Im just finishing one off and was reading the various threads here to see what extra info I could pickup, as usual instructions are light on practical detail and flying experience. Quite understandable. One thing i noticed straight away is the throws in the threads here are quite different from those in the build instructions, quoting another post they are said to be:

Aielrons 1.75" travel total. Put some expo on ailerons for less sensitive.
Elevator 1.75" travel total.
Rudder 2" travel total. Put some expo on rudder for less sensitive.
Flaps : Half flap 3/4". Full flaps 1.5".
Crow ailerons 3/8" up.

but for example the Cermark instructions say flap travel is 2/3 of that here. Hmm, who is right? anyone have stick experience of what works best? and is crow really necessary or flap alone ok? I use flap alone on my Kingcat without any trouble, I know some prefer crow mix. I guess that may be down to taste.

Ive heard alot about flutter problems but that would seem to be an issue with any model if care is not taken. Im not over worried about flutter ive always been a big fan of no slop linkage and no-gap type scale hinging (mass balancing in this moel might be a little tricky so ill skip that fo rnow unless its really necssary). Ill go easy on the throttle just in case...

Any other flight experience or mod experience of the Viperjet 2 would be greatly appreciated?

http://www.rcuniverse.com/forum/m_31..._1/key_/tm.htm

Thx Miguel, i guess Cermark instructions are indeed way off the mark then, by 33%!

Sorry to hear about your model btw, that happens to the best of us from time to time

From the instructions that were given my partner and I set the throws up at max deflection and made that our low rates. Then we added a little more throw (5%- 8%) to the origional throws and made that our high rates.
The plane flew great with the throws that were provided.
We added 12% expo on ele and ail and plane flies great.
With flaps, set up your take off (no down ele. programed needed) and for landing use as much as you can get and don't forget to add a little down ele. when full flaps are on (-8%) seemed to work for us.

good luck plane flies great and we are pushing 60 flights with it so far

THIS IS FOR THE ORIGIONAL VP FIRST GENERATION

Mike

Amjflyer
Use the throws given by Tam, as we know he did extensive testing on this airplane and he is the one responsible for the Viper MK II, a better version.

I'm using them and they work just fine, use crow, it will slow the airplane down to a pleasant speed and use a tad of down elevator too, flaps along will not slow it down enough, I know, truss me.
The MK II will take the abuse just fine, I'm flying the original, the wing spars have the thin joiner and it flew just fine at any speed.

Regarding fluter on the controls, Tam also talks about that on the same or on another thread, the info. is all there.

If you need more info. PM me.

CARS II

My Cermark/Tam manual states that the throws given are for low rate...For example, the elevator is 5/8th's inches up and down for a total of 1 1/4 inches-----Right on for low rates from what I've been told...I'm going to maiden mine in about a week or two..

Kevin

Kevin

I just maidend an MKII Viper this past weekend, my RTF dry weight came in right @ 28lbs using a fully bypassed AMT Pegasus SP. I was a bit nervous of a high wing loading.

I made a stainless c/g hangar that fit on wing spars and sandwich in between wing and fuse and hung it up on recomended c/g point all inclusive and UAT full. My c/g was made to be spot on and lateral balance too.

This thing flies awesome. elevator I use is the 5/8" up/down total 1 1/4" and it lands to full 3 point stall nose wheel high plenty of elevator authority available to touchdown where full deflection is used.

Ailerons 3/4" each direction are HOT HOT, with triple rates it provides nice blend of differant manuvers.

I use 40 digits of spoilerons on JR radio for landing, 50 digits proved to have to much authority and cause a more abrupt 3 point stall.

I use 5/8" flaps for takeoff and landing pattern and it needs some down elevator trim as it balloons up. I use full flap deflection for landings and same elevator trim.

FWIW, my spoilerons are activated in landing flap flight mode set on final, and are curve mixed proportional to throttle position meaning that at 50% throttle they are set to start and go to full 40 digits at low throttle setting.

Stock fuel tanks are not enough fuel for this turbine only allowing for 7 minutes with not much full throttle use, maiden flight was at 9 minutes with mostly 1/2 throttle flying and upon taxi in the turbine shut down as UAT was sucked dry. I've since added a 32oz BVM overflow in front bay area.

I've flown over 40 gallons on a Pegasus powered Kingcat and routinely fly at our 500' club field but this Viper uses less throttle to fly landing pattern and should easily be at home on our 500' home field. I hope to burns allot of kero at this weeks Kentucky Jets.

I'm glad almost everyone got this plane fly successfull.
Make sure to use correct servos.
I recomending JR DS 3421 metal gear for elevators. Hook up the linkage rod about 3/8" from the center of the servo arm. This isvery important for mechanical advantage. Most flutter incident happen was done too far out from the center of the servo arm.
Crow set up is the way to land the viper jet. Flaps along will not enough to slow down for landing.
3/8" crow. Full flaps. No need to trim elevator if set up the flaps servos to travel slow to deploy the flaps.

Before landing. Slow down the speed. Put out gear first. After it slow enough. Put down flaps and crow. Add little throtle to kept the airplane fly nose high. Not to worry about stalling. With the crow set up. It won't tip stall. Use your throtle to control the decent.
If you got use to it. The Viper Jet can craw in for landing.
Have fun with Viper Jet.
I can't wait to EDF version flying soon.

Congrats on your maiden c/f, and thx for the additional supporting info Tam.

Out of interest I had HiTec 5245MG servos available (left over from an F3J glider that they wouldnt fit in!) so i used these instead of the JR DS3421. However the specs are almost identical, they are very similar servos (I even wonder if underneath the case they are perhaps identical). Although given a choice I would generally feel more comfrotable with JR/Futaba servos in high performance models Ive found these HiTec digitals to be pretty good. Im using heavy ball links in the linkage for zero slop and will hookup as you say.

Incidentally the servo actually ius slightly wider at the back (like by 1-2mm!) than the servo bay can provide. This means the cover sits slightly proud of the stab halve. I was just going to modify the cover to fit this way anyone else had to overcome a similar problem. The alternative would be to use JR DS161 servos but im just not comfrotable that these would be man enough for the job.

Ohhh, incidentally Tam or anyone, do you notice much loss of aileron (roll) authority when using crow? Often this is the case (with other models i have with crow e.g. KingCat) which can make landing pattern a little bit soft and stodgy.

Hitec 5245MG is O.K. I have flow with that servo and lock in over 100 of flights. But I do experience few of those servo are bad out of the box.
So I go with JR DS 3421. It cost little more. But more reliable.
As the cover. Yes it bigger by 1-2mm on the back of the cover. Shim the cover on the back to raise to clear the servo.
Do not use Jr DS168 on the elevators. It don't have enough power to hold the elevator.

Good luck.

It got plenty of ailerons control for landing.
I never have any issue.

I maidened my Viperjet today and it flies well but I had elevator and aileron sensitivity issues as both were waaaaaay too hot around neutral even with plenty of expo---I think that I may need more nose weight to cure the pitch problem...


Guy's---Please post how much expo and total throw you have on the ailerons and elevators for all three rate settings on your 10X...

THANKS!!

Kevin

Is your Viper balancing on the rear of the recommended CoG? If it is then that could certianly be the problem. Otherwise its simply too much rates and needs dropping down a hole or two on the servo arm.

On the note of balancing the Viper. Mine has come out profoundly tail heavy. With all gear in and 2lbs of old fashioned batteries in the nose I am still going to need to add lead, about 1lb I think. Anyone else had it come out this far out?

Yep---I added at least a pound to mine---I'm going to add more it looks like....Yes, my C/G is at the rear of the recomended C/G....Mine was so tail heavy it sat on it's tail when I first put it all together. I'm running all large nicads in mine and still had to add weight even though I was carefull about not adding weight to the tail...However, I did static balance the rudder due to all of the rudder flutter problems previously mentioned in other threads...I never opened her up today on the maiden and kept her at 1/2 throttle the entire time as she was a handfull due to pitch sensitivity...

Kevin

i put my ecu and both rec packs in the nose
and put 2 detailed pilots in the cockpit and
6 oz of lead up front to not be tail heavy
vinny

Vinny---What are your control throws and expo #'s????


Kevin

kevin
i am using -10 persent expo on elev and aileron
this is with hitec 5945 on all contol surface if the servos
you are using are faster use a little more expo
set up per tams viper book just the flaps i put as much
as i can get for landing flaps take off it is set as plans
vinny

Wow thats a tiny amount of expo. If I use it at all i set usually about 60% on ailerons, 40% on elevator and 60% on rudder (if its a strong rudder, 40% if not) as a starting point. With 3D prop jobs i even run 80% or more expo on hi rates.

Expo is also about servo arm to horn geometry. I am 5/8" out on arm and 1" off of hinge line. This allows for 80% ATV for the 5/8" elevator throw in either direction, roughly. I did not use the stock horn and used BVM c/f ones. I only use 25 digits of expo and that is for control stick interaction. I'm also a 3D flier and generally never like to use over 50 digts. In some of my non jets foamies stuff, I've actualy preffer to use servo speed instead of high expo. Servos get kind of flaky IMHO using 80% digits of expo.

I am confident that some jets get a bad rap from c/g problems, ( I learned on a KAngaroo and NOT once KANGA ROOEd it, still in pristine condition, I have KANGA rooed the KingCat prior to spoilerons) I did not add one ounce of weight to my Viper, However I did use GP3300 NMH for ECU pack. I also had to create my own custom C/F mounting of all the goodies. The fuel pump is in the point of the nose with all 3 battery packs as well. Basically from the tip of the nose (which I made removable) to 15" back is all the goodies minus control servos. heres the list:

Pump
(2) 1400 Ncd
(1) 3300 NMh
ECU
AMT ASU plug
AMT ECU
Jr 10X RX
Powerbox
BVM soft brake and Hitec MG85 servo
Robart Retract valve and Hitec MG 85 servo
JR DS 3421 nose wheel steering.

As for control servos I used the DS3421 on all surfaces, with JR 4721 on flaps.

I used Tamjets thin profile composite servo mounts glued to skins (not hatches) then I boxed them in to opposite side skins with c/f. this way they are locked in to both side skins. My rudder does not have any special considerations other than this mounting style, as it is a MKII kit.

Having burned 7 gallons of kero at Kentucky Jets this past weekend I am extremely pleased with this model and actually like flying it more than the Kingcat for now as the KC never came out of the trailer. The totally enclosed bypass is really putting out the thrust on the pegasus SP.

I encourage all to make some c/g plates out of 1/4" plywood sandwiched between wings. drill two large holes to pickup the spars, then about 2" above wing you drill a small hole that represents c/g position, then string it up in the air by the c/g hole in plates. I wish ALL manufactures could laser cut these c/g lifting plates and supply in kits, they would get far less abuse for the cost of the plywood. these heavy jets theres just no other way IMHO.

PS if someone would like to borrow my Stainless ones, I'd be happy to send them your way.

I will be getting the Eagle tree back this week so we'll see what it's got.

c/f, with this weight issue i was also considering installing a powerbox + extra rx pack. At present it just has a 5 cell pack and 6 cell ecu pack and Jacco regulator (as this setup + the P120 has come fromt the Hotspot i just sold). Although I was wondering where the hell I was going to put it, could you post a photo of your install? Id be grateful, thx. Nose cone of the Mk11 is already removeable via two bolts in through the front. In general agree with your expo comment as well. I dont run any jet with more than 60% expo, and my Kingcat has none.

AM,

Your right the nose is removable with internal screw arrangement, I needed the room so the front nose bulkhead of the fuse was opened up to within 1/4" of the edges and the nose cone plywood former was removed. I use 4 #2 small black button head wood screws externally to mount nose and since their black and placed in the black pinstriping paint there mostly invisible and easier to remove.

I also made a c/f frame to secure removable canopy too and did not use any off the Original fiberglass seat/cockpit stuff. That stuff weighed 15 ounces.

Here are some pix from inside, I will get front shot later today.

Nice work in there, its quite tight for room, thx for posting. You are right i nearly fell over when i picked up the cockpit parts etc, they weigh more than some of my lightweight gliders! Though at the moment i can use that weight to advantage. I think if i want to include a powerbox id have to start again on the install unless i go for the Basic version and just have a redundant pack. Ill probably fly it for a while with removable lead then decide. Ill give it some thought....

more photos of interest:








My solution for tight wing connections, the braid acts as a snake to feed along side of tanks and everything rests and plugs in on top of bypass.

What did you do with your farings? I can see they arent glued to the wings as per instructions. Mine are being a bit of a nightmare. They are on the wings but the fit to the fuse is poor so i thing i will have to add more glass to the fairings to belnd them in.