Beachy1968

Sound advice Mark. I will definitely do the first few flights with them on. Are you off to Merryfield tomorrow?

Aussie1

This was a post that I did last year on adding lights. It actually worked really well, but certainly not as nice as this new example from Beachy!
Just click on the post link to show the pictures of the install.

Beachy1968

Hi Aussie1

It was in fact that very post of yours which inspired me to fit lights for my build.I got a bit carried away though and went for the full Christmas tree effect as can be seen below!

https://www.youtube.com/watch?v=BDtrB5LhrI8

Aussie1

Beachy, that will look amazing in the air, especially on those overcast days that you NEVER get in England!!

Beachy1968

LOL! Too right about the overcast days. It's a Bank Holiday here this weekend so of course that means rain and wind as well!

I have an Avonds F-16 which is a great model, but seeing as it's painted grey it is very stressful to fly as I just can't see it. So that's the next project, break out the spray gun....

Mark Vandervelden

Good Morning B.S.
I'm sorry to say that since fitting a full by-pass to the Viper along with a few other little mods its been sitting fully rigged on a stand in the workshop for ages.
I really should get out and fly it along with my other toys but between the weather, work and building airframes for others I just don't get the chance.
So no mystery im afraid, no special plumbing or valves just a confidence booster in so much as the Viper holds air for a very long time

Beachy1968

Well, it's finally finished! Now all that remains is the scary bit; the maiden.....

Vettster

Superb build Beachy. I hope you all the best on the maiden of your first turbine

Trevor

Vettster

Im just waiting for my gear to arrive and then I will start my build. I bought a used one that had a bad landing but has been fixed professionally by my good buddy who spent his entire career as a fiberglass layup person..AND.. He flys turbines too

fredo

I can't wait for mine to arrive. It's been a really long, long wait. Hopefully, TNT guys will surprise me on Monday.

Beachy1968

Finally got the maiden out of the way yesterday. What a lovely flying little jet!

I was beginning to think the omens were against me as I found a bunch of little snags which meant it took about an hour to go through my pre-maiden check list. One was entirely my own fault though. I had rearranged the pressure side fuel piping a bit the night before so there was a load of air in the fuel line. The engine often deals with this on startup so I didn't prime it properly as I should have. This time, however, the air was too much and once it had pumped it all out the ECU had turned the burner off so it just pumped fuel into the engine. After seeing this and feeling suitably foolish I had to take the turbine out and tip the fuel out of the front end. Once drained I was ready to go again, but I didn't notice I had in the process allowed fuel onto the nose of the compressor. Result; starter motor slipped on the compressor and couldn't spin it up. So, turbine out again, clean, back in again...I swear the nerves associated with a maiden flight just seems to turn me into a complete incompetent idiot!

Anyway when I did eventually fly I took off with no flap so I could test them at height. T/O flap resulted in a continual slight roll to the left despite me having ensured both flaps came down the same amount. Strange, never experienced that before. I'm sure just a very small tweak up or down on one side will fix that. I expected the unwanted roll to be worse with landing flap so I landed with just T/O flap. Despite being a little faster than ideal, it was just about the most straightforward jet landing I've experienced. Great model. Looking forward to having another go at the weekend.

p.s. In the end I did the maiden without the winglets. I was going to put them on but decided against it because of the rather dodgy way they are attached. The supplied retaining screws should screw into one of the two mounting posts in the win let but the holes are so badly drilled and tapped that the screw could just be pulled out by hand. I've encountered very few examples of iffy Chinese quality with this model but this is one bad example. I didn't fancy losing one winglet so I left them off. Orientation wasn't a problem and I do think it looks better without them anyway (real Vipers don't have them).

essyou35

My Feedback: (11)

Really wierd with the flap roll issue. I use some crow in mine so I am not sure if that somehow corrects it or not. But I never experienced it.

Congrats, it is a very easy to fly jet as you have found. Knife edge is great too.

fredo

Hi guys, finally got my Viper�� and must say, it looks really nice. Mine is in Brit colour and I have "pro-wired version", so most of the gear is installed, which is great for a first timer. My turbine will be K100g.
Just a couple of questions. I'm going to use HV servos Spectrum 6150 all around but not quite sure about what to use on flaps and nose gear stearing. I'm thinking HV analog servos would be OK. What do you use?
Also, I wouldn't mind using stock hardware but I noticed ball link bolts have some weird size, looks like 2.5mm. Servo arms I can get are either 3mm or 4/40 so it doesn't fit to a standard arm. Did you end up using it or ditched it?
Thanks

Jeremy_D

I ended up using standard sullivan clevis on my setup. I only used the ball link on the steering and used a nylon arm. I know DA just got some m2 alloy arms that you might be able to thread to the JL bolts.

http://www.desertaircraft.com.au/sho...servo-arm.html

fredo

Thanks Jeremy, I already have servo arms with 3mm holes in it, so I think I will end up using them. Just need to buy right size ball links.

M3Baker

Good luck with the viper. I love mine.

Beachy1968

Hi Fredo

I used the ball links supplied in the kit but only on one end. On the servo end I used a clevis. The reason I did this is that it's the easiest way to attach to the servo arm at the correct distance from the centre. I found that on all the controls the best mechanical setup (which gives the correct control throws whilst using all the travel and resolution of the servo) needs the servo arms to be pretty short so you need to use an arm hole which is below the top of the servo hatch. Because the ball links are quite large you will find that if you want to use them to attach to the servo arm you will either have to substantially widen the slot in the servo hatch cover to use a hole close enough to the centre or use a hole which is further out and put up with your servos not using all their travel and resolution and therefore not performing at their best. A clevis, on the other hand, is narrow enough to fit in the correct holes and fit in the hatch slot with little or no widening, as can be seen in the picture.

Regarding servos, I used digital servos on all surfaces including flaps. Although accuracy/centering may not be such an issue with flaps, holding power is. One main advantage of digital servos compared to analogue is their generally much better ability to hold a position. Flaps are used at big deflections and therefore I would imagine can have large aerodynamic forces acting on them, so a servo with good holding power is important.

Jason R.

Looks awesome Beachy, i just ordered a viper 2 days ago. Looking very forward to its arrival with factory lights installed also. Good luck with the maiden..

fredo

Thanks Beachy, I'll think about using them. I understand mechanical advantage and having pivot point close to the centre but still I 'm a bit worried about slop development later on. In my opinion, ball links are pretty bullet proof. I always used them on all my IMAC planes. The only enemy I can see is flutter.

Beachy1968

Good point about the slop, I'll keep an eye on that. There's no perfect way, but as I spent money on good servos I want to get full advantage of their full power and resolution. I would imagine that on an IMAC plane because of the large throws and low speed of the model resolution is not as critical as on a jet where the vast majority of flying is done with only very small control surface movements.

Beachy1968

Spent a great morning at Westonzoyland today. Got the Viper trimmed out and starting to get the feel for it. Loving it so far....

A few pics from today taken by my good buddy Simon....

Jason R.

Congratulations it looks like it flies well. Mine should arrive in less than 2 weeks. Can't wait..

keweiliang

Congratulations

Jgwright

Just got back from then flying field. I recently bought a second hand Viperjet that had only a handful of flights. Unfortunately the owner had cut the ducts out and my first task was to reinstall them. This is definitely not as easy as cutting them out! They were strengthened in places with fibreglass bandage and the joints were held in place with duct tape while I joined the inside of the Y shape where it was easy to get at with fibreglass tape. This left the outside of the Y where the had been cut. I joined with this Proskin. The Proskin held the parts nicely together and aligned.

I used the servos that were in the plane which were 20 Kg Hobbyking servos in the flaps and ailerons. The rudder was a Savox servo and a Hitech in the elevator.
The wing surfaces did feel a little 'spongy' but in the air seemed ok.

The engine is a very old Simjet that I bought some months ago that needed some TLC. I fitted new bearings and balanced it. It came with a modern Xicoy ECU but did not have a starter fitted. I soon fitted one and got the autostart working well. Tests at home seems fine.

After a little delay in tweaking the settings on the ECU we got the engine running and went for a takeoff. Dave Wilde was my pilot as usual. We flew off grass at Raydon and it was soon airborne. It immediately became apparent that this was one very clean airframe and even at low throttle settings was pretty quick. I am not quite sure of the power of the Simjet but reckon it is 20lbs or so. The plane weighs 23 lbs dry and it flew most of the time on 1/2 throttle. It seems that anything much more is severely overpowering the airframe. The maiden was spent checking pitch changes deploying flaps and trim min out. The send flight was a fuller routine and we were delighted with it. The great thing about using a old-timer engine is that they rev a bit lower and have less throughput so are a lot quieter. I was amazed at the fuel consumption on both flights we only used 2 litres in 7 minutes flying. Just goes to show how you can get performance by conserving energy in the airframe by not slowing too much in turns and nice smooth large manoeuvres. The second landing was nice and slow with no bounce. This is a great plane and everything that we hoped. It can be thoroughly recommended to everyone. This is a great thread with lots of info. I would only add that I would not cut out the intakes. The plane flies great on the stock tanks with Cg at 35mm behind the centre of the spar.

Jgwright

One thing I should add we had some crow on the set up. Mix was put in for up ailerons about 5mm up with flaps 65mm down and elevator 5mm down. 30% expo on elevator and aileron.


John