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JET LEGEND VIPER BUILD THREAD

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Old 01-28-2013, 01:10 AM
  #376
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Default RE: JET LEGEND VIPER BUILD THREAD

I can land it at walking pace on the numbers, it's the easiest model to land I've ever had.
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Old 01-28-2013, 01:13 AM
  #377
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Default RE: JET LEGEND VIPER BUILD THREAD

Hello,

look at my pics in post 210.
The Viper flies out of the box, but with the fuel more to the rear, you dont need to trim the elevator during flight.
For normal funflights it should be okay, but if you want to fly a special program (for jet acro master) it is better with the new tank position.

Christian
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Old 01-28-2013, 03:47 AM
  #378
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Default RE: JET LEGEND VIPER BUILD THREAD

Hey Jeremy,

Trying to upload pic as promised but RCU not playing ball at the moment, I'll try later, pm me your email addy if you like.

Gary.
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Old 01-28-2013, 03:58 AM
  #379
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Pm sent, thanks Gary
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Old 01-28-2013, 05:00 AM
  #380
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Default RE: JET LEGEND VIPER BUILD THREAD

Hi Christian,
Had a look at your post 210 ,thats exactly how Iwas thinking of installing a tank,What tank did you use ,is it a dubro.
what distance is best to mount a merlin 100 from the bellmouth.
Cheers
Chris
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Old 01-28-2013, 05:01 AM
  #381
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Default RE: JET LEGEND VIPER BUILD THREAD


Hi All
The Viper flys very well straight out of the box and its a testament to its design that it can cope with such a large CG change but all or any improvements to any airframe have to be a good thing?
Its really not a big modification to utilise the already available tanks in a different way and it definitely makes a big improvement for both takeoffs and during the early minuets of the flight.
I think it took me less than an hour to think about and then re-plumb the tanks and what else is there to do on a rainy, windy Sunday after noon this time of year here in the UK!
In answer to Londrina It should make virtually no difference to the landings whether you use 2 tanks to the front or 1 at the front and two to the rear?
When the rear tanks are empty or alternatively one of the 2 front tanks is empty the CG shift for both setups is the same as the remaining fuel is in the same place.
What will make a big difference to the landing is the Crow coupled to the the landing flap as this gives you the ability to to come in steeper and slower.
With 50-55mm of flap and 5-6mm of crow you can come in on a 45 deg approach, flare and not build up any speed or balloon, as Gary says its a lovely airframe to land.
If you do "go for Crow" only mix it from the second stage flap, if you mix it for the take off flap also it wont help at all if you want a short takeoff run.
One thing you will notice with the front rear tank setup is the take of runs are are much shorter and it requires less back stick to rotate then less elevater trim to keep the nose up.
Roll on the summer, I'm going Cabin crazy here in the workshop and cant wait for our "two weeks of sunshine" some time between June and August

Regards Mark
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Old 01-28-2013, 05:07 AM
  #382
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Default RE: JET LEGEND VIPER BUILD THREAD

I know the feeling Mark
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Old 01-28-2013, 06:31 AM
  #383
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Default RE: JET LEGEND VIPER BUILD THREAD

Hi All
Reading back a few posts I see some one had a problem feeding the servo wires and airlines through the Vipers wing.
I find by using a small lead weight on the end of a length of string can get around any ribs or formers whether there lined up or not.
Just dangle the weight down the hatch or hole in the tip cut for the lights and let it drop through as you rotate or tip the wing accordingly.
Don't forget to tie the end off or it will just disappear and fall out the other end and you will have to start again!
Once its found its way through,use masking tape to attach the wires or airlines to the string "stream lining" the joint and pull them through "Simples"
Not sure why theres been any problems with the airlines on the Viper, all of mine so far have come pre plumbed up?

Regards Mark
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Old 01-28-2013, 07:51 AM
  #384
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Default RE: JET LEGEND VIPER BUILD THREAD

Thanks guys I got everythign routed, after I put the gear into the wing I realized I was doing it wrong. I only work on this thing a couple hours a week and it is very easy to build. I made it harder by modifying mine for where all the stuff mounts and redid the tank locations. Still easy though! Since I did not buy the fancy valves and used existing gear I made my own mounting boards to accomodate everything and it mounts above the front tank.

One thing about the tank mods, if you are like me and do not have a smoke system, then you get a great advantage if you use the rear tanks for fuel and only ONE front tank. Then your CG will still still move, however you get to take off with the CG on the spot, it moves forward during flight and the most forward will be when the rear tanks are empty, and the one front tank is full. In this configuration the CG is still not as far foward as it would be with two full front tanks! Having such a forward CG on take off is hard on the front gear in grass, and increases take off distance. On my fields, the end of the fields are DEATH so I like to shorten the distance as much as I can. I found holding the brakes and spooling up does not do much on grass so I am doing this. My buddy is getting the turnkey version and his will be stock, we fly the same field so I will be able to report back the differences if any.

If you wanted to, which it would be unecessary, you could hook all the tanks in series, so that one rear tank drains, then the front tank, and finally the last rear tank. Sice the rear tank is so close the CG this would result in little CG shift. But like everyone is saying, its not needed.

If you have a smoke system and always run smoke, you have the best advantage with CG, which I think JL assumed.

I havent flown mine yet but I just know that a nose heavy plane sucks on grass, and I really hope I dont have to trim in flight, that is very rare to have to do and questionable.
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Old 01-28-2013, 08:56 AM
  #385
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Default RE: JET LEGEND VIPER BUILD THREAD

Quote:
ORIGINAL: Chris Pyrah

Hi Christian,
Had a look at your post 210 ,thats exactly how I was thinking of installing a tank ,What tank did you use ,is it a dubro.
what distance is best to mount a merlin 100 from the bellmouth.
Cheers
Chris

All the turbines are about same, somewhere around 1" is the best (25mm). This is the distance from the exhaust cone to the start of the bellmouth.
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Old 01-28-2013, 09:07 AM
  #386
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Default RE: JET LEGEND VIPER BUILD THREAD

That's rubbish, Jetcat and several other manufacturers state 18mm, or 3/4"
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Old 01-28-2013, 09:23 AM
  #387
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Default RE: JET LEGEND VIPER BUILD THREAD

A Merlin 100 needs a distance of 1" or 25mm, NO MORE than that, and definitely not 2" as posted above!

Mine is set at exactly 25mm with the Merlin 100 X, and it works perfectly!
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Old 01-28-2013, 10:12 AM
  #388
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Default RE: JET LEGEND VIPER BUILD THREAD

Sorry it is 1", not 2". Somwhere around 1" is about where they all are from what I have seen, not 2"
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Old 01-29-2013, 01:06 PM
  #389
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Default RE: JET LEGEND VIPER BUILD THREAD

Hi Guys Thanks to all who replied to my questions ,I am eager to finish the install but have to work away Monday to Friday so don't get a lot of time to complete things.We have a good grass strip to fly from (as per Ian Prentices first Video post).But at this time of year it gets wet and is very draggy that's why I am keen to have the nose as light as possible for take off.I will be using Crow, its the best thing since the invention of beer for keeping the jet on the deck on landing.Cheers Chris
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Old 01-30-2013, 03:31 AM
  #390
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Default RE: JET LEGEND VIPER BUILD THREAD

Greetings all, I maidened my viper this past weekend, I'm using a Jet central Rabbit, my CG is 35mm behind the cl of the spar, the turbine is 3/4" from the hot tube, I did make a platform to sit on top of the air inlets for the fuel valves and ecu, the ecu battery and RX batteries are in the nose.

I had to put two clicks of trim in the elev (up) and two clicks of trim to the left (ail), I did get a little left roll with 1st flap input, I didn't have both flaps set the same mm down, old eyes can do that.

All flight surf have been rechecked and set the same.

It is one of the best flying airplanes I have had, I didn't use any flaps on landing, no problem slowing down, we are very lucky to fly on a Navy out line field, 3500' X 300' runway, you can land a bus on it.

I wish everyone the best of luck with your Vipers, I also want to thank the two fellows that did give me some input, (1) placement of the fuel valves, (2) sending me the items needed for the landing lights, the landing lights are used on over cast days...old eyes again.

Thanks All.

Rocky Kranz
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Old 01-30-2013, 04:07 AM
  #391
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Default RE: JET LEGEND VIPER BUILD THREAD

Hello Rocky,

congrats for your successful maiden flight.
Some pics?

Greatings from Germany

Christian
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Old 01-30-2013, 12:27 PM
  #392
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Default RE: JET LEGEND VIPER BUILD THREAD

Congrats Rocky,

You are going to love this jet, gets more enjoyable each flight!
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Old 01-31-2013, 01:25 PM
  #393
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Default RE: JET LEGEND VIPER BUILD THREAD

Thanks and thanks for the information, I will try to get some pictures this coming weekend, weather depending, yes FL. also has it's bad days as well, living on the coast.

Rocky Kranz
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Old 02-01-2013, 01:38 PM
  #394
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Greetings from now sunny FL, does anyone have any info for a pilot that will fit, without having to cut nost of it off, front seat only....Thanks.
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Old 02-01-2013, 08:23 PM
  #395
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Default RE: JET LEGEND VIPER BUILD THREAD

Hey guys, this seem like a very nice every day flying jet. Really like the Vodaphone colour scheme and the blue HPAT scheme.

How will this jet fly with a K 80? I had this in a JT Hawk of the same size/weight, it flew nice and the Viper seems like a cleaner airframe.

Opinions?

Also Jeremy, how can I contact you for a quote?

Matt
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Old 02-01-2013, 08:30 PM
  #396
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Default RE: JET LEGEND VIPER BUILD THREAD

Hi Matt,

K100 would be better but I have seen one fly on a VT80 (18lbs) and it was fine. I'll PM you my details

Cheers

Jeremy
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Old 02-01-2013, 08:35 PM
  #397
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Default RE: JET LEGEND VIPER BUILD THREAD

K80 will fly it fine, I dont think we'd see much difference between a K80 and K100 except on takeoff.

Its a clean airframe but the wings and tail are quite thick. I suspect from that perspective it is quite draggy. I would not expect it to fly like a bandit or flash.

I have not flown mine so I cant really say much else.

I had my K80 in a MB f-86D, similar wing thickness, much thinner tail. It was not fast at all. I would not expect much more speed out of this.

I was shocked at the thickness of the wings, it will help it land nice but I dont really need that. I want speed!
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Old 02-01-2013, 08:36 PM
  #398
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Default RE: JET LEGEND VIPER BUILD THREAD

Yeah it would only be noticeable on takeoff. In the air it doesn't need much to push it around at all. It ia a very clean airframe.
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Old 02-02-2013, 01:28 AM
  #399
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Default RE: JET LEGEND VIPER BUILD THREAD

How do you know a K80 will be fine if you haven't even flown yours yet? Also it is not "draggy"

I can tell you that with a P80SE it is damn quick when it's wound up.
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Old 02-02-2013, 06:41 AM
  #400
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Default RE: JET LEGEND VIPER BUILD THREAD

common sense. and comments others made about p80 lead me to believe it will fly.

The wings and tail ARE draggy. I dont care what you say, anything that thick will cause drag.

Quote:
ORIGINAL: madmodelman

How do you know a K80 will be fine if you haven't even flown yours yet? Also it is not ''draggy''

I can tell you that with a P80SE it is damn quick when it's wound up.
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