounting the motor and adding electronics. The supplied motor is a 2205, 2300kV Sunnysky. Its OK and seems to be fairly good for what it is, but its not the end all and be all compared to something like the new Emax or XNova. With this is mind its important to mount the motor so you can remove it in the future if need be.

I experimented a little with the mounts, first using the supplied stand offs, then some plastic ones (shown), then eventually no stand offs. This helped the CG a little and in the future if a larger motor is installed, will bring it closer to the wing again, helping keep weight forward.

(no stand off)

However, the major downside of this is that your aircraft will now be very loud. The air coming off the trailing edge will be slapped hard by the blades causing an enjoyable (but anti-social) noise. This will lose you efficiency also.  A great demonstration of this can be found here:

I will more than likely experiment with some different ways of increasing the prop distance from the trailing edge.

For the electronics package, I went with :

  • Foxteer HS117 (with voltage OSD)
  • Tramp HV VTX
  • Frsky D4R-II RX
  • Included ESC
  • Included Motor
  • Included PDB and stabiliser.

On the subject of using the PDB and FC, although I didn’t feel I would use the stabilisation It offered a way to easily manage the 5v/12v required. And if I felt like it, play about the stability modes. I used the supplied 30A ESC which looks a little light for its job but is still holding out to this date. A lot of people had major issues with this cutting out, so I suggest you replace if you are not confident to start with.

-End of part 1. Keep an eye out for part 2 coming soon.

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