RE: ViperJet Mk2 - control throws and tips?
 

I just put the fairings on with the wings. They are so delicate that if made permanent to the wing or the fuse they would be junk in no time. You can add a bit of foam saddle tape if you think they are to loose. At 199.99MPH sandwiched fit they present no problems in now 9 galllons of use.

RE: ViperJet Mk2 - control throws and tips?
 

and you still get a nice close fit to the fuse like that?

RE: ViperJet Mk2 - control throws and tips?
 

Well, It fit well enough that I doubt most people would even know its a seperate piece and it does not rattle. Its possible you could slide a business card in between the fuse and fairing at most. but the center portion is keyed in to the recess so its not going anywhere, its strictly an appearance item and possibly increased speed but I see it as non structural.

http://image.rcuniverse.com/gallery/...1/lg-59233.jpg


Heres some real proof of complete throws in action, everything can be seen as this is a nose wheel high 3 point stall touchdown with max elevator deflection. I am amazed that at full speed and low speed the elevator has a smooth linear response with no mushy or dead spots or pitchyness at high speeds. You can see, crow, full flaps and full elevator. taken at Kentucky Jets this past weekend.

http://image.rcuniverse.com/gallery/...1/lg-59229.jpg

RE: ViperJet Mk2 - control throws and tips?
 

Same Here, I had a little over one pound of lead in the nose. I ripped out the servos in the nose, moved them all forward, did the same with the fuel pump and ECU. While I was added, I installed the light kit and that also included a 9Volt battery, not it balances perfect with no weight required.

Turbulence

RE: ViperJet Mk2 - control throws and tips?
 

Nice photos c/f, good landing. Good idea Turbulence, light kit will add more weight up front.

RE: ViperJet Mk2 - control throws and tips?
 

The viperjet has finally had its maiden flight, and two others very successfully thanks to the help on this thread thanks alot. In the air its gorgeous, the tail pipe has an especially nice sound at low throttle it just purrs past on low slow passes, even lower and slower with half flap, very nice. With a P120 vertical climbs are no problem, and with full throws as suggested fast rolls while climbing also no problem.

BVM Easy airs – need to be recessed into wing or get in the way of the fuel tanks just inside the fuselage. Also don’t forget to fit check valves to make setup easier otherwise you need a completely assembled aircraft to make the pneumatics work.

Undercarriage – I fly off grass, which is pretty hard on landing gear and mounts. On the third flight one oleo loosened and twisted at the middle of the landing run out, the model skewed to one side pulling off both wheels (the circlips will not hold even low speed sideways force) causing the outward skewed side to dig in the grass and damage the wing mounts and skin a little. Haven’t worked a solution to this yet but im guessing it needs a lot of tightening on grass and liberal use of loctite (and perhaps softer wheels to absorb vibration better).

Throws – the Cermark throws are way under and give you very soft authority with the model. I used Tam’s recommended throws and its just right, with a tiny amount of expo 20-40%. As below:
Aielrons 1.75" travel total (45mm). 40% expo.
Elevator 1.75" travel total (45mm). 0 expo.
Rudder 2" travel total (51mm). 40% expo.
Flaps : Half flap 3/4". Full flaps 1.5". It will stand more than this even… (19mm, 38mm). With delay, on futaba 98% channel delay.
Crow ailerons 3/8" up. (10mm)


CoG – The model comes out very tail heavy with a P120 engine mounted as forward as possible with provided bypass and tail pipe. So, plan on putting all nicads as big as you can get as far forward as possible, mine are right ion the point of the nose cone. Also worth fitting the standard cockpit and detailed pilots for another couple of pounds of nose weight. I added 1lb and a half of lead to the nose to get it to balance at the 200mm mark (mid way between the 195-210 limits in the Cermark instructions). However, in the first flight the model needed full up trim available to stay level so it was way nose heavy imo. I took half a pound back out again and it flys much better.

Flaps – this model will stand for a lot of flap throw and slow down nicely while remaining stable. Tam’s flap throws are far better than the Cermark instructions. However I found it needed almost no trim with full flap to fly a nice glide slope. With the flap trim suggested it pitches down too much and isn’t on good trim for a nice light landing. I think it will stand for even more flap than Tam suggests, I will continue experimenting. The ideal max flap should theoretically be about 60-70deg down, at present its only about 45-50deg. Take off flap isn’t given anywhere, it seems to work best with about 15deg.

Crow – crow works great as Tam suggested, very little loss of roll authority. On a P120 it cruises nicely with full crow on about quarter throttle.

Flutter – used mostly ball joints on servo linkage and the provided surface horns that put the leverage in the servos favour well away from the servo hinge point. I used HiTec 5245’s on the elevator, a JR DS161 on the rudder, two JR DS8411 on ailerons and two Futaba 9151 on flaps (as I had them lying around). Full power max speed passes (unrestricted and no speed limiter) where no problem, there was no flutter. The aircraft stayed nice and crisp in manouveres.

As a side note, the wings are very very heavy. Much heavier than my Kingcat wings that in theory take more weight/stress and I cant work out why its necessary. The models weight and slightly rough seams are the only criticisms id have of this jet its otherwise fantastic!

RE: ViperJet Mk2 - control throws and tips?
 

CONGRATULATIONS on your maiden

Might take a look at some Intairco Axles. I had one wheel pop off because of the C Clip as well and opted to use the Intairco Axles on the wheels since those eliminated the use of the C Clip.

Turbulence

RE: ViperJet Mk2 - control throws and tips?
 

I use robart retracts and struts with BVM wheels and brakes. All mounted in stock wing as provided.

I always use the axle head button to the wheel side then file a flat for axle to strut set screw. I also use a small shim of plastic (ie. JR heli control movement linkage shims) one for the wheel to button head and one for wheel to brake disc to insure no metal to metal rotation wear.

RE: ViperJet Mk2 - control throws and tips?
 

ahh yes, im using the Tam retracts and intairco wheels. They are a bit different. Though actually the Robarts may be better on grass so ill bear that in mind. Which Robarts are they?

RE: ViperJet Mk2 - control throws and tips?
 

I got flights #4, 5, and 6 on the Viperjet today at a local fly-in---What a sweetheart of a plane...Made me look so good I won the "Best Flight" award!!!.....The Tam smoke system helped me look good, too. Here are a few shots of my Viperjet along with some of my buddies planes. The Viperjet had NO problem handling the 575' X 40' runway landing in 1/2 the length on average. Top speed was good too (unresticted P-120) with NO hint of any flutter issues as I went waaaaaay overkill on the servos...A VERY nice flyer!!! :D


Kevin

RE: ViperJet Mk2 - control throws and tips?
 

Pics won't load now---[:'(]

Kevin

RE: ViperJet Mk2 - control throws and tips?
 

Congratulations Kevin.

Yes, those darn Viperjets fly so good they make the owners go from good pilot to !!!you are the man now!!! pilot, I know, mine did it to me. :) :).

Please post the pictures if you can.

RE: ViperJet Mk2 - control throws and tips?
 

Let's try the pics again...Looks like RCU is up to full speed again!!!


Kevin

RE: ViperJet Mk2 - control throws and tips?
 

Kevin,

I can totally concur. I already put 10 gallons thru mine in 3 weeks, its just that much fun. My Pegasus SP is boogieing straight and level around 184MPH per Eagle Tree. Landings are around 40MPH full stall. Landing pattern easily under 60MPH.

As for Flutter, not sure if servos are the only answer. No hint of flutter using JRDS3421MG on all surfaces except flaps.

My servos are mounted solid in the composite TAM mounts, using c/f to lock into both skin surfaces, Using 5/8" on arm side and 1" on horn side for mechanical advantage. NO hint of flutter either.

This jet flies so locked in on rails and light on the sticks I'm getting some incredible slow rolls and two point rolls with inverted positions on the deck 20' high......


With all the bad press I was really nervous about this one, yet its now proving to be the most exciting Jet I fly out of a hangar of 6.


My home field is 25'X500' and I only use half of it on landing....


Kevin,

Earlier in the thread you had some setup issues on controls. What did you do to resolve them??

RE: ViperJet Mk2 - control throws and tips?
 

c/f yeh control throws resolved, the ones in Cermark instructions are way to low as per my last message post the maiden flight. With the TAM higher rates in its just ice, for eg i ran out of elevator for flare on first landing using low Cermark rates, clicked in hi tam rates and was fine. Incidentally CoG i think is also too far forward, towards the forward end of the limit i needed 1.5lbs of lead in the nose but full up ele trim in flight to maintain level attitude. So have gone to rear most CoG point and taken half a pound of lead out, flys just right.

RE: ViperJet Mk2 - control throws and tips?
 

C/F---

C/G issues and a brain fart on my behalf....I set up the expo reversed from what it is supposed to be...I almost didn't bring her back on the maiden.

I then put too much weight in the nose to compensate for the C/G issue. I then removed some weight and now she is perfect. It's hard to set up the proper C/G without making up a jig of some kind...

Anyway---All is well and this plane flies great!!!

Kevin

RE: ViperJet Mk2 - control throws and tips?
 

Very happy for you guys.

The Viperjet is truly great flying machine, you just have to give her a chance ( with the right setup ) to prove it and here it is, Kevin, c/f, amjflyer and my self have been very successful with it.

RE: ViperJet Mk2 - control throws and tips?
 

You hit the nail on the head!!!

I flew flight #7 today from a grass strip---No issues...Performed some extended inverted flying as well as knife edge flight---This baby will knife edge from coast to coast!!!! You will need to add in a little aileron to counter the slight rudder roll coupling and a little down elevator as it slightly pulls to the canopy. The counter inputs are so slight I wouldn't even bother to try to mix them out... [sm=thumbup.gif]----Point rolls are effortless...Did I mention that this baby flies great!!!:D

Kevin

RE: ViperJet Mk2 - control throws and tips?
 

This is great info guys, thanks for this thread...

RE: ViperJet Mk2 - control throws and tips?
 

Does anyone know the lenght of the struts? Mains and nose please! 630 retracts?

Joe

RE: ViperJet Mk2 - control throws and tips?
 

Kevin was the last to do this modification on the struts, he should be able to give the specs.

RE: ViperJet Mk2 - control throws and tips?
 

My set-up is a hodge-podge collection of parts---It's easier to explain over a phone conversation than for me to type it all out as I'm a hunt and peck typist!!! [:@]---

Joe, I'll PM you my cell phone # and we can talk.

Kevin

RE: ViperJet Mk2 - control throws and tips?
 

Well, after 2 years in the making I have no clue what robart gear I used but the struts are 1/2". They are mounted in original pocket well as is. The strut inner/outer pieces where cut to size to fit.

The main retract was moved as far out as possible to still allow for mounting into wood rails. You can see skin enlarged towards root.

BVM wheels were 2 3/4" used so treads where flat, If new they will fit snug against well for a few landings at that diameter.

http://image.rcuniverse.com/gallery/...1/lg-60452.jpg

http://image.rcuniverse.com/gallery/...1/lg-60454.jpg

RE: ViperJet Mk2 - control throws and tips?
 

I think Robart 630s are used by others, but not absolutely sure. Im using the Tam HD retracts with Intairco wheels. They are very good, very substantial, rather heavy, but as noted above you need to be a bit careful on grass that sideways forces dont pop off the circlip and you loose a wheel at speed, *crunch*.

RE: ViperJet Mk2 - control throws and tips?
 

If you go with Robart gear, the lenght of the struts is determinated after installing the retract and by centering the wheel at he wheel bay.
I use 7/16" dia struts, but will try 1/2" next time.
Good luck,
MS