Vettster

Plane is for sale. http://rccanucks.com/showthread.php?1433-Xcalibur

Flaps2012

It's been a while since I have posted anything on my Xcalibur build. Here a few pics of what it's shaping up to be. Everything is pretty much installed. She weighs in at 18.4 lbs without fuel. I have not done the CG yet, and I am hoping all the battery capacity that I have in the nose isn't too much. We shall see...lol.

saillplane77

Jeremy, noticed you are not using the GPS with the Xycoy Flight Computer. I assume you are using the one your PowerBox system? Is that working ok for you?

Flaps2012

Actually I do have the Xicoy GPS for the Flight Computer. I just don'y have it installed yet. I'm not so sure what is pictured will be the final home for the FC1. I may mount it on top of the air tanks.

saillplane77

Jeremy, got it. I think I am going to try both GPS in the FC and GPS in my PowerBox. My other jets only did the GPS in my Powerbox but will try both in this airframe. If your nose heavy will be a first for Ripmax I think. I'm going to CG mine in a few days. I have a 5,200 ECU, 5,200 brakes and retracts (electric) and 2 - 2600 mah on the receiver. I doubt if I am going to be nose heavy by my initial trial CG's, but will see. Would rather fly batteries around than lead.

Vettster

So i decided to keep my Blue Angel X from HK

The big problem I was having was it tendency to climb above half throttle. I fixed that soon enough by adding 4* up to the stab. But then(not surprisingly)I noticed that the grass was getting burned in our pit area. Not Good! For Sale!! But I decided to give it one more shot. The Boomer Sprint jets never needed down thrust.. so why should this plane?? I took a chance and I leveled off the engine with the thrust line and took her up. I fully expected the plane to climb to the moon and was praying I had enough down trim to compensate... this was not the case... It actually flew very well. I will add another 1* up(for down effect) to the horizontal stab.. but otherwise, It just doesn't need Down Thrust!!! So why do these so and so designers put it into the design?? There is no chance what so ever of it burning the tail or the thrust pulling the tail into the plume making it climb. I just dont get why they would design a jet that they KNOW will burn the grass and thus hurt sales, when there is no need for it.

Dave Wilshere

So you 'cured' it by adding down elevator!?

Our local site is all grass, 13 std size Xcalibur models, all with down thrust, none climb (more than a touch) none burn the grass.
As always you cannot design a model like this to suit all turbines efflux speeds. But it does need down thrust. Tailplane placement is the controlling factor, if its high enough less is needed.

Vettster

A club that is all grass is not so much a problem if the club likes turbines.. Now when you fly on a SOD field where the owners expect you to NOT damage their lively hood.. Its a hole other ball game.

I cured it by adding 4* Up to the stab. Then I fixed the NOT NEEDED down thrust by adding yet one more degree for a total of 5* UP in the stab and thus reducing the down elevator. Hey!! I didnt design this jet.. Im just making it proper.

Im now working on correcting the canopy for the company

Vettster

I got her out today for 2 more flights. Its now bang on! hands of the sticks at any speed. All I had to do was add 4mm to the front of the stab...who knew(gigantic rolling eyes)

Thats 3mm if you leave the grass burner angle that is not necessary, in the engine.

Or 4mm if you mount the engine straight and level with the thrust line.

Getting back to work on correcting the canopy now

Flaps2012

A few pictures of my Xcalibur on the scales. Getting very close to maiden time!

saillplane77

After trying to keep the weight as far forward as possible I'm nose heavy by 375 grams? I used the smaller servos for the rudder as suggested, and moved my Jet Central Bee II as far forward as possible. Also using 2-2600 mah for the receiver, and 5,200 mah for the retracts and brakes and a 5,200 mah Life 3 cell for the turbine all located up front. I know that's alot of battery but I would rather fly batteries than lead around. I can't believe I'm that nose heavy and wanted to throw out my measurements (see pic) that I'm using. I'm using Electron retracts trailing link and doubt that is throwing off my measurements. I'm also using 160 mm as the CG point (Suggested in the manual) even though most are using 165-170. I know us Americans have troubles with metric but I think I measured this correctly. It was a beautiful day in the mid-west so I was out at the field all day and spent till late tonight putting the airframe on the scale, so a little tired, just can't believe I'm that nose heavy ? If I move the turbine back 30 mm and go with a 2,600 3 cell Life for the turbine and go with a 2,600 Li-Ion for the retracts and brakes I'm still about 100 grams nose heavy? The tank is MT and the UAT full. Any suggestions? How nose heavy can I be?

Grodus

I fly mine with a Wren SS which is almost identical in weight to my Superbee. I don't reckon a Superbee II is much heavier. I mounted the engine as far forward as possible, all 3 batts in the nose compartment as well as the uat. The fuel pump, and solenoid on the forward bulkhead yet still had to fill the end of the nose cone with lead shot and attach a couple of ounces of lead to the underside of the deck in the nose. My rudder servos are less than one ounce. I have one of the earlier kits so maybe something has changed but I could not have possibly have built mine nose heavy, I tried!
You are toting a lot of electricity. I set mine flight control servos up with an amp meter and I use about 125 ma per 10 min flight. Two 1800mah packs for the receivers conservatively will fly it more flight during a day than I can afford. You don't need 5200ma for flight controls? I can't speak for the electric retracts but if they require that kind of mah, can you consider going with smaller packs and changing them out? I fly mine with a 2300 lipo for the ecu and have a charged spare one ($15) if I need to fly more than 10 times. Might be an option? If the Superbee II is kero strart and uses a lot more battery for start, you can make a "Y" for an offboard battery assisted start. I had to do that to get my Bee to start because the supplied 5200ma Li ion wasn't up to the task.

Flaps2012

Mine was nose heavy as well with 2 3000mAh 2S LiFe packs for the Powerbox and a 3000 mAh 3S LiFe for the turbine. It is only nose heavy enough to put the CG at 157mm. I bought a couple of 2000 mAh 2S Lipo's to replace the overkill LiFe packs on the Powerbox.. This should get me alot closer to the reccommended 170mm without having to do major surgery changing component locations, while reducing overall weight as well.

Dave Wilshere

Have you tried the 100% reliable two fingers on marks? does it agree with your gizmo, that I would trust no further than I could throw them...
Servo weights do vary, and for sure there will be a little variation on wood weight on the back end stuff, but I have a P-100Rx in the back a 3400 3s Li-fe ECU and 2 x 2200 2s Rx packs with a Powerbox Sensor switch and no weight.
The variations people see can be down to changing control horns and rods (I use all stock in over 150 flights) The servo weights, even extension lead weights.

Dave

izzy

My favorite jet lately
http://www.youtube.com/watch?v=64m-WQtzTF4

DenisFerrari

My one, Wren 80DCi with exhaust nozzle just 15-20mm out the back, 250gr in front nose cone, 2x1800mAh in front nose cone --> CG at 170mm and it flies just beautifully.

Setting the CG with 2-fingers-method on 170mm marks underside

izzy

Cg at 170mm is perfect in mine too
the k100 is heavier so mounter way forward and using 4200 3s life cells for turbine and 2*2200mah 2s lipo for Rx with powerbox switch

also using electron retracts

dmattmul

Normally I break out the fingers for final checking. Fingers confirmed Xycoy was correct. Will start shifting the engine back and using lighter battery systems. I am building this using a little heavier receiver than normal (PowerBox Royal) as I wanted to duplicate what I'm using in my other jets. It seems possible to build this one tail heavy. The quality of the kit I've been very happy with. Good value for the money.

chrispol

My Feedback: (9)

Finally got my Xcalibur in the air this weekend, two clicks of elevator and everything was great.

8 flights, last one i had a bounce and bent the stock gear.

What I noticed, I need to add throttle to down elevator it would climb under power

The stock travels seem quite low. Doing a reverse half cuban full elevator resulted in a very wide arc

But overall best twin boom jet i ever owned.

EDFCrazy

Add one washer under the front of the engine mount on each side, to make the engine's nozzle point a little down. this is all mine needed to not climb at full throttle. VT 80 in mine.

https://www.youtube.com/watch?v=ctpqZ7q0xSA

chrispol

My Feedback: (9)

VT80 here also

What washer thickness did you use?

saillplane77

I wanted to post the equipment I used and let others know it's possible to not be tail heavy. If anyone sees something unusual I did or used let me know. The receiver and systems are a little over-kill but I wanted to set this jet up the same as my other 4. I want to use this as a training jet to let others fly a turbine at my field and to show that it's not overly complicated to build and fly even with the new telemetry out there. I moved to smaller batteries plus pushed them back as far as possible in the nose of the airframe along with moving my turbine back as far as practical. I think my light turbine was the issue why I was able to build so nose heavy. If I would build again probably would put a JC Rabbit in it. Weights only 1.00 kg and puts out 11 kg of thrust. I am pretty sure I could get it also to balance with no added weight. I think the newer more efficient turbines make this airframe less prone to being tail heavy. Again it's nice value for the money !!

Servos:
HS-5645MG approx. 170oz/in(12.2kg/cm)@6V- 4 total for Ailerons, Elevator, and Flap(Digital Metal Gear)
HS-5245MG approx. 76oz/in(5.5kg/cm)@6V- 2 total for Rudder Pair(Digital Mini Metal Gear)
HS-645MG approx. 133oz/in(9.5kg/cm)@6V- 1 total for nose wheel steering (Analog Metal Gear)
Total weight 0.350 kg (Rudder servos were slightly over an ounce)



Turbine:
Jet Central Bee II - 0.88 kg with starter

Bower Box Royal - 0.260 kg including display and switch

Turbine battery: 3 cell Life 2100 mAH 0.159 kg

Retracts, brakes receiver - 3 2,600 mah Li-Ion (Jeti) - 3* 0.120 = 0.360 kg

Airframe with MT with above (UAT full) 8.95 kg

That puts the airframe at ~ 6.7 kg with a full UAT. Does that appear like the others?

When I tested the CG with a ful tank moved the CG forward 29 mm and total gross weight at 11.48 kg.

There has been discussion on the elevator incidence, I get down horizontal stab 5.5 degrees, Airframe as it sits level down 1 degree measured on the canopy top about 1/3 back from the tail. Turbine downthrust is 6 degrees.

I know this is overkill but I like to find issues on the ground, easier to troubleshoot than in the air. (You should see what I go through with my full scale planes and builds)

saillplane77

"There has been discussion on the elevator incidence, I get down horizontal stab 5.5 degrees, Airframe as it sits level down 1 degree measured on the canopy top about 1/3 back from the tail. Turbine downthrust is 6 degrees."

Meant canopy bottom top of airframe. (Removed the canopy to check incidence)

Vettster

I agree with these numbers 100% Though my engine is zero incidence with relation to the thrust line(bottom of canopy)

EDFCrazy

Just one standard washer like 1mm thick. i didn't think one washer would make such a difference.