Xantos

Hi Didier,
Im at the primer stage on my Viper , just filled up the seam line with putty and I'm ready to spray primer.
Yes , the Engine mounting and the flap servo mounting is the most fiddly part of the build.
You need very long and thin fingers , dont know what Thomas Hochman was thinking.
Yes a 90deg drive is what i would use for engine mounting
Xantos

Didier

My god, those German guys knows how to design airplanes and there quality is second to none but construction enginering and to perform maintenance later on? Hmmmmmmm. [&:]
Damn, also no long piano fingers, guess I ask my girlfriend to install the flap servo.

c_makhija

Its not that bad as Xantos made it sound. I drilled the holes for the flap servo with a pinvice, no motor tool i had would go in there. A little patience is required with a sharp drill.

Chaitanya.

gruntled

The website says 6 kg turbine but you guys are talking about much much bigger. Where did they get 6 kg from?

Xantos

We've flown the Viper with a P80 and found it a little underpowered, lacked in the verticals changed over to a P120 and it flies great .
Also we fly at avg temp of 35 deg C so we do loose some thrust.
Xantos

Ragz

bombay boys, cmon get off your *****es and get that viper in the air...    

Didier

Hey Guys.

This beauty is finally arrived! :-)
The molding quality is really good, the best I've seen so far.
Anyway, due to the very thin wing a special retract mechanism is required. (air cylinder pointed outside wing)
What do you think guys of the Airtech landing gear Tomahawk provides?
Did you use the recommended elevator servo and is it enough when flying with a P-120SE?
Thanks!

consoleworld

Hi Didier

for the standard engine booster 90 or simiular i think the 4-6 kg servo is ok . (in my i install JR DS3421 Digital Mini MG Servo )
but if you use overpower engine p120 you need sure more kg in elevator , but i see is very thin the stabilazer . ( problem to put standard servos ).

i have the boomerang elan , the jet is 10.5 kg and with with 8 kg turbine thrust run 250 km . ( no need more power )

in my viper i fiit the evojet booster 90 . i think no need more power for 9-11 kg empty viper jet.

the airtech landing gear is a good german quality .

my viper shipping time is on end of february

now please Didier if you can tell me some information for the wing place for retract ,
tell me the measurements from attach pictures A-B-C-D-E in mm.
i have the Jet-1a retract to fitting in my viper , but if dont fit i take that from Thomas .

thank you

Didier

Hey Christian.
I will measure it for you tomorrow.

Regards Didier

Xantos

Hi Didier,
The Airtech gear is really good !
It is very robust will take a lot of abuse and probably is better than most others on the market, I wouldnt try anything else -these are a drop in fit.
You might have to cut a little with a dremel tool to get the frames in but once in place it fits perfectly.
I've used the JR 3421s as well and they are sufficient even for a 120size engine - Im using the same in my bandit
The only gripe I have is the stab and wing tubes.
These tubes slide into fiberglass outers moulded in the fuselage , the fit is too tight and it takes a lot of careful sanding to get the tubes to slide in freely in the fuse as well as the wings and stabs .
I had to spend too much time sanding the insides of these tube with very fine sandpaper so that the wings and the stabs would slide on and off easily.
Tomahawk should have used phenolic outer tubes instead.
Xantos

consoleworld

ok. Didier

i wait !!!

Didier

Xantos:
Thanks for your info about servo choice and gear.
The wingtube is a perfect fit into the wing and fuselage.
The stab tubes is like yours, needs a sanding job.
If I can find, I will replace the stock alu tubes (especially the stab tubes) for carbon ones to loose some weight.

Christian:
Here are the measurement you asked for:
The letter code is the code in your pictures.
A= 45mm
A1= 35mm (This is the other side from A, trailing edge side)
B= 31mm
C= 34mm
D= 215mm
D1= 260mm (This is the total length from edge to edge)
E= 44mm
F= 90mm (This is the diameter of the wheel hole in the wing

Didier

Also some weight info:

-Fuselage inc canopy frame: 1525 gram
-R wing 610 gram
-L wing 606 gram
-Central fins 62 gram
-Fuel tank 140 gram
-L stab 170 gram
-R stab 166 gram
-Canopy glass 270 gram (At least 50% have to be cut away to get in proper shape)
-Thustpipe 426 gram (This is complete inc inner-outer tube and alu bellmouth)
-Alu wingtube 244 gram
-Stab tubes 94 gram
-loose assembly parts 190 gram (This includes intakes, servo connections etc)

Total weight: 4503 gram.
This is very light as I remember the weight of a Flash and Boomerang where a little over 5 kilo out from the box.

digitech

My Feedback: (10)

Jet-1a wont fit without shimming the retract
Behotec will do the job , but needs a inforcement carbon plate to make sure the screws will have enough place to secure.
since both Jet-1a and behotec are relative small.
Pro-lynx will also fit , the oleo,s are pretty long but not impossible.
Still to make a set we need the model here to make sure we got it right.
i ordered also one

consoleworld

Thank you Didier for the measurement
( i think my Jet-1A retract its ok with some extra work . )

here is some parts for my baby :

5 servos hitec 7985 mg 12 kg for aile-flap-rudd total weight 300 gr.
2 servos JR 3421 mg 6 kg for elevator total weight 63 gr.
1 servo hitec 5645 mg 10 kg for nose gear total weight 60 gr.
1 turbine evo jet 90 9 kg thrust weight only the turbine 950 gr. ( full weight is 1400 with all accessories inc. battery )
1 powerbox competition with switch total weight 136 gr.
1 full set landing gear JET-1A total weight 1030 gr
1 receiver JR plus 3 remote receivers total weight 30 gr.
2 lipo battery 7.4v 20c 2250 mAh total weight 240 gr.
1 air accessories battle tank , valves , tubing etc. total weight 200 gr.
1 airtrap bvm total weight 60 gr.
various accessories 200 gr.

total weight for all this things is 3720 plus the viper weight 4503 total only 8.2 kg .

dont forget the painting 400-800 gr.

if the total empty viper weight is 9-10 kg its really verry good jet.

Didier

It is possible to install a standard servo in to the horizontal stab. (JR8411)
Very minor adjusment with a dremel needed.
Only it will be twice the weight compared to the JR3421.
Still did not decide. I'm very interrested if this will give me C.G. problems because I also will install a heavier turbine (P-120SE)

consoleworld

thats is good news Didier .

the jr 3421 is 32 gr. ( i dont take yet i prefer to add more kg to elevator 10-12 kg but is standard size that servos . )

keep us informed .

Xantos

Hi Didier,
uploading some pics for you
I dont think the 8411 will fit as the tailplane half is designed such that a 3421 servo is screwed on from the bottom and only the top of the servo and arm exit on the other side of the rib on which it is mounted
Ive uploaded some pics of the flap servo install and the retract install
Xantos

Didier

Looking good Xantos, keep the pictures coming!
The manual says the C.G. is at the middle of the wingtube but is that not to much forward?
What C.G. are your friends Viper using?


I'm convinced the JR8311/8411 will fit in the stab.
In this picture I just drop in the JR8311 (8411 with nylon gear) in to the stab without doing anything.
Only the opening in the wooden former needs to be enlarged.
Ayway, I go for this option and replace the alumium stab tubes with carbon ones to compensate the servo weight difference.

Xantos

Didier
Thomas says the model tends to be tail heavy thats why he has a fairly large component tray in front
All batteries , pump ECU etc go up front.
We have only one viper flying here so far and this on is balanced as per the recommended CG and is a pleasure to fly.
Bear in mind that this one has lights etc and the electric retracts , so there are 2 additional 2500mA lipos so is a little heavier.
Xantos

Didier

Hey Xantos.

Do you have anymore pictures about the turbine installation and thrust tube?
I see there is a offset on the mounting clamps of the thrust tube but have no idea which is the upper and lower part?

consoleworld

Hi Didier

finally you are install the standard size servos in elevator ?

Xantos

Hi Didier,
There are no mounting clamps that come with the thrust tube , I made up those bracket from scrap aluminium right angle channel I had lying around
Its fairly simple you have to push the thrust tube in and then place your turbine on the rails and eyeball it from the rear to check if your turbine is centered in the vertical axis
Adjust the tailpipe from the front to the correct height and drill holes for the bracket. the 2 brackets screw on to the rear former.
Similarly adjust the turbine in the lateral axis until it is centered and mark holes for the mounting with a pin vise or similar tool.
Xantos

Xantos

Hi Didier,
I did not get the wood parts for securing the Fuel tank in the Fuse, if you have received these wood parts can you please take an outline of these parts on paper and email me a scanned copy so I could cut out the parts from Ply.
Thanks
Xantos

Didier

Xantos.
Will do the scanning 4 you in the afternoon.
Please send your email adres via PM.
I didnt get the turbine installation rails I guess.
Do you have picures or if possible, make a scan as well?
Thanks