Fei Bao Velox Assembly

[Dick Spreadbury]

I was in the market for a quick-build sport model for my Mercury HP and, having had a good look over Sandor Kruise's prototype Velox at the JMAs Long Marston meeting back in March, and being impressed with its flying qualities and it's good looks, I bought a kit from Pete Lancaster at Just Turbines (whom, incidentally, I'd recommend to deal with any time - a very helpful chap).

Quite a bit has been written about the Velox on RCU, and RCJI has carried a kit review article so I don't intend to do a build (or assembly) thread per se, more of a photo record of the assembly with a few comments added to each picture and a few general points elsewhere in support.

To start with, let's have a look at what you get for your hard earned cash, and the quality and finish of the parts...

The Velox is finished in the traditional manner rather than the normal high-quality paint in the mould method, and the Diamond Back version I have is a spectacular looking model. Closer inspection revealed a few local defects...











Plenty of accessories come with the kit. The tank capacity is 2.15 litres...











If you buy the retracts and doors set, you get loads of bits for those too...



The kit comes with Fei Bao retract units, wheels and brakes, and Digitech legs. All good quality stuff but a bit disappointing that one has to shim the leg to compensate for the oversize trunnion hole...a quality control issue that should have been picked up before kit shipment...











Having seen other Chinese built ARFs suffer from poor glue joints, I had a good look at the joints I could see on my model...



All control surfaces come pre-hinged and, without exception, all required re-work to bring the surfaces together properly at their centre-lines and make them good. This kind of defect is inexcusable from a mass-production quality control point of view...and it isn't rocket salad to make up a simple jig in the factory to produce perfectly positioned holes every time...



Servo box/hatch...



Fitting the retracts, legs, etc...











The assembler has to fit the horns to the control surfaces. I found good hard balsa 'backing' material at all horn positions to provide a support and glue key...



It is necessary to trim the lower flap shroud to facilitate full and free movement of the flap. Note the flap horn position - for greater mechanical and geometric advantage)...





Aileron linkage...



The slab tailplane and elevator is heavy...



I like the idea of a cover over the engine - sort of finishes it off nicely and takes away from that 'after thought' impression given by other similar exposed engine models...



...but my Mercury HP wouldn't fit on the moulded rails, and it was about 1/4" too high for the cover to fit - and I wasn't going to leave it off - so I had to modify the rails by adding about 30mm to their length and mod the engine mounts to lower the engine...











I made a 'tea-strainer' FOD guard for my Mercury HP...







Bits and pieces about the installation...



















I initially balanced the model to the instructions on the Digitech website but conflicting information on its 'correct' position lead me to re-balance the model 15mm behind the C/L of the anti-rotation pin. Before anybody comments, I'm aware that the NLG retracts forwards...but it's fairly light and the relatively small difference it made was, for me, a bit of insurance!

...that was two weeks ago - the model's been ready for flight since then but, as is often the case, other things have got in the way of progress. However, all being well, it should fly sometime next week and I'll be back to let you know how it went.

Cheers,

Dick

[M J Namih]

Hi Dick,

I read your Velox review with great interest as I am thinking of getting one. That is how reporting should be. Now I can go ahead knowing the good things about the kits and the faults. In particular the all important non-aligned hinges. Let's hope manufacturers accept the feedback from customers and improve their kits accordingly. Good work.

Moussa
MJN

[Dick Spreadbury]

Thanks Moussa...so far I'm fairly happy with the model and, if it flies well, would recommend it be given close consideration.

Even though it's 'cheap' compared to similar type of models (mind you, £1000+ isn't cheap!) a comparison of build and finish quality would add perspective to this. If you do decide to follow it up, give Pete Lancaster a call at Just Turbines...I found him excellent to deal with.

Having seen several snippets on RCU whereby the thrust line of the engine was refered to, I emailed Digitech for advice. Their response was that, for engines in the Supersport category, raise the front engine mount by 4mm...so I'll try and translate that into degrees and angle my Mercury the same.

Barring unforeseen family committments, and weather allowing, I may go flying this weekend. I'll post how it goes.

Cheers,

Dick

[Dick Spreadbury]

Just for a change, we had sunshine today, albeit with a stiff breeze running at 45 deg to the runway at Wroughton but, with no opportunity to go flying again for at least 3 weeks, took the opportunity to fly my Velox.

Before describing the flight though, three things I should mention:

First, the soft aluminium tongue that protrudes from the wing panels that's used to secure the wing in position, has a 3mm pre-threaded hole in it. Both holes were basically oversize and the threads inadequately formed...both would have stripped with even the lightest of tension applied by the screws. I suspect that this is the result of inexperience on the part of the person who cut the threads (soft aluminium has to be carefully worked if a decent thread is to be achieved) and is another area that Fei-Bao might like to look at. My solution was to cut a slightly larger and coarser thread and, as I only had 4BA avaialable, that's what I used.

Second (and I forgot to mention this before), is that I had to wrap 2 layers of aluminium 'speed' tape around the stbd wing anti-roll pin to tighten up the boom security...play between the boom and pin allowed the boom to move up and down approx 5mm at the T/E fin position. I should add that neither wing had any torsional play at all...everything fitted spot on and was nice and tight...this problem was limited to the stbd boom only.

Finally, I erred on the safe side and added a tad more nose weight to put the CG spot on the middle of the wing anti-roll pin. OK, on with the flying bit...

I set the controls exactly as advised in the Velox manual on the Digitech website and decided against doing anything with the engine thrust line until I saw how the model acted as per the basic build.

Ground handling was good (nice wide track U/C) and the brakes worked very well...holding the model against 1/2 power easily (post flight inspection revealed that I'd flat-spotted both tyres when I braked on landing...the brakes are very good!).

Take-off was normal (about 50 yards from stopped to T/O).

S&L flight at 1/2 power needed some right aileron trim.

At full power, the model climbed noticeably (down-thrust required!).

General handling showed the control throws to suit my feel, so Digitech's advice was good.

The model slowed to a very low speed before stalling. The stall was unusual inasmuch that the model exhibited elevator authority until a very slow speed was reached, at which point it suddenly pitched nose-up violently, lost all airspeed and pitched nose down just as quickly. I think this strange stall is due in part to the lifting effect of the fuselage causing a sudden centre of pressure change...it's nothing to do with the thrust line (as the model was at idle during the tests - I did 3 or 4 just to get familiar with it!). Recovery was OK...just let the nose drop to the vertical and start flying it again when the speed had built up.

Stall with take-off and full flap was the same (but the model was going even slower at the point of stall.

Application of take-off flap pitched it slightly nose down and take-off flap a bit more nose down. Between flighs I mixed in another 3 mm of up elevator movement (at full-flap...proportionally less at T/O flap) which cured this completely.

The Mercury HP gave the Velox plenty of power to run through a nice aerobatic routine (on the second flight) and didn't suck up too much juice at a good flying speed throttle setting, so I shouldn't have to screw about adding extra fuel tanks.

One area of note is that the Velox has very little wetted area and doesn't slow down as quick as you might expect. Together with its very slim side profile, vision (especially when the model is head-on) can be a challenge...I am going to paint the leading edges of the wing a dark colour (probably same red as the wing tips) to try and enhance its visual properties (and maybe get my eyes tested again!).

Landing was OK but I bounced the model both times on landing...my fault entirely, I need to add some expo to soften the elevator a bit...and the Jet 1-A legs worked beautifully.

That's it, a non-event really. I don't think I'll change the CG again until I've got to know the model and its characteristics better (and maybe not even then) but I will experiment and add some down thrust to the engine to try and stop the pitch change with throttle (although, it wasn't a problem coping with). I'll alter the elevator (expo) as mentioned above, and maybe add just a bit more travel to the ailerons. Shake-down checks showed nothing amiss so that was that.

Geoff White's a gem when it comes to general assistance and calling (cheers Geoff) and Paul Lewis is getting better with the camera - here's one he took on the second flight...



I'll not get a chance to fly again for some while but will come back and give my thoughts on quality and value for money when I know a bit more about the Velox's serviceability and reliability...but first impressions are pretty good!

Cheers,

Dick

[Geoff White]

Congrats Dick,

I think once you have it tuned to your taste, you are really going to enjoy it.

Geoff.

[Dick Spreadbury]

Congrats Dick,

I think once you have it tuned to your taste, you are really going to enjoy it.

Geoff.

I think you're right, Geoff.

I wedged the engine mounts to give some downthrust but, with the weather forecast being cr*p, planned for doing lots of other brownie point gathering tasks at home! And so, I sit here now in brilliant sunshine, a nice breeze and pi**ed off that I didn't go flying! British weather...no wonder it's our #1 topic of conversation!

Enjoy Cottesmore...see you in a couple of weeks!

Cheers,

Dick

[Dick Spreadbury]

Finally managed to put a few more flights on my Velox at Scampton over the weekend, and another at Wroughton yesterday.

Having jacked the front of the engine up about 1/4" to give a bit of downthrust (as advised by Sandor of Digitech) the trim change with power disappeared and I had 7 decent aerobatic flights at Scampton. There was a healthy cross-wind blowing at about 10 knots most of the time but it made no difference to the model taking off or landing (apart from my consistently crap landings!) and I was very surprised at how little correction I had to put in against the wind during aerobatics - I suppose the relatively small side area played a big part...all the same, it still has a fair sized keel area - so all in all, I was further impressed with the model.

What has surprised me, though, is how much power I need to keep on to overcome the drag presented by the big flaps - they're very effective and I'm thinking about maybe reducing their travel somewhat to lessen their effect and also make a bit more elevator control available (because the pre-set compensation up elevator would also be reduced).

I didn't try the stall again as it was well breezy and, therefore, would give a false indication of model speed at the stall compared to still coditions.

Slightly different outcome to the one flight I had yesterday at Wroughton when, having enjoyed a decent flight, my depth perception chip went unserviceable and I cocked up the landing causing the port wing to catch the long grass at the edge of the runway resulting in the model doing a horizontal 360 that looked far worse than it actually was (phew!). Other than a slight ding to the leading edge of the port wing (Wiltshire grass is tough stuff!) a snapped nose-leg pin due to excessive side-load and a slightly bruised ego, no harm was done!

The point of mentioning this is that it proved the Velox capable of absorbing some punishment - it is a very robust design.

One thing I will need to do eventually, is to change tyres. No other reason than the very effective brakes supplied with the kit do their job as advertised...I just need to change the settings on my Jetronics brake valve to stop me flat-spotting the tyres! I checked with Digitech today and they have a load of tyres on order, and delivery should be soon.

Finally, the Jet 1A legs are working well at cushioning my carrier-deck style landings but I think a stronger spring would help. Digitech again advised that stronger springs are available.

OK then, I've still only got 9 flights on my Velox, which is nowhere near enough to form a full picture of it, but it's plenty to get that initial 'I like / don't like it' impression. What I can say at this point is that I do like it, I look forward to flying it and have yet to find anything really adverse with it. It's easy to transport (just take the wings off and leave the booms/tailplane on) simple to operate, easy to fly, not too difficult to see in the sky (especially now that I've added the leading edge colour I spoke about earlier), performs large, smooth aerobatics, will fly safely down to a low speed and just plain 'feels' nice.

So far, I'm pleased with it...I'll keep you informed.

Cheers,

Dick

PS...would have put some pics of it in at Scampton but my photographer there is a far better (100 Sqn Hawk) pilot than he is photographer!

[Geoff White]

No idea who you are referring to Dick

Geoff otherwise known as 100 Sqn pilot

[Dick Spreadbury]

No idea who you are referring to Dick :D

Geoff otherwise known as 100 Sqn pilot

LOL! See you Thurs PM Geoff...I'll fly the Parky whilst you do the pics!

Following on from my last post, I forgot to mention that one other thing came to light yesterday: Both the plastic conduits for the steering cables overcame the cyano I put on them initially and slid in their bulkhead holes, thus allowing the cables to go slack.

As cyano doesn't do much with plastic, I got around the problem by inserting a piece of 1/2" dowell (3/8" long) cut to provide a flat seat to glue against the bulkhead and the radius providing support against the conduit, preventing it from moving and slipping through the holes.

Let me know if that doesn't make sense and I'll take a picture to explain it better!

Dick

[Kevin Watson]

Hi

Seen one of these flying and it looked a handfull on landing almost like a blanked elevator response.

What throws have you got set up? - especially with the flap deployed


How do you rate the slow speed characteristics Dick?

To look at it is sleek and smart, flying qualities? A personal unbiased view here please?

You can PM me if you prefer

Thanks

[Dick Spreadbury]

Kevin,

I only ever give personal unbiased opinions!

I was directed to your pm before I got here so replied to it (you're more than welcome to reproduce it here if you want).

Rgds,

Dick

[Dick Spreadbury]

Kevin,

Further to the info in the PM, having flown the model quite a lot now and having moved the CG back 5mm (now 5mm aft of the C/L of the wing anti-rotation pin), reduced the full-flap travel and corresponding elevator compensation trim, I flew the model twice again yesterday to check out the latest changes and am happy with how it feels and performs. The set-up I have settled on is:

CG - 5mm aft of the C/L of the wing anti-rotation pin
Aileron movement - 14mm each way (measured at the tip - no expo...gives the very soft aileron I like)
Elevator Movement - 30mm each way (12% expo)
Rudder movement - 25mm each way (measured at the top - no expo)
Flap travel (measured at outb'd flap/inb'd aileron position):

Take-off: 20mm with 9mm up elevator trim mixed in
Full-flap: 35mm with 11mm elevator trim mixed in

(so that means there's 20mm up elevator trim required with full flap travel)

As mentioned earlier, I reduced the length of the noseleg by 5/8" (which stiffened the spring somewhat) to give the model a better sit on the ground, and to help reduce the onset of bouncing on landing.

The only thing now left for me to do is to make arrangements to put more fuel on board...having got more used to the model and using top end throttle more, I'm not getting the flight duration I need with my thirsty Mercury HP on the back (plenty of power, by the way...a good engine for the airframe). So, we'll see what happens there.

With regard to your concern about some guys losing control control of their Velox at slow speed; yes, this model does exhibit unusual stall characteristics due, I believe, to the rapid change in CP towards the stall caused by the fuselage chines and turbulence/airflow blanking of the T/P at high AOA. Putting this into perspective, though, every model has a point at which it stalls, and some, like Mick Reeves' Javlein, suffer from tailplane blanking at certain attitudes. The answer's quite simple - when you know the model's characteristics and limitations, stay away from the 'danger zone'! My Velox slows to an acceptable speed for landing and I'm happy with the way it performs.

Any other questions, pse let me know.

Cheers,

Dick

[Kevin Watson]

Many thanks Dick

What thrust does your turbine produce?

It says up to 160 on the blurb for the velox but that is overkill and I suspect 24 lbs is ample , maybe even less eg Wren SS

I will let you know how I get on and many thanks

I will respond

Keep me updated and happly landings

Kevin

[Julian Swiestowski]

Dick

With your AMT Mercury HP and Velox combo,

What flight duration are you looking for and what tank capacity will you upgrade to, 3 litres ?

AMT spec says 290g/minute @ 88N at full thrust.

I have a spare Mercury and this info would be very useful for any next project.

[Dick Spreadbury]

Dick

With your AMT Mercury HP and Velox combo,

What flight duration are you looking for and what tank capacity will you upgrade to, 3 litres ?

AMT spec says 290g/minute @ 88N at full thrust.

I have a spare Mercury and this info would be very useful for any next project.

Julian,

3 litres would be good but I have to see how I can get there first. 4 options come to mind...

One is to see if I can get a 3 litre pop bottle to sit in the fuse somehow (there's some room in the U/C bay I might be able to get a bottle to sit through the back bulkhead and into there)...

...or make another tank to use some more of the space available in the centre fuse (problem there could be getting the tank in through the cockpit opening)...

...or move the ECU and pump, etc and insert a couple of inches into the existing tank...

...or add a functional centre-line tank...!

Once that's done, I'll be content!

Cheers,

Dick