EDIT - For those who don't want to flick through the whole thread, here's a direct link to the FPV maiden...
View this video on YouTube
It was suggested to me by SENTRY 62 on helifreak that I come post this here, so here I am! Hello!
So anyway here's the start of a build log of my current big project! I'm quite excited about this one, hopefully you guys will like it! Apologies if this first post is too long a read... Hopefully if you're reading this anyway it'll all be of interest to you.
I think the French term "vol en immersion" best sums up my goals here. I want an aircraft with scale cockpit for not just an FPV experience, but a fully immersive experience. It won't offer the best unobstructed view, it won't be the easiest to fly, but it should be a great experience and an absolute blast... If I'm not buzzing after flying it I will have failed!
So first, I started with the design brief:
- Must be big enough to cope with a full array of FPV gear, pan tilt, OSD etc etc
- Must be a Foamy to mitigate damage to property or person should the worst happen! I must point out that I have no intention of flying near either, but you just never know.
- Must be able to belly land, and preferably also be able to take gear in case I find somewhere suitable to fly with a hard runway!
- Must be fun and challenging to fly both short range FPV and LOS as I intend to use it in both roles
- Must be fast and aerobatic to keep my inner speed freak happy!
- Must use high quality components for reliability
- Must be easy to store and transport
- Must have that special something that gets my heart going and offers me a challenge...
Not asking for much....
So after much thought and research I settled on the Freewing 90mm EDF Eurofighter. It fills almost every criteria except for being easy to store and transport... But I have plans for that! I went with the airframe only version (includes servos and retracts too) so I could install my choice of electronics. And boy it's a pretty big birdy! Around 1.4m long and 0.96m span...
So now as for the setup... Here's what I'm going with
- Wemotech 90mm midifan
- Arc 36-55-2 motor
- Kontronik 80+ HV ESC
- 2x Flightpower 4S 3300mah 30c nano in series for one 8S pack.
- HS-85 servo's for the primary flight controls (elevons and canards)
This is not the normal setup, which would be a 6S 4000ish mah based system. This higher voltage setup does however allow me to run around 3Kg of thrust (well in excess of 1:1) very efficiently with the arc motor, with a max amp pull in the mid 60's. All that with almost no change in weight when compared to stock). I am hoping the kontronik's efficiency at partial loads will also be an asset, but the proof will be in the pudding.... The reliability and load coping ability of its BEC was another big reason for the choice. One of the big drawbacks of EDFs is the short flight times, so I'm doing everything I can to extend that here. I am hoping for a good 5-6 mins of mixed flying which should be sufficient for my needs.
Now, one thing I've learned over the years is that you can't beat low weight when you are trying to get the most out of your airframe... To that end this will be an exercise in trying to maintain a relatively weight-neutral outcome! Since I will primarily be belling landing I will be removing the retracts, a total saving of some 250g I believe - that's a big help already. I can also save a little additional weight by removing the lighting system, and by switching to a single servo canard arrangement (apparently it flies better with canards only in pitch anyway).
So Far I've got the below removed:
Main gears (nose gear is yet to be extracted!) - 144g including screws
LED light controller - 4.g
Drop Tanks - 32g (for the pair)
Pilot - 15g
Seat - 16g
So already up at 211g... Assuming the nose gear is around the same weight as the mains that's another 70g or so bringing me up to 281g saved... then i have some wiring to remove, maybe servos for the gear door and steering although i may leave those in for times that I want the gear. Hoping to get to around 300g before I then start adding weight again!
I must say its a shame I'm not using the landing gear as it looks blooming awesome! Suspension all round and proper struts. Surprisingly light actually given they are fully contained electric retracts and have the full strut leg too.
This is the FPV load out:
- Eagle Tree OSD Pro
- Eagle Tree eLogger v4
- Eagletree Guardian stabilisation unit
- Eagletree Alt v4, ASI v3, GPS v4
- Immersion RC 5.4ghz vTX with CP antenna on TX and RX
- Fat Shark RCV922 camera
- Fat Shark Predator goggles with integrated head tracking
Total weight for the FPV gear comes in at approximately 160g, which is quite incredible when you consider what's there!
Of course nothing is perfect out of the box when you have such a specific goals, so to that end there will be some modding here! The mods will cover 3 main areas:
1 - Durability (specifically for belly landing)
I intend to do some mods to protect the leading edges of the wings and canards, and the belly. The most vulnerable part will be the intake at the font, and this will require some thought. Minimal weight gain is key, and rules out glassing IMO... In addition, to protect the overall finish I will be coating it with a few layers of thinned minwax polycrylic.
2 - FPV gear bays and cockpit
All this "avionics" gear needs to go somewhere, and the cockpit area needs to be brought up to snuff... I will probably be making custom covers for the turtle deck so that most of the equipment can be placed there for good CG balance. I'm going to experiment with vacuum forming I think for this. I may also then make my own canopy replacement if I think it's feasible and within my abilities!
3 - Transportability.
It's a big plane and will be awkward to store or transport in one piece. I will be working on a method of using detachable wings that must be as strong or stronger than the epoxy joint that would normally be used. Inspiration partly comes from an old GWS J10 (also a canard + delta wing design) I used to have which had removable wings.... But I'll be trying to use a better implementation. The trick will be keeping everything aligned and adding minimal weight while I'm at it.
So, that's the plan... We'll see how it works out! It's quite a big undertaking and I won't be rushing along so it may take a while to get it all done. I also intended to have a camera capable of HD recording whilst also providing video out, but there's nothing that fits the size constraints or weight targets. I do have an inside track on an upcoming product that might provide just what I'm looking for, but it won't be available until early summer at best. When it becomes available I'll probably fit that instead of the RCV922.
Please feel free to chirp in with any suggestions along the way, I'm very much open to input and criticism (preferably constructive, but beggars can't be choosers!).
Well done for making it to the end of this post, let's ding dang do it....